n e w s of t h e w e e k
IDENTIFYING CARCINOGENS Saccharin, ethyl acrylate offthe governments list of cancer hazards, but tamoxifen is on
T
he federal government last week removed two chemicals found in consumer goods from its list of human carcinogens, striking saccharin and ethyl acrylate. In its ninth "Report on Carcinogens," the government did not reclassify the most potent form of dioxin as a known human carcinogen, as it had planned, due to a pending lawsuit. But it did rank tamoxifen, a drug used to combat breast cancer, as a known carcinogen because it can trigger uterine cancer. Overall, the report adds 11 items to its list of known carcinogens, including 1,3butadiene, ethylene oxide, and cadmium compounds. The Department of Health & Human Services, through the National Toxicology Program (NTP), prepares the carcinogen report every two years, as required by Congress. The report identifies substances, mixtures, and exposures that fit into one of two categories: known human carcinogens and reasonably anticipated to be a human carcinogen. The first report was released in 1980. The delisting of saccharin, an artificial sweetener, and ethyl acrylate, a chemical used in making paint and industrial coatings, is noteworthy, George W. Lucier, associate director of NTP, tells C&EN. This marks the first time chemicals have been taken off the list following a formal scientific review. Several substances were removed in the 1980s but only because human exposure to them in the U.S. had ceased, he explains. Saccharin had been ranked as "reasonably anticipated" to be a carcinogen since 1981, after tests indicated saccharin caused bladder cancer in rats. But research since then has shown that rats— male rats in particular—have a unique physiology that contributes to formation of bladder cancer, the report says. "The factors thought to contribute to tumor induction by sodium saccharin in rats 8
MAY 22, 2000 C&EN
Government's latest list of carcinogen ins, outs Removed: Ethyl acrylate3 Saccharin3 Added as or upgraded to "known human carcinogen": 1,3-Butadiene Cadmium and its compounds3 Chewing or smoking tobacco products Consumption of alcoholic beverages Crystalline silica of respirable size Dyes metabolized to benzidine Ethylene oxide3 Secondhand tobacco smoke Strong inorganic acid mists containing sulfuric acid Tamoxifen UV radiation, all types Added as "reasonably anticipated to be a human carcinogen": Chloroprene Diesel exhaust particles Isoprene Phenolphthalein Tetrafluoroethylene Trichloroethylene a Formerly listed as "reasonably anticipated to be a human carcinogen."
would not be expected to occur in humans," the report says. Also delisted was ethyl acrylate, used as an intermediate in production of emulsion-based polymers found in paint formulations, industrial coatings, and latex products. It was classified as "reasonably anticipated" to be a carcinogen in 1989 based on tests showing that mice developed stomach tumors when force-fed ethyl acrylate. More recent research suggests that tumors developed because the gavage-administered chemical irritated the animals' stomachs. Animals in tests using exposures other than administration by a tube to the stomach showed no increased cancer rates. The Basic Acrylic Monomer Manufacturers, a Washington, D.C., industry
group, had asked NTP to remove ethyl acrylate from its list. In addition, the gasoline additive methyl tert-buty\ ether (MTBE) was considered for inclusion in the report but was not added. NTFs review of scientific evidence on the substance concluded that the results of tests on rodents were not sufficient to list MTBE as reasonably anticipated to be a human carcinogen. The report did not upgrade 2,3,7,8-tetrachlorodibenzo-^-dioxin (TCDD), a by-product of combustion and some industrial processes, from a "reasonably anticipated" to a "known" carcinogen, because of a lawsuit. An industry consultant, two restaurants, a restaurant association, and a medical device maker that uses polyvinyl chloride are suing NTP in an effort to prevent such a listing. They argue that, in proposing the upgrade, NTP disregarded its own standard that only substances with "sufficient evidence from studies in humans" be classified as known human carcinogens. A federal judge in Washington, D.C., is expected to decide this summer whether to allow NTP to list TCDD as a known carcinogen. If the court rules in favor of NTP, the agency will issue an addendum to the report In a related development, the Environmental Protection Agency apparently is set to classify TCDD as a human carcinogen, according to the Washington Post, which last week received a leaked copy of a draft EPA report on the health and environmental effects of dioxins. The draft, which has not been reviewed by the agency's advisory board, reportedly also links exposure to low amounts of TCDD to hormonal changes and developmental effects. Cheryl Hogue
Epoxidation Catalyst Immobilized In Ionic Liquid Chemists in South Korea have employed a room-temperature ionic liquid to immobilize, recover, and recycle a homogeneous chiral catalyst that is used for the asymmetric epoxidation of alkenes. Principal research scientist Choong Eui Song and research scientist Eun Joo Roh at the Korea Institute of Science & Technology, Seoul, immobilized a cata-
