Lung cancer accounts for a substantial proportion of cancer incidence and mortality throughout the world. Epidemiologic data suggest that Chinese women have a high incidence of lung cancer in relation to their smoking prevalence. In addition to active tobacco smoke exposure, other sources of fumes and airborne particles in the indoor environment (e.g., cooking, burning of incense and mosquito coils) have been considered potential risk factors for lung cancer. Using a case–control study, Tang et al. (p. 1257) explored effects of inhalants from combustion sources common in the domestic environment on lung cancer and the modification of these effects by active tobacco smoking. They observed a positive relationship with daily exposure to incense or mosquito coils and cooking fumes only among smokers but no association among lifetime nonsmokers. Interactions between smoking and frequency of cooking or exposure to incense or mosquito coils were statistically significant and consistent with synergistic effects on lung cancer. The authors conclude that active tobacco smoking is an important risk factor for development of lung cancer and may also cause smokers to be more susceptible to the risk-enhancing effects of other inhalants.