Most cases of cancer have no known cause but some are related to the exposure to certain chemicals, including Vinyl Chloride Monomer (VCM). From information on cancers in general, it is known that one single exposure does not develop a cancer. Only workers repeatedly exposed during many years to high levels (orders of magnitude higher than those currently permitted) have developed Angiosarcoma of the Liver (ASL). ASL is a very rare form of cancer of the blood vessels of the liver which has been known to pathologists for very many years.
Once it was known that there was a relationship with VCM, the association of Angiosarcoma of the Liver (ASL) with occupational exposure to VCM was established in 1974.
Once this association was established, industry led the way in reducing exposures drastically. We do not believe that any worker who started work after 1975 is currently at risk in plants located in the countries (such as Western Europe) where strict controls were introduced following the discovery of this problem. Some new cases of ASL may however still appear in workers who had high exposures before 1975.
Maximum permitted exposures are now set out in a E.U. Directive. Expert opinion and research has led European governments to be convinced that an exposure of 3 ppm during 8 hours a day through a full career of 40 years poses no significant risk to health. Typical levels in VCM and PVC manufacturing plants are lower and are monitored continuously.
ASL has been definitely linked to vinyl chloride exposure. Possible associations have been reported between exposure to high levels of VCM and other types of cancers. The International Agency for Research on Cancer (IARC) recently reviewed its assessment of the literature. This time, the conclusion of the experts was that there is “sufficient evidence” that vinyl chloride causes also hepatocellular carcinomas (HCC - cancer of liver cells). Proposals to recognise a link between VCM and cancers of other organs were rejected by a majority of the experts. The overall classification of VCM (Class 1) will not change. The main causes of HCC in the general population are hepatitis B and C as well as high alcohol consumption. It is possible that VCM might accelerate the development of a cancer in a liver already damaged by the hepatitis virus or ethanol, but the available information is not sufficient to substantiate this speculation.
