DIFFERENTIAL-EFFECTS OF TAR CONTENT, TYPE OF TOBACCO AND USE OF A FILTER ON LUNG-CANCER RISK IN MALE CIGARETTE SMOKERS

Background. To date, the effect of tar exposure, the use of a filter and the type of tobacco (light or dark) on the risk of lung cancer have not been studied together. Methods. Data from a case-control study on lung cancer were used to evaluate the specific effects of these three parameters. Cases of lung cancer and controls were interviewed in hospitals in France from 1976 to 1980. The past tar content of cigarettes distributed by the French Tobacco Monopoly was obtained. The results presented concern an exclusively male population of lifelong smokers of French cigarettes and lifelong smokers of light imported cigarettes. The population comprised 1114 cases of histologically confirmed lung cancer and 1466 hospitalized controls. Results. An increase in risk was found among smokers of both dark and light cigarettes (relative risk[RR] = 2.6, 95% confidence interval [CI]:1.1-6.5) and among lifelong smokers of dark cigarettes (RR = 1.7, 95% CI: 0.9-3.2) compared to lifelong smokers of light cigarettes. Similarly, the risk of lung cancer was higher among smokers of both non-filter and filter cigarettes (RR = 1.6, 95% CI: 0.9-2.7) and among lifelong smokers of non-filter cigarettes (RR = 1.6, 95% CI: 0.9-2.8) than among lifelong smokers of filter cigarettes. A borderline significant increase in risk was observed for smokers of French cigarettes compared to smokers of light imported cigarettes (RR = 2.6, 95% CI: 0.9-7.7). No significant difference in the risk of lung cancer was observed among smokers of French cigarettes according to the proportion of years of smoking high tar cigarettes. Conclusion. This study tends to demonstrate a separate effect of type of tobacco, use of a filter and tar content in addition to the usual characteristics of cigarette smoking on lung cancer risk.