The carcinogenic risk and variability of particulate-bound polycyclic aromatic hydrocarbons with consideration of meteorological conditions

Epidemiological and laboratory studies suggest that atmospheric particulate matter and polycyclic aromatic hydrocarbons (PAHs) have a strong association with cancer prevalence and risk. Health hazards from PAH inhalation emanate mainly if these compounds are bound to particulate matter, whereas the depth of penetration and retention in the human organism is greatly dependent on the size and morphology of the particle. We determined the distribution of 21 PAHs over different particle size fractions and investigated the influence of meteorological conditions on the partitioning between air and particle phase and the distribution over different size fractions. The highest PAH concentration was found in a size range from 0.35 to 1.2 mu m. About two-thirds of the total PAH concentration were associated to respirable particles smaller than 1.2 mu m, highlighting the importance of considering fine particles in cancer risk assessment. High temperature and sunshine duration were associated with decreased PAH contamination, while humidity was associated with increased PAH contamination. We found that high molecular weight compounds had an increased tendency to be sorbed to smaller particles. Approximately 30% of the overall carcinogenicity of the samples, determined by a dose addition model, was contributed by benzo[a]pyrene. However, the relative contribution of benzo[a]pyrene to the overall carcinogenicity varied greatly over different samples and size fractions, suggesting that benzo[a]pyrene alone is not an adequate indicator compound for assessment of carcinogenicity. Instead, we suggest integrating nine PAHs, which together contributed approximately 93% to the overall carcinogenicity, into a sum parameter serving as an indicator for carcinogenic potential.