Refining Assessment of PAH Exposure and Potential Carcinogenic Risk Assessment from Biomass Burning Incorporating Internal Dosimetry Metrics

摘要

The current study deals with the assessment of the cancer risk attributable to exposure to PAHs associated to an increased use of biomass for space heating in Greece in the winter of 2012-2013. The study incorporated ambient air PM sampling in several sites in the city of Thessaloniki, as well as chemical analysis of PAHs and levoglucosan, used here as the most specific tracer of biomass combustion. Internal exposure to PAHs was estimated taking into account the deposition of the respective PM fractions across the human respiratory tract (HRT) and the respective PAHs concentration of the respective PM fractions. Deposition at different regions of the HRT was estimated using the Multiple-Path Particle Dosimetry (MPPD) model. Potential cancer risk due to exposure to the mixture of urban ambient air PAHs was calculated using the toxicity equivalence factor (TEF) approach using as basis the benzo(a)pyrene (B[a]P) cancer potency. The BaP-TEQ (Toxicity Equivalent Quotient) (carcinogenic equivalent expressed in ng/m3) was calculated by multiplying the concentrations of each compound in the PAH mixture with the respective TEF for cancer potency relative to BaP. Cancer risk was estimated by multiplying the TEQ of the respective fraction of particulate matter deposited daily across HRT by a slope-factor equal to 0.25 10-6 ng/kg_bw/day) function, initially derived by the B[a]P Inhalation Unit Risk (equal to 0.88 10-6 (ng/m3)-1). Significant variation in internal exposure to PAHs (and respectively to the estimated risk) was observed among different age groups, much larger than variation due to geospatial attributes. Bodyweight normalized uptake (and the attributed risk) for children is four times higher than for adults. Only limited difference was found between traffic and urban background sites in the winter; the latter indicates that biomass emitted PM are not significantly different in terms of carcinogenic potency compared to traffic ones.