## Facts

- EPA issued its first toxic-pollutant effluent regulations under Clean Water Act (CWA) § 307(a), listing polychlorinated biphenyls (PCBs) and setting an effectively zero-discharge standard for PCB effluent from manufacturers of electrical equipment using PCBs.
- The administrative record described PCBs’ persistence in the environment, bioaccumulation and biomagnification in aquatic systems, toxicity to aquatic organisms at low concentrations, human exposure through diet and tissue residues, and evidence suggesting carcinogenic risk.
- EPA concluded that no discharge level could be identified that would protect health and the environment with an “ample margin of safety,” and therefore adopted a prohibition/near-prohibition approach.
- Multiple parties filed consolidated petitions for review: environmental petitioners argued the rule was under-protective in some respects; industry petitioners argued the rule was unauthorized or unsupported, particularly as applied to less-chlorinated PCBs.
- Petitioners challenged EPA’s authority in light of the later-enacted Toxic Substances Control Act (TSCA), EPA’s rulemaking procedures, and the evidentiary basis for the near-zero standard.

## Issues

1. Whether TSCA’s PCB provisions preempted or displaced EPA’s authority to regulate PCB effluent discharges under CWA § 307(a).
2. Whether EPA complied with CWA § 307(a) and APA procedural requirements in listing PCBs and promulgating final effluent standards.
3. Whether the administrative record adequately supported EPA’s determination that no safe level of PCB discharge could be set, including for less-chlorinated PCB congeners.
4. What level of judicial deference applies to EPA’s technical judgments, including extrapolation from incomplete toxicological data and selection of conservative assumptions.

## Decision

- The court upheld EPA’s PCB effluent regulations in all material respects and denied the petitions for review seeking to invalidate the rule.
- The court held TSCA did not preempt or bar EPA’s CWA § 307(a) authority; the statutes operate in overlapping, complementary fields.
- The court found EPA’s notice, hearing, and related rulemaking steps satisfied CWA § 307(a) and APA requirements; any minor timing or format concerns were not reversible.
- The court held EPA’s near-zero discharge standard was supported by the record and reflected permissible scientific and policy judgments, including treatment of less-chlorinated PCBs within the regulated class.

## Legal Principles

- Later-enacted toxic-substance legislation does not displace CWA toxic-effluent authority absent clear congressional intent; regulation of chemical manufacture and commerce (TSCA) can coexist with regulation of water discharges (CWA).
- CWA § 307(a) authorizes effluent standards that may include a prohibition on discharge for listed toxic pollutants.
- When Congress requires protection with an “ample margin of safety,” EPA may regulate despite scientific uncertainty and need not wait for conclusive proof of harm.
- Courts defer to EPA’s technical determinations and reasonable extrapolations from limited data so long as the agency considers relevant factors, explains its reasoning, and grounds its conclusions in evidence and rational inference.
- EPA may regulate a chemical family as a class, including less-studied congeners, where shared properties and record evidence support class-based risk management.

## Conclusion

The D.C. Circuit sustained EPA’s authority and methodology for imposing an effectively zero PCB effluent standard under CWA § 307(a), rejecting TSCA-based displacement arguments and holding that EPA’s conservative, record-based risk judgments satisfied procedural and substantive review.


Env't Def. Fund v. EPA, 598 F.2d 62 (D.C. Cir. 1978)