The NTP is headquartered at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., and the board will meet in public meetings there in the conference center, building 101, at 111 Alexander Drive. The recommendations of two scientific reviews will become public at that time.

The board is influential but not the final word. It makes recommendations to NTP Director Kenneth Olden, Ph.D., who in turn makes recommendations to Secretary of Health and Human Services Donna E. Shalala.

The strongest category in the listings is "known" human carcinogen. Saccharin has, since 1981, been in a lesser category as "anticipated" to be a carcinogen (or "likely to be") based on evidence that included testing in animals. The Calorie Control Council, an industry group, petitioned for saccharin to be de-listed under revised criteria and review procedures announced by the Department of Health and Human Services last year. The criteria were broadened to allow consideration of such factors as mechanisms of action as well as the standard two-year rodent tests, and also set up a mechanism for petitioning to have a substance removed. Under a Congressional mandate, the HHS Secretary is required to submit to Congress a Report on Carcinogens. The Secretary has delegated responsibility for preparing the report on the NTP.

In July, in announcing plans for the ninth such report, NTP said that it planned to review saccharin for de-listing and to review 13 substances or categories of substances that have been nominated for review as candidates for listing.

Besides tobacco smoke, smokeless tobacco and UV radiation, the substances planned for review are:

• Benzidine-based dyes -- a class of more than 250 dyes primarily used to dye textiles, leather and paper;

• Chloroprene, used to make industrial rubber products and as a component of adhesives in food packaging;

• Phenolphthalein, an ingredient in some nonprescription laxatives which a study by the National Institute of Environmental Health Sciences already has caused the Food and Drug Administration to review its use as a nonprescription drug;

• Inorganic acid mists containing Sulfuric acid, generated in refining petroleum, in ore concentration and in removing impurities from iron, steel and other metals;

• Tetrafluoroethylene, which is used in making Teflon and was used as a propellant in food and cosmetic aerosols;

• Trichloroethylene, an industrial solvent for vapor degreasing and cold cleaning fabricated metal parts. It has also been used as a carrier in insecticides and fungicides -- and was once commonly used to decaffeinate coffee but has been replaced by a water process;

• Tamoxifen, a drug used in the palliative treatment of breast cancer and in preventing recurrence. (As with many cancer drugs, the labeling already reflects studies indicating the drug may sometimes also cause cancer in animals or humans.)

In addition, several already listed substances would be reviewed as candidates to move from "anticipated" human carcinogens to the stronger category of "known" human carcinogens:

• Butadiene, a chemical used in making synthetic rubber;

• Cadmium and cadmium compounds, used in batteries, alloys, coating and plating, plastic and synthetic products;

• Dioxin, or tetrachlorodibenzo-p-dioxin (TCDD), formed as an impurity or byproduct in herbicide manufacture, as in the Agent Orange sprayed by the U.S. military to defoliate parts of Vietnam, and during incineration and in several industrial processes.

Both Oct. 30 and Oct. 31 sessions begin at 8:30 AM.