J"T
27753 ' "'^ * * **
DRAFT CRITERIA DOCUMENT
FOR TRICHLOROETHYLENE
FEBRUARY 1984
HEALTH EFFECTS BRANCH
CRITERIA AND STANDARDS DIVISION
OFFICE OF DRINKING WATER
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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PREFACE
27953
The objective of this document is to assess the health
effect information of the contaminant trichloroethylene in drink-
ing water and to recommend a maximum contaminant level. To
achieve this objective, data on pharmacokinetics, assessment of
human exposure, acute and chronic health effects in animals,
human health effects including epidemiology and mechanisms of
toxicity were evaluated. Only the reports which were con-
sidered pertinent for the derivation of the maximum contaminant
level are cited in the document. Particular attention was paid
toward the utilization of primary references for the assessment
of health effect. Secondary references were used rarely. For
comparison, standards and criteria developed by other organiza-
tions are included in Section IX, Quantification of Toxicological
Effects, and are discussed.
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TABLE OF CONTENTS
PAGE
I . SUMMARY 1-1
II. INTRODUCTION II-l
III. PHARMACOKINETICS III-l
IV. ASSESSMENT OF HUMAN EXPOSURE
TO TRICHLOROETHYLENE (To be developed later)
V. ACUTE AND CHRONIC HEALTH EFFECTS
IN ANIMALS „• .V-1
A. Hepatotoxicity V-l
B. Nephrotoxicity V-3
C. Nervous System V-4
D. Cardiovascular Effects V-6
E. Teratogenicity
F. Mutagenicity
G. Carcinogenicity V-9
VI. HUMAN HEALTH EFFECTS VI-1
A. Acute Exposures VI-1
B. Chronic Exposures • VI-5
C. Epidemiologic Studies Vl-10
VII. MECHANISMS OF TOXICITY VII-1
VIII. RISK ASSESSMENT VIII-1
IX. QUANTIFICATION OF TOXICOLOGICAL EFFECTS IX-1
X. REFERENCES X-l
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I. SUMMARY
Trichloroethylene, Cl^C » CHC1, is a colorless solvent
It has been used as a degreasing solvent in metal industries
and in drycleaning shops and as an inhalation anaesthetic
during certain short-term surgical procedures.
The widespread use of trichloroethylene has resulted
in its detection in airf in food and in human tissues. It has
also been detected in the surface as well as ground water
supplies of several states across the Continent of the
United States.
On ingestion, either from food or in drinking water,
trichloroethylene is expected to be readily absorbed from the
gastrointestinal tract and enter the blood stream. After
entering the blood stream, it distributes into various tissues
and organs. The extent of distribution depends largely on
the fat content of the tissues. Trichloroethylene may be
transported across placental barriers in pregnant women.
Trichloroethylene is metabolized to monochloroacetic
acid, trichloroacetaldehyde (chloral), trichloroethanol,
trichloroacetic acid and trichloroethanol glucuoronide. There
is strong evidence that trichloroethylene is metabolized
to the above-mentioned metabolites via an epoxide inter-
mediate—2,2,3-trichlorooxirane. This intermediate is
thought to be responsible for the mutagenic and carcinogenic
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1-2
potential of trichloroethylene. However, interaction of the
epoxide with the nuclear material—a step towards carcino-
genesis—has not been studied. It is noteworthy that TCE-
epoxide does bind with tissue macromolecules. This is
characteristic of other carcinogens.
Among the acute and chronic adverse effects in
animals, hepatotoxicity appears to be of importance.
Nephrotoxic effects have a'lso been reported in rats and mice.
At very high dosages, it depresses myocardial contractility.
The teratogenic and reproductive effects of trichloroethylene
need to be substantiated. There are two reports on the
teratogenic effects of trichloreothylene. These reports
indicated no tetratogenic abnormalities in mice or rats.
Trichloroethylene is mutagenic in bacterial test
system, utilizing liver microsomal fractions for activation.
