Benzo pyrenes carcinogenicity

Shimizu Y, Nakatsum Y, Ichinose M, Takahashi Y, Kume H, Mimura J, Fujii-Kuriyama Y, Ishikawa T (2000) Benzo[a]pyrene carcinogenicity is lost in mice lacking the aryl hydrocarhon receptor. Proc Natl Acad Sci USA 97 779-782... 

Benzo[/ ]pyrene is designated an A2-sus-pected human carcinogen by ACGIH and has no assigned threshold limit value. 

In skin-painting studies in mice, catechol increased the carcinogenic effects of benzo[< ]pyrene (B(skin tumors was compared with that obtained from groups treated with B([Pg.129]

Clearly, a sound evaluation of the total mutagenic/carcinogenic potencies of a complex mixture of POM emissions (e.g., diesel exhaust) should include not only the PEFs of the primary particle- and vapor-phase PAHs and PACs but also those of the mutagens formed in atmospheric reactions of precursor PAHs (see, for example, Arey et al. (1992), Lewtas (1993b), Atkinson and Arey (1994), Nielsen et al. (1996), Arey (1998a), and Section F). For examples of such formal scientific health risk assessments prepared by the State of California Air Resources Board and Office of Environmental Health Hazard Assessment, see Benzo[ ]pyrene as a Toxic Air Contaminant (CARB, 1994) and Identification of Diesel Exhaust as a Toxic Air Contaminant (CARB, 1998). 

Syn dihydrodiol epoxide adducts formed in mouse skin treated with benzo[ ]pyrene constitute only about 12% of the total binding (36) and dihydrodiol epoxide deoxyadenosine adducts account for even less (2 to 3%) of the total (37,38). DMBA is approximately 20 times more potent a carcinogen than BP and this difference cannot be explained by the 2- to 4-fold difference in overall binding to DNA by these two carcinogens in mouse skin (35). Thus, these more subtle differences in DNA reaction products, i.e. the difference in reaction of syn-stereoisomer with DNA or in the modification of deoxyadenosine residues, might account for the greater tumor-initiating potential of DMBA. 

Transgenic mice may add to our understanding of the role of XME polymorphisms in potentiation or protection from xenobiotic toxicity. For example, mice lacking the AhR are immune to benzo(a)pyrene carcinogenicity, presumably due to an inability to induce CYPlAl expression. 

It is postulated that this ultimate carcinogen reacts covalently with nucleic acids, producing nucleic acid adducts. It has been demonstrated that benzo[a]pyrene reacts covalently with nucleic acids in vitro, provided that the microsomal enzyme systems necessary for activation are present, and also in whole cell systems. The 7,8-dihydrodiol metabolite of benzo[ ]pyrene binds more extensively to DNA after microsomal enzyme activation than does benzo[a]pyrene or other benzo[a]pyrene metabolites, and the nucleoside adducts formed from the 7,8-dihydrodiol of benzo[tf]pyrene are similar to those obtained from cells in culture exposed to benzo[ ]pyrene itself. Furthermore, the synthetic 7,8-diol-9,10-epoxides of benzo[a]pyrene are highly mutagenic in mammalian as well as in bacterial cells. 

It shows DNA damaged by the environmental chemical carcinogen benzo[ ]pyrene in the active site of the human DNA bypass polymerase k. 

Being interested here in the volatile components of coffee aroma, we shall arbitrarily limit the list of the aromatic hydrocarbons to tricyclic structures. The higher fused polycyclic hydrocarbons (fluoranthene [206-44-0], pyrene [129-00-0], chrysene [218-01-9], benz[ ]anthracene (1,2-benzanthracene) [56-55-3], benz[< ]acephenanthrylene (3,4-benzofluoranthene) [205-99-2], benzo[ ]pyrene (3,4-benzopyrene, 3,4-BP) [50-32-8], benzo[e]pyrene (1,2-benzopyrene) [192-97-2], perylene [198-55-0], benzo[g,/i,/]perylene (1,12-benzopyrene) [191-24-2], and dibenz[ ,//]anthracene (1,2,5,6-dibenzanthracene) [53-70-3]) cannot be considered as a part of the aroma. However, as some of these, specially benzo[o pyrene, are known for carcinogenic properties, they have been particularly analyzed in food subject to roasting or smoke-curing. 

Fig. 1. Structures of benzo[<2]pyrene, 3-methylcholanthrene and dioxin. Benzo[<2]-pyrene and 3-methylcholanthrene are PAH compounds, but dioxin is not. Benzo [ ] pyrene is converted to the ultimate carcinogen BPDE by CyplAl.

Shimizu, Y, Nakatsuru, Y, Ichinose, M., Takahashi, Y, Kume, H., Mimura, J., Fujli-Kuriyama, Y, and Ishikawa, T. (2000). Benzo[ a] pyrene carcinogenicity is lost in mice lacking the arylhydrocarbon receptor. Proc. Natl. Acad. Sci. USA 97, 779-782. 

The best known carcinogenic compound — benzo [ ] pyrene — is used as leading substance out of about 250 different compounds which belong to the PAH... 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

A large number of polycyclic aromatic hydrocarbons are known Many have been synthesized m the laboratory and several of the others are products of com bustion Benzo[a]pyrene for example is present m tobacco smoke contaminates food cooked on barbecue grills and collects m the soot of chimneys Benzo[a]pyrene is a carcinogen (a cancer causing substance) It is converted m the liver to an epoxy diol that can induce mutations leading to the uncontrolled growth of certain cells... 

Many naturally occurring substances are epoxides You have seen two examples of such compounds already m disparlure the sex attractant of the gypsy moth (Section 6 18) and m the carcinogenic epoxydiol formed from benzo[a]pyrene (Section 118) In most cases epoxides are biosynthesized by the enzyme catalyzed transfer of one of the oxy gen atoms of an O2 molecule to an alkene Because only one of the atoms of O2 is trans ferred to the substrate the enzymes that catalyze such transfers are classified as monooxy genases A biological reducing agent usually the coenzyme NADH (Section 15 11) is required as well... 

Polycyclic aromatic hydrocarbons have been classified as human carcinogens because they induce cancers in experimental animals and because smoking and exposure to mixtures of chemicals containing polycyclic aromatic hydrocarbons in the workplace increase the risk of lung cancer in exposed individuals. In experimental animals, benzo(a)pyrene induces cancer in different organs depending on the route of administration.Furthermore, exposure to polycyclic aromatic hydrocarbons commonly occurs in occupations related to traffic (use of diesel engines in transportation and railways). 

---