Evaluating the Health Risks of Heavy Metal Contamination in Drinking Water - A Comprehensive Risk Assessment

Humans are frequently exposed to heavy metals (HMs) and pathogens via assimilation of contaminated drinking water all over the world, especially in developing countries. This study aimed to evaluate drinking water quality and related human health risks in spring and tap water in Hangu District, Pakistan. Standard methods were employed for gathering samples (10 from spring water and 10 from tap water) from the predominant drinking water sources in the study areas. The samples were assessed for human health risk, HMs, physicochemical, and microbiological evaluations. In the study site, the water supplies were polluted with faecal coliform, demonstrating high bacterial pollution. A total of 72 bacterial isolates were obtained from water samples, 40 from spring water, and 32 from tap water samples. The physiochemical parameters such as turbidity (2.10-4.65 NTU), total suspended solids (3.80-5.30 mg/L), electrical conductivity (498.3-569.9 µS/cm), COD (4-9 mg/L), BOD (6-11 mg/L), Total Dissolved Solids (477.8-638.3mg/L), pH (7.2-7.5), sulphate (187.2-269.8 mg/L), nitrate (0.43-0.62 mg/L), sodium (255.1-238.4mg/L), chloride (217.7-290.4 mg/L), Ca hardness (149.1-228.0mg/L), Mg hardness (122.6—6136.7mg/L) and total hardness (412.2-456.6 mg/L) were analyzed for both water samples. The HMs concentrations, such as lead, Manganese, Chromium, and Cadmium, were assessed in drinking water by Atomic Absorption Spectrometry and then compared with limits set by WHO. The HMs were noted as Cd (0.011-0.017 mg/L), Cr (0.017-0.088 mg/L), Mn (0.015-0.083 mg/L), and Pb (0.003-0.008 mg/L). According to the World Health Organization drinking water quality standard, the majority of physical and chemical characteristics fell within acceptable limits.. However, the values of sodium ions, nitrate, sulphate, and chloride ions were beyond the limits of the WHO in some water samples. The potential health risks of HMs to the native population were also studied. The concentrations of all selected metals were within permissible limits. Health risk indicators like the health risk index and the chronic daily intake were measured for children and adults. The CDIs of metals were observed in the order of Cr > Cd >Mn > Pb and Mn > Cr > Cd > Pb for spring and tap water, respectively. The HRIs of HMs were observed in order of Cd > Mn > Pb >Cr and Cd >Mn > Cr > Pb for spring and tap water, respectively. There was no health threat to the indigenous community because the HRIs of the HMs in the drinking water for adults as well as children were less than 1.