||The purpose of this study is to evaluate the drinking water quality of Kaohsiung city and its cancer risk potential to residents using city water. In this study, water qualities from different locations and seasons were collected and compared with drinking water quality standards. Total trihalomethanes (TTHM), which is the byproduct of disinfection process, has become one of the major concerns due to its high cancer risk potential. TTHM is composed of trichloromethane (TCM), dichlorbromomethane (BDCM), dibromochloromethane (DBCM), and tribromo methane (TBM), and the drinking water standard for TTHM is 0.1 mg/L. Effective on July 1, 2006, this standard will be revised to 0.08 mg/L, which is adopted from U.S. EPA. In this study, tap water quality data were provided from the technical office of Environmental protection Bureau, Kaohsiung City. These data were collected quarterly in 2004 and 2005 from 50 locations in the city water net system. Moreover, health and risk assessment models developed by US Environmental Protection Agency (EPA) were used for cancer risk calculation.|
Results from the water quality evaluation indicate that drinking water quality meets with the standards regulated by government. Except for TTHM, results show that sampling locations and seasons did not have significant influence on the variations in other water quality parameters.
Results of health and risk assessment of TTHM show that inhalation is the major route of risk exposure, which contributes 80.84% of the cancer risk. The dermal contact only contributes about 0.36% of the cancer risk. Among those four components of TTHM, TCM had higher detected concentrations. However, the major cancer risk came from BDCM and DBCM. Results reveal that the Chijin District (located at the end pipe area) of Kaohsiung city had the highest TTHM cancer risk (3.82×10-4), whereas Sanmin District (located at the front pipe area) got the lowest risk (4.10×10-5). The averaged TTHM health risk for the general public in Kaohsiung is about 1.50×10-4. This calculated risk is much higher than the acceptable risk value (≦10-6) recommended by US EPA. Thus, more stringent standards and more effective treatment technologies should be adopted by related authorities.