Assessment of the potential health risks of heavy metals in soils in a coastal industrial region of the Yangtze River Delta

Soil heavy metal contamination is a serious environmental problem. Human beings may be directly exposed to heavy metals in soils through the inhalation of soil particles, dermal contact, and oral ingestion, which can seriously threaten health. This study assesses the health risks associated with heavy metals in soils by determining the concentrations of eight heavy metals (Cr, Pb, Cd, Hg, As, Cu, Zn, and Ni) based on 2051 surface-soil samples collected from the southern Yangtze River Delta of China. The mean concentrations were higher than the corresponding background values in Zhejiang Province and China as a whole, indicating an accumulation of heavy metals. The health risk assessment suggests that the non-carcinogenic and carcinogenic risks in the study area were not significant. The non-carcinogenic risk for children was the highest, followed by those for adults and seniors; the non-carcinogenic risk for the entire population was less than 1.0, the predetermined threshold. Carcinogenic risk for adults was the highest, followed by those for seniors and children; a few sample points had a value larger than the threshold of 1.0E-04. Arsenic represented the greatest contribution to non-carcinogenic and carcinogenic risk. Meanwhile, ingestion of heavy metals in soil was the main exposure pathway for carcinogenic risk, followed by inhalation and dermal exposure. The spatial method of Getis-Ord was used to identify hot spots of health risk. Hot spots with high hazard index (HI) and total carcinogenic risk (TCR) for children, adults, and seniors were mainly distributed in core urban areas, such as Jiangbei, Haishu, Yinzhou, Jiangdong, and the urban areas of some other counties, which coincided with industrial, mining, and urban areas of the study area and were strongly influenced by anthropogenic activities. These results provide a basis for heavy metal control in soil, source identification, and environment management in the Yangtze River Delta and other rapidly developing industrial regions in China.