Revision of December 2000 Regulatory Finding on the Emissions of Hazardous Air Pollutants From Electric Utility Steam Generating Units and the Removal of Coal- and Oil-Fired Electric Utility Steam Generating Units From the Section 112(c) List, 15994-16035 [05-6037]
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15994
Federal Register / Vol. 70, No. 59 / Tuesday, March 29, 2005 / Rules and Regulations
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 63
[OAR–2002–0056; FRL–7887–7]
RIN 2060–AM96
Revision of December 2000 Regulatory
Finding on the Emissions of
Hazardous Air Pollutants From Electric
Utility Steam Generating Units and the
Removal of Coal- and Oil-Fired Electric
Utility Steam Generating Units From
the Section 112(c) List
Environmental Protection
Agency (EPA).
ACTION: Final rule.
AGENCY:
SUMMARY: The EPA is revising the
regulatory finding that it issued in
December 2000 pursuant to section
112(n)(1)(A) of the Clean Air Act (CAA),
and based on that revision, removing
coal- and oil-fired electric utility steam
generating units (‘‘coal- and oil-fired
Utility Units’’) from the CAA section
112(c) source category list. Section
112(n)(1)(A) of the CAA is the threshold
statutory provision underlying today’s
action. That provision requires EPA to
conduct a study to examine the hazards
to public health that are reasonably
anticipated to occur as the result of
hazardous air pollutant (HAP) emissions
from Utility Units after imposition of
the requirements of the CAA. The
provision also provides that EPA shall
regulate Utility Units under section 112,
but only if the Administrator determines
that such regulation is both
‘‘appropriate’’ and ‘‘necessary’’
considering, among other things, the
results of the study. EPA completed the
study in 1998 (the Utility Study), and in
December 2000 found that it was
‘‘appropriate and necessary’’ to regulate
coal- and oil-fired Utility Units under
CAA section 112. That December 2000
finding focused primarily on mercury
(Hg) emissions from coal-fired Utility
Units. In light of the finding, EPA in
December 2000 announced its decision
to list coal- and oil-fired Utility Units on
the section 112(c) list of regulated
source categories. In January 2004, EPA
proposed revising the December 2000
appropriate and necessary finding and,
based on that revision, removing coaland oil-fired Utility Units from the
section 112(c) list.
By this action, we are revising the
December 2000 appropriate and
necessary finding and concluding that it
is neither appropriate nor necessary to
regulate coal- and oil-fired Utility Units
under section 112. We are taking this
action because we now believe that the
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December 2000 finding lacked
foundation and because recent
information demonstrates that it is not
appropriate or necessary to regulate
coal- and oil-fired Utility Units under
section 112. Based solely on the revised
finding, we are removing coal- and oilfired Utility Units from the section
112(c) list. The reasons supporting this
action are described in detail below.
Other actions related to this final rule
include the recent promulgation of the
final Clean Air Interstate Rule (CAIR)
and the final Clean Air Mercury Rule
(CAMR).
DATES: Effective Date: The effective date
of the final rule is March 29, 2005.
ADDRESSES: EPA has established a
docket for this action under Docket ID
No. OAR–2002–0056. All documents in
the docket are listed in the EDOCKET
index at https://www.epa.gov/edocket.
Although listed in the index, some
information is not publicly available,
i.e., Confidential Business Information
(CBI) or other information whose
disclosure is restricted by statute.
Certain other material, such as
copyrighted material, is not placed on
the Internet and will be publicly
available only in hard copy form.
Publicly available docket materials are
available either electronically in
EDOCKET or in hard copy at the EPA
Docket Center (EPA/DC), EPA West
Building, Room B102, 1301 Constitution
Ave., NW., Washington, DC. The Public
Reading Room is open from 8:30 a.m. to
4:30 p.m., Monday through Friday,
excluding legal holidays. The telephone
number for the Public Reading Room is
(202) 566–1744, and the telephone
number for the EPA Docket Center is
(202) 566–1742.
FOR FURTHER INFORMATION CONTACT: Ms.
Wendy Blake, OGC Attorney, Office of
General Counsel, Environmental
Protection Agency, (AR–2344),
Washington, DC 20460 telephone
number: (202) 564–1821; fax number:
(202) 564–5603; e-mail address:
blake.wendy@epa.gov.
Judicial Review. Pursuant to CAA
section 307(b), judicial review of this
final rule is available only by filing a
petition for review in the United States
Court of Appeals for the District of
Columbia Circuit by May 31, 2005. EPA
designates this action a CAA section
307(d) rulemaking. (See CAA section
307(d)(1)(V); 69 FR 4653 (January 30,
2004).) Under CAA section 307(d)(7)(B),
only an objection to the rule that was
raised with reasonable specificity
during the time period for public
comment can be raised during judicial
review. Section 307(d)(7)(B) further
provides that if the person raising the
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objection can demonstrate to the
Administrator that it was impracticable
to raise the objection during the public
comment period or if the grounds for
the objection arose after the public
comment period but within the time
period specified for judicial review and
if the objection is of central relevance,
EPA will convene a proceeding for
reconsideration of the rule and provide
the same procedural rights as would
have been afforded had the information
been available at the time the rule was
proposed.
I. Statutory Background
In the 1990 Amendments to the CAA,
Congress substantially modified CAA
section 112, the provision of the CAA
addressing HAP. Among other things,
section 112 contains a list of ‘‘hazardous
air pollutants,’’ which are ‘‘pollutants
which present, or may present, * * * a
threat of adverse human health effects
* * * or adverse environmental effects
whether through ambient
concentrations, bioaccumulation,
deposition, or otherwise.’’ (See CAA
section 112(b)(2).) In the 1990
amendments to the CAA, Congress
listed 190 HAP, and authorized EPA to
add or remove pollutants from the list.1
(See CAA Section 112(b)(1)–(b)(3).)
The types of sources addressed under
section 112 include: major sources, area
sources, and electric utility steam
generating units (Utility Units). (See
CAA 112(a)(1), (a)(2), (a)(8).) A ‘‘major
source’’ is any stationary source 2 or
group of stationary sources at a single
location and under common control that
emits or has the potential to emit ten
tons or more per year of any HAP or 25
tons or more per year of any
combination of HAP. (See CAA
112(a)(1).) A stationary source of HAP
that is not a ‘‘major source’’ is an ‘‘area
source.’’ (See CAA 112(a)(2).) Finally,
an electric utility steam generating unit
is any ‘‘fossil fuel fired combustion unit
of more than 25 megawatts that serves
a generator that produces electricity for
sale.’’ (See CAA 112(a)(8).)
There are two important steps under
section 112: (1) Determining whether a
source category meets the statutory
criteria for regulation under section 112;
and (2) promulgating emission
standards for those source categories
regulated under section 112. In terms of
the first step, Congress required EPA to
publish a list of categories and
1 The current section 112(b) list includes 188
HAP.
2 A ‘‘stationary source’’ of hazardous air
pollutants is any building, structure, facility or
installation that emits or may emit any air
pollutant. (See CAA Section 111(a)(3) and
112(a)(3).)
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subcategories of major sources and area
sources by November 15, 1991.3 (See
CAA 112(c)(1) & (c)(3).) Congress further
directed EPA to revise this initial list
periodically, based on, for example, new
information. (See 112(c)(1).) EPA is
required to list a category of major
sources under section 112(c)(1) if at
least one stationary source in the
category meets the definition of a major
source—i.e., if a certain amount of a
HAP (or combination of HAP) is emitted
from the source. (See 112(a)(1).) By
contrast, EPA is required to list
categories or subcategories of area
sources only if they meet one of the
following statutory criteria: (1) EPA
determines that the category of area
sources presents a threat of adverse
effects to human health or the
environment that warrants regulation
under CAA section 112; or (2) the
category of area sources falls within the
purview of CAA section 112(k)(3)(B)
(the Urban Area Source Strategy). (See
CAA 112(c)(3).)
For those source categories regulated
under section 112, the next step
concerns the establishment of emission
standards. Under section 112(d), EPA
must establish emission standards that
‘‘require the maximum degree of
reduction in emissions of the hazardous
air pollutants subject to this section’’
that the Administrator determines is
achievable based on technology, taking
into account certain factors such as cost,
energy requirements, and other impacts.
The emission standard for new sources
cannot be, however, less stringent than
the level of control achieved by the best
controlled similar source, and the
emission standard for existing sources
cannot be less stringent than the average
emission limitation achieved by the best
performing 12 percent of existing
sources in the category, regardless of
cost, energy requirements and other
impacts. CAA 112(d)(2) and (3). Finally,
within eight years after promulgation of
section 112(d) emission standards for a
listed source category, EPA must
promulgate additional standards if such
standards are necessary to provide an
ample margin of safety to protect public
health or to prevent an adverse
environmental effect. (See CAA section
112(f).) These additional standards
under CAA section 112(f) are commonly
referred to as ‘‘residual risk’’ standards.
3 EPA published the initial list on July 16, 1992.
See 57 FR 31,576, July 16, 1992. EPA did not
include Utility Units on the initial section 112(c)
list because Congress required EPA to conduct and
consider the results of the study required by section
112(n)(1)(A) before regulating these units and,
therefore, listing in 1992 was not authorized by
statute.
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The criteria for listing major and area
sources established in section 112(c)(1)
and (c)(3) do not apply to Utility Units
because Congress treated Utility Units
differently from other major and area
sources. Indeed, Congress enacted a
special provision for Utility Units in
section 112(n)(1)(A), which governs
whether Utility Units should even be
regulated under section 112.4 Section
112(n)(1)(A) directs EPA to conduct a
study to evaluate what ‘‘hazards to
public health [are] reasonably
anticipated to occur’’ as the result of
HAP emissions from Utility Units ‘‘after
imposition of the requirements of th[e]
Act,’’ (emphasis added) and to report
the results of such study to Congress by
November 15, 1993. Congress also
directed EPA to describe in the report to
Congress ‘‘alternative control strategies
for [those] emissions that may warrant
regulation under this section.’’ (See
CAA section 112(n)(1)(A).) Section
112(n)(1)(A) further provides that EPA
shall regulate Utility Units under
section 112 if the Administrator
determines, considering the results of
the study, that such regulation is
‘‘appropriate and necessary.’’ Thus,
unlike other major and area sources,
Congress first required EPA to examine
how ‘‘imposition of the requirements of
th[e] Act’’ would affect the overall level
of utility HAP emissions, and then
determine whether regulation of Utility
Units under section 112 is both
appropriate and necessary. Section
112(n)(1)(A) therefore sets an important
and unique condition precedent for
regulating Utility Units under section
112 and provides EPA discretion in
determining whether that condition
precedent has been met.
II. Regulatory Background
A. EPA’s December 20, 2000 Regulatory
Finding
On December 20, 2000, EPA issued a
finding pursuant to CAA section
112(n)(1)(A) that it was appropriate and
necessary to regulate coal- and oil-fired
Utility Units under section 112. In
making that finding, EPA considered the
Utility Study, which was completed and
submitted to Congress in February 1998.
In the Utility Study, we divided
Utility Units into three subcategories
based on fuel type: coal-, oil-, and gas4 No one would dispute that certain Utility Units
would meet the definition of a ‘‘major source’’
based on the quantity of HAP emitted from such
units, or that other Utility Units may meet the ‘‘area
source’’ criteria for listing under section 112(c)(3),
but Congress recognized this fact in 1990 and
specifically enacted section 112(n)(1)(A), which
establishes an entirely different test for determining
whether Utility Units should be regulated under
section 112.
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fired units. We then analyzed HAP
emissions from each subcategory. We
followed this approach because each
subcategory burns a different fuel,
which, in turn, leads to different
emissions profiles, which can require
different emission controls. This
approach is also consistent with EPA’s
historical practice of subcategorizing
Utility Units based on fuel type. (See,
e.g., 40 CFR 60.44(a).)
Because EPA subcategorized Utility
Units for purposes of the Utility Study,
EPA, in December 2000, made separate
‘‘appropriate and necessary’’ findings
under section 112(n)(1)(A) for gas-fired,
coal-fired, and oil-fired Utility Units. In
making these findings, EPA considered
the Utility Study and certain additional
information obtained after completion
of the Utility Study, including the
National Academy of Sciences’ report
concerning the health effects of
methylmercury and actual emissions
data obtained in response to an
information collection request EPA
issued to all coal-fired Utility Units in
1999. See 65 FR 79826. EPA reasonably
relied on this additional information
because the information provided a
more comprehensive and
contemporaneous record concerning Hg
emissions from coal-fired units. Nothing
in section 112(n)(1)(A) suggests that
Congress sought to preclude EPA from
considering more current information in
making the appropriate and necessary
finding.
In the December 2000 finding, EPA
determined that it was appropriate and
necessary to regulate coal- and oil-fired
units, but not gas-fired units.5 With
respect to the latter, EPA found that
regulation of HAP emissions from
natural gas-fired Utility Units ‘‘is not
appropriate or necessary because the
impacts due to HAP emissions from
such units are negligible based on the
results of the study documented in the
utility RTC.’’ (Emphasis added) See 65
FR 79831.
EPA provided three primary reasons
in support of its finding that it was
‘‘appropriate’’ to regulate coal- and oilfired Utility Units under section 112.
First, EPA found that it was appropriate
to regulate HAP emissions from coaland oil-fired Utility Units because
Utility Units ‘‘are the largest domestic
source of Hg emissions.’’ See 65 FR
79830. EPA next found that it was
5 Although the December 2000 finding addressed
three subcategories of Utility Units—coal-, oil-, and
gas-fired units, the majority of the finding
concerned Hg emissions from coal-fired power
plants. 65 FR 79826–29 (explaining that Hg from
coal-fired units is the HAP of greatest concern);
Utility Study, ES–27 (‘‘mercury from coal-fired
utilities is the HAP of greatest potential concern.’’).
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appropriate to regulate coal- and oilfired Utility Units because ‘‘mercury in
the environment presents significant
hazards to public health and the
environment.’’ 6 See 65 FR
79830. Finally, EPA explained that it
was appropriate to regulate HAP
emissions from coal- and oil-fired units
because it had identified certain control
options that, it anticipated, would
effectively reduce HAP from such units.
In discussing the appropriate finding,
EPA also noted that uncertainties
remained concerning the extent of the
public health impact from HAP
emissions from oil-fired units. Thus,
EPA’s determination that it was
‘‘appropriate’’ to regulate coal- and oilfired units under section 112 hinged on
the health effects associated with Hg
emissions from coal-fired Utility Units,
the uncertainties associated with the
health effects of HAP from oil-fired
Utility Units, and EPA’s belief that
control options would be available to
reduce certain utility HAP emissions.7
Once EPA determined that it was
‘‘appropriate’’ to regulate coal- and oilfired Utility Units under section 112 of
the CAA, EPA next concluded that it
was also ‘‘necessary’’ to regulate HAP
emissions from such units under section
112. Interpreting the term ‘‘necessary’’
in section 112(n)(1)(A), EPA found that
it was necessary to regulate HAP from
coal- and oil-fired Utility Units
‘‘because the implementation of other
requirements under the CAA will not
adequately address the serious public
6 Section IV below addresses our conclusion that
it is not appropriate and necessary to regulate coaland oil-fired Utility Units under section 112 and
explains why we now believe that our December
2000 finding lacked foundation. As explained
below, one of the reasons the December 2000
‘‘appropriate’’ finding for oil-fired Utility Units
lacks foundation is because the record that was
before the Agency in December 2000 establishes
that Hg is a HAP of concern only as emitted from
coal-fired units, not oil-fired units. Utility Study
ES–5,13,27. EPA therefore should not have relied
upon Hg emissions as a basis for finding it was
appropriate to regulate oil-fired units under section
112. (See, e.g., Utility Study ES–5, ES–27.)
7 The ‘‘appropriate’’ finding for oil-fired units
stemmed primarily from EPA’s concerns over the
potential health effects of nickel from such units.
As explained in the January 2004 proposed rule, the
record before the Agency in December 2000
supported a distinction between nickel and the
other HAP emitted from oil-fired units. See 69 FR
4688. We proposed that this distinction was
reasonable based on the relative amount of nickel
emitted from oil-fired units and the health effects
associated with such emissions. (See also Utility
Study at ES–12 (noting higher population
concentrations surrounding oil-fired units). At the
time of the proposed rule, we recognized, however,
the uncertainties in the data underlying our
‘‘appropriate’’ finding for oil-fired units based on
nickel emissions, and for that reason solicited
information as to whether nickel emissions from
oil-fired plants currently pose a hazard to public
health.
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health and environmental hazards
arising from such emissions identified
in the Utility RTC.’’ See 65 FR 79830.
In light of the positive appropriate
and necessary determination, EPA in
December 2000 listed coal- and oil-fired
Utility Units on the section 112(c)
source category list. See 65 FR 79831
(our finding that it is appropriate and
necessary to regulate coal- and oil-fired
Utility Units under section 112 ‘‘adds
these units to the list of source
categories under section 112(c).’’).
Relying on CAA section 112(e)(4), EPA
explained in its December 2000 finding
that neither the appropriate and
necessary finding under section
112(n)(1)(A), nor the associated listing
were subject to judicial review at that
time. EPA did not add natural-gas fired
units to the section 112(c) list in
December 2000 because it did not make
a positive appropriate and necessary
finding for such units.
B. Litigation Challenging December
2000 Regulatory Finding
Shortly after issuance of the December
2000 Finding, an industry group
challenged the December 2000 finding
in the United States Court of Appeals
for the District of Columbia Circuit (DC
Circuit). UARG v. EPA, 2001 WL
936363, No. 01–1074 (DC Cir. July 26,
2001). EPA moved to dismiss the
lawsuit on the basis of section 112(e)(4),
which provides, in pertinent part, that
‘‘no action of the Administrator * * *
listing a source category or subcategory
under subsection (c) of this section shall
be a final agency action subject to
judicial review, except that any such
action may be reviewed under such
section 7607 of this title when the
Administrator issues emission standards
for such pollutant or category.’’
(Emphasis added.) (See CAA Section
112(e)(4).)
In its motion to dismiss the petition,
EPA argued to the DC Circuit, among
other things, that the December 2000
listing of coal- and oil-fired Utility Units
was inseparable from the appropriate
and necessary finding and that the
appropriate and necessary finding and
listing actions are not final agency
actions pursuant to section 112(e)(4).
See also 65 FR 79826. EPA further noted
in its motion to dismiss that both the
finding and the listing would be subject
to additional notice and comment as
part of the section 112(d) rulemaking.
See EPA’s Motion to Dismiss, UARG v.
EPA, 2001 WL 936363, No. 01–1074S
(‘‘Because the decision to add coal and
oil fired electric utility steam generating
units to the source category list is not
yet final agency action, it will be among
the matters subject to further comment
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in the subsequent [standards]
rulemaking.’’); 65 FR 79831 (noting that
issues related to the listing, such as ‘‘the
exact dimension of the source category,’’
will be subject to additional comment in
the emission standard rulemaking
process). The DC Circuit dismissed the
challenge to the December 2000 finding
for lack of jurisdiction based on section
112(e)(4) of the CAA. The December
2000 finding and associated listing are
therefore not final agency actions.
C. January 30, 2004 Proposed Rule and
March 2004 Supplemental Notice
On January 30, 2004, EPA published
in the Federal Register a proposed rule
entitled ‘‘Proposed National Emissions
Standards for Hazardous Air Pollutants;
and, in the Alternative, Proposed
Standards of Performance for New and
Existing Stationary Sources: Electric
Utility Steam Generating Units.’’ (See 69
FR 4652 (January 30, 2004).) In that rule,
EPA proposed three alternative
regulatory approaches. First, EPA
proposed to retain the December 2000
Finding and associated listing of coaland oil-fired Utility Units and to issue
under section 112(d) maximum
achievable control technology-based
(MACT) emission standards for both
subcategories. Second, EPA
alternatively proposed revising the
Agency’s December 2000 Finding,
removing coal and oil-fired Utility Units
from the section 112(c) list,8 and issuing
final standards of performance under
CAA section 111 for new and existing
coal-fired units that emit Hg and new
and existing oil-fired units that emit
nickel. Finally, as a third alternative,
EPA proposed retaining the December
2000 finding, removing coal and oilfired Utility Units from the section
112(c) list, and regulating Hg emissions
from Utility Units under CAA section
112(n)(1)(A).
Shortly thereafter, on March 16, 2004,
EPA published in the Federal Register
a supplemental notice of proposed
rulemaking entitled ‘‘Supplemental
Notice of Proposed National Emission
Standards for Hazardous Air Pollutants;
and, in the Alternative, Proposed
Standards of Performance for New and
Existing Stationary Sources: Electric
Utility Steam Generating Units.’’ See 69
FR 13298 (March 16, 2004). In that
8 We did not propose revising the December 2000
finding for gas-fired Utility Units because EPA
continues to believe that regulation of such units
under section 112 is not appropriate and necessary.
We have not received any information that would
cause us to change our conclusion in this regard.
In fact, the information that we have received since
the Utility Study only confirms the conclusion we
reached in December 2000. We therefore take no
action today with regard to the December 2000
finding for gas-fired Utility Units.
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notice, EPA proposed certain additional
regulatory text, which largely governed
the proposed section 111 standards of
performance for Hg, which included a
cap-and-trade program. The
supplemental notice also proposed state
plan approvability criteria and a model
cap-and-trade rule for Hg emissions
from coal-fired Utility Units. The
Agency received thousands of
comments on the proposed rule and
supplemental notice.9 Comments
relating to the central issues concerning
today’s action are addressed in this
preamble. The remainder of our
responses are contained in the response
to comments document which is in the
docket.10
D. The December 2004 Notice of Data
Availability
On December 1, 2004, EPA published
in the Federal Register a notice of data
availability entitled ‘‘Proposed National
Emission Standards for Hazardous Air
Pollutants; and, in the Alternative,
Proposed Standards of Performance for
New and Existing Stationary Sources,
Electric Utility Steam Generating Units:
Notice of Data Availability.’’ See 69 FR
69864 (December 1, 2004). EPA issued
this notice to seek additional
information and input concerning: (1)
Certain Hg data and information that the
Agency received in response to the
proposed rule and supplemental notice,
(2) the different forms of Hg that are
emitted into the atmosphere from coalfired Utility Units and how those forms
respond to different control
technologies; and (3) a revised proposed
benefits methodology for assessing the
benefits of Hg regulation. The benefits
methodology generally involves
analyzing Hg emissions from coal-fired
Utility Units, conducting deposition
modeling based on the identified Hg
emissions, and relating that deposition
modeling to methylmercury
concentrations in fish. EPA conducts
benefits analyses for rulemakings
consistent with the provisions of
Executive Order 12866.
9 We initially estimated that we had over 680,000
submissions from the public on the proposed rule
and the supplemental notice, which came primarily
in the form of letters and e-mails. A recent review
of the electronic docket reveals that our initial
estimate was over-stated. The docket reflects
approximately 500,000 separate submissions from
the public, about 5,000 of which represent unique
comments.
10 The response to comments document relevant
to this rule is called: ‘‘Response to Significant
Public Comments Concerning the Proposed
Revision of the December 2000 Appropriate and
Necessary Finding and Proposed Removal of Utility
Units From the Section 112(c) List.’’
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III. EPA’s Interpretation of CAA Section
112(n)(1)(A)
As explained above, Congress treated
Utility Units differently from other
major and area sources and provided
EPA considerable discretion in
evaluating whether to regulate Utility
Units under section 112. Section
112(n)(1)(A) provides, in full:
The Administrator shall perform a study of
the hazards to public health reasonably
anticipated to occur as a result of emissions
by electric utility steam generating units of
pollutants listed under subsection (b) of this
section after imposition of the requirements
of this Act. The Administrator shall report
the results of this study to the Congress
within 3 years after the date of the enactment
of the Clean Air Act Amendments of 1990.
The Administrator shall develop and
describe in the Administrator’s report to
Congress alternative control strategies for
emissions which may warrant regulation
under this section. The Administrator shall
regulate electric utility steam generating
units under this section, if the Administrator
finds such regulation is appropriate and
necessary after considering the results of the
study required by this subparagraph.
(Emphasis added.).
The italicized terms in the above
paragraph are central terms in section
112(n)(1)(A). Before we address our
interpretation of these terms, however,
we again summarize the requirements of
section 112(n)(1)(A). The first step
under section 112(n)(1)(A), which is
addressed by the first three sentences of
section 112(n)(1)(A), concerns the
completion of a study and submission of
the results of that study to Congress by
November 15, 1993. The study is to
examine the hazards to public health
from utility HAP emissions that are
reasonably anticipated to occur
following imposition of the
requirements of the CAA and to identify
alternative control strategies for those
HAP that may warrant regulation under
section 112. The second step, which is
addressed by the last sentence of section
112(n)(1)(A), requires EPA to determine
whether regulation of Utility Units
under section 112 is appropriate and
necessary considering, among other
things, the results of the study. Congress
provided no deadline by which this
determination must be made.
Section 112(n)(1)(A) itself contains no
clear standard to govern EPA’s analysis
and determination of whether it is
‘‘appropriate and necessary’’ to regulate
utilities under section 112. The first
sentence of the subparagraph describes
the scope of the study EPA was to
conduct. The sentence on EPA’s
‘‘appropriate and necessary’’ finding
then says that the Agency must make
that finding after considering the results
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15997
of the study. But Congress did not
supply an actual definition or test for
determining whether regulation of
utilities under section 112 is
‘‘appropriate and necessary.’’ Thus, EPA
must supply a reasonable interpretation
of those terms to fill the gap. Chevron
USA Inc. v. NRDC, 467 U.S. 837 (1984).
Congress’ direction on the study
provides the only guidance in section
112(n)(1)(A) about the substance of
EPA’s inquiry. Because the statute
provides no other explicit guidance,
EPA has chosen to extrapolate from
Congress’ description of the study to
adopt a reasonable interpretation of the
phrase ‘‘appropriate and necessary.’’
The following sections describe how the
Agency has used Congress’ guidance on
the study to formulate different aspects
of our interpretation and application of
the ‘‘appropriate and necessary’’ test.
A. Hazards to Public Health Reasonably
Anticipated To Occur
In section 112(n)(1)(A), Congress
directed EPA to perform a study of
‘‘hazards to public health’’ that would
likely result from utility HAP emissions,
before making any further decisions
about regulating utilities under section
112. Unlike other sections of the CAA,
section 112(n)(1)(A) focuses only on
hazards to public health. It does not
require that EPA study other factors,
such as environmental effects without
any established pathways to human
health effects. In contrast, section
112(n)(1)(B) requires a separate EPA
study, although not as a precursor to a
regulatory determination, of the ‘‘health
and environmental effects’’ of ‘‘mercury
emissions’’ from a broad range of
sources. Also unlike Section
112(n)(1)(A), many of the other
requirements of section 112 explicitly
require both an assessment of human
health effects and, in addition, an
assessment of adverse environmental
effects. For example, the Administrator
is charged with periodically reviewing
the list of Hazardous Air Pollutants and
adding pollutants that present a threat
of either ‘‘adverse human health effects’’
or ‘‘adverse environmental effects.’’
CAA Section 112(b)(2). The
Administrator examines area sources of
HAPs to determine if they present ‘‘a
threat of adverse effects to human health
or the environment.’’ CAA Section
112(c)(3). The Administrator is to
prioritize action under section 112(d)
after considering ‘‘the known or
anticipated adverse effects of such
pollutants on public health and
environment.’’ CAA Section
112(e)(2)(A). Nor did Congress appear to
view the two terms as synonymous.
Under section 112(f), the EPA
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promulgates emission standards at a
level ‘‘with an ample margin of safety’’
to ‘‘protect public health.’’ CAA Section
112(f)(2)(A). The Administrator may go
further and impose more stringent
standards to protect against ‘‘an adverse
environmental effect’’ only after
considering ‘‘cost, energy, safety, and
other relevant factors.’’ Id.
As described above, section
112(n)(1)(A) also provides no clear
standard for analyzing public health
effects—in contrast to, for example,
section 112(f). Under section 112(f), the
issue is whether additional regulation is
needed to ‘‘provide an ample margin of
safety to protect public health.’’ Section
112(f) also expressly incorporates EPA’s
pre-1990 two-part inquiry for evaluating
what level of emission reduction is
needed to provide an ample margin of
safety to protect public health. See CAA
section 112(f)(2)(B) (incorporating EPA’s
two-part ample margin of safety inquiry,
set forth at 54 FR 38044 September 14,
1989, which implemented the
requirements of section 112 of the 1977
CAA).11 By contrast, section
112(n)(1)(A) neither includes the
‘‘ample margin of safety to protect
public health’’ requirement, nor does it
incorporate EPA’s pre-1990 ample
margin of safety inquiry.
Because of the focus on ‘‘public
health’’ in the section 112(n)(1)(A) study
requirement, and because as discussed
above Congress did not define the scope
of the ‘‘appropriate and necessary’’
finding, EPA is reasonably interpreting
section 112(n)(1)(A) to base that finding
on an assessment of whether utility
HAP emissions likely would result in
‘‘hazards to public health.’’
Moreover, EPA reasonably interprets
section 112(n)(1)(A) not to require the
Agency either to study or to base its
‘‘appropriate and necessary’’ finding on
an assessment of environmental effects
unrelated to public health.
As described above, Section
112(n)(1)(A) requires only that the
Administrator ‘‘consider’’ the results of
11 Section 112 of the 1977 CAA directed EPA to
promulgate emission standards ‘‘at the level which
in * * * [the Administrator’s judgment] provides
an ample margin of safety to protect the public
health.’’ Congress substantially amended section
112 in 1990 and enacted several new provisions.
Congress specifically incorporated the ‘‘ample
margin of safety to protect public health’’
requirement into section 112(f), which applies to
any source category that is regulated under section
112(d)(2) and (d)(3). Significantly, Congress did not
include the ‘‘ample margin of safety’’ language in
section 112(n)(1)(A). Instead, Congress directed
EPA to assess the ‘‘hazards to public health
reasonably anticipated to occur’’ from utility HAP
emissions after imposition of the requirements of
the CAA, and then determine whether Utility unit
emissions should be regulated under section 112 of
the CAA.
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the public health study before
determining whether utility regulation
is ‘‘appropriate and necessary.’’ This
mild direction, when paired with the
considerable discretion inherent in any
judgment about whether an action is
‘‘appropriate and necessary,’’ has led
EPA to conclude that the statute permits
the agency to consider other relevant
factors when determining whether to
regulate emissions from utility units
under section 112. This is not to say,
however, that EPA believes it may
ignore the context of section 112(n) in
making its determination.
The Supreme Court has recognized
that ‘‘where Congress includes
particular language in one section of a
statute but omits it in another section of
the same Act,’’ as here, where section
112(n)(1)(A) refers to public health and
conspicuously omits any reference to
adverse environmental effect, ‘‘it is
generally presumed that Congress acts
intentionally * * * in the disparate
inclusion or exclusion.’’ Russello v.
United States, 464 U.S. 16, 23 (1983).
The only direction that Congress
explicitly provided to guide our
‘‘appropriate and necessary’’ finding
was that we consider the results of a
study of only those ‘‘hazards to public
health’’ that the agency ‘‘reasonably
anticipate[s] to occur.’’
EPA must reconcile the broad
discretion to determine what is
‘‘appropriate and necessary’’ with the
implicit Congressional decision that
information about environmental effects
unrelated to human health effects was
not needed for that determination.
Rather than conclude that EPA is
prohibited from considering
environmental effects, however, EPA
interprets section 112(n)(1)(A) to permit
the agency to consider other relevant
factors as part of its ‘‘appropriate and
necessary’’ determination, as refined
further below, but these factors may not
independently, or in conjunction with
one another, justify regulation under
section 112(n) when EPA has concluded
that hazards to U.S. public health are
not reasonably anticipated to occur.
Compare CAA section 112(f)(2)(A)
(Administrator may set a more stringent
standard than is required to protect
health if necessary, considering factors
such as cost, to prevent an adverse
environmental effect).
In evaluating hazards to public health
under section 112(n)(1)(A) we look at
various factors, including, for example,
the affected population, the
characteristics of exposure (e.g., level
and duration), the nature of the data,
including the uncertainties associated
with the data, and the nature and degree
of health effects. In terms of assessing
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health effects, we have numerous tools
at our disposal. See Section VI.H (for
fuller discussion of factors relevant to
assessing the hazards to public health).
For example, for cancer effects, we can
assess the lifetime excess cancer risk,
and for other effects, we look to tools,
such as the reference dose.12 As
explained below, the ‘‘hazards to public
health reasonably anticipated to occur’’
standard is relevant not only for the
Study, but also for the appropriate and
necessary determination.
EPA has also taken note of the context
for assessing ‘‘hazards to public health,’’
for the language of section 112(n)(1)(A),
calls for an analysis of the ‘‘hazards to
public health’’ reasonably anticipated to
‘‘occur as a result of emissions by
electric utility steam generating units.’’
(Emphasis added.) Section 110(a)(2)(D)
provides an instructive comparison in
this regard. In section 110(a)(2)(D),
Congress required that each state
implementation plan contain adequate
provisions ‘‘prohibiting * * * any
source or other type of emissions
activity within the State from emitting
any air pollutant in amounts’’ that will
‘‘contribute significantly to
nonattainment’’ of the national ambient
air quality standards. This provision
demonstrates that Congress knew how
to require regulation of emissions of air
pollutants even where the pollutants
themselves do not cause a problem, but
rather only ‘‘contribute to a problem.’’
Unlike section 110(a)(2)(D), in section
112(n)(1)(A), Congress focused
exclusively on the ‘‘hazards to public
health’’ of HAP emissions ‘‘result[ing]
from’’ Utility Units. Rather, it is the EPA
study performed pursuant to section
112(n)(1)(B), not the inquiry under
section 112(n)(1)(A), that examines all
current anthopogenic sources of Hg
emissions and their effects on human
health and the environment. EPA has
concluded that its inquiry under section
112(n)(1)(A) may reasonably focus
solely on whether the utility HAP
emissions themselves are posing a
hazard to public health. This focus on
utility emissions only is consistent with
Congress’ overall decision to provide for
separate treatment of utilities in section
112(n)(1)(A).
B. Imposition of the Requirements of
This Act
Congress required EPA to examine the
hazards to public health from utility
emissions ‘‘after imposition of the
requirements of this Act.’’ The phrase
‘‘imposition of the requirements of th[e]
Act’’ is susceptible to different
12 Section VI below discusses the reference dose
(‘‘RfD’’) in detail.
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interpretations because Congress did not
specify the scope of the requirements
under the CAA to be considered or,
more importantly, the time period over
which the imposition of requirements
was to be examined. EPA reasonably
interprets the phrase ‘‘imposition of the
requirements of th[e] Act’’ to include
not only those requirements already
imposed and in effect, but also those
requirements that EPA reasonably
anticipates will be implemented and
will result in reductions of utility HAP
emissions. This interpretation is
reasonable in view of the fact that
Congress called for the study to be
completed within three years of
enactment of the 1990 CAA
Amendments. At such time, EPA could
have only forecast, to the extent
possible, how implementation of the
requirements of the CAA would impact
utility HAP emissions, based on the
science and the state of technology at
the time.13
We are interpreting the phrase
‘‘requirements of th[e] Act’’ broadly to
include CAA requirements that could
either directly or indirectly result in
reductions of utility HAP emissions. For
example, certain provisions of the CAA
that affect Utility Units, such as the
requirements of Title I and Title IV,
require controls on pollutants like SO2
or NOX. Although these pollutants are
not HAP, the controls that are required
to achieve the needed reductions have
the added effect of reducing HAP
emissions. Thus, given our
interpretation of the phrase ‘‘imposition
of the requirements of th[e] Act,’’ we
read the first sentence of section
112(n)(1)(A) as calling for a study of the
hazards to public health from utility
HAP emissions that EPA reasonably
anticipates would occur after
implementation of the CAA
requirements that EPA, at the time of
the study, should have reasonably
anticipated would be implemented and
would directly or indirectly result in
reductions of utility HAP emissions.
Finally, it is telling that Congress
directed EPA to examine the utility HAP
emissions remaining ‘‘after imposition
13 Although the December 2000 finding does not
provide an interpretation of the phrase ‘‘after
imposition of the requirements of the[e] Act,’’ the
Utility Study, on which that finding was based,
does account for the phrase by evaluating utility
HAP emission levels in 2010. See Utility Study ES–
2 (the ‘‘2010 scenario was selected to meet the
section 112(n)(1)(A) mandate to evaluate hazards
‘after imposition of the requirements of ’the CAA.’’).
We do not believe that the December 2000 finding
or the January 2004 proposal properly give effect to
all of the terms of section 112(n)(1)(A), including
the first sentence of section 112(n)(1)(A). We
therefore provide our interpretation of the central
terms in that sentence above, as those terms are
relevant to the final actions we are taking today.
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of the requirements of th[e] Act,’’
because there is no other provision in
section 112 that calls for EPA to
examine the requirements of the CAA in
assessing whether to regulate a source
category under section 112.14 Congress
plainly treated Utility Units differently
from other source categories, and that
special treatment reveals Congress’
recognition that Utility Units are a
broad, diverse source category that is
subject to numerous CAA requirements,
including requirements under both Title
I and Title IV, and that such sources
should not be subject to duplicative or
otherwise inefficient regulation.15 See
136 Cong. Rec. H12911, 12934 (daily ed.
Oct. 26, 1990) (Statement of
Congressman Oxley) (stating that the
conferees adopted section 112(n)(1)(A)
‘‘because of the logic of basing any
decision to regulate on the results of
scientific study and because of the
emission reductions that will be
achieved and the extremely high costs
that electric utilities will face under
other provisions of the new Clean Air
Act amendments.’’).
C. Appropriate and Necessary After
Considering the Results of the Study
Section 112(n)(1)(A) requires EPA to
make a determination as to whether
regulation of Utility Units under section
14 Section 112(m)(6) provides an instructive
comparison because it requires EPA to examine the
other provisions of section 112, and to determine
whether those provisions are adequate to prevent
serious adverse effects to public health and the
environment associated with atmospheric
deposition to certain waterbodies. Section
112(m)(6) also requires EPA to promulgate
additional regulations setting emission standards or
control requirements, ‘‘in accordance with’’ section
112 and under the authority of section 112(m)(6),
if EPA determines that the other provisions of
section 112 are adequate, and such regulations are
appropriate and necessary to prevent serious
adverse public health and environmental effects.
Section 112(n)(1)(A) provides EPA far greater
discretion because under that section, EPA is not
only to evaluate the reasonably anticipated public
health hazards remaining ‘‘after imposition of the
requirements of th[e] Act,’’ but also to determine
whether to regulate Utility Units under section 112
of the CAA at all.
15 As noted elsewhere, section 112(n)(1)(A) was
included in the House Committee bill and adopted
by the House; while the Senate included a different
provision. In the Conference Committee, the House
version prevailed. Sen. Durenberger, a Senate
conferee and an evident opponent of the provision,
alluded to another purpose for the provision, which
concerns the fact that ‘‘mercury is a global
problem.’’ Legislative History of the Clean Air Act
Amendments of 1990, at 872 (Oct. 27, 1990)
(statement of Sen. Durenberger). Based on Sen.
Durenberger’s statement, it appears that one of the
reasons for the wide deference Congress accorded
EPA under section 112(n)(1)(A) was to allow EPA
to account for the fact that Hg emissions from U.S.
utilities are a very small part of overall Hg
emissions, and therefore that EPA should exercise
discretion in considering the uncontrollable amount
of risk from Hg that would remain regardless of the
extent to which U.S. utilities are controlled.
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112 is ‘‘appropriate and necessary.’’
Congress did not define the terms
‘‘appropriate’’ and ‘‘necessary,’’ but
provided that regulation of Utility Units
under section 112 could occur only if
EPA determines that such regulation is
both ‘‘appropriate’’ and ‘‘necessary.’’
1. Considering the Results of the Study
The appropriate and necessary
determination is to be made only after
‘‘considering the results of the study’’
required under section 112(n)(1)(A). We
interpret the phrase ‘‘considering the
results of the study’’ to mean that EPA
must consider the results of the study in
making its determination, but that EPA
is not foreclosed from analyzing other
relevant information that becomes
available after completion of the study.
