Vinyl Chloride
Environmental Health Criteria, No 215
World Health Organization
ISBN-13    9789241572156 ISBN-10    9241572159
Order Number    11600215 Format    E-book collection (PDF)
Price    CHF    72.00 / US$    72.00 Developing countries:    CHF    50.40
English     1999        356   pages
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Summary
Evaluates the risks to human health and the environment posed by exposure to vinyl chloride, a colourless, flammable gas manufactured almost exclusively for use in the production of polyvinyl chloride (PVC). PVC is used to produce plastic materials having wide applications in the building sector, packaging, electrical appliances, medical care, agriculture, the automotive industry, and toys. Conclusive evidence that vinyl chloride causes cancer in humans led to the lowering, in the early 1970s, of occupational exposure limits in several countries. At the same time, many countries imposed restrictions on the levels of residual vinyl chloride permitted in PVC, thus reducing the risk that residues in packaging materials might contaminate food items, pharmaceutical products, and cosmetics. A chapter on sources of human and environmental exposure covers production levels and processes, noting the recent geographical expansion of production plants to South-east Asia, Eastern Europe, the Indian subcontinent, and oil-producing countries. Production technologies that lead to lower residual levels of PVC are also briefly described. A review of data on the environmental fate of vinyl chloride notes that environmental releases are almost entirely in the vapour phase. Vinyl chloride is rapidly volatilized and removed from surface water and soil, but is not easily biodegraded. Evidence suggests some bioaccumulation within the food chain, but no biomagnification. Concerning human exposure, the report concludes that atmospheric concentrations in ambient air are low, resulting in very little exposure of the general population. Much higher concentrations have been recorded near industry and waste disposal sites, and following accidental spills, including spills of chlorinated solvents in dry cleaning shops. Findings confirm a reduced risk of exposure for the general population via residues in packaging materials. The report identifies inhalation as the main route for occupational exposure, which occurs primarily in plants producing vinyl chloride and PVC. A chapter on kinetics and metabolism in laboratory animals and humans concludes that vinyl chloride is rapidly absorbed and widely distributed following exposure via the inhalation and oral routes. Following inhalation, the main metabolic route involves oxidation to form chloroethylene oxide, which is rapidly transformed to chloroacetaldehyde. Effects on laboratory mammals and in vitro test systems have been extensively studied. The compound shows low acute toxicity when administered by inhalation. Long-term feeding studies in several species show significantly increased incidences of liver angiosarcoma, hepatocellular carcinoma, and tumours at several other organ sites. An assessment of effects on humans draws on clinical findings following accidental exposures, supported by a large number of well-designed epidemiological studies of occupationally-exposed workers. Apart from defining the symptoms of "vinyl chloride illness", these studies provide strong and consistent evidence that vinyl chloride causes the rare tumour, angiosarcoma of the liver. Brain tumours and hepatocellular carcinoma may also be associated with exposure, though the evidence is less conclusive. On the basis of this analysis, the report calls for measures to minimize emissions at production sites and sanitary landfills, and to ensure low residual levels in PVC. Moreover, as vinyl chloride is a known carcinogen, the report stresses the need to keep occupational exposures as low as possible and to educate workers about the risks involved and the need for safe working procedures.