The present study aims to assess the probable lifetime cancer and non-cancer risks of exposure to the trihalomethanes in Egypt's drinking water through ingestion, dermal contact, and inhalation. A total of 1667 drinking water samples were collected from twenty-three Egyptian governorates over a three-years period. The concentrations of total trihalomethanes ranged between 29.07 and 86.01 μg/L and were always below the maximum contamination level recommended by the Egyptian standards (100 μg/L). Chloroform was the most prominent trihalomethanes species, while bromoform was rarely detected. The cancer risk study revealed that, among the investigated paths, inhalation poses the greatest risk. And bromodichloromethane had the highest impact to cancer (69%), followed by chlorodibromomethane (28%). Geographically, the highest cancer risk value was found in Matruh governorate (42.2 × 10-6) and the lowest was in Minya governorate (1.0 × 10-6). The cancer risk for the studied governorates, except Minya governorate, was higher than the level recommended by the USEPA (1.0 × 10-6). Hazard index (HI) study revealed that the ingestion pathway caused higher HI values than the dermal pathway and that chloroform had the highest contribution to HI value. However, the values of HI were below unity in all studied governorates demonstrating that there would be negligible non-cancer risk.
Keywords: Cancer risk; Chlorination; Disinfection by-products; Gas chromatography; Hazard index.
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