This interpretation is reasonable
because section 112(n)(1)(A) contains no
deadline by which EPA must determine
whether it is ‘‘appropriate and
necessary’’ to regulate Utility Units
under section 112.
Moreover, nothing in section
112(n)(1)(A) suggests that EPA is
precluded from considering new
relevant information obtained after
completion of the Utility Study in
determining whether regulation of
Utility Units under section 112 is
appropriate and necessary. Indeed, the
term ‘‘considering’’ in section
112(n)(1)(A) is analogous to the terms
‘‘based on’’ or ‘‘including,’’ which are
neither limiting nor exclusive terms.16
In a recent case, the DC Circuit rejected
an argument advanced by the
petitioners that an EPA rule was invalid
because the statute required EPA to
promulgate the regulation ‘‘based on the
study,’’ and according to petitioners
EPA’s rule was not based on a study that
met the requirements of the CAA. Sierra
Club v. EPA, 325 F.3d 374 (DC Cir.
2003). In rejecting petitioners’
arguments, the Court held, among other
things, that ‘‘the statute doesn’t say that
the rule must be based exclusively on
the study.’’ Sierra Club v. EPA, 325 F.3d
at 377 (emphasis in original); See also
United States v. United Technologies
Corp., 985 F.2d 1148, 1158 (2d Cir.
1993) (‘‘based upon’’ does not mean
‘‘solely’’); McDaniel v. Chevron Corp.,
203 F.3d 1099, 1111 (9th Cir. 2000).
Consistent with this reasoning, EPA
reasonably interprets the phrase
‘‘considering the results of the study,’’
to mean that EPA must consider the
study, but that it can consider other
relevant information obtained after
completion of the study. Congress could
not have reasonably intended for EPA to
16 In fact, the term ‘‘considering,’’ on its face, is
less limiting than the phrase ‘‘based on.’’
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ignore relevant information concerning
HAP emissions from Utility Units solely
because that information was obtained
after completion of the Utility Study.17
2. Appropriate and Necessary
The condition precedent for
regulating Utility Units under section
112 is whether such regulation is
‘‘appropriate’’ and ‘‘necessary.’’ These
are two very commonly used terms in
the English language, and Congress has
not ascribed any particular meaning to
these terms in the CAA. The legislative
history does not resolve Congress’ intent
with regard to these terms. We therefore
first examine the structure of section
112(n)(1)(A) and then discuss our
interpretation of the terms
‘‘appropriate’’ and ‘‘necessary.’’
a. Examining the Structure of Section
112(n)(1)(A). In interpreting the terms
‘‘appropriate’’ and ‘‘necessary’’ in
section 112(n)(1)(A), we begin with the
structure of section 112(n)(1)(A). As an
initial matter, the order of the terms in
the phrase ‘‘appropriate and necessary’’
suggests that the first decision EPA must
make is whether regulation of Utility
Units under section 112 is
‘‘appropriate.’’ Even if EPA determines
that regulation of Utility Units under
section 112 is appropriate, it must still
determine whether such regulation is
also necessary. Were EPA to find,
however, that regulation of Utility Units
under section 112 met only one prong,
then regulating Utility Units under
section 112 would not be authorized by
the statute.
The structure of section 112(n)(1)(A)
also reveals that the appropriate and
necessary finding is to be made by
reference to the reasonably anticipated
public health risks of utility HAP
emissions that remain after ‘‘imposition
of the requirements of th[e] Act.’’ The
first sentence of section 112(n)(1)(A)
contains an important direction to EPA,
which sets the predicate for the entire
provision. That first sentence calls for
EPA to identify the hazards to public
health reasonably anticipated to occur
as a result of the utility HAP emissions
remaining ‘‘after imposition of the
requirements of th[e] Act.’’ Stated
differently, Congress wanted EPA to
identify the utility HAP emissions that
would remain ‘‘after imposition of the
requirements of th[e] Act’’ and identify
the hazards to public health reasonably
17 Consistent with this interpretation, in
December 2000, EPA relied not only on the Utility
Study, but also on certain information concerning
Hg obtained after completion of the study,
including actual emissions data from coal-fired
plants for calendar year 1999 and a report from the
National Academy of Sciences on the health effects
of methylmercury. See 65 FR 79825–27.
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anticipated to occur as the result of such
emissions. As noted above, we interpret
the phrase ‘‘imposition of the
requirements of th[e] Act’’ to include
those CAA requirements that EPA
should have reasonably anticipated
would be implemented and would
result in reductions of utility HAP
emissions.18 Congress’ focus on the
other requirements of the CAA reflects
its recognition that Utility Units are
subject to numerous CAA provisions
and its intent to avoid duplicative and
unnecessary regulation. We therefore
reasonably conclude that the
appropriate and necessary finding is to
be made by reference to the reasonably
anticipated public health risks from
utility HAP emissions that remain ‘‘after
imposition of the requirements of th[e]
Act.’’
b. EPA’s interpretations of the terms
‘‘appropriate’’ and ‘‘necessary.’’ (i)
Appropriate. In December 2000, EPA
found that it was appropriate to regulate
coal- and oil-fired Utility Units under
section 112. At that time, we did not
provide an interpretation of the term
‘‘appropriate.’’ Instead, we focused on
the following facts and circumstances.
We first found that it was ‘‘appropriate’’
to regulate coal- and oil-fired Utility
Units under section 112 because
‘‘mercury in the environment presents
significant hazards to public health.’’
See 65 FR 79830. We also determined
that it was appropriate to regulate oilfired Utility Units based on the
uncertainties ‘‘regarding the extent of
the public health impact from HAP
emissions from’’ such units. See 65 FR
79830. Finally, we found that it was
appropriate to regulate HAP emissions
from coal-and oil-fired units under
section 112 because we had identified
control options that we anticipated
would effectively reduce certain HAP
emissions. We also indicated that
certain control options could ‘‘greatly
reduc[e] mercury control costs.’’ See 65
FR 79830.
18 The comments of Rep. Oxley, a member of the
Conference Committee, about section 112(n)(1)(A)
support EPA’s interpretation of that provision. Rep.
Oxley stated:
Pursuant to section 112(n), the Administrator
may regulate fossil fuel fired electric utility steam
generating units only if the studies described in
section 112(n) clearly establish that emissions of
any pollutant, or aggregate of pollutants, from such
units cause a significant risk of serious adverse
effects on the public health. Thus, if the
Administrator regulates any of these units, he may
regulate only those units that he determines—after
taking into account compliance with all other
provisions of the CAA and any other federal, state
or local regulation and voluntary emission
reductions—have been demonstrated to cause a
significant threat of adverse effects on public
health.
136 Cong. Rec. H12911, 12934 (daily ed. Oct. 26,
1990) (Statement of Rep. Oxley) (emphasis added).
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In January 2004, we proposed
reversing our ‘‘appropriate’’ finding in
large part. Specifically, we proposed
that it is not ‘‘appropriate’’ to regulate
coal-fired units on the basis of non-Hg
HAP and oil-fired units on the basis of
non-Ni HAP because the record that was
before the Agency in December 2000
indicates that emissions of such
pollutants do not result in hazards to
public health. See Section IV.B.
Webster’s dictionary defines the term
‘‘appropriate’’ to mean ‘‘especially
suitable or compatible.’’ MiriamWebster’s Online Dictionary, 10th ed.
Determining whether something is
‘‘especially suitable or compatible’’ for a
particular situation requires
consideration of different factors. In
section 112(n)(1)(A), Congress requires
EPA to determine whether it is
‘‘appropriate’’ to regulate Utility Units
under section 112. In making this
determination, we begin as we did in
December 2000, by assessing the
paramount factor, which is whether the
level of utility HAP emissions
remaining ‘‘after imposition of the
requirements of th[e] Act’’ would result
in hazards to public health. We
determine whether the remaining utility
HAP emissions cause hazards to public
health by analyzing available health
effects data and assessing, among other
things, the uncertainties associated with
those data, the weight of the scientific
evidence, and the extent and nature of
the health effects. See Section VI. If the
remaining HAP emissions from Utility
Units do not result in hazards to public
health, EPA does not believe that it
would be ‘‘especially suitable’’—i.e.,
‘‘appropriate’’—to regulate such units
under section 112. In this situation,
there would be no need to consider any
additional factors under the
‘‘appropriate’’ inquiry because the
threshold fact critical to making a
finding that it is appropriate to regulate
Utility Units under section 112 would
be missing.
Even if the remaining utility HAP
emissions cause hazards to public
health, it still may not be appropriate to
regulate Utility Units under section 112
because there may be other relevant
factors particular to the situation that
would lead the Agency to conclude that
it is not ‘‘especially suitable’’ or
‘‘appropriate’’ to regulate Utility Units
under section 112. For example, it might
not be appropriate to regulate the utility
HAP emissions remaining ‘‘after
imposition of the requirements of th[e]
Act,’’ if the controls mandated under
section 112(d) would be ineffective at
eliminating or reducing the identified
hazards to public health. Similarly, it
might not be appropriate to regulate the
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remaining utility HAP emissions under
section 112 if the health benefits
expected as the result of such regulation
are marginal and the cost of such
regulation is significant and therefore
substantially outweighs the benefits.
These examples illustrate that situationspecific factors, including cost, may
affect whether it ‘‘is appropriate’’ to
regulate utility HAP emissions under
section 112.19 (See Section
112(n)(1)(A).)
It cannot be disputed that Congress
under section 112(n)(1)(A) entrusted
EPA to exercise judgment by evaluating
whether regulation of Utility Units
under section 112 is, in fact,
‘‘appropriate.’’ We believe that in
exercising that judgment, we have the
discretion to examine all relevant facts
and circumstances, including any
special circumstances that may lead us
to determine that regulation of Utility
Units under CAA section 112 is not
appropriate.20
19 Nothing precludes EPA from considering costs
in assessing whether regulation of Utility Units
under section 112 is appropriate in light of all of
the facts and circumstances presented. The DC
Circuit has indicated that regulatory provisions
should be read with a presumption in favor of
considering costs: ‘‘It is only where there is ‘clear
congressional intent to preclude consideration of
cost’ that we find agencies barred from considering
costs. [Citations omitted.]’’ Michigan v. EPA, 213
F.3d 663, 678 (DC Cir. 2000), cert. den., 532 U.S.
903 (2001) (upholding EPA’s interpretation of
‘‘contribute significantly’’ under CAA section
110(a)(2)(D) to include a cost component). The
Supreme Court’s decision in Whitman v. American
Trucking Assn’s (ATA), Inc., 531 U.S. 457 (2001),
is not to the contrary. In that case, the Court held
that EPA lacked authority to consider costs in the
context of setting the national ambient air quality
standards under CAA section 109(b)(1), because the
‘‘modest words ‘adequate margin’ and ‘requisite’ ’ in
that section do not ‘‘leave room’’ to consider cost.
531 U.S. 466. By contrast, EPA is not setting
emission standards in today’s action, but rather
determining, as Congress directed, whether it is
‘‘appropriate’’ and ‘‘necessary’’ to regulate Utility
Units under CAA section 112. The terms
‘‘appropriate’’ and ‘‘necessary’’ are broad terms,
which by contrast to the terms at issue in ATA do,
in fact, leave room for consideration of costs in
deciding whether to regulate utilities under section
112. Moreover, the legislative history of section
112(n) indicates that Congress intended for EPA to
consider costs. See 136 Cong. Rec. H12911, 12934
(daily ed. Oct. 26, 1990) (statement of Rep. Oxley)
(‘‘[T]he conference committee produced a utility air
toxics provision that will provide ample protection
of the public health while avoiding the imposition
of excessive and unnecessary costs on residential,
industrial and commercial consumers of
electricity.’’). Finally, section 112(n)(1)(A) requires
EPA to consider alternative control strategies, and
the focus on such strategies may reasonably be read
as further evidence of the relevance of costs. See,
e.g., 65 FR 79830 (discussing costs in relation to
certain technologies).
20 Significantly, in December 2000, we
acknowledged that factors other than the hazards to
public health resulting from utility HAP emissions
should be examined in determining whether
regulation of Utility Units is appropriate under
section 112. Indeed, after concluding that the Hg
emissions from coal-fired Utility Units caused
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(ii) Necessary. Like the ‘‘appropriate’’
finding, the ‘‘necessary’’ finding must be
made by reference to the utility HAP
emissions remaining after imposition of
the requirements of the CAA.
Specifically, we interpret the term
‘‘necessary’’ in section 112(n)(1)(A) to
mean that it is necessary to regulate
Utility Units under section 112 only if
there are no other authorities available
under the CAA that would, if
implemented, effectively address the
remaining HAP emissions from Utility
Units. Assessing whether an alternative
authority would effectively address the
remaining utility HAP emissions would
involve not only: (a) An analysis of
whether the alternative legal authority,
if implemented, would address the
identified hazards to public health,
which was a concept specifically
addressed in December 2000 and in the
January 2004 proposal, but also (b) an
analysis of whether the alternative legal
authority, if implemented, would result
in effective regulation, including, for
example, its cost-effectiveness and its
administrative effectiveness. See
Michigan v. EPA, 213 F.3d, 663, 678
(addressing consideration of costs).
This interpretation of the term
‘‘necessary’’ differs slightly from the
interpretation advanced in December
2000 and January 2004. In December
2000 and January 2004, we interpreted
the term ‘‘necessary’’ to mean that it is
only necessary to regulate Utility Units
under section 112 if there are no other
authorities under the CAA that would
adequately address utility HAP
emissions. Several commenters noted
that under this interpretation, EPA
could never regulate HAP under section
112 if it identified an alternative viable
legal authority. In light of these
comments and further review of section
112(n)(1)(A), we refined our
interpretation of the term ‘‘necessary’’ as
noted above. We agree that if we found
an alternative authority under the CAA
but we also determined that such
authority would not effectively address
the remaining HAP emissions, we
should be able to address those
emissions under section 112.
Accordingly, we maintain that it is
necessary to regulate Utility Units under
section 112 only if there are no other
authorities under the CAA that, if
implemented, would effectively address
the remaining HAP emissions from
Utility Units.
hazards to public health, we proceeded with the
appropriate inquiry and examined whether there
were any control technologies that could effectively
reduce Hg. We also commented on the costs of
achieving such reductions. See, e.g., 65 FR 79828,
79830.
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Some commenters argued that the
‘‘appropriate and necessary’’ finding is
a public health threshold finding, not an
investigation into whether another
provision of the CAA would address
HAP emissions from utilities. This
argument is without merit, however,
because it conflates the terms
‘‘appropriate’’ and ‘‘necessary’’ and
renders one term mere surplusage.
Congress required EPA to determine
whether it was both appropriate and
necessary to regulate Utility Units under
section 112. EPA agrees that it must
evaluate the hazards to public health
associated with HAP from utilities in
terms of assessing whether regulation
under section 112 is ‘‘appropriate.’’ But
Congress meant something different by
the term ‘‘necessary,’’ and EPA’s
interpretation of that term is reasonable.
Moreover, we believe that the emissions
inquiry envisioned under the first
sentence of section 112(n)(1)(A) is
distinct from the ‘‘necessary’’ inquiry
called for by the last sentence of section
112(n)(1)(A), because under the
‘‘necessary’’ inquiry the issue is not
whether EPA reasonably anticipated
that a particular provision of the CAA
will be implemented and will reduce
HAP emissions, but rather whether
there are any other authorities in the
CAA that could be implemented, and if
implemented, could effectively address
the hazards to public health that result
from the remaining HAP emissions.
Other commenters argued that EPA
cannot consider other statutory
authorities under the ‘‘necessary’’ prong
of the ‘‘appropriate and necessary’’
inquiry because those authorities do not
provide for regulation of utility HAP
according to the provisions of CAA
section 112(d) and (f). This argument is
also without merit because it again
renders mere surplusage the
‘‘necessary’’ prong of the determination.
Moreover, as explained above, Congress
did not incorporate the requirements of
section 112(f) into section 112(n)(1)(A),
but instead, as we interpret section
112(n)(1)(A), called on EPA to consider
the ‘‘hazards to public health reasonably
anticipated to occur’’ from utility HAP
emissions after imposition of the
requirements of the CAA, in
determining whether it is both
appropriate and necessary to regulate
Utility Units under section 112.
3. The Timing and Nature of the
‘‘Appropriate and Necessary’’
Determination
Congress set no deadline in section
112(n)(1)(A) by which EPA must
determine whether regulation of Utility
Units is appropriate and necessary. We
believe that Congress provided
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sufficient discretion under section
112(n)(1)(A)—in terms of both the
substance and the timing of the
appropriate and necessary finding—that
nothing precludes us from revising our
appropriate and necessary finding if we
determine either that the finding was in
error based on information before the
Agency at the time of the finding, or that
the finding is incorrect given new
information concerning utility HAP
emissions obtained after issuance of the
finding. Both of these situations are
present here, as explained in section IV
below.
Moreover, EPA reasonably interprets
the last sentence of section 112(n)(1)(A)
as authorizing EPA to issue separate
appropriate and necessary findings for
different subcategories of ‘‘electric
utility steam generating units.’’ EPA
typically subcategorizes large source
categories such as utilities. This is
especially true for Utility Units because
the nature of the fuel used in different
units (e.g., coal-, oil-, or gas-fired Utility
Units), affects the type and amount of
HAP emitted from the units, which, in
turn, affects the issue of whether
hazards to public health may exist from
such emissions.21 Even where section
112(n)(1)(A) read to require EPA to
make only one appropriate and
necessary finding for all ‘‘electric utility
steam generating units,’’ EPA’s
conclusions, as described below, would
remain the same.
IV. Revision of the December 2000
Appropriate and Necessary Finding
In Section II above, we summarize the
December 2000 appropriate and
necessary finding for coal- and oil-fired
Utility Units. In this section, we explain
why we now believe that the December
2000 finding lacked foundation and
therefore was erroneous. We also
address below certain new information
obtained since the finding that confirms
that it is not appropriate and necessary
to regulate coal- and oil-fired Utility
Units under section 112. Our discussion
below is divided into two sections, the
first of which concerns the December
2000 finding for coal-fired units, and the
second of which addresses the
December 2000 finding for oil-fired
units.
A. Revision of the December 2000
Appropriate and Necessary Finding for
Coal-fired Units
The majority of the December 2000
finding concerned Hg emissions from
coal-fired Utility Units. See, e.g., 65 FR
21 We received no adverse comments concerning
our subcategorization of Utility Units for purposes
of section 112(n)(1)(A).
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79826 (‘‘mercury * * * is emitted from
coal-fired units, and * * * is the HAP
of greatest concern to public health from
the industry.’’); 65 FR 79829–30
(conclusions section of December 2000
finding focuses almost exclusively on
Hg); Utility Study, ES–27 (‘‘mercury
from coal-fired utilities is the HAP of
greatest potential concern.’’). For that
reason, we first address how EPA erred
in making the appropriate and necessary
finding for coal-fired units based on Hg
emissions. We then discuss the
December 2000 finding for coal-fired
units with regard to non-Hg HAP.
1. It Is Not Appropriate and Necessary
To Regulate Coal-Fired Units on the
Basis of Hg Emissions
a. It Is Not Appropriate to Regulate
Coal-fired Units on the Basis of Hg
Emissions. As noted above, EPA’s
December 2000 ‘‘appropriate’’ finding is
framed primarily in terms of health
effects resulting from Hg emissions from
coal-fired Utility Units.22 See
65 FR 79829. The December 2000
finding also discusses environmental
effects, primarily in the context of
public health. In particular, the
appropriate finding discusses the effects
of Hg on fish because the public’s
primary route of exposure to Hg is
through consumption of fish containing
methylmercury. See 65 FR 79829–30.
See also Section VI (discussing health
effects of Hg). The December 2000
finding also discusses briefly the effects
of methymercury on certain fish-eating
wildlife, such as racoons and loons. See
65 FR 79830.
As explained above, EPA interprets
section 112(n)(1)(A) as not requiring the
Agency to consider environmental
effects of utility HAP emissions that are
unrelated to public health. Nevertheless,
EPA believes it has authority under the
‘‘appropriate’’ inquiry to consider other
factors, including non-public health
22 The ‘‘appropriate’’ rationale set forth in the
December 2000 finding focused exclusively on Hg
with regard to coal-fired Utility Units. The
December 2000 ‘‘necessary’’ finding can be read,
however, to suggest that under the appropriate
prong, EPA also determined that non-Hg from coalfired Utility Units resulted in hazards to public
health. See 65 FR 79830 (‘‘It is necessary to regulate
HAP emissions from coal- and oil-fired’’ Utility
Units under section 112 ‘‘because the
implementation of other requirements of the CAA
will not address the serious public health and
environmental hazards arising from such
emissions.’’). As explained below in section IV.B,
the record that was before the Agency in December
2000 confirms that the non-Hg HAP emissions
remaining ‘‘after imposition of the requirements of
th[e] Act’’ do not result in hazards to public health.
In the proposed rule, EPA solicited comment on
this issue. We did not receive any new information
concerning non-Hg HAP during the comment
period that would cause us to change our position
as to these HAP.
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related environmental factors. As
explained above, however, given the
focus in section 112(n)(1)(A) on hazards
to public health, we believe that
environmental factors unrelated to
public health, although they can be
considered in the appropriate inquiry,
may not independently or, in
conjunction with one another, justify
regulation of Utility Units under section
112 when EPA has concluded that
hazards to public health are not
reasonably anticipated to result from
utility HAP emissions.
EPA reasonably addressed non-public
health related environmental factors,
such as exposure to wildlife, in the
December 2000 finding, because we
separately concluded that Hg emissions
from coal-fired Utility Units pose
hazards to public health. As explained
below, we believe that our December
2000 appropriate finding lacks
foundation, and that conclusion is
supported by certain recent information.
Specifically, we conclude today that the
level of Hg emissions remaining after
imposition of the requirements of the
Act will not cause hazards to public
health, and therefore we need not
consider other factors, such as nonpublic health related environmental
effects. We do, of course, discuss the
effects of Hg on fish, because the
ingestion of fish contaminated with
methylmercury is the public’s primary
route of exposure to Hg. See Section VI
(discussing health effects of Hg).23
As noted above, EPA’s December 2000
appropriate finding for coal-fired units
hinged primarily on the health and
environmental effects resulting from Hg
emissions. See 65 FR 79830 (‘‘mercury
in the environment presents significant
hazards to public health and the
environment.’’). This finding lacks
foundation, however, for the reasons
described below.
(i) The December 2000 Appropriate
Finding Is Overbroad To The Extent It
Hinged On Environmental Effects. EPA
should not have made its appropriate
23 We note, however, that as part of our overall
inquiry into the effects of Hg emissions, we
assessed the available information on the
environmental effects of Hg emissions, including
effects that appear to be unrelated to public health.
See 1997 Mercury Report to Congress. While that
information, in a very general sense, suggests that
environmental effects of Hg emissions (unrelated to
public health) may be of some concern and
therefore warrant further study, the available
information is not specific to the effects of Hg
emissions from domestic utilities. See RIA
Appendix C. Thus, even if EPA were either required
or permitted to give unlimited consideration to
these non-health-related environmental effects of
utility Hg emissions in making the regulatory
determination under section 112(n)(1)(A), we
would conclude that there is insufficient causal
information to conclusively link utility emissions to
deleterious effects (in wildlife) from Hg exposure.
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finding because of ‘‘hazards to * * *
the environment’’ resulting from Hg
emissions from coal-fired Utility Units.
Section 112(n)(1)(A) requires EPA to
analyze only the ‘‘hazards to public
health’’ resulting from utility HAP
emissions, not the environmental effects
caused by such emissions. Under
section 112(n)(1)(A), the condition
precedent for regulation under section
112 is public health hazards, not
environmental effects, which Congress
included in other provisions of section
112. See, e.g., 112(c)(3) (‘‘a threat of
adverse effect to human health or the
environment.’’). The Supreme Court has
recognized that ‘‘where Congress
includes particular language in one
section of a statute but omits it in
another section of the same Act, it is
generally presumed that Congress acts
intentionally * * * in the disparate
inclusion or exclusion.’’ Russello v.
United States, 464 U.S. 16, 23 (1983).
Accordingly, EPA erred in its December
2000 ‘‘appropriate’’ finding to the extent
that it hinged on the environmental
effects of HAP, including Hg.
(ii) The December 2000 Appropriate
Finding Lacks Foundation Because EPA
Did Not Fully Consider The Hg
Reductions That Would Result From
‘‘Imposition of the Requirements of th[e]
Act.’’ As explained above, EPA
interprets section 112(n)(1)(A) as
providing that the ‘‘appropriate’’ finding
should be made by reference to the level
of HAP emissions remaining after
‘‘imposition of the requirements of th[e]
Act.’’ We reasonably interpret the
phrase ‘‘imposition of the requirements
of th[e] Act’’ to include those
requirements that EPA should have
reasonably anticipated would be
implemented and would result in
reductions of utility HAP emissions.
The December 2000 ‘‘appropriate’’
finding lacks foundation because EPA
failed to fully account for the Hg
emissions remaining after ‘‘imposition
of the requirements of th[e] Act.’’ 24 That
failure resulted in an overestimate of the
remaining utility Hg emissions, which is
the level of emissions that we
considered in making our December
2000 appropriate finding. Had we
properly considered the Hg reductions
remaining ‘‘after imposition of the
requirements of th[e] Act’’ in December
2000, we might well have (and, as
discussed below, now believe should
have) reached a different conclusion as
to whether it was ‘‘appropriate’’ to
24 For ease of reference, we refer to the level of
utility Hg emissions remaining ‘‘after imposition of
the requirements’’ of the CAA as the ‘‘remaining Hg
emissions.’’
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regulate coal-fired units on the basis of
Hg emissions.
We begin our analysis with a brief
background concerning the Utility
Study. In an attempt to address the
requirement in section 112(n)(1)(A) of
evaluating utility emissions ‘‘after
imposition of the requirements of th[e]
Act’’, the Utility Study estimates utility
HAP emissions as of the year 2010. See
Utility Study ES–1. In quantifying 2010
utility HAP emissions, our analysis
focused almost exclusively on the acid
rain provisions of Title IV. Title IV of
the CAA establishes a national, annual
emissions cap for sulfur dioxide (SO2)
emissions from Utility Units, which is
to be implemented in two phases. Phase
I commences January 1, 1995, and Phase
II on January 1, 2000.
EPA relied in the Utility Study on a
1997 Department of Energy report
concerning the effects of the
implementation of Title IV of the CAA
on utilities. Utility Study 2–31 to 2–33,
2–39. That report provides that 53
percent of Utility Units subject to Phase
1 requirements switched to a lowersulfur coal, 27 percent purchased
additional emissions allowances, and 16
percent (i.e., 27 Utility Units) installed
flue gas scrubbers to comply with the
Phase I requirements.25 In the 2010
utility HAP emissions analysis, EPA
accounted for the 27 Utility Units that
installed scrubbers to comply with the
phase I requirements. Utility Study 2–
31. EPA accounted for these scrubbers
in the 2010 analysis because it
recognized that scrubbers, which
control SO2, achieve HAP reductions,
including Hg.26 Utility Study at ES–19
& 25, 1–2, 2–32, 3–14 (discussing ability
of PM controls (including SO2 controls)
to reduce Hg and other HAP emissions
from Utility Units).27 Significantly,
however, EPA did not incorporate into
the 2010 utility HAP emissions analysis
25 Flue gas scrubbers are a type of control
technology used to control SO2.
26 EPA did not account in its 2010 analysis for the
installation of any scrubbers associated with Phase
II of the acid rain program, because it only had
industry projections as to which units would install
scrubbers and, for various reasons, it did not find
those projections reliable. Utility Study 2–31 to 2–
33.
27 In the December 2000 finding, we indicate that
recent data show that technologies used to control
criteria pollutants, like PM, SO2, and NOX are not
‘‘effective’’ in controlling Hg. See 65 FR 79828. This
statement is incorrect. It is not only inconsistent
with other statements in the December 2000
finding, it is contrary to the record that was before
the Agency in December 2000. The record indicates
that technologies used to control PM, SO2, and NOX
do reduce HAP, including Hg. Furthermore, insofar
as Hg is concerned, these technologies result in
important reductions of oxidized Hg, which is the
type of Hg that tends to deposit locally and
regionally. Utility Study at ES–19 & 25, 1–2, 2–32,
3–14.
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16003
the Hg reductions that we reasonably
should have anticipated achieving
through implementation of the
requirements of Title I of the CAA. See
Utility Study, at 2–31 to 2–33. In this
regard, EPA erred in, at least, two
respects.
First, EPA erred by not accounting for
the utility Hg reductions that it should
have reasonably anticipated would
result from implementation of the
nonattainment provisions of Title I,
including, in particular, the revised
NAAQS for ozone that EPA issued in
July 1997, before the report was
completed, under the nonattainment
provisions.28 The Utility Study
expressly recognizes that the revised
NAAQS would result in, among other
things, significant reductions of SO2 and
NOX. See generally Utility Study at 1–
2 to 1–3. The Utility Study also
indicates that the revised NAAQS
would result in approximately a 16
percent reduction (11 tons per year) of
Hg emissions by 2010, primarily due to
the fact that Utility Units would need to
install controls, like scrubbers, to meet
the SO2 reductions needed to attain the
PM NAAQS. (Utility Study 1–3, ES–25,
3–14). Notwithstanding these significant
estimated reductions, EPA did not take
these reductions into account in its 2010
utility HAP emissions analysis.29 ES–25
(‘‘analyses performed to assess
compliance with the revised NAAQS
* * * indicate that Hg emissions in
2010 may be reduced by approximately
16 percent (11 tpy) over those projected
in this report.’’). Accordingly, the
December 2000 appropriate finding
lacks foundation because we made the
finding based on an inaccurate level of
Hg emissions remaining after imposition
of the requirements of the CAA. Had we
properly accounted in December 2000
for the 11 tons per year of Hg reductions
that we projected in our own analyses,
we might well have (and, as discussed
below, now believe should have)
concluded that it was not appropriate to
regulate coal-fired units under section
28 For additional background concerning the
nonattainment provisions of Title I and the revised
PM and ozone NAAQS, see Section V below.
29 In the Utility Study, we explained that we did
not account for the identified Hg reductions in the
2010 analysis because we lacked information on the
specific number of units that would install
scrubbers and related PM control technologies since
we had not yet designated which areas of the
country were in nonattainment of the revised
NAAQS. See Utility Study 2–32. Although we had
not yet designated areas of the country as being in
nonattainment of the revised standards, as
explained in section V, we were generally aware of
the likelihood of widespread nonattainment with
the revised NAAQS. In fact, that recognition formed
the basis of our analysis that resulted in an
estimated 16 percent reduction in Hg emissions
from implementation of the revised NAAQS.
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112 on the basis of the remaining Hg
emissions. Indeed, recent modeling
confirms that we likely would have
reached such a conclusion. That
modeling specifically demonstrates that
about a 13 ton reduction in utility Hg
emissions from 1990 levels would result
in a level of Hg emissions that does not
cause hazards to public health. We
conducted these recent analyses in
conjunction with the recently signed
Clean Air Interstate Rule (‘‘CAIR’’)
issued pursuant to CAA section
110(a)(2)(D), which is explained more
fully in section V below.
Second, EPA erred in December 2000
by not examining, and therefore not
accounting for, the reductions in utility
Hg emissions that would result from
two other rules issued pursuant to Title
I of the CAA. The first rule set new
source performance standards (‘‘NSPS’’)
under CAA section 111(b) for NOX
emitted from utility and industrial
boilers. The second rule, promulgated
under CAA section 110(a)(2)(D),
requires 22 states and the District of
Columbia to revise their state
implementation plans (‘‘SIP’’) to
mitigate for the interstate transport of
ozone. This rule is called the NOX SIPcall rule and requires significant
reductions of NOX emissions in the
eastern half of the United States. EPA
determined those NOX reductions by
analyzing Utility Units and large
nonpoint utility sources and identifying
the amount of reductions that those
units could achieve in a ‘‘highly costeffective’’ manner. Both the NOX SIP
call and the NSPS rule were premised
on a NOX control technology called
selective catalytic reduction (‘‘SCR’’).
The data on the effectiveness of SCR at
controlling utility Hg emissions was
limited in February 1998. See Utility
Study 2–32. As of December 2000,
however, EPA had additional data that
confirmed that SCR would lead to
certain reductions in utility Hg
emissions. See, e.g., 65 FR 79829 (SCR—
a NOX control technology ‘‘may also
oxidize mercury and therefore enhance
mercury control.’’). EPA therefore
should have been able to reasonably
estimate in December 2000 that some Hg
reductions would occur as the result of
implementation of the NSPS and the
NOX SIP-call rules. Because we did not
account for reductions in utility Hg
emissions as the result of
implementation of these rules, we made
our appropriate finding in December
2000 based on an incorrect estimate of
the remaining Hg utility emissions.
Based on all of the above, the December
2000 ‘‘appropriate’’ finding lacked
foundation because it was not based on
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the level of utility Hg emissions
remaining ‘‘after imposition of the
requirements of th[e] Act.’’
(iii) It Is Not Appropriate to Regulate
Coal-fired Utility Units Under Section
112 on the Basis of Hg Emissions
Because New Information Reveals that
the Level of Utility Hg Emissions
Remaining After Imposition of the
Requirements of the CAA Does Not
Cause Hazards to Public Health. In
addition to the errors noted above with
regard to the December 2000 finding, we
have new information that confirms that
it is not appropriate to regulate coalfired units under section 112 on the
basis of Hg emissions. EPA recently
signed a rulemaking implementing
section 110(a)(2)(D), called the Clean
Air Interstate Rule. (See Section V
below for further discussion of CAIR.)
This rulemaking, among other things,
requires a number of eastern states to
develop SIPs providing for substantial
reductions of SO2 and NOX emissions.
Although affected states retain
flexibility to decide how to achieve
those reductions, EPA has concluded
that the reductions from Utility Units
are highly cost-effective, and anticipates
that affected states will meet their
emission reduction obligations by
controlling Utility Unit emissions. EPA
also concluded that the technologies
that most cost-effectively achieve SO2
and NOX reductions for Utility Units are
scrubbers for SO2 and SCR for NOX.
These technologies, as noted above,
result in reductions of utility Hg
emissions. In conjunction with the CAIR
rulemaking, EPA analyzed the nature of
Hg emissions that would remain after
implementation of the rule and assumed
that states would choose to regulate
Utility Units, which is the most costeffective option for achieving the
required reductions. That modeling
reveals that the implementation of
section 110(a)(2)(D), through CAIR,
would result in a level of Hg emissions
from Utility Units that would not cause
hazards to public health. See Section V
for further detail. Because this new
information demonstrates that the level
of Hg emissions projected to remain
‘‘after imposition of’’ section
110(a)(2)(D) does not cause hazards to
public health, we conclude that it is not
appropriate to regulate coal-fired Utility
Units under section 112 on the basis of
Hg emissions.30
30 The reductions achieved through CAIR overlap,
in part, with the 11 tons per year of reductions
discussed in the prior section, which EPA estimated
in 1998 would occur as the result of
implementation of the revised NAAQS. The
reductions necessarily overlap because in the
Utility Study EPA projected forward 13 years, by
examining utility HAP emissions in 2010. In
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In addition to CAIR, we today
finalized a rule pursuant to section 111,
called the Clean Air Mercury Rule
(‘‘CAMR’’). (See section VII below for
further discussion of CAMR.) That rule
requires even greater reductions in Hg
emissions from coal-fired Utility Units
than CAIR. As explained in greater
detail in Section VI, the computer
modeling completed in support of that
rule, like the modeling completed on
CAIR, demonstrates that CAMR,
independent of CAIR, will result in
levels of utility Hg emissions that do not
result in hazards to public health. Thus,
the implementation of CAMR provides
an independent basis for our conclusion
that it is not appropriate to regulate
coal-fired Utility Units under section
112 because the utility Hg emissions
remaining after implementation of
section 111 will be at a level that results
in no hazards to public health.31
b. It Is Not Necessary to Regulate
Coal-fired Units on the Basis of Hg
Emissions. Even if Congress had
intended EPA to focus on a more
limited set of requirements in
interpreting the phrase ‘‘after imposition
of the requirements of th[e] Act,’’ that
would mean only that EPA did not err
in December 2000 in terms of its
‘‘appropriate’’ finding for coal-fired
units based on Hg emissions. EPA
nevertheless concludes today that it still
erred in December 2000 with regard to
its ‘‘necessary’’ finding. In section
112(n)(1)(A), Congress called on EPA to
make a finding as to whether regulation
of Utility Units under section 112 was
not only ‘‘appropriate,’’ but
‘‘necessary.’’ To give effect to the term
‘‘necessary,’’ we interpret the
‘‘necessary’’ prong of the section
112(n)(1)(A) inquiry to require EPA to
examine whether there are any other
available authorities under the CAA
that, if implemented, would effectively
address the remaining Hg emissions
from coal-fired Utility Units.
analyzing the level of utility Hg emissions
remaining ‘‘after imposition of [section
110(a)(2)(D)]’’ through CAIR, we are accounting for
the full impact of CAIR and that necessarily
includes reductions that occur between today and
2010, and beyond. See Section V (discussing
requirements of CAIR in 2010 and 2015).
31 Nothing in section 112(n)(1)(A) precludes EPA
from revising a prior appropriate and necessary
finding based on new information. In light of CAIR
and, independently, CAMR, we can now reasonably
anticipate the reductions in utility Hg emissions
that would result from implementation of sections
110(a)(2)(D) and 111 of the CAA. Accordingly, we
are accounting for those reductions in assessing the
level of utility Hg emissions remaining after
‘‘imposition of the requirements of th[e] Act,’’
which include section 110(a)(2)(D) and 111. We
then based our new appropriate finding on these
remaining Hg emissions.
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In December 2000, EPA did not
consider CAA sections 110(a)(2)(D) 32
and 111,33 which are viable alternative
authorities under the CAA, that, if
implemented, would effectively address
the remaining utility Hg emissions. See
Section VI below. Regulation under
these authorities would effectively
address the remaining utility Hg
emissions for two primary reasons.
First, as demonstrated in section VI
below, the level of utility Hg emissions
remaining after implementation of CAIR
will not result in hazards to public
health. Similarly, as shown in section VI
below, the CAMR, which requires even
greater Hg reductions than CAIR, will,
once implemented, result in a level of
utility Hg emissions that does not cause
hazards to public health.
In addition, controlling Hg emissions
through a cap-and-trade system—
whether that control is through direct
regulation under section 111 or indirect
regulation under section 110(a)(2)(D)—
is an efficient means of regulating
Utility Units. See CAMR final rule
(signed on March 15, 2005) (discussing
basis and purpose of the regulations). As
an initial matter, a cap-and-trade
system, as opposed to the control regime
imposed pursuant to section 112(d),
provides Utility Units the flexibility to
pursue a least-cost compliance option to
achieve the required emissions
reductions.
Sources have the choice of complying
with the reductions in a variety of ways,
such as fuel switching, installing
different pollution control technologies,
installing new or emerging control
technologies and/or buying allowances
to emit from another source that has
32 In January 2004, the proposed section 111 rule
was premised, in part, on the reductions in Hg
emissions that EPA anticipated would be achieved
through CAIR. In response to comments received on
the CAMR, we conducted additional modeling that
confirmed that CAIR alone, once implemented,
would result in levels of utility Hg emissions that
do not cause hazards to public health. (See Section
VI below). Accordingly, we now believe that CAA
section 110()(2)(D) constitutes yet another viable
authority under the CAA that, once implemented,
will effectively address the remaining utility Hg
emissions.
33 In the Utility Study, we considered section 111
of the CAA, noting that ‘‘new source performance
standards currently provide the major regulatory
authority for the control of air emissions from
utilities.’’ Utility Study 1–6. We recognized that we
had issued NSPS for PM for Utility Units and we
noted that such requirements would result
indirectly in the control of certain HAP, including
Hg. EPA did not, however, address in the Utility
Study the question of whether HAP from utilities
could be regulated under the authority of section
111 [Utility Study 1–5–6]. As explained in the
proposed rule, we conducted a thorough reevaluation of the provisions of the CAA and have
concluded that section 111 provides authority to
regulate HAP from new and existing Utility Units.
See Section VII below (discussing legal authority
under section 111).
