1,1,2,2Tetrachloroethane [factsheet]

1,1,2,2-TETRACHLOROETHANE

Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on the carcinogenic effects of 1,1,2,2-tetrachloroethane including the unit cancer risk for inhalation exposure, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for 1,1,2,2-Tetrachloroethane. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Low levels of 1,1,2,2-tetrachloroethane can be present in both indoor and outdoor air. Average ambient air concentrations are around 0.005 ppb, and average concentrations in the indoor air of several homes measured 1.8 ppb. (1)

* 1,1,2,2-Tetrachloroethane has been detected in surface water and groundwater; however, a nationwide survey of drinking water supplies did not find any supplies containing 1,1,2,2-tetrachloroethane. (1)

* Occupational exposure to 1,1,2,2-tetrachloroethane may occur through inhalation of the vapors or through skin contact. (1)

Assessing Personal Exposure

* No specific medical tests are available to determine exposure to 1,1,2,2-tetrachloroethane. (1)

Health Hazard Information

Acute Effects:

* Acute (short-term) exposure to very high levels of 1,1,2,2-tetrachloroethane has caused death in humans; the autopsies revealed severe liver destruction. (1,2)

* Respiratory, neurological, and gastrointestinal effects have been noted from acute inhalation exposure in humans.

* Animal studies have observed effects on the liver, eyes, and central nervous system from acute inhalation exposure to 1,1,2,2,-tetrachloroethane. (1)

* Tests involving acute exposure of animals, such as the LC₅₀ and LD₅₀ tests in rats and mice, have shown 1,1,2,2-tetrachloroethane to have moderate acute toxicity. (3)

Chronic Effects (Noncancer):

* Chronic (long-term) exposure to 1,1,2,2-tetrachloroethane in humans and animals results in effects on the liver (jaundice and an enlarged liver) and central and peripheral nervous system (headaches, tremors, dizziness, and drowsiness). (1)

* EPA has not established an RfC for 1,1,2,2-tetrachloroethane. (4)

* The RfD for 1,1,2,2-tetrachloroethane is under review by EPA. (4)

Reproductive/Developmental Effects:

* No studies are available regarding developmental or reproductive effects in humans from inhalation or oral exposure to 1,1,2,2-tetrachloroethane. (1)

* Animal studies have not reported reproductive effects from inhalation exposure to 1,1,2,2-tetrachloroethane, while an oral study in rats reported histopathological changes in the testes. (1)

Cancer Risk:

* A slight increase in the incidence of death from genital cancers, leukemias, and other cancers was reported in a study that examined a group of army workers exposed to 1,1,2,2-tetrachloroethane by inhalation. However, this study is inconclusive because the increased cancer incidence was insignificant and other confounding factors may have been present. (1)

* Oral exposure to 1,1,2,2-tetrachloroethane in mice resulted in an increased incidence of liver tumors, while no increase in tumors was reported in rats. (1,4)

* EPA has classified 1,1,2,2-tetrachloroethane as a Group C, possible human carcinogen. (4)

* EPA uses mathematical models, based on animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA has calculated an inhalation unit risk estimate of 5.8 H 10^-5 (m g/m³)^-1. EPA estimates that, if an individual were to breathe air containing 1,1,2,2-tetrachloroethane at 0.02 Fg/m³* over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing air containing 0.2 Fg/m³ would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 2.0 Fg/m³ would result in not greater than a one-in-ten thousand increased chance of developing cancer. (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 1,1,2,2-tetrachloroethane in the nonthreshold category. The 1/ED₁₀ value is 1.7 per (mg/kg)/d and this would place it in the low category under Superfund's ranking for carcinogenic hazard. (5)

Physical Properties

* 1,1,2,2-Tetrachloroethane is a colorless, dense liquid that has a sweet, chloroform like odor. (6)

* The odor threshold for 1,1,2,2-tetrachloroethane is 1.5 ppm. (6)

* The chemical formula for 1,1,2,2-tetrachloroethane is C₂H₂Cl₄, and the molecular weight is 167.85 g/mol. (2)

* The vapor pressure for 1,1,2,2-tetrachloroethane is 5.95 mm Hg at 25 EC, and it has a log octanol/water partition coefficient (log K_ow) of 2.39. (1)

Uses

* 1,1,2,2-Tetrachloroethane is used to produce trichloroethylene, tetrachloroethylene, and 1,2,-dichloroethylene. (1)

* Other uses include as a solvent, in cleaning and degreasing metals, in paint removers, varnishes and lacquers, in photographic films, and as an extractant for oils and fats. (1)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
10,000.0
_ _ _ _ 1,000.0	* LC₅₀ (mice) (4,500 mg/m³)		3
_ _ _ _ 100.0
_ _ _ _ 10.0
_ _ _ _ 1.0
_ _ _ _ 0.1		* OSHA PEL, ACGIH TLV and NIOSH REL (7 mg/m³)	1
_ _ _ _ 0.01
_ _ _ _ 0.001
_ _ _ _ 0.0001
_ _ _ _ 0.00001	* EPA Cancer Risk Level^c (1-in-a-million excess lifetime risk) = 2 H 10^-5 mg/m³		4

See notes on following page.

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.

^c These cancer risk estimates were derived from oral data and converted to provide the estimated inhalation risk.

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for 1,1,2,2-Tetrachloroethane (Draft). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1987.

2. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

3. 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.

4. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on 1,1,2,2-Tetrachloroethane. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.

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.