Pyrolysis products, carcinogenic

The involvement of tobacco smoke carcinogens in the aetiology of lung cancer is conclusively established, but the role of specific chemical carcinogens as inducers of colorectal cancer is much less clear. Mutagenic pyrolysis products derived from cooked food have come under suspicion as possible... 

Table IV. Mutagenic activities of mutagens isolated from pyrolysis products and typical carcinogens...

Carcinogenic activities of pyrolysis products were studied in vitro and in vivo. Trp-P-1, Trp-P-2 (35), and Glu-P-1 (36) induced malignantly transformed foci in the embryonic cells of cryopreserved Syrian golden hamsters. 

Other studies on coal were performed using pyrolysis, such as the measurement of the level of sulfur containing compounds in coal [27,28], or evaluation of polynuclear aromatic hydrocarbons (PAH) in coal [29]. The generation of PAH in coal pyrolysis is an important issue, as some of these compounds are known to have carcinogenic properties. A list of PAHs identified in coal pyrolysates is given in Table 14.2.2. The yield of PAH in coal pyrolysate depends to some extent on the coal type but mainly on the pyrolysis temperature. The variation of PAH levels as a function of temperature for several bituminous coals is shown in Figure 14.2.3. The yields of other pyrolysis products of coal were also shown to be temperature dependent [30]. 

M21. Manabe, S., Yanagisawa, H., Ishikawa, S., et al., Accumulation of 2-amino-6-methyldipyri-do[l,2-a 3, 2 d]imidazole and 2-aminodipyrido[l,2 fl 3, 2 d]imidazole, carcinogenic glutamic acid pyrolysis products, in plasma of patients with uremia. Cancer Res. 47, 6150-6155 (1987). 

Hosaka, S., Matsushima, T., Hirono, I., and Sugimura, T., Carcinogenic activity of 3-amino-l-methyl-5H-pyrido [4,3-b]indole (Trp-P-2), a pyrolysis product of tryptophan, Cancer Lett., 13, 23, 1981. 

Ishikawa, T., Takayama, S., Kitagawa, T., et al., In vivo experiments of trptophan pyrolysis products, in Naturally Occurring Carcinogens-Mutagens and Modulators of Carcinogenesis, Miller, E. C., Miller, I., Hirono, T., et al., Eds., University Park, Baltimore, MD, 1979, 159-167. 

Kanai, Y., Wada, O., and Manabe, S., Detection of carcinogenic glutamic acid pyrolysis products in cigarette smoke condensate. Carcinogenesis, 11, 1001-1003, 1990. 

Of the known carcinogenic pyrolysis products of the amino acids, so far only 2-amino-3-methylhnidazo(4,5-/)quinoline has been detected in trace amounts of 0.26 ng in the smoke of a Japanese filter cigarette [Yamashita et al. (4368)]. 

Apparently, Hoffmann and Hecht had overlooked not only the reports of the identification in CSC of several other known carcinogenic pyrolysis products of amino acids, for example, 2-amino-97/-pyrido[2,3-fc]indole (AaC) and 2-ami-no-3-methyl-97/-pyrido[2,3-fc]indole (MeAaC) (4388) or... 

Etliylene production involves liigh temperatures (1500°F) in tlie pyrolysis section and cryogenic temperatures in tlie purification section. The feedstocks, products, and by-products of pyrolysis are flaimnable and pose severe fire liazards. Benzene, wliich is produced in small amounts as a byproduct, is a known carcinogen. Table 21.7.1 summarizes some of the properties of etliane (feedstock) and tlie product gases. Figure 21.7.1 shows a simplified schematic diagram of the pyrolysis and waste heat recovery section on an etliylene plant. 

Methods were described for HPLC determination of the mutagenic and carcinogenic a-carbolines (56,57), y-carbolines (58,59)155 160, and other products of amino acid pyrolysis found in cigarette smoke, diesel exhaust and cooked foods and phenazines (60, 61) present as impurities of certain pesticides161. These compounds were also determined in human plasma, urine and bile161,162. 

Presently about 20 different mutagenic and/or carcinogenic heterocyclic amines (HAs) have been isolated from various heat-processed foods. One class of these HAs is formed by pyrolysis of proteins or some amino acids. These HAs are amino-carbolines (Figure 13.7), and have been identified in grilled, broiled, baked, and fried meat and fish products, in meat sauces and bouillons, as well as in pyrolyzed proteins, glutamate, lysine, phenylalanine, tryptophan, ornithine, and creatine. 

Both NAT1 and NAT2 N-acetylate benzidine and O-acetylate the N-hydroxy metabolite. Because NAT2 and, to a lesser extent, NAT1 both show variation in the human population, this influences susceptibility to the carcinogenic effects of arylamines such as benzidine. With other aromatic amines, such as the heterocyclic amines found as food pyrolysis degradation products, N-acetylation is not favored, N-oxidation being the primary route followed by O-acetylation. This seems to take place in the colon. 

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