Health risk assessment of groundwater nitrate contamination: a case study of a typical karst hydrogeological unit in East China.

Nitrate pollution in rivers, lakes, shallow groundwater, and even deep groundwater occurs in many parts of the world. And, it's essential to assessing the relationship between nitrate pollution and human health, which is called human health risk assessment (HHRA). In this paper, groundwater samples were collected for their nitrate content in a typical karst hydrogeological unit in East China during the wet and dry seasons. Then, a human health risk assessment was conducted using the four-step risk assessment process developed by the US Environmental Protection Agency (USEPA), which aimed to determine the potential risk posed to human health by nitrate in the groundwater. To make the assessment more authentic and objective, the drinking water and dermal contact exposure pathways were considered, and the people were divided into four groups, including infants (0~6 months), children (7 months~17 years old), females (18 years and older), and males (18 years and older), in the wet and dry seasons to determine the impacts of the exposure pathway, age, sex, and precipitation period. The results indicated that more than half of the groundwater samples exceeded 10 mg/L (measured as nitrogen), which is the drinking water standard of China. The children and infants had greater health risks than the adults at the same groundwater nitrate concentration, and those two groups need to be paid more attention; the adult females had a greater health risk than the adult males in the two precipitation periods, which shows that the order of the health risk was infants ˃ children ˃ adult females ˃ adult males. In addition, the value of the hazard quotient (HQ) and the area of the adverse effects were both higher in the wet season than in the dry season, which explains that precipitation can affect the human health risk as well. The HQ caused by the drinking water exposure pathway was much higher than that caused by the dermal contact exposure pathway. This study can provide information for more effective and reasonable decisions to city managers for groundwater nitrate pollution prevention.