Deciphering the origin of Cu, Pb and Zn contamination in school dust and soil of Dhaka, a megacity in Bangladesh.

In recent decades, anthropogenic activities have resulted in road dust and roadside soil hosted metal(oid)s pollution in the urban environment. In the South-Asian megacity "Dhaka", schools are situated in the areas with high population density and high traffic emissions. As the school-going children are the most vulnerable receptor, school premises in Dhaka city represent an important yet overlooked exposure point to contaminated dust and soil. Therefore, the present study investigated the metal(oid)s (Cu, Pb, Zn and As) pollution in dust and soil at school compounds, explored their possible sources and estimated the associated human health risk. This study revealed that dust contained higher concentration of metal(oid)s than soil, and the Azimpur Govt. Girls School & College was identified as the most contaminated site. The enrichment of school dust with Cu, Zn and Pb were strictly related to the dense population and substantial traffic activity in the study areas. Arsenic content in school soil was several folds higher than its concentration in the upper crust. Natural and anthropogenic activities possibly posed a synergistic effect on such high soil As. The multivariate statistics suggested that Cu, Zn and Pb were likely to be originated from traffic-related activities, while Zr, Fe, Ti and Rb from natural sources, and K, Sr and Ca from industrial activities. The assessment of health risk suggested the children as a vulnerable receptor and ingestion was identified as the dominant pathway of dust and soil exposure. The hazard index (HI) values were lower than unity, suggesting no possible non-cancer health risk. Arsenic posed a lifetime carcinogenic risk to the population in the study area through soil ingestion and dermal adsorption.