Advisory Opinion for Cis-I,2-Dichloroethylene
Off ice of Drinking Water
O.S. Environmental Protection: Agency
Washington, D.C» 20460
/AN OFFICE OF DRINKING WATER: HEALTH EFFECTS ADVISOR*
The Office of Drinking Water provides advice on health
effects upon requestr concerning unregulated contaminants
found in drinking water supplies. This information suggests
the level of a contaminant in drinking water at which ad-
verse health effects would not be anticipated. A margin of
safety is factored.in so as to protect the most sensitive
members of the general population. The advisories are
called Suggested No Adverse Response Levels (SNARLs).
SNARLs have been calculated by EPA and by the National
Academy of Sciences. (NAS) for selected contaminants in
drinking water* An SPA-SNARL and a NAS-SNARL may well
differ due to the possible selection of different experimen-
tal studies for use as the basis for the calculations. Fur-
thermore, NAS-SNARLs are calculated for adults while the
EPA-SNARLs are established for a 10 kg body weight child.
Normally EPA-SNARLs are provided for one-day, ten-day and
longer-term exposure periods where available data exist. A
SNARL does not condone the presence of a contaminant in
drinking water, but rather provides useful information to
assist in the setting of control priorities in cases where
contamination occurs. EPA-SNARLs are provided on a case-by-
case basis in. emergency situations such as spills, and acci-
dents.
In the absence of a formal drinking water standard for an
.identified drinking water contaminant, the Office of Drink-
ing Water develops EPA-SNARLs following the state-of-the-art
concepts in toxicology for non-carcinogenic risk for short
and longer term exposures. In cases where a substance has
been identified as having carcinogenic potential, a range of
estimates for carcinogenic risk based upon lifetime exposure
as developed by the HAS (1977 or 1980) and/or EPA Carcinogen
Assessment Group (EPA, 1980a) is presented. However, the
EPA-SNARL calculations for all exposures ignore the possible
carcinogenic risk that may result from these exposures* In
addition, EPA-SNARLs usually do not consider the health risk
resulting from possible synergistic effects of other
chemicals; in drinking water, food, and air.
EPA-SNARLs are not legally enforceable standards; they are
not issued as an official regulation, and they may or may
not lead ultimately to the issuance of national standards or
Maximum Contaminant Levels (MCLs). The latter must take
into account occurrence, relative source contribution
factors, treatment technology, monitoring capability, and
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costs, in addition to health effects* It is quite conceiv-
able that the concentration set for EPA-SNARL purposes might.
differ from an eventual MCL. The EPA-SNAALs may also change
as additional information becomes available. In short, EPA-
SNARLs. are offered as advice to assist those such as Region-
al and State environmental and health officials, local pub-
lic officials, and water treatment facility personnel who
are responsible for the protection of public health when
dealing with specific contamination situations.
General'Information and Properties
Cis-l,2-dichloroethylene is one of three isomers of
dichloroethylene, all clear, colorless liquids with the
molecular formula of C2H2C12 and a molecular weight bf
96.95 (Irish, 1963). It is moderately soluble in water (3.5
g/1 at 25°C) , but soluble in most organic solvents. The
cis-isomer has a vapor pressure of 208 Torr ( mm Hg) at 25°C
and a boiling point of 60*C. Its vapor density is 3.34,
over three times that of air, so that it will settle in low
places in a still atmosphere- Its specific gravity is 1.27
at 25°C. Thus, it also would tend to sink in a still body
of water.
Horsely (1947) lists a binary azeotrope with water (3.35%
water by weight, boiling at 55.3°C) and a ternary azeotrope
with water and ethanol (2.85% water, 90.5% cis-l,2-dichloro-
ethylene and 6.65% ethanol by weight, boiling at 53.8° C).
This* isomer also forms an azeotrope with ethanol or methanol
alone.
In air, one (1) ppm is equivalent to 3.97 mg/m3 and one
(1) mg/1 is equivalent to 252 ppm (Irish, 1963).
The existing threshold limit value (TLV) for the dichloro-
ethylenes in the United States is 200 ppm (794 mg/m3)
(ACGIH, 1977).
