Fifteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in two fractions (<63μm and 63-850μm) of street dust samples collected in different urban areas of Rio de Janeiro and Niterói cities, Brazil. Individual PAH concentrations and total PAH concentrations (∑PAH) were evaluated considering geographic and particle size distributions, PAH source and cancer risk. In 53% of the samples, ∑PAH values were higher in the smallest particles than in the largest ones, whereas the inverse was true for 23.5% of the samples. In 23.5% of the samples, both classes of particles showed comparable ∑PAH. The highest ∑PAH concentrations were found in areas of limited air dispersion, resulting in PAH accumulation in street dust. The diagnostic ratios and principal component analysis (PCA) indicated a strong influence of pyrogenic sources on PAH concentration, mainly of vehicular emissions. The cancer risk levels for children and adults, for both particulate size fractions (<63μm and 63μm-850μm), were comparable for dermal contact and by ingestion, and ranged from 10-8 to 10-6, whereas in certain cases the cancer risk level for adults by dermal contact was 2 to 3 times larger than for children. The cancer risk levels via inhalation always ranged from 10-13 to 10-10, so this exposure pathway was almost 104 less severe than through ingestion and dermal contact, and thus negligible.
Keywords: Cancer risk assessment; PAH; Particle-size distribution; Source evaluation; Street dust.
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