Heavy metal contamination and human health risk assessment in drinking water from shallow groundwater wells in an agricultural area in Ubon Ratchathani province, Thailand

Most local people in the agricultural areas of Hua-ruea sub-district, Ubon Ratchathani province (Thailand), generally consume shallow groundwater from farm wells. This study aimed to assess the health risk related to heavy metal contamination in that groundwater. Samples were randomly collected from 12 wells twice in each of the rainy and the dry seasons and were analyzed by inductive coupled plasma spectrometry-mass spectrometry (ICP-MS). The concentration of detected metals in each well and the overall mean were below the acceptable groundwater standard limits for As, Cd, Cr, Cu, Hg, Ni and Zn, but Pb levels were higher in four wells with an overall average Pb concentration of 16.66 ± 18.52 μg/l. Exposure questionnaires, completed by face-to-face interviews with 100 local people who drink groundwater from farm wells, were used to evaluate the hazard quotients (HQs) and hazard indices (HIs). The HQs for non-carcinogenic risk for As, Cu, Zn and Pb, with a range of 0.004-2.901, 0.053-54.818, 0.003-6.399 and 0.007-26.80, respectively, and the HI values (range from 0.10 to 88.21) exceeded acceptable limits in 58 % of the wells. The HI results were higher than one for groundwater wells located in intensively cultivated chili fields. The highest cancer risk found was 2.6 × 10^-6 for As in well no. 11. This study suggested that people living in warmer climates are more susceptible to and at greater risk of groundwater contamination because of their increased daily drinking water intake. This may lead to an increased number of cases of non-carcinogenic and carcinogenic health defects among local people exposed to heavy metals by drinking the groundwater.