Trichloroethylene was found carcinogenic in B^C^FI strain mice;
however, it was not carcinogenic in Osborne-Mendel rats. The
validity of the study was questioned because carcinogenic impuri-
ties were detected in the test compound. In a repeat experiment
with pure TCE, it was again found to be carcinogenic in
mice.
Central nervous system, cardiotoxic, hepato- and
nephrotoxic effects have been reported in humans exposed to
trichloroethylene in workplace, inhalation-abuse and by
accidental ingestion. The reports are clouded by the fact
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1-3
that the subjects were exposed either to the contaminated
trichloroethylene and/or to its decomposition products. However,
some of the effects have been observed in animals under
experimentally controlled conditions with reasonably pure
trichloroethylene. Furthermore, dose-response relationships
have been observed.
Based on the mechanism of toxicity—specifically
mutagenesis and carcinogenesis—trichloroethylene, has the
potential of being carcinogenic. TCE has been reported to bind
with mouse liver DNA in an in vivo experiment. Covalent binding
of calf thymus DNA with TCE in an jji vitro experiment, further
provides support to the carcinogenic potential of TCE.
The National Academy of Sciences (NAS) and EPA's
Carcinogen Assessment Group (CAG) have calculated projected
incremental excess cancer risks associated with the consumption
of a specific chemical via drinking water by mathematical
extrapolation from high-dose animal studies (Table 1-1). Using
the risk estimates generated by the NAS (1977-1979) where the
multi-stage model was utilized, that range of trichloroethy-
lene concentrations was computed which would nominally increase
the risk of one excess cancer per million (106), per hundred
thousand (105) and per ten thousand (104) people over a 70-year
lifetime assuming daily consumption at the stated exposure level
From the NAS model it is estimated that, at the 95% confidence
limit, consuming two liters of water having trichloroethylene
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1-4
concentrations of 450 ug/1, 45/1 or 4.5 ug/1 per day over a
lifetime, would increase the risk of one excess cancer per
10,000, 100,000 or 1,000,000 people exposed, respectively.
Using the revised CAG approach and thus the "improved" multi-
stage model, it can be estimated at the 95% confidence limit
that consuming two liters of water having trichloroethylene
concentrations of 280 ug/1, 28 ug/1 or 2.8 ug/1 per day over
a lifetime, would increase the risk of one excess cancer per
10,000, 100,000 or 1,000,000 people exposed, respectively.
The numerical differences observed after utilizing the NAS and
the CAG risk estimates are partly due to the fact that the dose
extrapolation model used by the two groups is similar but not
identical. The NAS has used the multi-stage model whereas the
CAG has used the "improved" version of the multi-stage model
recently discussed by Crump (U.S. EPA, 1980). In addition, the
selection of the data and other parameters in each model will
also result in some differences.
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1-5
Table 1-1
Drinking Water Concentrations and Associated Cancer Risks
Range of Concentrations (ug/1)*
CA3 NAS NAS
Excess Lifetime (95% confidence (95% confidence (point estimate)
Cancer Risk limit) limit)
280 450 1400-450
lcr5 28 45 140-45
10-* 2.8 4.5 14-4.5
*Assume 2 liters of water are consumed per day.
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II. INTRODUCTION
Trichloroethylene (1,1,2-trichloroethylene; TCE),
C2HC13* is a clear colorless liquid, used mainly as a degreas-
ing solvent in metal industries. TCE is also used as a
household and industrial dryclefening solvent, an extractive
solvent in foods, and an inhalation anesthetic during certain
short-term surgical procedures {Huff, 1971).
TCE has a molecular weight of 131.4; is non-
flammable; has chloroform-like order; d20 1.4649 bp?60 86.7";
vapor density, 4.53 (air = 1.00) (Windholz, 1976); 1 ppm in
air at 25° C is equivalent to 5.45 mg/m3; odor threshold 0.5
n»g/kg water (Van Gemert and Nettenbreijer, 1977).
