Page 3: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Tetrachloroethylene
2.0 Executive summary
Tetrachloroethylene is primarily a synthetic chemical. In Canada, it is mostly used as a solvent in the dry cleaning industry and as an intermediate in chemical synthesis. Information on its release in drinking water is primarily from reported spills. Tetrachloroethylene has not been produced in Canada since 1992; it is still being imported, primarily from the U.S.
This guideline technical document reviews and assesses all identified health risks associated with tetrachloroethylene in drinking water, incorporating all relevant routes of exposure from drinking water—namely, ingestion as well as inhalation and skin absorption from showering and bathing.
It assesses new studies and approaches and takes into consideration the availability of appropriate treatment technology in order to establish a maximum acceptable concentration that is protective of human health, measurable and achievable by both municipal and residential scale treatment technologies. Based on this review, the drinking water guideline for tetrachloroethylene has been established at a maximum acceptable concentration of 0.010 mg/L (10 μg/L).
2.1 Health effects
Tetrachloroethylene has repeatedly caused various types of cancers in experimental animals by inhalation and ingestion, including liver tumors in mice and leukemia in rats. The cancer risk assessment was based on liver tumors in mice. Studies on the carcinogenic effects of tetrachloroethylene in humans, including those from long term occupational exposures, are inconsistent, and available evidence is not sufficient to draw conclusions regarding cancer effects.
Various non-cancer health effects related to inhalation or ingestion of tetrachloroethylene were observed in humans and/or animals. These effects include neurological, liver, kidney and reproductive/developmental effects. The non-cancer risk assessment was based on neurological effects (color confusion) in humans, occurring at the lowest level of exposure.
Both cancer and non-cancer risk assessments were considered in the derivation of the MAC. The non-cancer risk assessment produces a MAC that is protective of human health from both cancer and non-cancer effects.
Canadians can be exposed to tetrachloroethylene in the workplace or through its presence in air, drinking water, food and possibly through the use of specific consumer products. Exposure is mainly from air, particularly indoor air. Tetrachloroethylene is not frequently found in Canadian drinking water supplies, and its presence would normally be associated with a spill or another point source of contamination. Because tetrachloroethylene is highly volatile, it is more frequently found in groundwater than in surface water. When present in drinking water, it may be absorbed through ingestion, inhalation and skin absorption.
2.3 Analysis and treatment
The establishment of a drinking water guideline must take into consideration the ability to both measure the contaminant and remove it from drinking water supplies. Tetrachloroethylene can be reliably measured in drinking water at the MAC.
At the municipal level, conventional treatment techniques are not effective for the removal of tetrachloroethylene. The best available technologies for removing tetrachloroethylene from drinking water are packed tower aeration and granular activated carbon. Taking into consideration currently available technologies, municipal treatment plants are expected to be able to consistently achieve concentrations below the MAC.
At the residential scale, there are certified point-of-use treatment devices available that can remove volatile organic chemicals (VOCs) such as tetrachloroethylene from drinking water to meet the MAC. They rely on adsorption (activated carbon) technologies and may be installed at the faucet (point-of-use) or at the location where water enters the home (point-of-entry). From a health perspective, point-of-entry systems are preferred for the removal of VOCs, because they provide treated water for bathing and laundry as well as for cooking and drinking. This will decrease the potential for VOC exposure through inhalation.
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