Risk assessment of trihalomethanes in drinking water with seasonal variation considerations.

This study evaluated the concentrations of trihalomethanes (THMs) in Alexandria’s drinking water across seven districts during summer and winter, and assessed the associated cancer risks. THMs, byproducts of water chlorination, are known for their potential carcinogenicity. A total of 35 drinking water samples were analyzed using gas chromatography with an electron capture detector (GC-ECD) to determine the concentrations of chloroform (CF), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (BF). The results revealed significant seasonal variations. Region-2 recorded the highest summer concentration (150 µg/L), while Region-7 had the highest winter concentration (196 µg/L). Hazard index (HI) calculations indicated that chloroform contributed the most to non-carcinogenic risks, with Region-7 recording an HI of 0.5698 in winter, while Region-2 showed a summer HI of 0.4843. Carcinogenic risk assessments using the USEPA methodology showed lifetime cancer risks significantly exceeding the acceptable threshold of 1 × 10−6, with an annual average total cancer risk of 67.027 × 10−6. These outcomes highlight the critical need for Alexandria to adopt advanced water treatment methods, such as ozonation and UV disinfection, optimize chlorine dosing, and strengthen routine monitoring to ensure compliance with safety standards and protect public health to safer drinking water and better health outcomes for Alexandria’s residents.