A systematic review and probabilistic meta-analysis of health risks and disability-adjusted life years (DALYs) associated with heavy metals in global drinking water: a continental comparison.

Heavy metal contamination in drinking water is a public health issue. This study conducted a probabilistic meta-analysis of health risk assessment for six commonly reported heavy metals (arsenic [As], lead [Pb], mercury [Hg], cadmium [Cd], chromium [Cr] and nickel [Ni]) in drinking water across six continents (Asia, Europe, Africa, North America, South America and Oceania) using the data from 2000 to 2024. Human exposure and risks were quantified in terms of cancer risks (CRs) and loss of disability-adjusted life years (DALYs). Monte Carlo simulation was employed to generate 5,000 random scenarios to incorporate uncertainty in risk assessment. Africa exhibited the average concentrations of As, Pb, Hg, Cd, Cr and Ni in drinking water of 176.7, 123.3, 93.7, 80.2, 91.0 and 35.1 μg/L respectively. The overall averages of CRs in Asia, Europe, North America, South America, Africa and Oceania were predicted to be 3.25 × 10-4, 1.34 × 10-4, 2.26 × 10-4, 1.18 × 10-3, 4.1 × 10-3 and 5.83 × 10-5 respectively while the DALYs were 1.48 × 105, 7.14 × 103, 1.20 × 104, 5.51 × 104, 8.63 × 105 and 2.68 × 102 respectively. Across six continents, inorganic fraction of arsenic (iAs) was the dominant carcinogen, contributing (45-91) % to total cancer risks in Asia, contributions of iAs and Cd were almost similar. The loss of DALYs were highest in Africa (8.63 × 105), due mainly to arsenic-induced bladder and cadmium-induced lung cancers. The global economic burden was USD 29 billion, with Africa accounting for almost 52 %. Sensitivity analysis identified iAs as the key parameter. The heavy metal contamination is a public health issue that requires decisive actions in Africa, South America and Asia.