IAQUK Resources - Tetrachlorethylene
Sources of Pollution
Michael Faraday, who also discovered Benzene, first
synthesized Tetrachloroethene in 1821 by thermal decomposition (a chemical
reaction in which a compound breaks up into at least two other substances when
heated) of hexachloroethane into Tetrachloroethene and chlorine.
Most Tetrachloroethene is produced by high
temperature chlorinolysis of light hydrocarbons. The method is related to
Faraday's discovery since hexachloroethane is generated and thermally
decomposes. Side products include carbon tetrachloride, hydrogen chloride, and
This reaction can be catalyzed (rate of chemical
reaction) by a mixture of potassium chloride and aluminium chloride, or by activated carbon.
Trichloroethylene is a major byproduct of the reaction, and
since both are salable commercial chemicals, typical industrial practice is to
collect both products and then separate them by distillation.
Tetrachloroethylene is an excellent solvent for organic materials. Otherwise it
is volatile, highly stable, and nonflammable. For these reasons, it is widely used
in dry cleaning. Usually as a mixture with other chlorocarbons, it is also used
to degrease metal parts in the automotive and other metalworking industries.
It appears in a few consumer products including
contact adhesives, degreasing agents, wax removers, shoe polishes, garden
pesticides, upholstery cleaners and carpet cleaners. In most products,
Tetrachloroethene has been replaced by other less toxic solvents.
Tetrachloroethene was once extensively used as an
intermediate in the manufacture of HFC-134a and related refrigerants. In the
early 20th century, Tetrachloroethene was used for the treatment for hookworm infestation (parasitic
The results of single or short-term human
exposure to Tetrachloroethylene indicate that human beings are likely to begin
to experience eye irritation at air concentrations of approximately 500 mg/m3,
and depression of the central nervous system and nose and throat irritation at
approximately 700 mg/m3. Such effects are reversible on cessation of exposure,
but increase in severity with both increasing concentration and duration of
High concentrations of Tetrachloroethylene (particularly in closed, poorly
ventilated areas) can cause dizziness, headache, sleepiness, confusion, nausea,
difficulty in speaking and walking, unconsciousness, and death. Observations after repeated exposure to Tetrachloroethylene, over months or years, indicate
that human beings inhaling Tetrachloroethylene are likely to begin to exhibit
depression of the central nervous system at concentrations exceeding
approximately 700 mg/m3.
Results from some studies suggest that women who work in dry cleaning
industries where exposures to Tetrachloroethylene can be quite high may have
more menstrual problems and spontaneous abortions than women who are not
exposed. However, it is not known if Tetrachloroethylene was responsible for these problems
because other possible causes were not considered.
The International Agency for Research on
Cancer has classified Tetrachloroethylene as probably
carcinogenic to humans. Prolonged exposure to high levels is believed to be necessary to
cause cancer. Like many chlorinated hydrocarbons, Tetrachloroethene is a
central nervous system depressant and can enter the body through inhalation.
Most Tetrachloroethylene is excreted unchanged via the lungs. Removal
of Tetrachloroethylene from blood and excretion in the breath are slow, the
amount increasing with increasing exposure level. The concentrations of the
compound in blood and breath can be used for estimating
One way of testing for Tetrachloroethylene exposure is to
measure the amount of the chemical in the breath, much the same way
breath-alcohol measurements are used to determine the amount of alcohol in the
blood. Because it is stored in the body's fat and slowly released into the
bloodstream, Tetrachloroethylene can be detected in the breath for weeks following
a heavy exposure.
Tetrachloroethylene and Trichloroacetic acid (TCA), a breakdown product
of Tetrachloroethylene, can be detected in the blood. These tests are
relatively simple to perform.
Because exposure to other chemicals can produce the same breakdown
products in the urine and blood, the tests for breakdown
products cannot determine if you have been exposed to Tetrachloroethylene or the other
A study of 99 twins by Dr. Samuel Goldman and researchers at the
Parkinson's Institute in Sunnyvale, California determined there is a "lot
of circumstantial evidence" that exposure to Tetrachloroethlene increases
the risk of developing Parkinson's disease ninefold. Larger population studies
Technical - Tetrachloroethylenee - Cl2C=CCl2.
- Ether-like odour
- Detectable in the air at 1ppm
- CAS Number: 127-18-4
LTEL - 50ppm (345 mg/m³)
STEL - 100ppm (689mg/m³)
- Risk Phrases: R40, 51, 53
- Safety Phrases: S23, 36, 37, 61
Tetrachloroethylene is a manufactured chlorocarbon (chlorine-containing
compound. The chlorocarbons have long been known for causing organ,
genetic and reproductive damage), with the formula Cl2C=CCl2. It is a
colourless liquid widely used fordry cleaning of fabrics, hence it is
sometimes called dry-cleaning fluid.