Carcinogens carbon tetrachloride

For the chlor-alkali industry, an emergency preparedness and response plan is mandatory for potential uncontrolled chlorine and other releases. Carbon tetrachloride is sometimes used to scrub nitrogen trichloride (formed in the process) and to maintain its levels below 4% to avoid fire and explosion. Substitutes for carbon tetrachloride may have to be used, as the use of carbon tetrachloride may be banned in the near future due to its carcinogenicity. 

Many very hazardous solvents, such as benzene and carbon tetrachloride, were widely used until the 1970s. The situation was very similar for the use of pesticides. Among the toxic pesticides that were still in wide use 20 years ago were chlorophenols, DDT, lindane, and arsenic salts, all of which are classified as human carcinogens as well as being acutely toxic. Fortunately, use of these kinds of very toxic chemicals is now limited in the industrialized world. However, because the number of chemicals used in various industries continues to increase, the risks of long-term health hazards due to long-term exposure to low concentrations of chemicals continues to be a problem in the workplace. 

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... 

Carbon tetrachloride, CCL, was a popular dry-cleaning agent until it was shown to be carcinogenic. It has a density of 1.589 g/cm3. What volume of carbon tetrachloride will contain a total of6.00 X 1025 molecules of... 

All Group 14/IV elements form liquid molecular tetrachlorides. The least stable is PbCl4, which decomposes to solid PbCl2 when it is warmed to about 50°C. Carbon tetrachloride, CC14 (tetrachloromethane), was widely used as an industrial solvent however, now that it is known to be carcinogenic, it is used primarily as the starting point for the manufacture of chlorofluorocarbons. Carbon tetrachloride is formed by the action of chlorine on methane ... 

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. 

Toxicology. Carbon tetrachloride causes central nervous system depression and severe damage to the liver and kidneys it is carcinogenic in experimental animals and has been classified as a potential human carcinogen. 

A number of animal studies suggest that hepatomas occur only after liver necrosis and fibrosis have occurred and, therefore, that carbon tetrachloride is not a direct liver carcinogen." One early study, however, found that liver necrosis and its associated chronic regenerative state probably were not necessary for tumor induction, although a correlation was found between the degree of liver necrosis and the incidence of hepatomas. "... 

The lARC has determined that there is sufficient evidence for carcinogenicity in animals, inadequate evidence for carcinogenicity in humans, and an overall evaluation that carbon tetrachloride is possibly carcinogenic to humans. " ... 

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for carbon tetrachloride is 5 ppm (31 mg/m ) with a shortterm excursion limit of 10 ppm (63mg/m ), an A3-animal carcinogen designation, and a notation for skin absorption. 

The filtrate is dried and slurried with carbon tetrachloride to separate the ricin by flotation. Use caution handling carbon tet as it is a suspected carcinogen and has toxic fumes. The ricin is skimmed off the top. Dry and grind carefully. 

Carbon tetrachloride is a poison and also a carcinogen. The acute toxicity... 

Summary of Carcinogenic Unit Risk Calculations for Oral Exposure to Carbon Tetrachloride s 2-4 Levels of Significant Exposure to Carbon Tetrachloride - Dermal 2-5 Genotoxicity of Carbon Tetrachloride In Vitro 2-6 Genotoxicity of Carbon Tetrachloride In Vivo... 

Levels of exposure associated with carcinogenic effects (Cancer Effect Levels, CELs) of carbon tetrachloride are indicated in Table 2-2 and Figure 2-2. Because cancer effects could occur at lower exposure levels. Figures 2-1 and 2-2 also show a range for the upper bound of estimated excess risks, ranging from a risk of 1 in 10,000 to 1 in 10,000,000 (10 to 10 as developed by EPA. 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have been made for carbon tetrachloride. An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given route of exposure. MRLs are based on noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

No studies were located regarding carcinogenicity in animals after inhalation exposure to carbon tetrachloride. 

TABLE 2-3. Summary of Carcinogenic Unit Risk Calculations for Oral Exposure to Carbon Tetrachloride... 

Cancer. There are a few reports of cancer in people who have been exposed to carbon tetrachloride, but these data per se are not adequate to show that carbon tetrachloride causes cancer in humans. However, there is convincing evidence from animal studies that oral exposure to carbon tetrachloride leads to hepatic tumors (see Section 2.2.1.8), which is supported by a number of other animal studies employing parenteral routes of exposure (Della Porta et al. 1961 Reuber and Glover 1967, 1970). Collectively, these data suggest that carbon tetrachloride is reasonably likely to be a human carcinogen. 

The DHHS has determined that carbon tetrachloride may reasonably be anticipated to be a carcinogen. lARC (lARC 1987) has classified carbon tetrachloride in Group 2B, possibly carcinogenic to humans, and ERA (IRIS 1993) has determined that carbon tetrachloride is a probable human carcinogen. 

As shown in Figure 2-4, there is a considerable body of data on the health effects of carbon tetrachloride in humans, especially following acute oral or inhalation exposures. Although many of the available reports lack quantitative information on exposure levels, the data are sufficient to derive approximate values for safe exposure levels. There is limited information on the effects of intermediate or chronic inhalation exposure in the workplace, but there are essentially no data on longer-term oral exposure of humans to carbon tetrachloride, most toxicity studies have focuses on the main systemic effects of obvious clinical significance (hepatotoxicity, renal toxicity, central nervous system depression). There are data on the effects of carbon tetrachloride on the immune system, but there are no reports that establish whether or not developmental, reproductive, genotoxic, or carcinogenic effects occur in humans exposed to carbon tetrachloride. 

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