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Risk Characterization
Published in Ted W. Simon, Environmental Risk Assessment, 2019
The chlorine used to produce toxaphene was produced at a nearby chlor-alkali plant. Both polychlorinated biphenyls and mercury are used in the electrolytic cells needed for the chlor-alkali process. Toxaphene, Aroclor 1268, a high-molecular weight polychlorinated biphenyl (PCB) mixture, and mercury were released during chlorine production and toxaphene manufacture. All three chemicals bioaccumulate in fish, and this example demonstrates the risk assessment of consumption of fish contaminated with these three chemicals. The last number in the Aroclor designation represents the weight percentage of chlorine in the PCB mixture. The most highly chlorinated mixture is Aroclor 1268, with 68% chlorine by weight.
In Vitro Effect of Bile Acids
Published in Herman Autrup, Gary M. Williams, Experimental Colon Carcinogenesis, 2019
Silverman and Andrews52 attempted to reproduce the promoting effect of bile acids on chemical carcinogens administered to the colon of rats using the Ames Salmonella-Mammalian Microsome Mutagenicity test. After testing some 30 bile acids with the various tester strains, with and without a phenobarbital-stimulated 9000 × g postmitochondrial supernatant fraction (S9), the authors found none of the bile acids to be mutagenic. Using suboptimal levels of two model carcinogens, MNNG (N-methyl-N′-nitro-N-nitrosoguanidine) and 2-aminoanthracene, lithocholic acid was found to enhance the mutagenicity of the aromatic amine only. In addition, lithocholic acid derivatives including the glycine and taurine conjugates as well as 3-keto-5β-cholanic acid enhanced the mutagenicity of 2-aminoanthracene when coincubated with the carcinogen. When an Aroclor-induced S9 preparation was used, no enhancement effects were observed. The different mutagen-enhancing activities of the bile acids with various S9 preparations are shown in Figure 2.
Percutaneous Absorption of Hazardous Substances from Soil and Water
Published in Francis N. Marzulli, Howard I. Maibach, Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Ronald C. Wester, Howard I. Maibach
Table 5 gives the in vitro and in vivo percutaneous absorption of polychlorinated biphenyl (PCBs) (Wester et al., 1993a). As with the other organic chemicals with high log/3, receptor fluid accumulation in vitro was essentially nil. In vitro, PCB showed some accumulation in skin. In vivo, PCB percutaneous absorption for both aroclor 1242 and 1254 was (a) high, ranging from 14 to 21% and (b) generally independent of formulation vehicle. Thus PCBs have a strong affinity for skin and are relatively easily absorbed into and through skin.
A contemporary review of electronic waste through the lens of inhalation toxicology
Published in Inhalation Toxicology, 2021
Oyemwenosa N. Avenbuan, Gabriella Y. Meltzer, Christina Awada, Amna Raja, Andrij Holian, Judith T. Zelikoff
In vivo animal studies have shown that exposure to certain PCBs at high concentrations produce adverse neurodevelopmental, immunological, endocrine, and reproductive effects, as well as cancer in some cases (Wang et al. 2019). In a study by Brown et al. (2007), male and female Sprague-Dawley rats exposed via the diet to PCB Aroclor concentrations ranging from 25 to 200 ppm for 24 months, demonstrated sex-/Aroclor-dependent increases in hepatic tumors compared to controls. The hepato-tumorigenesis was associated with tissue accumulations of PCBs and dioxin equivalents and increased expression of cell proliferation and proliferating cell nuclear antigen (Brown et al. 2007). PCBs can also act as endocrine-disrupting chemicals (EDCs). In one study, four weekly 50 mg/kg doses of non-coplanar PCB153 were administered to C57BL/6 male mice. These exposures resulted in a significant decrease in plasma and liver tissue concentrations of retinyl esters, retinol, and all-trans-retinoic acid (atRA). This study suggests that disruption of retinoid homeostasis is caused by PCB153-induced activation of the constitutive androstane receptor (CAR), which adds to the obesogenic properties of PCBs (Shmarakov et al. 2019).
Concentration dependence of human and mouse aryl hydrocarbon receptor responsiveness to polychlorinated biphenyl exposures: Implications for aroclor mixtures
Published in Xenobiotica, 2019
Hongxue Shi, Josiah E. Hardesty, Jian Jin, Kimberly Z. Head, K. Cameron Falkner, Matthew C. Cave, Russell Allen Prough
PCBs are polyhalogenated aromatic hydrocarbons and consist of up to 10 chlorine atoms attached to a biphenyl ring. PCBs were manufactured as mixtures (US tradename Aroclor) and sold by the percentage of chlorine in the mix. For example, Aroclor 1254 is 54% chlorine by mass, while Aroclor 1260 is 60% chlorinated. Of the 209 theoretical PCB congeners, approximately 130 were present in commercial PCB mixtures. PCB mixtures were used in a variety of industrial applications, such as insulating agents for electrical transformers. Approximately 1.3 million tons were produced worldwide before PCBs were banned (Ockenden et al., 2003). The primary routes of human PCB exposure are ingestion of contaminated food (Schecter et al., 2003) or breast milk, and inhalation of contaminated air (Ampleman et al., 2015). PCB metabolism varies considerably with low molecular weight PCBs being metabolized at a higher rate than the more heavily chlorinated PCBs. This leads to bioaccumulation patterns in adipose that greatly favor retention of the more highly chlorinated congeners being similar to those present in Aroclor 1260. However, there is an important exception. Aroclor 1260 is not believed to contain significant amounts of DL PCBs (Battelle Memorial Institute, 2012; Wahlang et al., 2014a; Wahlang et al., 2014b).
Impact of selenium status on Aroclor 1254-induced DNA damage in sperm and different tissues of rats
Published in Toxicology Mechanisms and Methods, 2018
Sevtap Aydin, Pinar Erkekoglu, Nurşen Başaran, Belma Kocer-Gumusel
Oxidative stress is suggested to induce oxidative DNA damage, including DNA base damages which can be detected by comet assay. Comet assay is a useful, versatile, easy, sensitive and low cost technique in detecting the DNA damage. It can be applied to wide range of cells, including sperm (Balasubramanyam et al. 2010). To our knowledge, this is the first study that uses Comet assay to show the effects of selenium status in Aroclor 1254-induced multi-organ toxicity. Currently, we have observed that Se deficiency alone can induce DNA damage, particularly in brain and sperm. Aroclor 1254 increased DNA damage in blood, liver, kidney, brain and sperm as evidenced by significant increases in DNA tail intensity, DNA tail moment and DNA tail migration (Figures 1–5). Se supplementation ameliorated the toxic effects of Aroclor 1254 in blood, liver, kidney and brain (Erkekoglu et al. 2012; Erkekoglu et al. 2015). Moreover, Se protected the sperm against the DNA damage-induced by this particular PCB congener. Se deficiency, on the other hand, aggravated Aroclor 1254’s toxicity in all of the organs as well as in sperm. Previously, we have shown that Se is found in higher concentrations in kidney compared to other organs. This might be the reason why Se supplementation was highly protective in kidney against Aroclor 1254 toxicity compared to other organs. Besides, in sperm, Se supplementation was also highly protective against toxic effects of Aroclor 1254 and almost prevented all of DNA-damaging effects of this particular PCB mixture.