WASHINGTON, May 15 (Reuters) - The latest U.S. government report on what causes cancer, issued on Monday, removed saccharin from the list of suspected carcinogens, but added 14 substances, including second-hand tobacco smoke, as known causes.

It also added alcoholic beverages as known causes of human cancer, along with sunshine and sunlamps, silica dust and the breast-cancer drug tamoxifen -- although the report noted that while cancer drugs may increase the incidence of other cancers, the benefits often outweigh the risks. The National Institute for Environmental Health Sciences (NIEHS), which issued the bi-annual report, said it removed saccharin as a potential cancer-causing agent because tests that showed it caused tumours in rats did not apply to humans. It had been listed since 1981. ``Two decades ago, when saccharin was shown to produce bladder tumours in rats, it was a prudent, protective step to consider the sweetener to be a likely human carcinogen,'' NIEHS director Dr. Kenneth Olden said in a statement. ``However, our understanding of the science has advanced and allows us to make finer distinctions today. Studies now indicate that the rat bladder tumours arise from mechanisms that are not relevant to the human situation.'' He also said humans had used saccharin for decades without increasing rates of cancer. The NIEHS also removed ethyl acrylate, a substance used in making latex paints and textiles, from the list. Both were removed at the request of industry groups. The report listed 218 substances known or suspected to cause cancer in people. The NIEHS said 14 had either been upgraded to the ``known'' category or added to the list. Second-hand smoke topped the upgraded list. ``Environmental tobacco smoke, generated from sidestream and exhaled mainstream smoke of cigarettes, pipes, and cigars is listed as a 'known human carcinogen,''' said the report, published on the Internet at http://ehis.niehs.nih.gov/roc/toc9.html. It cited reports that showed second-hand smoke can cause lung cancer, as well as studies showing that nonsmoking wives and co-workers of smokers have higher rates of lung cancer. Tobacco smoke was also listed as a known cause. ``Separate chemicals identified in tobacco smoke were already listed as carcinogens in the report,'' it said. The new listing came after 1996 revisions in the review process. Smokeless tobacco, including chewing tobacco and snuff, were listed, as well as consumption of alcohol, too much sun and the use of tanning beds or sun lamps. Alcohol is associated with cancers of the mouth, pharynx, larynx, and oesophagus, and there may be a link with liver and breast cancer. Chewing tobacco and snuff can cause cancer wherever they contact the mouth or nose. Other substances listed included: -- Crystalline silica dust small enough to breathe, a byproduct of mining -- Strong inorganic acid mists containing sulphuric acid, produced in the manufacture of alcohol, lead batteries, phosphate fertilisers, soap and detergents, synthetic ethanol, and in pickling and other acid treatments of metals -- Dyes metabolised to benzidine -- 1,3-Butadiene, used to make synthetic rubber -- Cadmium, used in batteries, coating and plating, plastic and synthetic products and alloy -- Ethylene oxide, used to make other chemicals and to sterilise medical devices -- Tamoxifen ``There has been concern expressed that the listing of tamoxifen ... could raise concerns among patients regarding its use for cancer treatment or prevention,'' the report said. It pointed out that benefits can outweigh the risks. Tamoxifen, made under the name Nolvadex by AstraZeneca (quote from Yahoo! UK & Ireland: AZN.L), can increase the risk of ovarian cancer. But ovarian cancer is so rare that doctors say the higher risk is small. Tamoxifen is the first drug to be shown to prevent breast cancer in some women at high risk. Substances added to the ``reasonably anticipated to be human carcinogens'' list include diesel exhaust particulates, isoprene -- one of the components of rubber which is also naturally emitted by plants -- chloroprene, phenolphthalein -- used in some laxatives -- tetrafluoroethylene and trichloroethylene.

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