PM10 and PM2.5 chemical source profiles with optical attenuation and health risk indicators of paved and unpaved road dust in Bhopal, India.

Size classified (PM10 and PM2.5) paved and unpaved road dust chemical source profiles, optical attenuation and potential health risk from exposure to these sources are reported in this study. A total of 45 samples from 9 paved road and 6 unpaved road sites located in and around Bhopal were re-suspended in the laboratory, collected onto filter substrates and subjected to a variety of chemical analyses. In general, road dust was enriched (compared to upper continental crustal abundance) in anthropogenic pollutants including Sb, Cu, Zn, Co, and Pb. Organic and elemental carbon (OC/EC) in PM10 and PM2.5 size fractions were 50-75% higher in paved road dust compared to their counterparts in unpaved road dust. Further, the results suggest that when it is not possible to include carbon fractions in source profiles, the inclusion of optical attenuation is likely to enhance the source resolution of receptor models. Additionally, profiles obtained in this study were not very similar to the US EPA SPECIATE composite profiles for PM10 and PM2.5, for both sources. Specifically, the mass fractions of Si, Fe, OC, and EC were most different between SPECIATE composite profiles and Bhopal composite profiles. An estimate of health indicators for Bhopal road dust revealed that although Cr was only marginally enriched, its inhalation may pose a health risk. The estimates of potential lifetime incremental cancer risk induced by the inhalation of Cr in paved and unpaved road dust (PM10 and PM2.5) for both adults and children were higher than the baseline values of acceptable risk. These results suggest that road dust Cr induced carcinogenic risk should be further investigated.