Acute exposure can cause dizziness and loss of consciousness, chronic exposure may increase cancer risk. Unstable in presence of sunlight and caustic soda.
Trichloroethylene (TCE,IUPAC name:trichloroethene) is anorganochloride with the formula C2HCl3, commonly used as an industrial degreaser. It is a clear, colourless, non-flammable, volatile liquid with a sweetchloroform-like pleasant mild smell[3] and burning sweet taste.[11] Trichloroethylene has been sold under a variety of trade names. Under the trade namesTrimar andTrilene, it was used as avolatile anesthetic and as an inhaled obstetricalanalgesic. Industrial abbreviations includetrichlor,Trike,Tricky andtri. It should not be confused with the similar1,1,1-trichloroethane, which was commonly known aschlorothene.
The earliest trichloroethylene synthesis was reported byAuguste Laurent in 1836. Laurent obtained it from the action ofpotassium hydroxide on a mixture of1,1,2,2-tetrachloroethane and1,1,1,2-tetrachloroethane made from the chlorination ofethylene dichloride and notated it asC4HCl3 (then the atomic weight of carbon was thought to be half of what it really is). He named trichloroethylenechlorétherise but did not investigate the compound further as his sample seemed unstable.[12][13]
E. Fischer obtained trichloroethylene in 1864 via the reduction ofhexachloroethane with hydrogen. Fischer investigated the compound and noted its boiling point as between 87 and 90 degrees Celsius.[14][15][16]
Commercial production of trichloroethylene began in Germany, in 1920 and in the US in 1925.[17]
The use of trichloroethylene in the food and pharmaceutical industries has been banned in some parts of the world since the 1970s[18] due to concerns about its toxicity.
Trichloroethylene is a good analgesic at 0.35 to 0.5% concentrations.[19] Trichloroethylene was used in the treatment of trigeminal neuralgia beginning in 1916.[20] Trichloroethylene for use as an analgesic for neuralgia were sold under the trade names "Gemalgene", "Trethylene" and "Chlorylen".
Pioneered byImperial Chemical Industries in Britain, under the trade name "Trilene" (fromtrichloroethylene), its development was hailed as an anesthetic revolution. It was also sold as "Trimar" in the United States. The–mar suffix indicated study and development at theUniversity of Maryland, e.g., "Fluoromar" forfluroxene and "Vinamar" forethyl vinyl ether".[21] From the 1940s through the 1980s, both in Europe and North America, trichloroethylene was used as a volatile anesthetic almost invariably administered withnitrous oxide. Marketed in the UK byImperial Chemical Industries under the trade nameTrilene it was coloured blue with a dye calledwaxoline blue in 1:200,000 concentration[22] to avoid confusion with the similar-smelling chloroform.Trilene was stabilised with 0.01%thymol.[22] "Anamenth" was an early German anaesthetic trichloroethylene formulation which containedmenthol as the stabiliser.
Cyprane handheld anaesthetic device for trichloroethylene, made in the UK, 1947. This device was designed for self-administration by the patient.
Originally thought to possess lesshepatotoxicity thanchloroform, and without the unpleasant pungency and flammability ofether, TCE replaced earlier anesthetics chloroform and ether in the 1940s. TCE use was nonetheless soon found to have several pitfalls. These included promotion ofcardiac arrhythmias, low volatility and high solubility preventing quick anesthetic induction, prolonged neurologic dysfunction from the reaction withsoda lime used in carbon dioxide absorbing systems, and evidence of hepatotoxicity as had been found with chloroform. Alkali components of carbon dioxide absorbers reacted with trichloroethylene and releaseddichloroacetylene, a neurotoxin.
