Disinfection By-products in Drinking Water and Associated Human Health Risks in Urban Communities of Rivers State, Nigeria
Disinfection by-products (DBPs) formed during drinking-water treatment may pose chronic health risks when exposure is sustained. This study characterised regulated and emerging DBPs and evaluated screening-level human health risks in drinking water from eleven urban communities and one commercial sachet-water sampling category in Rivers State, Nigeria. Thirty-six samples (three per sampling category) were analysed for physicochemical characteristics, trihalomethanes (THMs), haloacetic acids (HAAs), chlorite, chlorate, bromate, haloacetonitriles and selected heavy metals using calibrated field meters, gas chromatography-mass spectrometry, ion chromatography and inductively coupled plasma-optical emission spectrometry. Total THMs ranged from 18.64 ± 1.42 to 96.82 ± 4.24 µg/L and total HAAs from 8.42 ± 0.62 to 52.84 ± 2.28 µg/L. Bromate ranged from 1.42 ± 0.12 to 12.48 ± 0.66 µg/L, while lead ranged from 0.002 ± 0.001 to 0.026 ± 0.002 mg/L. The highest TTHM concentration occurred in Eleme, while Bonny had the highest measured residual chlorine; therefore, the observed DBP pattern cannot be attributed to chlorine residual alone. Screening hazard indices were below one for adults but reached 1.08 for children in Eleme, whereas the reported incremental lifetime cancer-risk estimates remained within the conventional 10⁻⁶-10⁻⁴ screening range. Because water-source type was not balanced across locations and detailed treatment histories were unavailable, source comparisons are interpreted descriptively and causal attribution is avoided. The study provides baseline DBP data for the Niger Delta and supports routine DBP surveillance, precursor control, optimisation of disinfectant dose and contact time, and source-specific treatment audits without compromising microbiological safety.