The RoC indicates this listing is based on the observed causal relationship between passive exposure to tobacco smoke and human lung cancer. The listing states that there are conclusive published studies that indicate increased risk of lung cancer in nonsmoking women living with smoking husbands or working with smoking co-workers. Cigarette smoking has been known to cause cancer in humans for many years, and is now considered to be the leading preventable cause of cancer in developed countries. Separate chemicals identified in tobacco smoke were already listed as carcinogens in the RoC . The new listing of tobacco smoking is the result of the 1996 revision in the review process that allows for the review and listing of exposure circumstances in the RoC .
Studies indicate that the tumors often arise at the site of placement of the tobacco.
The RoC states that consumption of alcoholic beverages is causally related to cancers of the mouth, pharynx, larynx, and esophagus, and goes on to say that studies indicate that the risk is most pronounced among smokers and at the highest levels of consumption. The RoC reports that the effect of a given level of alcoholic beverage intake on cancers of the head and neck is influenced by other factors, especially smoking, but that smoking does not explain the increased cancer hazard associated with alcoholic beverage consumption. The RoC also states that there is evidence that suggests a link between alcoholic beverage consumption and cancer of the liver and breast. The RoC cites data that indicate a causal relationship between exposure to solar radiation and melanoma and other skin cancers in humans, and that exposure to sunlamps or sunbeds is associated with melanoma. The RoC also indicates that skin cancers are observed with increasing duration of exposure, and the effects are especially pronounced in individuals under 30 and for those who experience sunburn.