Current through Register Vol. 63, No. 3, March 1, 2024
This rule establishes a risk protocol for performance of human
health and ecological risk assessments, including: General requirements for
risk assessments and specific requirements for baseline human health risk
assessments, baseline ecological risk assessments, residual risk assessments,
and probabilistic risk assessments.
(1) General requirements for risk assessments
include:
(a) Risks assessments shall consider
existing and reasonably likely future human exposures and significant adverse
effects to ecological receptors in the locality of the facility.
(b) Risk assessments may be conducted using
either deterministic or probabilistic risk assessment methodologies at the
discretion of the party conducting the risk assessment, provided the risk
assessment requirements of this rule are met.
(c) Sources of toxicity information to be
used in a risk assessment may include the following information to the extent
it is available and acceptable to the Department at the time a human health or
ecological risk assessment is prepared:
(A)
For human health risk assessments:
(i) U.S.
EPA IRIS Data Base;
(ii) U.S. EPA
HEAST Data Base;
(iii) HEAST
alternative method;
(iv) U.S.
EPA-NCEA Superfund Health Risk Technical Support Center;
(v) Other U.S. EPA documents or
databases;
(vi) ATSDR Toxicological
Profiles; or
(vii) Other refereed
technical publications.
(B) For ecological risk assessments:
(i) U.S. EPA AQUIRE Data Base;
(ii) U.S. EPA IRIS Data Base;
(iii) U.S. EPA HEAST Data Base;
(iv) U.S. EPA ASTER Data Base;
(v) U.S. EPA PHYTOTOX Data Base;
(vi) U.S. EPA Terrestrial Toxicity Data Base
(TERRATOX);
(vii) U.S. Fish and
Wildlife Service Technical Reports;
(viii) Oak Ridge National Laboratory
Toxicological Benchmark Technical Reports;
(ix) Other U.S. EPA documents or
databases;
(x) ATSDR Toxicological
Profiles; or
(xi) Other refereed
technical publications.
(C) In the absence of toxicity information
that is available and acceptable to the Department under paragraph (A) or (B),
the Department may require the development of acceptable site-specific toxicity
information.
(d) Risk
assessments may include use of transport and fate models, subject to Department
approval of the model and the data to be used for the parameters specified in
the model. The Department shall ensure than any transport and fate model
approved for use is capable of simulating all site conditions and contaminant
properties that might have a significant impact on site-specific contaminant
transport or fate.
(e) The
Department shall require appropriate sampling approaches and data quality
requirements to support the risk assessment and remedy selection
processes.
(f) A plausible
upper-bound or high-end exposure for both human health and ecological risk
assessments is the 90th percentile upper confidence limit on the arithmetic
mean of concentrations of hazardous substances that would be contacted by an
exposed receptor and reasonable maximum estimates of the exposure factors used
in the risk calculations, unless a greater or lesser best estimate is
acceptable to the Department.
(g)
The central tendency exposure for both human health and ecological risk
assessments is the arithmetic mean of concentrations that would be contacted by
an exposed receptor and mean estimates of the exposure factors used in the risk
calculations. Risk assessments utilizing only deterministic methods shall
provide both central tendency and upper-bound estimates of exposure and
risk.
(h) The use of population
risk estimates in addition to individual risk estimates is provided for as
follows:
(A) For human health risk
assessments, risk estimates shall be made only at the level of the
individual;
(B) For ecological risk
assessments, risk estimates shall be made:
(i) At the level of the individual for
species present in the locality of the facility if the species is listed as
threatened or endangered species pursuant to
16
U.S.C. 1531 et seq. or ORS
496.172;
or
(ii) At the level of the
population for all other plants or animals in the locality of the
facility.
(i)
Cumulative risk from multiple hazardous substances will be assessed by assuming
additivity of the risk posed separately by individual non-carcinogenic and
carcinogenic hazardous substances in the locality of the facility, unless the
Department determines that an assumption of synergism, antagonism, or other
toxic response is appropriate or it is demonstrated to the satisfaction of the
Department that an assumption other than additivity is appropriate.
