Chemical biomarkers of exposure and early damage from potentially carcinogenic airborne pollutants
Epidemiology and laboratory studies support the conclusion that air pollution is carcinogenic to humans. Chemically specific biomarkers are useful for determining human exposure to, and metabolism of, potentially toxic and carcinogenic components of air pollution, and distinguishing exposures due to air pollution from those resulting from tobacco smoke. Representative chemically specific biomarkers, quantified by mass spectrometry and related techniques, are discussed. The biomarkers are related to exposure to polycyclic aromatic hydrocarbons, volatile toxicants and carcinogens, oxidants, DNA damaging compounds, and metals found in polluted air. Quantifiable chemically specific biomarkers potentially useful in studies of air pollution carcinogenesis include urinary 1-hydroxypyrene, metabolites of benzo[a]pyrene, phenanthrene, benzene, 1,3-butadiene, acrolein, and crotonaldehyde, as well as products of oxidative damage such as urinary 8-hydroxy-2'-deoxyguanosine, malondialdehyde, and F2-isoprostanes, certain DNA adducts, and metals. Tobacco-specific metabolites such as cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol can be used to distinguish tobacco-related exposures from those resulting from air pollution. The following validated chemically specific biomarkers are currently the optimal ones for use in studies of air pollution and cancer: urinary 1-hydroxypyrene, phenanthrene metabolites, S-phenyl mercapturic acid, urinary or blood Cd, 8-hydroxydeoxyguanosine and F2-isoprostanes such as 8-iso-PGF2α. This suite of biomarkers will reliably establish exposure to carcinogenic polycyclic aromatic hydrocarbons, benzene and Cd, and will also provide critical information on oxidative damage and inflammation, both of which are important in carcinogenesis.