Description of the Evidence
Approximately 10% of all lung cancer deaths and 30% of lung cancer deaths in lifetime nonsmokers are estimated to be attributable to indoor exposure to radon, estimations that are supported by meta-analysis and pooled-analyses of case-control studies of lung cancer and indoor radon exposure.[27,28] Due to a synergistic interaction between cigarette smoking and radon exposure, the radon-associated risk of lung cancer among smokers is considerably greater than for nonsmokers. The prevention strategy for residents of homes with high radon concentrations is to have the basement sealed to prevent radon gas from leaking into the home.
Early evidence from case-control and cohort studies did not support an association between air pollution and lung cancer; however, the evidence now points to a genuine association. In particular, two prospective cohort studies provide evidence to suggest that air pollution is weakly associated with the risk of lung cancer. In an extended follow-up of a study of six U.S. cities, the adjusted relative risk (RR) of lung cancer mortality for each 10 �g/m3 increase in concentration of fine-particulate was 1.27 (95% CI, 0.96-1.69). Using data from the American Cancer Society's Cancer Prevention Study II, it was observed that compared with the least polluted areas, residence in areas with high sulfate concentrations was associated with an increased risk of lung cancer (adjusted RR = 1.4; 95% CI, 1.1-1.7) after adjustment for occupational exposures and the factors mentioned above. In a subsequent update to this report, the risk of lung cancer was observed to increase 14% for each 10 ?g/m3 increase in concentration of fine particles.
Factors of uncertain association with risk
The results of many case-control and prospective cohort studies show that individuals with high dietary intake of fruits or vegetables have a lower risk of lung cancer than those with low fruit or vegetable intake. In a systematic review of the evidence, the World Cancer Research Fund rates the evidence as "limited suggestive" that nonstarchy vegetable consumption decreases lung cancer risk and "convincing" that fruit consumption and foods containing carotenoids decrease lung cancer risk. However, a subsequent systematic review and meta-analysis limited to prospective studies that adjusted for cigarette smoking found the evidence for carotenoids to be equivocal.
While the focus has been on fruit and vegetable consumption and micronutrients, a wide range of dietary and anthropometric factors have been investigated. Anthropometric measures have been studied, indicating a tendency for leaner persons to have increased lung cancer risk relative to those with greater body mass index.[36,37] The results of a meta-analysis showed that alcohol drinking in the highest consumption categories was associated with an increased risk of lung cancer.