Health Risk Assessment of Metals in Street Dust of Karaj City in 2018

In the last two decades, air pollution has become a serious problem, leading to a variety of harmful health effects. Street dust is a complex combination of pollutants from different sources, which can be a good indicator of air quality in the urban environment. So, this study was conducted to assess the health risk of toxic metals associated with street dust and identify their emission sources.

Dust samples were collected from three high-traffic districts in Karaj. After acid digestion, Cu, Zn, Cr, Mn, Ni, Ca, Ba, Sr, Li, Ti, Na, Mg, K, Fe, Al and V were measured using ICP-OES and Cd, Co, W and Pb were measured using ICP-MS.

The results of the measurement of elements in the street dust of Karaj indicated that compared to the amounts of elements in the earth's crust, the concentration (mg/kg) of Cd (X =0.9), Zn (X =479.15), Cu (X =159.37) and Pb (X =113.57) were at a very high level and the concentration (mg/kg) of Ni (X =69.36), Cr (X =93.96), Co (X =21.06), W (X =5.73) and Ca (X =75900) were at a relatively high level. In contrast, the concentrations of other elements (Ba, Mn, V, Sr, Ti, Li, Mg, Na, Ka, Fe, and Al) were in the range of values found in the earth's crust. Cluster analysis showed that Cd, Pb, Zn, Cu, Ni, Cr, Co, and Ca were mainly caused by anthropogenic activities, while other studied metals were associated with natural sources. Ingestion of dust particles was the main exposure pathway of toxic metals for both adults and children in Karaj. The Hazard Index (HI) in the children was higher than the adults, but it was lower than the safe level (HI≤1) in the both groups. Co, Cr and Cd had the highest carcinogenic risk among the studied metals.

The results of this study indicated that the street dust of Karaj is highly contaminated with toxic metals that long-term exposure with them can cause harmful effects, especially in children. Therefore, continuous monitoring of metal pollutants especially Co, Cr and Cd is recommended.