Holistic approach to assess human health risks, integrating physicochemical quality attributes and heavy metal levels in tap water

Heavy metal contamination is a serious concern affecting the safety of tap water sources. Hence, this study evaluated physicochemical quality indices, carcinogenic and non-carcinogenic health hazard derived from the level of toxic metals in tap water in Gondar city, Ethiopia. The results revealed that except dissolved oxygen, salinity and nitrite, all quality attributes were below the allowable quality standards. The average concentrations for iron (Fe), copper (Cu), lead (Pb), chromium (Cr) and cadmium (Cd) were ranged from 0.003 mg/L to 5 mg/L, 0.475 mg/L to 0.752 mg/L, 0.14 mg/L to 0.703 mg/L, 0.261 mg/L to 2.182 mg/L, and 0.035 mg/L to 4.286 mg/L, respectively. The mean levels of metals in different areas decreased in the order: AR > AZ1 > PS1 > AZ3 > PS2 > MR > PS3 > SHD > AZ2 > CL. Except for Cu, the concentration of Fe, Pb, Cr, and Cd exceeded the safe limits described by WHO/FAO. According to principal component analysis and cluster analysis, anthropogenic activities were found to be the major source of metals. Chronic daily intake (CDI), target hazard quotient (THQ), hazard index (HI), and incremental lifetime cancer risk assessment (ILCR) were employed to evaluate human health risks. Except for Pb in AZ1, PS3, and AR, the values of THQ for both ingestion and dermal pathways from the analysed metals for adults were within the safety limits (THQ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo><</mml:mo></mml:math> 1). However, the distribution pattern of HI values were presented in the decreasing order: PS1 > PS2 > AZ3 > MR > PS3 > AR > AZ2 > AZ1 > SHD > CL. Except, the HI values in CL, all values were greater than one (HI > 1), indicating that tap water in these areas may pose non-carcinogenic health risk. The analysis of carcinogenic health risks indicated that the lifetime cancer risk (ingestion and dermal exposure pathways) of heavy metals were in accordance with the acceptable range for tap water (10^-6 - 10^-4). This finding provides valuable input for the development of precise action plans aimed at elevating water quality standards in the studied areas.