The association of lung cancer with exposure to ETS has yielded relative risks of 2 or less for nonsmokers. As cancer of the lung is the cancer most strongly associated with active smoking, weaker effects would be expected for cancers that are less closely related to smoking. The first emphasis in this chapter is on smoking-related cancers, because these might be more plausibly associated with exposure to ETS. However, exposure to ETS occurs at earlier ages than active smoking; thus, there may be effects of ETS exposure on risk for other cancers.
Active tobacco smoking is an important cause not only of lung cancer, but also of bladder cancer, cancers of the pancreas and renal pelvis, and probably of the nasal sinus and kidneys. Oral, oropharyngeal, hypopharyngeal, laryngeal, and oesophageal cancers are also strongly associated with active smoking, especially in conjunction with the use of alcohol. Primary cigar and pipe smokers face a somewhat lower risk for cancer of the lung than cigarette smokers, but their risk for cancer of the larynx, pharynx, oral cavity, and esophagus is similar if not greater than that of cigarette smokers (U.S. Department of Health and Human Services, 1982). Also, lip cancer is associated with tobacco smoking, as well as pancreatic cancer and, perhaps, renal adenocarcinoma. An increased risk of cervical cancer has been observed in tobacco smokers, but