Health & Environmental Research Online (HERO)


Print Feedback Export to File
4072469 
Technical Report 
Vinyl halides (selected) 
National Toxicology Program :: NTP 
2016 
U.S. Department of Health and Human Services, National Toxicology Program 
Research Triangle Park, NC 
Report on Carcinogens 
8 
English 
is part of a larger document 3827262 14th Report on carcinogens
Vinyl bromide, vinyl chloride, and vinyl fluoride belong to a class of structurally related chemicals referred to as “simple vinyl halides” or “halogenated olefins.” These three vinyl halides are listed in the Report on Carcinogens as individual chemicals and not as a class. (The class also includes vinyl iodide, which is not listed in the Report on Carcinogens.) Vinyl chloride was first listed in the First Annual Report on Carcinogens (1980) as known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans, and vinyl bromide and vinyl fluoride were first listed in the Tenth Report on Carcinogens (2002) as reasonably anticipated to be human carcinogens based on sufficient evidence of carcinogenicity from studies in experimental animals.

The three listed vinyl halides have widespread industrial use, especially in the plastics industry, and the primary route of occupational exposure is inhalation. Numerous epidemiological studies of occupational exposure have shown that vinyl chloride causes cancer of the blood vessels of the liver (hepatic angiosarcoma) in humans (IARC 2008a,b,c). Hepatic angiosarcoma is a very rare type of cancer; its estimated incidence in the United States is only 25 cases per year (Molina and Hernandez 2003). In experimental animals, this type of cancer is usually referred to as hemangiosarcoma; all three listed vinyl halides cause hemangiosarcoma of the liver in experimental animals. No epidemiological studies of the carcinogenicity of vinyl bromide or vinyl fluoride have been identified. However, all three listed vinyl halides are metabolized to similar DNA-reactive intermediates (haloethylene oxide and haloacetaldehyde) via a human cytochrome P450 2E1–dependent pathway and cause genetic damage in vivo and in vitro. Furthermore, the DNA adducts formed are the same for all three of these vinyl halides, and the etheno adducts can cause DNA miscoding by modifying base-pairing sites (IARC 2008a,b,c). The fact that vinyl bromide, vinyl chloride, and vinyl fluoride all cause hemangiosarcoma of the liver in experimental animals and induce the formation of similar DNA adducts suggests a common mechanism of carcinogenicity for these three vinyl halides. 
14 
9781523108527