The solvent used in industry before the mid-1960's
contained impurities, such as 1,1,2,2-tetrachloroethane, and
some of the stabilizers, such as epichlorhydrin. A more
pure product was obtained in the early 1960's, because a
change was made in the manufacturing process (MRI, 1979).
The US produced approximately 234,000 metric tons a
year (40 FR 48907 - October 1975). TCE volatilization
during production and use is the major source of environmental
levels of this compound. TCE has been detected in air, in
water, and in marine organisms.
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II-2
Its detection in rivers, municipal water supplies, the sea,
and aquatic organisms indicates that TCE is widely distributed
in the aquatic environment. The authors concluded that it
is not persistent in the environment and that there is no
significant bioaccumulation in marine food chains (Pearson
and McConnell, 1975).
Recently, TCE has been detected in the groundwater
of several states across the continent of the United States.
Region III, U.S. EPA, reported high concentrations of TCE in
Pennsylvania and Delaware at several locations. The concen-
tration of TCE in these waters ranged from 18 ppb to 22,000
ppb. How TCE entered groundwater in these areas has not been
determined.
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III. PHARAMACOKINETICS
Absorption
Several reports indicate that TCE is absorbed into
the bloodstream by all the three routes of entry—inhalation,
oral and dermal. However, information on the quantitative
aspects of TCE absorption is limited.
Soucek and Vlachova (£960) exposed three men and two
women of an average age of 21 years to trichloroethylene.
vapors for 5 hours in an exposure chamber. The concentrations
of TCE used in these experiments were: 500, 850, 820, and
830 ug/1. The concentration of the trichloroethylene retained
by the test subjects was calculated by subtracting the levels
of TCE in the expired air from the concentrations in the
exposure chamber. The method of analysis of TCE was not
described. The authors calculated that the body retains an
average 65% of inhaled TCE. Soucek et al. (1952) recorded
a range between 51% and 64%, with an average of 58%.
Data on ingestion of TCE are limited. Several reports
concern the accidental ingestion of TCE that resulted in
poisoning (Kleinfeld & Tabershaw, 1954; Gibitz and Ploechal,
1973). These reports provide evidence that TCE is absorbed
via the gastrointestinal tract. Quantitative absorption
data are not available.
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III-2
Stewart and Dodd (1964) demonstrated that the alveo-
lar breath concentration from skin exposure to TCE was only
0.5 ppm after subjects had immersed their thumb in a beaker
containing the compound for 30 minutes. Using alveolar
breath levels to measure absorption and assuming no body
retention, the authors stated that unless TCE was trapped
against the skin, it was not absorbed in any significant
quantities. Frant and Westendorp (1950) showed that when a
volunteer's hands had been dipped into the solvent for 1-0
minutes, absorption through the skin was of minor importance
and that 3 days later the trichloroacetic acid content in
the urine was found to be only 1.5 mg/1. To insure that the
only mode of entry of TCE was through the skin the subject
wore a protective gas mask during the experiment. Schwander
(1936) demonstrated that TCE penetrated the skin of rabbits
and was detected in the expired air.
Distribution
After absorption, TCE enters the blood and is
distributed to the various tissues and organs. Most of the
data on tissue levels have been obtained through inhalation
studies. There are no data available on disposition of ingested
TCE, although there is substantial evidence that TCE after
ingestion enters the bloodstream.
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III-3
Kulkarni (1944) determined TCE blood and tissue levels
of dogs, rabbits, guinea pigs and cats after exposure to TCE
vapors. The lethal TCE blood concentration in dogs was
found to be 100-110 mg per 100 ml blood; for chloroform
anesthesia, it was 60-65 mg/100 ml blood. At the anesthetic
stage, TCE blood levels were 24-37, 23-28, 14-18 and
25-32 mg/100 ml blood for dogs, rabbits, guinea pigs and
cats, respectively. The blood-brain ratio at anesthetic
dosages was approximately 1:2 for both guinea pigs and dogs.
