IAQUK Resources - Trichlorethylene
Sources of Pollution
Trichloroethylene was first synthesized by Berlin chemist Hermann Emil Fischer in
1864 whilst working on tetrachlorethan but wasn’t commercially produced
inGermany until the 1900s as a degreaser. Fischer is noted
for for the Nobel Prize in Chemistry
1902, for the 'complete synthesis' of caffeine and his work
on sugar and purine syntheses.
Most Trichloroethylene is produced from ethylene.
First, ethylene is chlorinated to produce 1,2-dichloroethane and then heated to
around 400 °C with additional chlorine, 1,2-dichloroethane is converted to
Trichloroethylene. When it was first
widely produced in the 1920s, Trichloroethylene's major use was to extract vegetable oils
from plant materials such as soy, coconut, and palm. Other uses in the food
industry included coffee decaffeination and the preparation of flavoring
extracts from hops and spices. It has also been used fordrying out the last bit
of water for production of 100% ethanol. From the 1930s through
the 1970s it was used as an anesthetic and thought to possess less
hepatotoxicity (toxic to the liver) than chloroform, and without the unpleasant
pungency and flammability of ether. However, Trichloroethylene was
found to cause cardiac arrhythmias (irregular heartbeat or abnormal heart rhythm) and was
replaced in the 1950s by a faster induction and recovery time of halothane.
Trichloroethylene was also used as an inhalation analgesic in childbirth,
concerns about fetal toxicity and carcinogenic potential led to a replacement
Trichloroethylene has primarily been as a degreaser
parts. The demand for Trichloroethylene as a degreaser began to decline
in the 1950s in favour of the less toxic 1,1,1-trichloroethane. However,
1,1,1-trichloroethane production has been phased out in most of the world under
the terms of the Montreal Protocol, and as a result Trichloroethylene has
experienced some resurgence in use as a degreaser.
Legislation has forced the substitution of
Trichloroethylene in many processes inEurope as the chemical was classified as
a carcinogen carrying an R45 risk phrase. Many degreasing chemical alternatives
are being promoted such as Ensolv and Leksol, however, each of these is based
on n-propyl bromide, which carries an R60 risk phrase and they would not be a
legally acceptable substitute.
As a solvent or as a component of solvent blends,
Trichloroethylene is used in adhesives, lubricants, paints, varnishes,
paint strippers, carpet shampoos and waterproofing agents. The textile industry
uses it to scour cotton, wool and other fabrics (remove oils or lubricants), and in waterless
dyeing and finishing.
When inhaled, Trichloroethylene produces central nervous system
depression resulting in general anesthesia. The symptoms of acute non-medical
exposure are similar to those of alcohol intoxication, beginning with headache,
dizziness, and confusion and progressing with increasing exposure to
unconsciousness. Respiratory and circulatory
depression can result in death.
At low concentrations it is relatively
non-irritating to the respiratory tract.
Higher concentrations result in tachypnea (rapid
breathing). Many types of cardiac arrhythmias can occur and are exacerbated by
Very large exposures may cause irreversible cardiac
problems, nerve and liver damage, and death.
Chronic (long-term) exposures to Trichloroethylene have been shown to
cause nausea, intolerance to fatty foods, respiratory irritation, renal
(kidney) toxicity, and immune system depression. Alcohol consumption increases
the toxicity of Trichloroethylene and may cause 'degreaser's flush', which
appears as red blotches on the skin.
Much of what is known about the human health effects of
Trichloroethylene is based on occupational exposures. Beyond the effects to the
central nervous system, workplace exposure to Trichloroethylene has been
associated with toxic effects in the liver and kidney.
Trichloroethylene is a cleaning solvent that was used to clean military
weapons during the Gulf War. There are reports associating exposure to this
solvent with amyotrophic lateral sclerosis (a form of motor neuron disease),
and also with a neurologic syndrome resembling Parkinson's disease.
The International Agency for Research on
Cancer has classified Trichloroethylene as a 'probable human carcinogen'.
Technical - Trichlorethylene - C
- Colourless, voltaile liquid
- Sweet odour
- CAS Number: 70-07-6
LTEL - 100ppm (550 mg/m³)
STEL - 150ppm (820 mg/m³)
- Risk Phrases: R20, 21, 22, 40, 52, 53
- Safety Phrases: S23, 36, 37, 61
The Trichloroethylene is a chlorinated hydrocarbon
commonly used as an industrial solvent. It is a clear non-flammable liquid with
a sweet smell.
It is also used for processing and finishing in the
textile industry, as an extraction solvent, veterinary anthelmintic (drugs that
are used to treat infections with parasitic worms), heat-exchange fluid, grain
fumigant, and in the manufacture of fluorocarbons (compounds that contain only
carbon and fluorine bonded together). It was also used in the dry cleaning
industry until the mid-1950s, when it was replaced by tetrachloroethylene.
It is one of the 50 most significant VOCs (in terms
of mass emission) released into the UK environment.
Other names for Trichloroethylene include
Trichloroethene and Ethylene Trichloride.