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controlled its emissions to a level below
what the regulation requires. This
compliance flexibility allows Utility
Units to respond to changing electricity
generation demands, economic market
conditions or unanticipated weather
situations (e.g., extremely hot or cold
periods) without jeopardizing their
compliance status, or the stability of the
overall cap. In addition, the certainty
provided by the emissions cap and the
timeline for declining emissions provide
important information for industry to
make strategic, long-range business
decisions.
Moreover, under a cap-and-trade
approach, most of the reductions are
projected to result from larger units
installing controls and selling excess
allowances, due to economies of scale
realized on the larger units versus the
smaller units. Indeed, EPA’s modeling
of trading programs demonstrates that
large coal-fired Utility Units, which
tend to have higher levels of Hg
emissions, will achieve the most costeffective emission reductions. These
units are more likely to over-control
their emissions and sell allowances,
than to not control and purchase
allowances. This model prediction is
consistent with principles of capital
investment in the utility industry.
Under a trading system where the firm’s
access to capital is limited, where the
up-front capital costs of control
equipment are significant, and where
emission-removal effectiveness
(measured in percentage of removal) is
unrelated to plant size, from an
economics standpoint, the utility
company is more likely to allocate
pollution-prevention capital to its larger
facilities than to the smaller plants
(since more allowances will be earned
from the larger facilities). Economies of
scale of pollution control investment
will also favor investment at the larger
plants. Further, insofar as large coalfired Utility Units tend to be newer and/
or better maintained than medium-sized
and small facilities, it can be expected
that companies will favor investments
in plants with a longer expected
lifetime. These modeled predictions are
consistent with the pattern of behavior
that EPA has observed over the past
decade through implementation of the
SO2 emissions trading program under
Title IV of the CAA. Thus, under a capand-trade program, Hg reductions result
from units that are most cost effective to
control, which enables those units that
are not considered to have cost effective
control alternatives to use other
mechanisms for compliance, such as
buying allowances. By contrast,
regulating pursuant to a control regime
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like section 112(d) does not result in the
cost efficiencies that are attendant a capand-trade program. For example, under
section 112(d), each facility must meet
a specific level of emission control,
which can result in increased
compliance costs, particularly for the
smaller Utility Units given economies of
scale.
Finally, trading provides greater
incentives for the development and
adoption of new technologies, which
could lead to a greater level of emissions
control. See generally 69 FR 4686–87.
An additional benefit of the cap-andtrade programs under sections
110(a)(2)(D) and 111 is that they
dovetail well with each other. In
particular, the coordinated regulation of
SO2, NOX, and Hg through CAIR and
CAMR improves the cost effective
manner of regulation because the
reductions are being achieved
simultaneously using in some cases the
same technology to control more than
one pollutant. In addition, the cap-andtrade programs under sections
110(a)(2)(D) complement other cap-andtrade programs that directly affect
Utility Units, such as the NOX SIP-call
final rule and the regulations
implementing Title IV, which only
further enhances the efficiencies of
emission control from such units.
In light of CAA sections 110(a)(2)(D)
and 111, we believe that we should not
have concluded in December 2000 that
it ‘‘is necessary’’ to regulate Utility
Units under section 112 and therefore
our ‘‘necessary’’ finding was in error.
Moreover, even setting aside the error
that we made in December 2000, we
now recognize the availability of these
other statutory provisions and we
further conclude today that it is not
necessary to regulate coal-fired Utility
Units under section 112 on the basis of
the remaining Hg emissions. CAA
section 110(a)(2)(D), as implemented
through CAIR, and independently
section 111, as implemented through
CAMR, will effectively address the Hg
emissions remaining from coal-fired
Utility Units ‘‘after imposition of the
requirements of th[e] Act.’’
In sections V and VII below, we
address sections 110(a)(2)(D) and 111
and provide a thorough discussion of
the legal authority under each
provision. We also explain in Section VI
that after implementation of CAIR, and
independently, CAMR, we do not
anticipate hazards to public health
resulting from Hg emissions from coalfired Utility Units.
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2. It Is Not Appropriate and Necessary
to Regulate Coal-Fired Units on the
Basis of Non-Hg Emissions
In the study required by section
112(n)(1)(A), and detailed in the Utility
Study, EPA identified 67 HAP as
potentially being emitted by Utility
Units. (Utility Study, ES–4). Based on a
screening assessment designed to
prioritize HAP for further evaluation,
EPA identified 14 HAP as a priority for
further evaluation. (Id.). Of the 14 HAP
identified for further evaluation, 12
HAP (arsenic, beryllium, cadmium,
chromium, manganese, nickel, hydrogen
chloride, hydrogen fluoride, acrolein,
dioxins, formaldehyde and
radionuclides) were identified for
further study based on potential for
inhalation exposure and risks. (Utility
Study, ES–6). Four of those 12 HAP
(arsenic, cadmium, dioxins and
radionuclides) plus Hg and lead were
considered priority for multipathway
exposure. (Id.). Of those six HAP, four
(arsenic, Hg, dioxins and radionuclides)
were identified as the highest priority to
assess for multipathway exposure and
risks. (Utility Study, ES–6, 7). The other
53 HAP were not evaluated beyond the
screening assessment. (Utility Study,
ES–7).
In evaluating the potential for
inhalation exposure and risks for the 12
HAP identified through the screening
assessment as priority for that purpose,
EPA estimated the high-end inhalation
cancer risk for each HAP identified as
a carcinogen and the high-end
inhalation noncancer risks for the
remaining HAP for both coal- and oilfired Utility Units in 2010. (Utility
Study, 6–16, tables 6–8 and 6–9). That
evaluation indicated that there was no
maximum individual risk (MIR) for
cancer greater than 1 × 10 6 for
beryllium, cadmium, dioxin and nickel
emissions from coal-fired Utility Units
and for beryllium, cadmium and dioxin
emissions from oil-fired Utility Units.
(Id.) With regard to dioxins, the Utility
Study specifically concluded that the
quantitative exposure and risk results
did not conclusively demonstrate the
existence of health risks of concern
associated with inhalation exposures to
utility emissions on a national scale or
from any actual individual utility.
(Utility Study, 11–5). The Utility Study
thus indicates that inhalation of
beryllium, cadmium and dioxin
emissions from coal and oil-fired Utility
Units and emissions of nickel from oilfired Utility Units are not of significant
concern from a public health standpoint
because such exposure does not present
a maximum individual risk (MIR) for
cancer greater than 1 × 10 6. With
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regard to lead emissions, EPA found
that emission quantities and inhalation
risks were relatively low and, therefore,
decided not to conduct future
evaluations of multipathway exposures
to lead resulting from Utility Unit
emissions. (Utility Study, ES–24). For
arsenic, EPA concluded that there were
several uncertainties associated with
both the cancer risk estimates and the
health effects data such that further
analyses were needed to characterize
the inhalation risks posed by arsenic
emissions from Utility Units. (Utility
Study, ES–21). The inhalation exposure
assessment did not identify any
exceedances of the health benchmarks
(e.g., RfCs) for hydrogen chloride or
hydrogen fluoride, thus indicating that
Utility Unit emissions of those HAP did
not pose a significant public health
concern. (Utility Study chapters 6 and
9.)
a. It Is Not Appropriate to Regulate
Coal-fired Units on the Basis of Nonmercury HAP Emissions. The EPA erred
in the December 2000 Regulatory
Determination to the extent that its
‘‘appropriate’’ finding for coal-fired
Utility Units was based, in any way, on
hazards to public health or the
environment arising from emissions of
non-mercury HAP from coal-fired
Utility Units. Based on the information
before it at the time, EPA could not have
reasonably concluded that coal-fired
Utility Unit non-mercury HAP
emissions presented a hazard to public
health. In addition, as stated above, EPA
should not have considered
environmental effects in the December
2000 Regulatory Determination’s
consideration of whether it was
appropriate to regulate HAP emissions
from coal-fired Utility Units under
section 112.
(i) Non-Mercury Metallic HAP. In the
December 2000 Regulatory
Determination, EPA indicated that there
were a few metallic HAP (e.g.,
chromium and cadmium) which were of
potential concern for carcinogenic
effects, but stated that ‘‘the results of the
risk assessment (performed in
conjunction with the Utility Study)
indicate that cancer risks are not high’’.
(See 65 FR 79825, 79827.) The EPA
acknowledged, however, that the cancer
risks were not low enough to eliminate
those metals as a potential concern for
public health (Id.). This latter statement,
at least as it pertains to cadmium, is at
odds with the results of the risk
assessment set forth in the Utility Study
and discussed above. In the Utility
Study, EPA determined that there was
no maximum individual risk (MIR) for
cancer greater than 1 × 10 6 due to
inhalation of cadmium emissions from
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Utility Units. In the Proposed Rule, EPA
stated that although it recognized the
existence of uncertainties with regard to
the data and information obtained prior
to the December 2000 Regulatory
Determination regarding potential
hazards to public health resulting from
Utility Unit emissions of non-mercury
metallic HAP, the Agency believed that
the uncertainties associated with those
emissions were so great that it was not
appropriate to regulate them at that time
because they do not pose a hazard to
public health that warrants regulation.
(69 FR 4652, 4688, January 30, 2004).
The EPA continues to believe that had
it properly accounted for the
uncertainties regarding the data and
information on potential hazards to
public health resulting from Utility Unit
emissions of non-mercury metallic HAP
in making the December 2000
appropriate finding it would have
concluded that it was not appropriate to
regulate such emissions because they do
not cause a hazard to public health. The
EPA has not discovered any new
information on hazards to public health
arising from such emissions that
invalidates this conclusion, either
through its own efforts or in response to
the Proposed Rule.
(ii) Dioxins. In the December 2000
Regulatory Determination, EPA also
identified dioxins as being of potential
concern and indicated that they may be
evaluated further during the regulatory
development process. (See 65 FR 79825,
79827.) The EPA did not, however,
indicate that those concerns rose to a
level that warranted regulation of
dioxins. Thus, EPA did not conclude,
and could not have concluded, based on
the record before it at the time of the
December 2000 Regulatory
Determination that it was appropriate to
regulate coal-fired Utility Unit HAP
emissions under section 112 of the CAA
on the basis of dioxin emissions. In the
Proposed Rule EPA stated that while it
intended to continue to study dioxins in
the future, the Utility Study and the
information EPA had obtained since
finalizing the Utility Study revealed no
public health hazards reasonably
anticipated to occur as a result of
emissions of dioxins by Utility Units.
(See 69 FR 4652, 4688). As is the case
with non-mercury metallic HAP, EPA
has neither discovered information on
hazards to public health arising from
Utility Unit emissions of dioxins based
on its own efforts, nor received such
information in response to the Proposed
Rule. The EPA therefore concludes that
its appropriate finding in December
2000 lacked foundation because it could
not have reasonably concluded that the
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level of remaining utility dioxin
emissions results in hazards to public
health.
(iii) Acid Gases. In the December 2000
Regulatory Determination, EPA
identified emissions of hydrogen
chloride and hydrogen fluoride as being
of potential concern and indicated that
such emissions may be evaluated
further during the regulatory
development process. (See 65 FR 79825,
79827.) The EPA did not, however,
indicate that it believed that it was
appropriate to regulate such emissions,
under section 112 or otherwise. As
indicated in the Proposed Rule, EPA did
in fact further evaluate Utility Unit
emissions of hydrogen chloride and
hydrogen fluoride. (See 69 FR 4652,
4688, fn. 10; ‘‘Modeling results for
hydrogen chloride, hydrogen fluoride
and chlorine emissions from coal-fired
utility boilers’’, December 12, 2003,
OAR–2002–0056–0015). That modeling
indicates that individuals are not
exposed to acid gas emissions from
Utility Units at concentrations which
pose hazards to public health. EPA has
neither discovered information on
hazards to public health arising from
Utility Unit emissions of acid gases
based on its own efforts, nor received
such information in response to the
Proposed Rule. EPA therefore concludes
that its appropriate finding in December
2000 lacked foundation because the
level of remaining utility acid gas
emissions does not result in hazards to
public health.
For the reasons stated above, EPA
finds that it could not reasonably have
concluded that it was appropriate to
regulate coal-fired Utility Units under
section 112 due to emissions of nonmercury HAP based on the record before
it at the time of the December 2000
Regulatory Determination. The EPA
further finds that it has not itself
discovered any information which
would support the conclusion that it is
appropriate to regulate non-mercury
HAP emissions by coal-fired Utility
Units under section 112 subsequent to
the December 2000 Regulatory
Determination, nor has it received any
such information in response to the
January 2004 Proposed Rule, the March
2004 Supplemental Notice or the
December 2004 Notice of Data
Availability. Further, EPA has
concluded that it did not, and should
not, rely on potential environmental
effects alone in determining whether it
was appropriate to regulate coal-fired
Utility Units under section 112. The
EPA, therefore, finds that, based on the
record before it at the time, it was in
error in determining that it was
appropriate to regulate coal-fired Utility
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Unit HAP emissions under section 112
to the extent that the determination was
based in any way on the hazards to
public health of non-mercury HAP
emissions or on environmental effects
resulting from such emissions.
b. It Is Not Necessary to Regulate
Coal-fired Units on the Basis of NonMercury HAP Emissions. In determining
whether it is appropriate and necessary
to regulate Utility Unit HAP emissions
under section 112, the threshold
question is whether it is appropriate to
regulate such emissions at all. Where, as
here, EPA cannot reasonably conclude
that it is appropriate to regulate such
emissions, the Agency does not need to
resolve the question of whether it is
necessary to regulate such emissions
under section 112, or elsewhere. In any
event, even if EPA could have
reasonably concluded that it was
appropriate to regulate non-mercury
HAP emissions from coal-fired Utility
Units, it would not have been
reasonable for the Agency to find that it
was necessary to regulate such
emissions under section 112 since, as
discussed above, it should have realized
that there was an available alternative
mechanism, such as section 111, for
regulating such emissions had it been
appropriate to do so. See also Section
VII below.
B. Revision of the December 2000
Appropriate and Necessary Finding for
Oil-fired Units
1. It Is Not Appropriate and Necessary
To Regulate Oil-Fired Units on the Basis
of Nickel Emission
a. It Is Not Appropriate to Regulate
Oil-fired Units on the Basis of Nickel
Emissions. In finding that the regulation
of HAP emissions from oil-fired Utility
Units was appropriate and necessary in
its December 2000 Regulatory
Determination, EPA did not clearly
identify the basis for this finding
beyond stating that there remained
uncertainties regarding the extent of the
public health impact from HAP
emissions from oil-fired units and that
those uncertainties led the
Administrator to find that regulation of
HAP emission from such units under
section 112 is appropriate and
necessary. (See 65 FR 79825, 79830).
Table 1 in the 2000 determination does,
however, indicate that nickel is the
metallic HAP emitted in the largest
quantities by oil-fired Utility Units and
that some nickel compounds are
carcinogenic. (See 65 FR 79825, 79828).
It therefore appears that EPA’s finding
was based at least in part on its
concerns regarding perceived hazards to
public health arising from inhalation
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exposure to nickel emissions from oilfired Utility Units. This is consistent
with the Utility Study which, based on
very conservative assumptions
regarding the carcinogenicity of the
nickel emitted by such units, identifies
nickel as the HAP emitted by oil-fired
Utility Units which poses the highest
cancer maximum individual risk.
(Utility Study, Table 6–3, p. 6–8). The
Utility Study identifies 11 oil-fired
utility plants as having emissions
causing maximum individual risk of
cancer greater than 10¥6 based on
nickel emissions (Id.)
In the Proposed Rule, EPA stated that
it continued to believe that the record
supports a distinction between the
treatment of nickel emissions from oilfired Utility Units and other non-nickel
HAP emissions from such units. EPA
proposed to conclude that it was not
appropriate to regulate the non-Ni HAP.
EPA also proposed to treat nickel from
oil-fired units differently based on the
amount of nickel emitted annually and
the scope of adverse health effects (See
69 FR 4652, 4688). Based on its analysis
of new information obtained in response
to the Proposed Rule, EPA has
determined that the distinction between
nickel and the remaining HAP from oilfired units cannot be supported. EPA
finds that it is not appropriate to
regulate nickel emissions from oil-fired
Utility Units and that it is, therefore, not
appropriate to regulate oil-fired Utility
Units. This finding is based on the
following: (1) The significant reductions
in the total nationwide inventory of oilfired Utility Units; and (2) the changing
fuel mixtures being used at the
remaining units.
Nickel emissions from oil-fired Utility
Units have been substantially reduced
since the 1998 Utility Report to
Congress through a combination of unit
closures and fuel switching. The 11 oilfired plants identified in the Utility
Study as having emissions causing a
maximum individual risk of cancer
greater than 10¥6 based on nickel
emissions were comprised of 42
individual units. Of those 42 units, 12
units have permanently ceased
operation or are out of service. (OAR–
2002–0056–2046 at pp. 12–13; OAR–
2002–0056–5998). In addition, 6 of the
original 42 units have reported to the
U.S. Department of Energy (DOE) that
their fuel mix now includes natural gas.
Earlier reports did not show these units
as using natural gas as a fuel. (OAR–
2002–0056–5998). The use of natural
gas as a part of their fuel mix would
decrease the nickel emissions from
these 6 units. Similarly, another 5 units
report using a mix of natural gas and
distillate oil (rather than residual oil) in
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2003. (OAR–2002–0056–5998). Since
distillate oil contains less nickel than
the residual oil previously burned by
these units, it is reasonable to assume
that these units currently emit less
nickel than was previously the case.
Another 2 units now fire a residual oil/
natural gas mixture and have limited
their residual oil use through permit
restrictions to no greater than 10 percent
of the fuel consumption between April
1 and November 15, with natural gas
being used for at least 90 percent of total
fuel consumption. (OAR–2002–0056–
2046 at p. 13). Finally, five units have
effectively eliminated their nickel
emissions since the Utility Study by
switching to burning natural gas
exclusively. (OAR–2002–0056–2046 at
pp. 12–13; OAR–2002–0056–5998).
Taken as a whole, these changes mean
that 30 of the original 42 units identified
in the Utility Study have taken steps to
reduce or actually eliminate their nickel
emissions. Of the original 11 plants
identified in the Utility Study, only 2,
both in Hawaii, have units for which
actions that will result in reduced nickel
emissions do not appear to have been
taken. (OAR–2002–0056–6871) In
addition to the closure of the 12 units
identified as being of potential concern
in the Utility Study, there has been a
steady decrease in the number of oilfired Utility Units generally over the
past decade and this trend is likely to
continue. In fact, the latest DOE/EIA
projections (OAR–2002–0056–5999)
estimate no new utility oil-fired
generating capacity and decreasing
existing oil-fired generating capacity
through 2025, with an additional 29.2
gigawatts of combined oil- and natural
gas-fired existing capacity being retired
by 2025.
Based on the foregoing, EPA
concludes that it is not appropriate to
regulate oil-fired Utility Units under
section 112 because we do not
anticipate that the remaining level of
utility nickel emissions will result in
hazards to public health.
b. It Is Not Necessary to Regulate Oilfired Units on the Basis of Nickel
Emissions. Because EPA could not have
reasonably found that it was appropriate
to regulate nickel emissions from oilfired Utility Units based on the record
before it at the time of the December
2000 Regulatory Determination, it
should not have made a finding that it
was necessary to regulate such
emissions. Information obtained in the
course of the rulemaking since the
Proposed Rule has confirmed this
conclusion. In any event, even if EPA
could have reasonably concluded that it
was appropriate to regulate nickel
emissions from oil-fired Utility Units, it
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would not have been reasonable for the
Agency to find that it was necessary to
regulate such emissions under section
112 since, as discussed above, it should
have realized that there was an available
alternative mechanism, section 111, for
regulating such emissions had it been
appropriate to do so. See also Section
VII below.
2. It Is Not Appropriate and Necessary
To Regulate Oil-Fired Units on the Basis
of Non-Nickel HAP Emissions
a. It Is Not Appropriate to Regulate
Oil-fired Units on the Basis of Nonnickel HAP Emissions. As is the case
with emissions of nickel, the record
before EPA at the time of the December
2000 Regulatory Determination does not
reasonably support a finding that it is
appropriate to regulate emissions of any
other HAP from oil-fired Utility Units.
In the December 2000 Regulatory
Determination, EPA stated that there
remain uncertainties regarding the
extent of the public health impact from
HAP emissions from oil-fired Utility
Units and, on that basis, found that it
was appropriate and necessary to
regulate oil-fired Utility Units under
section 112. (See 65 FR 79825, 79830.)
The EPA neither identified the HAP
concerning which there were
uncertainties nor identified what those
uncertainties were. EPA has neither
discovered information on hazards to
public health arising from the remaining
non-nickel emissions of oil-fired Utility
Units, nor received such information in
response to the Proposed Rule. EPA
therefore concludes that its appropriate
finding in December 2000 lacked
foundation because, given the level of
remaining non-nickel HAP emissions
from Utility Units, the Agency did not
and does not have any information on
the hazards to public health reasonably
anticipated to occur. Indeed, the
uncertainties that exist with regard to
the data and information on these
emissions are so great that the Agency
has not identified any hazards to public
health.
b. It Is Not Necessary to Regulate Oilfired Units on the Basis of Non-nickel
HAP Emissions. Because EPA finds that
it is not appropriate to regulate oil-fired
Utility Units on the basis of non-nickel
HAP emissions, it also finds that it is
not necessary to regulate oil-fired Utility
Units on the basis of such emissions. In
any event, even if EPA could have
reasonably concluded that it was
appropriate to regulate non-nickel HAP
emissions from oil-fired Utility Units, it
would not have been reasonable for the
Agency to find that it was necessary to
regulate such emissions under section
112 since, as discussed above, it should
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have realized that there was an available
alternative mechanism, section 111, for
regulating such emissions had it been
appropriate to do so. See also Section
VII below.
V. Statutory and Regulatory Overview
of CAA Section 110(a)(2)(D) and
Summary of EPA’s Clean Air Interstate
Rule, Which Implements Section
110(a)(2)(D)
A. The Clean Air Interstate Rule and
Clean Air Act Section 110(a)(2)(D)
1. Background for Promulgation of the
Clean Air Interstate Rule
The Administrator signed the notice
of final rulemaking for the Clean Air
Interstate Rule (CAIR) on March 10,
2005. The background for CAIR is fully
described in the preambles to the final
rule, the notice of proposed rulemaking,
69 FR 4565 (January 30, 2004) and the
notice of supplemental rulemaking, 69
FR 12398 (March 16, 2004), and is
briefly summarized below.
a. PM 2.5 NAAQS, 8-hour Ozone
NAAQS, and the Nonattainment
Problems. By notice dated July 18, 1997,
we revised the NAAQS for particulate
matter to add new standards for fine
particles, using as the indicator particles
with aerodynamic diameters smaller
than a nominal 2.5 micrometers, termed
PM 2.5. 62 FR 38652. We established
health- and welfare-based (primary and
secondary) annual and 24-hour
standards for PM 2.5. The annual
standard is 15 micrograms per cubic
meter, based on the 3-year average of
annual mean PM 2.5 concentrations.
The 24-hour standard is a level of 65
micrograms per cubic meter, based on
the 3-year average of the annual 98th
percentile of 24-hour concentrations.
By a separate notice dated July 18,
1997, EPA also promulgated a revised
primary NAAQS for ozone (and an
identical secondary ozone NAAQS).
This revised NAAQS, termed the 8-hour
NAAQS, specified that the 3-year
average of the fourth highest daily
maximum 8-hour average ozone
concentration could not exceed 0.08
ppm. (See 40 CFR 50.10) In general, the
revised 8-hour standard is more
protective of public health and the
environment and more stringent than
the pre-existing 1-hour ozone standard.
Following promulgation of the 8-hour
ozone and the PM 2.5 NAAQS, EPA
anticipated that many areas of the
country, particularly in the eastern half
of the country, would have air quality
violating one or both of those NAAQS.34
34 Environmental Protection Agency, 1996.
Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment
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b. SO2 and NOX as Precursors for PM
2.5 and 8-hour Ozone. Fine particles are
emitted directly from emissions sources
and also can be formed in the
atmosphere through the reaction of
gaseous precursors. Sulfur dioxide and
nitrogen oxides are among the primary
precursors to the ‘‘secondary’’ formation
of PM 2.5.
Eight-hour ozone is exclusively a
secondary pollutant. Ozone is formed by
natural processes at high altitudes, in
the stratosphere, where it serves as an
effective shield against penetration of
harmful solar UV–B radiation to the
ground. The ozone present at ground
level as a principal component of
photochemical smog is formed in sunlit
conditions through atmospheric
reactions of two main classes of
precursor compounds: VOCs and NOX
(mainly NO and NO2). Nitrogen oxides
are emitted by motor vehicles, power
plants, and other combustion sources,
with lesser amounts from natural
processes including lightning and soils.
Both PM 2.5 and 8-hour ozone are
regional phenomena; that is each is
caused by emissions over a broad
geographic area. As a result, attainment
of the PM 2.5 NAAQS requires
reductions in SO2 and NOX over a
widespread area, and attainment of the
8-hour ozone NAAQS requires
reductions in NOX over a widespread
area. In the CAIR proposal, EPA
described the photochemistry and need
for regionwide reductions of precursors
of both pollutants in detail. See 69 FR
at 4572.
After promulgation of the PM 2.5
NAAQS, EPA was generally aware of
the role of SO2 and NOX emissions in
the PM 2.5 nonattainment problem, and,
therefore, of the need for widespread
reductions. Similarly, after
promulgation of the 8-hour ozone
NAAQS, EPA was aware of widespread
nonattainment, due to nonattainment of
the pre-existing, one-hour ozone
standard, and therefore of the need for
widespread NOX reductions.
c. Coal-fired Utility Units Emit A
Large Portion of SO2 and NOX
Emissions. Utility Units emit a large
portion of both the SO2 and NOX
inventory. Congress clearly recognized
that the utility industry emits a large
portion of the nation’s inventory of SO2
and NOX emissions when Congress
enacted the acid deposition provisions
in the 1990 Clean Air Act Amendments.
EPA noted in the CAIR proposal that
Utility Units—
of Scientific and Technical Information. OAQPS
Staff Paper. Research Triangle Park, NC: Office of
Air Quality Planning and Standards; Report No.
EPA–45/R–96–013.
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are the most significant source of SO2
emissions and a very substantial source of
NOX in the * * * region [proposed to be
affected by CAIR]. For example, EGUs
[Utility Units] emissions are projected to
represent approximately one-quarter (23
percent) of the total NOX emissions in 2010
and over two-thirds (67 percent) of the total
emissions in 2010 in the 28-State plus DC
region that [EPA proposed for] being
controlled for both SO2 and NOX after
application of current CAA controls.
(See 69 FR 4565, 4609–10 January 30, 2004.)
Beginning in the mid-1990s, EPA has
considered regional and national
strategies to reduce interstate transport
of SO2 and NOX. EPA described these
efforts in the CAIR notice of final
rulemaking.
3. Legal Authority
As noted above, in 1997, EPA revised
the NAAQS for PM to add new annual
average and 24-hour standards for fine
particles, using PM 2.5 as the indicator
(62 FR 38652). At the same time, EPA
issued its final action to revise the
NAAQS for ozone to establish new 8hour standards (62 FR 38856.)
Following promulgation of new
NAAQS, the CAA requires all areas,
regardless of their designation as
attainment, nonattainment, or
unclassifiable, to submit SIPs containing
provisions specified under section
110(a)(2). SIPs for nonattainment areas
are generally required to include
additional emissions controls providing
for attainment of the NAAQS. In
addition, under the authority of section
110(a)(2)(D) and other provisions of
section 110, EPA promulgated the NOX
SIP-Call in 1998. In that rulemaking,
EPA determined that 22 States and the
District of Columbia in the eastern half
of the country significantly contribute to
1-hour and 8-hour ozone nonattainment
problems in downwind States.35 This
rule required those jurisdictions to
revise their SIPs to include NOX control
measures to mitigate the significant
ozone transport. The EPA determined
the emissions reductions requirements
by projecting NOX emissions to 2007 for
all source categories and then reducing
those emissions through controls that
EPA determined to be highly costeffective. The affected States were
required to submit SIPs providing the
resulting amounts of emissions
reductions.
‘‘Finding of Significant Contribution and
Rulemaking for Certain States in the Ozone
Transport Assessment Group Region for Purposes of
Reducing Regional Transport of Ozone; Final Rule,’’
63 FR 57356 (October 27, 1998). The EPA also
published two Technical Amendments revising the
NOX SIP Call emission reduction requirements. (64
FR 26298; May 14, 1999 and 65 FR 11222; March
2, 2000).
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Under the NOX SIP-Call, States had
the flexibility to determine the mix of
controls to meet their emissions
reductions requirements. However, the
rule provided that if the SIP controls
Utility Units, then the SIP must
establish a budget, or cap, for Utility
Units. The EPA recommended that each
State authorize a trading program for
NOX emissions from Utility Units. We
developed a model cap and trade
program that States could voluntarily
choose to adopt, and all did so.
4. CAIR
In CAIR, EPA established SIP
requirements for the affected upwind
States under the authority of CAA
section 110(a)(2)(D) and other
provisions of section 110.36 Based on air
quality modeling analyses and cost
analyses, EPA concluded that SO2 and
NOX emissions in certain States in the
eastern part of the country, through the
phenomenon of air pollution transport,
contribute significantly to downwind
nonattainment of the PM 2.5 and 8-hour
ozone NAAQS. In CAIR, EPA required
SIP revisions in 28 States and the
District of Columbia to reduce SO2 and/
or NOX emissions, which are important
precursors of PM 2.5 (NOX and SO2) and
ozone (NOX). The affected States and
the District of Columbia are required to
adopt and submit the required SIP
revision with the necessary control
measures by 18 months from date of
signature of CAIR.
The 23 States along with the District
of Columbia that must reduce annual
NOX emissions for the purposes of the
PM 2.5 NAAQS are: Alabama, Florida,
Georgia, Illinois, Indiana, Iowa,
Kentucky, Louisiana, Maryland,
Michigan, Minnesota, Mississippi,
Missouri, New York, North Carolina,
Ohio, Pennsylvania, South Carolina,
Tennessee, Texas, Virginia, West
Virginia, and Wisconsin.
The 25 States along with the District
of Columbia that must reduce NOX
emissions for the purposes of the 8-hour
ozone NAAQS are: Alabama, Arkansas,
Connecticut, Delaware, Florida, Illinois,
Indiana, Iowa, Kentucky, Louisiana,
Maryland, Massachusetts, Michigan,
Mississippi, Missouri, New Jersey, New
York, North Carolina, Ohio,
Pennsylvania, South Carolina,
36 See ‘‘Rule to Reduce Interstate Transport of
Fine Particulate Matter and Ozone (Interstate Air
Quality Rule); Proposed Rule,’’ 69 FR 4566 (January
30, 2004); ‘‘Supplemental Proposal for the Rule to
Reduce Interstate Transport of Fine Particulate
Matter and Ozone (Clean Air Interstate Rule);
Proposed Rule,’’ 69 FR 32684 (June 10, 2004); and
the final rule ‘‘Rule to Reduce Interstate Transport
of Fine Particulate Matter and Ozone (Clean Air
Interstate Rule),’’ which was recently issued.
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Tennessee, Virginia, West Virginia, and
Wisconsin.
The emissions reductions
requirements are based on controls that
EPA determined to be highly costeffective for Utility Units. However,
States have the flexibility to choose the
measures to adopt to achieve the
specified emissions reductions. If the
State chooses to control Utility Units,
then it must establish a budget—that is,
an emissions cap—for those sources.
CAIR defines the Utility Units budgets
for each affected State. Due to feasibility
constraints, EPA is requiring that
emissions reductions be implemented in
two phases, with the first phase in 2009
(for NOX) and 2010 (for SO2), and the
second phase in 2015.
As noted above, under the CAIR, each
State may independently determine
which emissions sources to subject to
controls, and which control measures to
adopt. The EPA’s analysis indicates that
emissions reductions from Utility Units
are highly cost-effective, and in the
CAIR, EPA encouraged States to adopt
controls for Utility Units. States that do
so must place an enforceable limit, or
cap, on Utility Unit’s emissions. The
EPA calculated the amount of each
State’s Utility Unit emissions cap, or
budget, based on reductions that EPA
determined are highly cost-effective.
States may allow their Utility Units to
participate in an EPA-administered capand-trade program as a way to reduce
the cost of compliance, and to provide
compliance flexibility. The EPA will
administer these programs, which will
be governed by rules provided by EPA
that States may adopt or incorporate by
reference.
EPA estimated that the CAIR would
reduce annual SO2 emissions by 3.6
million tons by 2010 and by 4.0 million
tons by 2015; and would reduce annual
NOX emissions by 1.3 million tons by
2010 and by 1.5 million tons by 2015.
If all the affected States choose to
achieve these reductions through Utility
Unit controls, then Utility Unit
emissions in the affected States would
be capped at 3.7 million tons in 2010
and 2.6 million tons in 2015; and Utility
Unit annual NOX emissions would be
capped at 1.5 million tons in 2010 and
1.3 million tons in 2015. The EPA
estimated that the required SO2 and
NOX emissions reductions would, by
themselves, bring into attainment 52 of
the 80 counties that are otherwise
expected to be in nonattainment for PM
2.5 in 2010, and 57 of the 75 counties
that are otherwise expected to be in
nonattainment for PM 2.5 in 2015. The
EPA further estimated that the required
NOX emissions reductions would, by
themselves, bring into attainment 3 of
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the 40 counties that are otherwise
expected to be in nonattainment for 8hour ozone in 2010, and 6 of the 22
counties that are expected to be in
nonattainment for 8-hour ozone in 2015.
In addition, the CAIR would improve
PM 2.5 and 8-hour ozone air quality in
the areas that would remain
nonattainment for those two NAAQS
after implementation of CAIR. Because
of the CAIR, the States with those
remaining nonattainment areas will find
it less burdensome and less expensive to
reach attainment by adopting additional
local controls. The CAIR would also
reduce PM 2.5 and 8-hour ozone levels
in attainment areas.
C. Utility Mercury Emission Reductions
Expected as Co-Benefits From CAIR
The final CAIR requires annual SO2
and NOX reductions in 23 States and the
District of Columbia, and also requires
ozone season NOX reductions in 25
States and the District of Columbia.
Many of the CAIR States are affected by
both the annual SO2 and NOX reduction
requirements and the ozone season NOX
requirements. CAIR was designed to
achieve significant emissions reductions
in a highly cost-effective manner to
reduce the transport of fine particles
that have been found to contribute to
nonattainment. EPA analysis has found
that the most efficient method to
achieve the emissions reduction targets
is through a cap-and-trade system on the
power sector that States have the option
of adopting. In fact, States may choose
not to participate in the optional capand-trade program and may choose to
obtain equivalent emissions reductions
from other sectors. However, EPA
believes that a region-wide cap-andtrade system for the power sector is the
best approach for reducing emissions.
The power sector accounted for 67
percent of nationwide SO2 emissions
and 22 percent of nationwide NOX
emissions in 2002.
EPA expects that States will choose to
implement the final CAIR program in
much the same way they chose to
implement their requirements under the
NOX SIP Call. As noted above, under the
NOX SIP Call, EPA gave States ozone
season NOX reduction requirements and
the option of participating in a cap-andtrade program. In the final rulemaking,
EPA analysis indicated that the most
efficient method to achieve reductions
targets would be through a cap-andtrade program. Each affected State, in its
approved SIP, chose to control
emissions from Utility Units and to
participate in the cap-and-trade
program.
Therefore, EPA anticipates that States
will comply with CAIR by controlling
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Utility Unit SO2 and NOX emissions.
Further, EPA anticipates that States will
implement those reductions through the
cap-and-trade approach, since the
power sector represents the majority of
national SO2 emissions and the majority
of stationary NOX emissions, and
represent highly cost-effective SO2 and
NOX sources to reduce. For further
discussion of cost-effectiveness, see
section IV of CAIR notice of final
rulemaking. EPA modeled a region-wide
cap and trade system on the power
sector for the States covered by CAIR,
and this modeling projected that most
reductions in NOX and SO2 would come
through the installation of scrubbers, for
SO2 control, and selective catalytic
reduction for NOX control (see
Regulatory Impact Assessment for CAIR
and CAMR in docket). Scrubbers and
SCR are proven technologies for
controlling SO2 and NOX emissions and
sources installed them to comply with
the Acid Rain trading program and the
NOX SIP Call trading program. EPA’s
modeling also projected that the
installation of these controls would
achieve Hg emission reductions as a cobenefit.
EPA projections of Hg co-benefits are
based on 1999 Hg ICR emission test data
and other more recent testing conducted
by EPA, DOE, and industry participants.
(For further discussion see Control of
Emissions from Coal-Fired Electric
Utility Boilers: An Update, EPA/Office
of Research and Development, March
2005, in the docket). That emission
testing has provided a better
understanding of Hg emissions and their
capture in pollution control devices.
Mercury speciates into three basic
forms, ionic, elemental, and particulate
(particulate represents a small portion of
total emissions). In general, ionic Hg
compounds are more readily absorbed
than elemental Hg and the presence of
chlorine compounds (which tend to be
higher for bituminous coals) results in
increased ionic Hg. Overall the 1999 Hg
ICR data revealed higher levels of Hg
capture for bituminous coal-fired plants
as compared to subbituminous and
lignite coal-fired plants and a significant
capture of ionic Hg in wet SO2
scrubbers. Additional Hg testing
indicates that for bituminous coals SCR
has the ability to convert elemental Hg
to ionic Hg and thus allow easier
capture in a wet scrubber. This
understanding of Hg capture was
incorporated into EPA modeling
assumptions and is the basis for our
projections of Hg co-benefits from
installation of scrubbers and SCR under
CAIR.
The final CAIR requires annual SO2
and NOX reductions in two phases, the
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first phase in 2010 and the second phase
in 2015. EPA modeling of CAIR
projected that most reductions in NOX
and SO2 would come through the
installation of scrubbers and SCR, and
that the installation of these controls
would also achieve Hg emission
reductions as a co-benefit. Given the
history of the Acid Rain and NOX SIP
Call trading programs, and our
experience with those programs, we
anticipate that reductions in SO2
emissions will begin to occur before
2010 because of the ability to bank SO2
emission allowances, though to some
degree this is limited by the time and
resources needed to install control
technologies. Companies have an
incentive to achieve greater SO2
reductions than needed to meet the
current Acid Rain cap because the
excess allowances they generate can be
‘‘banked’’ and either later sold on the
market or used to demonstrate
compliance in 2010 and beyond at the
facility that generated the excess
allowances. Based on the analysis of
CAIR, EPA’s modeling projects that Hg
emissions would be 38.0 tons (12 tons
of non-elemental Hg) in 2010, 34.4 tons
in 2015 (10 tons of non-elemental Hg),
and 34.0 tons in 2020 (9 tons of nonelemental Hg), about a 20 and 30
percent reduction (in 2010 and 2015,
respectively) from a 1999 baseline of 48
tons.37 For further discussion of EPA
modeling results and projected
emissions see Chapter 8 of the
Regulatory Impact Assessment.38
37 As
discussed in the TSD, the emissions of
reactive gaseous Hg and particle-bound Hg are most
important for local and regional Hg deposition
purposes, since they are substantially more likely
to be deposited than elemental Hg. CAIR and CAMR
will significantly reduce reactive gaseous Hg and
particle bound Hg from 2001 levels. CAIR will
reduce the levels from approximately 22 tons to 9
tons. CAMR will reduce this level further to
between 7 and 9 tons, for a total reduction (with
CAIR) of roughly 70 percent.
38 In addition to CAIR, EPA recently promulgated
another rule for Utility Units. Specifically, on
March 15, 2005, the Administrator signed a final
rulemaking called the Clean Air Mercury Rule
(‘‘CAMR’’) pursuant to CAA section 111. This rule
sets standards of performance for Hg emitted from
both new and existing coal-fired Utility Units. Like
CAIR, the rule establishes a cap-and-trade
mechanism by which Hg emissions from new and
existing coal-fired Utility Units are capped at
specified, nation-wide levels. The first phase cap of
38 tons per year (‘‘tpy’’) becomes effective in 2010
and the second phase cap of 15 tpy becomes
effective in 2018. Facilities must demonstrate
compliance with the standards of performance by
holding one ‘‘allowance’’ for each ounce (oz) of Hg
emitted in any given year. Allowances are readily
transferrable among all regulated units. As
explained in section VI below, the level of Hg
emissions remaining after implementation of CAMR
do not result in hazards to public health.
