Map showing all locations mentioned on Wikipedia article:

The IUPAC name
is trichloroethene. Industrial abbreviations
include TCE, trichlor,
Trike, Tricky and
tri. It has been sold under a variety of trade
names. Under the trade names Trimar and
Trilene, trichloroethylene was used as a volatile
anesthetic and as an inhaled obstetrical
analgesic in millions of patients.

History

Pioneered by Imperial
Chemical Industries in Britain, its development was hailed as
an anesthetic revolution. Originally thought to possess less
hepatotoxicity than chloroform, and without the unpleasant pungency
and flammability of ether, TCE use was
nonetheless soon found to have several pitfalls. These included
promotion of cardiac
arrhythmias, too low a volatility for quick anesthetic
induction, reactions with soda lime used
in carbon dioxide absorbing systems, prolonged neurologic
dysfunction when used with soda lime, and evidence of
hepatotoxicity as had been found with chloroform.

The introduction of halothane in 1956
greatly diminished the use of TCE as a general anesthetic. TCE was
still used as an inhalation analgesic in childbirth given by
self-administration. Fetal toxicity and concerns for carcinogenic
potential of TCE led to its abandonment in the 1980s.

Due to concerns about its toxicity, the use of trichloroethylene in
the food and pharmaceutical industries has been banned in much of
the world since the 1970s. Legislation has forced the substitution
of trichloroethylene in many processes in Europe 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.

Groundwater contamination by TCE has become an important
environmental concern. Seepage of the compound into groundwater has
raised health concerns in many locations.

This reaction can be catalyzed by a variety of substances. The most
commonly used catalyst is a mixture of potassium chloride and aluminum chloride. However, various forms
of porous carbon can also be used. This
reaction produces tetrachloroethylene 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 by distillation.

Uses

Trichloroethylene is an effective solvent
for a variety of organic
materials.

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 coffeedecaffeination
and the preparation of flavoring extracts from hops and spices. It has also been
used for drying out the last bit of water for production of 100%
ethanol.

From the 1930s through the 1970s, both in Europe and North America,
trichloroethylene was used as a volatile gas anesthetic. TCE was
used in place of earlier the anesthetics chloroform and ether
in the 1940s, but was itself replaced in the 1950s by the newer
halothane, which allowed much faster
induction and recovery times. Marketed in the UK by ICI under the
trade name Trilene it was coloured blue (with a dye called waxolene
blue) to avoid confusion with the similar smelling
chloroform.

Perhaps the greatest use of TCE has been as a degreaser for metal
parts. The demand for TCE as a degreaser began to decline in the
1950s in favor 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.

Chemical instability

Despite its widespread use as a metal degreaser, 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 in
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 in a reflux condenser and
observing decomposition. The first widely used stabilizing additive
was dioxane; however, its use was patented
by Dow Chemical Company and
could not be used by other manufacturers. Considerable research
took place in the 1960s to develop alternative stabilizers for
trichloroethylene. Other chemical stabilizers include ketones such as methyl
ethyl ketone.

Physiological effects

When inhaled, trichloroethylene produces central nervous system depression
resulting in general anesthesia. Its high
lipid 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 in tachypnea. Many types of cardiac arrhythmias can occur and are exacerbated by
epinephrine (adrenaline). It was noted
in the 1940s that TCE reacted with carbon dioxide (CO2) absorbing
systems (soda lime) to produce
dichloroacetylene and phosgene. Cranial nerve dysfunction (especially the
fifth cranial nerve) was not uncommon when TCE anesthesia was given
using CO2 absorbing systems. These nerve deficits could last for
months. Occasionally facial numbness was permanent. Muscle
relaxation with TCE anesthesia sufficient for surgery was poor. For
these reasons as well as problems with hepatotoxicity, TCE lost popularity in North
America and Europe to more potent anesthestics such as halothane by the 1960s.

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.

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 . Over time, occupational exposure limits on
trichloroethylene have tightened, resulting in more stringent
ventilation controls and personal protective equipment use by
workers.

The National Toxicology Program’s 11th Report on Carcinogens
categorizes trichloroethylene as “reasonably anticipated to be a
human carcinogen”, based on limited evidence of carcinogenicity
from studies in humans and sufficient evidence of carcinogenicity
from studies in experimental animals.

