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Chlorine Chemistry Council v. EPA

United States Court of Appeals for the District of Columbia Circuit
206 F.3d 1286 (2000)
ELI5:

Rule of Law:

Under the Safe Drinking Water Act, a federal agency must use the 'best available, peer-reviewed science' at the time of rulemaking. An agency acts arbitrarily and exceeds its statutory authority if it disregards its own contemporaneous scientific findings in favor of a prior, unsupported policy, even if it claims the action is 'interim' or awaits future scientific reports.


Facts:

  • Chloroform is a byproduct of the chlorination process used to disinfect drinking water and has been classified by the EPA as a probable human carcinogen.
  • Historically, the EPA's default assumption for carcinogens was a 'linear' model, meaning any level of exposure poses some risk, which supported a Maximum Contaminant Level Goal (MCLG) of zero.
  • In 1997, the EPA formed an advisory group to analyze new information regarding disinfection byproducts.
  • In a 1998 Notice of Data Availability, the EPA announced its agreement with an expert panel's conclusion that chloroform is a 'nonlinear' or 'threshold' carcinogen, meaning it does not pose a cancer risk below a certain dose.
  • Based on this nonlinear mode of action, the EPA's own science indicated that an MCLG between 300 and 600 parts per billion (ppb) would be safe from carcinogenic effects.
  • Despite these findings, in its December 1998 final rule, the EPA set the MCLG for chloroform at zero.
  • The EPA justified its decision by stating it needed more time for its Science Advisory Board (SAB) to review the science, a process that could not be completed before the statutory deadline for the rule.

Procedural Posture:

  • The Chlorine Chemistry Council and other petitioners petitioned the U.S. Court of Appeals for the D.C. Circuit for review of the EPA's final rule setting the MCLG for chloroform.
  • After the case was briefed, the EPA moved for a voluntary remand to consider an upcoming Science Advisory Board report but did not offer to vacate the challenged rule; the court denied the motion.
  • On the day of oral argument, the EPA released a draft of the SAB report and subsequently filed a motion asking the court to vacate the MCLG.

Locked

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Issue:

Does the Environmental Protection Agency (EPA) violate the Safe Drinking Water Act's mandate to use the 'best available, peer-reviewed science' when it sets a Maximum Contaminant Level Goal (MCLG) of zero for a substance, despite its own contemporaneous scientific findings indicating that the substance is a threshold carcinogen for which a non-zero MCLG is scientifically appropriate?


Opinions:

Majority - Williams, J.

Yes. The EPA violates the Safe Drinking Water Act's mandate when it promulgates a rule that is contrary to the best available scientific evidence at the time of the rulemaking. The statute unequivocally requires the EPA to use the 'best available' science, which means the best science available at the time of the agency's action, not science that may become available in the future. Here, the EPA's own 1998 findings concluded that chloroform is a threshold carcinogen, making a zero MCLG scientifically indefensible. The agency cannot ignore its own scientific conclusions by claiming its action is 'interim' or by citing the need to await a future SAB report. While uncertainty about some technical factors might justify choosing a conservative non-zero MCLG within the scientifically supported range, it provides no justification for choosing an MCLG of zero, which lies entirely outside that range.



Analysis:

This decision significantly reinforces judicial oversight of agency rulemaking, particularly in science-intensive areas. It establishes that an agency cannot use administrative convenience, procedural delays, or the mere possibility of future scientific developments to justify ignoring the 'best available' science as mandated by statute. The case solidifies the principle that an agency's final action must be consistent with its own scientific record at the time the decision is made. This precedent limits agency discretion to revert to outdated 'default' assumptions when new, robust scientific evidence points to a different conclusion, thereby promoting science-based regulation and holding agencies accountable to their statutory obligations.

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