^®: CRE Regulatory Action of the Week

NTP UNVEILS NEW RATIONALE IN SUPPORT OF "KNOWN HUMAN CARCINOGEN" LISTING FOR DIOXIN

In a move sure to raise eyebrows among toxicologists, the National Institute of Environmental Health Sciences amended the Ninth Report on Carcinogens on January 19, 2001, to list dioxin as a "known human carcinogen" based on an interpretation of the agency’s listing criteria that was never presented to reviewing scientists. While the criteria require a finding of "sufficient evidence from studies in humans", the final listing states that the listing is based on "a combination of epidemiological and mechanistic information". The agency had conceded some time ago that the epidemiological data alone were not "sufficient" to support the listing.

The final listing represents a formal and public departure from the listing rationale presented to reviewing scientists during the 9^th RoC listing reviews in 1998-99. The Draft Background Document, upon which the proposed dioxin listing was reviewed, cited animal studies as a basis for the listing, and when pressed on this point the agency thereafter contended that it was entitled to rely on "all relevant information" under the terms of the listing criteria, which were revised in 1996.

CRE Advisory Board Member Jim Tozzi and several other plaintiffs challenged that position in a federal lawsuit in 1999. Click here to read about Tozzi suit, including copies of key briefs. The agency’s newly released rationale was first disclosed to plaintiffs on the morning of oral argument in May, 2000, but was then placed under seal at the agency’s request.

A District Court judge deferred to the agency’s interpretation of the criteria on September 30, 2000, and the Tozzi plaintiffs are appealing that decision. NTP’s new listing follows a ruling by the D.C. Circuit in December denying the plaintiffs’ request for an injunction of the amended publication pending appeal. The parties are awaiting an order from the Appeals Court scheduling further briefing in the case