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VI. Scientific and Technical
Background and EPA’S Conclusions
Concerning the Level of Utility
Attributable Mercury Emissions After
CAIR and CAMR
In this section, we explain why we
believe the level of utility attributable
Hg emissions remaining after imposition
of CAIR, and independently, CAMR,
will not result in hazards to public
health. The issue of whether utility Hg
emissions remaining after CAIR, and
independently CAMR, result in hazards
to public health is directly related to our
conclusion, stated above in Section
IV.A, that we cannot find it appropriate
and necessary to regulate coal-fired
Utility Units under section 112 on the
basis of Hg emissions. This section
includes an overview of the scientific
and technical information relevant to
evaluating utility Hg emissions and the
public health impacts associated with
such emissions. Below, we provide
general background concerning the
health impacts of methylmercury; the
predominant exposure pathway by
which humans are affected by
methylmercury, which is by ingestion of
fish containing methylmercury; and
EPA’s methodology for determining the
impacts of utility Hg emissions on the
amount of methylmercury found in fish
tissue. This section also includes a
summary of our conclusions, including
that utility Hg emissions remaining after
implementation of CAIR, and
independently CAMR, are not
reasonably anticipated to result in
hazards to public health.
A. Human Health Impacts of
Methylmercury Exposure and Amounts
of Hg Emissions
Hg is a persistent, bioaccumulative
toxic metal that is emitted from power
plants in three forms: Elemental
mercury (Hg\0\), oxidized mercury
(Hg\++\) compounds, as well as
particle-bound mercury. Methylmercury
is formed by microbial action in the top
layers of sediment and soils, after Hg
has precipitated from the air and
deposited into water bodies or land.
Once formed, methylmercury is taken
up by aquatic organisms and
bioaccumulates up the aquatic food
web. Larger predatory fish may have
methylmercury concentrations many
times that of the water body in which
they live.
While Hg is toxic to humans when it
is inhaled or ingested, we focus on oral
exposure of methylmercury in this
rulemaking, as it is the route of primary
interest for human exposures in the U.S.
Methylmercury is a well-established
human neurotoxicant. Methylmercury
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that is ingested by humans is readily
absorbed from the gastrointestinal tract
and can cause effects in several organ
systems. The best studied effect of low
level exposure is the ability of
methylmercury to cause subtle, yet
potentially important
neurodevelopmental effects. Of
particular concern is the effect of
methylmercury on the developing fetal
nervous system exposed in utero from
maternal fish ingestion. Large
prospective epidemiological studies
have reported that prenatal
methylmercury from environmental
exposures has been associated with poor
performance on neurobehavioral tests in
children. These include tests that
measure attention, visual-spatial ability,
verbal memory, language skills, and fine
motor function. These studies have been
thoroughly reviewed, singly and as part
of review groups, by many expert
scientists, including a panel of the
National Research Council (NRC) of the
National Academy of Sciences (NAS).39
While important, the weight of evidence
for cardiovascular effects is not as strong
as it is for childhood neurological
effects and the state of the science is
still being evaluated. However, some
recent epidemiological studies in men
suggest that methylmercury is
associated with a higher risk of acute
myocardial infaraction, coronary heart
disease and cardiovascular disease in
some populations. Other recent studies
have not observed this association. The
findings to date and the plausible
biological mechanisms warrant
additional research in this area (Stern
2005; Chan and Egeland 2004). There is
some recent evidence that
methylmercury may result in genotoxic
or immunotoxic effects. Overall, there is
a relatively small body of evidence from
human studies that suggests exposure to
methylmercury can result in
immunotoxic effects and the NRC
concluded that evidence that human
exposure caused genetic damage is
inconclusive. There are insufficient
human data to evaluate whether these
effects are consistent with levels in the
U.S. population. Because the developing
fetus may be the most sensitive to the
effects from methylmercury, women of
39 Studies investigating the relationship between
methylmercury and cardiovascular effects have
reached different conclusions. Some recent
epidemiological studies of men suggest that
methylmercury is associated with a higher risk of
acute myocardial infarction, coronary heart disease
and cardiovascular disease in some populations.
Other research with less corroboration suggest that
reproductive, renal, and hematological impacts may
be of concern. There are insufficient human data to
evalaute whether these effects are consistent with
levels in the U.S. population. See RIA for CAMR
chapter 2.
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child-bearing age are regarded as the
population of greatest interest when
assessing methylmercury exposure.
The predominant pathway of Hg
exposure to both humans and wildlife is
consumption of fish. Critical elements
in estimating methylmercury exposure
and risk from fish consumption include
the concentrations of methylmercury in
the fish consumed, the quantity of fish
consumed,40 and how frequently the
fish is consumed. There is a great deal
of variability among individuals in fish
consumption rates. However, our
analysis indicates that the typical U.S.
consumer eating moderate amounts of a
wide variety of low-mercury fish from
restaurants and grocery stores is not
expected to ingest harmful levels of
methylmercury from fish. Those who
regularly and frequently consume large
amounts of fish, or fish with higher
levels of methylmercury, are more
exposed. The EPA and Food and Drug
Administration jointly, as well as states,
have issued fish consumption advisories
to inform people of ways to reduce
exposure to methylmercury from fish.
As part of its long term U.S.
population surveillance, the U.S.
Centers for Disease Control (CDC)
assessed Hg concentrations in blood of
over 3,600 women of child-bearing age
under the National Health and Nutrition
Examination Survey (NHANES). A
recent analysis of these data reported
that about 6 percent of these women of
child-bearing age have levels of Hg in
their blood that are at or above the U.S.
EPA’s RfD, described below. The CDC
also surveyed the same group of women
about their eating habits. An analysis of
1500 of these women showed that Hg
blood levels were higher in the women
who reported eating three or more
servings of fish in the month before they
were tested. It is reasonable to conclude
that methylmercury contained in
seafood may be responsible for elevated
levels of Hg in U.S. women of childbearing age.41
As described below, the analysis
supporting today’s action focuses on
assessing exposure from freshwater fish
caught and consumed by recreational
and subsistence anglers because
available information indicate that U.S.
utility Hg emissions may affect the
methylmercury concentrations in these
fish. EPA also considered the following
fish consumption pathways:
Consumption from commercial sources
(including saltwater and freshwater fish
from domestic and foreign producers);
40 A precise estimate of methylmercury exposure
depends on quantity of fish consumed as a function
of an individual’s body weight.
41 289 JAMA 1667 (April 2, 2003).
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consumption of recreationally caught
marine fish, consumption of
recreationally caught estuarine fish; and
consumption of commercial fish raised
at fish farms (aquaculture). For a
number of reasons, as explained in the
TSD, current information does not
suggest that these latter pathways
present meaningful risks of ingestion of
utility-attributable methylmercury.
The EPA’s 1997 Mercury Study
Report to Congress suggests a plausible
link between anthropogenic releases of
Hg from industrial and combustion
sources in the U.S. and methylmercury
in fish in the U.S. However, other
sources of Hg emissions, including Hg
from natural sources (such as volcanos)
and anthropogenic emissions in other
countries, contribute to the levels of
methylmercury observed in fish in the
U.S.42 Our current understanding of the
global Hg cycle and the impact of the
anthropogenic sources allow us to make
estimates on a global, continental, or
regional scale of their relative
importance. It is more difficult to make
accurate predictions of the fluxes on a
local scale given our current
understanding.
We recognize that it is also difficult to
quantify with precision how a specific
change in air deposition of Hg leads to
a change in fish tissue levels. We further
recognize that the relationship between
the amount of Hg emissions reduced
and the attendant reduction in
methlymercury fish concentrations
depends upon the specific
characteristics of the waterbody at issue.
Nevertheless, science continues to
evolve and EPA has made substantial
progress in developing methods for
assessing the amount of methylmercury
in fish tissues that may be traced to
emissions from coal-fired U.S. Utility
Units. We describe our methodology
below and why this methodology is
sufficient to support today’s action.
As discussed above, we are focusing
on consumption of self-caught,
freshwater fish. We estimate that there
42 Recent Hg estimates (which are highly
uncertain) of annual total global emissions from all
sources (natural and anthropogenic) are about 5,000
to 5,500 tons per year (tpy). Of this total, about
1,000 tpy are estimated to be natural emissions and
about 2,000 tpy are estimated to be contributions
through the natural global cycle of re-emissions of
Hg associated with past natural releases and
anthropogenic activity. Current anthropogenic
emissions account for the remaining 2,000 tpy.
Given the global estimates noted above, U.S.
anthropogenic Hg emissions are estimated to
account for roughly 3 percent of the global total,
and U.S. utilities are estimated to account for about
1 percent of total global emissions. Deposition from
U.S. utilities is described in greater detail below.
Utility RTC at 7–1 to 7–2; Mercury NPR, 69 FR
4657–58 (January 20, 2004); RIA for CAMR chapters
5–6.
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are approximately 27.9 million
recreational freshwater fishers in the
U.S. population, including fishers who
do not eat (e.g., release) their catch.
Based on application of a ‘‘consuming’’
factor and a ‘‘sharing’’ factor to the
estimate of recreational fishers, as
discussed further in the RIA to CAMR,
we estimate that approximately 58.6
million individuals in the U.S.
population consume recreationallycaught freshwater fish. Of these
individuals, we estimate that
approximately 7.5 to 10.5 million are
women of child-bearing age (that is, 15–
44 years old), about 500,000 of whom
are expected to give birth in any one
year. We estimate that the mean
recreational freshwater fish
consumption rate for these women is 8
grams/day, and the 95th percentile
recreational freshwater fish
consumption rate is 25 grams/day. A
subset of recreational freshwater fish
consumers may consume at higher
levels, as discussed below. In addition,
subsistence fishers and fishers in certain
ethnic groups are expected to have
generally higher fish consumption rates
than consumers of recreational
freshwater fish. These sub-populations
are discussed below.
B. The Methylmercury Reference Dose
EPA generally quantifies risk of
adverse health effects other than cancer
by calculating a reference value (RfV). In
general, an RfV is an estimation of an
exposure that is likely to be without an
appreciable risk of adverse effects over
a lifetime. See https://www.epa.gov/iris/
gloss8.htm. RfVs for exposure by
ingestion are called reference doses
(RfD).
The EPA defines an RfD as ‘‘an
estimate (with uncertainty spanning
perhaps an order of magnitude) of a
daily oral exposure to the human
population (including sensitive
subgroups) that is likely to be without
an appreciable risk of deleterious effects
during a lifetime. It can be derived from
a NOAEL (no observed adverse effect
level), LOAEL (lowest observed adverse
effect level), or benchmark dose, with
uncertainty factors generally applied to
reflect limitations of the data used.’’ See
https://www.epa.gov/iris/gloss8.htm.
As stated above, an RfD is derived by
choosing a point of departure from
animal or human data. This can be a
NOAEL or LOAEL, either of which may
be defined by applying statistical tests
and scientific judgment to the data.
When the data are sufficient, one can
apply a mathematical model to obtain a
benchmark dose (BMD). The BMD is the
dose at which a particular level of
response (i.e., the benchmark response,
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or BMR) for some outcome of concern
is found to occur. One can then derive
a BMD lower confidence limit (BMDL),
which is a statistical lower bound on the
chosen BMD, an exposure expected to
produce a specified effect in some
defined percentage of a test population.
The point of departure (again,
NOAEL, LOAEL, or BMDL) is divided
by uncertainty/variability factors to
arrive at the RfD. The uncertainty
factors are intended to account for
variability and uncertainty in the data.
The size of an uncertainty/variability
factor is determined by the adequacy or
limitations of the data and is typically
either 10 or 3 for each type of variabilty.
For example, uncertainty factors may be
employed for extrapolating from
animals to humans, variability in
human susceptibility (sensitive
populations), and extrapolating from
subchronic to chronic exposures. The
resulting RfD is believed to be the
amount of a chemical which, when
ingested daily over a lifetime, is likely
to be without an appreciable risk of
deleterious effects to humans, including
sensitive subpopulations.
In 2001, EPA published an RfD for
methylmercury that is based on a BMD
approach. This quantitative risk
estimate was based on data from
developmental neurotoxicity studies
mentioned above; specifically, deficits
in tests associated with ability to learn
and process information. EPA applied
an uncertainty/variability factor of 10 to
the point of departure (BMDL) to derive
the RfD. EPA’s RfD for methylmercury
is 0.1 µg/kg bw/day, which is 0.1
micrograms of Hg per day for each
kilogram of a person’s body weight.
As noted in the Hg Proposal, at the
direction of Congress, EPA funded the
NAS to perform an independent
evaluation of the available data related
to the health impacts of methylmercury
and provide recommendations for EPA’s
RfD. The NAS/National Research
Council (NRC) conducted an 18-month
study of the available data on the health
effects of methylmercury. The review by
the NAS, published in July 2000,
concluded that the neurodevelopmental effects are the most
sensitive and well-documented effects
of methylmercury exposure. The NRC
advised revising the basis of the RfD,
which used data from a short-term
exposure in Iraq, to incorporate new
studies on children exposed in utero
when their mothers ate seafood
containing Hg. EPA subsequently
established a reference dose of 0.0001
mg/kg bw/day. NAS determined that
EPA’s RfD ‘‘is a scientifically justified
level for the protection of public
health.’’
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The methylmercury RfD is further
described in the RIA, chapter 2 and in
other EPA documents (IRIS, U.S. EPA
2001; Water Quality Criteria for the
Protection of Human Health:
Methylmercury, EPA–823–R–01–001).
Briefly, EPA used as the point of
departure BMDLs for multiple
endpoints from the three studies of in
utero methylmercury exposure and
effects. These were conducted in the
Faroes and Seychelles Islands and in
New Zealand.43 All of the endpoints
were children’s scores on
neuropsychological tests. Consistent
with NRC recommendations, an
uncertainty/variability factor of 10 was
used to account for pharmacokinetic
and pharmacodynamic variability in the
human population. In the EPA
documents, one data set from the Faroes
(Boston Naming Test, full cohort) is
displayed for all calculations as an
example of the multiple BMDLs which
serve as the basis for the RfD.
In determining the RfD for
methylmercury, EPA said that the ‘‘RfD
can be considered a threshold for a
population at which it is unlikely that
adverse effects will be observed’’ (Water
Quality Criteria for the Protection of
Human Health: Methylmercury, EPA–
823–R–01–001). The RfD was calculated
to be a level ‘‘likely to be without an
appreciable risk,’’ of ‘‘deleterious
effects’’ for all populations, including
sensitive subgroups. EPA does not
further quantify the degree of risk which
43 More specifically, the subjects of the Seychelles
longitudinal prospective study were 779 motherinfant pairs from a fish-eating population (Myers et
al., 1995a–c, 1997; Davidson et al., 1995, 1998).
Infants were followed from birth to 5.5 years of age,
and assessed at various ages on a number of
standardized neuropsychological endpoints. The
independent variable was maternal-hair Hg levels.
The Faroe Islands study was a longitudinal study
of about 900 mother-infant pairs (Grandjean et al.,
1997). The main independent variable was cordblood Hg; maternal-hair Hg was also measured. At
7 years of age, children were tested on a variety of
tasks designed to assess function in specific
behavioral domains. The New Zealand study was a
prospective study in which 38 children of mothers
with hair Hg levels during pregnancy greater than
6 ppm were matched with children whose mothers
had lower hair Hg levels (Kjellstrom et al., 1989,
1986). At 6 years of age, a total of 237 children were
assessed on a number of neuropsychological
endpoints similar to those used in the Seychelles
study (Kjellstrom et al., 1989). The Seychelles study
yielded no statistically significant evidence of
impairment related to in utero methylmercury
exposure, whereas the other two studies found
dose-related effects on a number of
neuropsychological endpoints. In the assessment
described here, an integrative analysis of all three
studies was relied upon in setting the point of
departure for derivation of the RfD. As noted by
NRC in reference to data from the Seychelles, Faroe
Islands, and New Zealand, ‘‘because those data are
epidemiological, and exposure is measured on a
continuous scale, there is no generally accepted
procedure for determining a dose at which no
adverse effects occur.’’ (NRC 2000)
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16013
would be expected for exposures at or
above the methylmercury RfD. This is
the case for all of EPA’s RfDs.
Additional regulatory values support a
similar threshold approach for
describing risks to methylmercury
exposure. For example, the World
Health Organization sets the level at
0.23 µg/kg/day; Health Canada sets the
level at 0.2 µg/kg/day; and the Agency
for Toxic Substances and Disease
Registry (ATSDR) sets a value of 0.3 µg/
kg/day.
EPA has established the RfD at a level
such that exposures at or below the RfD
are unlikely to be associated with
appreciable risk of deleterious effects. It
is important to note, however, that the
RfD does not define an exposure level
corresponding to zero risk; exposure
near or below the RfD could pose a very
low level of risk which EPA deems to
be non-appreciable. It is also important
to note that the RfD does not define a
bright line, above which individuals are
at risk of adverse effects.
Further, in EPA’s 1989 Residual Risk
Report to Congress, we stated:
It should be noted that exposures above an
RfD or RfC do not necessarily imply
unacceptable risk or that adverse health
effects are expected. Because of the inherent
conservatism of the RfC/RfD methodology,
the significance of exceedances must be
evaluated on a case-by-case basis,
considering such factors as the confidence
level of the assessment, the size of UF used,
the slope of the dose-response curve, the
magnitude of the exceedance, and the
number or types of people exposed at various
levels above the RfD or RfC.44
44 U.S. Environmental Protection Agency. 1989.
Risk Assessment Guidance for Superfund: Volume
I. Human Health Evaluation Manual (Part A). Office
of Emergency and Remedial Response. Washington,
DC, EPA/541/1–89/002, at 52–53 https://
www.epa.gov/oswer/riskassessment/ragsa/pdf/
ch8.pdf (Residual Risk Report). The Residual Risk
Report further stated:
It is expected that an HI (i.e., hazard index (HI)),
which is the sum of more than one hazard quotient
for multiple substances and/or multiple exposure
pathways) less than 1 that is derived using target
organ specific hazard quotients would ordinarily be
considered acceptable. If the HI is greater than 1,
then the amount by which the HI is greater than 1,
the uncertainty in the HI, the slope of the doseresponse curve, and a consideration of the number
of people exposed would be considered in
determining whether the risk is acceptable.
Evaluation of the acceptable value for an HQ (i.e.,
hazard quotient (HQ), which is the ratio of the
exposure level to a reference exposure level (e.g.,
RfD)) or an HI of 1 also would consider the values
of UFs (i.e., uncertainty/variability factor (UF)),
which is a default factor—generally 10-fold—used
in operationally deriving the RfD or RfC from
experimental data) and the confidence in the RfC
that are used in the calculation of the HI. In general,
it is considered that each UF is somewhat
conservative; because all factors are not likely to
simultaneously be at their most extreme (highest)
value, a combination of several factors can lead to
substantial conservatism in the final value. Larger
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C. Methylmercury Levels in Fish and the
Methylmercury Water Quality Criterion
As noted above, the most important
pathway of exposure to Hg for humans
is through the consumption of fish and
seafood. These include saltwater fish
such as tile fish, shark, and swordfish,
which are most often caught
commercially. They also include
freshwater fish such as bass, perch, and
walleye, which are often caught
recreationally, commercially, or for
personal consumption or distribution.
Generally shellfish have lower levels of
methylmercury than do finfish. The
levels of Hg in fish and shellfish are
variable, with mean levels ranging from
non-detectable to 1.45 mg/kg,
depending on species. See FDA Mercury
Levels in Commercial Fish and Shellfish
(https://www.cfsan.fda.gov/~frf/seamehg.html).
Methylmercury exposure is a function
of how much fish is eaten (on a
bodyweight basis), how frequently fish
is eaten, and the methylmercury
concentration in the fish. As a result,
estimates of the amount and type of fish
consumption are important to assessing
the impacts of methylmercury attributed
to coal-fired Utility Units on public
health.
Hg is emitted from powerplants in
three forms: Elemental Hg, reactive
(oxidized) Hg, and particulate Hg. Most
of the local and regional Hg deposition
is associated with the emissions of
reactive Hg. For this reason, the
magnitude of reactive Hg emission from
powerplants is critical to Hg deposition
in the United States. As noted above,
FGD and SCR control technologies are
most effective in controlling reactive Hg
emissions. As indicated by Table VI–2,
roughly 90 percent of the Hg reductions
under CAIR in 2020 are reactive Hg. As
a result, the SO2 and NOX limits
established by CAIR yield significant
reductions (roughly 70 percent) in
reactive Hg emissions from
powerplants.
Americans eat fish from a variety of
sources. An individual’s fish diet can be
composed of commercial fish and
shellfish (both imported and domestic),
fish from aquaculture (or farm raised
fish for commercial sale), and fish from
non-commercial sources (e.g.,
recreationally caught fish, fish caught to
composite UF lead to more conservative RfC.
Conversely, lower composite UF are less
conservative and usually indicate a higher level of
confidence in the RfC. Intermediate UF values or a
mixture of high and low UF would require an
examination of the relative contribution of various
chemicals to the HI. Thus, an HI or HQ greater than
1 may be considered acceptable based on
consideration of other factors.
Id. at 125.
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meet dietary needs, and/or fish caught
for cultural or traditional reasons).
These fish may come from marine,
estuarine, or freshwater sources.
Using the 2001 RfD and information
on Hg exposure routes, EPA published
a recommended ambient water quality
criterion for the states’ and tribes’ use in
setting water quality standards for U.S.
waters (freshwater and estuarine) that
are designed to protect human health.
EPA issued the methylmercury water
quality criterion in 2001. Water Quality
Criterion for the Protection of Human
Health: Methylmercury. EPA–823–R–
01–001. Office of Science and
Technology, Office of Water, USEPA,
Washington, DC, USEPA 2001) Because
of the wide variability in
methylmercury bioaccumulation among
waterbodies, EPA set the criterion as a
fish tissue level rather than as an
ambient water concentration. The
criterion is 0.3 mg/kg (milligram
methylmercury per kilogram of wetweight fish tissue). The criterion is a
risk assessment number that states and
authorized tribes may use in their
programs for protection of designated
uses.
The Clean Water Act (CWA) and
EPA’s regulations specify requirements
for adoption of water quality criteria.
States and authorized tribes must adopt
water quality criteria that protect
designated uses. See CWA section
303(c)(2)(A). Water quality criteria must
be based on a sound scientific rationale
and must contain sufficient parameters
or components to protect the designated
uses. See 40 CFR 131.11. States and
authorized tribes must adopt criteria for
all toxic pollutants where EPA has
established ambient water quality
criteria where the discharge or presence
of these pollutants could reasonably
interfere with the designated uses. See
CWA Section 303(c)(2)(B). EPA issued
guidance on how states and authorized
tribes may comply with section
303(c)(2)(B) which is now contained in
the Water Quality Standards Handbook:
Second Edition (EPA, 1994). States and
authorized tribes that decide to use the
recommended methylmercury criterion
as the basis for new or revised
methylmercury water quality standards
have the option of adopting the criterion
as a fish tissue concentration into their
water quality standards, adjusting the
criterion to account for state or local
exposure, or adopting it as a traditional
water column concentration. States and
authorized tribes remain free not to use
EPA’s current recommendations,
provided that their new or revised water
quality criteria for methylmercury
protect the designated uses and are
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based on a scientifically defensible
methodology.
The methylmercury water quality
criterion incorporated the RfD, data on
freshwater and estuarine finfish and
shellfish consumption for the target
population (the adult general
population), and information on
exposure to methylmercury as a result
of consumption of marine fish (for
methylmercury, exposure from any
route other than eating fish is
negligible). Specifically, EPA assumed a
default intake of freshwater and
estuarine and marine finfish and
shellfish of 17.5 grams per day (or two
8-ounce meals a month) conforming to
EPA’s methodology. (EPA;
‘‘Methodology for Deriving Ambient
Water Quality Criteria for the Protection
of Human Health (2000),’’ EPA–822–B–
00–004 (October 2000) (‘‘2000 Water
Quality Criteria Methodology’’)). This
default (to be used by EPA for national
criteria or others in the absence of data
specific to a waterbody) is the 90th
percentile total (commercial and noncommercial) freshwater and estuarine
finfish and shellfish consumption
reported by adults, both consumers and
non-consumers. The source of this data
is the 1994–1996 Continuing Study of
Food Intake by Individuals (CSFII). This
is a large ongoing U.S. food
consumption survey conducted by
USDA.
In addition, in accordance with EPA’s
published methodology, in developing
the criterion, EPA used a relative source
contribution (RSC) approach to
apportion the RfD to ensure that the
water quality criterion is protective,
given other sources of exposure. The
RSC approach apportions the RfD
according to routes of exposures; for
methylmercury this adjustment was
done to account for marine fish
consumption, as the criterion is for
freshwater and estuarine finfish and
shellfish. In deriving the methylmercury
water quality criterion, EPA assumed an
exposure to methylmercury in marine
fish that is equivalent to 27 percent of
RfD. That is, EPA developed the
criterion so that it would be protective
even if an individual is consuming
typical amounts of fish from other
sources (i.e., marine fish).
D. EPA’s Methodology for Assessing
Methylmercury Levels in Fish Tissues
To estimate methylmercury levels,
including methylmercury attributable to
Utility Units, in consumed freshwater
fish, EPA’s analysis relied primarily on
monitoring data (i.e., fish tissue samples
collected from freshwater sites across
the study area). EPA used sources of
national-level monitored Hg data. The
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National Listing of Fish and Wildlife
Advisories (NLFA), which is maintained
by EPA, contains data from over 80,000
fish tissue samples across the U.S. In
addition to the NLFA, EPA’s National
Fish Tissue Survey (NFTS) provides
useful data. Conducted in 2000–2003,
this dataset includes fish tissue samples
from 500 randomly selected lakes and
reservoirs across the U.S. EPA considers
these combined two data sets to be
sufficiently comprehensive and
sufficiently inclusive of the waterbodies
of highest exposure for use in EPA’s
regional analysis, although, as discussed
in the TSD, for certain areas of the
country, gaps in the datasets have led
EPA to rely on overall regional trends to
draw conclusions for local areas.
The NLFA is the most extensive
available source of fish tissue sampling
data for Hg. It currently includes fish
tissue contaminant data collected by
states (and submitted to EPA) from over
10,000 locations nationwide, with most
of the locations in the eastern half of the
U.S. In general, the States historically
sampled waterbodies in areas of
suspected contamination. More
recently, states have also focused
sampling efforts on areas of elevated
fishing pressure. Almost all of the tissue
samples include tests for Hg. The NLFA
includes roughly 83,000 Hg samples
collected in the U.S. between 1967 and
2002. In the dataset, most samples are
described according to the sample
location, sample date, measured Hg
concentration, species and size of fish,
and the part of the fish sampled.
Based on the geographic coordinates
provided in the NLFA database, EPA
also defined two additional fields for
each Hg sample:
—The eight-digit watershed
(hydrological unit code (HUC)
(discussed below)) in which the
sample was located; and
—The type of waterbody (i.e., lake or
river/stream) from which the sample
was taken.
The HUC, developed by the USGS,
spatially delineates watersheds
throughout the United States.
Hydrologic units are available at four
levels of aggregation, ranging from a
two-digit regional level (21 units
nationwide) to the eight-digit HUC
(2,150 distinct units). The eight-digit
HUC-level designation is useful for this
analysis because it provides a nationally
consistent approach for grouping
waterbodies on a ‘‘local’’ scale (the
average HUC area is 1,631 sq mi).45
45 More information regarding these hydrological
units can be found through the USGS Web site
https://water.usgs.gov/GIS/huc.html.
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We made the water body type
assignments using proximity analysis in
ArcINFO. Each sampling site was
assigned to either a flowing (e.g., river,
stream) or a stationary (e.g., lake,
reservoir) waterbody, according the type
of waterbody most closely located to the
site’s lat/long coordinates. We used
National Hydrology Dataset (NHD) in
the proximity analysis.
For purposes of the modeling
described below, we restricted the
samples selected from the NLFA data to
those that met the following criteria:
• Collected after 1999;
• Sampled from freshwater species
(i.e., saltwater species are excluded from
the analysis); and
• Sampled from freshwater (rather
than estuarine or coastal) waterbodies.
These NLFA Hg sampling data were
supplemented with additional
observations from EPA’s National Fish
Tissue Survey (NFTS). Compiled in
2000–2003, this dataset includes fish
tissue samples from 500 randomly
selected lakes and reservoirs across the
U.S. Combining data from NLFA and
NFTS, samples from 1633 lake and river
sampling sites were selected for the
analysis.
Although the NLFA and NFTS
provide rich sources of data on Hg
levels in freshwater fish for the study
area, the fish tissue samples in these
databases vary in several respects. For
example, they vary according to the size
and species of fish sampled and
according to the sampling method used
(e.g., the cut of fish sampled). We
limited the samples we used for this
analysis to fish likely to be caught and
consumed, defined for this analysis as
fish greater than or equal to seven
inches in length.
The TSD describes in more detail how
we used the data available in the NLFA
and NFTS datasets.
E. Air Quality Modeling of the Impacts
of Utility Unit Hg on Fish Tissue Levels
EPA conducted computerized
modeling that indicates the effects of
various scenarios for Utility Unit Hg
emissions on fish tissue at the NLFA–
NFTS sites across the country, in both
a 2001 base case and in projected
control cases for the year 2020. This
section summarizes the emissions
inventories used in those modeling
scenarios, and the air quality modeling,
that serve as the basis for determining
the fish tissue impacts of Hg from
Utility Units at various levels of
emissions.
EPA used a sophisticated air quality
model to estimate baseline and postcontrol annual total Hg deposition for
each scenario. EPA then combined the
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estimated changes in Hg depositions
with fish tissue data to determine
estimated changes in methylmercury
levels in fish tissues. EPA then
combined those changes in fish tissue
methylmercury levels with estimates of
fish consumption, for use in estimating
exposure levels.
1. Air Quality Modeling for Hg
Deposition From Utility Mercury
Emissions
This section summarizes the methods
for estimating Hg deposition for 2001
and 2020 base cases and control
scenarios. EPA estimated the Hg
deposition changes using national-scale
applications of the Community MultiScale Air Quality (CMAQ) model in the
contiguous United States.
a. CMAQ Model and Hg Deposition
Estimates. CMAQ is a three-dimensional
grid-based Eulerian air quality model
designed to estimate annual particulate
concentrations and Hg deposition over
large spatial scales (e.g., over the
contiguous United States). Because it
accounts for spatial and temporal
variations as well as differences in the
reactivity of emissions, CMAQ is useful
for evaluating the impacts of changes in
utility Hg emissions, under various
scenarios, on U.S. Hg deposition. Our
analysis applies the modeling system to
the entire United States for the
following emissions scenarios:
(1) A 2001 base year;
(2) A 2001 base year of utility Hg
emissions only;
(3) A 2020 projection that includes
utility Hg emissions as reduced through
implementation of CAIR;
(4) A 2020 projection with utility Hg
emissions zeroed-out; 46
(5) A 2020 projection that includes
utility Hg emissions as reduced through
implementation of CAMR (which, in
turn, reflects both CAIR reductions and
the reductions from the additional, 2018
controls); and
(6) A 2020 projection that includes
utility Hg emissions as reduced through
a second CAMR option (this second
CAMR option reflects both CAIR
reductions and a set of additional
reductions that are tighter than the ones
adopted in CAMR).
The CMAQ version 4.3 was employed
for this CAMR modeling analysis. This
version reflects updates in a number of
areas to improve performance and
address comments from the peer review.
CMAQ simulates every hour of every
day of the year and, thus, requires a
46 The reference to ‘‘zeroed out’’ means that the
modeled inventory did not include any amount of
Hg emissions from utilities. This ‘‘zero-out’’
technique allows focus on the impact of the utilities
alone.
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variety of input files that contain
information pertaining to the modeling
domain and simulation period. These
include hourly emissions estimates and
meteorological data in every grid cell, as
well as a set of pollutant concentrations
to initialize the model and to specify
concentrations along the modeling
domain boundaries. These initial and
boundary concentrations were obtained
from output of a global chemistry
model. We use the model predictions in
a relative sense by first determining the
ratio of Hg deposition predictions. The
calculated relative change is then
combined with the corresponding fish
tissue concentration data to project fish
tissue concentrations for the future case
scenarios.
b. Modeling Domain and Simulation
Periods. The modeling domain
encompasses the lower 48 States and
extends from 126 degrees to 66 degrees
west longitude and from 24 degrees
north latitude to 52 degrees north
latitude. The modeling domain is
segmented into rectangular blocks
referred to as grid cells. The model
actually predicts pollutant
concentrations for each of these grid
cells. For this application, the
horizontal grid cells are roughly 36 km
by 36 km. In addition, the modeling
domain contains 14 vertical layers with
the top of the modeling domain at about
16,200 meters. Within the domain each
vertical layer has 16,576 grid cells.
The simulation periods modeled by
CMAQ included separate full-year
application for each of the emissions
scenarios modeled.
c. Model Inputs. CMAQ requires a
variety of input files that contain
information pertaining to the modeling
domain and simulation period. These
include gridded, hourly emissions
estimates and meteorological data and
initial and boundary conditions.
Separate emissions inventories were
prepared for the 2001 base year and
each of the future-year base cases and
control scenarios. All other inputs were
specified for the 2001 base year model
application and remained unchanged
for each future-year modeling scenario.
CMAQ requires detailed emissions
inventories containing temporally
allocated emissions for each grid cell in
the modeling domain for each species
being simulated. The previously
described annual emission inventories
were preprocessed into model-ready
inputs through the emissions
preprocessing system. Details of the
preprocessing of emissions are provided
in the Clean Air Interstate Rule
Emissions Inventory Technical Support
Document (Emissions Inventory TSD).
Meteorological inputs reflecting 2001
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conditions across the contiguous United
States were derived from version 5 of
the Mesoscale Model (MM5). These
inputs include horizontal wind
components (i.e., speed and direction),
temperature, moisture, vertical diffusion
rates, and rainfall rates for each grid cell
in each vertical layer.
The lateral boundary and initial
species concentrations are provided by
a three-dimensional global atmospheric
chemistry and transport model (GEOSCHEM). The lateral boundary species
concentrations varied with height and
time (every 3 hours). Terrain elevations
and land use information were obtained
from the U.S. Geological Survey
database at 10 km resolution and
aggregated to the roughly 36 km
horizontal resolution used for this
CMAQ application.
d. CMAQ Model Evaluation. An
operational model performance
evaluation for Hg wet deposition for
2001 was performed to estimate the
ability of the CMAQ modeling system to
replicate base-year wet deposition of Hg.
Because measurements for the dry
deposition of Hg do not currently exist,
the modeled dry deposition
performance could not be evaluated.
The wet deposition evaluation
principally comprises statistical
assessments of model versus observed
pairs that were paired in time and space
on a weekly basis. This evaluation
includes comparisons of model
predictions to the corresponding weekly
measurements from the Mercury
Deposition Network (MDN).
As discussed in the TSD, in EPA’s
view, CMAQ model performance for wet
deposition shows very good agreement
with the MDN monitoring sites with an
underprediction bias well within
accepted performance criteria. It should
be noted that the application of a
sophisticated photochemical grid model
like CMAQ has been demonstrated to be
appropriate to support national and
regional assessments of control
strategies on atmospheric
concentrations such as today’s rule.
Therefore, for purposes of assessing
impacts on regional patterns of Hg
deposition, we aggregate individual
CMAQ grids to watersheds.
2. Emission Inventories and Estimated
EGU (Utility Unit) Emission Reductions
As discussed in the Clean Air
Mercury Rule Emission Inventory
Technical Memorandum, EPA
developed 2001 and 2020 Hg emission
inventories for the air quality modeling.
EPA relied on the 2001 Hg emission
inventory as the base case. The base
case consists of the level of Hg
emissions, including Utility Unit
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emissions reduced by controls
implemented for purposes of the acid
deposition provisions and for other
purposes, before reductions under CAIR
(required under CAA section
110(a)(2)(D)) or CAMR (required under
section 111). For comparison purposes,
EPA also conducted an air quality
modeling run of the 2001 Hg emissions
inventories with Utility Units’ Hg
emissions ‘‘zeroed out.’’ EPA relied on
the Integrated Planning Model (IPM),
discussed below, to develop projections
of EGU emissions for 2020. The 2020
utility Hg emission inventories reflect
reductions under various control
scenarios.
a. Use of IPM for Estimating Utility
Unit Emissions. EPA projected future
Hg emissions from the power generation
sector using the IPM. The EPA uses IPM
to analyze the projected impact of
environmental policies on the electric
power sector in the 48 contiguous states
and the District of Columbia.
IPM is a multi-regional, dynamic,
deterministic linear programming model
of the U.S. electric power sector. The
EPA used IPM to project both the
national level and the unit level of
Utility Unit Hg emissions under
different control scenarios. The EPA
also used IPM to project the costs of
those controls.
As noted elsewhere, the CAIR SO2
and NOX controls provide the basis for
reducing Hg to the CAIR co-benefit
levels in 2010 and 2020. EPA assumed
that states would choose to implement
the CAIR-required SO2 and NOX
reductions by controlling Utility Units,
and by doing so through the EPAadministered cap-and-trade program.
This assumption is reasonable, for
present purposes, because of the costsavings associated with the cap-andtrade program.
EPA used IPM to project the
distribution within the utility industry
of the emission controls to comply with
CAIR. EPA then was able to use IPM to
project the amount, and geographic
distribution, of Hg emissions that would
result from implementation of those
CAIR-required emissions controls. In
addition, EPA used IPM to project the
geographic distribution of the additional
emissions controls under section 111,
and the associated costs.
In these IPM runs, EPA assumed that
states would implement the Hg
requirements through the Hg cap-andtrade program that EPA is establishing.
EPA further assumed that the States
would implement the additional
reductions under section 111, beginning
in 2010, through the same cap-and-trade
program. The cap-and-trade program is
implemented in two phases, with a cap
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of 38 tons in 2010 (set at the co-benefits
reduction under CAIR) and a lower cap
of 15 tons in 2018. EPA modeling of
section 111 projects banking of excess
Hg reductions in the 2010 to 2017
timeframe for compliance with the cap
in 2018 and beyond timeframe.
Although states are not required to
adopt the EPA-administered trading
program, this program assures that those
reductions will be achieved with the
least cost. For that reason, EPA believes
it reasonable to assume that States will
adopt the program.
The National Electric Energy Data
System (NEEDS) contains the generation
unit records used to construct model
plants that represent existing and
planned/committed units in EPA
modeling applications of IPM. The
NEEDS includes basic geographic,
operating, air emissions requirements,
and other data on all the generation
units that are represented by model
plants in EPA’s v.2.1.9 update of IPM.
The IPM uses model run years to
represent the full planning horizon
being modeled. That is, several years in
the planning horizon are mapped into a
representative model run year, enabling
IPM to perform multiple year analyses
while keeping the model size
manageable. Although IPM reports
results only for model run years, it takes
into account the costs in all years in the
planning horizon. In EPA’s v.2.1.9
update of IPM, the years 2008 through
2012 are mapped to run year 2010, and
the years 2013 through 2017 are mapped
to run year 2015, and the years 2018
through 2022 are mapped to 2020.47
Model outputs for 2009 and 2010 are
from the 2010 run year. More detail on
IPM can be found in the model
documentation in the docket or at
https://www.epa.gov/airmarkets/epa-ipm
and more discussion of modeled
scenarios can be found in the Regulatory
Impact Assessment for CAIR and CAMR
in the docket.
IPM has been used for evaluating the
economic and emission impacts of
environmental policies for over a
decade. The model’s base case
incorporates title IV of the Clean Air Act
(the Acid Rain Program), the NOX SIP
Call, various New Source Review (NSR)
settlements, and several state rules
affecting emissions of SO2 and NOX that
were finalized prior to April of 2004.
