Street dust in the largest urban agglomeration: pollution characteristics, source apportionment and health risk assessment of potentially toxic trace elements

The study assessed the composition, health risk, and sources of trace elements of road dust collected from three major metropolitan cities in Bangladesh. Pellets were prepared from the collected road dust samples and analyzed by the Energy Dispersive X-ray Fluorescence. The mean concentration of trace elements showed the order of K > Fe > Ca > Ti > Mn > Zr > Sr > Zn > Rb > Cr > Rb > Cu > Pb > Y > As > Ni. This research also presented the spatial distribution of the metals among three cities. The contamination factor and degree of contamination were assessed. The highest contamination factor was observed near BSRM steel manufacturing company, Chattogram could be due to the increased traffic in front of this industry. All the sampling sites showed pollution load index lower than one indicating unpolluted. However, K, Zn, and Zr showed a pollution load index values more significant than one. The result indicated that the ecological risk factor (Er) values fluctuated among metals tested across metropolitan cities. Negative geo-accumulation indexes were found for all the elements except K and Zn, suggesting moderate pollution. The Hazard Quotient values of all metals are < 1 for both adults and children. The cancer risks associated with Cr, Co, Ni, As, and Pb have been estimated individually for children and adults. The cancer risks associated with trace elements are below the European Union's acceptable limit, indicating that these five elements are not carcinogenic. The findings of principal component analysis followed by multiple linear regression showed that the sources of heavy metals were mixed natural (34.25%) and anthropogenic sources, vehicle emissions (38.92%), natural sources (5.80%), industrial sources (11.02%) and agricultural sources (10.02%). Four factors were concluded as sources of heavy metals confirmed by applying the positive matrix factorization model such as anthropogenic, industrial activities, natural process and agricultural activities.