Page 3: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Vinyl Chloride
Part I. Overview and Application (continued)
Vinyl chloride is primarily a synthetic chemical. It can enter drinking water through leaching from polyvinyl chloride (PVC) pipes, from industrial discharges from chemical and latex manufacturing plants, or as a result of the biodegradation of synthetic solvents. Only one PVC manufacturing facility currently exists in Canada.
This guideline technical document reviews and assesses all identified health risks associated with vinyl chloride 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 vinyl chloride has been established at a maximum acceptable concentration of 0.002 mg/L (2 μg/L).
Vinyl chloride is classified as a human carcinogen, with sufficient evidence in both humans and animals. Vinyl chloride exposure has been linked with liver and neurological effects, in both humans (at occupational exposure levels) and animals. Liver cancer is the most serious endpoint that follows exposure from ingestion or inhalation of vinyl chloride.
The MAC has been established taking into consideration the most vulnerable population: Evidence from animal studies suggests that very young children (less than 5 weeks of age) may be twice as sensitive to the carcinogenic effects of vinyl chloride as adults. However, there are no human studies supporting these findings.
The general population is primarily exposed to vinyl chloride from inhalation of ambient air and the ingestion of items packaged in PVC containers, which may leach vinyl chloride. Exposure can also occur from drinking water, from sources of contamination in the environment, or from leaching of PVC pipes in the distribution system. However, vinyl chloride is rarely detected in Canadian drinking water supplies. There are no Canadian data on vinyl chloride levels in sediment, sewage or consumer products. Canadians may also be exposed to vinyl chloride from drinking water through inhalation and dermal absorption.
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. Vinyl chloride can be reliably measured in drinking water at the MAC.
At the municipal level, conventional treatment techniques are not effective at removing vinyl chloride. The best available technology for removing vinyl chloride is packed tower aeration. Taking into consideration currently available technologies, municipal treatment plant are expected to be able to consistently achieve concentrations below the MAC.
At the residential level, although there are no treatment units currently certified to remove vinyl chloride, treatment devices using treatment technologies such as activated carbon may remove vinyl chloride below the MAC if two or more units are installed in series.
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