Polycyclic aromatic hydrocarbons (PAHs) in street dust of Rio de Janeiro and Niterói, Brazil: Particle size distribution, sources and cancer risk assessment.

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 to 10, 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 to 10, so this exposure pathway was almost 10 less severe than through ingestion and dermal contact, and thus negligible.