1,2-Dichloroethylene, as a mixture of the cis- and trans-
isomers, is used as a solvent for such substances as fats,
rubber, phenol and camphor and for retarding fermentation
(Windholz et al., 1976). It also is used as a low tempera-
ture extraction solvent for heat sensitive substances and
has been employed as a coolant in refrigeration plants
(Bardie, 1964).
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Sources'of Exposure
Cis-l,2-dichloroethylene has beea detected in a number of
raw and finished drinking waters, principally from ground
water sources. During the National Organics Reconnaissance
Survey (NORS), this isoraer was detected in Miami drinking
water at 16*0 ug/1 (U.S. EPA, 1975)» Concentrations of 0.1
ug/1 were observed in samples from Cincinnati and
Philadelphia; none was detected in drinking waters from the
other cities. '..,.-.....
Cis-l,2-dichloroethylene was detected at an average concen-
tration of 0.17 ug/1 in three of 105 raw surface waters
examined (2.9%) in a number of surveys (Coniglio, et al,
1980). An average of 0.66 ug/1 was detected in five of 103
samples (4.9%) of finished water from these surface water
supplies. Of 13 ground water samples collected in 13 cities
during- one or: more of several surveys (NORS, MOMS, or the
recent. SRI survey conducted for EPA), four (30.8%) of the
samples were positive for cis-l,2-dichloroethylene. Three
samples contained less than 1 ug/1; one sample contained 37
ug/1.,
Pellizzari (1978) found slightly higher levels of 1,2-
dichloroethylene (cis- and trans— isomers not distinguished)
than 1,1-dichloroethylene during his air sampling survey.
The maximum amount of 1,1-dichloroethylene measured was 2500
ng/m^ at Front Royal, Virginia. Maximum concentrations of
1,2-dichloroethylenes detected in various areas of the
United States varied from a trace (detection limit » 260
ng/nH or higher) near Magna, Utah, South Charleston, West
Virginia, and Grand Canyon, Arizona, to 5263 ng/ra3 at the
Kin-Buc Disposal Site in Edison, New Jersey (an industrial
site near an urban area).
No data are available on the presence of either isomer of
1,2-dichloroethylene in foodstuffs.
Pnarmacbkihetics -
Cis-l,2-dichloroethylene, as a neutral, low molecular
weight, lipid soluble material, should be systemically
absorbed following any route of administration.
No pharmacokinetic data appear to exist which define the
absorption rate of cis-l,2-dichloroethylene after oral
exposure. However, pharmacokinetic studies based on urinary
and biliary excretion data show that administration of a
single oral dose of 1,1-dichloroethylene (1 or 50 mgAg)
results in rapid and complete absorption in rats and mice
(McKenna, et air 1978b). Rapid absorption and distribution
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of 1,1-dichloroethylene after intraperitoneal administration
to rats also occurs (Jones and Hathway, 1978). For purposes
of SNARL development, then, we will assume that cis-1,2-
dichloroethylene is absorbed rapidly and completely after
oral exposure.
Hie absorption of gases from the lung is highly dependent
upon the blood:gas partition coefficient. Sato and NaJcajima
(1979) showed that cis-l,2-dichioroethylene has a blood:gas
partition coefficient of 9.2 in the rat. While it has a
high blood solubility, this chemical in air reaches a
steady-state within the whole rat in about 2 hours (Filser
and Bolt, 1979).
Distribution data on cis-l,2-dichloroethylene are not avail-
able. However, if this isomer follows the same distribution
pattern as that observed for 1,1-dichloroethylene, the
highest concentration would be found in the liver and kidney
(McKenna, et al, 1978a). These studies were performed in
rats, exposed by inhalation to concentrations varying from
10-2000 ppm C-v^40-8000 mg/m3) for 2 or 6 hours.
Bonse, et al. (1975) observed that metabolism of cis-1,2-
dichloroethylene in perfused rat liver produced detectable
amounts of dichloroethanol and dichloroacetic acid, possibly
indicating the initial formation of dichloroacetaldehyde.
