Trichloroethylene [factsheet]

TRICHLOROETHYLENE

Please Note: The main source of information for this fact sheet is the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Trichloroethylene. Other secondary sources include the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed, and EPA's Health Assessment Document for Trichloroethylene.

Environmental/Occupational Exposure

* Trichloroethylene has been detected in ambient air at levels less than 1 ppb. (1)

* Drinking water supplies may contain trichloroethylene; a recent monitoring study found average trichloroethylene levels of 1 ppb in drinking water using groundwater as a source. (1)

* Workers may be exposed to trichloroethylene in the factories where it is manufactured or used. In addition, persons breathing air around these factories may be exposed to trichloroethylene. (1)

* Persons may also be exposed to trichloroethylene through the use of products containing the chemical and from evaporation and leaching from waste disposal sites. (1)

Assessing Personal Exposure

* Trichloroethylene can be measured in the breath, and breakdown products of trichloroethylene can be measured in urine or blood. (1)

Health Hazard Information

Acute Effects:

* Acute (short-term) exposure to very high levels of trichloroethylene (approximately 10,000 ppm) in humans has caused death. A few of these reports have cited cardiac arrhythmias as the cause of death, and one report noted massive liver damage. (1)

* Central nervous system effects are the primary effects noted from acute inhalation exposure to trichloroethylene in humans, with symptoms including sleepiness, confusion, and feelings of euphoria. Effects on the gastrointestinal system, liver, kidneys, and skin have also been noted. (1)

* Trichloroethylene absorption by inhalation, dermal, and oral exposure is very rapid. Trichloroethylene is metabolized in humans and animals to a number of substances which themselves are known to be toxic: chloral hydrate, trichloroacetic acid, dichloroacetic acid, and trichloroethanol.

* Tests involving acute exposure of animals, such as the LC₅₀ and LD₅₀ tests in rats and mice, have shown trichloroethylene to have low toxicity from inhalation exposure and moderate toxicity from oral exposure. (1,2)

Chronic Effects (Noncancer):

* Chronic (long-term) exposure to trichloroethylene by inhalation in humans also results in central nervous system effects. Case reports have reported effects such as dizziness, headache, sleepiness, nausea, confusion, blurred vision, facial numbness, and weakness at concentrations around 100 ppm. (1)

* Studies have shown that alcohol consumption in humans increases the toxicity of trichloroethylene. (1)

* The RfC and RfD for trichloroethylene are under review by EPA. (3)

Reproductive/Developmental Effects:

* One study found increases in miscarriages in nurses exposed to trichloroethylene and other chemicals in the workplace, although no specific association with trichloroethylene was found. Another study found no increase in malformations in babies of 2,000 fathers and mothers exposed to trichloroethylene in the workplace via inhalation. (1)

* An association (but no cause-and-effect relationship) was found between elevated levels of chlorinated hydrocarbons, including trichloroethylene, in drinking water and congenital heart disease in children of exposed parents. (1)

* Several studies have not reported adverse reproductive effects in humans exposed to trichloroethylene in drinking water. (1)

* One study reported an increase in abnormal sperm morphology in mice exposed to trichloroethylene by inhalation, while other animal studies did not report developmental effects from inhalation or oral exposure to trichloroethylene. (1,4)

Cancer Risk:

* Several human studies have investigated the relationship between inhalation exposure to trichloroethylene and cancer. These studies did not find significant increases in cancer incidence, but they are limited by lack of exposure data and small sample size. (1,4)

* One human study reported that there was a potential association between drinking water contaminated with trichloroethylene and an increased risk of childhood leukemia. Other studies reexamined the data and did not agree with the association because the people were exposed to chemicals other than trichloroethylene, and the statistical significance of the incidence of leukemia has not been resolved. (1)

* Animal studies, via inhalation exposure, have reported increases in lung, liver, and testicular tumors and increases in liver tumors via gavage (experimentally placing the chemical in the stomach). (1,4)

* EPA has classified trichloroethylene as a Group B2/C, probable human carcinogen. (5)

* EPA's Office of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has ranked trichloroethylene in the nonthreshold category. The 1/ED₁₀ value is 0.035 per (mg/kg)/d and this would place it in the low category under Superfund's ranking for carcinogenic hazard. (5)

Physical Properties

* Trichloroethylene is a nonflammable colorless liquid with an odor similar to ether or chloroform. (1)

* The odor threshold for trichloroethylene is 28 ppm. (6)

* The chemical formula for trichloroethylene is C₂HCl₃, and the molecular weight is 131.40 g/mol. (1)

* The vapor pressure for trichloroethylene is 60 mm Hg at 20 EC, and it has a log octanol/water partition coefficient (Log K_ow) of 2.42. (1)

Uses

* Trichloroethylene is used as a degreaser of metal parts, an extraction solvent for greases, oils, fats, waxes, and tars, a chemical intermediate in the production of other chemicals, and as a refrigerant. (1)

* Trichloroethylene is used in products such as typewriter correction fluids, paint removers/strippers, adhesives, spot removers, and rug-cleaning fluids. (1)

* Trichloroethylene was used in the past as a general anesthetic. (1)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
1,000,000.0
_ _ _ _ 100,000.0
_ _ _ _ 10,000.0	* LC₅₀ (rat) (67,178 mg/m³) * LC₅₀(mouse) (45,412 mg/m³)		1,2 1,2
_ _ _ _ 1,000.0		* OSHA PEL and ACGIH TLV (STEL) (1,080 mg/m³)	7
_ _ _ _ 100.0		* OSHA PEL and ACGIH TLV (270 mg/m³) * NIOSH REL (134 mg/m³)	7 7

ACGIH STELCAmerican Conference of Governmental and Industrial Hygienists' short-term exposure limit; 15-min time-weighted-average exposure that should not be exceeded at any time during a workday even if the 8-h time-weighted-average is within the threshold limit value.

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.

LC₅₀ (Lethal Concentration₅₀)CA calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

NIOSH RELCNational Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Trichloroethylene. U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1993.

2. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

3. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Trichloroethylene. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.

4. U.S. Environmental Protection Agency. Health Assessment Document for Trichloroethylene. EPA/600/8-82/006F. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development. 1985.

5. U.S. Environmental Protection Agency. Technical Background Document to Support Rulemaking Pursuant to the Clean Air ActCSection 112(g). Ranking of Pollutants with Respect to Hazard to Human Health. EPAB450/3-92-010. Emissions Standards Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.

6. J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.

7. E.J. Calabrese and E.M. Kenyon. Air Toxics and Risk Assessment. Lewis Publishers, Chelsea, MI. 1991.