BENZPYRENE

From Big Medical Encyclopedia

BENZPYRENE [3,4 benzpyrene, benz (and) pyrene, benzapiren) — one of the most strong cancerogenic connections. Polycyclic aromatic hydrocarbon, C 20 H 12  :

Molecular weight — 252,30; t°pl 176,5 °; t°kip 310 °. I bury the pale yellow substance crystallizing in the form of needles or plates soluble in benzene, acetone, ether, in oils and other organic solvents; low solubility in water (0,24 µmol on 1 l). In a range of fluorescence of B. has three strips with maxima at 418, 430 and 458 nanometers. Enters substitution reaction, rather easily is oxidized before formation of quinones, and then carboxylic acids.

The laboratory B. receives from pyrene or symmetric hexahydropyrene and anhydride amber to - you. At high temperatures from aliphatic and simple aromatic hydrocarbons B. it is synthesized by reaction of free radicals. Primary radicals are formed by a gap carbon-hydrogen or carbon carbon bonds of initial hydrocarbons (the first phase of process). In the second phase from primary radicals there is B.'s synthesis by gradual and consecutive connection of chains and dehydrogenation.

B. is one of the most widespread carcinogenic substances in the Wednesday surrounding the person. B. in the industry is educated occurs at high-temperature heat treatment processes of organic raw materials (distillation, coking) and burning in conditions under which products of incomplete combustion appear. B. it is found in many products of the industry at the enterprises for processing of black coal, oil shales, oil, at the black plants, the installations producing heating gases etc., and also there some of products of these productions are applied. It is possible to explain with B.'s action emergence of a professional carcinoma cutaneum at chimney sweeps, parafinshchik and other workers whose skin was exposed to long pollution by pitches, and also cases of lung cancer at workers of the gas industry. Cancerogenic action of B. is explained by its interaction with proteins nucleic acids causing the disturbances leading to transformation of normal cells in tumoral. The mechanism of action is up to the end not opened.

One of powerful sources of emission of B. in the atmosphere are internal combustion engines — significant amounts find it in composition of exhaust gases of motor transport and airplanes. B. it is possible to find in a polluted air of atmospheric dust, in the soil, reservoirs, and also in various washed-up foodstuff and tobacco smoke: it is found in tissues of lungs of the person, bronchial limf, nodes, in a secret of sebaceous glands and urine. It is possible to tell that B. meets everywhere where it is necessary to deal with smoke! or its products. In a certain communication with it it is possible to put increase in cancer cases of lungs at residents of big cities and at smokers of cigarettes.

Cancerogenic properties B. began to be studied widely in experiments after 1933 when it was for the first time allocated from coal tar, and then is synthesized from pyrene. At hypodermic introduction to mice and rats on 1 — 2 mg of B. in oil of sarcoma arise in 4 — 5 months; during the greasing of skin by it (0,5% solution in benzene) in 2 — 3 months there are papillomas, and through 4 — 5 months — honor cancer at 100% of animals. B.'s introduction directly to fabric of various bodies of animals also causes malignant tumors: papillomas and cancer of a prestomach, planocellular lung cancer, cancer of a uterus, a tumor of mammary glands etc. Krom of new growths on site of primary application, B. causes adenomatous tumors of lungs in a large number of mice.

B.'s exchange in an organism is carried out as reaction of a detoxication in a liver of ways of a hydroxylation with education 3 hydroxybenzpyrenes, 3,6 benzpyrenequinones, etc. End products of exchange of B. are allocated with bile, and then with a stake, partially with urine, hl. obr. in the form of pair connections with sulfuric and glucuronic acids. Only 1% of B.'s dose which is originally entered into an organism is removed in not changed look. During the studying of dynamics of emergence of metabolites in an hour after B.'s introduction, marked on carbon (With 14 ), in bile the 6-oxybenzpyrene-glucuronide, a Z-oksibenzpiren-glyukuronid, diioksibenzpiren-glucuronides and some other the unstable conjugated connections is found. In 24 hours after introduction to blood of a mouse of B., marked on carbon (With 14 ), 2/3 entered doses of radioactivity are revealed in Calais and 1/6 in urine. Further marked carbon within several more days can be found in a liver, bile, fatty tissue, Calais and urine. In expired air radioactivity is not found. Speed of removal of B. and products of its exchange from an organism of animals depends on a way of introduction, solvent and a dose of the entered carcinogen. So, at intraperitoneal introduction of B. in fatty solvent carcinogen is removed from an organism of a mouse by 15 times quicker, than at hypodermic introduction. At hypodermic introduction of B. in fatty solvent, in a water emulsion and in proteinaceous solvent B. entered with proteinaceous solvent, most slowly — in fatty solvent is most quicker removed. At intravenous administration of B. character of solvent affects the speed of removal least. At increase in a dose of the entered B. there is a proportional increase in its removal from an organism. However there is a threshold of a dosage, after achievement to-rogo further increase in allocation of metabolites does not occur.

In process of oxidation of an initial molecule B. in the course of metabolism carcinogenic activity decreases (oxyderivatives were less active). Patterns of metabolism of B. were studied not only in an organism, but also in culture of fabrics. They take place and at degradation of this substance in the environment, e.g. in the soil, drain waters, ground deposits etc. This process of bioscrubbling is carried out by a bacterial flora.

The technique of definition of B. and other polycyclic aromatic hydrocarbons applied in the USSR and abroad includes several stages.

1. Extraction of resinous substances, hl. obr. benzene.

2. Fractionation on a column with alumina.

3. B.'s identification, edges is most often made by the most sensitive spectral method. At the same time use both ranges of fluorescence, and absorption spectrums. In the frozen solutions of normal paraffinic hydrocarbons ranges of fluorescence of B. and other polycyclic aromatic hydrocarbons consist of a large number of thin and accurate lines. Such «quasiline» ranges have the expressed identity (E. V. Shpolsky, etc., 1952). Use of effect of Shpolsky considerably increases test-sensitivity of definition of B. (to 0,001 mkg).

4. For quantitative definition use a method of additives, or a method of internal control. The applied method is highly selective and allows to define B. in mixes of the most complex structure.

Development and use of thin and exact methods of definition of B. in the environment and in a human body created premises for preventive actions: detection of sources of emission of B., introduction of technological improvements (improvement of burning) to production (especially coke-chemical and oil industry), and also to a design and operation of internal combustion engines, rational town planning, personal hygiene. Firmly established dependence of cancerogenic effect of B.'s dose allowed on the basis of pilot studies, epidemiological observations, and also studying of level of this substance in the environment to establish maximum allowable concentration of B. in air of the inhabited places in number of 0,1 mkg / 100 to m 3 and 15 mkg / 100 m 3 in air of a working zone.

See also Oncogenous substances , Pitches .

Bibliography:

L. M Sabbath. Methods of studying of a blastomogennost of chemicals, M., 1970; it, About circulation of carcinogens in the environment, M., 1973; Badger G. M of Mode of formation of carcinogen es in human environment, Nat. Cancer Inst Monogr., jsft 2, p. 1, 1962.

AA. E. Smetanin, L. M. Shabad.

Яндекс.Метрика