Genetic effects of air pollutants: insights from human biomonitoring studies.

In this issue Sree Devi and coworkers1 report the results of a cytogenetic investigation on traffic policemen from an Indian metropolitan area. The study shows a distinct excess of cytogenetic damage in peripheral blood lymphocytes of policemen compared to indoor workers, highlighting the genotoxic consequences of the exposure to urban air pollutants. Genetic damage, for the severity and irreversibility of the effects at somatic and germ cell level, deserves the highest consideration, and may give an important contribution to the global burden of air pollution. Current estimates of the health impact of air pollution have largely been based on non-neoplastic outcomes, such as mortality for respiratory and cardiovascular diseases2, even though outdoor air pollution is considered a significant risk factor for lung cancer in non smokers. At present, the available evidence suggests that trafficrelated pollution may be associated with childhood cancer and lung cancer in adults, with an estimated contribution of ~ 60,000 lung cancer deaths per year worldwide3. Despite the increasing evidence for a role of air pollution in human lung cancer, especially in developing countries, there are still uncertainties on the underlying mechanism. Fine particles could initiate or promote the development of tumours with indirect mechanism(s), e.g. linked to the inflammatory activity of particulate matter4, or through the direct genotoxic and promoting activity of their organic components5. Extractable organic matter of ambient air in fact is known to be carcinogenic in rodents since decades, with hundreds of genotoxic components identified6.