Liebman and Ortiz (1977) have postulated the metabolic
pathways for cis-l,2-dichloroethylene. One proposed pathway
would be conversion to a reactive epoxide intermediate, then
to monochloroacetyl chloride and monochloroacetic acid. The
authors also suggested that the production of dichloroace-
taldehyde may occur by rearrangement of the glycol or the
epoxide with migration of a chloride ion. Their attempts to
identify a chromatographic peak as dichloroacetaldehyde were
inconclusive.
An essential feature of the metabolic pathway is that the
compound appears to be metabolized to an epoxide intermedi-
ate which is reactive and which may form covalent bonds with
tissue macromolecules (Henschler, 1977; Henschler and Bonse,
1977). These authors have synthesized chemically the epox-
ides for both isomers of 1,2-dichloroethylene; they believe
that these epoxides are formed in vivo during the metabolic
process. Each was inactive when tested for mutagenic
potential in a modified Ames system (Greim et al, 1975).
However, these results only added support to the hypothesis
of Henschler and co-workers that the epoxides with symmetri-
cal chlorines are more stable and less likely to be mutagen-
ic. This does not exclude the possibility that these
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symmetrical, epoxides may still interact with tissue macro-
molecules other than DNA, a process which may result in some
form of damage other than autagenesis or carcinogenesis.
There apparently are no published studies which test the
interaction of the isomers of 1, 2-dichloroethylene with DNA;
nor are there any which evaluate the interaction of these
two isomers with other tissue macromolecules .
No data concerning the excretion of cis-1, 2-dichloroethylene
are available. The rate of elimination of 1,1-dichloroethy-
lene is relatively rapid, with most of a dose being excreted
in the first, 24-72 hours after cessation of exposure* One
might assume that cis-1, 2-dichloroethylene would be elimina-
ted at a similar rate.
Health" fiffects
There are no published studies available to us at this time
which describe accidental, occupational or controlled expo-
sures to cis-1 r 2-dichloroethylene in humans by any route or
for any duration of exposure. At high concentrations (4000
ppm) central nervous system effects have been described from
unpublished data (Irish, 1963). This concentration was
estimated to be sufficient to rapidly produce a state
resembling drunkenness and was judged likely to result in
unconsciousness if exposure were continued.
Data on the toxicity of cis-1, 2-dichloroethylene in animals
are severely limited.. No LDso values for the cis- isomer
alone have been published. The lowest lethal oral dose for
the mixture in the human (70 kg) is estimated to be 500
(McBirney, 1954).
Jenkins, et al. (1972) tested the effects of single 400 or
1500 mg/kg oral doses of each isomer of dichloroethylene in
corn oil given to adult female Holtzman rats weighing
200-470 g. Liver and plasma enzyme activities were deter-
mined 20 hours after dosing. The cis- isomer appeared to
exert a more potent effect than did the trans- isomer at the
higher dose. No significant difference between the two iso-
mers was seen at the lower dose. Each was less potent than
1,1-dichloroethylene. At 400 mg/kg, cis-1, 2-dichloroethylene
significantly increased liver alkaline phosphatase to a*
level 10% above control (P < 0.05). At 1500 mgAg/ this
isomer significantly decreased the level of liver glucose-6-
phosphatase to about 88% of control (P < 0.05). Liver
tyros ine transaminase was decreased to 80% of control, and
plasma alanine transaminase to 14% of control (P < 0.05).
Plasma alkaline phosphatase was not altered. x
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In an animal study reporting on the central nervous system
•effect of the cis- isomer, the chemical, did not anesthetize
rats in 4 hours at 8000 pom (^-32,000 mg/m3), but at
16,000 ppm (/»^64,000 mg/m3), they were anesthetized in 8
minutes and killed within 4 hours (Irish, 1963).
Preundt, and Macholz (1978) showed that single 8-hour inhala-
tion exposures to cis-1,2-dichloroethylene at 20Qf 600 or
1000 ppm. (/"-'BOO, 2400 or 4000 mg/m3, respectively) concen-
trations resulted in a dose-dependent and significant in-
crease in hexobarbital sleeping time, zoxazolamine paralysis
time and the metabolic formation of 4-aminoantipyrine (AAP)
from aminopyrine in adult female Wistar rats. The effects
induced by the cis- isomer were more severe than those
induced by the trans- isomer* The authors attributed this
difference to the higher uptake of the cis- isomer by liver
tissue. The investigators concluded that the inhibition of
hepatic drug metabolism, as reflected in the change in AAP
levels, was caused by a competitive, reversible interaction
of, the chemical with the mixed function: oxidase system.