Guinea pigs and rats were used by Fabre and Truhaut (1952) to
determine how TCE vapors distributed to the tissues. Guinea
pigs were exposed to 600-900 mg/m3 for 5-23 days (4.5-5.25
hrs/day). Biological effects, per se, were not evaluated
in this study. Rather, tissue distribution was assessed.
However, a trend for distribution of TCE in this study can be
observed. TCE was present in most of the examined tissues;
the greatest concentrations were in fat, followed by adrenals,
ovaries, kidneys, lungs, brain and liver. A metabolite,
trichloroacetic acid, was found in the greatest concentrations
in the adrenals, ovaries, spleen, kidneys, lungs, adipose
tissue and the brain. After acute exposure to TCE, the greatest
amount of trichloroacetic acid was present in the spleen.
After repeated exposure, the largest amount of acid was present
in the lungs.
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III-4
To study the effect of embalming on TCE tissue con-
centration, Stewart et al. (1964) administered 1 and 2 ml TCE
orally to dogs, weighing 8 and 10.2 kg, respectively. The
animals were sacrificed 16 hours after exposure and the tissue
levels were determined four, ten and 21 days later, utilizing
gas chromatographic technique. Omental fat contained highest
level of TCE.
TCE tissue distribution in humans has been studied
by several investigators (Powell, 1945; Astrand and Ovrum,
1976; Versterberg and Astrand, 1976; Clayton and Parkhouse,
1962; Laham, 1970 and Beppu, 1968). These data were collected
both from patients under anesthesia and from autopsies of human
subjects. As with animals, inhaled TCE vapors are readily
absorbed into the bloodstream of humans.
In an inhalation study by Powell (1945), 12 patients
(during anesthesia) were exposed to 1.5 to 2,5 vol. % TCE
for at least one half-hour. Concentrations in venous blood
varied between 6.5 and 12.5 mg (100 ml). The blood concentra-
tion was reduced to 1 mg % within 3 hours and to 0.1 mg %
within 24 hours. However, lower TCE blood concentration
[2.8+1.14 mg/100 ml] was reported in women after TCE
anesthesia during vaginal deliveries. These women inhaled
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III-5
TCE vapors for an average time period of 34.7 minutes (Beppu,
1968). When the inhalation time for TCE anesthesia was reduced
to 10-19 minutes, maternal venous blood ranged from 0.67-8 mg
TCE per 100 ml blood (Laham, 1970). Clayton and Parkhouse
(1962) recorded 2.2-11.3 mg TCE per 100 ml in venous blood of
subjects who inhaled 0.5 to 1.0 TCE concentration volume/volume
percent for 20-25 minutes.
TCE is readily transported from mother to fetus.
Beppu (1968) noted that TCE may be transported across placental
barriers in pregnant women. The mean inhalation time of thirty-
four subjects was 34.7 minutes; the mean concentration of TCE
was 2.80+1.14 mg/100 in the femoral (cubital) arteries of
mothers, 2.36+1.17 mg/100 ml in the cubital veins of mothers
and 1.83+1.08 mg/100 ml in the umbilical veins and 1.91+0.95
mg/100 ml in the umbilical arteries. The concentration of TCE
in fetal blood was lower than that of the mother's blood.
Laham (1970) obtained similar results from studies on placental
transfer of trichloroethylene. Ten case studies involving
women between 20-28 years were reported. Intermittent inhala-
tion technique was used for producing anesthesia. Duration of
inhalation was between 10 and 19 minutes. Material venous
blood contained 0.67-8 mg trichloroethylene per 100 ml of
blood, whereas fetal blood concentrations of trichloroethylene
ranged from 1-5.20 mg/100 ml.
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III-6
TCE has been detected in human tissues. Specimens
from eight humans were examined post-mortem by McConnell
et al. (1975) and found to contain TCE in the body fat, liver,
kidney and brain tissue samples, indicating uptake by these
tissues (Table I1I-1).