The introduction ofhalothane in 1956 greatly diminished the use of TCE as a general anesthetic in the 1960s, as halothane allowed much faster induction and recovery times and was considerably easier to administer. Trichloroethylene has also been used in the production of halothane.[23]
Bottle of trichloroethylene for anesthesia by ICIInhaler used for Trilene, 1961–1970
Trilene was also used as an inhaled analgesic, mainly during childbirth, often self-applied by the patient. It was introduced for obstetrical anaesthesia in 1943, and used until the 1980s.[19] Its anaesthetic use was banned in the United States in 1977 but the anaesthetic use in the United Kingdom remained until the late 1980s (especially for childbirth).[20] Fetal toxicity and concerns about the carcinogenic potential of TCE led to its abandonment in developed countries by the 1980s. TCE was used with halothane in the tri-service field anaesthetic apparatus used by the UK armed forces under field conditions. As of 2000[update], TCE was still in use as an anesthetic in Africa.[24][needs update]
When heated to around 400 °C with additional chlorine, 1,2-dichloroethane is converted to trichloroethylene:
ClCH2CH2Cl + 2 Cl2 → ClCH=CCl2 + 3 HCl
This reaction can be catalyzed by a variety of substances. The most commonly used catalyst is a mixture ofpotassium chloride andaluminum chloride. However, various forms of porouscarbon can also be used. This reaction producestetrachloroethylene as a byproduct and depending on the amount of chlorine fed to the reaction, tetrachloroethylene can even be the major product. Typically, trichloroethylene and tetrachloroethylene are collected together and then separated bydistillation.[25]
The 1,1,2,2-tetrachloroethane is then dehydrochlorinated to give trichloroethylene. This can be accomplished either with an aqueous solution ofcalcium hydroxide:[25]
Trichloroethylene is an effectivesolvent for a variety oforganic materials. It is mainly used for cleaning. Trichloroethylene is an active ingredient (solvent) in variousprinting ink,varnish and industrialpaint formulations.[26][20] Other uses includedyeing and finishing operations, adhesive formulations,rubber processing, adhesives,lacquers, andpaint strippers. It is applied beforeplating,anodizing, and painting.[27]
Perhaps the greatest use of TCE is as a degreaser for metal parts. It has been widely used in degreasing and cleaning since the 1910s because of its low cost, low flammability, low toxicity, and high effectiveness as a solvent. The demand for TCE as a degreaser began to decline in the 1950s in favor of the less toxic1,1,1-trichloroethane. However, 1,1,1-trichloroethane production has been phased out in most of the world under the terms of theMontreal Protocol due to its contribution to theozone depletion. As a result, trichloroethylene has experienced some resurgence in use as a degreaser.[20]
Trichloroethylene has been used as adry cleaning solvent, although mostly replaced by tetrachloroethylene, except for spot cleaning – for grease and oil stains – where it is still often used under various tradenames. It was found unfavourable for dry cleaning because it tended to dissolve acetate dyes, which tetrachloroethylene did not. Trichloroethylene is used to remove grease andlanolin fromwool beforeweaving.[20]
TCE has also been used in the United States to clean kerosene-fueled rocket engines (TCE was not used to clean hydrogen-fueled engines such as theSpace Shuttle Main Engine). During static firing, theRP-1 fuel would leave hydrocarbon deposits and vapors in the engine. These deposits had to be flushed from the engine to avoid the possibility of explosion during engine handling and future firing. TCE was used to flush the engine's fuel system immediately before and after each test firing. The flushing procedure involved pumping TCE through the engine's fuel system and letting the solvent overflow for a period ranging from several seconds to 30–35 minutes, depending upon the engine. For some engines, the engine's gas generator andliquid oxygen (LOX) dome were also flushed with TCE before test firing.[28][29] TheF-1 rocket engine had its LOX dome, gas generator, and thrust chamber fuel jacket flushed with TCE during launch preparations.[29]
TCE is also used in the manufacture of a range of fluorocarbon refrigerants[30] such as1,1,1,2-tetrafluoroethane more commonly known as HFC-134a.[31]
CHCl=CCl2 + 4 HF → CF3CH2F + 3 HCl
TCE was also used in industrial refrigeration applications due to its high heat transfer capabilities and its low-temperature specification.[citation needed]
1,1,2,2-tetrachloroethylsulfenyl chloride, used in the production ofcaptafol, is obtained from trichloroethylene andsulfur dichloride:
C2HCl3 + SCl2 → C2HCl4SCl
The reaction of trichloroethylene with chloroform can yield different compounds depending on the catalyst used. If sodium hydroxide is used, chloroform is dehydrochlorinated todichlorocarbene which adds to trichloroethylene, andpentachlorocyclopropane is obtained:
C2HCl3 + :CCl2 → C3HCl5
The reaction of trichloroethylene with chloroform under the catalyst aluminum chloride gives1,1,1,2,3,3-Hexachloropropane:
CHCl3 + C2HCl3 → CHCl2CHClCCl3
The reaction of trichloroethylene withcarbon tetrachloride under similar conditions gives 1,1,1,2,3,3,3-heptachloropropane:[32]
Despite its widespread use as a metaldegreaser, trichloroethylene itself is unstable in the presence of metal over prolonged exposure. As early as 1961 this phenomenon was recognized by the manufacturing industry when stabilizing additives were added to the commercial formulation. Since the reactive instability is accentuated by higher temperatures, the search for stabilizing additives was conducted by heating trichloroethylene to its boiling point under areflux condenser and observing decomposition. Definitive documentation of1,4-dioxane as a stabilizing agent for TCE is scant due to the lack of specificity in early patent literature describing TCE formulations.[33][34]Epichlorohydrin,butylene oxide,N-methylpyrrole andethyl acetate are common stabilisers for TCE, with epichlorohydrin being the most persistent and effective.[25] Other chemical stabilizers includeketones such asmethyl ethyl ketone.
