Vinyl chloride

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What is Vinyl chloride?

• Vinyl chloride is an organochlorine with the formula H₂C=CHCl. It is also called vinyl chloride monomer of chloroethene. 
• This colourless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride. It is among the top twenty largest petrochemicals in world production.

Its impact on human health-

• It has been shown to cause liver cancer, as well as a nonmalignant liver disease known as TASH, or toxicant-associated steatohepatitis. 
• With TASH, the livers of otherwise healthy people can develop the same fat accumulation, inflammation and scarring (fibrosis and cirrhosis) as people who have cirrhosis from alcohol or obesity.
• That kind of damage typically requires relatively high levels of vinyl chloride exposure – the kind an industrial worker might experience on the job.
• However, exposures to lower environmental concentrations are still a concern. That’s in part because little is known about the impact low-level exposure might have on liver health, especially for people with underlying liver disease and other risks.
• Vinyl chloride is used to produce PVC, a hard plastic used for pipes, as well as in some packaging, coatings and wires.
• Its health risks were discovered in the 1970s at a B.F. Goodrich factory in the Rubbertown neighbourhood of Louisville, Kentucky. 
• Four workers involved in the polymerization process for producing polyvinyl chloride there each developed angiosarcoma of the liver, an extremely rare type of tumour.
• Their cases became among the most important sentinel events in the history of occupational medicine and led to the worldwide recognition of vinyl chloride as a carcinogen.
• The liver is the body’s filter for removing toxicants from the blood. Specialised cells known as hepatocytes help reduce the toxicity of drugs, alcohol, caffeine and environmental chemicals and then send away the waste to be excreted.
• The hallmark of vinyl chloride exposure to the liver is a paradoxical combination of normal liver function tests and the presence of fat in the liver and the death of hepatic cells, which make up the bulk of the liver’s mass. 
• However, the detailed mechanisms that lead to vinyl chloride-induced liver disease are still largely unknown.
• Recent research has demonstrated that exposure to vinyl chloride, even at levels below the federal limits for safety, can enhance liver disease caused by a “Western diet” – one rich in fat and sugar. 
• This previously unidentified interaction between vinyl chloride and underlying fatty liver diseases raises concerns that the risk from lower vinyl chloride exposures may be underestimated.
• In outdoor air, vinyl chloride becomes diluted fairly quickly. Sunlight also breaks it down, typically in nine to 11 days. 
• Therefore, outdoor air exposure is likely not a problem except with intense periods of exposure, such as immediately following a release of vinyl chloride. 
• Vinyl chloride is also dispersed in water.  

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