Following three scientific reviews, the National Toxicology Program has asked for final public comment before recommending action on proposals to list benzidine dyes, UV radiation from sunlamps and the sun, cadmium, the drug tamoxifen, butadiene, sulfuric acid mists and tobacco whether smoked or chewed, as "known human carcinogens" in the federal government's Report on Carcinogens.

"Final" comment on a proposal to remove saccharin from the Report on Carcinogens was also sought. In an associated Federal Register notice, the NTP said it is also re-reviewing dioxin for procedural reasons.

NTP said in one notice it is "especially interested in obtaining additional relevant scientific information in support of or against the petition to delist saccharin" because the three reviews split in their recommendations. Two scientific reviews favored removing saccharin from the Report but an October 30-31 advisory panel -- the NTP Board of Scientific Counselors Subcommittee for the Report on Carcinogens-recommended by a narrow margin that the sweetener continue to be listed as an "anticipated" carcinogen.

The NTP, which is headquartered at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., particularly asked information on:

• The adequacy of existing epidemiology data, particularly as it relates to reported increased incidences of bladder tumor formation in certain subpopulations.
• The mechanism of urinary bladder tumor formation in male rats as it relates to other test species and to humans.

Final comment was also requested for additional substances to be listed as "reasonably anticipated to be a human carcinogen":

• Chloroprene, a component of adhesives in food packaging; phenolphthalein, a cathartic recently removed from popular nonprescription laxatives following NIEHS studies; tetrafluoroethylene, used in the production of Teflon, and trichloroethylene, a solvent.

NTP said that the NTP Board subcommittee's re-review of dioxin need not delay its listing in the ninth Report on Carcinogens, which is planned for next year. Kenneth Olden, Ph.D., director of the NTP and the NIEHS, said he has no argument with the recommendation to upgrade dioxin from "reasonably anticipated" to "known human carcinogen" but wanted to make sure the review crossed every "t" and dotted every "i" in this first set of actions following recent changes in the criteria and procedures for listing agents in the Report.

A press release on the advisory council's review of these substances may be obtained at http://www.niehs.nih.gov (http://www.niehs.nih.gov) under news and publications or by telephoning the contact listed at the beginning of this release. The FR notices are on page 13418 (March 19) and page 18435 (April 15).

Comment should be sent to Dr. C. W. Jameson, NTP Report on Carcinogens, EC-14, P.O. Box 12233, Research Triangle Park, NC 27709, by May 19, 1998, or, in the case of dioxin (TCDD) June 15.