Two advertisements for trichloroethylene in two different uses, metal degreasing (1947) and anaesthesia (1952)
When inhaled, trichloroethylene producescentral nervous system depression resulting ingeneral anesthesia. These effects may be mediated by trichloroethylene acting as apositive allosteric modulator of inhibitoryGABAA andglycine receptors.[35][36] Its high blood solubility results in a less desirable slower induction of anesthesia. At low concentrations, it is relatively non-irritating to the respiratory tract. Higher concentrations result intachypnea. Many types of cardiacarrhythmias can occur and are exacerbated byepinephrine (adrenaline). It was noted in the 1940s that TCE reacted with carbon dioxide (CO2) absorbing systems (soda lime) to producedichloroacetylene bydehydrochlorination andphosgene.[37]Cranial nerve dysfunction (especially the fifth cranial nerve) was common when TCE anesthesia was given using CO2 absorbing systems. Muscle relaxation with TCE anesthesia sufficient for surgery was poor. For these reasons as well as problems withhepatotoxicity, TCE lost popularity in North America and Europe to more potent anesthetics such ashalothane by the 1960s.[38]
The symptoms of acute non-medical exposure are similar to those ofalcohol intoxication, beginning with sleepiness, dizziness, and confusion and progressing with increasing exposure to unconsciousness.[39] Much of what is known about the chronic human health effects of trichloroethylene is based on occupational exposures. Besides its effects on the central nervous system, industrial exposure to trichloroethylene is correlated with toxic effects in the liver and kidney.[39]
Long-term industrial[40] or ambient environmental[41] exposure to trichloroethylene is suspected to elevate the risk of developingParkinson's disease.
Trichloroethylene has been classified as "Group 1: Carcinogenic to Humans" by theInternational Agency for Research on Cancer (IARC) due to sufficient evidence in humans and experimental animals for cancer of the kidney and a positive association between exposures to trichloroethylene and development of non-Hodgkin lymphoma and liver cancer in humans, and limited evidence in humans and experimental animals for increased incidence of leukemia, lymphoma, reproductive cancers, and respiratory cancers.[42]
With aspecific gravity greater than 1 (denser than water), trichloroethylene can be present as adense non-aqueous phase liquid (DNAPL) if sufficient quantities are spilt in the environment.
The first known report of TCE in groundwater was given in 1949 by two English public chemists who described two separate instances of well contamination by industrial releases of TCE.[48] Based on available federal and state surveys, between 9% and 34% of the drinking water supply sources tested in the US may have some TCE contamination, though EPA has reported that most water supplies comply with the maximum contaminant level (MCL) of 5 ppb.[49]
Generally, atmospheric levels of TCE are highest in areas of concentrated industry and population. Atmospheric levels tend to be lowest in rural and remote regions. Average TCE concentrations measured in air across the United States are generally between 0.01 ppb and 0.3 ppb, although mean levels as high as 3.4 ppb have been reported.[50] TCE levels in the low parts per billion range have been measured in food; however, levels as high as 140 ppb were measured in a few samples of food.[50] TCE levels above background[how?] have been found in homes undergoingrenovation.[51]
State, federal, and international agencies classify trichloroethylene as a known or probable carcinogen for humans. In 2014, theInternational Agency for Research on Cancer updated its classification of trichloroethylene toGroup 1, indicating that sufficient evidence exists that it can cause cancer of the kidney in humans as well as some evidence of cancer of the liver andnon-Hodgkin's lymphoma.[52]
Existing EU legislation aimed at protection of workers against risks to their health (including Chemical Agents Directive 98/24/EC[54] and Carcinogens Directive 2004/37/EC[55]) currently do not impose binding minimum requirements for controlling risks to workers' health during the use phase or throughout the life cycle of trichloroethylene.
