Comparison of heavy metals in urban soil and dust in cities of China: characteristics and health risks

To determine the similarities and differences in heavy metal characteristics in urban soil and dust, we collected heavy metal data for soil and dust samples from 34 cities in China reported in peer-reviewed articles. The results showed that the mean Cd, Pb, Cu, and Zn concentrations in urban street dust were generally higher than those in urban soil. The mean I-geo values of heavy metals in urban soil followed the order of: Cd (1.07) > Zn (0.31) > Pb (0.25) > Cu (0.05), while that in urban dust was: Cd (2.50) > Zn (1.39) > Pb (1.17) > Cu (0.98). The development of metal processing and smelting industries, manufacturing, and the relocation of heavily polluting enterprises were the main reasons for the high metal concentrations in some cities. The heavy metal concentrations in urban soil were uncorrelated to those in urban dust, because the heavy metal concentrations in soil mainly reflected the long-term impact of urban pollution, while the concentrations in dust were associated with short-term emissions in the urban area. In most cities, the non-carcinogenic risk of heavy metals in urban soil and dust for children was largely at a safe level. Lead was the major contributor to the total health risk presented by heavy metals in urban soil and dust. More attention should be given to heavy metal contamination in urban soil and dust in cities with heavy industry and traffic.