One recent review of the epidemiology of kidney cancer rated cigarette smoking
and obesity as more important risk factors for kidney cancer than
exposure to solvents such as trichloroethylene. In contrast, the
most recent overall assessment of human health risks associated
with trichloroethylene states, "[t]here is concordance between
animal and human studies, which supports the conclusion that
trichloroethylene is a potential kidney carcinogen". The evidence
appears to be less certain at this time regarding the relationship
between humans and liver cancer observed in mice, with the NAS
suggesting that low-level exposure might not represent a
significant liver cancer risk in the general population.

Recent studies in laboratory animals and observations in human
populations suggest that exposure to trichloroethylene might be
associated with congenital heart defects While it is not clear what
levels of exposure are associated with cardiac defects in humans,
there is consistency between the cardiac defects observed in
studies of communities exposed to trichloroethylene contamination
in groundwater, and the effects observed in laboratory animals. A
study published in August 2008, has demonstrated effects of TCE on
human mitochondria. The article questions whether this might impact
female reproductive function.

The health risks of trichloroethylene have been studied
extensively. The U.S.Environmental Protection
Agency (EPA) sponsored a "state of the science" review of the
health effects associated with exposure to trichloroethylene.
The
National Academy of Sciences concluded that evidence on the carcinogenic risk
and other potential health hazards from exposure to TCE has
strengthened since EPA released their toxicological assessment of
TCE, and encourages federal agencies to finalize the risk
assessment for TCE using currently available information, so that
risk management decisions for this chemical can be
expedited.

Human exposure

Some are exposed to TCE through contaminated drinking water.Another
significant source of vapor exposure in Superfund sites that had
contaminated groundwater, such as the Twin Cities Army Ammunition
Plant, was by showering. TCE readily volatilizes out of hot water
and into the air. Long, hot showers would then volatilize more TCE
into the air. In a home closed tightly to conserve the cost of
heating and cooling, these vapors would then recirculate.

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. Based on
available federal and state surveys, between 9% to 34% of the
drinking water supply sources tested in the U.S. may have some TCE
contamination, though EPA has reported that most water supplies are
in compliance with the Maximum Contaminant Level (MCL) of 5 ppb. In
addition, a growing concern in recent years at sites with TCE
contamination in soil or groundwater has been vapor intrusion in
buildings, which has resulted in indoor air exposures, such is in a
recent case in the McCook Field Neighborhood of Dayton, Ohio.
Trichloroethylene has been detected in 852 Superfund sites across
the United States, according to the Agency for
Toxic Substances and Disease Registry (ATSDR). Under the Safe
Drinking Water Act of 1974, and as amendedannual water quality
testing is required for all public drinking water distributors. The
EPA'S current guidelines for TCE can be found here. It should be noted that the EPA's table
of "TCE Releases to Ground" is dated 1987 to 1993, thereby omitting
one of the largest Superfund Cleanup sites in the nation, the NIBW
in Scottsdale, Arizona. The TCE "released" here occurred prior to
its appearance in the municipal drinking wells in 1982.

As of 2007, 57,000 pounds, or roughly 19 tons of TCE have been
removed from the system of wells that once supplied drinking water
to the residents of Scottsdale. One of the three drinking water
wells previously owned by the City of Phoenix and ultimately sold
to the City of Scottsdale, tested at 390 ppb TCE when it was closed
in 1982.(see East Valley Tribune, April 6, 2007, "Feds to Examine
Superfund Site" by John Yantis) Some Scottsdale residents who
received their water bills from the City of Phoenix throughout the
1960s and 70's were understandably confused as to whether they
indeed had been consuming contaminated water when information about
the Superfund site was first disseminated. The City of Scottsdale
recently updated their website to clarify that the contaminated
wells were "in the Scottsdale area" and to delete all references to
the levels of TCE discovered when the wells were closed as
"trace".

A spot was then ultimately chosen to receive and treat the
contaminated drinking water known as the Central Groundwater
Treatment Facility. Then 1989, as now, this treatment facility
(CGTF) is situated on land adjacent to Pima Park and the Siemens
facility documented as one of the Potentially Responsible Parties
at the corner of Thomas and Pima roads. Close proximity to this
park did not appear to enter into Motorola's calculations when
asserting that it would save money to remove the carbon air filters
in 2007. (See East Valley Tribune, October 5, 2007, "Motorola wants
to axe filters at Superfund site" by Ari Cohn)

Camp Lejeune in North Carolina may be the largest TCE contamination
site in the country. Legislation could force the EPA to establish a
health advisory and a national public drinking water regulation to
limit trichloroethylene.

