Trichloroethylene
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TRICHLOROETHYLENE Trichloroethylene was considered by previous IARC Working Groups in 1979, 1987, and 1995 (IARC, 1979, 1987, 1995). New data have since become available, and these have been taken into consideration in the present evaluation. 1. Exposure Data 1.1.3 Chemical and physical properties of the pure substance 1.1 Identification of the agent Description: Nonflammable, mobile liquid. 1.1.1 Nomenclature Characteristic odour resembling that of chlo- roform (O’Neil et al., 2006) Chem. Abstr. Serv. Reg. No.: 79-01-6 Boiling-point: 86.9 °C (O’Neil et al., 2006) Deleted CAS Reg. No.: 52037-46-4 Melting-point: −84.8 °C (O’Neil et al., 2006) Chem. Abstr. Name: 1,1,2-Trichloroethene Density: 1.4642 at 20 °C/relative to H2O at IUPAC Systematic Name: Trichloroethylene 4 °C (O’Neil et al., 2006) Synonyms: Ethinyl trichloride; ethylene Spectroscopy data: Infrared (prism, 185; trichloride; TCE; 1,1,2-trichloroethylene grating, 62), nuclear magnetic resonance (proton, 9266; C-13, 410) and mass (583) spectral data have been reported (Sadtler 1.1.2 Structural and molecular formulae and Research Laboratories, 1980; Weast & Astle, relative molecular mass 1985). H Cl Solubility: Slightly soluble in water (1.1 g/L at 25 °C); soluble in ethanol, diethyl ether, acetone and chloroform (O’Neil et al., 2006); Cl Cl dissolves most fixed and volatile oils O’Neil( et al., 2006) C HCl 2 3 Volatility: Vapour pressure, 100 Pa at Relative molecular mass: 131.39 39 °C (Haynes, 2012); relative vapour density (air = 1.0), 4.53 (O’Neil et al., 2006) Stability: Photo-oxidized in air by sunlight (half-time, 5 days) giving phosgene and 35 IARC MONOGRAPHS – 106 dichloroacetyl chloride (EPA, 1985), which slowly decomposes with formation of Table 1.1 Some impurities and stabilizers found in commercial trichloroethylene hydrogen chloride by light in the presence of moisture (O’Neil et al., 2006). Impurities Stabilizers Reactivity: Incompatible with strong caustics Carbon tetrachloride Pentanol-2 and alkalis and with chemically active metals Chloroform Thymol such as barium, lithium, sodium, magnesium, 1,2-Dichloroethane Triethanolamine trans 1,2-Dichloroethylene Triethylamine titanium and beryllium (NIOSH, 1994a) cis 1,2-Dichloroethylene 2,2,4-Trimethylpentene Octanol/water partition coefficient (P): log P, Pentachloroethane Cyclohexene oxide 2.61 (Hansch et al., 1995) 1,1,1,2-Tetrachloroethane n-Propanol 1,1,2,2-Tetrachloroethane Isobutanol Conversion factor: mg/m3 = 5.37 × ppm 1,1,1-Trichloroethane N-methylmorpholine 3 1,1,2-Trichloroethane Diisopropylamine Calculated from: mg/m = (relative molecular 1,1-Dichloroethylene N-Methylpyrrole mass/24.45) × ppm, assuming normal tempera- Bromodichloroethylene Methyl ethyl ketone ture (25 °C) and pressure (101 kPa). Tetrachloroethylene Epichlorohydrin Bromodichloromethane 1.1.4 Technical products and impurities Benzene From WHO (1985) Trichloroethylene is available in the USA in vapour-degreasing, general-purpose and stabilizers used will depend on patent ownership high-purity grades (DOW Chemical, 2012). In and the technical specification being met WHO,( France, industrial-grade trichloroethylene is 1985). generally of high purity (> 99%). Depending Trade names for trichloroethylene include: on its intended use, it can contain one or more Algylen, Anamenth, Benzinol, Cecolene, stabilizers, including amines, alcohols or epox- Chlorilen, Chlorylea, Chlorylen, CirCosolv, ides (thymol, triethylamine, trimethyloxirane, Crawhaspol, Densinfluat, Dukeron, Dow-Tri, epoxybutane, etc.) at low concentration (< 1%) Fleck-Flip, Flock Flip, Fluate, Germalgene, (Table 1.1; Commission for Health and Safety at Lanadin, Lethurin, Narcogen, Narkosoid, Nialk, Work, 2012). Perm-AChlor, Petzinol, Philex, Threthylen, Possible impurities depend on the manufac- Threthylene, Trethylene, Tri, Triad, Trial, turing route, the type and quality of feed stock Trichloran, Trichloren, Triclene, Trielene, Trielin, used, the type of distillation equipment, and the Trieline, Trilen, Trilene, Trimar, TRI-Plus M, technical specification being met. It is uncommon Vestrol, Vitran, and Westrosol. for any individual impurity to be present at a level in excess of 100 mg/kg and for the total impuri- 1.1.5 Analysis ties to exceed 1000 mg/kg (WHO, 1985). Stabilizers, in the form of antioxidants or Methods for the analysis of trichloroethylene acid-receptors (such as phenolic, olephinic, have been reviewed by Delinsky et al. (2005) pyrrolic, and/or oxiranic derivatives and aliphatic and Demeestere et al. (2007). Selected methods amines), are usually added in concentrations that for the analysis of trichloroethylene in various normally range from 20 to 600 mg/kg; however, matrices are identified in Table 1.2. for