Heavy Metals, Microbial Contamination, and Health Risks in Groundwater of Coal Mining Regions: Carcinogenic and Noncarcinogenic Insights

Groundwater contamination poses a growing threat to environmental quality and human health, particularly in regions affected by mining and agricultural activities. This study evaluated groundwater quality and associated carcinogenic and noncarcinogenic health risks in coal mining regions of Pakistan. We quantified bacterial contamination (nutrient and MacConkey agars), physicochemical properties (pH, temperature, EC, and TDS), heavy metals (Cd, Cr, Ni, Pb, Cu, and Fe), and major ions (Na⁺, Mg²⁺, Cl^-, F^-, SO₄ ^2-, and NO₃ ^-); benchmarked values against WHO limits; and estimated health risk exposure using EDD, THQ, HI, and cancer risk (CR/TCR) for adults and children. Widespread bacterial growth was detected. EC, temperature, Cd, Cr, Ni, Pb, Na⁺, SO₄ ^2-, Cl^-, and NO₃ ^- varied significantly across sites, and several parameters (Cd, Pb, Cr, Fe, NO₃ ^-, SO₄ ^2-, Na⁺, TDS, and temperature) exceeded WHO guidelines. Correlation analysis showed strong positive associations among several metals and ions. Noncarcinogenic risk exceeded safety thresholds (HI: adults 4.85-8.01; children 7.76-10.95). Carcinogenic risk from Cd, Cr, and Pb surpassed acceptable levels (TCR: adults 1.06 × 10^-3-2.19 × 10^-3; children 2.16 × 10^-3-4.49 × 10^-3). Groundwater is chemically and microbially compromised, posing unacceptable risks particularly to children necessitating urgent monitoring and mitigation.