Perchloroethylene, toxicity

EPA. 1986b. Extension of the public comment periods on notices of intent to list trichloroethylene and perchloroethylene as potentially toxic air contaminants. U.S. Environmental Protection Agency. Federal Register 51 9510. 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

Perchloroethylene (tetrachloroethylene) is a nonflammable solvent of low toxicity that dissolves and removes H blister and V nerve agents but does not neutralize them. NIOSH has recommended that this substance be treated as a potential human carcinogen. It does not work with G nerve agents. 

I now shall present a summary of an application of decision analysis to a specific chemical, perchloroethylene (PCE), a widely used dry cleaning solvent (also called tetrachloroethylene). Full details of this application are presented in an EPA report (5). Perchloroethylene was selected for us by the staff of the EPA Office of Toxic Substances as representative of chemicals on which EPA needed to make an unreasonable risk determination under TSCA. Our analysis was carried out as an exercise in methodology development and not to support any specific regulatory activities by EPA concerning perchloroethylene. 

Is the risk of cancer posed by perchloroethylene "unreasonable" under the language of TSCA No clear answer emerges from the illustrative analysis. Whether a risk is unreasonable is not a matter to be determined from scientific evidence on toxicity and exposure, but rather a determination that will hinge on judgment. We concluded from our calculations that the uncertainty in projected annual cancer incidence from PCE was nearly five orders of magnitude, and such large uncertanties in health impacts may be typical for many chemical agents. 

Alexander, H.C., McCarty, W.M., and Bartlett, E.A. Toxicity of perchloroethylene, trichloroethylene, 1,1,1-trichloroethane, and methylene chloride to fathead minnows, Bull. Environ. Contam. Toxicol, 20(3) 344-352, 1978. 

Environment and health-related problems are especially determined by health risks due to solvents, which result in damage to skin and the central nervons system (polyneuropathy, encephalopathy) in the case of chronic exposure. Some solvents are also classified as being carcinogenic (e.g. benzene, trichloroethylene) or are suspected of being carcinogenic (e.g. perchloroethylene) or reproduction-toxic (e.g. toluene). 

SOLVENTS. The following solvents should be considered for possible use trichloroethylene, ethylene dichloride, perchloroethylene, and carbon tetrachloride. The solvents may be purchased in tank-car lots since storage space is available. Note that some of these are on the toxic list. 

U.S. Environmental Protection Agency. 1992. Technology transfer network air toxics Web site. Tetrachloroethylene (perchloroethylene), hazard summary. Revised in lanuary 2000 (updated 2007). Washington, D.C. U.S. EPA. 

Some industrial solvents are found on the Proposition 65 Hst. As of January 1, 1993 (2), benzene, carbon tetrachloride, chloroform, methjlene chloride, 1,4-dioxane, 2-nitropropane, and perchloroethylene have been Hsted as substances known to the state of California to cause cancer. Ethji alcohol in alcohoHc beverages, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethjiene glycol monoethyl ether acetate, and toluene are Hsted as substances known to the state of California to cause reproductive toxicity. Because the Hst is being expanded periodically, it is necessary for a user of industrial solvents to maintain awareness of the Proposition 65 Hst. 

The removal of perchloroethylene solvents such as the very toxic trichloroethylene (TCE) from soil and water is a rather difficult problem [331]. A bench-scale study was conducted in TCE-contaminated sand columns. The following operation was tested. Foam obtained using the anionic surfactant Steol CS-330 was injected in a pulsed operation, after which artificial groundwater followed, and then foam again. The result was 75% of the initial TCE content. After the TCE-degrading bacterial strain ENV 435 had been added with the second pulse of foam, the result of the treatment was 95-99%. 

Abedin Z, Cook RC, Jr, Milberg RM. 1980. Cardiac toxicity of perchloroethylene (a dry cleaning agent). South Med 173 1081-1083. 

EPA. 1985a. Assessment of perchloroethylene as a potentially toxic air pollutant. U.S. Environmental Protection Agency. Code of Federal Regulations. 40CFR61. 

Hayes JR, Condie LW Jr, Borzelleca JF. 1986. The subchronic toxicity of tetrachloroelhylene (perchloroethylene) administered in the drinking water of rats. Fundam Appl Toxicol 7 119-125. 

Rampy LW, Quast JF, Balmer MF, et al. 1978. Results of a long-term inhalation toxicity study. Perchloroethylene in rats. Toxicology Research Laboratory, Health and Environmental Research, The Dow Chemical Company, Midland, Ml. Unpublished. 

Rao VR, Levy K, Lustik M. 1993. Logistic regression of inhalation toxicities of perchloroethylene— Application in noncancer risk assessment. Regulatory Toxicology and Pharmacology 18 233-247. 

Bis(3,4-dicarboxybenzoyl)phthalocyanines with M = Co(II) or Cu(II) have been covalently bound to linear polystyrene by a Friedel-Crafts reaction [130], The polymers contained 0.13 mmol g (12.4 wt.%) phthalocyanine moieties. The sensitivity of the polymers toward toxic gases were investigated by quartz balance transducers. The sensitivities are 6T0" m mL for NO2 and 2T0 m mL for chloroform and perchloroethylene, respectively. 52 (R = SO2CI, M = Fe) has been covalently bound to the amino groups of a cross-linked, hydrophilic polymer consisting of A/ -acryloyl-P-alanine-(aminoethyl-ene)-amide, A -acryloylpyrrolidine and 7V,A -bis(methacryloyl)-l,2-diamino-ethane as comonomers [131]. The polymer obtained, 52, contains 20 pmol phthalocyanine units per g. The catalytic oxidation of 2,4,6-trichlorophenol or 3,5-di-tert-butylcatechol in the presence of H2O2 or KHSO5 as oxidant has been studied. Around 80% of the trichlorophenol was catalytically oxidized within 2 h at pH 7. 

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