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Water: Regulatory Information

Summary of Proposed Rule Revising the Human Health Water Quality Criteria for Polychlorinated Biphenyls (PCBs) in the National Toxics Rule (NTR)


United States
Environmental Protection
Agency
Office of Water
4304
EPA-822-F-98-001
March 1998

Abstract

The U.S. Environmental Protection Agency is proposing a rule to revise the human health water quality criteria for Polychlorinated Biphenyls (PCBs) in the National Toxics Rule (NTR). When the NTR was promulgated, human health criteria for PCBs were calculated using the cancer potency factor entered in the Agency's Integrated Risk Information System (IRIS). The Agency, is now proposing revisions to the human health water quality criteria for PCBs in the NTR, based on the Agency's reassessment of the cancer potency of PCBs.

Background

On December 22, 1992, EPA promulgated the National Toxics Rule (NTR), which established numeric water quality criteria for priority toxic pollutants for fourteen States and Jurisdictions. The Federal promulgation brought these States into compliance with section 303(c)(2)(B) of the Clean Water Act, which requires states to adopt criteria for all toxic pollutants, the discharge or presence of which could interfere with state designated uses and for which EPA had published criteria.

Among the criteria promulgated in the NTR were human health water quality criteria for polychlorinated biphenyls (PCBs). A number of parties challenged the human health criteria for PCBs promulgated by EPA in the NTR. As part of a partial settlement agreement between General Electric Company and the Agency, EPA is now proposing revisions to the human health water quality criteria for PCBs in the NTR, based on the Agency's reassessment of the cancer potency of PCBs.

When the NTR was promulgated, human health criteria for PCBs were calculated using a cancer potency factor of 7.7 per mg/kg-day entered in the Agency's Integrated Risk Information System (IRIS). The Agency recently reassessed the cancer potency of PCBs, and issued a final report, PCBs: Cancer Dose-Response Assessment and Applications to Environmental Mixtures. The Agency now adopts an approach that distinguishes among PCB mixtures by using information on environmental mixtures and different exposure pathways. Based on this reassessment, for this proposed rule, EPA derived the human health criteria for PCBs using a cancer potency factor of 2 per mg/kg-day, a potency factor considered protective of children and adults who drink surface water and consume fish from water contaminated with PCBs.

Costs and Benefits

The proposed rule establishes water quality criteria that, by themselves, do not directly impose economic impacts. Criteria combined with State-adopted designated uses result in water quality standards, and costs can be incurred by regulated entities (i.e., point source dischargers) when water quality standards are translated into NPDES permit limits. Costs of compliance can vary significantly because of the wide range of control strategies available to dischargers.

However, the revised human health criteria EPA is proposing for PCBs are less stringent than those promulgated in the 1992 NTR. If states or jurisdictions implement NPDES permit limits consistent with these proposed criteria, the potential economic impacts will be less then those associated with the criteria promulgated in the 1992 NTR.


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