Page 3: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Trichloroethylene

2.0 Executive Summary

Trichloroethylene (TCE) is a volatile solvent that is used extensively in the automotive and metals industries for vapour degreasing and cold cleaning of metal parts. TCE is not manufactured in Canada, and its use is regulated under the Canadian Environmental Protection Act, 1999. Canadians can be exposed to TCE through its presence in drinking water, air and food. Certain segments of the population could be exposed via contaminated soil or occupational settings.

This supporting document focuses on the health risks associated with TCE in drinking water, including multiple routes of exposure -- ingestion as well as inhalation and skin absorption from showering and bathing. It assesses all identified health risks, taking into account new studies and approaches, and incorporates appropriate safety factors. The guideline of 0.005 mg/L will protect humans from both cancer and non-cancer health risks.

2.1 Health Effects

Animal studies have shown links between exposure to TCE and kidney and testicular tumours in rats and pulmonary and liver tumours in mice. Studies in humans seem to support these links, but further studies are needed to confirm them, in part because other chemicals were also present. Based on the evidence from both animal and human studies, TCE has been classified as probably carcinogenic to humans. Research is ongoing in this area.

Animal and human studies have shown a small increase in the rate of reproductive effects (heart malformations in fetuses) above what can be expected under normal circumstances. The data from the human studies came from people who had been exposed to very high levels of TCE and other solvents through contaminated groundwater. Further studies are required to confirm these developmental effects as well as their long-term significance to human health.

2.2 Exposure

TCE evaporates readily from surface water but may occasionally be found in groundwater. TCE is not a concern for the majority of Canadians who rely on surface water as their source of drinking water. TCE is not a widespread problem in Canada, affecting only some groundwater supplies; where TCE is detected in Canadian drinking water supplies, levels are generally less than 0.001 mg/L. TCE can be introduced into groundwater as a result of industrial effluents or spills or leaking from old dump sites.

2.3 Treatment

Options to reduce exposure to TCE include finding an alternative source of drinking water; enhancing treatment to reduce the level of TCE in the drinking water to below the proposed guideline in municipal systems relying on groundwater supplies; and using drinking water treatment devices where individual households obtain drinking water from private wells. Health Canada recommends that consumers use certified treatment devices. Point-of-entry systems are preferred for volatile organic compounds (VOCs) such as TCE because they reduce exposure through inhalation and dermal absorption by providing treated water for bathing and showering. Although certified point-of-use treatment devices are currently available for the reduction of VOCs, including TCE, certified point-of-entry treatment devices cannot be purchased off the shelf; however, systems can be designed and constructed with certified materials.

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