Benzopyrenes, carcinogenicity

Finally it is likely that attention will be focused on emissions of polynuclear aromatics (PNA) in diesel fuels. Currently the analytical techniques for these materials in exhaust systems are not very accurate and will need appreciable improvement. In conventional diesel fuels, emissions of PNA thought to be carcinogenic do not exceed however, a few micrograms per km, that is a car will have to be driven for several years and cover at least 100,000 km to emit one gram of benzopyrene for example These already very low levels can be divided by four if deeply hydrotreated diesel fuels are used. 

Polycychc aromatic hydrocarbons (PAHs) are carcinogens produced by the thermal breakdown of organic materials. These are widely distributed in both food and the environment, and are some of the principal carcinogens in cigarette tar and air pollution. Of over 20 PAHs isolated, benzopyrene and quinoline compounds are the most commonly encountered in foods, particularly those which are broiled or fried (111). Shellfish living in petroleum contaminated waters may also contain PAHs (112). 

Many aromatic compounds, such as benzopyrene, are carcinogenic because —... 

Dean, J.H., et al., Selective immunosuppression resulting from exposure to the carcinogenic congener of benzopyrene in B6C3F1 mice, Clin. Exp. Immunol., 52, 199, 1983. 

Cigarette smoke contains a minute amount of polonium, along with many other carcinogenic chemicals, many of which can cause lung cancer. Over one hundred trace elements and compounds have been identified in cigarette smoke besides polonium. Some examples are nicotine, cresol, carbon monoxide, pyridine, and the carcinogenic compound benzopyrene. 

Hydroxylation may also take place at nitrogen atoms, resulting in hydroxyl-amines (e.g., acetaminophen). Benzene, polycyclic aromatic compounds (e.g., benzopyrene), and unsaturated cyclic carbohydrates can be converted by mono-oxygenases to epoxides, highly reactive electrophiles that are hepato-toxic and possibly carcinogenic. 

Edes, T. E., Gysbers, D. G., Buckley, C. S., and Thornton, W. H., Jr. (1991). Exposure to the carcinogen benzopyrene depletes tissue vitamin A Beta-carotene prevents depletion. 

Borneff I, Engelhardt K, Griem W, et al. 1968. Carcinogenic substances in water and soil. XXII. Mouse drinking study with 3,4-benzopyrene and potassium chromate. Arch Hyg 152 45-53. 

Substitution of a methyl group (electron donor) at a position of high free valency increases the action (the 10-methyl derivative is active). In 1, 2, 5, 6-dibenzanthracene, one of the first known carcinogenic hydrocarbons, there are two bonds, 3—4 and 7—8, which both possess a high TT-electron density. The difference between the inactive 1, 2-benzopyrene and the active 3, 4-benzopyrene from coal tar would be due to the fact that the former possesses one K region, the 6—7 bond, the latter, however, has also the 1—2 bond as such. 

SAFETY PROFILE Confirmed carcinogen with experimental carcinogenic, neoplastigenic, and tumorigenic data. A poison via subcutaneous, intraperitoneal, and intrarenal routes. Experimental teratogenic and reproductive effects. Human mutation data reported. A skin irritant. A common air contaminant of water, food, and smoke. When heated to decomposition it emits acrid smoke and fumes. See other benzopyrenes. 

One of the many enzyme functions of hepatocytes is the hydroxyla-tion of various drugs (aminopyrine, codeine, hexobarbital, etc.) cyclic compounds, and carcinogenic hydrocarbons (benzopyrenes, benzanthracene), steroid hormones (testosterone), fatty acids (lauric acid), etc. All these functions are carried out by an organized multienzyme system in the endoplasmic reticulum membrane (Gillette and Gram, 1969). The endoplasmic reticulum can be obtained by differential centrifugation in the form of membranous vesicles called microsomes. 

According to Hall (80a) adsorption on silica-alumina in the presence of isoctane, displays for pyrene bands at 462 and 467, and for 3,4-benzopyrene, the carcinogenic hydrocarbon, bands at 520 and 782 mju., corresponding evidently to similar cation radicals and to carbonium cations. It was presumed that these latter are not of the protonated form, but represent a positively charged configuration, covalently bound to an electrophilic (Al) site, like that schematically represented in Section VD for chemisorbed olefins. 

The fact that the fixation maximum is of the same order of magnitude for benzopyrene (/ = 4000, J — 1.6 x 10 8) and for 1, 2—6, 4-dibenzanthracene (/ = 6xl0-u, J — 2.5 x 10s) seems to show that the fixation takes place both by bonds and by a pair of opposite atoms. It would thus not be very surprising if the correlation between the fixation maximum and carcinogenic activity is not very good. 

Benzopyrene (shown below) is found in tobacco smoke, smokestack effluents, charcoal-grilled meat, and automobile exhaust. It is one of the strongest carcinogens known. It is estimated that a wide variety of all cancers are caused by chemical carcinogens, such as PAH, in the environment. 

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. 

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