Table III-l
Occurrence of Trichloroethylene in Human Tissue
Age of
Subject Sex
76 F
76 F
82 F
48 M
65 M
75 M
66 M
74 F
Tissue
Body fat
Kidney
Liver
Brain
Body fat
Kidney
Liver
Brain
Body fat
Liver
Body fat
Liver
Body fat
Liver
Body fat
Liver
Body fat
Body fat
ug/kg
32
<1
5
1
2
3
2
<1
1.4
3.2
6.4
3.5
3.4
3.5
14.1
5.8
4.6
4.9
Post-mortem samples taken from subjects of unreported work
history or trichloroethylene exposure, who had lived in north-
western England? isolation accomplished by solvent extraction
and column chromatography; samples analyzed by gas-liquid
chromatography using an electron capture detector with confir-
mation by mass spectroscopy (Source: McConnell et al. (1975).
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III-7
Metabolism
Studies indicate that TCE Is metabolized to tri-
chloroethylene oxide (2,2,3-trichloro—oxirane), trichloro
acetaldehyde, trichloroacetic acid, monochloroacetic acid,
trichloroethanol, trichloroethanol glucuronide). These
metabolites have been obtained both in in vivo and in vitro
experiments, utilizing both experimental animals and human
systems. In general, the metabolites reported in the animal
systems were qualitatively similar to those found in humans.
A proposed pathway for the metabolism of trichloro-
ethylene is given in Figure 1. According to this pathway,
the first step in the biotransformation of TCE is the forma-
tion of 2,2,3-trichloro oxirane by the epoxidation of the
double bond. Uehleke and Poplawski-Tabarelli (1977) com-
pared the absorption spectrum at 451-452 nm of both the
incubated rabbit liver microsomes with trichloroethylene and
2,2,3-trichloro oxirane added to reduce suspension of rabbit
liver microsomes. Both preparations had identical spectra.
Trichloroethylene did not form a ligand absorption spectrum
with hepatic microsomes reduced by dithionite or in anaerobic
incubates in the presence of NADPH. 2,2,3-trichloro oxirane
has not been isolated and characterized in either in vitro or
in vivo experiments probably because of the unstable nature of
the compound.
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m-e
a.
1
O.-C- O
I
• OH J
"L ci
1
H- C- O
1
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III-9
The intramolecular rearrangement of trichloroethy-
lene oxide and hydrolysis may result in the formation of chloral
hydrate. Experiments conducted by Daniel (1963) suggest that
the rearrangement favors the pathway leading to the formation
of chloral hydrate and the subsequent metabolites—trichloro-
ethanol and trichloroacetic acid. The author showed that chlo-
rine attached to TCE is not removed during biotransformation
in rats exposed to 36Cl-labelled compound. Approximately 93%
of the 36Cl-labelled TCE administered by stomach tube was excreted
unchanged through the lungs or in the urine as trichloroethanol
and trichloroacetic acid. The specific activities of metabolic
trichloroacetic acid and trichloroethanol were shown to be the
same as that of the administered trichloroethylene, thus demon-
strating an intramolecular rearrangement of chloride.
Chloral hydrate has been suggested as an interme-
diate in the metabolic pathway of TCE since 1949. Later,
Liebman (1965), and Byington and Leibman (1965) demonstrated
the transformation of trichloroethylene to chloral hydrate.
These workers utilized liver microsomes of rats, rabbits and
dogs, in a reaction requiring NADPH and oxygen. Ikeda and
Imamura (1973) confirmed this finding, using rat liver micro-
somes. In vivo identification of chloral hydrate was done
by Kimmerle and Eban (1973), using rats exposed to TCE vapors.
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111-10
Chloral hydrate as a metabolite of TCE in the plasma of human
subjects following trichloroethylene anesthesia was demonstrated
by Cole, et al., 1975.
