Health risk assessment of trihalomethanes from tap water in Karachi,Pakistan

Risk assessment study of trihalomethanes (thms) through different exposure pathways is based on the results of thms concentration in tap water samples collected from various locations of karachi city. the lifetime cancer risk and hazard index of each thm species were used to estimate the health risk from thm exposure through oral ingestion and dermal absorption. exposure to chcl3 either through ingestion or dermal contact was found to be the most important pathway for cancer risks from thms. it was also found that the residents of karachi have a higher risk of cancer through oral ingestion than through the dermal absorption. the mean hazard index value of total trihalomethanes (tthms) through oral ingestion and dermal absorption was calculated to be 8.84×10 -2 and 4.39×10-3,respectively. the results of hazard index were found lower than unity,which did not indicate the non-cancer effects of thms. on the basis of cancer risk analysis,it is expected that approximately 2 of the 18 million population of karachi could get cancer each year due to exposure to the thms.