Age dependent adjustment factor (ADAF) for the estimation of cancer risk through trihalomethanes (THMs) for different age groups- A innovative approach

Lifetime cancer risk due to trihalomethanes (THMs) in drinking water supplies for different age groups were investigated for the first time using age dependent adjustment factor (ADAF) as per USEPA protocol. Five water treatment plants (WTPs) in Eastern part of India were monitored for establishing the baseline concentrations of THMs and their seasonal variations. The concentration of THMs (231-484 mu g/L) in all WTPs exceeded the USEPA guidelines (80 mu g/L). Risk analysis of THMs through different pathways revealed that major risk ( > 97%) is caused through oral ingestion and is the most vulnerable pathway. Amongst different THMs, chloroform triggered the major risk through oral and dermal routes while BDCM for inhalation. The analysis of lifetime cancer risk for various age group dictated that it was highest (2.37 x 10(-4)) for 60-80 yrs age group while it was lowest (4.89 x 10(-5)) for 0-1 yr. The cancer slope factors for each THM species were combined with different exposure models and probability of cancer risks for different age groups. Monte Carlo simulations of cancer risk through different exposure routes dictated significant correlation between estimated and simulated risk. The average risk estimated through different exposure models lies well within +/- 2.75% of the simulated average risk.