Technical Factsheet on: 1,2-DICHLOROETHYLENE
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: cis-0.07; trans-0.1 mg/L
MCL: cis-0.07; trans-0.1 mg/L
HAL(child)- 1 day: cis-4; trans-20
: Longer-term: cis-3; trans-2
Health Effects Summary
Acute: EPA has found cis- and trans- 1,2-dichloroethylene to potentially cause central nervous
system depression from short-term exposures at levels above the MCL.
Short-term exposures in drinking water which are considered "safe" for a 10-kg (22 lb.) child
consuming 1 liter of water per day: for the cis form- a one-day exposure of 4 mg/L or upto a
7-year exposure to 3 mg/L. For the trans isomer: a one-day exposure of 20 mg/L or upto a 7-year
exposure to 2 mg/L.
Chronic: Both cis- and trans-1,2-DCE have the potential to cause liver, circulatory and nervous
system damage from long-term exposure at levels above the MCL. The trans isomer is
approximately twice as potent as the cis- isomer in its ability to depress the central nervous
system.
Cancer: There is inadequate evidence to state whether or not either cis- or trans-1,2-DCE have
the potential to cause liver cancer from a lifetime exposure in drinking water.
Usage Patterns
Both the cis and trans forms - usually as a mixture - are used as a solvent for waxes, resins, and
acetylcellulose; in the extraction of rubber; as a refrigerant; in the manufacture of
pharmaceuticals and artificial pearls and in the extraction of oils and fats from fish and meat; as a
chemical intermediate for making chlorinated compounds.
No data were available on recent production levels in the United States.
Release Patterns
Releases to the environment are expected to be limited to manufacturing plants in the Gulf
Region of the United States. Since cis-and trans-1,2-DCE are not listed chemicals in the Toxics
Release Inventory, data on releases during manufacture and handling are not available.
Trans-1,2-dichloroethylene may be released to the environment in air emissions and wastewater
during its production and use as a solvent and extractant, in organic synthesis, and in the
manufacture of perfumes, lacquers, and thermoplastics.
An assessment of the sources of trans-1,2-dichloroethylene is complicated by the fact that it is a
priority pollutant while the cis isomer is not and the standard EPA methods of analysis do not
allow the isomers to differentiated. This has resulted in monitoring reports erroneously listing the
trans isomer when the cis isomer is present. The Michigan Department of Health has the
capability of distinguishing these isomers and claims that it frequently finds the cis isomer and, if
concentrations are high, they occasionally find traces of the trans isomer.
Environmental Fate
Both the cis- and trans-1,2-dichloroethylenes may be released to the environment in air emissions
and wastewater during its production and use. Under anaerobic conditions that may exist in
landfills, aquifers, or sediment one is likely to find 1,2-dichloroethylenes that are formed as
breakdown products from the reductive dehalogenation of common industrial solvents
trichloroethylene, tetrachloroethylene, and 1,1,2,2-tetrachloroethane.
The cis-1,2-dichloroethylene is apparently the more common isomer found although it is
mistakenly reported as the trans isomer. The trans-isomer, being a priority pollutant, is more
commonly analyzed for and the analytical procedures generally used do not distinguish between
isomers.
If 1,2-dichloroethylenes are released on soil, it should evaporate and leach into the groundwater
where very slow biodegradation should occur.
If released into water, 1,2-dichloroethylenes will be lost mainly through volatilization.
In the atmosphere, 1,2-dichloroethylenes will be lost by reaction with photochemically produced
hydroxyl radicals and scavenged by rain. Because it is relatively long-lived in the atmosphere,
considerable dispersal from source areas should occur.
Biodegradation, adsorption to sediment, and bioconcentration in aquatic organisms should not be
significant.
Chemical/Physical Properties
CAS Number: cis- 156-59-2 trans- 156-60-5
Color/ Form/Odor: Colorless, odorless liquid
M.P.: cis- -80 C; trans- -50 C
B.P.: cis- 60.3 C; trans- 48 C
Vapor Pressure: cis- 273 mm Hg at 30 C; trans- 395 mm Hg at 30 C
Octanol/Water Partition (Kow): Log Kow = cis- 1.86; trans- 2.06
Density/Spec. Grav.: cis- 1.26 at 20 C trans- 1.28 at 20 C
Solubility: Soluble in water, cis- 3.5 g/L of water, trans- 6.3 g/L of water
at 25 C
Soil sorption coefficient: Kocs of cis and trans isomers are estimated at 36
to 49; high to very high mobility in soil
Odor/Taste Thresholds: N/A
Henry's Law Coefficient: cis- 0.00337 atm-cu m/mole; trans- 0.00672 atm-cu
m/mole
Bioconcentration Factor: BCFs of cis and trans isomers are estimated at 15
to 22; not expected to bioconcentrate in aquatic organisms.
Trade Names/Synonyms: Both isomers- 1,2-DCE, Acetylene dichloride; cis-
Z-1,2-dichloroethene; trans- E-1,2-dichloroethene, sym-dichloroethylene
Other Regulatory Information
Monitoring:
-- For Ground/Surface Water Sources:
Initial Frequency- 4 quarterly samples every 3 years
Repeat Frequency- Annually after 1 year of no detection
-- Triggers - Return to Initial Freq. if detect at > 0.0005 mg/L
Analysis
| Reference Source | Method Numbers |
|---|
| EPA 600/4-88-039 | 502.2; 524.2 |
Treatment/Best Available Technologies: Granular Activated Charcoal and Packed Tower
Aeration
For Additional Information
EPA can provide further regulatory or other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
Agency for Toxic Substances and Disease Registry - 404/639-6000
List of Contaminants
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