Page 2: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – 1,2–Dichloroethane
A maximum acceptable concentration (MAC) of 0.005 mg/L (5 µg/L) is established for 1,2-dichloroethane in drinking water.
1,2-dichloroethane (1,2-DCA) is a volatile organic compound that does not occur naturally in the environment. It hasn't been produced in Canada since 2006, but is still imported, primarily for use in the synthesis of vinyl chloride and other organic chemicals.
This guideline technical document reviews and assesses all identified health risks associated with 1,2-DCA 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. Based on this review, the guideline for 1,2-DCA in drinking water is a maximum acceptable concentration of 0.005 mg/L (5 µg/L).
1,2-DCA is classified by Health Canada as a probable human carcinogen, based on inadequate evidence of carcinogenicity in humans, but sufficient evidence in animals. Animal studies have shown links between inhalation and/or ingestion of 1,2-DCA and various types of tumours in rats and mice. No conclusion of excess cancer linked to 1,2-DCA could be derived from the available studies in humans.
Various non-cancer health effects related to exposure to 1,2-DCA were observed in rodents, including immunological and renal effects, occurring at the lowest level of exposure. The non-cancer risk assessment was based on renal effects in rats.
Both cancer and non-cancer risk assessments were considered in the derivation of the MAC. The cancer risk assessment produces a MAC that is protective of human health from both cancer and non-cancer effects.
Canadians can be exposed to 1,2-DCA through its presence in air, drinking water, food and possibly through the use of specific consumer products or in occupational settings. Exposure is mainly from air, particularly indoor air. Because 1,2-DCA is highly volatile, its presence in water is usually associated with groundwater sources. 1,2-DCA is not frequently found in Canadian drinking water supplies. However, when present in drinking water, it may be absorbed through ingestion, inhalation and skin absorption.
1,2-DCA can readily be detected and analysed in drinking water supplies using the general methods used for volatile organic compounds (VOCs), at levels below the MAC.
Conventional treatment methods have little effect in reducing VOC concentrations. Municipal-scale treatment technologies effective at removing 1,2-DCA include air stripping (preferably using packed tower aeration), and granular activated carbon adsorption. At the residential scale, certified point-of-use treatment devices as well as a limited selection of point-of-entry devices are currently available for the reduction of VOCs, including 1,2-DCA.
Note: Specific guidance related to the implementation of drinking water guidelines should be obtained from the appropriate drinking water authority in the affected jurisdiction.
Generally, 1,2-DCA is not a concern for the majority of Canadians who rely on surface water as their source of drinking water, because it volatilizes easily. As levels of 1,2-DCA in treated water are generally very low, water suppliers are not expected to monitor the concentrations of 1,2-DCA in drinking water supplies on a routine basis.
Groundwater sources should be characterized to determine if 1,2-DCA is present, especially if the land use history is unknown. Quarterly monitoring for 1,2-DCA is recommended for groundwater sources that are or may have been impacted by spills or other potential contamination with this compound. VOCs and organic solvents in contaminated land may permeate some drinking water pipes and adversely affect water quality. The problem of permeation is generally limited to plastic and non-metallic materials.
The drinking water guideline is based on lifetime exposure to 1,2-DCA from drinking water. For drinking water supplies that occasionally experience short-term exceedances above the MAC, it is suggested that a plan be developed and implemented to address these situations. For more significant long-term exceedances that cannot be addressed through treatment, it is suggested that alternative sources of drinking water be considered.
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