Levels of heavy metals in outdoor and indoor dusts in Muscat, Oman

The concentrations of lead, copper, nickel, zinc and chromium in outdoor and indoor dusts collected from different sites in Muscat, Oman, were determined by flame atomic absorption. Results showed a wide range of concentrations, the means in the outdoor dust being, 65 ± 50, 124 ± 316, 47 ± 45, 930 ± 666 and 64 ± 26 mg kg^-1 for lead, zinc, copper, nickel and chromium, respectively. The 2001 Omani phasing out of leaded fuel resulted in low levels of lead in outdoor dust compared to those reported in the literature. Outstanding was the high nickel concentration in outdoor dust when compared to that in the literature, the reason being natural soil pollution due to the local geology of the northern parts of Oman. The concentrations of chromium, copper and zinc are lower than or comparable to these in other cities around the world. The results also showed that the industrial activities in Muscat do not contribute significantly to metal pollution in street dusts. On the other hand, the mean concentrations of lead, zinc, copper, nickel and chromium in indoor dust were 108 ± 65, 753 ± 1162, 108 ± 91, 130 ± 125 and 34 ± 14 mg kg ^-1, respectively. In general, zinc and nickel levels are higher than those reported in the literature while lead, copper and chromium levels are lower or comparable. When outdoor and indoor dusts were correlated, the ratios between indoor-outdoor mean concentrations revealed that lead, zinc, and copper were generated internally, while nickel and chromium were from external sources.