Heavy Metals Contamination in Roadside Dust along Major Roads and Correlation with Urbanization Activities in Cairo, Egypt

Abstract: Heavy metal concentrations in roadside dusts are increasingly becoming of health concern. Street dust samples were collected from 46 sites representing different activities across the big city and analysed for Pb, Zn, Cd, Ni, Co, Cr, As, Ag and V. Size fraction of <125 µm, represented the greatest contribution of dust in residential, traffic roads and industrial areas, while coarse particles fraction (>200 µm) was the greatest portion of dust in rural sites. Metal concentrations indicated that roadside dust contained elevated levels of heavy metals and varied across Cairo districts. Concentrations of metals in fine fraction of <125 µm were greater than those in coarse fraction. Compared with residential and rural areas, metals concentrations in the dust were higher in traffic roads and industrial areas. Zinc and lead were the most available metals in both dust fractions from all areas. The correlation and ANOVA analysis confirmed the contribution of anthropogenic sources, traffic and industrial emissions, to metal levels in road dust in Cairo. Furthermore, size fraction and dominant urban activity are the main factors controlling metals concentrations in road dust. The contamination levels of the heavy metals in the road dust were evaluated on the basis of contamination factor (Cf), the degree of contamination (Cd), index of geo-accumulation (Igeo), ecological risk factor (Er) and the potential ecological risk index (RI). The contamination factors (Cf) revealed that road dust is highly contaminated by Pb, Zn, Cd, As and V than that contaminated by Ni, Cr, Co and Ag. These results are confirmed by the very high degree of contamination, particularly at traffic roads and industrial areas.