limited quantities and special uses, concen- trations as high as 5000 mg/kg may be used. The 36 Trichloroethylene Table 1.2 Methods for the analysis of trichloroethylene Sample matrix Sample preparation Assay Limit of Reference procedure detection Air Analyte collected on sorbent tube; thermally GC/MS NR EPA (1999b) desorb to GC Air collected in specially prepared canister; GC/MS NR EPA (1999a) desorb from cold trap to GC Water Purge with inert gas and trap; desorb to GC GC/PID 0.02 µg/L EPA (1988, 1995a) GC/HECD 0.01 µg/L Purge with inert gas and trap; desorb to GC GC/PID 0.01 µg/L EPA (1988) Purge with inert gas and trap; desorb to GC GC/MS 0.02 µg/L EPA (1988, 1995b) Extract with methyl-t-butyl ether or pentane; GC/EC 0.002 µg/L EPA (1995c) Liquid and Purge with inert gas and trap GC/PID 0.02 µg/L EPA (1996) solid wastes GC/HECD 0.01 µg/L Blood Purge with inert gas and trap on Tenax GC/MS 0.004 ppb Ashley et al. (1992) EC, electron capture detection; FID, flame ionization detection; GC, gas chromatography; HECD, Hall electrolytic conductivity detection; MCD, microcoulometric detection; MS, mass spectrometry; PID, photoionization detection; ppb, parts per billion; NR, not reported 1.2 Production and use of trichloroethylene, tetrachloroethylene and hydrochloric acid. This process was developed 1.2.1 Production process and is used in Japan (Linak et al., 1992). (a) Manufacturing processes (b) Production volume Trichloroethylene was first prepared in 1864 In general, there has been a continuing decline by Emil Fischer in experiments on the reduction in demand for trichloroethylene over the years. of hexachloroethane with hydrogen (Hardie, Concern about the environmental and health 1964). Commercial production of trichloro- and safety implications of chlorinated solvents ethylene began in Germany in 1920 and in the has resulted in regulations and controls that USA in 1925 (Mertens, 1993). Originally, the have had an impact on the use and production acetylene-based process consisted of two steps: of trichloroethylene. For example, in the USA first, acetylene was chlorinated with a chloride the demand for trichloroethylene dropped from catalyst to produce 1,1,2,2-tetrachloroethane, 244 939 tonnes (540 million pounds) in 1971 to and then this product was dehydrohalogenated only 68 038 tonnes (150 million pounds) in 1990 to trichloroethylene (Mertens, 1993). (NICNAS, 2000). In Sweden, 4564 tonnes were The current method of manufacture is from used in 1993, but only 91 tonnes by 2009 (KEMI, ethylene. Trichloroethylene can be produced 2012). The production volume of trichloroethylene using oxichlorination or noncatalytic chlorina- in the European Union in 1996 was thought to tion of ethylene dichloride or other C2-chlorinated be between 51 000 and 225 000 tonnes per year hydrocarbons. Another method involves using (SCOEL/SUM, 2009). In 1995, this declining catalytic hydrogenation of tetrachloroethylene trend was reversed when the Montreal Protocol (ECSA, 2012). Trichloroethylene can also be on Substances that Deplete the Ozone Layer produced by direct chlorination of ethylene in was enacted: trichloroethylene was required in the absence of oxygen, giving a mixture of tetra- increasing amounts as a precursor in the manu- chloroethane and pentachloroethane. The prod- facture of chlorofluorocarbon alternatives and as ucts are thermally cracked to produce a mixture 37 IARC MONOGRAPHS – 106 a substitute for chemicals such as 1,1,1-trichlo- (a) Metal degreasing roethane (NICNAS, 2000). Before the 1990s, the major use of trichloro- In 2007, the USA was the largest consumer of ethylene was in metal degreasing. Degreasing is trichloroethylene, followed by western Europe, important in all metalworking and maintenance China, and Japan (Glauser & Ishikawa, 2008). operations to remove oils, greases, waxes, tars and moisture before final surface treatments, 1.2.2 Use such as galvanizing, electroplating, painting, Trichloroethylene is best known for its use anodizing and application of conversion coatings. as a solvent for cleaning and degreasing metal Trichloroethylene has been used in degreasing parts. However, it has had numerous other uses, operations in five main industrial groups: furni- including as an anaesthetic, a heat-transfer ture and fixtures, fabricated metal products, medium, an extraction agent for fats and oils, as electric and electronic equipment, transport an intermediate in producing chlorofluorocar- equipment and miscellaneous manufacturing bons and other chemicals, and as an ingredient industries. It has also been used in plastics, appli- in many products for industrial and consumer ances, jewellery, automobile, plumbing fixtures, use (Doherty, 2000). textiles, paper, glass and printing (Papdullo et al., Demand for trichloroethylene was gener- 1985;