The U.S. District Court for the District of Columbia has rejected chemical industry challenges to an agency's decision to list the chemical styrene in the Twelfth Report on Carcinogens as "reasonably anticipated" to be a cancer-causing agent. A major styrene trade association and a manufacturer of the substance had sued the U.S. Department of Health and Human Services (HHS) for including styrene in the report.

The background

The Public Health Service Act of 1978 directs the Secretary of HHS to prepare a Report on Carcinogens every other year that identifies substances with the potential to cause cancer. The National Toxicology Program (NTP) prepares the report to be issued on behalf of the Secretary of HHS. NTP does not issue or enforce regulations; it only conducts its own evaluations of the scientific evidence on carcinogens and publishes its conclusions.

The statute requires that the report contain a list of all substances that are "known to be carcinogens" or "may reasonably be anticipated" to be carcinogens. Under NTP criteria, a substance is known to be a human carcinogen if there is sufficient evidence of carcinogenicity from studies in humans. A substance is reasonably anticipated to be a human carcinogen if there is some evidence of carcinogenicity from studies in humans, evidence of carcinogenicity from animal studies, or other evidence to suggest a substance causes cancer.

How styrene got on the list

The NTP nominated styrene for review in 2004 after an international body listed styrene as "possibly carcinogenic to humans." After a seven-year, multistep review process that included peer review and an opportunity for public comment, NTP finalized the report, which lists styrene as "reasonably anticipated to be a human carcinogen." The Secretary of HHS approved and published the report on June 10, 2011.

The same day, the styrene industry filed suit challenging the listing.

The legal challenges

The Styrene Information and Research Council (SIRC), the major trade association for the styrene industry, and Dart Container Corporation, a manufacturer of styrene, raised several procedural challenges to the listing.

They claimed that NTP's report violated the Administrative Procedure Act (APA) because it was issued "without observance of procedure required by law." The court considered the argument that NTP violated its own procedures concerning the timing of peer review and public comment periods but ultimately rejected the claim. The opinion noted that the industry "plaintiffs may question the wisdom" of NTP's approach, but did not show that NTP failed to observe a procedure required by law.

The suit also argued that HHS's listing of styrene violated the APA's arbitrary and capricious standard. The standard is highly deferential to agency action but does require that the agency "examine the relevant data and articulate a satisfactory explanation for its action including a rational connection between the facts found and the choice made." The court concluded that HHS provided sufficient justification for the decision to list styrene in the report's substance profile. Moreover, the administrative record adequately supported the agency's explanation.