Vinyl chloride
(endorsed 1996)
Guideline
No safe concentration for vinyl chloride in drinking water can be confidently set. However, for practical purposes, the concentration should be less than 0.0003 mg/L, which is the limit of determination.
General description
Vinyl chloride is used industrially in the production of poly vinyl chloride (PVC), which has wide application in the plastics, rubber, paper and glass industries.
Vinyl chloride may be present in drinking water through pollution of water sources by chemical spills. Water bottled and stored for long periods in PVC containers may contain very low concentrations of vinyl chloride. It has occasionally been detected in drinking water supplies that use PVC pipes in the United States and Germany, with a maximum reported concentration of 0.01 mg/L. In Australia there are stringent requirements on the maximum permissible residual vinyl chloride concentrations in PVC pipes and fittings.
Typical values in Australian drinking water
Vinyl chloride has not been found in Australian drinking waters. It is included here to provide guidance in the unlikely event of contamination, and because it has been detected occasionally in drinking water supplies overseas.
Treatment of drinking water
There are no published reports on methods for the removal of vinyl chloride from drinking water.
Measurement
A purge and trap gas chromatographic procedure can be used for the analysis of vinyl chloride (USEPA Draft Method 502.1 1986). An inert gas is bubbled through the sample and vinyl chloride trapped on an adsorbent. The adsorbent is then heated and vinyl chloride analysed using gas chromatography with electron capture detection. The limit of determination is 0.0003 mg/L.
Health considerations
Vinyl chloride is readily absorbed following ingestion. It is metabolised to chloroethylene oxide, which can rearrange spontaneously to chloroacetaldehyde. Both substances are highly reactive and mutagenic.
In humans, vinyl chloride is a narcotic agent, and occupational exposure to high doses causes a number of symptoms including Raynaud’s phenomenon, a painful disorder of the hands. This is not a concern for environmental exposure.
Vinyl chloride is a well-documented human carcinogen, with inhalation of high concentrations causing tumours in the liver, particularly angiosarcoma. Tumours in the brain and lung and malignancies of the lymphatic and haematopoietic tissues have also been reported.
No data are available on oral exposure in humans.
Vinyl chloride is also carcinogenic to animals. When administered by inhalation at doses above 100 ppm in air, it induced tumours of the liver and of some other organs in rats, mice and hamsters. Oral administration resulted in dose-related tumours of the liver at a dose of 14 mg/kg body weight per day. Some tumours were also observed in other organs, including the lungs and mammary glands.
Vinyl chloride has exhibited mutagenic activity in a variety of tests on bacteria and mammalian cells.
The International Agency for Research on Cancer has concluded that vinyl chloride is carcinogenic to humans (Group 1, sufficient evidence of carcinogenicity in humans) (IARC 1987).
Derivation of guideline
Vinyl chloride is a genotoxic human carcinogen, and there is no safe or acceptable concentration for vinyl chloride in drinking water. The guideline of less than 0.0003 mg/L is based on a consideration of health effects in relation to the limit of determination.
i) The excess risk of lifetime consumption of drinking water with a vinyl chloride concentration of 0.0005 mg/L was conservatively estimated by the World Health Organization (WHO), using a linear multistage model, at one additional cancer per million people.
ii) A value of 0.0005 mg/L can also be derived as follows:
where:
0.13 mg/kg body weight per day is the no-effect level from lifetime studies using rats (Feron et al. 1981, Til et al. 1991). Tumours were reported at higher doses.
70 kg is the average weight of an adult.
0.1 is the proportion of total daily intake attributable to the consumption of water.
2 L/day is the average amount of water consumed by an adult.
1000 is the safety factor in using the results of an animal study as a basis for human exposure (10 for interspecies variations, 10 for intraspecies variations and 10 for evidence of carcinogenicity).
The limit of determination is slightly less than the values derived from health considerations, and provides an adequate degree of protection. This is consistent with the general approach adopted for genotoxic human carcinogens (see Section 6.3.4).
The WHO guideline value of 0.005 mg/L was based on a calculation that estimated an additional lifetime risk of one fatal cancer per 100,000 people.
References
Feron VJ, Hendriksen CFM, Speek AJ, Til HP, Spit BJ (1981). Lifespan oral toxicity study of vinyl chloride in rats. Food and Cosmetics Toxicology, 19:317–333.
IARC (International Agency for Research on Cancer) (1987). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Overall Evaluations of Carcinogenicity. An updating of IARC monographs volumes 1 to 42. World Health Organization, IARC, Supplement 7.
Til HP, Feron VJ, Immel HR (1991). Lifetime (149-week) oral carcinogenicity study of vinyl chloride in rats. Food and Chemical Toxicology, 29:713–718.
USEPA Draft Method 502.1 (1986). Volatile halogenated organic compounds in water by purge and trap gas chromatography. United States Environmental Protection Agency, Environmental Monitoring and Support Laboratory (EMSL), Cincinnati, Ohio.
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