Integrated Assessment of Cumulative Health Risk Index and Lifetime Cancer Risk of Groundwater Heavy Metals in Bokkos Town, Plateau State, Nigeria

Abstract

Groundwater is the main source of drinking water in Bokkos Town, Plateau State, Nigeria. This study assessed water quality and human health risks using hydrochemical analysis, statistical evaluation, and the USEPA risk framework. Twenty sources (17 wells, 3 boreholes) were sampled for manganese (Mn), chromium (Cr), and arsenic (As) using Atomic Absorption Spectrophotometry. Risks were quantified using Hazard Quotient (HQ), Hazard Index (HI), Total Carcinogenic Risk (TCR), and child-to-adult TCR ratios. Results showed mean concentrations of Mn (0.074 mg/L), Cr (0.055 mg/L), and As (0.014 mg/L), with several samples exceeding WHO limits, particularly Mn and As. Non-carcinogenic risk analysis indicated elevated HI at multiple sites, with children showing greater vulnerability. Carcinogenic risk assessment revealed most sources exceeded the USEPA acceptable threshold (1.0 x 10-3 ), with BIO having the highest TCR (adult: 2.48 x 10-3 ; child: 5.02 x 10-3). Pearson correlation indicated strong positive associations, especially between Cr and As (r = 0.82, P < 0.01). One-sample t-tests confirmed significant exceedances for Mn (t = 2.45, P = 0.024) and As (t = 3.98, P = 0.001). Arsenic and manganese are major contaminants, with children disproportionately affected. Recommendations include regular groundwater monitoring, provision of safe water sources, public awareness campaigns, and enforcement of water quality regulations to reduce exposure and protect vulnerable populations.