In 2023, the United StatesUnited States Environmental Protection Agency (EPA) determined that trichloroethylene presents a risk of injury to human health in various uses, including during manufacturing, processing, mixing,recycling, vapor degreasing, as a lubricant, adhesive,sealant, cleaning product, and spray. It is dangerous from both inhalation anddermal exposure and was most strongly associated withimmunosuppressive effects for acute exposure, as well asautoimmune effects for chronic exposures.[56] Chronic exposure to trichloroethylene has also been linked to an increased risk ofParkinson's disease.[57][58] As of June 1, 2023, two U.S. states (Minnesota andNew York) have acted on the EPA's findings and banned trichloroethylene in all cases but research and development.[59][60] According to the US EPA, in October 2023 it "proposed to ban the manufacture (including import), processing, and distribution in commerce of TCE for all uses, with longer compliance time frames and workplace controls (including an exposure limit) for some processing and industrial and commercial uses until the prohibitions come into effect" to "protect everyone including bystanders from the harmful health effects of TCE".[61] Following the EPA's recommendation theBiden Administration announced a proposal to ban trichloroethylene later that month.[62] In December 2024 the EPA issued a final ruling on the regulation of trichloroethylene, with the rule taking effect on January 16, 2025.[63] The rule bans the manufacture (including import), processing, and distribution in commerce of trichloroethylene for all uses, with longer compliance timeframes and stringent worker protections for some processing and industrial and commercial uses until the prohibitions come into effect.[64] The EPA is prohibiting most uses of trichloroethylene within one year of the rule taking effect including manufacture and processing for most commercial and all consumer products, with only a limited number of commercial uses being allowed after January 16, 2026.[65] These uses will eventually be phased out as well, though an exact timeframe hasn't been determined yet, but until they have been phased out more stringent worker protections will be required with a lowerinhalationexposure limit forairborne trichloroethylene being put in place.[64] Many of the trichloroethylene uses that are continuing for longer than one year occur in highlyindustrialized settings with critical uses such as the cleaning of parts used inmedical devices, aircraft & other transportation,security anddefense systems and the manufacture ofbatteryseparators andrefrigerants.[64] These uses will ultimately be prohibited as well but are temporarily being allowed to continue in order to avoid negative impacts tonational security orcritical infrastructure, and to allow time to transition to alternative chemicals and methods.[64]
Research has focused on the in-place remediation of trichloroethylene in soil and groundwater usingpotassium permanganate instead of removal for off-site treatment and disposal. Naturally occurringbacteria have been identified with the ability to degrade TCE.Dehalococcoides sp. degrade trichloroethylene by reductive dechlorination under anaerobic conditions. Under aerobic conditions,Pseudomonas fluorescens can co-metabolize TCE. Soil and groundwater contamination by TCE has also been successfully remediated by chemical treatment and extraction. The bacteriaNitrosomonas europaea can degrade a variety of halogenated compounds including trichloroethylene.[66]Toluene dioxygenase has been reported to be involved in TCE degradation byPseudomonas putida.[67] In some cases,Xanthobacter autotrophicus can convert up to 51% of TCE to CO and CO2.[67]
Trichloroethylene has been used as arecreational drug.[68] Reported methods of TCE abuse include inhalation and drinking.[69] It was abused for its euphoriant and slight hallucinogenic effect by mostly young people and workers who used the chemical.[69] Some industrial workers had become addicted to TCE.[70]
Groundwater anddrinking water contamination from industrial discharge including trichloroethylene is a major concern for human health and has precipitated numerous incidents and lawsuits in the United States. One notable example is that of Woburn, Massachusetts, (Anderson v. Cryovac) where improper disposal of industrial solvents including trichloroethylene by local companies led to the contamination of two municipal wells.[71] Families blamed the supposed local increase in leukemia cases on trichloroethylene pollution,[72] although trichloroethylene does not cause leukemia in humans. The incident gained national attention in the 1980s and was the subject of extensive litigation, culminating in a settlement between the companies and affected families[73] It later served as the basis for the bookA Civil Action by Jonathan Harr, which was adaptedadapted to cinema in 1998.
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^Hardie DWF (1964). Chlorocarbons and chlorohydrocarbons. 1,1,2,2-Tetrachloroethane. In: Encyclopedia of Chemical Technology. Kirk RE, Othmer DF, editors. New York: John Wiley & Sons, pp. 159–164
^Mertens JA (1993). Chlorocarbons and chlorohydrocarbons. In: Kirk-Othmer Encyclopedia of Chemical Technology, 4th Ed. Kroschwitz JI, Howe-Grant M, editors. New York: John Wiley & Sons, pp. 40–50.
