Trihalomethanes in desalinated water: Human exposure and risk analysis

Desalinated seawater is used to satisfy domestic water demands in many countries. The treated freshwater is blended with desalinated water to increase the water supply. The desalinated and blended water contains disinfection byproducts (DBPs), some of which may induce cancer risk to human. In this study, concentrations of trihalomethanes (THMs) in desalinated and blended water in Saudi Arabia were investigated, and human exposure and risk were predicted. The intakes of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) were predicted to be 8.38 × 10⁻⁵, 7.57 × 10⁻⁵, 2.54 × 10⁻⁵, and 4.32 × 10⁻⁴ mg/kg-d, respectively. The overall cancer risk and hazard index were estimated to be 1.78 × 10⁻⁵ (range: 7.40 × 10⁻⁷–9.26 × 10⁻⁵) and 3.49 × 10⁻² (range: 1.20 × 10⁻³–2.34 × 10⁻¹), respectively. The probabilities of cancer risk exceeding the risk levels of 1 × 10⁻⁶, 1 × 10⁻⁵, and 5.0 × 10⁻⁵ were 1.0, 0.775, and 0.012, respectively. The loss of disability adjusted life years (DALYs) was predicted to be 25.1 per year while the cancer risk represented 8.48 × 10⁻⁷ DALY per person per year. The financial burden from such risk was estimated to be US$ 2.72 (range: US$ 2.52–2.91) million per year. The findings may assist in better understanding and reducing cancer risk from DBPs in desalinated and blended water.