Air pollution as a risk factor for lung cancer

Over the past decade, an increasing body of scientific evidence has accrued associating outdoor air pollution with certain types of cancer. Ambient air, particularly in densely populated urban environments, contains a variety of known human carcinogens such as benzo[a]pyrene and benzene, inorganic compounds (e.g., arsenic and chromium), and radionuclides. Now, it is well recognized that urbanization and lung cancer mortality are linked. This association could arise from differences in the distributions of other lung cancer risk factors, such as smoking and occupational exposures, by degree of urbanization, etc. Air pollution has positively been associated with lung cancer mortality and cardiopulmonary disease mortality, but not with mortality from other causes combined. New studies will need to develop and apply improved epidemiologic methods and to compare the effect of exposure to the pollutant mixtures on lung cancer in different cities while effectively controlling confounding factors including cigarette smoking and diet.