Teratbgehlcity
No reports on the teratogenic potential of cis-1,2-dichloro-
ethylene are available at the present time.
ftutagenicity
Both*cis— and trans-1,2-dichloroethylene were non-mutagenic
when assayed with E. coli K12 at similar concentrations used
for 1,1-dichloroetEylene at which the latter was found to be
mutagenic (Greim, et al, 1975). The medium concentration of
the cis-isomer was 2.9 mM, that of t-l,2-DCE was 2.3 mM, and
that of 1,1-DCE was 2.5 mM.
Both 1,1-dichloroethylene and cis-1, 2-dichloroethylene were
mutagenic in the host-mediated assay using Salmonella tester
strains in- mice (Gerna and Kypenova, 1977). Of the three
isomeric dichloroethylenes, only cis-1,2-dichloroethylene
produced chromosomal aberrations in bone marrow cells of
mice following repeated intraperitoneal injections (daily
injections at 1/2 LD$Q for five or ten days).
Carcinogenic!ty
No studies have been completed which test the carcinogenic
potential of cis-1,2-dichloroethylene. It is currently
under consideration by the National Toxicology Program.
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SNARL Development
One-day SNARL
There are few animal studies available which provide dose-
response data on the toxicity of cis-l,2-dichloroethylene
(Irish, 1963; Jenkins et al, 1972; Freundt and Macholz,
1973). Only the study by Jenkins and co-workers provides
information on what might be identified as a minimal effect
level. In measuring levels of three liver enzymes and two
plasma enzymes, indicators of liver function, these authors
showed that a single 400 mg/kg oral dose to the rat produced
a significant change only in liver alkaline phosphatase,
while the other enzyme levels were not significantly affec-
ted. This slight degree of liver involvement is felt not to
be life-threatening; evidence developed for 1,1-dichloro-
ethylene points to the fact that this degree of liver effect
appears to be quite rapidly and completely reversible once
exposure has ceased.
The Jenkins et al. results may be used to develop a one-day
SNARL. It would be derived thusly:
400 mg/kg x 10 kg x 100% « 4 mg/1
.1000 x 1
Where: 400 mg/kg * minimal effect dose
•
10 kg - weight of protected individual (child)
100% • percentage of dose absorbed
1000 * safety factor
1 * volume in liters of drinking water imbibed per
day by 10 kg child ,
Ten-day SNARL
A ten-day SNARL can be derived from the one-day SNARL which
will adequately protect the sensitive individual from
adverse health effects over that duration of exposure. As
stated above, any slight alteration in liver function is
felt to be quickly and readily reversible after cessation of
exposure.
A ten-day SNARL would be derived simply by dividing the one-
day SNARL by 10 to get 0.4 mg/1.
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8
Analysis
^^•MM^H^HM^^B^^B^" , • •
Cis-l,2-dichloroethylene and trans-l,2-dichloroethylene can
be analyzed by the purge-and-trap gas chromatographic proce-
dure used for the determination of volatile organohalides in
drinking waters (U.S. EPA, 198Ob; Bellar and Lichtenberg,
1979). In this procedure, volatile components are extracted
by an inert gas which is bubbled through the aqueous sample.
The compounds are swept from the purging device into a short
sorbent trap. After a predetermined period of time, the
trapped components are thermally desorbed and backflushed
onto the head of a gas chromatographic column where separa-
tion takes place.
The recommended primary columns for organohalide analysis do
not adequately resolve the cis- and trans-l,2-dichloroethy-
lene isomersv Therefore, it is suggested that the column
recommended for confirmatory analysis be used when these two
chemicals are being determined. The recommended chromato-
graphic conditions for the analysis are given belowr
Column: Six feet long x 0.1 inch ID stainless steel or
glass.
Packing; n — octane on Porisil - C (100/120 mesh).
Temperature; 50°C isothermal for 3 minutes, then program at
6'/minute to 170°C.
