1,1Dichloroethylene [factsheet]

1,1-DICHLOROETHYLENE

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literature and Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Air releases, primarily from emissions from polymer synthesis and fabrication industries, are the greatest source of ambient 1,1-dichloroethylene. (1)

* Occupational exposure to 1,1-dichloroethylene may occur by inhalation or dermal contact. (1)

* 1,1-Dichloroethylene has been detected at low levels in a number of drinking water supplies across the United States. (1)

Assessing Personal Exposure

* Measurable levels of 1,1-dichloroethylene can be detected in the breath, blood, urine, and body tissues. Determination of 1,1-dichloroethylene in breath samples by gas chromatography/mass spectrometry is the most commonly used method of monitoring exposure to 1,1-dichloroethylene. (1)

Health Hazard Information

Acute Effects:

* Limited human information indicate that relatively high concentrations of inhaled 1,1-dichloroethylene can induce adverse neurological effects including central nervous system depression and symptoms of inebriation, convulsions, spasms, and unconsciousness. (1,2)

* Inhalation of 1,1-dichloroethylene in humans causes respiratory effects, such as inflammation of mucous membranes. (1,2)

* Acute (short-term) animal tests, such as the LD₅₀ test in rats, have shown 1,1-dichloroethylene to have high toxicity from oral exposure, while the LC₅₀ test has shown 1,1-dichloroethylene to have moderate toxicity from inhalation exposure. (3)

Chronic Effects (Noncancer):

* 1,1-Dichloroethylene is possibly associated with liver and kidney toxicity after repeated low-level exposure in humans. (1,2)

* Considerable information from animal studies exist showing that long-term exposure to 1,1-dichloroethylene (inhalation and oral) causes effects on the lungs; gastrointestinal, cardiovascular and neurological systems; and the kidney and liver. (2,3)

* The RfD for 1,1-dichloroethylene is 0.009 mg/kg/day based on hepatic lesions in rats. (4)

* EPA has medium confidence in the study on which the RfD was based because it was conducted using appropriate numbers of animals of two species, measured several endpoints, and was of chronic duration; medium confidence in the database because there were corroborative chronic and subchronic oral bioassays; and, consequently, medium confidence in the RfD. (4)

* The RfC is currently under review by EPA. (4)

Reproductive/Developmental Effects:

* No studies were located regarding developmental or reproductive effects in humans. (1,2)

* Birth defects were noted in the offspring of pregnant rats that had been exposed to 1,1-dichloroethylene in air. (1,2) Maternal toxicity was also observed at developmentally toxic doses. (1)

Cancer Risk:

* No relationship between the occurrence of cancer in humans and occupational exposure to 1,1-dichloroethylene has been demonstrated. However, only three studies are available and these studies are limited by small population sizes and short observation periods. (1,2)

* One animal study has shown an increase in kidney and mammary tumors in mice exposed to 1,1-dichloroethylene via inhalation. Another drinking water study with rats has shown an increase in adrenal tumors in the male rats. (1,2)

* EPA considers 1,1-dichloroethylene to be a possible human carcinogen (cancer-causing agent) and has ranked it in EPA's Group C. (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 calculated an inhalation unit risk estimate of 5.0 H 10^-5 (m g/m³)^-1. EPA estimates that, if an individual were to breathe air containing 1,1-dichloroethylene 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 m g/m³ would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 2.0 m g/m³ would result in not greater than a one-in-ten thousand increased chance of developing cancer. (4)

* 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-dichloroethylene in the nonthreshold category. The 1/ED value of 1.2 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-Dichloroethylene is a colorless liquid with a mild sweet odor resembling that of chloroform. (1,6)

* The chemical formula for 1,1-dichloroethylene is C₂H₂Cl₂ and the molecular weight is 96.95 g/mol. (1,6)

* The vapor pressure for 1,1-dichloroethylene is 591 mm Hg at 25 EC and it has an octanol/water partition coefficient (log K_ow) of 2.13. (1)

* 1,1-Dichloroethylene has an odor threshold of 190 ppm. (7)

* 1,1-Dichloroethylene is practically insoluble in water. (1,6)

Uses

* 1,1-Dichloroethylene is used as an intermediate for organic chemical synthesis.

* 1,1-Dichloroethylene is also used in the production of polyvinylidene chloride copolymers. (1)

* The major application of these chloride copolymers is in the production of flexible films for food packaging (SARAN⁷ and VELON⁷ wraps). (1)

* These copolymers are also used extensively in many types of packing materials, as flame retardant coatings for fiber and carpet backing and in piping, coating for steel pipes, and adhesive applications. (2)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
100,000.0
_ _ _ _ 10,000.0	* LC₅₀ (rats) (25,177 mg/m³)		3
_ _ _ _ 1,000.0
_ _ _ _ 100.0
_ _ _ _ 10.0		* ACGIH STEL (79 mg/m³) * ACGIH TLV (20 mg/m³)	1,3 1,3
_ _ _ _ 1.0		* OSHA PEL (4 mg/m³)	1,3
_ _ _ _ 0.1
_ _ _ _ 0.01
_ _ _ _ 0.001
_ _ _ _ 0.0001

0.00001

* EPA Cancer Risk Level (1-in-a-million excess lifetime risk) = 2 H 10^-5 mg/m³

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.

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 1,1-Dichloroethene. (Draft). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1992.

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

3. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS). 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-Dichloroethylene. 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. The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.

7. 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.