What are the health effects associated with THMs?
The Federal-Provincial Subcommittee on Drinking Water established the current guideline for THMs in 1993. The guideline is based on the risk of cancer reported in animal studies of chloroform, the THM most often present and in greatest concentration in drinking water. Since then, new epidemiological (human) studies had been published which reported associations between THMs and bladder and colon cancer, and adverse pregnancy outcomes including miscarriage, birth defects and low birth weight. In response to these new findings Health Canada, in its role as Secretariat to the DWS, established a multi-stakeholder task group in 1998 to oversee a comprehensive update of health risk information on THMs and to develop recommendations for controlling the risks.
