Risk assessment of lung cancer related to environmental PAH pollution sources.

We assessed the lung cancer risk in six localities with aluminium smelting activities and five with other polycyclic aromatic hydrocarbon (PAH) pollution sources, using two quantitative risk assessment (QRA) approaches for PAH mixtures and compared their risk predictions against actual cancer incidence. In the first approach, carcinogen exposure was estimated from animal-derived BaP toxic equivalents (BaPeq) of individual PAHs. The upper bound lifetime risk estimates ranged between 0.012-4.7 x 10(-5) and 0.019-0.94 x 10(-5) in the aluminium and other localities, respectively. The second approach assumed that the potency of PAH mixtures was linked to their BaP content and lifetime lung cancer unit risk gradients were estimated from epidemiological studies based on BaP exposure measurements. Lifetime risks ranged between 0.02-89 x 10(-5) and 0.06-6.8 x 10(-5) in the aluminium and other localities, respectively. Predicted risks were generally higher in smelter towns, and higher when based on epidemiological studies than on BaPeq. In smelting communities, there was a linear relationship (R2 approximately 0.8) between female lung cancer rates and PAH exposure estimates. To conclude, animal/BaPeq-based QRAs predicted lower risks than occupational/BaP-based QRAs. Epidemiological validation of the QRA could be performed for elevated past exposure to PAHs, but not for currently lower concentrations.