Potential Risks Assessment of Trihalomethanes in Drinking Water Supply

Chlorine is widely used in the disinfection process of water supply systems to eliminate pathogens. However, a complication that occurs during the disinfection process is the formation of by-products that include volatile organic compounds such as chloroform and other trihalomethanes. This study is intended to assess the risk of trihalomethanes in tap water. Water samples were taken from end-user tap water near wastewater treatment plants in various locations in Perlis, Malaysia. Following the standard procedure and calculation method proposed by the US EPA, the exposure dose (mg/kg day)) for oral ingestion, dermal absorption and inhalation was calculated. A total of 90 independent data were obtained from the Perlis regions. Risk assessments were calculated and three groups were formed to represent three separate waste water treatment plants. The assessment of cancer risk in the Timah Tasoh area by ingestion routes for dibromochloromethane, bromo-dichloromethane and chloroform was 3.04 × 10 –5 , 1.73 × 10 –4 , and 2.67 × 10 –5 , while for the dermal pathway it was 6.65 × 10 –4 , 3.97 × 10 –4 , and 7.19 × 10 –5 and inhalation for dibromochloromethane, bromodichloromethane, bromoform and chloroform—1.33 × 10 –3 , 1.02 × 10 –3 , 1.38 × 10 –3 , and 6.32 × 10 –5 . Another study area, Kuala Sungai Baru, has the lowest trihalomethane content. Obviously, the lowest risk as some of the compounds were found to be below the US EPA limit. The combined risk of cancer in these three study areas for the ingestion method was 1.23 × 10 –5 , 1.07 × 10 –4 , and 1.11 × 10 –5 . The results showed that the carcinogenic risk assessed for chloroform, bromodichloromethane and dibromochloromethane was within the established limit in some areas, but exceeded the acceptable level in other areas of the study. In addition, the greatest risk from trihalomethanes appears to arise from inhalation followed by ingestion and skin contact. This study made the Perlis Exploration Area Warning as a reference point for other nearby areas.