Assessment of disinfection by-products levels in selected bottled waters and swimming pools in Nigeria with it’s associated health risks

Trihalomethanes (THMs) are common disinfection by-products (DBPs) formed during water treatment and are associated with potential adverse health effects, including carcinogenic risks. Despite these concerns, there is limited information on the occurrence and health risks of THMs in bottled waters and swimming pools in Nigeria. This study determined the concentration of the DPBs (particularly THMs) of some bottled waters and swimming pools in Nigeria and evaluated possible health risk associated with it. The physicochemical parameters were determined using association of official analytical chemists standard methods. The THMs in bottled waters and swimming pools were pre-concentrated using liquid–liquid extraction method and determined using gas chromatography. The health risk assessment was done using the hazard index and cancer risk models. Results of the physicochemical parameters for both bottled waters and swimming pool samples were within the World Health Organization (WHO) acceptable limit except for pH, total hardness, chloride, conductivity, phosphate and turbidity of some samples. The total concentration of THMs for bottled water across the six brands were 0.631 ± 0.004, 0.407 ± 0.001, 0.471 ± 0.002, 0.420 ± 0.004, 0.611 ± 0.001 and 0.511 ± 0.002 µg/L, while that of the six different locations of swimming pools were 2.080 ± 0.004, 2.542 ± 0.001, 4.166 ± 0.002, 1.997 ± 0.004, 2.171 ± 0.001 and 2.284 ± 0.002 µg/L. The THMs concentrations of swimming pool samples were significantly higher than that of bottled waters, although both were below the WHO and European Union standards. Significant correlation was observed between the physicochemical parameters and the THMs. The cancer risk assessment for oral and dermal exposure routes to THMs for both adults and children were negligible and within acceptable low risk level offered by United states Environmental Protection Agency. Some of the cancer risks for oral exposure routes were within (1 × 10⁻⁶ ≤ LCIR ≤ 5.1 × 10⁻⁵) which is classified as acceptable low cancer risk level while the rest were within the negligible cancer risk level. The health hazard index for oral and dermal exposure routes for both adult and children were below 1, therefore may not pose any health risk. Although the health risk assessment of this study shows potentially not toxic, it is recommended that proper monitoring and awareness should be enforced to prevent further formation of THMs in these water samples because with prolonged consumption and exposure there is a probability of it posing a health risk.