Groundwater heavy metal levels and associated human health risk in the North China Plain

Heavy metals in domestic water are a serious threat to human health. In this study, 139 groundwater samples were collected from rural wells in the villages of five cities in the middle region of the North China Plain along two transects. Statistical analysis and human health risk assessment were conducted to determine the distribution of heavy metals and the associated human health risk from ingestion and dermal adsorption of local groundwater. The results show that the mean concentrations of heavy metals in local groundwater are in the order: Mn > Zn > Cr > Ni > As > Se > Cu > Pb > Cd; with the exception of some sampling stations of Mn and Ni, concentrations for all metals have not exceeded the drinking water standard. Most of the highest pollution stations are in the middle part of urban areas. Mn-As and Cr-Cu are divided into groups by cluster analysis, indicating either the same source or similar transport behaviors. All of the values of the calculated HItotal (the non-carcinogenic risk) range from 1.28 x 10(-2) to 5.54 x 10(-1), indicating no or slight chronic risk to residents from heavy metals in groundwater. Average values of R (ingestion) (carcinogenic risk caused by ingestion) for As, Cr, and Cd are between 1 x 10(-6) and 1 x 10(-4), indicating a slight carcinogenic risk from heavy metals in groundwater. Although several policies have already been implemented in the study area to ensure the safety of drinking water for residents, the local administration should continue to direct significant attention to groundwater pollution from heavy metals.