The NSR settlements include
agreements between EPA and certain
utilities. IPM also includes various
current and future state programs in
Connecticut, Illinois, Maine,
Massachusetts, Minnesota, New
Hampshire, North Carolina, New York,
Oregon, Texas, and Wisconsin. IPM
includes state rules that have been
finalized and/or approved by a state’s
legislature or environmental agency.
The base case is used to provide a
reference point to compare
environmental policies and assess their
impacts and does not reflect a future
scenario that EPA predicts will occur.
EPA’s modeling is based on various
input assumptions that are uncertain,
particularly assumptions for Hg control
technology, future fuel prices and
electricity demand growth. While IPM
contains an assumption of 90% Hg
16017
removal for ACI and, for modeling
convenience, does not constrain the
timeframe for the availability of
technology, this should not be
interpreted as implying any assessment
of the availability of technology. For
further discussion of the availability of
Hg technology, see EPA’s Office of
Research and Development (ORD)
Control of Emissions from Coal-Fired
Electric Utility Boilers: An Update,
EPA/Office of Research and
Development, March 2005, in CAMR
docket. There may also be technologies
available for SO2 and NOX control that
are not accounted for in IPM. Therefore
the technologies that plants may use to
comply with this program may not be
accurately projected by IPM in all cases.
These and other assumptions and
uncertainties are discussed further in
the RIA for CAIR and CAMR in the
docket. More detail on IPM can be
found in the model documentation,
which provides additional information
on the assumptions discussed here as
well as all other assumptions and inputs
to the model (see docket or https://
www.epa.gov/airmarkets/epa-ipm).
b. Emission Estimates. The emission
sources and the basis for current and
future-year inventories are listed in
Table VI–1. Table VI–2 summarizes the
Hg emissions and the change in the
emissions from EGUs (Utility Units) that
we expect to result under the various
EGU control scenarios (under CAIR and
CAMR) that we used in modeling
deposition changes.
TABLE VI—1. EMISSION SOURCES AND BASIS FOR CURRENT AND FUTURE-YEAR MERCURY INVENTORIES
Sector
Emissions source
2001 Base year
Future-year base case projections
EGU ...............................................
Power industry electric generating
units (EGUs).
Non-Utility Point ............................
1999 National Emission Inventory
(NEI) data.
1999 NEI, with medical waste incinerator sources replaced with
draft 2002 NEI.
Integrated Planning Model (IPM).
All other stationary sources inventoried at the county level.
1999 NEI, with medical waste incinerator sources replaced with
draft 2002 NEI.
Non-EGU point sources .................
Non-point .......................................
(1) Department of Energy (DOE)
fuel use projections, (2) Regional Economic Model, Inc.
(REMI) Policy Insight model,
(3) decreases to REMI results
based on trade associations,
Bureau of Labor Statistics
(BLS) projections and Bureau
of Economic Analysis (BEA)
historical growth from 1987 to
2002, (4) Maximum Achievable
Control Technology category
growth and control assumptions.
Same as above.
This table documents only the sources of data for the U.S. inventory. The sources of data used for Canada and Mexico are explained in the
technical support memorandum and were held constant from the base year to the future years.
47 An exception was made to the run year
mapping for an IPM sensitivity run that examined
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the impact of a NOX Early Reduction Pool (ERP).
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mapped to 2010 and 2008 was mapped to 2008.
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TABLE VI—2. SUMMARY OF MODELED MERCURY EMISSIONS FOR CLEAN AIR MERCURY RULE
Elemental mercury
Reactive gaseous
mercury
Particulate
mercury
Total mercury
2001 Base Case Emissions (tons)
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
26.26
37.85
5.05
20.58
13.33
1.53
1.73
7.60
0.96
48.57
58.78
7.54
All Sources .......................................................................
69.16
35.44
10.29
114.89
2001 Utility Mercury Emissions Zero-Out (tons)
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
0.00
37.85
5.05
0.00
13.33
1.53
0.00
7.60
0.96
0.00
58.78
7.54
All Sources .......................................................................
42.90
14.86
8.56
66.32
2020 With CAIR Emissions (tons)
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
25.72
28.03
5.69
7.87
10.37
1.30
0.83
6.61
0.77
34.42
45.01
7.76
All Sources ...............................................................................
59.44
19.54
8.21
87.19
2020 With CAIR Utility Mercury Emissions Zero-Out
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
0.00
28.03
5.69
0.00
10.37
1.30
0.00
6.61
0.77
0.00
45.01
7.76
All Sources .......................................................................
33.72
11.67
7.38
52.77
2020 With CAIR and CAMR
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
17.65
28.03
5.69
6.57
10.37
1.30
0.83
6.61
0.77
25.05
45.01
7.76
All Sources .......................................................................
51.37
18.24
8.21
77.82
2020 With CAIR and Alternative CAMR Control Option
EGU Sources ...........................................................................
Non-EGU Point Sources ..........................................................
Area Sources ...........................................................................
14.33
28.03
5.69
5.71
10.37
1.30
0.79
6.61
0.77
20.83
45.01
7.76
All Sources .......................................................................
48.05
17.38
8.17
73.60
(Note: ‘‘Reactive Gaseous Mercury’’
refers to oxidized mercury).
(Note: Table IV–2 includes projections
for all EGUs, including other fossil-fired
units, and coal-fired units that are less
than 25 MW.)
c. Projected Hg Emissions. Table VI–
3 provides projected total Hg emissions
levels in 2010, 2015, and 2020. Because
of the banking of excess emissions
reductions under the first phase of the
Hg program, emissions in the second
phase will be initially higher than the
caps that are required under CAMR.
TABLE VI—3. PROJECTED EMISSIONS OF HG WITH THE BASE CASE a (NO FURTHER CONTROLS), WITH CAIR, AND WITH
SECTION 111 CONTROLS
[Tons]
2010
Base Case ...............................................................................................................................................
CAIR ........................................................................................................................................................
CAMR ......................................................................................................................................................
Alternative CAMR Control Option ............................................................................................................
46.6
38.0
31.3
30.9
a Base case includes Title IV Acid Rain Program, NO SIP Call, and state rules finalized before March 2004.
X
Source: Integrated Planning Model run by EPA.
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2015
45.0
34.4
27.9
25.7
2020
46.2
34.0
24.3
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Federal Register / Vol. 70, No. 59 / Tuesday, March 29, 2005 / Rules and Regulations
Emissions projections are presented
for affected coal-fired units.
(Note: Table VI–3 includes projections
for all affected units, i.e., coal-fired units
greater than 25 MW.)
3. Effect of Reductions in Utility Unit
Hg Emissions on Regional Patterns of
Mercury Deposition and Fish Tissue
Methylmercury Concentrations
EPA uses CMAQ to predict the effect
of the various control scenarios on Hg
deposition attributable to Utility Units
within the 48 contiguous states. By
averaging the 36 km CMAQ gridded
deposition estimates to the watershed
(i.e., HUC–8) level, EPA is able to
estimate the effectiveness of reductions
in utility Hg emissions in achieving
reductions in deposition attributable
solely to Utility Units. In addition, by
comparing changes in Hg deposition
before and after implementation of rule
requirements at the geographic location
of the fish tissue sample points, EPA is
able to estimate the effect of reductions
in Hg deposition on fish tissue
methylmercury concentrations at the
sample points.
EPA generates these changes in Hg
deposition by comparing two air
modeling scenarios (e.g., a control
scenario versus a baseline scenario for a
particular simulation year). EPA then
translates these changes in Hg
deposition into changes in
methylmercury fish tissue
concentrations based on a
proportionality assumption: i.e., an
incremental percent change in
deposition produces a matching
percentage change in Hg fish tissue
concentrations.48
EPA is able to use these modeled
changes in methylmercury fish tissue
concentrations, together with
information about fish consumption, to
predict changes in population-level Hg
exposure. These exposure changes
reveal the extent to which reductions in
16019
Utility Unit Hg emissions, and the
extent to which remaining Utility Unit
Hg emissions, affect public health.
F. Fish Tissue Levels of Methylmercury
Modeled To Result After
Implementation of CAIR and CAMR
This section describes the amounts of
Utility Unit attributable Hg deposition
onto watersheds (termed HUC), as well
as the Utility-attributable
methylmercury in fish tissue, all under
the various control scenarios modeled.
1. Utility-Attributable Hg Deposition
Patterns
The air quality modeling shows that
total Hg deposition is not highly
impacted by utility deposition. The
small size of this impact is evident
when utility emissions are, in effect,
zeroed out in the 2001 base case. The
following tables summarize impacts on
total Hg deposition and Hg deposition
attributable to Utility Units.
TABLE VI–4.—SUMMARY STATISTICS FOR TOTAL HG DEPOSITION
[Aggregated to the HUC–8 level]
2001 Base
case
Minimum ...................................................
Maximum ..................................................
50th percentile .........................................
90th percentile .........................................
99th percentile .........................................
6.94
54.54
15.92
22.16
32.35
2001 Utility
zero out
2020 Base
case (with
CAIR)
6.94
54.38
14.60
19.48
27.20
2020 Utility
zero out
6.08
62.76
14.59
19.46
29.15
2020 CAMR
requirements
5.90
62.72
13.92
19.04
28.93
6.08
62.76
14.44
19.37
28.96
2020 CAMR
alternative
6.07
62.75
14.39
19.33
28.95
(All units are expressed in micrograms per square meters.)
TABLE VI–5. SUMMARY STATISTICS FOR UTILITY ATTRIBUTABLE HG DEPOSITION
[aggregated to the HUC–8 level]
2001 Base
case
Minimum ..........................................................................................................
Maximum .........................................................................................................
50th percentile .................................................................................................
90th percentile .................................................................................................
99th percentile .................................................................................................
2020 Base
case (with
CAMR)
0.00
19.71
0.39
4.08
10.15
0.00
4.03
0.3
1.38
2.56
2020 CAMR
Requirements
0.00
3.85
10.26
1.16
2.17
2020 CAMR
Alternative
0.00
3.80
0.22
0.99
2.04
(All units are expressed in micrograms per square meters.)
The median deposition level is
reduced by only 8 percent when utilities
emissions are zeroed out in 2001,
suggesting that utilities are not a major
source of Hg deposition in most HUCs.
Even so, at HUCs with the highest
deposition levels, zeroing out utilities
reduces the 99th percentile deposition
level by 16 percent, suggesting that
there are relatively larger impacts of
utilities in high deposition areas.
By 2020, after implementation of
CAIR, significant reductions in
deposition attributable to utilities
occurs. HUCs with high levels of utility
deposition receive a larger reduction in
Utility-attributable Hg deposition
relative to HUCs with a relatively small
level of Utility-attributable deposition.
Specifically, CAIR results in a 75
percent reduction in the 99th percentile
of Utility-attributable deposition, and a
20 percent reduction in the 50th
percentile. CAIR also shifts the
distribution of utility-attributable
deposition. In the 2001 base case, 10
percent of HUCs had greater than 20
percent of deposition attributable to
utilities. In the 2020 post-CAIR base
case, no HUCs had greater than 20
percent of deposition attributable to
utilities, and 90 percent had less than 9
percent of deposition attributable to
utilities.
48 US EPA, 2001. Mercury Maps: A Quantitative
Spatial Link Between Air Deposition and Fish
Tissue: Peer Reviewed Final Report. EPA–823–R–
01–009. Mercury Maps is discussed at length in the
TSD.
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Additional reductions in Hg
emissions due to the CAMR
requirements result in relatively small
additional shifts in the distribution of
deposition. Additional emissions
reductions due to the CAMR
requirements result in a small
additional reduction in the number of
HUCs with a high percentage of utility-
attributable emissions. (The incremental
impact of the CAMR alternative relative
to the promulgated CAMR requirements
is very small.)
2. EGU-Attributable Methylmercury
Fish Tissue Levels
The following tables summarize the
methylmercury fish tissue levels
associated with the various Utility Unit
Hg emissions scenarios. All units refer
to mg (of methylmercury) per kg (fish
tissue), or parts per million (ppm). As a
frame of reference, it should be noted
that EPA’s default water quality
criterion is 0.3 mg/kg.
TABLE VI—6. SUMMARY STATISTICS FOR TOTAL FISH TISSUE METHYLMERCURY
[Sample locations]
2001 Base
case
Minimum ...................................................
Maximum ..................................................
50th percentile .........................................
90th percentile .........................................
99th percentile .........................................
2001 Utility
zero out
0.00
4.49
0.25
0.90
1.80
2020 Base
case CAIR
0.00
3.64
0.21
0.81
1.65
2020 Zero out
0.00
3.65
0.21
0.79
1.64
0.00
3.46
0.20
0.77
1.57
2020 CAMR
requirements
0.00
3.63
0.21
0.79
1.63
2020 CAMR
alternative
0.00
3.61
0.21
0.78
1.63
(All units are in mg methylmercury per kg fish tissue.)
TABLE VI—7. SUMMARY STATISTICS FOR UTILITY ATTRIBUTABLE FISH TISSUE METHYLMERCURY
[Across sampling locations]
2001 Base
Minimum ..........................................................................................................
Maximum .........................................................................................................
50th percentile .................................................................................................
90th percentile .................................................................................................
99th percentile .................................................................................................
2020 (with
CAIR)
0.00
0.85
0.03
0.11
0.26
0.00
0.25
0.01
0.03
0.10
2020 CAMR
Requirements
0.00
0.19
0.01
0.03
0.09
2020 CAMR
Alternative
0.00
0.18
0.01
0.03
0.08
(All units are in mg methylmercury per kg fish tissue.)
a. 2001 Base case and 2001 Utility
Zero-out. In the 2001 base case, as a
result of all international and U.S.
emissions, and before U.S. utilities
implement reductions from CAIR or
CAMR, the 50th percentile of the
sample points had an estimated
methylmercury fish tissue concentration
of 0.25 mg/kg. The 90th percentile water
body had an estimated methylmercury
fish tissue concentration of 0.90 mg/kg,
and the 99th percentile had 1.80 mg/kg.
The amount of methylmercury
attributable solely to utilities in the
2001 base case, which becomes evident
when utilities are zeroed out, is of
course much smaller. The 50th
percentile of the sample points had an
estimated methylmercury fish tissue
concentration. attributable solely to
utilities, of 0.03 mg/kg. The 90th
percentile had 0.11 mg/kg, the 99th
percentile had 0.26 mg/kg, and the
maximum individual sample point had
0.85 mg/kg.
It should be recalled that EPA
recommends the water quality criterion
of 0.3 mg/kg as a level that, given fish
consumption at the 90th percentile
level, would result in exposure levels
below the RfD. For present purposes,
EPA does not consider the water quality
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criterion of 0.3 mg/kg as a bright-line
test for evaluating fish tissue
methylmercury levels attributable to
U.S. Utility Units. Rather, the criterion
serves as establishing a broad frame of
reference, that serves to place into
context both the overall methylmercury
fish tissue levels (which are attributable
to methylmercury from all sources) and
the methylmercury levels attributable to
Utility Units.
These results indicate the relatively
small percentage of U.S. utility
contribution to U.S. fish tissue
methylmercury levels.
b. 2020: Utilities With CAIR
Reductions. EPA’s modeling shows that
in 2020, as a result of all international
and U.S. emissions, and with U.S.
utilities implementing reductions from
CAIR (but not CAMR), the 50th
percentile of the sample points is
projected to have a methylmercury fish
tissue concentration of 0.21 mg/kg. The
90th percentile is projected to have 0.79
mg/kg, and the 99th percentile is
projected to have 1.64 mg/kg.
The amount of methylmercury in fish
attributable solely to utilities in 2020,
after implementation of the CAIR
reductions (but, again, before CAMR), of
course is smaller. The 50th percentile of
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the sample points is projected to have
fish tissue concentration, attributable
solely to utilities of 0.01 mg/kg. The
90th percentile is projected to have 0.03
mg/kg, the 99th percentile is projected
to have 0.10 mg/kg, and the maximum
individual sample point (i.e., the one
with the highest methylmercury levels)
is projected to have 0.25 mg/kg.
Again, using the 0.3 mg/kg
methylmercury water quality criterion
as a broad frame of reference serving to
place in context both the overall
methylmercury fish tissue levels
(attributable to methylmercury from all
sources) and the methylmercury fish
tissue levels attributable to Utility Units,
it is clear that the latter levels, following
implementation of CAIR, are low.
c. 2020: Utilities with CAMR
Controls. The CAMR level of controls
achieve further, albeit small, reductions
in methylmercury fish tissue
concentrations. Compared to the CAIR
controls, the CAMR controls would
further reduce, in 2020, methylmercury
fish tissue concentrations by, in the 99th
percentile, 0.01 mg/kg.
d. 2020: Utilities with Alternative
CAMR Controls. EPA evaluated, but did
not adopt, a slightly tighter level of
CAMR controls. These alternative
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CAMR controls would have achieved
still further, albeit, again small,
reductions in Hg deposition and in fish
tissue methylmercury levels. Compared
to the CAIR controls, these alternative
CAMR controls would reduce
methylmercury fish tissue levels in 2020
by, in the 99th percentile, 0.02 mg/kg.49
5. Overall Impact of CAIR and CAMR
Controls on Utility Unit Hg Emissions
As described in the CAIR rule, CAIR
reduces EGU Hg emissions from preCAIR levels by a substantial percentage.
CAMR reduces Utility Unit Hg
emissions, from CAIR levels, by 27
percent. CAMR reduces ionic Hg
emissions, those that are most likely to
result in local and regional deposition,
by 17 percent relative to CAIR levels.
These reductions tend to occur from
the largest sources. That is, the larger
the source of Hg emissions, the more
likely it is to implement CAIR or CAMR
controls, and therefore the more likely
it is to reduce its Hg emissions. More
specifically, under the cap-and-trade
system, the marketplace tends to direct
controls to the largest emitters because
those emitters can achieve the most
cost-effective reductions. Compared to
smaller emitters, these larger emitters
have an incentive to implement more
stringent controls, thereby reducing
their emissions further below the level
of their allowances, and thereby
generating a larger number of
allowances for sale to defray control
costs. See ‘‘Proposed National
Emissions Standards for Hazardous Air
Pollutants; and in the Alternative,
Proposed Standards of Performance for
New and Existing Sources: Electric
Utility Steam Generating Units,’’ 9 FR
4652, 4702–03 (Jan. 30, 2004).
G. Exposure to Utility-Attributable
Methylmercury Levels in Fish Tissue
CAIR reduces median Utilityattributable fish tissue methylmercury
levels, from pre-CAIR levels, by 67
percent. CAIR reduces the 99th
percentile Utility-attributable fish tissue
methylmercury levels, from pre-CAIR
levels, by 60 percent. CAMR reduces
median Utility-attributable fish tissue
methylmercury levels, from CAIR levels,
by 12 percent. CAMR reduces the 99th
percentile Utility-attributable fish tissue
methylmercury levels, from CAIR levels,
by 9 percent.
As a result of these reductions, after
CAIR or CAMR, no sample site remains
in which Utility-attributable, emissions
cause methylmercury fish tissue levels
49 A detailed discussion of the control alternatives
we considered and the reason for our final selection
is contained in the preamble to the final CAMR.
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to exceed 0.3 mg/kg (EPA’s water
quality criterion).
Even with these reductions, although
the levels of methylmercury in fish
tissues attributable to Utility Units are
small, the magnitude of methylmercury
exposure depends on consumption
levels and the sensitivity of the
individual. For purposes of assessing
whether utility Hg emissions are
reasonably anticipated to result in
hazards to public health, we focused on
evaluating utility attributable
methylmercury exposures for women of
childbearing age in the general U.S.
population who consume noncommercial (e.g., recreational)
freshwater fish in U.S. waterbodies.
This section describes available
information as to the consumption
levels of women of child-bearing age
within the population of recreational
fishers who consume at typical levels,
and within high-consumption subpopulations; and discusses the amounts
of methylmercury that may be ingested
as a result of those consumption levels.
1. General Population
We believe that only those women of
childbearing age who consume
noncommercially caught U.S.
freshwater fish have the potential for
significant exposures to utilityattributable methylmercury. As a result,
our assessment of the hazards to public
health focuses on those women.
2. Recreational Fishers Who Consume
Fish At Typical Levels.
a. Consumption Levels. For our
analysis of recreational freshwater fish
consumption, EPA has determined that
the sport-caught fish consumption rates
for recreational freshwater fishers
specified as ‘‘recommended’’ in the
EPA’s Exposure Factors Handbook
(mean of 8 gm/day and 95th percentile
of 25 gm/day), represent the most
appropriate values for present purposes.
These recommended values were
derived based on ingestion rates from
four studies conducted in Maine,
Michigan, and Lake Ontario (Ebert et al.,
1992; Connelly et al., 1996; West et al.,
1989; West et al., 1993). These studies
are suitable because they included
information for annual-averaged daily
intake rates for self-caught freshwater
fish by all recreational fishers including
consumers and non-consumers. The
mean values presented in these four
studies ranged from 5 to 17 gm/day,
while the 95th percentile values ranged
from 13 to 39 gm/day.50
50 The 39 gm/day value actually represents a 96th
percentile value.
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The EPA ‘‘recommended values’’
were developed by considering the
range and spread of means and 95th
percent values presented in the four
studies. EPA recognizes that use of
mean and 95th percentile consumption
rates based on these four studies may
not be representative of fishing behavior
in every state and that there may be
regional trends in consumption that
differ from the values used in this
analysis. However, EPA believes that
these four studies represent the best
available data for developing
recreational fisher ingestion rates for
present purposes.
As a result, for today’s purposes of
evaluating the potential for health
effects for consumers of recreational
freshwater fish resulting from exposure
to utility-attributable methylmercury,
we consider both the mean of 8 gm/day
consumption and the 95th percentile
amount of 25 gm/day.
b. Levels of Consumption Combined
with Levels of Utility-Attributable
Methylmercury in Fish Tissue. As
described above, fish tissue levels of
Utility-attributable methylmercury, for
virtually all sample points, are only a
fraction of the 0.3 mg/kg (fish tissue)
water quality criterion. EPA evaluated
recreational fish consumers’ exposure to
this Utility-Attributable methylmercury
by calculating the level of exposure to
this methylmercury and comparing it to
the RfD when background exposures are
not considered. For the purposes of
assessing population exposure due
solely to power plants, we create an
index of daily intake (IDI).The IDI is
defined as the ratio of exposure due
solely to power plants to an exposure of
0.1 µug/kg bw/day. The IDI is defined so
that an IDI of 1 is equal to an
incremental exposure equal to the RfD
level, recognizing that the RfD is an
absolute level, while the IDI is based on
incremental exposure without regard to
absolute levels. Note that an IDI value
of 1 would represent an absolute
exposure greater than the RfD when
background exposures are considered.
At either the mean fish consumption
rate of 8 gm/day or the 95th percentile
fish consumption rate of 25 gm/day for
recreational fish consumers discussed
above, and using the 99th percentile
methylmercury fish tissue concentration
attributable to Utility Unit (and a typical
body weight of 64 kg for women of
child-bearing age), the calculated
Utility-attributable methylmercury
exposures are 0.013 µug/kg body weight
per day and 0.04 µug/kg body weight
per day, respectively. Both calculated
exposures are well below the RfD of 0.1
µug/kg body weight per day (an IDI
value well below 1).
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EPA uses the RfD to place ingestion
levels in context. The RfD level of
methylmercury ingestion—0.1 µug/kg
body weight—should not be considered
a bright line standard above which
adverse health effects occur, but rather
as an aid in establishing the context for
evaluating both overall methylmercury
ingestion (arising from methylmercury
from all sources) as well as UtilityAttributable methylmercury ingestion in
light of consumption rates. Our analysis
concludes that Utility Unit Hg
emissions do not cause hazards to the
health of the general public or higher
fish consuming recreational anglers.
3. High-Level Fish Consumption SubPopulations
Although exposure to Utilityattributable methylmercury from
freshwater fish tissue is quite low for
recreational fishers generally, as just
described, EPA recognizes that certain
sub-populations consume higher levels
of U.S. freshwater fish. These
populations may include a subset of
recreational fishers who consume large
quantities of fish, individuals who are
subsistence fishers, and individuals
who are part of certain ethnic groups.
EPA is aware that at very high
consumption levels, even relatively
small concentrations of methylmercury
in fish may result in exposures that
exceed the RfD.
However, as described in the TSD,
characterization of fish consumption
rates for the highest fish consuming
subpopulations (e.g., Native American
and other ethnic populations exhibiting
subsistence-like consumption) in the
context of a larger regional or national
analysis is technically challenging. Peer
reviewed study data on these
populations is relatively limited,
especially when subjected to the criteria
outlined in the TSD. Many of the high
consumption groups that have been
studied are located near the ocean and
consequently have a significant fraction
of their overall exposure comprised of
saltwater fish. In addition, some of these
studies provide details on seasonal
consumption rates, but do not integrate
these rates to provide an overall mean
annual-averaged consumption rate
relevant to an RfD-based analysis.
Although many of these studies
provide mean consumption rates, few
have identified specific high-end
percentile values (e.g., 90th, 95th or
99th percentile consumption rates).
Instead, many studies, including a
number of non-peer reviewed sources,
cite non-specific high-end or bounding
point estimates (e.g., the range of
consumption rates for the Ojibwe
submitted for the CAMR NODA). While
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these point values can be used in
developing high-end bounding
scenarios for evaluating risk to these
groups, they do not support populationlevel analysis of exposure since they
cannot be used to fit distributions
characterizing variability in fish
consumption rates across these subpopulations (as noted above, modeling
of population-level exposures requires
that distributions characterizing fish
consumption rates across a particular
population be developed).
An additional challenge in
characterizing high-level fish
consumption is that care needs to be
taken in extrapolating study results from
one group to another. This reflects the
fact that high-level fish consumption is
often tied to socio-cultural practices and
consequently consumption rates for a
study population cannot be easily
transferred to other groups which may
have different practices (e.g., practices
for one Native American tribe may not
be relevant to another and consequently
behavior regarding fish consumption
may not be generalized).
Despite these challenges in
characterizing high-level consumption,
EPA has developed recommended
subsistence-level fish consumption rates
of 60 g/day (mean) and 170 g/day (95th
percentile) (EPA, 1997, Exposure
Factors Handbook). These values are
based on a study of several Native
American Tribes located along the
Columbia River in Washington State.
Although these consumption rates are
specific to the tribes included in the
study and reflect their particular sociocultural practices (including seasonality
and target fish species), EPA believes
that this study does provide a
reasonable characterization of highconsuming subsistence-like freshwater
fishing behavior (EPA, 1997, Exposure
Factors Handbook). Therefore, in the
absence of data on local practices, EPA
recommends that these consumption
rates be used to model high-consuming
groups in other locations. It is important
to note that, as explained above,
application of these subsistence
consumption rates outside of the
original Columbia River study area
could be problematic because it would
be difficult to transfer these
consumption rates to a different group
that might exhibit different fishing
behavior. However, these recommended
rates can be used to model subsistence
scenarios at different locations.
Although these subsistence
consumption rates are recommended by
EPA, commenters (including NODA
comments obtained for this rule), have
identified alternative consumption rates
for specific high consuming groups that
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are in some instances, higher than these
recommended values. For example, a
survey by the Great Lakes Indian Fish
and Wildlife Commission (GLIFWC) (as
referenced in comments to the CAMR
NODA) indicates that consumption rates
by members of Ojibwe Great Lakes
tribes during fall spearing season may
range from 155.8–240.7 g/day and may
range from 189.6–292.8 g/day during the
spring. EPA has reviewed these
comments and does not believe that it
would be appropriate to rely on them
for purposes this rulemaking. First, the
data has not been peer reviewed.
Moreover, it is not clear from the
comments how many people consume
fish at those rates, to what extent those
fish consumers are women of childbearing years, and how to annualize
these seasonal sales.51
For all the above reasons, and despite
comments indicating that some
subgroups may have larger short-term
consumption rates, EPA believes that
the Columbia River-based consumption
rates of between 60 g/day (mean) and
170 g/day (95th percentile) are
appropriate default values for
subsistence fish consumers.
H. EPA Concludes That Utility Hg
Emissions Remaining After Imposition
of Other Requirements of the Act, in
Particular CAA Sections 110(a)(2)(D)
and 111, Do Not Result in Hazards to
Public Health
As discussed above, Congress
mandated that EPA assess hazards to
public health reasonably anticipated to
occur as a result of utility HAP
emissions remaining after imposition of
the requirements of the Act, and to
regulate Utility Units under section 112
if EPA determines that such regulation
is ‘‘appropriate’’ and ‘‘necessary.’’ The
issue of whether the level of Hg
emissions from Utility Units remaining
after implementation of CAA section
110(a)(2)(D), and independently section
111, cause hazards to public health is
directly relevant to our conclusion set
forth in section IV.A. above, namely,
that it is not appropriate to regulate
coal-fired Utility Units under section
112 on the basis of Hg emissions. For
the reasons discussed below, EPA
concludes that the level of Hg emissions
remaining after implementation of
CAIR, and, independently, CAMR,
which implement sections 110(a)(2)(D)
and 111, respectively, do not result in
hazards to public health.
1. ‘‘Hazards to Public Health’’ Under
Section 112(n)(1)(A)
51 As discussed below, the Ojibwe Great Lakes
tribes do not appear to be located in areas with high
utility-attributable Hg deposition.
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Section 112(n)(1)(A) establishes the
backdrop against which our utility
‘‘appropriate and necessary’’
determination should be judged. Again,
we must decide whether we reasonably
anticipate utility Hg emissions
remaining after imposition of the
requirements of the Act to cause hazards
to public health. If they do, then we
must determine whether it is
appropriate and necessary to regulate
Utility Units under section 112. If utility
Hg emissions do not cause public health
hazards, however, which indeed is what
we conclude today, then it is not
appropriate to regulate such emissions
under section 112, and there is no need
to proceed to the ‘‘necessary’’ prong of
the section 112(n)(1)(A) inquiry, as
explained above.
Section 112(n)(1)(A) defines neither
what constitutes a ‘‘hazard’’ to public
health nor what EPA’s obligations
would be if such hazard were identified.
Therefore, we believe that EPA has wide
discretion, using its technical expertise,
to define ‘‘hazards to public health,’’
and to determine whether Hg emissions
from utilities pose such a hazard. EPA’s
judgment should only be overturned if
it is deemed unreasonable, not merely
because other, reasonable alternatives
exist. Department of Treasury v. FLRA,
494 U.S. 922, 933 (1990); Texas Office
of Public Utility Counsel v. FCC, 265
F.3d 313, 320 (5th Cir. 2001).
Although section 112(n)(1)(A) does
not define ‘‘hazards to public health,’’
section 112(n)(1)(C) offers guidance
with respect to determining whether Hg
emissions result in hazards to public
health. In that section, Congress asked
the National Institute of Environmental
Health Sciences to conduct a study to
determine the ‘‘threshold level of
mercury exposure below which adverse
human health effects are not expected
to occur.’’ (Emphasis added) Congress
further mandated that the study include
a threshold for Hg concentrations in fish
tissue which may be consumed,
including consumption by ‘‘sensitive
populations’’ without adverse effects on
public health. Implicit in this direction,
is that Congress was concerned, first
about public health, not environmental
effects. EPA has identified the exposure
to Hg through consumption of
contaminated fish as a pathway to
human health effects, and EPA has also,
in its discretion, looked at the health
effects on sensitive populations.
In interpreting what ‘‘hazards to
public health’’ might be reasonably
anticipated under section 112(n)(1)(A),
we think it is also useful to look at the
DC Circuit’s Vinyl Chloride decision,
824 F.2d 1146 (1987), and the analysis
EPA articulated in its so-called
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‘‘benzene’’ analysis, 54 FR 38044 (Sept.
14, 1989). Although the Vinyl Chloride
decision and ‘‘benzene’’ analysis
address the issue of how to protect
public health ‘‘with an ample margin of
safety,’’ and are thus more stringent
than the standard established in section
112(n)(1)(A), we nevertheless believe
that the general principles articulated in
Vinyl Chloride and the ‘‘benzene’’
analysis are relevant to our analysis of
assessing hazards to public health
pursuant to section 112(n)(1)(A). Some
of those key principles include: (1)
‘‘Safe’’ does not mean ‘‘risk free,’’
(Administrator is to determine what
risks are acceptable in the world in
which we live, where such activities as
driving a car are considered generally
safe notwithstanding the known risk
involved), Vinyl Chloride, 824 F.2d at
1165; (2) something is ‘‘ ‘unsafe’ only
when it threatens humans with a
significant risk of harm,’ ’’ id. at 1153;
(3) EPA, not the courts, has the
technical expertise to determine what
risks are acceptable, id. at 1163; (4) EPA
is permitted to account for uncertainty
and to use ‘‘expert discretion to
determine what action should be taken
in light of that uncertainty,’’ id.; and (5)
in determining what is ‘‘safe’’ or
‘‘acceptable,’’ EPA should consider a
variety of factors, including: (a)
Estimated risk to a maximally exposed
individual (the so-called ‘‘maximum
individual risk’’ or ‘‘MIR’’); (b) overall
incidence of cancer or other serious
health effects within the exposed
population; (c) the numbers of persons
exposed within each individual lifetime
risk range; (d) the science policy
assumptions and uncertainties
associated with the risk measures; (e)
weight of the scientific evidence for
human health effects; and (f) other
quantified or unquantified health
effects. (See 54 FR at 38045–46, 38057).
In assessing whether remaining utility
HAP emissions pose hazards to public
health, consistent with section
112(n)(1)(C) and the above identified
factors, we looked at the public’s,
including sensitive populations’ (i.e.,
fish consumers), exposure to
methylmercury through fish
consumption attributable to utilities
alone. Based on this assessment, and as
explained further below, EPA concludes
that remaining utility HAP emissions do
not pose hazards to public health.
2. CAIR and CAMR Reduce the Public’s
Methylmercury Exposure Due to Fish
Consumption to Below the
Methylmercury RfD (Below an IDI Value
of 1)
As discussed above, EPA has adopted
a water quality criterion for
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16023
methylmercury for states to use in
establishing water quality standards to
protect public health. The criterion,
expressed as a fish tissue concentration,
of 0.3 mg/kg was derived from the
methylmercury RfD (taking into account
the possibility that a person may be
exposed to methylmercury via
commercial fish to some degree, as
expressed in the RSC described
elsewhere). At this level, people
consuming at a high-end fish
consumption rate of 17.5 grams per day
would not be exposed above the
methylmercury RfD. As noted above,
this value represents the 90th percentile
fish consumption rate.
In the base year of 2001 (i.e., prior to
both CAIR and CAMR), fish-tissue
methylmercury concentrations at the
90th percentile, 99th percentile, and
maximum (that is, the single highest
concentration) levels, attributable to
utilities, are 0.11, 0.27, and 0.85 mg/kg,
respectively. CAIR reduces the utilityattributable methylmercury fish-tissue
concentrations at the 90th percentile,
99th percentile, and maximum level to
0.03, 0.10, and 0.25 mg/kg, respectively.
CAMR reduces these concentrations
even further to 0.03, 0.09, and 0.19 mg/
kg, respectively. These post CAIR and
CAMR levels are considerably below the
methylmercury water quality criterion
of 0.3 mg/kg.
At all of these post-control
methylmercury levels, fish consumers at
the water quality criterion 90th
percentile consumption level of 17.5
grams per day are well below the RfD
(below an IDI value of 1). Further, these
concentration values when applied to
the 95th percentile consumption rate for
recreational freshwater anglers
identified in EPA’s Exposure Factors
Handbook, i.e., 25 grams per day, also
result in exposures below the RfD
(below an IDI value of 1). As a result,
it is evident that the general population
(which is expected to consume less U.S.
freshwater fish than recreational
anglers) does not confront hazards to
public health from utility-attributable
methylmercury.
At the methylmercury fish tissue
concentrations attributable to utilities
remaining after implementation of CAIR
and CAMR, it is possible that consumers
eating at the subsistence-level fish
consumption rates of 60 g/day (mean)
and 170 g/day (95th percentile), see
Exposure Factors Handbook, could
exceed the RfD (an IDI value greater
than 1) as a result of utility-attributable
emissions if they are in fact consuming
fish from the most contaminated
locations. In other words, for a fish
consumer to exceed the RfD (an IDI
value greater than 1) as a result of utility
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Hg emissions, they have to both (1)
consume fish at the highest
consumption rates and (2) consume fish
from waterbodies with the highest levels
of utility-attributable Hg fish-tissue
concentrations. As discussed in the
TSD, the probability of these factors
converging is quite low. For example,
after CAIR, the probability that a
recreational angler will exceed the RfD
(an IDI value greater than 1) exclusively
as a result of utility Hg emissions is only
0.01 percent. After CAMR, the
probability drops even lower. Our
analysis further shows that even if there
were a convergence of the unlikely
factors of consuming at the 99th
percentile consumption rates and at the
99th percentile methylmecury fish
tissue concentrations, exposure would
exceed the RfD by only 10 percent (an
IDI value of 1.1). Exceeding the RfD by
this amount (an IDI value of 1.1) does
not mean that an adverse effect will
occur. Indeed, 10 percent above the RfD
(an IDI value of 1.1), or 0.11 µg/kg-bw/
day, is below the World Health
Organization’s level of 0.23 µg/kg-bw/
day.52
Consumption rates for subsistence
fishers are much higher than
recreational anglers. As such, these
populations have a greater probability of
exceeding the RfD (an IDI value greater
than 1). For this to happen, the
subsistence fisher still must be at the
high-end of the distribution for both
consumption and utility-attributable
methylmercury fish tissue
concentrations. Our statistical data
suggest that subsistence anglers at the
99th percentile consumption rate and
the 99th percentile concentration level
could exceed the RfD (an IDI value
greater than 1). Holding consumption
rates at the 99th percentile, the
subsistence angler will likely exceed the
RfD (an IDI value greater than 1) at or
52 The choice of an ‘‘acceptable’’ risk level is one
of policy informed by science. The RfD does not
represent a ‘‘bright line’’ above which individuals
are at risk of significant adverse effects. Rather, it
reflects a level where EPA can state with reasonable
certainty that risks are not appreciable. The Agency
further notes that a number of other national and
international scientific bodies have assessed the
health effects of Hg and have adopted levels greater
than EPA’s RfD. As exposure levels increase beyond
the RfD, the possibility of deleterious effects
increases, but the point at which they become
‘‘unacceptable’’ must be determined on a case-bycase basis. In making this determination, the
Agency considers a number of factors including: (1)
Confidence in the risk estimate: How certain is the
scientific information supporting the link between
possible health effects and exposures?; (2) the
effects of concern: How serious are the health
effects?; (3) the size of the population at risk, as well
as the distribution of risk within the population.
The Agency has considered these factors in the case
of Hg and has concluded that the exposures above
the IDI described elsewhere in this chapter do not
constitute an unacceptable risk.
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above the 72nd percentile fish tissue
concentration.
Again, the likelihood of this occurring
is very small. Specific data on
concentrations in fish at waterbodies
frequented by subsistence fishing
populations has not been generated. To
get a sense of tribal location in relation
to utility-attributable Hg deposition
post-CAIR, we overlaid the 2000 Census
data on the location of Native American
populations (by census tract) on our
CMAQ models. Visual inspection of the
resulting map shows that the
overwhelming majority of tribal
populations live outside of areas most
impacted by utility-attributable Hg
deposition. See TSD. This suggests that
the 99th percentile of the utility
attributable methylmercury
concentrations is likely inappropriate as
an upper bound for Native American
exposures, further reducing the
probability that, post CAIR, and even
more so, post CAMR, an individual
Native American (who comprise a
significant percent of upper-bound
subsistence anglers) will exceed the RfD
(an IDI value greater than 1).
As discussed above, EPA received
comments on the consumption rates of
certain ethnic groups that are higher
than the subsistence angler
consumption rate that EPA relied on for
purposes of this analysis. Specifically,
members of the Ojibwe Great Lakes
Tribes commented that during their fall
spearing season they may consume
between 156 and 241 grams of fish per
day, and during their spring spearing
season, they may consume as much as
293 grams/day. For a number of reasons,
EPA found the data to be of limited
value. First, the data have not been peer
reviewed and thus EPA is reluctant to
rely on them for regulatory purposes.
