The lifetime
cancer risk and the hazard index of
trihalomethanes (THMs) through oral ingestion, dermal absorption, and inhalation exposure from supply water of five WTPs were analysed. THMs concentration varied from plant to plant and was found to be in the range of 274-511µg/l, which is much higher than the prescribed USEPA standards of 80µg/l.
Chloroform was the most dominant THM followed by
bromodichloromethane (BDCM), and
dibromochloromethane (DBCM).
Cancer risk analysis through multi-pathways exposure reveals that residents had a higher
cancer risk through oral ingestion than other two routes of exposure. The lifetime
cancer risks of THMs from supply water were 100 times higher than prescribed USEPA guidelines. The higher
cancer risk found for Indian context than those reported for other countries like USA, UK, Japan, Australia, is mainly due to the higher concentration level of THMs, water intake and average
body weight. The study also revealed that amongst different THMs,
chloroform is the major THMs causing
cancer risk through both oral and dermal route of exposure whereas in case of inhalation it was mainly because of BDCM. Average lifetime
cancer risk analysis indicated that females are more prone to
cancer risk than males. Oral ingestion is a major route indicating the potential impact of non-
cancer risk while it was insignificant through dermal exposure. Sensitivity analysis of THMs revealed that
chloroform is the predominant parameter followed by
body weight and exposure duration influencing
cancer risk.