Carrier"gas? Helium at 40 ml/minute*
Detection; Hall model electrolytic conductivity or other
halogen specific detector.
Sample"volume; 5 ml.
The retention time for- the cis- isomer is 726 seconds and
for the trans- isomer is 563 seconds under the conditions
specified above. Confirmatory analysis of each isomer by a
second column or by GC-MS techniques is recommended. Al-
though the MS itself will not distinguish between cis- and
trans-l,2-dichloroethylene, the difference in GC retention
times will allow for proper identification.
The purge-and-trap procedure is applicable to the measure-
ment of most, organohalides over a concentration range of 0.1
to 1500 ug/1 when the Hall model electrolytic conductivity
detector is used. Other halogen specific detectors are
generally limited to measurements of 1.0 ug/1 or above.
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treatment
The best options for community systems to remove cis-1,2-
dichloroethylene appear to be granular activated carbon
(GAC), diffused or packed tower aeration/ and synthetic
resins. The preferred treatment needs to be evaluated on a
case-by-case basis* Pilot scale testing is essential to
estimate cost effectiveness since the quality of water may
greatly affect performance for each of the treatments*
Pilot scale data indicate that this compound is not as
easily removed by aeration (GAC or synthetic resins) as is
trichloroethylene or tetrachloroethylene.
Counter current diffused aeration, in a 30* diameter 10*
deep column, operating with a 10 minute contact time and an
air to water ratio of 30:1, removed 85% of cis-1,2-dichloro-
ethylene (present in groundwater at concentrations of 18-118
ug/1). At an air to water ratio of 5:1, and the same oper-
ating conditions, 58% cis-1,2-dichloroethylene was removed
from the same water. Counter current diffused aeration with
1.5 in. diameter columns, a 10 minute contact time and an
air to water ratio~of 4:1 removed 80% of the chemical in a
different groundwater sample containing 0.5 ug/1 of the
chemical. The performance of diffused aeration will be
affected by the design of the diffusers and matrix effects
(e.g., TOC and dissolved solids content). The extent to
which each of these effects performance has not yet been
evaluated.
Packed column aeration may be a more economical treatment
alternative than diffused aeration. However, no empirical
data are yet available to compare costs.
t
GAC with a bed depth of 2.5 ft and an Empty Bed Contact Time
(EBCT) of 6 minutes was used to treat a groundwater contain-
ing 25 ug/1 cis-1,2-dichloroethylene and 10 mg/1 TOC. Break-
through of the chemical (when concentrations in the effluent
exceeded .1 ug/1) occurred after 18 days of service or 4,300
bed volumes of throughput. The loading of cis-1,2-dichloro-
ethylene on the carbon at breakthrough was 0.3 mg/gm. Amber-
sorb XE-340, a synthetic resin, with the same bed depth and
EBCT, did not have breakthrough until after 60 days of
service or 14,400 bed volumes of throughput; the loading of
the chemical on the resin at breakthrough was 0.7 mg/gm.
The extent that service life of the adsorbent will be
affected by other organic substances competing for
adsorption sites is not yet known.
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10
In emergency situations,, or where funding is not available
for community treatment, boiling can be effectively used to
reduce cis-l,2-dichloroethylene concentrations to acceptable
levels. Ten minutes of boiling at a water depth of 8 cm.
should reduce concentrations of 150 ug/1 to 5 ug/1 or less.
Conclusions'and Recommendations , -
One-day and ten-day SNARLs of 4 mg/1 and 0.4 mg/1, respec-
tively, have been developed for cis-l,2-dichloroethylene.
At this time, no satisfactory dose-response, no-effect level
data exist from which a longer-term SNARL can be derived.
In addition, it would be preferable to have dose-response,
no-effect data for the one-day and ten-day SNARLs as well.
A grant has been awarded under the EPA Competitive Grants
program to study the toxicity of all three dichloroethylenes
and compare the percentage absorption via ingestion and
inhalation. Data from this study, which will include no-
effect, dose-response data, should be available in 1982. At
that time, the data will be reviewed and, if found suitable,
will form the basis for the revision of the existent SNARLs.
If the data are fpund lacking, further research will be
requested.
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11
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