Second, commenters did not include
information on annual average
consumption rates or the percentage of
those fish consumers that are women of
childbearing age. Third, based on EPA’s
information, the Tribes do not reside in
an area that appears to be significantly
impacted by utility Hg emissions. Thus,
despite having extremely high
consumption rates, there are no data in
the record that suggest that members of
the Tribe would be exposed above the
RfD (an IDI value greater than 1) as a
result of utility emissions. And again, as
discussed in greater detail below,
exposure above the RfD does not
necessarily equate to adverse effects.
3. The RfD Is An Appropriate Health
Benchmark
As described in section VII.B., in
general, the RfD is ‘‘an estimate (with
uncertainty spanning perhaps an order
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of magnitude) of a daily exposure to the
human population (including sensitive
subgroups) that is likely to be without
an appreciable risk of deleterious effects
during a lifetime.’’ 53 EPA’s RfD for
Methylmercury is 0.1 µg/kg bw/day,
which is 0.1 microgram of Hg per day
for each kilogram of a person’s body
weight. Since the most sensitive
subpopulations are factored into the
RfD, its use is thought to be protective
of all life stages without additional
uncertainty factors or adjustments. The
National Academy of Sciences (NAS)
reviewed the toxicological effects of
Methylmercury and concluded that
‘‘[o]n the basis of its evaluation, the
committee’s consensus is that the value
of EPA’s current RfD for
Methylmercury, 0.1 µg/kg per day, is a
scientifically justifiable level for the
protection of public health.’’ 54
EPA views the level of the RfD as
establishing the overall context for
assessing the health effects of ingesting
utility-attributable Methylmercury. As
noted above, in regulating HAPs that
constitute threshold pollutants, EPA has
stated that the risks associated with
exposures below the RfD generally
should be considered to be acceptable,
and that the emissions associated with
those exposures need not be regulated
further under section 112.
However, the RfD should not be
considered a bright line. At exposures
above the RfD, ‘‘adverse health effects
are possible,’’ but such exposures ‘‘[do]
not necessarily mean that adverse
effects will occur.’’ Indeed, the World
Health Organization has concluded that
a level equal to 2.3 times EPA’s
Methylmercury RfD is protective of
human health.
4. Risks Remaining After
Implementation of CAIR, and Even
More So After CAMR, Are Acceptable
Applying the risk factors identified
above to utility Hg emissions in the
112(n)(1)(A) context, EPA concludes
that utility Hg emissions remaining after
implementation of CAIR, and even more
so after CAMR, do not pose
unacceptable hazards to public health.
The overwhelming majority of the
general public and high-end fish
consumers (at least through the 99th
percentile of recreational anglers) are
not expected to be exposed above the
methylmercury RfD (an IDI value greater
than 1). While the possibility exists that
a very small group of people may be
exposed above the RfD (an IDI value
greater than 1), significant uncertainties
exist with respect to the existence and
53 See
54 See
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actual size of such a group. There are
also significant uncertainties concerning
the extent to which such exposure
might exceed the RfD (an IDI value
greater than 1) and whether exposure at
such levels would cause adverse effects.
See TSD. EPA intends to continue to
investigate the size and extent to which
certain groups might be exposed above
the RfD (an IDI value greater than 1),
and reserves the right to revisit its risk
acceptability determination if future
information warrants.
In the meantime, however, given the
size of the population, including
sensitive subpopulations, that after
implementation of CAIR and,
independently, CAMR, will be below
the RfD (an IDI value of less than 1); the
uncertainty of the size and the level to
which certain groups may be exposed
above the RfD (an IDI value greater than
1); the uncertainties that adverse effects
will be experienced by such groups
even at levels significantly above the
methylmercury RfD (an IDI value greater
than 1); and the nature of those
potential adverse effects (see TSD), EPA,
in its expert judgment, concludes that
utility Hg emissions do not pose hazards
to public health, and therefore that it is
not appropriate to regulate such
emissions under section 112.
5. Section 112(f) ‘‘Residual Risk’’
Analysis
Some commenters have argued that,
in determining whether utility HAPs
pose a hazard to public health, EPA is
bound to the mandates of section 112(f).
In other words, some have argued that
unless we can conclude that the
imposition of the CAA requirements on
utility HAP emissions ‘‘provide[s] an
ample margin of safety to protect public
health,’’ we must regulate utilities under
section 112. We disagree. Section
112(n)(1)(A) governs our decision
whether to regulate utilities under
section 112, not 112(f). Had Congress
intended us to apply the same standard,
it could have used identical words to
those found in section 112(f) or
referenced it directly. It did not. Instead,
Congress instructed EPA to assess
whether utility HAP emissions cause
‘‘hazards to public health.’’
Nevertheless, as explained above, in
assessing whether remaining utility
HAP emissions cause ‘‘hazards to public
health,’’ EPA used essentially the same
analysis that it would use in assessing
the human health prong of a 112(f)
determination.55 The factors laid out in
55 It should be noted that section 112(f) requires
consideration of effects on the environment in
addition to human health. In contrast, 112(n)
requires a narrower assessment.
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the ‘‘benzene’’ analysis for assessing
acceptable risk to public health under
112(f) are generally relevant to assessing
hazard under 112(n)(1)(A). Thus, even if
EPA were required to do a 112(f)
analysis in determining whether utility
Hg emissions pose public health
hazards, it is very likely that the
conclusion would have been the same,
even if the methodology might have
been slightly different.
As noted above, section 112(f)
expressly incorporates EPA’s pre-1990
two-part inquiry for evaluating what
level of emission reduction is needed to
provide an ample margin of safety to
protect public health. See CAA section
112(f)(2)(B) (incorporating EPA’s twopart ample margin of safety inquiry, set
forth at 54 FR 38044 (Sept. 14, 1989),
which implemented the requirements of
section 112 of the 1977 CAA). Under
this approach, we must first determine
what level is ‘‘acceptable’’ based
exclusively upon the Administrator’s
determination of the risk to health at a
particular emission level. Vinyl
Chloride, 824 F.2d at 1164.56 The Court
stressed, however, that ‘‘safe’’ in this
context does not mean ‘‘risk-free.’’
Rather, the Agency must make a
determination about what is safe ‘‘based
upon an expert judgment with regard to
the level of emission that will result in
an ‘‘acceptable’’ risk to health,’’ taking
into account the many every day
activities that entail health risks but are
not considered to be unsafe. Id. at 1165.
In this regard, we also note that
section 112(f) makes a distinction
between pollutants classified as
‘‘known, probable or possible
carcinogens’’ and other hazardous air
pollutants such as Hg. For possible
carcinogens, the Agency must set a
residual risk standard if ‘‘the individual
most exposed to emissions from a
source’’ is subject to a risk above a
certain level. This additional
requirement does not apply to other
hazardous air pollutants. Therefore, in
determining whether any level of Hg
emission is ‘acceptable’ under 112(f), we
would use the same basic approach we
have used in this case. Although we
56 The Vinyl Chloride court did note, however,
that under certain circumstances it might be
appropriate to combine the two steps into one.
Specifically, the court stated that ‘‘[i]f the
Administrator finds that some statistical
methodology removes sufficiently the scientific
uncertainty present in this case, then the
Administrator could conceivably find that a certain
statistically determined level of emissions will
provide an ample margin of safety. If the
Administrator uses this methodology, he cannot
consider cost and technological feasibility: these
factors are no longer relevant because the
Administrator has found another method to provide
an ‘ample margin’ of safety.’’ 824 F.2d at 1165, fn
11.
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would evaluate the risk to the maximum
exposed individual, which we
essentially did for purposes of assessing
the hazards posed by utility emissions
under section 112(n)(1)(A), we believe
that ‘‘the distribution of risks in the
exposed population, incidence, the
science policy assumption and
uncertainties associated with the risk
measures, and the weight of evidence
that a pollutant is harmful to health are
[also] important factors to be
considered’’ in making a decision as to
whether a given level of emissions is
acceptable. 54 FR at 38044.
Then, ‘‘[i]n the ample margin decision
[the second step], the Agency again
considers all of the health risk and other
health information considered in the
first step. Beyond that information,
additional factors relating to the
appropriate level of control will also be
considered, including costs and
economic impacts of controls,
technological feasibility, uncertainties,
and any other relevant factors.’’ 54 FR
38046.
As explained in section H.3. above,
applying the general principles
articulated in the Vinyl Chloride
decision and the benzene rule, the
Agency has concluded that power plant
Hg emissions remaining after CAIR, and
even more so after CAMR, do not pose
hazards to public health. This
determination was based on health
considerations alone, as would be the
case under the first step of a 112(f)
analysis. Under the second step of a
112(f) analysis, we would then consider
both the benefits and costs of further
emission reductions. Based on what we
know about the uncertainties and nature
of the potential adverse effects
associated with Hg exposure, the extent
to which the public, including sensitive
subpopulations, is exposed to Hg, and
the extent to which such exposure could
be reduced by further reducing Hg
emissions from U.S. power plants, we
have concluded that the cost of
requiring further reductions in Hg
emissions from power plants would
significantly outweigh any benefits.
Therefore, if we were proceeding under
section 112(f), we would likely
conclude that CAIR, and even more so
CAMR, not only protects public health,
but does so with an ‘‘ample margin of
safety.’’
I. The Final CAMR Will Not Lead to
Localized ‘‘Utility Hot Spots’’
1. What Is a ‘‘Utility Hot Spot’’?
As we said in the preamble to the
proposed rule, Hg emissions from power
plants sometimes are deposited locally
near the plant (i.e., within 25 km),
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specifically emissions of oxidized and
particulate Hg. Nearby waterbodies may
be a source of fish consumption for
recreational and/or subsistence fishers,
and thus local Hg deposition in nearby
waterbodies could be a source of what
some refer to as ‘‘hot spots.’’ In the
proposed rule, we suggested that a
‘‘power plant may lead to a hot spot if
the contribution of the plant’s emissions
of Hg to local deposition is sufficient to
cause blood Hg levels of highly exposed
individuals near the plant to exceed the
RfD.’’ (See 69 FR 4702.)
Based on additional analysis and
consideration of the ‘‘hot spot’’ issue
and to ensure that stakeholders have a
common understanding of how EPA
uses the term, we define a ‘‘utility hot
spot’’ as ‘‘a waterbody that is a source
of consumable fish with Methylmercury
tissue concentrations, attributable solely
to utilities, greater than the EPA’s
Methylmercury water quality criterion
of 0.3 mg/kg.’’ We believe that the water
quality criterion is an appropriate
indicator of a ‘‘hot spot,’’ given that the
Methylmercury exposure pathway of
greatest concern is fish consumption
and that the water quality criterion was
back calculated from the Methylmercury
RfD using a high-end fish consumption
rate.
2. EPA Does Not Believe That There
Will Be Any Hot Spots After
Implementation of CAIR and CAMR
As explained elsewhere in this
preamble and in the TSD, for purposes
of today’s notice, EPA modeled utility
Hg deposition, before and after
implementation of CAIR and CAMR,
using the Community Multi-Scale Air
Quality (‘‘CMAQ’’) model, a threedimensional eulerian grid model.
CMAQ is the most sophisticated Hg
dispersion model in existence. It uses a
‘‘one-atmosphere’’ approach and
addresses the complex physical and
chemical interactions known to occur
among multiple pollutants in the free
atmosphere.57 The spatial resolution
(i.e., the ability to observe concentration
or depositional gradients/differences) of
the gridded output information from
CMAQ for purposes of this analysis is
36 km.
We believe that this an appropriate
scale given the exposure pathway. First,
because much of the Hg deposited on
57 In simulating the transport, transformation, and
deposition of pollutants, CMAQ resolves 14 vertical
layers in the atmosphere, and employs finer-scale
resolution near the surface of the boundary layer to
simulate deposition to both terrestrial and aquatic
ecosystems. CMAQ atmospheric transport is
defined using a higher-order meteorological model,
commonly the Fifth-Generation Pennsylvania State
University/National Center for Atmospheric
Research mesoscale model (MMM5).
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the watershed of different ecosystems
will eventually enter waterbodies
through subsurface inflow and runoff,
we consider a watershed scale analysis
to be more appropriate than finer scale
resolution that may only describe direct
inputs to surface waters. Second, in
larger waterbodies (i.e., the Great Lakes)
where there is substantial fishing
activity, the higher trophic level fish
species consumed by humans are likely
migratory and the accumulation of Hg
by these species will represent an
aggregated signal from deposition over a
wider area (e.g., the entire waterbody
within a watershed.) Since we are
concerned about the cumulative dose
over weeks and months from repetitive
consumption of fish containing
methylmercury, this fishing behavior
should be considered in the exposure
pathway. Based on the above
considerations, we conclude that the
HUC–8 watershed is the appropriate
unit of measure for analysis. While this
analysis covers the vast majority of the
U.S. population that may be exposed to
emissions from U.S. power plants, we
acknowledge that there are inherent
uncertainties at the extreme tails of the
exposure distribution. We continue to
advance the state of the science and the
associated models to better understand
the tail of this exposure distribution.
As discussed in section VII.D. of
today’s notice, EPA used fish tissue data
from the National Listing of Fish and
Wildlife Advisories and the National
Fish Tissue Survey to determine
Methylmercury fish tissue
concentrations for numerous sample
sites throughout the country. We then
used CMAQ to determine the amount of
utility Hg deposition, in conjunction
with Mercury Maps (which associates
an increment of change in Hg deposition
with an equal change in Methylmercury
fish tissue concentrations) to predict
what fish concentrations at those
sample sites would be after
implementation of CAIR and CAMR. As
discussed in section VII.E., those
analyses conclude that none of the
sample sites will exceed, as a result of
utility emissions, the water quality
criterion of 0.3 mg/kg. In fact, our
analysis shows that fish tissue
Methylmercury concentrations
attributable to utility Hg emissions will
be significantly below the water quality
criterion. By 2020, after CAIR, levels at
the 50th, 90th, 99th percentiles and
maximum value sample site are
predicted to be 0.01, 0.03, 0.10, and 0.25
mg/kg, respectively. After CAMR, levels
at the 50th, 90th, 99th percentiles and
maximum value sample site are
predicted to be 0.01, 0.03, 0.09, and 0.19
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mg/kg, respectively. Therefore, based on
the information available to us at this
time, our analyses indicate utility Hg
emissions, after implementation of
either CAIR or CAMR, will not result in
‘‘hot spots.’’
EPA conducted a similar analysis in
its 1998 Utility Report to Congress
(‘‘Utility Study’’) using the Industrial
Source Complex Version 3 (‘‘ISC3’’)
model. (See TSD) EPA analyzed four
model plants representing four utility
boilers: Large coal-fired, medium coalfired, small coal-fired, and medium oilfired. Each of these plants was also
modeled at two generic sites: A humid
site east of the 90 degrees west
longitude, and a more arid site west of
the 90 degree west longitude. (See
Utility Study at 7–29). Hg deposition
was modeled at a hypothetical lake
located at three distances for each
model site: 2.5, 10, and 25 km. The
results of that analysis showed that
under only one modeled scenario was
the Methylmercury water quality
criterion exceeded. Specifically, the
model predicted that a hypothetical lake
located 2.5 km from a large eastern coalfired utility would experience
Methylmercury fish tissue concentration
of 0.43 mg/kg. None of the other 23
model facilities/lake combinations
exceeded the water criterion. (See
Utility Study at 7–37).
For a number of reasons more fully
explained in our TSD, even though only
one facility/lake combination exceeded
the water quality criterion, we believe
that the analysis done for the 1998
Utility Study was conservative and,
hence, over predicted near-field Hg
deposition and corresponding fish
tissue concentrations in almost all
situations. That analysis was a screening
analysis and thus was conservative by
design. For example, it did not
incorporate a sophisticated treatment of
the atmospheric chemistry and phasetransition behavior of Hg, as we have
included in our CMAQ analysis, and
our understanding of wet and dry
deposition processes for Hg has
improved significantly since then. As a
result, we judge that the CMAQ model
results represent a more accurate
representation of near-field Hg impacts
than can be obtained using the ISC3
modeling approach. See the discussion
above about why the CMAQ model
appropriately represents near-field
deposition.
There are other factors that lead EPA
to conclude that the Utility Study
analysis overstated fish-tissue
methylmercury concentrations in most
situations. Based on the BAFs
considered, the hypothetical ecosystem
described in the RTC is more sensitive
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than three out of four ecosystems
chosen for the case studies (see Table 4–
6, page 25 of Ecosystem Scale Modeling
for Mercury Benefits Analysis) and is
less sensitive than one (Lake Barco).
Comparing these case studies to
empirically derived BAFs characterized
by the Office of Water indicates that
modeled fish tissue responses in three
of four case studies had empirically
derived BAFs that fell between the 5th
and 50th percentiles of the geometric
mean of field-measured BAFs for
trophic level 4 species obtained from
the published literature (EPA 2000). The
model ecosystem described in the RTC
fell between the 50th and 95th
percentile for BAFs, and one of the case
studies (Lake Barco) exceeded the 95th
percentile.
Some limitations to the BAF approach
deserve mention. Because
Methylmercury concentrations in the
water column are highly variable,
empirically-derived BAFs are inherently
underdetermined and have limited
predictive power. A more credible
approach based on our current
knowledge is to forecast changes in fish
Hg concentrations using information on
the food-web dynamics
(‘‘bioenergetics’’) of different
ecosystems. Such a model (BASS) was
applied in one of the case studies
described in Chapter 3 of the RIA for
CAMR, and showed that while the BAFs
calculated from the outputs of the
bioenergetics-based bioaccumulation
model were within a factor of 2 of the
empirically derived BAF used in the
SERAFM model, the empirically
derived fish Hg concentrations were
more conservative than the BASS model
for this one ecosystem. (See TSD). Thus,
the above information suggests that our
RTC analysis may have over predicted
fish-tissue methylmercury
concentrations in many ecosystems that
could be impacted by Hg deposition
from U.S. power plants. However, it is
important to note that fish tissue
methylmercury concentrations due to
power plants may be higher in some
ecosystems (for example, ecosystems
similar to Lake Barco described in Ch.
3 of the CAMR RIA).
For all the above described reasons,
we think our current modeling approach
as described in the TSD provides for a
more advanced, state-of-the-science
assessment of the atmospheric fate,
transport, deposition, and cycling of Hg
through the environment than the
modeling approach used in the Utility
Study. For these reasons, we have no
evidence that utility Hg emissions after
CAIR (and even more so after CAMR)
will result in hot spots.
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Based on our experience with the
Title IV acid rain program and our
modeling using IPM, we believe that the
cap-and-trade approaches adopted
under CAIR and CAMR will reduce Hg
exposure in most areas and create strong
economic incentives for the reduction of
Hg emissions in the future.
First, modeling runs suggest that large
coal-fired utilities contribute more to
local Hg deposition than medium-sized
and smaller coal-fired utilities.58
However, under a cap-and-trade system,
large utilities are more likely to overcontrol their emissions and sell
resulting emission allowances than
smaller utilities, which are less likely to
be the source of a local hot spot. Under
basic utility economics of capital
investment, when capital is limited, upfront capital costs of control equipment
are significant, and where emissionremoval effectiveness (measured in
percentage of removal) is unrelated to
plant size, it makes more economic
sense for a company to allocate
pollution-prevention capital to its larger
facilities where more allowances can be
earned, than to its smaller ones. In other
words, we would expect economies of
scale of pollution control investment to
be made at larger plants. Moreover,
newer plants tend to be larger. Since
newer plants have longer expected
lifetimes, providing a longer return on
investment, we would expect this to be
an incentive for these larger facilities to
choose to control and sell credits.
Indeed, as part of its analysis of the
President’s 2003 Clear Skies initiative,
EPA analyzed Hg emissions reductions
under a cap-and-trade mechanism. In
the Clear Skies example, the greatest
emissions reductions were projected to
occur at the electric generating sources
with the highest Hg emissions. This
pattern is similar to that observed in the
SO2 emissions trading program under
the Acid Rain Program. Under Clear
Skies, compared to a base case of
existing programs, Hg 2∂ emissions
(which tend to be deposited locally, i.e.,
within 25 kilometers) from power plants
located up to 10 kilometers from a water
body were projected to decrease by over
60 percent by 2020.
Second, the types of Hg that are
deposited locally—Hg 2∂ and Hgp—are
controlled by the same equipment that
controls PM, SO2, and NOX. Thus, as
utilities invest in equipment to comply
with EPA’s new PM and ozone
58 Indeed, the one model utility in the Utility
Study analysis that exceeded the water quality
criterion at a hypothetical lake within 2.5 km was
an eastern large coal-fired utility. Given the
tendencies for larger facilities to control under a
cap-and-trade system, we do not anticipate that
larger plants will cause localized hot spots.
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standards (e.g., the CAIR rule that was
signed on March 10, 2005 and new State
Implementation Plans (SIPs) for PM and
ozone), the Agency expects ‘‘co-benefit’’
Hg reductions.
Moreover, EPA’s IPM modeling for
today’s action predicts that larger
emitters generally are expected to
reduce the most, as was our experience
with the Acid Rain Program. Through
our CMAQ modeling, we further predict
utility-attributable deposition
reductions in areas where hotspots
would otherwise potentially occur. As
described in section VII.E., the median
deposition level is reduced by only 8
percent when utilities emissions are
zeroed out in 2001, but in areas with the
highest deposition levels, zeroing out
utilities reduces the 99th percentile
deposition level by 15 percent. After
implementation of CAIR in 2020, areas
with high levels of utility deposition
receive a larger reduction in utilityattributable Hg deposition relative to
areas with a relatively small level of
utility-attributable deposition.
For all these reasons, we do not
anticipate that our final CAMR rule will
result in local Hg hot spots; to the
contrary, we anticipate that our capand-trade CAMR will actually eliminate
hot spots that may have previously
existed.
In addition to reductions required by
the CAIR and CAMR caps, states have
the authority to address local healthbased concerns separate from these
programs. Although more stringent state
regulations would reduce the flexibility
of a cap-and-trade system, states
nevertheless have such authority.
3. Continued Evaluation of Utility Hg
Emissions
For all the reasons discussed above
and elsewhere in this preamble, EPA
does not believe that CAIR or CAMR
will result in utility-attributable hot
spots. That said, we recognize that even
our state-of-the-art models and inputs
have certain limitations that make it
impossible for us to definitively
conclude that there are no
circumstances under which a hot spot
could result even after full
implementation of CAIR and CAMR.
However, in order for a hot spot to
occur, there would have to be an
alignment of key environmental factors,
such as meteorology, deposition, and
ecosystem processes in conjunction
with a large uncontrolled near-field
utility unit or a collection of such units.
The likelihood of these factors
converging is remote. Nevertheless, we
intend to monitor this situation closely
and continue to advance the state of the
science of Hg transport and fate. In that
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regard, if we receive new information
that raises the possibility of utilityattributable hotspots, we will evaluate
the situation and take appropriate
action.
We believe that we have the authority
under the Act to address future hotspots
appropriately. Indeed, today we have
identified other authorities under the
CAA through which we can obtain Hg
reductions from coal-fired Utility
Units—either by regulating Hg directly,
or indirectly as the result of co-benefits.
The 1998 Utility Study also identifies
other requirements of the Act with
which Utility Units must comply that
can result in HAP reductions, including
Hg. Because we do not currently have
any facts before us that would lead us
to conclude that utility-attributable
hotspots exist, we do not at this time
reach any conclusion as to which
statutory authority we would use to
address such a fact-specific situation
because it necessarily depends on the
facts.
For example, if in the future we
determine that utility-attributable
hotspots exist and that those hotspots
occur as the result of Hg emissions from
coal-fired Utility Units, we may
promulgate a tighter section 111
standard of performance, provided we
determine the technology can achieve
the contemplated reductions. We could
revise the standard of performance by
adjusting the cap-and-trade program to
limit trading by high-emitting Utility
Units. As the DC Circuit has recognized,
we have discretion to weigh the
statutory factors identified in section
111(a), which include cost, in setting a
standard of performance. Lignite Energy
Council v. EPA, 198 F.3d 930 (DC Cir.
1999). We therefore believe that under
section 111, we can evaluate the cost of
emission reduction in the context of the
identified hotspots, and we may
reasonably conclude that the additional
cost of a more stringent standard is
appropriate in light of the health
concern associated with the hotspots.
Alternatively, we may in the future
identify utility-attributable hotspots and
determine that such hotspots can be
addressed by virtue of Hg co-benefits
control achieved through the
promulgation of other requirements.
Thus, although we cannot conclude
today which statutory authority we
would implement to address utilityattributable hotspots because that
determination necessarily hinges on the
facts associated with the identified
hotspots, we do conclude that were
such a situation to occur, we believe
that EPA has adequate authority to
address any such situation that may
arise in the future.
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J. The Global Pool of Hg Emissions
1. Background
As explained above, Hg is emitted
into the environment in different ways.
About one-third of the Hg in the
atmosphere is from human-caused
activities (‘‘anthropogenic’’), one-third
is from natural processes (such as
volcanic eruption, groundwater seepage
and evaporation from the oceans), and
one-third constitutes re-emitted
emissions, which is Hg from humancaused activities or natural processes
that is emitted into the atmosphere,
deposited and then re-emitted into the
atmosphere. United States
anthropogenic Hg emissions are
estimated to account for about three
percent of the global pool of Hg
emissions, and United States
(‘‘domestic’’) utilities are estimated to
account for about one percent of that
total global pool. See Utility Study at 7–
1 to 7–2, 69 FR at 4657–58 (January 20,
2004). The global pool therefore
includes all human-caused activities
that occur both within the United States
and abroad, all emissions that result
from natural processes anywhere in the
world, and re-emitted Hg.
To place the Hg emissions from
domestic Utility Units in context, EPA
modeled different scenarios that analyze
the effect of domestic utility Hg
emissions in the context of the global
pool. We describe that modeling in
detail above.
Our modeling shows that in virtually
all instances, the utility-attributable
methylmercury levels are a very small
fraction of the overall methylmercury
levels. For 16 percent of the modeled
sites, overall levels of methylmercury in
fish tissue in 2020 are projected to be
above the 0.3 mg/kg water quality
criterion. At the 90th percentile, in
2020, after implementation of CAIR,
overall levels are projected at 0.79 mg/
kg, and at the 99th percentile, at 1.64.
The greatest fraction of these
methylmercury levels are attributable to
non-air sources, including mines and
chloralkali plants, and uncontrollable
air sources, including international
emissions from industrial and utility
sources. In virtually all of these
instances, the Utility-attributable
methylmercury levels are a very small
fraction of the overall methylmercury
levels. For the highest 10 percent of
utility-attributable methylmercury fish
tissue levels, utility-attributable
methylmercury accounted for a
maximum of 9 percent of total
methylmercury concentrations, and an
average of only 4 percent. Clearly, even
at locations with high levels of utility
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Hg deposition, other sources of Hg
contribute most of the methylmercury.
2. Even Examining Utility Hg Emissions
in the Context of the Global Pool, We
Cannot Conclude That It Is Appropriate
to Regulate Coal-Fired Utility Units
Under CAA Section 112
Our conclusions in sections VI.J and
VI.K above are based solely on our
analysis of Hg emissions from coal-fired
Utility Units. See generally 65 FR
79,826–29 (explaining that Hg from
coal-fired units is the HAP of greatest
concern); Utility Study, ES–27 (same).
We focused our analysis in this regard
because EPA has interpreted section
112(n)(1)(A) to examine the hazards to
public health that are ‘‘a result of’’
Utility Units. See CAA section
112(n)(1)(A). As explained in section III
above, the focus in section 112(n)(1)(A)
on emissions ‘‘result[ing]’’ from Utility
Units is significant, particularly when
contrasted against other provisions of
the Act, such as section 110(a)(2)(D). In
section 110(a)(2)(D), Congress sought to
regulate any air pollutant that will
‘‘contribute to’’ nonattainment. Thus,
under section 110(a)(2)(D), we can
regulate a pollutant if it ‘‘contributes’’ to
a nonattainment problem, but does not
itself cause the problem. EPA has
concluded that section 112(n)(1)(A) is
different, where Congress directed EPA
to study the hazards to public health
‘‘reasonably anticipated to occur as a
result of emissions of’’ Utility Units.
(emphasis added)
Moreover, Congress’ focus on the
hazards to public health resulting from
Utility Units may reflect Congress’
recognition of the unique situation
posed by Hg, which is that Hg emissions
from domestic utilities represent less
than one percent of the global pool.
Indeed, Congress specifically addressed
Hg in other provisions of section 112(n).
For example, under section 112(n)(1)(B),
Congress required EPA to complete a
study addressing Hg emissions from
Utility Units and other sources of Hg.
See CAA section 112(n)(1)(B); see also
CAA Section 112(n)(1)(C) (requiring
National Institute of Environmental
Health Sciences to determine the
threshold level of Hg exposure below
which adverse human health effects are
not expected to occur).
Nevertheless, even were we to
examine hazards to public health on a
broader scale by focusing on the global
Hg pool, our conclusion (discussed
above in Section IV.A.) that it is not
appropriate to regulate coal-fired Utility
Units under section 112 on the basis of
Hg emissions would be the same. Our
analyses in support of that conclusion
would differ, however, because we
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would be assessing whether it is
appropriate to regulate Utility Units
under section 112 by reference to a
different level of Hg emissions. As
explained in section III of this notice,
we have discretion, in determining
whether regulation under section 112 is
appropriate, to consider other factors
and, in particular, any unique facts and
circumstances associated with the HAP
emissions at issue. Here, the unique
circumstance is that domestic Utility
Units represent only one percent of the
global pool. Our modeling shows that
were we to prohibit all Hg emissions
from domestic utilities in this country,
such regulation would result in only a
very small improvement in
methylmercury levels in the
waterbodies that exceed the
methylmercury water quality criteria.
Therefore, precluding all Hg emissions
from coal-fired powerplants would, in
effect, force such plants out of business,
yet reduce virtually none of the risks to
public health stemming from the global
Hg pool.
In these circumstances, we find that it
is not appropriate to regulate coal-fired
Utility Units under section 112 on the
basis of the global Hg pool because the
health benefits associated with such
regulation would be nominal and the
costs extreme. It is also not appropriate
to regulate Hg emissions from coal-fired
utility units remaining after imposition
of the requirements of the Act because
the global sources contributing most
significantly to the remaining public
health hazards are not domestic utilities
and the sole question before us under
section 112(n)(1)(A) is whether it is
appropriate to regulate Utility Units
under section 112 of the Act.59
K. Further Study
The behavior of Hg in the atmosphere
and in aquatic systems, and the human
59 See
36 Cong. Rec. S16895, S16899 (daily ed.
Oct. 27, 1990) (Statement of Senator Burdick,
member of the Conference Committee and
Chairman of the Committee on Environment and
Public Works) (‘‘Under section 112(n) utility
emissions are exempt from air toxics regulation
until studies are completed and the Administrator
determines, based on the studies, that air toxics
regulation is warranted. The hazardous substance of
greatest concern here is Hg. The Senate bill required
Hg reductions from coal-fired units. The Senate
provision could not be sustained by the scientific
facts. What little is known of Hg movement in the
biosphere, suggests that its long residence time
makes it a long-range transport problem of
international or worldwide dimensions. Thus, a full
control program in the United States requiring dry
scrubbers and baghouses to control Hg emissions
from coal-fired power plants would double the
costs of acid rain control with no expectation of
perceptible improvement in public health in the
United States. I am pleased the conferees adopted
the House provision on hazardous air pollutants
with respect to Utility Units.’’)
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health effects of Hg are areas of much
interest and activity within the
scientific and health research
communities. In addition, our ability to
quantify and value the effects that
changes in Hg releases may have to
human health is continuing to evolve.
Furthermore, technologies and
techniques for limiting Hg emissions
from power plants are also rapidly
advancing. EPA will continue to
monitor developments in all these areas,
as well as continuing its own efforts to
advance the state of the science. One of
the benefits of today’s approach is that
it provides a flexible structure that
could be modified to accommodate new
information should it become available.
VII. EPA’S Authority to Regulate HAP
From Utility Units Under CAA Section
111
As explained in sections IV and VI
above, we conclude today, among other
things, that EPA’s December 2000
appropriate and necessary finding
lacked foundation because it failed to
consider the HAP reductions that could
be obtained through implementation of
section 111, and therefore whether it
was ‘‘necessary’’ to regulate under
section 112. We decide today that it is
not ‘‘necessary’’ to regulate utility HAPs
under section 112, in particular because
of our authorities to effectively reduce
utility HAPs under CAA sections
110(a)(2)(D) and 111.60
We describe below the regulatory
scheme under section 111 and EPA’s
authority to regulate HAP emissions
under that section. We also describe the
recently issued Clean Air Mercury Rule
(‘‘CAMR’’), which implements CAA
section 111. Finally, we demonstrate
that the CAMR rule, once implemented,
will result in levels of Hg emissions
from coal-fired Utility Units that pose
no hazards to public health.
A. Overview of the Requirements of
Section 111
CAA section 111 creates a program for
the establishment of ‘‘standards of
performance.’’ A ‘‘standard of
performance’’ is ‘‘a standard for
emissions of air pollutants which
reflects the degree of emission
60 We also conclude today, as discussed in detail
above, that Hg emissions from coal-fired Utility
Units remaining after implementation of section
110(a)(2)(D) do not result in hazards to public
health. See Sections V and VI. Section 111, which
is the focus of this section of the preamble,
constitutes an independent basis for our actions
today, because that provision, once implemented,
will effectively address any Hg emissions from coalfired Utility Units, and for that reason, Hg
emissions from coal-fired Utility Units that remain
‘‘after imposition of the requirements of th[e] Act
do not result in hazards to public health.’’ CAA
Section 112(n)(1)(A).
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limitation achievable through the
application of the best system of
emission reduction, which (taking into
account the cost of achieving such
reduction, any nonair quality health and
environmental impacts and energy
requirements), the Administrator
determines has been adequately
demonstrated.’’ CAA section 111(a)(1).
For new sources, EPA must first
establish a list of stationary source
categories, which, the Administrator has
determined ‘‘causes, or contributes
significantly to, air pollution which may
reasonably be anticipated to endanger
public health or welfare.’’ CAA section
111(b)(1)(A)). EPA must then set federal
standards of performance for new
sources within each listed source
category. (CAA section 111(b)(1)(B)).
Like section 112(d) standards, the
standards for new sources under section
111(b) apply nationally and are effective
upon promulgation. (CAA section
111(b)(1)(B)).
Existing sources are addressed under
section 111(d) of the CAA. EPA can
issue standards of performance for
existing sources in a source category
only if it has established standards of
performance for new sources in that
same category under section 111(b), and
only for certain pollutants. (CAA section
111(d)(1)). Section 111(d) authorizes
EPA to promulgate standards of
performance that states must adopt
through a SIP-like process, which
requires state rulemaking action
followed by review and approval of
state plans by EPA. If a state fails to
submit a satisfactory plan, EPA has the
authority to prescribe a plan for the
state. (CAA section 111(d)(2)(A)).
B. EPA’s Authority to Regulate HAP
Under Section 111
Section 111(b) covers any category of
sources that causes or contributes to air
pollution that may reasonably be
anticipated to endanger public health or
welfare and provides EPA authority to
regulate new sources of such air
pollution. EPA included Utility Units
on the section 111(b) list of stationary
sources in 1979 and has issued final
standards of performance for new
Utility Units for pollutants, such as
NOX, PM, and SO2. See 44 FR 33580;
June 11, 1979; Subpart Da of 40 CFR
Part 60. Nothing in the language of
section 111(b) precludes EPA from
issuing additional standards of
performance for other pollutants,
including HAP, emitted from new
Utility Units. Moreover, nothing in
section 112(n)(1)(A) suggests that
Congress sought to preclude EPA from
regulating Utility Units under section
111(b). Indeed, section 112(n)(1)(A)
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provides to the contrary, in that it calls
for an analysis of utility HAP emissions
‘‘after imposition of the requirements of
th[e] Act,’’ which we have reasonably
interpreted to mean those authorities
that EPA reasonably anticipated at the
time of the Study would have reduced
utility HAP emissions.
EPA received numerous comments
concerning its authority under section
111 to regulate HAP from Utility Units.
Those comments focused largely on
EPA’s authority to regulate existing
units under section 111(d). As
explained below, EPA has reasonably
interpreted section 111(d) as providing
authority to regulate HAP from existing
Utility Units.
Unlike section 111(b), section 111(d)
specifically references CAA section 112.
The import of that reference is not clear
on the face of Public Law 101–549,
which is the 1990 amendments to the
CAA, because the House and Senate
each enacted a different amendment to
section 111(d). The Conference
Committee never resolved the
differences between the two
amendments and both were enacted into
law as part of section 111(d). EPA is
therefore confronted with the highly
unusual situation of an enacted bill
signed by the President that contains
two different and inconsistent
amendments to the same statutory
provision.
1. Overview of the Two Amendments in
Section 111(d)
An important starting point for
evaluating the two amendments to
section 111(d) in 1990 is the 1977 Act.
Section 111(d) of the 1977 CAA
provides, in pertinent part:
The Administrator shall prescribe
regulations which shall establish a procedure
similar to that provided by section 7410 of
this title under which each State shall submit
to the Administrator a plan which (A)
establishes standards of performance for any
existing source for any air pollutant (i) for
which air quality criteria have not been
issued or which is not included on a list
published under section 7408(a) or
7412(b)(1)(A) of this title, but (ii) to which a
standard of performance under this section
would apply if such existing source were a
new source. * * *
42 U.S.C.A. 7411(d) (West 1977); Public
Law 95–95. The above language
provides that standards of performance
under section 111(d) cannot be
established for any pollutant that is
listed as a ‘‘hazardous air pollutant’’
under section 112(b)(1)(A) of the 1977
CAA.
In 1990, Congress significantly
amended the CAA. Among other things,
it significantly amended section 112, it
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enacted Title IV of the CAA, which
includes numerous provisions that are
directly applicable to Utility Units, and
it amended section 111(d). Both the
House and the Senate bills included
different amendments to section 111(d),
and both of those amendments were
enacted into law.
The first amendment, which is the
House amendment, is contained in
section 108(g) of Public Law 101–549.
That section amends section
111(d)(1)(A)(i) of the 1977 CAA by
striking the words ‘‘or 112(b)(1)(A)’’
from the 1977 CAA and inserting in its
place the following phrase: ‘‘or emitted
from a source category which is
regulated under section 112.’’ The
second amendment to section 111(d),
which is the Senate amendment, is
labeled a ‘‘conforming amendment’’ and
is set forth in section 302 of Public Law
101–549. That section amends CAA
section 111(d)(1) of the 1977 CAA by
striking the reference to ‘‘112(b)(1)(A)’’
and inserting in its place ‘‘112(b).’’ The
two amendments are reflected in
parentheses in the Statutes at Large as
follows:
The Administrator shall prescribe
regulations which shall establish a procedure
similar to that provided by section 7410 of
this title under which each State shall submit
to the Administrator a plan which (A)
establishes standards of performance for any
existing source for any air pollutant (i) for
which air quality criteria have not been
issued or which is not included on a list
published under section 7408(a) (or emitted
from a source category which is regulated
under section 112) [House amendment,] (or
112(b)) [Senate Amendment,] but (ii) to
which a standard of performance under this
section would apply if such existing source
were a new source. * * *
The United States Code does not
contain the parenthetical reference to
the Senate amendment, as set forth in
section 302 of Public Law 101–549. The
codifier’s notes to this section of the
Official Committee Print of the executed
law state that the Senate amendment
‘‘could not be executed’’ because of the
other amendment to section 111(d)
contained in the same Act. The United
States Code does not control here,
however. The Statutes at Large
constitute the legal evidence of the laws,
where, as here, Title 42 of the United
States Code, which contains the CAA,
has not been enacted into positive law.
See 1 U.S.C. 204(a); United States v.
Welden, 377 U.S. 95, 98 n.4 (1964);
Washington-Dulles Transportation Ltd.
v. Metropolitan Washington Airports
Auth., 263 F.3d 371, 378 (4th Cir. 2001).
We did not receive any comments
disputing either that the Statutes of
Large constitute the legal evidence of
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the laws in this case, or that the 1990
Act contains two different amendments
to the same statutory provision.61
2. Overview of Legislative History
As we indicated in the proposal, there
is scant legislative history concerning
the two amendments to section 111(d).
