Heavy metals contamination in soil, surface water, crops, and resident blood in Uthai District, Phra Nakhon Si Ayutthaya, Thailand

This study evaluates the heavy metal (As, Cd, Cu, Hg, Pb, and Zn) contamination in soil, surface water, and crops in Uthai District, Ayutthaya Province, Thailand, an agricultural area located near an industrial park. Further, the blood levels of these metals in residents living in the study area are investigated. The concentrations of the six metals in soil were below the values permitted under the Soil Quality Standard, Thailand. In contrast, the concentrations of As and Hg in surface water exceeded the permissible limits. For the crops, all heavy metal values in eggplant, kale, and rice were at safe levels. However, in basil, both Hg and Cu levels exceeded the permissible limits, and in coriander, Hg content exceeded the permissible limit. Additionally, the potential health risks of heavy metal exposure through consumption of local crops were assessed using target hazard quotients (THQs) and hazard indices (HIs). The former values of the crops varied. 100.0% for As, 40% for Cd, 60% for Cu, 20% for Pb, and 30% for Zn of the analyzed samples had THQs above 1. This indicated that consumers were probably exposed to some non-carcinogenic health risk (except for Hg which was 0%). Of greater concern, the HI values of each consumed crop were > 1, indicating obvious risk of adverse health effect. Finally, the heavy metal levels in blood from a sample of local residents (n = 16) were assessed along with blood chemistry tests. The levels of all heavy metals were within the normal ranges. Nevertheless, heavy metal contamination in both the environment and food crops raise concerns of health risks to the residents of this area.