(j) Appropriate sources of exposure factor
information may include, but are not limited to, the following information, to
the extent it is available and acceptable to the Department at the time human
health and ecological risk assessments are prepared:
(A) U.S. EPA Risk Assessment Guidance for
Superfund. Volume 1. Human Health Evaluation Manual, Part A, 1989;
(B) U.S. EPA Risk Assessment Guidance for
Superfund Volume 2. Environmental Evaluation Manual, 1989;
(C) U.S. EPA Risk Assessment Guidance for
Superfund. Volume 1. Human Health Evaluation Manual, Supplemental Guidance -
Standard Default Exposure Factors, 1991;
(D) U.S. EPA Wildlife Exposure Factors
Handbook. Volumes 1 and 2, 1993; and
(E) U.S. EPA Exposure Factors Handbook,
1990.
(2)
Baseline human health risk assessments shall include, but are not limited to,
the following information:
(a) A conceptual
site model describing contaminant sources, release mechanisms, transport routes
and media, potential human receptor populations, and relevant exposure
scenarios based on current and reasonably likely future land and water
uses;
(b) Data quality objectives
for the human health risk assessment based on the conceptual site
model;
(c) Exposure analysis
including identification and selection of contaminants of concern, a detailed
description of potentially exposed populations and exposure routes, and a
quantitative estimate of exposure for both current and reasonably likely future
land and water use scenarios;
(d)
Toxicity analysis including a summary of current information regarding the
carcinogenic effects, noncarcinogenic effects, bioconcentration potential,
bioaccumulation potential, biomagnification potential, and persistence of the
identified contaminants of concern as well as current slope factors and
reference doses;
(e) Risk
characterization presenting the quantitative human health risks potentially
associated with the facility, a discussion of any available facility-specific
human health studies, an explicit discussion of risks associated with the
bioconcentration potential, bioaccumulation potential, biomagnification
potential, and persistence of each contaminant, and consideration of any other
available, published, and peer-reviewed scientific information on other sources
of stress as appropriate; and
(f)
Quantitative and qualitative uncertainty analysis as appropriate for each
element of the risk assessment.
(3) Baseline ecological risk assessments
shall include, but are not limited to, the following information:
(a) Problem formulation to include
identification of contaminants of ecological interest, potential ecological
effects, ecological receptors, relevant exposure pathways, initial definition
of assessment and measurement endpoints, all with respect to current and
reasonably likely future land and water uses, and described in a conceptual
site model;
(b) Data quality
objectives for the ecological risk assessment based on the conceptual site
model, with emphasis on analytical detection limits appropriate for ecological
receptors;
(c) Exposure analysis to
include identification and selection of potential contaminants of ecological
concern, identification and selection of target ecological receptors, an
exposure pathway model relating target receptors, exposure routes and
measurement endpoints, and a quantitative estimate of exposure for both current
and reasonably likely future land and water use scenarios;
(d) Ecological response analysis including a
summary of current information regarding the toxicological effects, ecological
effects, bioconcentration potential, bioaccumulation potential,
biomagnification potential, and persistence of the identified contaminants of
ecological concern, as well as ecological benchmark values;
(e) Risk characterization presenting the
quantitative ecological risks potentially associated with the facility,
identification of contaminants of ecological concern, a discussion of any
available facility-specific ecological studies, an explicit discussion of risks
associated with the bioconcentration potential, bioaccumulation potential,
biomagnification potential, and persistence of each contaminant, and
consideration of any other available, published and peer-reviewed scientific
information on other sources of stress as appropriate;
(f) As appropriate, the potential for
significant adverse effects on the health or viability of individual ecological
receptors or local populations may be evaluated with a weight-of-evidence
analysis or population viability analysis, respectively. These analyses may
utilize field studies, laboratory investigations, appropriate population
models, or any combination of these or other methods acceptable to the
Department; and
(g) Quantitative
and qualitative uncertainty analysis as appropriate for each element of the
risk assessment.
(4)
Residual risk assessments shall be conducted prior to selection or approval of
the remedial action, and shall include:
(a) A
quantitative assessment of the risk resulting from concentrations of untreated
waste or treatment residuals remaining at the facility at the conclusion of any
treatment or excavation and offsite disposal activities taking into
consideration current and reasonably likely future land and water use scenarios
and the exposure assumptions used in the baseline risk assessment;
and
(b) A qualitative or
quantitative assessment of the adequacy and reliability of any institutional or
engineering controls to be used for management of treatment residuals and
untreated hazardous substances remaining at the facility.
