Pennsylvania Code
Title 25 - ENVIRONMENTAL PROTECTION
Part I - Department of Environmental Protection
Subpart A - Preliminary Provisions
Article II - Statements of Policy
Chapter 16 - WATER QUALITY TOXICS MANAGEMENT STRATEGY-STATEMENT OF POLICY
Subchapter A - GUIDELINES FOR DEVELOPMENT OF CRITERIA FOR TOXIC SUBSTANCES AND WATER QUALITY CRITERIA FOR TOXIC SUBSTANCES
GUIDELINES FOR DEVELOPMENT OF HUMAN HEALTH-BASED CRITERIA
Section 16.33 - Nonthreshold effects (cancer)
Current through Register Vol. 54, No. 52, December 28, 2024
(a) A nonthreshold effect is defined as an adverse impact, including cancer, for which no exposure greater than zero assures protection to the exposed individual. Thus, in contrast to the threshold concept discussed in § 16.32 (relating to threshold level toxic effects), the nonthreshold approach to toxics control is based upon the premise that there is no safe concentration of the toxic.
(b) The Department has determined that the regulation of carcinogens from a water quality perspective in accordance with the procedure specified in the following subsections will adequately and reasonably protect human health.
(c) The Department accepts the evaluation and extrapolation modeling used by the EPA to quantitate the carcinogenic risk of particular chemicals. Cancer risk level criteria are, therefore, adaptations of the EPA's cancer potency (slope) factors. Criteria based on cancer risk levels are average lifetime exposure values.
(d) The Department's water quality toxics management program controls carcinogens to an overall risk management level of one excess case of cancer in a population of one million (1 x 10-6). Expressing this another way, the probability of an individual getting cancer from an ambient water exposure to a carcinogen is increased by a factor of one in one million. This level appears to be protective of human health to a significant degree when compared to other risks encountered in life.
(e) The Department uses a 1 x 10-6 cancer risk level as specified in § 93.8a(d) (relating to toxic substances). Attainment of this risk level is predicated on exposure that includes drinking 2.4 liters of water and ingesting 22.0 grams of fish per day over a 70-year lifetime. Bioaccumulation of carcinogenic toxics in edible portions of fish are accounted for by use of bioaccumulation factors (BAFs).
(f) The Department will use the following guidelines in establishing criteria for nonthreshold toxics:
This section cited in 25 Pa. Code § 16.61 (relating to special provisions for the Great Lakes System).