Polychlorinated biphenyls carcinogenicity

Liver cancer can also be a consequence of exposure to hepatotoxic chemicals. Natural hepatocarcinogens include fungal aflatoxins. Synthetic hepato-carcinogens include nitrosoamines, certain chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), chloroform, carbon tetrachloride, dimethyl-benzanthracene, and vinyl chloride.Table 5.15 lists the chemical compounds that induce liver cancer or cirrhosis in experimental animals or... 

Polychlorinated Biphenyls. Polychlorinated biphenyls (PCBs) are carcinogenic and adversely... 

Hayes, M.A. 1987. Carcinogenic and mutagenic effects of PCBs. Pages 77-95 in S. Safe (ed.). Polychlorinated Biphenyls (PCBs) Mammalian and Environmental Toxicology. Environ. Toxin Ser. 1. Springer-Verlag, New York. 

The applicability of using these interdisciplinary approaches, which include incorporation of various physical and chemical properties of the pollutants, QSARs/QSPRs and multicomponent joint action modeling are discussed and evaluated using a group of toxic and carcinogenic pollutants, i. e., polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). 

This includes bioremediation cases of contaminated sites with several toxic and carcinogenic pollutants, such as petroleum hydrocarbons, PAHs, dichlorobenzene, chlorinated hydrocarbons, carbon tetrachloride, Dicamba, methyl bromide, trinitrotoluene, silicon-based organic compounds, dioxins, alkyl-phenol polyethoxylates, nonylphenol ethoxylates, and polychlorinated biphenyls. The following is a brief summary of each case. 

Polychlorinated biphenyls (PCBs) are a family of compounds that were used extensively in electrical equipment, such as transformers, because of their insulating and heat transferring qualities. They are suspected human carcinogens and have been linked to liver, kidney, and other health problems. It is known that PCBs can be transported by air, and this is thought to be one of the major ways in which they circulate around the world, explaining why they are found in the Arctic and Antarctic. Indian women dwelling on Cornwall Island located in the Canadian portion of the reservation have elevated levels of toxic PCBs in their breast mUk. The PCB contamination does not appear to come from fish, but from air the women breathe every day [45]. 

Mayes BA, McConnell EE, Neal BH, et al Comparative carcinogenicity in Sprague-Dawley rats of the polychlorinated biphenyl mixtures Aroclors 1016, 1242, 1254, and 1260. Toxicol Sci M y.62-16, 1998... 

The work described here was performed in a laboratory which had been specially modified and equipped to handle chemical carcinogens (10). Strict care was taken to avoid worker exposure to hazardous chemicals during the course of these studies. Reagent grade chemicals used for this work were 1,2-dichloroethane (Alfa Products, Danvers, MA) 1,1,1-trichloroethane (Matheson, Coleman Bell, Norwood, OH) 1,1,2-trichloroethane (J.T. Baker Chemical Co., Phillipsburg, NJ) n-heptane and n-hexane (Burdick Si Jackson Laboratories, Inc., Muskegon, MI). Also,used was a polychlorinated biphenyl whose chemical composition as determined... 

This type of induction is caused by a large group of environmental chemicals, both natural such as plant indoles and man made such as polycyclic hydrocarbons. Examples include benzo [a]pyrene, benzo[a]anthracene, 3-methylcholanthrene, p-napthoflavone, polychlorinated biphenyls and benzo-p-dioxins, and dibenzofurans. Many of these compounds are of interest as they are carcinogenic. 

Chlorinated aromatic compounds are commonly found as contaminants in environmental soil samples. For example, chlorobenzenes have been listed as priority pollutants and can be found in various matrixes such as water, soils, sediments and sewage sludges. Polychlorinated biphenyls are probable human carcinogens but have been applied in large doses in various industrial products. Analysis of these compounds in solid matrixes, such as soils and sediments, requires several steps. 

WHO (World Health Organization) 1978. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans. Polychlorinated biphenyls and polybromin-ated biphenyls. 18, WHO, Geneva, Switzerland. 

A number of environmental contaminants (e.g., some organo-chlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons) cause cancer in laboratory animals. The committee found no epidemiological evidence to suggest that these compounds individually make a major contribution to the risk of cancer in humans. However, the possibility that they may act synergistically and may thereby create a greater carcinogenic risk cannot be excluded. 

Table II. Modification of 2-FA-induced mutagenesis in S. typhimurium TA98 by retinol utilizing carcinogen activation sources prepared from rats not treated with polychlorinated biphenyls...

Although several peroxidase enzymes obtained from plant, animal, and microbial sources have been investigated for their ability to catalyze the removal of aromatic compounds from wastewaters, the majority of studies have focused on using HRP. In particular, it has been shown HRP can transform phenol, chlorophenols, methoxyphenols, methylphenols, amino-phenols, resorcinols, and various binuclear phenols [7], HRP was also used for the treatment of contaminants including anilines, hydroxyquinoline, and arylamine carcinogens such as benzidines and naphthylamines [7,8]. In addition, it has been shown that HRP has the ability to induce the formation of mixed polymers resulting in the removal of some compounds that are either poorly acted upon or not directly acted upon by peroxidase [7], This phenomenon, termed coprecipitation or copolymerization, has important practical implications for wastewaters that usually contain many different pollutants. This principle was demonstrated when it was observed that polychlorinated biphenyls (PCBs) could be removed from solution through coprecipitation with phenols [20]. However, this particular application of HRP does not appear to have been pursued in any subsequent research. 

Polychlorinated biphenyls (PCBs) have been used in the manufacturing of electrical transformers. They are highly persistent in the environment. Rodent tests have suggested that PCBs are carcinogenic and the U.S. government strongly regulates their production (Shelton, 1989). 

However, the use of perchlorates in pyrotechnic formulations is discouraged due to the supposed toxicity of this chemical which has been linked to causing thyroid disorders. Furthermore, the combustion of polychlorinated organic materials such as poly(vinyl) chloride has been shown to produce polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). These polychlorinated chemicals are highly toxic and are potent carcinogens. Therefore, the removal of perchlorates and chlorinated organic materials in pyrotechnic formulations would eliminate the formation of these aforementioned pollutants. 

Iverson F, Grant DL (1991), in IARC Scientific Publication No. 108, Environmental Carcinogens Methods of Analysis and Exposure Measurement, Vol. 11 Polychlorinated Dioxins and Dibenzofurans", Toxicology of the polychlorinated biphenyls, dibenzofurans and dibenzodio-xins", p. 5-21, Eds. Rappe C, Buser HR, Dodet B, O Neill IK International Agency for Research on Cancer, Lyon... 

Lewis, R.G. (1993). Determination of pesticides and polychlorinated biphenyls in indoor air by gas chromatography. Method 24, in Environmental Carcinogens Methods for Analysis and Exposure Measurement, Vol. 12, B. Seifert, H. van de Wiel, B. Dodet and I. O Neill (Ms), International Agency for Research on Cancer, Lyon, France, pp. 353-376. 

SAFETY PROFILE Suspected human carcinogen. Moderately toxic by ingestion and skin contact. Experimental reproductive effects. When heated to decomposition it emits toxic fumes of Cl". Used in heat transfer, hydraulic fluids, lubricants, and insecticides. See also POLYCHLORINATED BIPHENYLS. 

---