For over twenty years of operation, the US-based multinational
Radio Company of America (RCA) had been pouring
toxic wastewater into a well in its Taoyuan, Taiwan facility. The
pollution from the plant was not revealed until 1994, when former
workers brought it to light. Investigation by the Taiwan
Environmental Protection Administration confirmed that RCA had been
dumping chlorinated organic solvents into a secret well and caused
contamination to the soil and groundwater surrounding the plant
site. High levels of TCE tetrachloroethylene (PCE) can be found in
groundwater drawn as far as two kilometers from the site. An
organization of former RCA employees reports 1375 cancer cases, 216
cancer deaths, and 102 cases of various tumors among its
members.

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
(Kasarskis EJ et al. Amyotrophic Lateral Sclerosis, 2008 Sep
16:1-7, Clinical aspects of ALS in Gulf War Veterans), and also
with a neurologic syndrome resembling Parkinson's disease (Gash DM. et al. Ann
Neurol. 2008 Feb;63(2):184-92. Trichloroethylene: Parkinsonism and
complex 1 mitochondrial neurotoxicity).

Existing regulation

Until recent years, the US Agency for Toxic Substances and Disease
Registry (ATSDR) contended that trichloroethylene had little-to-no
carcinogenic potential, and was probably a
co-carcinogen—that is, it acted in concert with other
substances to promote the formation of tumors.

Half a dozen state, federal, and international agencies now
classify trichloroethylene as a probable carcinogen. The International Agency
for Research on Cancer considers trichloroethylene a Group 2A
carcinogen, indicating that it considers it is probably
carcinogenic to humans.California EPA regulators consider it a
known carcinogen and issued a risk assessment in 1999 that
concluded that it was far more toxic than previous scientific
studies had shown.

Proposed U.S. federal regulation

In 2001, a draft report of the Environmental Protection Agency
(EPA) laid the groundwork for tough new standards to limit public
exposure to trichloroethylene. The assessment set off a fight between the
EPA and the Department of Defense (DoD), the Department of Energy, and
NASA, who appealed directly to the White House.
They argued that the EPA had produced junk science, its assumptions
were badly flawed, and that evidence exonerating the chemical was
ignored.

The DoD has about 1,400 military properties nationwide that are
contaminated with trichloroethylene. Many of these sites are
detailed and updated by www.cpeo.org and include a former
ammunition plant in the Twin Cities area. Twenty three sites in
the Energy Department's nuclear weapons complex — including
Lawrence Livermore National
Laboratory in the San Francisco Bay area, and NASA centers,
including the Jet Propulsion Laboratory in La Cañada Flintridge are reported to have TCE
contamination.

Political appointees in the EPA sided with the Pentagon and agreed
to pull back the risk assessment. In 2004, the National Academy of Sciences was given a $680,000 contract to study the matter,
releasing its report in the summer of 2006. The report has
raised more concerns about the health effects of TCE.

In response to the heightened awareness of environmental toxins
such as TCE and the role they may be playing in childhood disease,
Sen. Obama proposed S1068, cosponsored by Hillary Clinton and
others. This legislation aims to inform and protect communities
that are threatened with environmental contamination. Sen.
Clinton's own bill, S1911, is known as the TCE Reduction Act. This
bill was co-sponsored by Sen. Elizabeth Dole (R-North
Carolina).

Reduced production and remediation

In recent times, there has been a substantial reduction in the
production output of trichloroethylene; alternatives for use in
metal degreasing abound, chlorinated aliphatic hydrocarbons being
phased out in a large majority of industries due to the potential
for irreversible health effects and the legal liability that ensues
as a result.

The U.S. military has virtually eliminated its use of the chemical,
purchasing only 11 gallons in 2005. About 100 tons of it is used
annually in the U.S. as of 2006.

Recent research has focused on the in-place remediation of
trichloroethylene in soil and ground water instead of removal for
off-site treatment and disposal. Naturally-occuring bacteria have
been identifed with the ability to degrade or completely mineralize
thrichloroethylene. Dehalococcoide sp. degrade
trichloroethylene by reductive dechlorination under anaerobic
conditions. Under aerobic conditions, Pseudomonas
fluorescence can cometabolize TCE. Soil and ground water
contamination by TCE has also been successfully remediated by
chemical treatment and extraction.

Further reading

Doherty, R.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. Journal of
Environmental Forensics (2000) 1, 83-93. link