Beijing Water Trihalomethanes Health Risk Assessment

Trihalmethanes (THMs) is composed of chloroform(TCM),bromodichloromethane (BDCM), dibromochloromethane (DBCM) and brmoform (TBM). The THMs in reused water is a kind of disinfectant by-pruduction that result from its chlorination .A larger number of studies in animals experiment demonstrated that THMs is carcinogen. Some epidemiology studies also show THMs is harmful to human Health.This study use the method of combination of sampling action detect and model prediction to test and predict the range of THMs' concentration in reused water in Beijing, and survey and analysis the exposure ways and level of occupational worker and unoccupational populations to THMs when the reused water was used in road clearing and public garden greening ,based on this background , human health risks assessment method was used to evaluate health affect of THMs in reused water on population, and to derivate the guidance values of TCM and BDCM for health-based exposure limits in reused water in Beijing .The results are as following :1. In Beijing's reused water, the major hazardous substances in THMs are TCM and BDCM.2．When beijing's reused water was used in road cleaning, the influence of THMs for occupational worker is:For the driver who is working on raod cleaning , cancer risk of THMs is smaller than 10-6,,uncancer risk is far smaller than 10-6. For the driver who will work on raod cleaning during his life , the cancer risk of THMs is little more than 10-5,uncancer risk is smaller than 10-6; the influence of THMs for unoccupational worker is:For pedestrian on road and worker beside road the cancer risk of THMs is smalle than 10-5,uncancer risk is smaller than 10-6. 3.When beijing's reused water was used in public garden greening, the influence of THMs for occupational worker is: For the gardener who is working on public garden greening, cancer risk of THMs is little more than 10-5, uncancer risk is far smaller than 10-6. For the gardener who will work on public garden geening during his life , the cancer risk of THMs is little more than 10-5,uncancer risk is smaller than 10-6; the influence of THMs for unoccupational populations is:For the youth who was at park , the cancer risk of THMs is little more than 10-5, for the youth and the old who was at park uncancer risk is smaller than 10-6.4.When Beijing's reused water was used in road cleaning, the guide value for TCM and BDCM is 576 ug/l and 533 ug/l, respectively.When beijing's reused water was used in public garden greening, the guide value for TCM and BDCM is 500 ug/l and 466 ug/l, respectively.