The next step in the metabolic process of TCE involves
biotransformation of chloral hydrate to trichloroethanol by a
reduction reaction and to trichloroacetic acid by oxidation pro-
cesses. Trichloroacetic acid was identified by Fujiwara test in
the urine of dogs exposed to TCE vapors (Barret and Johnston,
1939). The identity of trichloroacetic acid was confirmed by its
m.p. and mixed ra.p. with an authentic sample of trichloroacetic-
acid, (Powell, 1945). Quantitative relationship of formation
and the course of elimination in the urine of the metabolites
including trichloroacetic acid were determined by Soucek and
Vlachova (1959, 1960). Three men and two women with an average
age of 21 years were exposed to TCE vapors. Their urine was
analyzed for monochloroacetic acid, trichloroacetic acid and
trichloroethanol. Sex-related differences in the metabolism
of TCE were not noted.
Ogata and SaeXi (1974) reported the presence of
monochloroacetic acid and chloral hydrate in the blood serum
after oral administration of TCE to rabbits. However, because
of its short half-life chloral hydrate does not remain in the
body for a long length of time.
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III-ll
Elimination
TCE and its metabolites are excreted in urine, by
exhalation, and to a lesser degree in sweat, feces, and
saliva. Trichloroethanol, trichloroethanol glucuronide,
monochloroacetic acid, and trichloroacetic acid appear in the
urine immediately after exposure begins. Monochloroacetic
acid is excreted from the organism the fastest, followed by
trichloroethanol, trichloroethanol glucuronide and trichloroacetic
acid. On the other hand, TCE is excreted in the urine in
small amounts (Soucek and Vlachova, 1959).
Urinary elimination of TCE metabolites in experimental
animals has been investigated by several researchers (Friberg
et al., 1953; Forssmann and Holmquist, 1953; Kimmerle and
Eben, 1973; and Ogta and Saeki, 1974). Rats exposed to TCE
vapors excreted Fujiwara positive reaction products which
were calculated as trichloroacetic acid (Friberg et al., 1953;
Forssmann and Holmquist, 1953). Kimmerle and Eben (1973)
detected trichloroacetic acid and trichloroethanol glucuronide
in the urine of rats given trichloroethylene by inhalation.
Trichloroacetic acid was determined colorimetrically whereas
trichloroethanol glucuronide was analyzed by gas chromatogra-
phically after enzymatic hydrolysis of the urine samples. After
oral administration of trichloroethylene to rabbits, the follow-
ing metabolites, in order of decreasing concentration were detected
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111-12
After oral administration of trichloroethylene to rabbits, the
following metabolites, in order of decreasing concentration
were detected in the urine: chloral hydrate
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111-13
retained TCE. Trichloroacetic acid appeared in the urine
immediately after inhalation, and its concentration slowly
rose due to its ability to accumulate in the body. Maximal
excretion occured within 24-48 hours and lasted for 520 hours.
The fall in the rate of excretion was considered to be the sum
of two exponential rates (phases). The first phase lasted
about 5 days, and t.he second phase lasted approximately 14 days.
Trichloroacetic acid comprised 10% to 30% (19% average) of the
retained vapor. Trichloroethanol was also excreted witnin the
first few minutes of exposure. Excretion of trichloroethanol
reached its maximum a few hours after exposure and rose very
rapidly. The excretion time was 312-390 hours (average 350
hours). A decrease in the excretion rate appeared as the sum
of two exponential rates. The first phase lasted 3-4 days, while
the second phase lasted 7-9 days. The total quantity of trichlo-
roethanol excreted was between 32% and 59% of the TCE retained;
the average was 50%. The total quantity of these three metabo-
lites excreted in the urine of humans amounted to from 43% to
100% of the absorbed TCE. The ratio of these three metabolites
was found to be monochloroacetic acid: trichloroacetic acid: tri-
chloroethanol - 1:5:12.