(c) The combination of (a) and (b) constitute
a residual risk assessment that must demonstrate to the Department that
acceptable levels of risk as defined by OAR 340-122-0115 would be attained in
the locality of the facility.
(5) Probabilistic techniques may be applied
to human health and ecological risk assessments. The purpose of this rule is to
establish a minimum level of technical performance for probabilistic risk
assessments submitted to the Department.
(a)
Before the commencement of a probabilistic risk assessment, the following
issues shall be addressed:
(A) Current and
reasonably likely future land and water uses in the locality of the
facility;
(B) A site-specific
preliminary conceptual site model that relates potential receptors, hazardous
substances, and exposure pathways;
(C) Preliminary assessment endpoints for any
ecological risk assessment; and
(D)
Sources and characteristics of the distributions proposed for use in the
assessment.
(b) Based on
consideration of the items specified in subsection (5)(a) of this rule, a
probabilistic risk assessment may be performed in accordance with a work plan
approved by the Department.
(c) The
Department is not obligated to accept the results of a probabilistic risk
assessment, unless the information requirements set forth in subsection (5)(d)
of this rule or otherwise specified by the Department have been addressed in a
manner acceptable to the Department.
(d) The probabilistic risk assessment shall
include, but not be limited to, information regarding:
(A) All formulae used to estimate exposure
point values, toxicity (cancer slope factor, reference dose) values, ecological
benchmark values, hazard indices, and incremental lifetime cancer
risks;
(B) The probabilistic risk
assessment's use of input parameters expressed as either point estimates or
distributions. For each input parameter expressed as a distribution, the
following information shall be provided:
(i)
The shape of the full distribution;
(ii) To the extent practicable, the mean,
standard deviation, minimum, 5th percentile, 10th percentile, median, 90th
percentile, 95th percentile, and maximum of the specified
distribution;
(iii) Justification
for the use of each distribution explaining the rationale for its use and the
rejection of other relevant distributions. Justification shall be based on one
or more of the following:
(I) Distributions
presented in a refereed or peer-reviewed publication;
(II) Distributions available from the U.S.
Environmental Protection Agency or other state or federal government agency,
the American Society for Testing and Materials (ASTM), or any distributions
designated by the Department as default distributions;
(III) Expert or professional judgment;
or
(IV) Parametric distributions of
input variables fit quantitatively to measured data. For such distributions,
the following information shall be provided: parametric fits and the data on
the same axes; appropriate goodness-of-fit statistics; implications of any
important differences between the parametric fits and the data; and influence
of the statistical process or underlying mechanism creating the random variable
on the selection of the distribution used.
(iv) The extent to which input distributions
and their parameters capture and separately represent both stochastic
variability and knowledge uncertainty. This information shall comprise a
portion of, but not be a replacement for, a comprehensive discussion in the
body of the baseline risk assessment of the qualitative and quantitative
sources of uncertainty.
(C) Any correlations between or among input
variables that are known or expected to have the practical effect of
significantly affecting the risk assessment;
(D) For each output distribution resulting
from the probabilistic risk assessment, the following information:
(i) The shape of the full distribution and
location of the acceptable risk level; and
(ii) To the extent practicable, the mean,
standard deviation, minimum, 5th percentile, 10th percentile, median, 90th
percentile, 95th percentile, and maximum of the specified
distribution.
(E) A
probabilistic sensitivity analysis for all key input distributions conducted so
as to distinguish, to the extent possible, the effects of variability from the
effects of uncertainty in the input variables; and
(F) Justification for the selection of any
point estimate value incorporated into the probabilistic assessment explaining
the rationale for its selection and for the rejection of other relevant point
estimate values. Such justification for use shall be based on one or more of
the sources specified in subparagraph (5)(d)(B)(iii) of this rule.
(e) Probabilistic methods may be
applied to:
(A) Environmental media
contaminant concentration data;
(B)
Transport and fate modeling;
(C)
Exposure estimation;
(D) Human
toxicity estimation;
(E) Ecological
response estimation; or
(F) Risk
characterization.
[NOTE: Referenced documents are available from the
agency.]
Statutory/Other Authority: ORS
465.315
& 465.400
Statutes/Other Implemented: ORS
465.200-455,
465.900, 466.706-835 & 466.895