The most persuasive legislative history
that is relevant to our task of
interpreting and reconciling the House
and Senate amendments to section
111(d) is the final Senate and House
bills. Those bills reflect significantly
different treatment of Utility Units
under section 112, as well as different
amendments to section 111(d).
We begin our analysis with Senate bill
1630, as passed by the Senate on April
3, 1990. That bill included a provision
concerning Utility Units. See generally
Section 301 (hazardous air pollutants),
A Legislative History of the Clean Air
Act Amendments of 1990 (‘‘Legislative
History’’), Vol III, at 4431–33 (Nov.
1993). Under that provision, EPA was to
conduct a study on the health and
environmental effects of utility HAP
emissions within three years of
enactment of the statute. The Senate Bill
also required EPA to promulgate section
112(d) emissions standards for Utility
Units within five years of enactment of
the statute. The Senate bill further
required EPA to place the study on
utility HAP emissions in the docket for
the section 112(d) rulemaking for Utility
Units. Finally, the Senate bill, in a
section labeled ‘‘conforming
amendments,’’ amended section 111(d)
by striking the reference to
‘‘112(b)(1)(A)’’ in the 1977 Act and
replacing it with ‘‘112(b).’’ See generally
Section 305 (conforming amendments),
Legislative History, Vol III, at 4534.
The final bill that passed the House in
May 1990 stands in stark contrast to the
Senate Bill. The House Bill included
section 112(l), entitled ‘‘Electric
Utilities.’’ See generally Section 301
(hazardous air pollutants), Legislative
History, Vol II, at 2148–49. That
provision is identical to section
112(n)(1)(A). See 104 Stat. 2558. The
House bill also amended section 111(d)
by replacing the words ‘‘or
112(b)(1)(A)’’ with ‘‘or emitted from a
source category which is regulated
under section 112.’’ See Legislative
History, Vol. II, at 179.
Finally, the House provision
concerning Utility Units is the provision
that was enacted into law as section
112(n)(1)(A). The Senate approach to
61 Although the notes accompanying the Official
Committee Print do not interpret with the force of
law, their conclusion about the appropriate effect to
give these conflicting amendments is evidence that
EPA’s conclusion is reasonable.
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regulating Utility Units under section
112 did not prevail. See Legislative
History, Vol. I at 1451.
3. EPA’s Interpretation of the Two
Amendments to Section 111(d)
Neither we, nor commenters, have
identified a canon of statutory
construction that addresses the specific
situation with which we are now faced,
which is how to interpret two different
amendments to the exact same statutory
provision in a final bill that has been
signed by the President. The canon of
statutory construction that calls for
harmonizing conflicting statutory
provisions, where possible, and
adopting a reading that gives some effect
to both provisions is not controlling
here because that canon applies where
two provisions of a statute are in
conflict, not where two amendments to
the same statutory provision are in
conflict. Nevertheless, we have
attempted to follow the general
principles underlying this canon of
construction. We also rely on the
legislative history noted above as
support for our interpretation of the two
amendments to section 111(d).
Turning first to the House
amendment, we noted at proposal that
a literal reading of that amendment is
that a standard of performance under
section 111(d) cannot be established for
any air pollutant—HAP and non-HAP—
emitted from a source category regulated
under section 112. See 69 FR 4685.
Certain commenters disagreed with our
reading. They argue instead that a literal
reading of the House amendment is that
EPA cannot regulate under section
111(d) any HAP that is emitted from any
source category regulated under section
112. This reading modifies the plain
language of section 111(d), as amended
by the House in 1990, in significant
respects. First, it changes the terms ‘‘any
pollutant’’ to ‘‘HAP,’’ and second, it
changes the phrase ‘‘a source category,’’
to ‘‘any source category’’ and therefore
commenters’’ reading of the amendment
cannot be characterized as a ‘‘literal’
reading.
Section 111(d), as amended by the
House, specifically provides:
Each State shall submit to the Administrator
a plan which (A) establishes standards of
performance for any existing source for any
air pollutant * * * which is not emitted from
a source category which is regulated under
section 112.
We interpret this language to mean
that EPA cannot establish a standard of
performance under CAA section 111(d)
for any ‘‘air pollutant’’—including both
HAP and non-HAP—that is emitted
from a particular source category
regulated under section 112. Thus,
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under our interpretation, if source
category X is ‘‘a source category’’
regulated under section 112, EPA could
not regulate HAP or non-HAP from that
source category under section 111(d).
This interpretation reflects the
distinction drawn in section 111(d), as
amended by the House, between ‘‘any
pollutant’’ and ‘‘a source category.’’ The
phrase ‘‘any pollutant’’ existed prior to
the 1990 amendments and therefore it
can be reasonably assumed that when
the House amended section 111(d) in
1990, it intentionally chose the words
‘‘a source category,’’ as opposed to ‘‘any
source category. Although we recognize
that the phrase ‘‘a source category’’ is
susceptible to different interpretations,
in that it could conceivably mean one or
many source categories, we believe that
our interpretation is a permissible
construction given the juxtaposition of
the phrases ‘‘any pollutant’’ and ‘‘a
source category’’ in section 111(d), as
amended by the House.
Moreover, consistent with our
interpretation of the House amendment,
we believe that the House sought to
change the focus of section 111(d) by
seeking to preclude regulation of those
pollutants that are emitted from a
particular source category that is
actually regulated under section 112.
The legislative history described above
is instructive in this regard. At the same
time the House substantively amended
section 111(d), it passed a bill
containing a provision (section 112(l))
that is identical to section 112(n)(1)(A)
of the current act. Section 112(l) of the
House bill calls for EPA to examine how
the ‘‘imposition of the requirements of
th[e] Act’’ would affect utility HAP
emissions. This provision suggests that
the House did not want to subject
Utility Units to duplicative or
overlapping regulation. In this regard,
the House’s amendment to section
111(d) could reasonably reflect its effort
to expand EPA’s authority under section
111(d) for regulating pollutants emitted
from particular source categories that
are not being regulated under section
112. Such a reading of the House
language would authorize EPA to
regulate under section 111(d) existing
area sources which EPA determined did
not meet the statutory criterion set forth
in section 112(c)(3), as well as existing
Utility Units (in the event EPA did not
decide to regulate such units under
section 112).
The Senate amendment provides that
a section 111(d) standard of
performance cannot be established for
any HAP that is listed in section
112(b)(1), regardless of whether the
source categories that emit such HAP
are actually regulated under section 112.
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The Senate amendment reflects the
Senate’s intent to retain the pre-1990
approach of precluding regulation under
CAA section 111(d) of any HAP listed
under section 112(b). The Senate’s
intent in this regard is confirmed by the
fact that its amendment is labeled a
‘‘conforming amendment,’’ which is
generally a non-substantive amendment.
By contrast, the House amendment is
not a conforming amendment.62
Moreover, the Senate’s conforming
amendment is consistent with the
Senate’s treatment of Utility Units in the
final Senate Bill. Unlike the House bill,
the Senate bill did not call for an
examination of the other requirements
of the CAA. Nor did it provide EPA
discretion to determine whether Utility
Units should be regulated under section
112. Instead, the Senate bill included a
provision that would have required EPA
to establish section 112(d) emission
standards for Utility Units by a date
certain. This provision, which was
never enacted into law, is consistent
with the Senate’s conforming
amendment which provides that HAP
listed under section 112(b) cannot be
regulated under section 111(d).
Based on the legislative history
described above, we believe that the
House amendment, as we have
interpreted it, is wholly consistent with
section 112(l) of the House bill, which
the conference committee adopted as
the provision governing Utility Units
(section 112(n)(1)(A). It is hard to
conceive that Congress would have
adopted section 112(n)(1)(A), yet
retained the Senate amendment to
section 111(d). While it appears that the
Senate amendment to section 111(d) is
a drafting error and therefore should not
be considered, we must attempt to give
effect to both the House and Senate
amendments, as they are both part of the
current law.
The House and Senate amendments
conflict in that they provide different
standards as to the scope of EPA’s
authority to regulate under section
111(d). As we explained at proposal, in
an effort to give some effect to both
amendments, we reasonably interpret
the amendments as follows: Where a
source category is being regulated under
section 112, a section 111(d) standard of
performance cannot be established to
address any HAP listed under section
112(b) that may be emitted from that
particular source category. Thus, if EPA
is regulating source category X under
section 112, section 111(d) could not be
62 There is a section of the final House bill that
includes conforming amendments. The House
amendment to section 111(d) does not appear in
that sectiono of the bill, however. See Legislative
History, Vol. II, at 179, 1986.
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used to regulate any HAP emissions
from that particular source category.
This is a reasonable interpretation of the
amendments to section 111(d) because it
gives some effect to both amendments.
First, it gives effect to the Senate’s
desire to focus on HAP listed under
section 112(b), rather than applying the
section 111(d) exclusion to non-HAP
emitted from a source category regulated
under section 112, which a literal
reading of the House amendment would
do. Second, it gives effect to the House’s
desire to increase the scope of EPA’s
authority under section 111(d) and to
avoid duplicative regulation of HAP for
a particular source category. See 136
Cong. Rec. H12911, 12934 (daily ed.
Oct. 26, 1990) (the conferees adopted
section 112(n)(1)(A) ‘‘because of the
logic of basing any decision to regulate
on the results of scientific study and
because of the emission reductions that
will be achieved and the extremely high
costs that electric utilities will face
under other provisions of the new Clean
Air Act amendments.’’).
We recognize that our proposed
reconciliation of the two conflicting
amendments does not give full effect to
the House’s language, because a literal
reading of the House language would
mean that EPA could not regulate HAP
or non-HAP emitted from a source
category regulated under section 112.
Such a reading would be inconsistent
with the general thrust of the 1990
amendments, which, on balance,
reflects Congress’ desire to require EPA
to regulate more substances, not to
eliminate EPA’s ability to regulate large
categories of pollutants like non-HAP.
Furthermore, EPA has historically
regulated non-HAP under section
111(d), even where those non-HAP were
emitted from a source category actually
regulated under section 112. See, e.g.,
40 CFR 62.1100 (California State Plan
for Control of Fluoride Emissions from
Existing Facilities at Phosphate
Fertilizer Plants). We do not believe that
Congress sought to eliminate regulation
for a large category of sources in the
1990 Amendments and our proposed
interpretation of the two amendments to
section 111(d) avoids this result.63
Finally, in assessing whether to revise
the December 2000 ‘‘necessary’’ finding,
it is reasonable to look to whether CAA
section 111 constituted a viable
alternative authority for regulating
utility HAP emissions prior to the
December 2000 finding. The answer is
yes and therefore under our proposed
interpretation of the conflicting
amendments, we could have regulated
HAP from Utility Units under section
111(d). We listed coal- and oil-fired
Utility Units under section 112(c) in
December 2000 based solely on our
appropriate and necessary finding. As
explained above, that finding lacks
foundation and recent information
confirms that it is neither appropriate
nor necessary to regulate Utility Units
under CAA section 112. We should have
recognized prior to the December 2000
finding that section 111 constituted a
viable authority for regulating utility
HAP emissions and therefore should
have never listed Utility Units on the
Section 112(c) list. In addition, as
explained below, the December 2000
finding and associated listing is not a
final agency action and EPA can
therefore make revisions to that finding
at any point prior to taking final action.
Such revisions are particularly
appropriate here, because the prior
finding is incorrect and new
information confirms this fact.
Some commenters argue that their
reading of the House amendment and
reconciliation of the amendments is
reasonable, but the question is not
whether commenters have identified a
reasonable construction of section
112(d). Rather, the issue is whether our
construction is a permissible one, and
for the reasons set forth above, we
believe that it is. See Smiley v. Citibank,
N.A. 517 U.S. 735, 744–45 (1996) (a
‘‘permissible’’ interpretation is one that
is ‘‘reasonable’’). Other commenters
effectively ask us to ignore the House
amendment because the Senate
amendment reflects the law as of 1977.
We cannot ignore the House
amendment, as it is part of current law,
and Congress substantially amended the
law in 1990, by including, among other
things, section 112(n)(1)(A).64
63 The first instance in which the Agency
proposed an interpretation of the conflicting House
and Senate amendments to CAA section 111(d) was
in the January 2004 proposed rule. We recognize
that we may have made statements concerning
section 111(d), since the 1990 Amendments, but
those statements did not recognize or account for
the two different amendments to section 111(d), as
enacted in 1990. We are also amending 40 CFR
60.21, as part of the final CAMR. That regulation,
which was promulgated in 1975, interprets the 1970
CAA and defines a ‘‘designated pollutant’’ for
purposes of section 111(d), as excluding any
pollutant that is listed on the section 112(b)(1)(A)
list. There is no section 112(b)(1)(A) in the current
act, as amended in 1990. We are therefore revising
40 CFR 60.21 because it does not reflect the current
language of section 111(d), as amended in 1990.
64 Finally, some commenters argue that EPA’s
interpretation of the conflicting amendments was
unreasonable, because it would give EPA discretion
to regulate area sources, under section 111, as
opposed to section 112. These commenters fail to
recognize the listing criteria for area sources under
section 112(c)(3). That section, for example,
provides that EPA shall list a category or
subcategory of area sources under section 112 if it
finds that the category or subcategory presents a
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VIII. Removal of Coal- and Oil-Fired
Utility Units From the Section 112(C)
List
Section 112(n)(1)(A) sets forth the
criteria for regulating Utility Units
under section 112. The criteria are:
Whether regulation of Utility Units
under section 112 of the CAA is
‘‘appropriate’’ and ‘‘necessary.’’ In
December 2000, EPA added coal- and
oil-fired Utility Units to the section
112(c) list in light of its positive
appropriate and necessary finding for
such units. See 65 FR 79831.
In the January 2004 proposed rule,
EPA proposed removing coal- and oilfired Utility Units from the section
112(c) list based on our proposed
reversal of the December 2000 finding.
Today, we conclude that the December
2000 finding lacked foundation and that
regulation of coal- and oil-fired Utility
Units under section 112 is not
appropriate and necessary. Based on
those decisions and our revision of the
December 2000 finding, we remove
coal- and oil-fired Utility Units from the
section 112(c) list. We disagree with
those commenters that argue that EPA
cannot remove coal and oil-fired Utility
Units from the section 112(c) list
without satisfying the delisting criteria
in section 112(c)(9).
EPA reasonably interprets section
112(n)(1)(A) as providing it authority to
remove coal- and oil-fired units from the
section 112(c) list at any time that it
makes a negative appropriate and
necessary finding under the section.
Congress set up an entirely different
structure and predicate for assessing
whether Utility Units should be listed
for regulation under section 112.
Compare 112(c)(1) and (c)(3), with
112(n)(1)(A). Section 112(n)(1)(A)
threat of adverse effects to human health or the
environment in a manner ‘‘that warrants regulation
under section 112.’’ Thus, EPA must determine
whether the category or subcategory presents a
threat that warrants regulation under section 112.
If EPA determined that the listing criteria for a
category of area sources were not met, nothing
would preclude EPA from regulating HAP from that
category under section 111(d), which contains
different requirements for regulation. See General
Overview of section 111 above.
Another commenter argued that EPA’s
interpretation of the two amendments is contrary to
a canon of statutory construction that provides that
where a conflict exists between two provisions of
an act, the last provision in point of arrangement
controls. This commenter argues that because the
Senate conforming amendment is found in section
302 of Public Law 101–549, and the House
amendment in section 108(g), the Senate
amendment should control. As explained above,
this canon of statutory construction is not directly
relevant to situations where the conflict at issue is
between two different amendments to the same
statutory provision. Furthermore, application of this
canon of construction would be contrary to the
legislative history described above.
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therefore occupies the field in section
112 with regard to Utility Units. Section
112(n)(1)(A) provides EPA significant
discretion in making the appropriate
and necessary finding and nothing in
section 112(n)(1)(A) suggests that EPA
cannot revise its finding, where, as here,
it has both identified errors in its prior
finding and determined that the finding
lacked foundation, and where EPA has
received new information that confirms
that it is not appropriate or necessary to
regulate coal- and oil-fired Utility Units
under section 112.65
The section 112(c)(9) criteria also do
not apply in two situations that are
directly relevant here. First, the
December 2000 appropriate and
necessary finding and associated listing
are not final agency actions. UARG v.
EPA, 2001 WL 936363, No. 01–1074 (DC
Cir. July 26, 2001). EPA therefore has
inherent authority under the CAA to
revise those actions at any time based
on either identified errors in the
December 2000 finding or on new
information that bears upon that
finding. Second, as explained in the
proposed rule, the section 112(c)(9)
criteria do not apply where, as here, the
source category at issue did not meet the
statutory criteria for listing at the time
of listing. See 68 FR 28197, 28200 June
4, 1996; see also 69 FR 4689 (citing
additional examples where EPA has
removed a source category from the
section 112(c) list without following the
criteria in section 112(c)(9) due to an
error at the time of listing). For all of the
reasons noted above, EPA did not meet
the statutory listing criteria at the time
of listing for coal- and oil-fired Utility
Units. Accordingly, coal- and oil-fired
Utility Units should never have been
listed under section 112(c) and therefore
the criteria of section 112(c)(9) do not
apply to today’s action.
IX. Statutory and Executive Order
Reviews
A. Executive Order 12866: Regulatory
Planning and Review
Under Executive Order 12866 (58 FR
51735, October 4, 1993), the Agency
must determine whether a regulatory
action is ‘‘significant’’ and therefore
subject to Office of Management and
Budget (OMB) review and the
65 Although not critical to our analysis, we do
note that it is questionable whether we even had a
legal obligation in December 2000 to list Utility
Units under section 112(c) after making the positive
appropriate and necessary finding. Section
112(n)(1)(A) makes no reference to CAA section
112(c) and the framework of section 112(c)(1) and
(c)(3) does not expressly provide for the listing of
Utility Units. Rather, those provisions speak to
major and area sources, which Congress treated
differently from Utility Units.
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requirements of the Executive Order.
The Order defines ‘‘significant
regulatory action’’ as one that is likely
to result in a rule that may:
1. Have an annual effect on the
economy of $100 million or more or
adversely affect in a material way the
economy, a sector of the economy,
productivity, competition, jobs, the
environment, public health or safety, or
State, local, or Tribal governments or
communities;
2. Create a serious inconsistency or
otherwise interfere with an action taken
or planned by another agency;
3. Materially alter the budgetary
impact of entitlements, grants, user fees,
or loan programs or the rights and
obligations of recipients thereof; or
4. Raise novel legal or policy issues
arising out of legal mandates, the
President’s priorities, or the principles
set forth in the Executive Order.
Pursuant to the terms of Executive
Order 12866, OMB has notified us that
it considers this a ‘‘significant
regulatory action’’ within the meaning
of the Executive Order. We have
submitted this action to OMB for
review. However, EPA has determined
that this rulemaking will not have a
significant economic impact. Changes
made in response to OMB suggestions or
recommendations will be documented
in the public record. All written
comments from OMB to EPA and any
written EPA response to any of those
comments are included in the docket
listed at the beginning of this notice
under ADDRESSES.
B. Paperwork Reduction Act
This action does not contain any
information collection requirements and
therefore is not subject to the Paperwork
Reduction Act (44 U.S.C. 3501 et seq.).
C. Regulatory Flexibility Act
The Regulatory Flexibility Act (5
U.S.C. 601 et seq.) (RFA), as amended
by the Small Business Regulatory
Enforcement Fairness Act (Pub. L. 104–
121) (SBREFA), provides that whenever
an agency is required to publish a
general notice of rulemaking, it must
prepare a regulatory flexibility analysis,
unless it certifies that the rule, if
promulgated, will not have ‘‘a
significant economic impact on a
substantial number of small entities.’’ 5
U.S.C. 605(b). Small entities include
small businesses, small organizations,
and small governmental jurisdictions.
As was discussed in the January 30,
2004 NPR, EPA determined that it was
not necessary to prepare a regulatory
flexibility analysis in conjunction with
this rulemaking. We certify that this
action will not have a significant impact
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16033
on a substantial number of small entities
because it imposes no regulatory
requirements.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates
Reform Act of 1995 (Pub. L. 104–4)
(UMRA), establishes requirements for
Federal agencies to assess the effects of
their regulatory actions on State, local,
and Tribal governments and the private
sector. Under UMRA section 202, 2
U.S.C. 1532, EPA generally must
prepare a written statement, including a
cost-benefit analysis, for any proposed
or final rule that ‘‘includes any Federal
mandate that may result in the
expenditure by State, local, and Tribal
governments, in the aggregate, or by the
private sector, of $100,000,000 or more
* * * in any one year.’’ A ‘‘Federal
mandate’’ is defined under section
421(6), 2 U.S.C. 658(6), to include a
‘‘Federal intergovernmental mandate’’
and a ‘‘Federal private sector mandate.’’
A ‘‘Federal intergovernmental
mandate,’’ in turn, is defined to include
a regulation that ‘‘would impose an
enforceable duty upon State, local, or
Tribal governments,’’ section
421(5)(A)(i), 2 U.S.C. 658(5)(A)(i),
except for, among other things, a duty
that is ‘‘a condition of Federal
assistance,’’ section 421(5)(A)(i)(I). A
‘‘Federal private sector mandate’’
includes a regulation that ‘‘would
impose an enforceable duty upon the
private sector,’’ with certain exceptions,
section 421(7)(A), 2 U.S.C. 658(7)(A).
We have determined that the final
rule does not contain a Federal mandate
that may result in expenditures of $100
million or more for State, local, or tribal
governments, in the aggregate, or the
private sector in any 1 year. Thus,
today’s final rule is not subject to the
requirements of sections 202 and 205 of
the UMRA. In addition, we have
determined that the final rule contains
no regulatory requirements that might
significantly or uniquely affect small
governments because it contains no
regulatory requirements that apply to
such governments or impose obligations
upon them. Therefore, the final rule is
not subject to the requirements of
section 203 of UMRA.
E. Executive Order 13132: Federalism
Executive Order 13132, entitled
‘‘Federalism’’ (64 FR 43255, August 10,
1999), requires EPA to develop an
accountable process to ensure
‘‘meaningful and timely input by State
and local officials in the development of
regulatory policies that have federalism
implications.’’ ‘‘Policies that have
federalism implications’’ is defined in
the EO to include regulations that have
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‘‘substantial direct effects on the States,
on the relationship between the national
government and the States, or on the
distribution of power and
responsibilities among the various
levels of government.’’
This rule does not have federalism
implications. It will not have substantial
direct effects on the States, on the
relationship between the national
government and the States, or on the
distribution of power and
responsibilities among the various
levels of government, as specified in EO
13132. The CAA establishes the
relationship between the Federal
government and the States, and this rule
does not impact that relationship. Thus,
EO 13132 does not apply to this rule.
However, in the spirit of EO 13132, and
consistent with EPA policy to promote
communications between EPA and State
and local governments, EPA specifically
solicited comment on this rule from
State and local officials.
F. Executive Order 13175: Consultation
and Coordination With Indian Tribal
Governments
EO 13175, entitled ‘‘Consultation and
Coordination with Indian Tribal
Governments’’ (65 FR 67249, November
9, 2000), requires EPA to develop an
accountable process to ensure
‘‘meaningful and timely input by Tribal
officials in the development of
regulatory policies that have Tribal
implications.’’
This rule does not have Tribal
implications as defined by EO 13175. It
does not have a substantial direct effect
on one or more Indian Tribes, in that it
is a determination not to regulate
utilities under section 112, and
therefore imposes no burdens on tribes.
Furthermore, this rule does not affect
the relationship or distribution of power
and responsibilities between the Federal
government and Indian Tribes. The
CAA and the Tribal Authority Rule
(TAR) establish the relationship of the
Federal government and Tribes in
implementing the Clean Air Act.
Because this rule does not have Tribal
implications, EO 13175 does not apply.
Although EO 13175 does not apply to
this rule, EPA took several steps to
consult with Tribal officials in
developing this rule. EPA gave a
presentation to a national meeting of the
Tribal Environmental Council (NTEC) in
April 2001, and encouraged Tribal input
at an early stage. EPA then worked with
NTEC to find a Tribal representative to
participate in the workgroup developing
the rule, and included a representative
from the Navajo Nation as a member the
official workgroup, with a
representative from the Campo Band
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later added as an alternate. In March
2004, EPA provided a briefing for Tribal
representatives and the newly formed
National Tribal Air Association and
NTEC. EPA received comments on this
rule from a number of tribes, and has
taken those comments and other input
from Tribal representatives into
consideration in development of this
rule.
G. Executive Order 13045: Protection of
Children From Environmental Health
and Safety Risks
Executive Order 13045, ‘‘Protection of
Children from Environmental Health
and Safety Risks’’ (62 FR 19885, April
23, 1997) applies to any rule that (1) is
determined to be ‘‘economically
significant’’ as defined under EO 12866,
and (2) concerns an environmental
health or safety risk that EPA has reason
to believe may have a disproportionate
effect on children. If the regulatory
action meets both criteria, section 5–501
of the EO directs the Agency to evaluate
the environmental health or safety
effects of the planned rule on children,
and explain why the planned regulation
is preferable to other potentially
effective and reasonably feasible
alternatives considered by the Agency.
The final rule is not subject to
Executive Order 13045 because it is not
an economically significant regulatory
action as defined by Executive Order
12866. In addition, EPA interprets
Executive Order 13045 as applying only
to those regulatory actions that are
based on health and safety risks, such
that the analysis required under section
5–501 of the Executive Order has the
potential to influence the regulations.
The final rule is not subject to Executive
Order 13045 because it does not include
regulatory requirements based on health
or safety risks.
Nonetheless, in making its
determination as to whether it is
‘‘appropriate and necessary’’ to regulate
Utility Units under section 112, EPA
considered the effects of utility HAP
emissions on both the general
population and sensitive
subpopulations, including children.
H. Executive Order 13211: Actions
Concerning Regulations That
Significantly Affect Energy Supply,
Distribution, or Use
Executive Order 13211 (66 FR 28355,
May 22, 2001) provides that agencies
shall prepare and submit to the
Administrator of the Office of
Regulatory Affairs, OMB, a Statement of
Energy Effects for certain actions
identified as ‘‘significant energy
actions.’’ Section 4(b) of EO 13211
defines ‘‘significant energy actions’’ as
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‘‘any action by an agency (normally
published in the Federal Register) that
promulgates or is expected to lead to the
promulgation of a final rule or
regulation, including notices of inquiry,
advance notices of final rulemaking, and
notices of final rulemaking: (1) (i) That
is a significant regulatory action under
EO 12866 or any successor order, and
(ii) is likely to have a significant adverse
effect on the supply, distribution, or use
of energy; or (2) that is designated by the
Administrator of the Office of
Information and Regulatory Affairs as a
‘‘significant energy action.’’ Although
this final rule is a significant regulatory
action under EO 12866, it will not have
a significant adverse effect on the
supply, distribution, or use of energy.
I. National Technology Transfer and
Advancement Act
Section 12(d) of the National
Technology Transfer and Advancement
Act (NTTAA) of 1995 (Pub. L. 104–113;
Section 12(d), 15 U.S.C. 272 note)
directs EPA to use voluntary consensus
standards (VCS) in their regulatory and
procurement activities unless to do so
would be inconsistent with applicable
law or otherwise impractical. Voluntary
consensus standards are technical
standards (e.g., materials specifications,
test methods, sampling procedures,
business practices) developed or
adopted by one or more voluntary
consensus bodies. NTTAA directs EPA
to provide Congress, through annual
reports to OMB, with explanations
when an agency does not use available
and applicable VCS.
This action does not involve technical
standards and therefore the NTTAA
does not apply.
J. Executive Order 12898: Federal
Actions To Address Environmental
Justice in Minority Populations and
Low-Income Populations
Executive Order 12898, ‘‘Federal
Actions to Address Environmental
Justice in Minority Populations and
Low-Income Populations,’’ provides for
Federal agencies to consider the impact
of programs, policies, and activities on
minority populations and low-income
populations, including tribes.
As described above, in making its
determination as to whether it is
‘‘appropriate and necessary’’ to regulate
Utility Units under section 112, EPA
considered the effects of utility HAP
emissions on both the general
population and sensitive
subpopulations, including subsistence
fish-eaters. EPA’s analysis considered
such subpopulations as the Chippewa in
Minnesota, Wisconsin, and Michigan;
and the Hmong in Minnesota and
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Wisconsin. As explained above, the
Agency has concluded that it is not
‘‘appropriate and necessary’’ to regulate
Utility Units under section 112, in light
of all available information, including
information on subsistence fish-eaters.
The Agency believes that
implementation of the CAIR and,
independently, the CAMR will remove
the hazards to public health resulting
from utility HAP emissions.
This action, however, does not
actually regulate HAP emissions from
utilities. The CAMR does regulate Hg
emissions from utilities, and it is in the
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CAMR rulemaking that EPA has
addressed the impacts of that regulation
on the populations addressed by
Executive Order 12898.
K. Congressional Review Act
The Congressional Review Act, 5
U.S.C. 801 et seq., as added by SBREFA
of 1996, generally provides that before
a rule may take effect, the agency
promulgating the rule must submit a
rule report, which includes a copy of
the rule, to each House of the Congress
and to the Comptroller General of the
U.S. The EPA will submit a report
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16035
containing this rule and other required
information to the U.S. Senate, the U.S.
House of Representatives, and the
Comptroller General of the U.S. prior to
publication of the rule in the Federal
Register. The final rule is not a ‘‘major
rule’’ as defined by 5 U.S.C. 804(2). The
final rule will be effective on March 29,
2005.
Dated: March 15, 2005.
Stephen Johnson,
Acting Administrator.
[FR Doc. 05–6037 Filed 3–28–05; 8:45 am]
BILLING CODE 6560–50–P
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]]>Agencies
[Federal Register Volume 70, Number 59 (Tuesday, March 29, 2005)]
[Rules and Regulations]
[Pages 15994-16035]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-6037]
[[Page 15993]]
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Part II
Environmental Protection Agency
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40 CFR Part 63
Revision of December 2000 Regulatory Finding on the Emissions of
Hazardous Air Pollutants From Electric Utility Steam Generating Units
and the Removal of Coal- and Oil-Fired Electric Utility Steam
Generating Units From the Section 112(c) List; Final Rule
Federal Register / Vol. 70, No. 59 / Tuesday, March 29, 2005 / Rules
and Regulations
[[Page 15994]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 63
[OAR-2002-0056; FRL-7887-7]
RIN 2060-AM96
Revision of December 2000 Regulatory Finding on the Emissions of
Hazardous Air Pollutants From Electric Utility Steam Generating Units
and the Removal of Coal- and Oil-Fired Electric Utility Steam
Generating Units From the Section 112(c) List
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: The EPA is revising the regulatory finding that it issued in
December 2000 pursuant to section 112(n)(1)(A) of the Clean Air Act
(CAA), and based on that revision, removing coal- and oil-fired
electric utility steam generating units (``coal- and oil-fired Utility
Units'') from the CAA section 112(c) source category list. Section
112(n)(1)(A) of the CAA is the threshold statutory provision underlying
today's action. That provision requires EPA to conduct a study to
examine the hazards to public health that are reasonably anticipated to
occur as the result of hazardous air pollutant (HAP) emissions from
Utility Units after imposition of the requirements of the CAA. The
provision also provides that EPA shall regulate Utility Units under
section 112, but only if the Administrator determines that such
regulation is both ``appropriate'' and ``necessary'' considering, among
other things, the results of the study. EPA completed the study in 1998
(the Utility Study), and in December 2000 found that it was
``appropriate and necessary'' to regulate coal- and oil-fired Utility
Units under CAA section 112. That December 2000 finding focused
primarily on mercury (Hg) emissions from coal-fired Utility Units. In
light of the finding, EPA in December 2000 announced its decision to
list coal- and oil-fired Utility Units on the section 112(c) list of
regulated source categories. In January 2004, EPA proposed revising the
December 2000 appropriate and necessary finding and, based on that
revision, removing coal- and oil-fired Utility Units from the section
112(c) list.
By this action, we are revising the December 2000 appropriate and
necessary finding and concluding that it is neither appropriate nor
necessary to regulate coal- and oil-fired Utility Units under section
112. We are taking this action because we now believe that the December
2000 finding lacked foundation and because recent information
demonstrates that it is not appropriate or necessary to regulate coal-
and oil-fired Utility Units under section 112. Based solely on the
revised finding, we are removing coal- and oil-fired Utility Units from
the section 112(c) list. The reasons supporting this action are
described in detail below. Other actions related to this final rule
include the recent promulgation of the final Clean Air Interstate Rule
(CAIR) and the final Clean Air Mercury Rule (CAMR).
DATES: Effective Date: The effective date of the final rule is March
29, 2005.
ADDRESSES: EPA has established a docket for this action under Docket ID
No. OAR-2002-0056. All documents in the docket are listed in the
EDOCKET index at https://www.epa.gov/edocket. Although listed in the
index, some information is not publicly available, i.e., Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Certain other material, such as copyrighted
material, is not placed on the Internet and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically in EDOCKET or in hard copy at the EPA
Docket Center (EPA/DC), EPA West Building, Room B102, 1301 Constitution
Ave., NW., Washington, DC. The Public Reading Room is open from 8:30
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The
telephone number for the Public Reading Room is (202) 566-1744, and the
telephone number for the EPA Docket Center is (202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Ms. Wendy Blake, OGC Attorney, Office
of General Counsel, Environmental Protection Agency, (AR-2344),
Washington, DC 20460 telephone number: (202) 564-1821; fax number:
(202) 564-5603; e-mail address: blake.wendy@epa.gov.
Judicial Review. Pursuant to CAA section 307(b), judicial review of
this final rule is available only by filing a petition for review in
the United States Court of Appeals for the District of Columbia Circuit
by May 31, 2005. EPA designates this action a CAA section 307(d)
rulemaking. (See CAA section 307(d)(1)(V); 69 FR 4653 (January 30,
2004).) Under CAA section 307(d)(7)(B), only an objection to the rule
that was raised with reasonable specificity during the time period for
public comment can be raised during judicial review. Section
307(d)(7)(B) further provides that if the person raising the objection
can demonstrate to the Administrator that it was impracticable to raise
the objection during the public comment period or if the grounds for
the objection arose after the public comment period but within the time
period specified for judicial review and if the objection is of central
relevance, EPA will convene a proceeding for reconsideration of the
rule and provide the same procedural rights as would have been afforded
had the information been available at the time the rule was proposed.
I. Statutory Background
In the 1990 Amendments to the CAA, Congress substantially modified
CAA section 112, the provision of the CAA addressing HAP. Among other
things, section 112 contains a list of ``hazardous air pollutants,''
which are ``pollutants which present, or may present, * * * a threat of
adverse human health effects * * * or adverse environmental effects
whether through ambient concentrations, bioaccumulation, deposition, or
otherwise.'' (See CAA section 112(b)(2).) In the 1990 amendments to the
CAA, Congress listed 190 HAP, and authorized EPA to add or remove
pollutants from the list.\1\ (See CAA Section 112(b)(1)-(b)(3).)
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\1\ The current section 112(b) list includes 188 HAP.
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The types of sources addressed under section 112 include: major
sources, area sources, and electric utility steam generating units
(Utility Units). (See CAA 112(a)(1), (a)(2), (a)(8).) A ``major
source'' is any stationary source \2\ or group of stationary sources at
a single location and under common control that emits or has the
potential to emit ten tons or more per year of any HAP or 25 tons or
more per year of any combination of HAP. (See CAA 112(a)(1).) A
stationary source of HAP that is not a ``major source'' is an ``area
source.'' (See CAA 112(a)(2).) Finally, an electric utility steam
generating unit is any ``fossil fuel fired combustion unit of more than
25 megawatts that serves a generator that produces electricity for
sale.'' (See CAA 112(a)(8).)
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\2\ A ``stationary source'' of hazardous air pollutants is any
building, structure, facility or installation that emits or may emit
any air pollutant. (See CAA Section 111(a)(3) and 112(a)(3).)
---------------------------------------------------------------------------
There are two important steps under section 112: (1) Determining
whether a source category meets the statutory criteria for regulation
under section 112; and (2) promulgating emission standards for those
source categories regulated under section 112. In terms of the first
step, Congress required EPA to publish a list of categories and
[[Page 15995]]
subcategories of major sources and area sources by November 15,
1991.\3\ (See CAA 112(c)(1) & (c)(3).) Congress further directed EPA to
revise this initial list periodically, based on, for example, new
information. (See 112(c)(1).) EPA is required to list a category of
major sources under section 112(c)(1) if at least one stationary source
in the category meets the definition of a major source--i.e., if a
certain amount of a HAP (or combination of HAP) is emitted from the
source. (See 112(a)(1).) By contrast, EPA is required to list
categories or subcategories of area sources only if they meet one of
the following statutory criteria: (1) EPA determines that the category
of area sources presents a threat of adverse effects to human health or
the environment that warrants regulation under CAA section 112; or (2)
the category of area sources falls within the purview of CAA section
112(k)(3)(B) (the Urban Area Source Strategy). (See CAA 112(c)(3).)
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\3\ EPA published the initial list on July 16, 1992. See 57 FR
31,576, July 16, 1992. EPA did not include Utility Units on the
initial section 112(c) list because Congress required EPA to conduct
and consider the results of the study required by section
112(n)(1)(A) before regulating these units and, therefore, listing
in 1992 was not authorized by statute.
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For those source categories regulated under section 112, the next
step concerns the establishment of emission standards. Under section
112(d), EPA must establish emission standards that ``require the
maximum degree of reduction in emissions of the hazardous air
pollutants subject to this section'' that the Administrator determines
is achievable based on technology, taking into account certain factors
such as cost, energy requirements, and other impacts. The emission
standard for new sources cannot be, however, less stringent than the
level of control achieved by the best controlled similar source, and
the emission standard for existing sources cannot be less stringent
than the average emission limitation achieved by the best performing 12
percent of existing sources in the category, regardless of cost, energy
requirements and other impacts. CAA 112(d)(2) and (3). Finally, within
eight years after promulgation of section 112(d) emission standards for
a listed source category, EPA must promulgate additional standards if
such standards are necessary to provide an ample margin of safety to
protect public health or to prevent an adverse environmental effect.
(See CAA section 112(f).) These additional standards under CAA section
112(f) are commonly referred to as ``residual risk'' standards.
The criteria for listing major and area sources established in
section 112(c)(1) and (c)(3) do not apply to Utility Units because
Congress treated Utility Units differently from other major and area
sources. Indeed, Congress enacted a special provision for Utility Units
in section 112(n)(1)(A), which governs whether Utility Units should
even be regulated under section 112.\4\ Section 112(n)(1)(A) directs
EPA to conduct a study to evaluate what ``hazards to public health
[are] reasonably anticipated to occur'' as the result of HAP emissions
from Utility Units ``after imposition of the requirements of th[e]
Act,'' (emphasis added) and to report the results of such study to
Congress by November 15, 1993. Congress also directed EPA to describe
in the report to Congress ``alternative control strategies for [those]
emissions that may warrant regulation under this section.'' (See CAA
section 112(n)(1)(A).) Section 112(n)(1)(A) further provides that EPA
shall regulate Utility Units under section 112 if the Administrator
determines, considering the results of the study, that such regulation
is ``appropriate and necessary.'' Thus, unlike other major and area
sources, Congress first required EPA to examine how ``imposition of the
requirements of th[e] Act'' would affect the overall level of utility
HAP emissions, and then determine whether regulation of Utility Units
under section 112 is both appropriate and necessary. Section
112(n)(1)(A) therefore sets an important and unique condition precedent
for regulating Utility Units under section 112 and provides EPA
discretion in determining whether that condition precedent has been
met.
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\4\ No one would dispute that certain Utility Units would meet
the definition of a ``major source'' based on the quantity of HAP
emitted from such units, or that other Utility Units may meet the
``area source'' criteria for listing under section 112(c)(3), but
Congress recognized this fact in 1990 and specifically enacted
section 112(n)(1)(A), which establishes an entirely different test
for determining whether Utility Units should be regulated under
section 112.
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II. Regulatory Background
A. EPA's December 20, 2000 Regulatory Finding
On December 20, 2000, EPA issued a finding pursuant to CAA section
112(n)(1)(A) that it was appropriate and necessary to regulate coal-
and oil-fired Utility Units under section 112. In making that finding,
EPA considered the Utility Study, which was completed and submitted to
Congress in February 1998.
