Technical Factsheet on: 1,1-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: 0.007 mg/L
MCL: 0.007 mg/L
HAL(child): 1 day: 2 mg/L; Longer-term: 1 mg/L
Health Effects Summary
Acute: EPA has found 1,1-dichloroethylene to potentially cause adverse
liver effects due to acute exposures at levels above the MCL.
Drinking water levels which are considered "safe" for short-term exposures:
For a 10-kg (22 lb.) child consuming 1 liter of water per day: a one-day
exposure of 2 mg/L; upto a 7-year exposure to 1 mg/L.
Chronic: Chronic exposure to 1,1-dichloroethylene at levels above the
MCL has the potential to cause liver and kidney damage, as well as toxicity
to the developing fetus.
Cancer: There is some evidence that 1,1-dichloroethylene may have the
potential to cause cancer at levels above the MCL.
Usage Patterns
An estimated 90,700 tons/yr of the monomer were produced in the USA
during the early 1980s. Virtually all of the 1,1-dichloroethylene produced
is used in the production of copolymers with vinyl chloride or acrylonitrile.
A small percentage (4%) of 1,1-dichloroethylene is used as chemical intermediates.
These products are then used in adhesives, synthetic fibers, refrigerants,
food packaging and coating resins such as the saran types.
Release Patterns
1,1-Dichloroethylene may be released into the environment as emissions
or in wastewater during its production and use in the manufacture of plastic
wrap, adhesives, and synthetic fiber.
1,1-Dichloroethylene is formed by a minor pathway during the anaerobic
biodegradation of trichloroethylene and also by the hydrolysis of 1,1,1-trichloroethane.
Therefore there is a potential for it to form in groundwater that has
been contaminated by chlorinated solvents.
1,1-Dichloroethylene is also produced by the thermal decomposition of
1,1,1-trichloroethane, a reaction that is catalyzed by copper. 1,1,1-Trichloroethane
is used as a degreasing agent in welding shops so there is a potential
for 1,1-dichloroethylene to be formed in these shops as well as in other
industrial environments where 1,1,1-trichloroethane is used near sources
of heat.
From 1987 to 1993, according to the Toxics Release Inventory, releases
to water totalled over 10,000 lbs. Releases to land totalled about 1,500
lbs. These releases were primarily from facilities classified as producing
alkalies/chlorine and plastics materials/resins. The largest releases
occurred in Kentucky.
Environmental Fate
Releases to water will primarily be lost to the atmosphere through evaporation.
The mass transfer coefficient between water and the atmosphere of 1,1-dichloroethylene
relative to oxygen has been measured to be 0.62. Using data for the oxygen
re-aeration rate of typical bodies of water, one can calculate the half-life
for evaporation of 1,1-dichloroethylene to be 5.9, 1.2 and 4.7 days from
a pond, river and lake, respectively. In water, the photooxidation of
1,1-dichloroethylene is insignificant. A hydrolysis half-life of 6-9 months
has been observed with no significant difference in hydrolysis rate between
pH 4.5 and 8.5. This value differs markedly from the estimated hydrolytic
half-life of 2 yr at pH 7.
If spilled on land, part of the 1,1-dichloroethylene will evaporate
and part will leach into the groundwater where its fate is unknown, but
degradation is expected to be slow based upon microcosm studies. No experimental
data is available on the adsorption of 1,1-dichloroethylene. A low Koc
of 150 are calculated from a regression equation based on its octanol/water
partition coefficient (log Kow= 1.48).
Once in the atmosphere it will degrade rapidly by photooxidation with
a half-life of 11 hours in relatively clean air or under 2 hours in polluted
air.
Few studies on the biodegradation of vinylidene could be found In one
study, 45-78% of the chemical was lost in 7 days when incubated with a
wastewater inoculum; however, a sizeable fraction of the loss was due
to volatilization. 97% of 1,1-dichloroethylene was reported to be removed
in a municipal wastewater plant but again the fraction lost by evaporation
is unknown.
Under anaerobic conditions in microcosms designed to simulate the anaerobic
conditions in groundwater and landfills, 1,1-dichloroethylene undergoes
reductive dechlorination to vinyl chloride. In the microcosms designed
to simulate a groundwater environment, 50% of the 1,1-dichloroethylene
disappeared in 5-6 mo.
Under the simulated landfill conditions, degradation occurred in 1-3
weeks. In another anaerobic biodegradation study that used materials from
an aquifer that receive municipal landfill leachate and is known to support
methanogenesis, the 1,1-dichloroethylene disappeared in 40 weeks. However,
no significant degradation occurred for 16 weeks. 1,1-Dichloroethylene
was formed as a degradation product.
No experimental data could be found on the bioconcentration of 1,1-dichloroethylene
in fish or aquatic invertebrates. Based on its low octanol/water partition
coefficient (log Kow= 1.48) one would not expect any significant bioconcentration.
The general population may be exposed to low levels of 1,1-dichloroethylene
in ambient air, indoor air, contaminated drinking water, and food which
has come in contact with plastic wrap which contains residual monomer.
Chemical/Physical Properties
CAS Number: 75-35-4
Color/ Form/Odor: Colorless liquid with a mild, sweet, chloroform-like
odor
M.P.: -122.5 C B.P.: 31.7 C
Vapor Pressure: 591 mm Hg at 25 C; highly volatile
Octanol/Water Partition (Kow): Estimated log Kow= 1.32
Density/Spec. Grav.: 1.213 at 20 C
Solubilities: 2.5 g/L of water at 25 C
Soil sorption coefficient: Koc estimated at 150
Odor/Taste Thresholds: N/A
Bioconcentration Factor: N/A; not expected to bioconcentrate in fish.
Henry's Law Coefficient: N/A
Trade Names/Synonyms: 1,1-DCE; 1,1-Dichloroethene; Asym-dichloroethylene;
Vinylidene chloride;
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
Toxic Release Inventory - Releases to Water and Land, 1987 to 1993
(in pounds):
| |
Water |
Land |
| TOTALS (in pounds) |
10,101 |
1,488 |
| Top States |
| KY |
2,880 |
286
|
| TX |
2,061 |
150
|
| LA |
2,079 |
3
|
| Major Industries |
| Plastics materials, resins |
3,942 |
1,299
|
| Alkalies, chlorine |
4,173 |
154
|
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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