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Friday, October 31, 1997, 12:00 p.m. EDT
The National Toxicology Program's advisory panel on the federal government's Report on Carcinogens today recommended the continued listing of saccharin in the ninth edition of this official report of cancer-causing substances. Saccharin thus may continue to be listed as an "anticipated" human carcinogen, as it has been since 1981.
It has never been listed in the stronger category of "known" human carcinogen.
Meeting in public sessions at the headquarters of the National Institute of Environmental Health Sciences and the affiliated NTP in Research Triangle Park, N.C., the review panel of the NTP's Board of Scientific Counselors looked at reports from two scientific reviews by the NIEHS Review Committee and the Interagency Committee Working Group for the Report on Carcinogens which were announced to have voted, respectively, 7-3 and 6-2 in favor of ending saccharin's listing.
Today, in the first public review of the proposals, the review subcommittee voted instead to continue listing the sweetener. The vote was 4-3.
The decision largely hinged on two issues: Whether the mechanism by which saccharin produced cancer in rats would operate in people, and Whether the dosages given rats were the extreme equivalent of "ten thousand cans of diet pop" a day, as popularly pictured, or were more comparable to potential human use.
Several panel members said they were surprised to find the doses used in rats were not so extreme as they supposed, particularly when compared to possible consumption by children. And some said that while rats were not people and may handle saccharin differently, they were unwilling to conclude there was no carcinogenic effect in humans.
A consultant from the National Cancer Institute said, "I don't think anyone thinks [saccharin] is a major cause of bladder cancer" but that there are "troubling subgroup" findings in some of the epidemiological studies.
The review panel of the NTP Board of Scientific Counselors makes its recommendation to Kenneth Olden, Ph.D., who is the director of both NIEHS and NTP. He, in turn, will make recommendations to Secretary of Health and Human Services Donna E. Shalala.
Saccharin has never been listed as a "known" human carcinogen but, since 1981, has been in a lesser category as "anticipated" to be a carcinogen (or "likely to be") based on evidence that included testing in animals. The review aimed at removing saccharin, which was sought by the Calorie Control Council, an industry group, was carried out 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.
A Canadian study in rats led the Food and Drug Administration to take steps to partially ban the popular sweetener in 1977, but Congress stepped in to permit saccharin's continued sale as long as it is labeled, "Use of this product may be hazardous to your health. This product contains saccharin which has been determined to cause cancer in laboratory animals."
The scientific advisory group also today recommended listing 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD) and BENZIDINE DYES as known human carcinogens.
Dioxin is formed as an impurity or by-product in herbicide manufacture, during incineration and in several industrial processes. Potential exposures today are from municipal incinerators, dump sites and contaminated soil. Agreed to narrowly, dioxin's recommended new designation would upgrade it from its current status as an "anticipated" human carcinogen to a "known" human carcinogen.
Benzidine dyes, of which there are more than 250, are used for dyeing textiles, paper and leather.
The panel voted to list TRICHLOROETHYLENE, used as an industrial solvent for degreasing and cold cleaning fabricated metal parts, as reasonably anticipated to be a human carcinogen. The solvent was once widely used to decaffeinate coffee.
Yesterday, the advisory group unanimously recommended that ultraviolet radiation, whether from sunlight or an artificial source such as tanning booths and tanning beds, be listed as "known to be a human carcinogen."
The draft document said, "Human studies have shown that exposure to solar radiation is causally related to skin cancer, and that use of sunlamps or sunbeds is associated with skin and eye cancer."
The recommended designation makes clear that sunlamps, tanning booths and other artificial sources of UV light are also hazardous, regardless of the claims of operators. Up to 10 percent of Americans-mostly young women-were estimated during the discussion to have used artificial tanning devices.
Operating under new rules that permit mixes, as well as single chemicals, to be listed in the Report on Carcinogens, the panel took this first opportunity, under the revised rules, to recommend that smokeless tobacco such as snuff and chewing tobacco, and inhaled tobacco smoke be officially listed as "known" to cause cancer in humans. Studies have linked smokeless tobacco to cancer of the mouth and lip, and to an increased risk of prostate cancer.
Chemicals in tobacco smoke and in tobacco are already listed in the report but the new listing would make clear that tobacco products as a whole, whether chewed or smoked as cigarettes, pipe tobacco and cigars, cause cancer in humans.
No one from industry asked to speak against the designation.
The advisors also recommended that:
Tetrafluoroethylene, a chemical used in producing Teflon and other polymers, as well as having been used as a propellant for food product aerosols, be listed as "reasonably anticipated to be a human carcinogen."
Cadmium and Cadmium Compounds, used in batteries, coating and plating, plastic and synthetic products and in alloys, be upgraded from "reasonably anticipated" to "known to be a human carcinogen."
Cholorprene, used as a monomer for neoprene elastomers, industrial rubber products, and as a component of adhesives in food packaging, be listed as reasonably anticipated to be a human carcinogen.
1,3-Butadiene, used in making synthetic rubber, be upgraded to be "known to be a human carcinogen."
Strong inorganic acid mists containing sulfuric acid, used to make fertilizers, rayon and other fibers, pigments and colors, explosives, plastics, coal-tar products such as dyes and drugs, storage batteries, detergents, rubber, pulp and paper, cellophane and catalysts. It is also used in refining petroleum, in ore concentration and in removing impurities from iron, steel and other metals to be listed as a known human carcinogen
Tamoxifen, a drug used to reduce the risk of a return of breast cancer, be listed as a known human carcinogen, but with a strong emphasis in the report that its benefits greatly outweigh the risks. (As with many cancer drugs, the labeling already reports animal studies indicating the drug may sometimes cause cancer in animals or humans.)
Phenolphthalein, an ingredient in some nonprescription laxatives, as an "anticipated human carcinogen." The research by the National Institute of Environmental Health Sciences on which this recommendation is based recently caused the Food and Drug Administration to question its safety as a nonprescription drug. Drug manufacturers have now abandoned its use.
Saccharin, which provides a sweet taste without the calories of sugar, became the first artificial sweetener after it was discovered by two chemists in 1879. One of them, Constantin Fahlberg, discovered the sweet taste by accident. According to the Britannica, he noticed an unexpected sweet taste to food he subsequently ate, and found this sweetness on his hands and arms, though he had washed them thoroughly. By taste tests back in his laboratory he found the source of the sweetness was saccharin. (It is 200 to 500 times as sweet as cane sugar.)
Saccharin became widely used by diabetics and was used in drugs in which sugar might lead to spoilage. In the toxicological studies that led to FDA's proposed ban, saccharin fed to rats at levels of 5 to 7.5 percent of their diet had a greater incidence of bladder cancer. Later, studies of human saccharin users showed no link to human bladder cancer. Most countries continued to permit its use-often with a label mentioning the animal studies.
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