^abCurrent Researches in Anesthesia & Analgesia. (1951). USA: International Anesthesia Research Society. p.278
^Suckling et al.,"Process for the Preparation of 1,1,1-trifluoro-2-bromo-2-chloroethane",US patent 2921098, granted January 1960 , assigned to Imperial Chemical Industries
^Asinger, F. "1,1,1,2,3,3-hexachloropropane" in Paraffins: Chemistry and Technology. Elsevier Science.
^Murphy, Brian L; Morrison, Robert D. (2015). "9. Source Identification and Age Dating of Chlorinated Solvents".Introduction to environmental forensics (3rd ed.).Academic Press. sec. 9.2.2.1 1,4-Dioxane.ISBN978-0-12-404707-5.
^Mohr, Thomas K. G. (2010). "Historical Use of Chlorinated Solvents and Their Stabilizing Compounds".Environmental investigation and remediation: 1,4-dioxane and other solvent stabilizers.CRC Press. p. 53 "Was 1,4-Dioxane a Stabilizer for Trichloroethylene?".ISBN978-1-56670-662-9.
^M. J. Beckstead, J. L. Weiner, E. I. 2nd Eger, D. H. Gong & S. J. Mihic (2000). "Glycine and gamma-aminobutyric acid(A) receptor function is enhanced by inhaled drugs of abuse".Molecular Pharmacology.57 (6):1199–1205.doi:10.1016/S0026-895X(24)23230-2.PMID10825391.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
^Orkin, F. K. (1986) Anesthesia Systems (Chapter 5). In R. D. Miller (Ed.), Anesthesia (second edition). New York, NY: Churchill Livingstone.[page needed]
^Stevens, W.C. and Kingston H. G. G. (1989) Inhalation Anesthesia (Chapter 11). In P. G. Barash et al. (Eds.) Clinical Anesthesia. Philadelphia, PA: Lippincott.[page needed]
^Lyne FA, McLachlan T (1949). "Contamination of water by trichloroethylene" p. 513 inLilliman, B.; Houlihan, J. E.; Lyne, F. A.; McLachlan, T. (1949). "Notes".The Analyst.74 (882):510–513.Bibcode:1949Ana....74..510L.doi:10.1039/AN9497400510.
^Minnesota Statutes (act 116.38 (also known as "White Bear Area Neighborhood Concerned Citizens Group Ban TCE Act"), Environmental Protection, Chapter 116, Section 116.385). Minnesota Legislature. 2022.Archived from the original on 6 September 2023.
^Trichloroethylene inNeurology in Clinical Practice, Daroff, R. B., Fenichel, G. M., Jankovic, J., Mazziotta, J. C. (2012)
^abChapter 50: Trichloroethylene Medical Toxicology of Drug Abuse: Synthesized Chemicals and Psychoactive Plants. Barceloux, D. G. (2012).
^Trichlorethylene Addiction and its Effects (1972) Boleslaw Alapin M.D., M.R.C. Psych. British Journal of Addiction to Alcohol & Other DrugsVolume 68, Issue 4 p. 331–335DOI
^Costas, Kevin; Knorr, Robert S; Condon, Suzanne K (2 December 2002). "A case–control study of childhood leukemia in Woburn, Massachusetts: the relationship between leukemia incidence and exposure to public drinking water".Science of the Total Environment.300 (1):23–35.Bibcode:2002ScTEn.300...23C.doi:10.1016/S0048-9697(02)00169-9.PMID12685468.
Doherty, Richard E. (2000). "A History of the Production and Use of Carbon Tetrachloride, Tetrachloroethylene, Trichloroethylene and 1,1,1-Trichloroethane in the United States: Part 2 – Trichloroethylene and 1,1,1-Trichloroethane".Environmental Forensics.1 (2):83–93.Bibcode:2000EnvFo...1...83D.doi:10.1006/enfo.2000.0011.S2CID97370778.
Lipworth, Loren; Tarone, Robert E.; McLaughlin, Joseph K. (2006). "The Epidemiology of Renal Cell Carcinoma".The Journal of Urology.176 (6):2353–2358.doi:10.1016/j.juro.2006.07.130.PMID17085101.
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