In the Utility Study, we divided Utility Units into three
subcategories based on fuel type: coal-, oil-, and gas-fired units. We
then analyzed HAP emissions from each subcategory. We followed this
approach because each subcategory burns a different fuel, which, in
turn, leads to different emissions profiles, which can require
different emission controls. This approach is also consistent with
EPA's historical practice of subcategorizing Utility Units based on
fuel type. (See, e.g., 40 CFR 60.44(a).)
Because EPA subcategorized Utility Units for purposes of the
Utility Study, EPA, in December 2000, made separate ``appropriate and
necessary'' findings under section 112(n)(1)(A) for gas-fired, coal-
fired, and oil-fired Utility Units. In making these findings, EPA
considered the Utility Study and certain additional information
obtained after completion of the Utility Study, including the National
Academy of Sciences' report concerning the health effects of
methylmercury and actual emissions data obtained in response to an
information collection request EPA issued to all coal-fired Utility
Units in 1999. See 65 FR 79826. EPA reasonably relied on this
additional information because the information provided a more
comprehensive and contemporaneous record concerning Hg emissions from
coal-fired units. Nothing in section 112(n)(1)(A) suggests that
Congress sought to preclude EPA from considering more current
information in making the appropriate and necessary finding.
In the December 2000 finding, EPA determined that it was
appropriate and necessary to regulate coal- and oil-fired units, but
not gas-fired units.\5\ With respect to the latter, EPA found that
regulation of HAP emissions from natural gas-fired Utility Units ``is
not appropriate or necessary because the impacts due to HAP emissions
from such units are negligible based on the results of the study
documented in the utility RTC.'' (Emphasis added) See 65 FR 79831.
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\5\ Although the December 2000 finding addressed three
subcategories of Utility Units--coal-, oil-, and gas-fired units,
the majority of the finding concerned Hg emissions from coal-fired
power plants. 65 FR 79826-29 (explaining that Hg from coal-fired
units is the HAP of greatest concern); Utility Study, ES-27
(``mercury from coal-fired utilities is the HAP of greatest
potential concern.'').
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EPA provided three primary reasons in support of its finding that
it was ``appropriate'' to regulate coal- and oil-fired Utility Units
under section 112. First, EPA found that it was appropriate to regulate
HAP emissions from coal- and oil-fired Utility Units because Utility
Units ``are the largest domestic source of Hg emissions.'' See 65 FR
79830. EPA next found that it was
[[Page 15996]]
appropriate to regulate coal- and oil-fired Utility Units because
``mercury in the environment presents significant hazards to public
health and the environment.'' \6\ See 65 FR 79830. Finally, EPA
explained that it was appropriate to regulate HAP emissions from coal-
and oil-fired units because it had identified certain control options
that, it anticipated, would effectively reduce HAP from such units. In
discussing the appropriate finding, EPA also noted that uncertainties
remained concerning the extent of the public health impact from HAP
emissions from oil-fired units. Thus, EPA's determination that it was
``appropriate'' to regulate coal- and oil-fired units under section 112
hinged on the health effects associated with Hg emissions from coal-
fired Utility Units, the uncertainties associated with the health
effects of HAP from oil-fired Utility Units, and EPA's belief that
control options would be available to reduce certain utility HAP
emissions.\7\
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\6\ Section IV below addresses our conclusion that it is not
appropriate and necessary to regulate coal- and oil-fired Utility
Units under section 112 and explains why we now believe that our
December 2000 finding lacked foundation. As explained below, one of
the reasons the December 2000 ``appropriate'' finding for oil-fired
Utility Units lacks foundation is because the record that was before
the Agency in December 2000 establishes that Hg is a HAP of concern
only as emitted from coal-fired units, not oil-fired units. Utility
Study ES-5,13,27. EPA therefore should not have relied upon Hg
emissions as a basis for finding it was appropriate to regulate oil-
fired units under section 112. (See, e.g., Utility Study ES-5, ES-
27.)
\7\ The ``appropriate'' finding for oil-fired units stemmed
primarily from EPA's concerns over the potential health effects of
nickel from such units. As explained in the January 2004 proposed
rule, the record before the Agency in December 2000 supported a
distinction between nickel and the other HAP emitted from oil-fired
units. See 69 FR 4688. We proposed that this distinction was
reasonable based on the relative amount of nickel emitted from oil-
fired units and the health effects associated with such emissions.
(See also Utility Study at ES-12 (noting higher population
concentrations surrounding oil-fired units). At the time of the
proposed rule, we recognized, however, the uncertainties in the data
underlying our ``appropriate'' finding for oil-fired units based on
nickel emissions, and for that reason solicited information as to
whether nickel emissions from oil-fired plants currently pose a
hazard to public health.
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Once EPA determined that it was ``appropriate'' to regulate coal-
and oil-fired Utility Units under section 112 of the CAA, EPA next
concluded that it was also ``necessary'' to regulate HAP emissions from
such units under section 112. Interpreting the term ``necessary'' in
section 112(n)(1)(A), EPA found that it was necessary to regulate HAP
from coal- and oil-fired Utility Units ``because the implementation of
other requirements under the CAA will not adequately address the
serious public health and environmental hazards arising from such
emissions identified in the Utility RTC.'' See 65 FR 79830.
In light of the positive appropriate and necessary determination,
EPA in December 2000 listed coal- and oil-fired Utility Units on the
section 112(c) source category list. See 65 FR 79831 (our finding that
it is appropriate and necessary to regulate coal- and oil-fired Utility
Units under section 112 ``adds these units to the list of source
categories under section 112(c).''). Relying on CAA section 112(e)(4),
EPA explained in its December 2000 finding that neither the appropriate
and necessary finding under section 112(n)(1)(A), nor the associated
listing were subject to judicial review at that time. EPA did not add
natural-gas fired units to the section 112(c) list in December 2000
because it did not make a positive appropriate and necessary finding
for such units.
B. Litigation Challenging December 2000 Regulatory Finding
Shortly after issuance of the December 2000 Finding, an industry
group challenged the December 2000 finding in the United States Court
of Appeals for the District of Columbia Circuit (DC Circuit). UARG v.
EPA, 2001 WL 936363, No. 01-1074 (DC Cir. July 26, 2001). EPA moved to
dismiss the lawsuit on the basis of section 112(e)(4), which provides,
in pertinent part, that ``no action of the Administrator * * * listing
a source category or subcategory under subsection (c) of this section
shall be a final agency action subject to judicial review, except that
any such action may be reviewed under such section 7607 of this title
when the Administrator issues emission standards for such pollutant or
category.'' (Emphasis added.) (See CAA Section 112(e)(4).)
In its motion to dismiss the petition, EPA argued to the DC
Circuit, among other things, that the December 2000 listing of coal-
and oil-fired Utility Units was inseparable from the appropriate and
necessary finding and that the appropriate and necessary finding and
listing actions are not final agency actions pursuant to section
112(e)(4). See also 65 FR 79826. EPA further noted in its motion to
dismiss that both the finding and the listing would be subject to
additional notice and comment as part of the section 112(d) rulemaking.
See EPA's Motion to Dismiss, UARG v. EPA, 2001 WL 936363, No. 01-1074S
(``Because the decision to add coal and oil fired electric utility
steam generating units to the source category list is not yet final
agency action, it will be among the matters subject to further comment
in the subsequent [standards] rulemaking.''); 65 FR 79831 (noting that
issues related to the listing, such as ``the exact dimension of the
source category,'' will be subject to additional comment in the
emission standard rulemaking process). The DC Circuit dismissed the
challenge to the December 2000 finding for lack of jurisdiction based
on section 112(e)(4) of the CAA. The December 2000 finding and
associated listing are therefore not final agency actions.
C. January 30, 2004 Proposed Rule and March 2004 Supplemental Notice
On January 30, 2004, EPA published in the Federal Register a
proposed rule entitled ``Proposed National Emissions Standards for
Hazardous Air Pollutants; and, in the Alternative, Proposed Standards
of Performance for New and Existing Stationary Sources: Electric
Utility Steam Generating Units.'' (See 69 FR 4652 (January 30, 2004).)
In that rule, EPA proposed three alternative regulatory approaches.
First, EPA proposed to retain the December 2000 Finding and associated
listing of coal- and oil-fired Utility Units and to issue under section
112(d) maximum achievable control technology-based (MACT) emission
standards for both subcategories. Second, EPA alternatively proposed
revising the Agency's December 2000 Finding, removing coal and oil-
fired Utility Units from the section 112(c) list,\8\ and issuing final
standards of performance under CAA section 111 for new and existing
coal-fired units that emit Hg and new and existing oil-fired units that
emit nickel. Finally, as a third alternative, EPA proposed retaining
the December 2000 finding, removing coal and oil-fired Utility Units
from the section 112(c) list, and regulating Hg emissions from Utility
Units under CAA section 112(n)(1)(A).
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\8\ We did not propose revising the December 2000 finding for
gas-fired Utility Units because EPA continues to believe that
regulation of such units under section 112 is not appropriate and
necessary. We have not received any information that would cause us
to change our conclusion in this regard. In fact, the information
that we have received since the Utility Study only confirms the
conclusion we reached in December 2000. We therefore take no action
today with regard to the December 2000 finding for gas-fired Utility
Units.
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Shortly thereafter, on March 16, 2004, EPA published in the Federal
Register a supplemental notice of proposed rulemaking entitled
``Supplemental Notice of Proposed National Emission Standards for
Hazardous Air Pollutants; and, in the Alternative, Proposed Standards
of Performance for New and Existing Stationary Sources: Electric
Utility Steam Generating Units.'' See 69 FR 13298 (March 16, 2004). In
that
[[Page 15997]]
notice, EPA proposed certain additional regulatory text, which largely
governed the proposed section 111 standards of performance for Hg,
which included a cap-and-trade program. The supplemental notice also
proposed state plan approvability criteria and a model cap-and-trade
rule for Hg emissions from coal-fired Utility Units. The Agency
received thousands of comments on the proposed rule and supplemental
notice.\9\ Comments relating to the central issues concerning today's
action are addressed in this preamble. The remainder of our responses
are contained in the response to comments document which is in the
docket.\10\
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\9\ We initially estimated that we had over 680,000 submissions
from the public on the proposed rule and the supplemental notice,
which came primarily in the form of letters and e-mails. A recent
review of the electronic docket reveals that our initial estimate
was over-stated. The docket reflects approximately 500,000 separate
submissions from the public, about 5,000 of which represent unique
comments.
\10\ The response to comments document relevant to this rule is
called: ``Response to Significant Public Comments Concerning the
Proposed Revision of the December 2000 Appropriate and Necessary
Finding and Proposed Removal of Utility Units From the Section
112(c) List.''
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D. The December 2004 Notice of Data Availability
On December 1, 2004, EPA published in the Federal Register a notice
of data availability entitled ``Proposed National Emission Standards
for Hazardous Air Pollutants; and, in the Alternative, Proposed
Standards of Performance for New and Existing Stationary Sources,
Electric Utility Steam Generating Units: Notice of Data Availability.''
See 69 FR 69864 (December 1, 2004). EPA issued this notice to seek
additional information and input concerning: (1) Certain Hg data and
information that the Agency received in response to the proposed rule
and supplemental notice, (2) the different forms of Hg that are emitted
into the atmosphere from coal-fired Utility Units and how those forms
respond to different control technologies; and (3) a revised proposed
benefits methodology for assessing the benefits of Hg regulation. The
benefits methodology generally involves analyzing Hg emissions from
coal-fired Utility Units, conducting deposition modeling based on the
identified Hg emissions, and relating that deposition modeling to
methylmercury concentrations in fish. EPA conducts benefits analyses
for rulemakings consistent with the provisions of Executive Order
12866.
III. EPA's Interpretation of CAA Section 112(n)(1)(A)
As explained above, Congress treated Utility Units differently from
other major and area sources and provided EPA considerable discretion
in evaluating whether to regulate Utility Units under section 112.
Section 112(n)(1)(A) provides, in full:
The Administrator shall perform a study of the hazards to public
health reasonably anticipated to occur as a result of emissions by
electric utility steam generating units of pollutants listed under
subsection (b) of this section after imposition of the requirements
of this Act. The Administrator shall report the results of this
study to the Congress within 3 years after the date of the enactment
of the Clean Air Act Amendments of 1990. The Administrator shall
develop and describe in the Administrator's report to Congress
alternative control strategies for emissions which may warrant
regulation under this section. The Administrator shall regulate
electric utility steam generating units under this section, if the
Administrator finds such regulation is appropriate and necessary
after considering the results of the study required by this
subparagraph.
(Emphasis added.).
The italicized terms in the above paragraph are central terms in
section 112(n)(1)(A). Before we address our interpretation of these
terms, however, we again summarize the requirements of section
112(n)(1)(A). The first step under section 112(n)(1)(A), which is
addressed by the first three sentences of section 112(n)(1)(A),
concerns the completion of a study and submission of the results of
that study to Congress by November 15, 1993. The study is to examine
the hazards to public health from utility HAP emissions that are
reasonably anticipated to occur following imposition of the
requirements of the CAA and to identify alternative control strategies
for those HAP that may warrant regulation under section 112. The second
step, which is addressed by the last sentence of section 112(n)(1)(A),
requires EPA to determine whether regulation of Utility Units under
section 112 is appropriate and necessary considering, among other
things, the results of the study. Congress provided no deadline by
which this determination must be made.
Section 112(n)(1)(A) itself contains no clear standard to govern
EPA's analysis and determination of whether it is ``appropriate and
necessary'' to regulate utilities under section 112. The first sentence
of the subparagraph describes the scope of the study EPA was to
conduct. The sentence on EPA's ``appropriate and necessary'' finding
then says that the Agency must make that finding after considering the
results of the study. But Congress did not supply an actual definition
or test for determining whether regulation of utilities under section
112 is ``appropriate and necessary.'' Thus, EPA must supply a
reasonable interpretation of those terms to fill the gap. Chevron USA
Inc. v. NRDC, 467 U.S. 837 (1984).
Congress' direction on the study provides the only guidance in
section 112(n)(1)(A) about the substance of EPA's inquiry. Because the
statute provides no other explicit guidance, EPA has chosen to
extrapolate from Congress' description of the study to adopt a
reasonable interpretation of the phrase ``appropriate and necessary.''
The following sections describe how the Agency has used Congress'
guidance on the study to formulate different aspects of our
interpretation and application of the ``appropriate and necessary''
test.
A. Hazards to Public Health Reasonably Anticipated To Occur
In section 112(n)(1)(A), Congress directed EPA to perform a study
of ``hazards to public health'' that would likely result from utility
HAP emissions, before making any further decisions about regulating
utilities under section 112. Unlike other sections of the CAA, section
112(n)(1)(A) focuses only on hazards to public health. It does not
require that EPA study other factors, such as environmental effects
without any established pathways to human health effects. In contrast,
section 112(n)(1)(B) requires a separate EPA study, although not as a
precursor to a regulatory determination, of the ``health and
environmental effects'' of ``mercury emissions'' from a broad range of
sources. Also unlike Section 112(n)(1)(A), many of the other
requirements of section 112 explicitly require both an assessment of
human health effects and, in addition, an assessment of adverse
environmental effects. For example, the Administrator is charged with
periodically reviewing the list of Hazardous Air Pollutants and adding
pollutants that present a threat of either ``adverse human health
effects'' or ``adverse environmental effects.'' CAA Section 112(b)(2).
The Administrator examines area sources of HAPs to determine if they
present ``a threat of adverse effects to human health or the
environment.'' CAA Section 112(c)(3). The Administrator is to
prioritize action under section 112(d) after considering ``the known or
anticipated adverse effects of such pollutants on public health and
environment.'' CAA Section 112(e)(2)(A). Nor did Congress appear to
view the two terms as synonymous. Under section 112(f), the EPA
[[Page 15998]]
promulgates emission standards at a level ``with an ample margin of
safety'' to ``protect public health.'' CAA Section 112(f)(2)(A). The
Administrator may go further and impose more stringent standards to
protect against ``an adverse environmental effect'' only after
considering ``cost, energy, safety, and other relevant factors.'' Id.
As described above, section 112(n)(1)(A) also provides no clear
standard for analyzing public health effects--in contrast to, for
example, section 112(f). Under section 112(f), the issue is whether
additional regulation is needed to ``provide an ample margin of safety
to protect public health.'' Section 112(f) also expressly incorporates
EPA's pre-1990 two-part inquiry for evaluating what level of emission
reduction is needed to provide an ample margin of safety to protect
public health. See CAA section 112(f)(2)(B) (incorporating EPA's two-
part ample margin of safety inquiry, set forth at 54 FR 38044 September
14, 1989, which implemented the requirements of section 112 of the 1977
CAA).\11\ By contrast, section 112(n)(1)(A) neither includes the
``ample margin of safety to protect public health'' requirement, nor
does it incorporate EPA's pre-1990 ample margin of safety inquiry.
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\11\ Section 112 of the 1977 CAA directed EPA to promulgate
emission standards ``at the level which in * * * [the
Administrator's judgment] provides an ample margin of safety to
protect the public health.'' Congress substantially amended section
112 in 1990 and enacted several new provisions. Congress
specifically incorporated the ``ample margin of safety to protect
public health'' requirement into section 112(f), which applies to
any source category that is regulated under section 112(d)(2) and
(d)(3). Significantly, Congress did not include the ``ample margin
of safety'' language in section 112(n)(1)(A). Instead, Congress
directed EPA to assess the ``hazards to public health reasonably
anticipated to occur'' from utility HAP emissions after imposition
of the requirements of the CAA, and then determine whether Utility
unit emissions should be regulated under section 112 of the CAA.
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Because of the focus on ``public health'' in the section
112(n)(1)(A) study requirement, and because as discussed above Congress
did not define the scope of the ``appropriate and necessary'' finding,
EPA is reasonably interpreting section 112(n)(1)(A) to base that
finding on an assessment of whether utility HAP emissions likely would
result in ``hazards to public health.''
Moreover, EPA reasonably interprets section 112(n)(1)(A) not to
require the Agency either to study or to base its ``appropriate and
necessary'' finding on an assessment of environmental effects unrelated
to public health.
As described above, Section 112(n)(1)(A) requires only that the
Administrator ``consider'' the results of the public health study
before determining whether utility regulation is ``appropriate and
necessary.'' This mild direction, when paired with the considerable
discretion inherent in any judgment about whether an action is
``appropriate and necessary,'' has led EPA to conclude that the statute
permits the agency to consider other relevant factors when determining
whether to regulate emissions from utility units under section 112.
This is not to say, however, that EPA believes it may ignore the
context of section 112(n) in making its determination.
The Supreme Court has recognized that ``where Congress includes
particular language in one section of a statute but omits it in another
section of the same Act,'' as here, where section 112(n)(1)(A) refers
to public health and conspicuously omits any reference to adverse
environmental effect, ``it is generally presumed that Congress acts
intentionally * * * in the disparate inclusion or exclusion.'' Russello
v. United States, 464 U.S. 16, 23 (1983). The only direction that
Congress explicitly provided to guide our ``appropriate and necessary''
finding was that we consider the results of a study of only those
``hazards to public health'' that the agency ``reasonably anticipate[s]
to occur.''
EPA must reconcile the broad discretion to determine what is
``appropriate and necessary'' with the implicit Congressional decision
that information about environmental effects unrelated to human health
effects was not needed for that determination. Rather than conclude
that EPA is prohibited from considering environmental effects, however,
EPA interprets section 112(n)(1)(A) to permit the agency to consider
other relevant factors as part of its ``appropriate and necessary''
determination, as refined further below, but these factors may not
independently, or in conjunction with one another, justify regulation
under section 112(n) when EPA has concluded that hazards to U.S. public
health are not reasonably anticipated to occur. Compare CAA section
112(f)(2)(A) (Administrator may set a more stringent standard than is
required to protect health if necessary, considering factors such as
cost, to prevent an adverse environmental effect).
In evaluating hazards to public health under section 112(n)(1)(A)
we look at various factors, including, for example, the affected
population, the characteristics of exposure (e.g., level and duration),
the nature of the data, including the uncertainties associated with the
data, and the nature and degree of health effects. In terms of
assessing health effects, we have numerous tools at our disposal. See
Section VI.H (for fuller discussion of factors relevant to assessing
the hazards to public health). For example, for cancer effects, we can
assess the lifetime excess cancer risk, and for other effects, we look
to tools, such as the reference dose.\12\ As explained below, the
``hazards to public health reasonably anticipated to occur'' standard
is relevant not only for the Study, but also for the appropriate and
necessary determination.
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\12\ Section VI below discusses the reference dose (``RfD'') in
detail.
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EPA has also taken note of the context for assessing ``hazards to
public health,'' for the language of section 112(n)(1)(A), calls for an
analysis of the ``hazards to public health'' reasonably anticipated to
``occur as a result of emissions by electric utility steam generating
units.'' (Emphasis added.) Section 110(a)(2)(D) provides an instructive
comparison in this regard. In section 110(a)(2)(D), Congress required
that each state implementation plan contain adequate provisions
``prohibiting * * * any source or other type of emissions activity
within the State from emitting any air pollutant in amounts'' that will
``contribute significantly to nonattainment'' of the national ambient
air quality standards. This provision demonstrates that Congress knew
how to require regulation of emissions of air pollutants even where the
pollutants themselves do not cause a problem, but rather only
``contribute to a problem.'' Unlike section 110(a)(2)(D), in section
112(n)(1)(A), Congress focused exclusively on the ``hazards to public
health'' of HAP emissions ``result[ing] from'' Utility Units. Rather,
it is the EPA study performed pursuant to section 112(n)(1)(B), not the
inquiry under section 112(n)(1)(A), that examines all current
anthopogenic sources of Hg emissions and their effects on human health
and the environment. EPA has concluded that its inquiry under section
112(n)(1)(A) may reasonably focus solely on whether the utility HAP
emissions themselves are posing a hazard to public health. This focus
on utility emissions only is consistent with Congress' overall decision
to provide for separate treatment of utilities in section 112(n)(1)(A).
B. Imposition of the Requirements of This Act
Congress required EPA to examine the hazards to public health from
utility emissions ``after imposition of the requirements of this Act.''
The phrase ``imposition of the requirements of th[e] Act'' is
susceptible to different
[[Page 15999]]
interpretations because Congress did not specify the scope of the
requirements under the CAA to be considered or, more importantly, the
time period over which the imposition of requirements was to be
examined. EPA reasonably interprets the phrase ``imposition of the
requirements of th[e] Act'' to include not only those requirements
already imposed and in effect, but also those requirements that EPA
reasonably anticipates will be implemented and will result in
reductions of utility HAP emissions. This interpretation is reasonable
in view of the fact that Congress called for the study to be completed
within three years of enactment of the 1990 CAA Amendments. At such
time, EPA could have only forecast, to the extent possible, how
implementation of the requirements of the CAA would impact utility HAP
emissions, based on the science and the state of technology at the
time.\13\
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\13\ Although the December 2000 finding does not provide an
interpretation of the phrase ``after imposition of the requirements
of the[e] Act,'' the Utility Study, on which that finding was based,
does account for the phrase by evaluating utility HAP emission
levels in 2010. See Utility Study ES-2 (the ``2010 scenario was
selected to meet the section 112(n)(1)(A) mandate to evaluate
hazards `after imposition of the requirements of 'the CAA.''). We do
not believe that the December 2000 finding or the January 2004
proposal properly give effect to all of the terms of section
112(n)(1)(A), including the first sentence of section 112(n)(1)(A).
We therefore provide our interpretation of the central terms in that
sentence above, as those terms are relevant to the final actions we
are taking today.
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We are interpreting the phrase ``requirements of th[e] Act''
broadly to include CAA requirements that could either directly or
indirectly result in reductions of utility HAP emissions. For example,
certain provisions of the CAA that affect Utility Units, such as the
requirements of Title I and Title IV, require controls on pollutants
like SO2 or NOX. Although these pollutants are
not HAP, the controls that are required to achieve the needed
reductions have the added effect of reducing HAP emissions. Thus, given
our interpretation of the phrase ``imposition of the requirements of
th[e] Act,'' we read the first sentence of section 112(n)(1)(A) as
calling for a study of the hazards to public health from utility HAP
emissions that EPA reasonably anticipates would occur after
implementation of the CAA requirements that EPA, at the time of the
study, should have reasonably anticipated would be implemented and
would directly or indirectly result in reductions of utility HAP
emissions.
Finally, it is telling that Congress directed EPA to examine the
utility HAP emissions remaining ``after imposition of the requirements
of th[e] Act,'' because there is no other provision in section 112 that
calls for EPA to examine the requirements of the CAA in assessing
whether to regulate a source category under section 112.\14\ Congress
plainly treated Utility Units differently from other source categories,
and that special treatment reveals Congress' recognition that Utility
Units are a broad, diverse source category that is subject to numerous
CAA requirements, including requirements under both Title I and Title
IV, and that such sources should not be subject to duplicative or
otherwise inefficient regulation.\15\ See 136 Cong. Rec. H12911, 12934
(daily ed. Oct. 26, 1990) (Statement of Congressman Oxley) (stating
that the conferees adopted section 112(n)(1)(A) ``because of the logic
of basing any decision to regulate on the results of scientific study
and because of the emission reductions that will be achieved and the
extremely high costs that electric utilities will face under other
provisions of the new Clean Air Act amendments.'').
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\14\ Section 112(m)(6) provides an instructive comparison
because it requires EPA to examine the other provisions of section
112, and to determine whether those provisions are adequate to
prevent serious adverse effects to public health and the environment
associated with atmospheric deposition to certain waterbodies.
Section 112(m)(6) also requires EPA to promulgate additional
regulations setting emission standards or control requirements, ``in
accordance with'' section 112 and under the authority of section
112(m)(6), if EPA determines that the other provisions of section
112 are adequate, and such regulations are appropriate and necessary
to prevent serious adverse public health and environmental effects.
Section 112(n)(1)(A) provides EPA far greater discretion because
under that section, EPA is not only to evaluate the reasonably
anticipated public health hazards remaining ``after imposition of
the requirements of th[e] Act,'' but also to determine whether to
regulate Utility Units under section 112 of the CAA at all.
\15\ As noted elsewhere, section 112(n)(1)(A) was included in
the House Committee bill and adopted by the House; while the Senate
included a different provision. In the Conference Committee, the
House version prevailed. Sen. Durenberger, a Senate conferee and an
evident opponent of the provision, alluded to another purpose for
the provision, which concerns the fact that ``mercury is a global
problem.'' Legislative History of the Clean Air Act Amendments of
1990, at 872 (Oct. 27, 1990) (statement of Sen. Durenberger). Based
on Sen. Durenberger's statement, it appears that one of the reasons
for the wide deference Congress accorded EPA under section
112(n)(1)(A) was to allow EPA to account for the fact that Hg
emissions from U.S. utilities are a very small part of overall Hg
emissions, and therefore that EPA should exercise discretion in
considering the uncontrollable amount of risk from Hg that would
remain regardless of the extent to which U.S. utilities are
controlled.
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C. Appropriate and Necessary After Considering the Results of the Study
Section 112(n)(1)(A) requires EPA to make a determination as to
whether regulation of Utility Units under section 112 is ``appropriate
and necessary.'' Congress did not define the terms ``appropriate'' and
``necessary,'' but provided that regulation of Utility Units under
section 112 could occur only if EPA determines that such regulation is
both ``appropriate'' and ``necessary.''
1. Considering the Results of the Study
The appropriate and necessary determination is to be made only
after ``considering the results of the study'' required under section
112(n)(1)(A). We interpret the phrase ``considering the results of the
study'' to mean that EPA must consider the results of the study in
making its determination, but that EPA is not foreclosed from analyzing
other relevant information that becomes available after completion of
the study. This interpretation is reasonable because section
112(n)(1)(A) contains no deadline by which EPA must determine whether
it is ``appropriate and necessary'' to regulate Utility Units under
section 112.
Moreover, nothing in section 112(n)(1)(A) suggests that EPA is
precluded from considering new relevant information obtained after
completion of the Utility Study in determining whether regulation of
Utility Units under section 112 is appropriate and necessary. Indeed,
the term ``considering'' in section 112(n)(1)(A) is analogous to the
terms ``based on'' or ``including,'' which are neither limiting nor
exclusive terms.\16\ In a recent case, the DC Circuit rejected an
argument advanced by the petitioners that an EPA rule was invalid
because the statute required EPA to promulgate the regulation ``based
on the study,'' and according to petitioners EPA's rule was not based
on a study that met the requirements of the CAA. Sierra Club v. EPA,
325 F.3d 374 (DC Cir. 2003). In rejecting petitioners' arguments, the
Court held, among other things, that ``the statute doesn't say that the
rule must be based exclusively on the study.'' Sierra Club v. EPA, 325
F.3d at 377 (emphasis in original); See also United States v. United
Technologies Corp., 985 F.2d 1148, 1158 (2d Cir. 1993) (``based upon''
does not mean ``solely''); McDaniel v. Chevron Corp., 203 F.3d 1099,
1111 (9th Cir. 2000). Consistent with this reasoning, EPA reasonably
interprets the phrase ``considering the results of the study,'' to mean
that EPA must consider the study, but that it can consider other
relevant information obtained after completion of the study. Congress
could not have reasonably intended for EPA to
[[Page 16000]]
ignore relevant information concerning HAP emissions from Utility Units
solely because that information was obtained after completion of the
Utility Study.\17\
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\16\ In fact, the term ``considering,'' on its face, is less
limiting than the phrase ``based on.''
\17\ Consistent with this interpretation, in December 2000, EPA
relied not only on the Utility Study, but also on certain
information concerning Hg obtained after completion of the study,
including actual emissions data from coal-fired plants for calendar
year 1999 and a report from the National Academy of Sciences on the
health effects of methylmercury. See 65 FR 79825-27.
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2. Appropriate and Necessary
The condition precedent for regulating Utility Units under section
112 is whether such regulation is ``appropriate'' and ``necessary.''
These are two very commonly used terms in the English language, and
Congress has not ascribed any particular meaning to these terms in the
CAA. The legislative history does not resolve Congress' intent with
regard to these terms. We therefore first examine the structure of
section 112(n)(1)(A) and then discuss our interpretation of the terms
``appropriate'' and ``necessary.''
a. Examining the Structure of Section 112(n)(1)(A). In interpreting
the terms ``appropriate'' and ``necessary'' in section 112(n)(1)(A), we
begin with the structure of section 112(n)(1)(A). As an initial matter,
the order of the terms in the phrase ``appropriate and necessary''
suggests that the first decision EPA must make is whether regulation of
Utility Units under section 112 is ``appropriate.'' Even if EPA
determines that regulation of Utility Units under section 112 is
appropriate, it must still determine whether such regulation is also
necessary. Were EPA to find, however, that regulation of Utility Units
under section 112 met only one prong, then regulating Utility Units
under section 112 would not be authorized by the statute.
The structure of section 112(n)(1)(A) also reveals that the
appropriate and necessary finding is to be made by reference to the
reasonably anticipated public health risks of utility HAP emissions
that remain after ``imposition of the requirements of th[e] Act.'' The
first sentence of section 112(n)(1)(A) contains an important direction
to EPA, which sets the predicate for the entire provision. That first
sentence calls for EPA to identify the hazards to public health
reasonably anticipated to occur as a result of the utility HAP
emissions remaining ``after imposition of the requirements of th[e]
Act.'' Stated differently, Congress wanted EPA to identify the utility
HAP emissions that would remain ``after imposition of the requirements
of th[e] Act'' and identify the hazards to public health reasonably
anticipated to occur as the result of such emissions. As noted above,
we interpret the phrase ``imposition of the requirements of th[e] Act''
to include those CAA requirements that EPA should have reasonably
anticipated would be implemented and would result in reductions of
utility HAP emissions.\18\ Congress' focus on the other requirements of
the CAA reflects its recognition that Utility Units are subject to
numerous CAA provisions and its intent to avoid duplicative and
unnecessary regulation. We therefore reasonably conclude that the
appropriate and necessary finding is to be made by reference to the
reasonably anticipated public health risks from utility HAP emissions
that remain ``after imposition of the requirements of th[e] Act.''
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\18\ The comments of Rep. Oxley, a member of the Conference
Committee, about section 112(n)(1)(A) support EPA's interpretation
of that provision. Rep. Oxley stated:
Pursuant to section 112(n), the Administrator may regulate
fossil fuel fired electric utility steam generating units only if
the studies described in section 112(n) clearly establish that
emissions of any pollutant, or aggregate of pollutants, from such
units cause a significant risk of serious adverse effects on the
public health. Thus, if the Administrator regulates any of these
units, he may regulate only those units that he determines--after
taking into account compliance with all other provisions of the CAA
and any other federal, state or local regulation and voluntary
emission reductions--have been demonstrated to cause a significant
threat of adverse effects on public health.
136 Cong. Rec. H12911, 12934 (daily ed. Oct. 26, 1990)
(Statement of Rep. Oxley) (emphasis added).
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b. EPA's interpretations of the terms ``appropriate'' and
``necessary.'' (i) Appropriate. In December 2000, EPA found that it was
appropriate to regulate coal- and oil-fired Utility Units under section
112. At that time, we did not provide an interpretation of the term
``appropriate.'' Instead, we focused on the following facts and
circumstances. We first found that it was ``appropriate'' to regulate
coal- and oil-fired Utility Units under section 112 because ``mercury
in the environment presents significant hazards to public health.'' See
65 FR 79830. We also determined that it was appropriate to regulate
oil-fired Utility Units based on the uncertainties ``regarding the
extent of the public health impact from HAP emissions from'' such
units. See 65 FR 79830. Finally, we found that it was appropriate to
regulate HAP emissions from coal-and oil-fired units under section 112
because we had identified control options that we anticipated would
effectively reduce certain HAP emissions. We also indicated that
certain control options could ``greatly reduc[e] mercury control
costs.'' See 65 FR 79830.
In January 2004, we proposed reversing our ``appropriate'' finding
in large part. Specifically, we proposed that it is not ``appropriate''
to regulate coal-fired units on the basis of non-Hg HAP and oil-fired
units on the basis of non-Ni HAP because the record that was before the
Agency in December 2000 indicates that emissions of such pollutants do
not result in hazards to public health. See Section IV.B.
Webster's dictionary defines the term ``appropriate'' to mean
``especially suitable or compatible.'' Miriam-Webster's Online
Dictionary, 10th ed. Determining whether something is ``especially
suitable or compatible'' for a particular situation requires
consideration of different factors. In section 112(n)(1)(A), Congress
requires EPA to determine whether it is ``appropriate'' to regulate
Utility Units under section 112. In making this determination, we begin
as we did in December 2000, by assessing the paramount factor, which is
whether the level of utility HAP emissions remaining ``after imposition
of the requirements of th[e] Act'' would result in hazards to public
health. We determine whether the remaining utility HAP emissions cause
hazards to public health by analyzing available health effects data and
assessing, among other things, the uncertainties associated with those
data, the weight of the scientific evidence, and the extent and nature
of the health effects. See Section VI. If the remaining HAP emissions
from Utility Units do not result in hazards to public health, EPA does
not believe that it would be ``especially suitable''--i.e.,
``appropriate''--to regulate such units under section 112. In this
situation, there would be no need to consider any additional factors
under the ``appropriate'' inquiry because the threshold fact critical
to making a finding that it is appropriate to regulate Utility Units
under section 112 would be missing.
Even if the remaining utility HAP emissions cause hazards to public
health, it still may not be appropriate to regulate Utility Units under
section 112 because there may be other relevant factors particular to
the situation that would lead the Agency to conclude that it is not
``especially suitable'' or ``appropriate'' to regulate Utility Units
under section 112. For example, it might not be appropriate to regulate
the utility HAP emissions remaining ``after imposition of the
requirements of th[e] Act,'' if the controls mandated under section
112(d) would be ineffective at eliminating or reducing the identified
hazards to public health. Similarly, it might not be appropriate to
regulate the
[[Page 16001]]
remaining utility HAP emissions under section 112 if the health
benefits expected as the result of such regulation are marginal and the
cost of such regulation is significant and therefore substantially
outweighs the benefits. These examples illustrate that situation-
specific factors, including cost, may affect whether it ``is
appropriate'' to regulate utility HAP emissions under section 112.\19\
(See Section 112(n)(1)(A).)
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\19\ Nothing precludes EPA from considering costs in assessing
whether regulation of Utility Units under section 112 is appropriate
in light of all of the facts and circumstances presented. The DC
Circuit has indicated that regulatory provisions should be read with
a presumption in favor of considering costs: ``It is only where
there is `clear congressional intent to preclude consideration of
cost' that we find agencies barred from considering costs.
[Citations omitted.]'' Michigan v. EPA, 213 F.3d 663, 678 (DC Cir.
2000), cert. den., 532 U.S. 903 (2001) (upholding EPA's
interpretation of ``contribute significantly'' under CAA section
110(a)(2)(D) to include a cost component). The Supreme Court's
decision in Whitman v. American Trucking Assn's (ATA), Inc., 531
U.S. 457 (2001), is not to the contrary. In that case, the Court
held that EPA lacked authority to consider costs in the context of
setting the national ambient air quality standards under CAA section
109(b)(1), because the ``modest words `adequate margin' and
`requisite' ' in that section do not ``leave room'' to consider
cost. 531 U.S. 466. By contrast, EPA is not setting emission
standards in today's action, but rather determining, as Congress
directed, whether it is ``appropriate'' and ``necessary'' to
regulate Utility Units under CAA section 112. The terms
``appropriate'' and ``necessary'' are broad terms, which by contrast
to the terms at issue in ATA do, in fact, leave room for
consideration of costs in deciding whether to regulate utilities
under section 112. Moreover, the legislative history of section
112(n) indicates that Congress intended for EPA to consider costs.
See 136 Cong. Rec. H12911, 12934 (daily ed. Oct. 26, 1990)
(statement of Rep. Oxley) (``[T]he conference committee produced a
utility air toxics provision that will provide ample protection of
the public health while avoiding the imposition of excessive and
unnecessary costs on residential, industrial and commercial
consumers of electricity.''). Finally, section 112(n)(1)(A) requires
EPA to consider alternative control strategies, and the focus on
such strategies may reasonably be read as further evidence of the
relevance of costs. See, e.g., 65 FR 79830 (discussing costs in
relation to certain technologies).
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It cannot be disputed that Congress under section 112(n)(1)(A)
entrusted EPA to exercise judgment by evaluating whether regulation of
Utility Units under section 112 is, in fact, ``appropriate.'' We
believe that in exercising that judgment, we have the discretion to
examine all relevant facts and circumstances, including any special
circumstances that may lead us to determine that regulation of Utility
Units under CAA section 112 is not appropriate.\20\
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\20\ Significantly, in December 2000, we acknowledged that
factors other than the hazards to public health resulting from
utility HAP emissions should be examined in determining whether
regulation of Utility Units is appropriate under section 112.
Indeed, after concluding that the Hg emissions from coal-fired
Utility Units caused hazards to public health, we proceeded with the
appropriate inquiry and examined whether there were any control
technologies that could effectively reduce Hg. We also commented on
the costs of achieving such reductions. See, e.g., 65 FR 79828,
79830.
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(ii) Necessary. Like the ``appropriate'' finding, the ``necessary''
finding must be made by reference to the utility HAP emissions
remaining after imposition of the requirements of the CAA.
Specifically, we interpret the term ``necessary'' in section
112(n)(1)(A) to mean that it is necessary to regulate Utility Units
under section 112 only if there are no other authorities available
under the CAA that would, if implemented, effectively address the
remaining HAP emissions from Utility Units. Assessing whether an
alternative authority would effectively address the remaining utility
HAP emissions would involve not only: (a) An analysis of whether the
alternative legal authority, if implemented, would address the
identified hazards to public health, which was a concept specifically
addressed in December 2000 and in the January 2004 proposal, but also
(b) an analysis of whether the alternative legal authority, if
implemented, would result in effective regulation, including, for
example, its cost-effectiveness and its administrative effectiveness.
See Michigan v. EPA, 213 F.3d, 663, 678 (addressing consideration of
costs).
This interpretation of the term ``necessary'' differs slightly from
the interpretation advanced in December 2000 and January 2004. In
December 2000 and J
