<P> BaP's metabolites are mutagenic and highly carcinogenic, and it is listed as a Group 1 carcinogen by the IARC . Chemical agents and related occupations, Volume 100F, A review of Human Carcinogens, IARC Monographs, Lyon France 2012 In June 2016, BaP was added as benzo (def) chrysene to the REACH Candidate List of Substances of very high concern for Authorisation . </P> <P> Numerous studies since the 1970s have documented links between BaP and cancers . It has been more difficult to link cancers to specific BaP sources, especially in humans, and difficult to quantify risks posed by various methods of exposure (inhalation or ingestion). A link between vitamin A deficiency and emphysema in smokers was described in 2005 to be due to BaP, which induces vitamin A deficiency in rats . </P> <P> A 1996 study provided molecular evidence linking components in tobacco smoke to lung cancer . BaP was shown to cause genetic damage in lung cells that was identical to the damage observed in the DNA of most malignant lung tumours . </P> <P> Regular consumption of cooked meats has been epidemiologically associated with increased levels of colon cancer (although this in itself does not prove carcinogenicity), A 2005 NCI study found an increased risk of colorectal adenomas was associated with BaP intake, and more strongly with BaP intake from all foods . However, the foods themselves are not necessarily carcinogenic, even if they contain trace amounts of carcinogens, because the gastrointestinal tract protects itself against carcinomas by shedding its outer layer continuously . Furthermore, detoxification enzymes, such as cytochromes P450 have increased activities in the gut for protection from food - borne toxins . Thus, in most cases, small amounts of BaP are metabolized prior to being passed into the blood . The lungs are not protected in either of these manners . </P>

Sources of benzo a pyrene in the environment