Bartonicek (1962) and Ogata et al. (1971) confirmed
Soucek and Vlachova's findings. Eight volunteers (both males
and females) were exposed to 1,042 mg/m3 TCE for 5 hours by
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111-14
Bartonicek (1962). Of the retained TCE, 38.0% to 49.7% and
27.4% to 35.7% was excreted in urine as trichloroethanol and
trichloroacetic acid, respectively. The amount of trichloro-
ethylene eliminated via the lungs was not determined.
Bartonicek, in the same experiment, found that trichloroethanol
and trichloroacetic acid were excreted in the feces, for a
total of 8.4%. The time and the time intervals at which
expired air was analyzed for TCE were not provided. Therefore,
the amount amount of TCE absorbed cannot be determined accu-
rately; there is a possibility of reaching a steady state
between the blood concentration and the inhaled TCE concen-
tration.
Ogata, et al. (1971) conducted two separate experi-
ments on 13 male subjects exposed to approximately 474 mg/m3
and 927 mg/m3 TCE. One group of five people (A) remained
in the exposure chamber for 3 hours in the morning and 4
hours in the afternoon at an exposure of 927 mg/m3. A
second group of four people (B) were exposed to 474 mg/m3,
but they remained in the chamber for only 3 hours (in the
morning). Urine was collected for 100 hours after the initial
exposure. In Groups A and B, the concentration of trichloro-
ethanol was maximum 1-3 hours after exposure, and trichloro-
acetic acid concentrations were maximum 42-69 hours after
exposure. The excretion rate of trichloroacetic acid and
trichloroethanol returned to normal after 92 hours. The
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111-15
total amounts of trichloroethanol and trichloracetic acid
recovered in the urine were 44% and 18.1%, respectively, for
the 7-hour exposure. Fifty-three percent of the trichloroethanol
and 21.9% of the trichloroacetic acid was the final amount
recovered in the 3-hour exposure to 927 mg/m3.
The levels of TCE metabolites in the urine of humans
have been recorded by many researchers. Ikeda and Ohtsuji
(1972) conducted two separate experiments on male workers
exposed to TCE vapors (1090 mg/m3) for 8 hours, and recorded
the excretion of the metabolites in the urine. In the first
experiment six workers were exposed intermittently to 54.5 to
272.5 mg/m3 of the solvent. Total trichloro-compounds varied
from 38 to 376 mg/liter, trichloroethanol varied from 11 to
281 mg/liter, and trichloroacetic acid varied from 18-95
rag/liter in the urine. In the second experiment, 14 workers
were exposed intermittently to a range of 650 to 1363 mg/m3
TCE. The urinary metabolites ranged from 55-487 for total
trichloro-compounds, 33-347 for trichloroethanol, and 22-177
for trichloroacetic acid. The overall time during which
these urinary metabolites were measured was not given.
Surveys were conducted by Ikeda et al. (1972) on 85
male industrial workers (36 control) under working environments.
The urinary excretion of metabolites was recorded as total
trichloro-compounds. The results are summarized in Table II1-2
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111-16
and show that metabolite concentration increased as exposure
concentration increased.
Sukhanova and Burdygina (1971) measured the metabolite
level in the urine of students during their 4 months' appren-
ticeship in a plant which used TCE. The content of metabolites
in the urine increased significantly. After 4 months, the
metabolites found in the urine of students ranged from 2.3 to
65.6 mg/liter.
Five male volunteers were subjected to 1090 mg/m3 TCE
7 hours/day for 5 days (Stewart, 1968). Twenty-four hour urine
samples were collected and analyzed for trichloroacetic acid
and trichloroethanol before, after, and during exposure. The
results are summarized in Table III-3.
A study conducted by Friberg, et al. (1953) showed simi-
lar results. Three people were exposed to TCE concentrations
ranging from 100-150 ppm for 7 hours daily for 1 week. During
the later days of the study, 250-500 mg of trichloroacetic acid
per liter of urine was excreted. Frant and Westendorf (1950)
calculated that if people were exposed to 100 ppm of TCE for
several days, they would excrete about 200 mg/liter of trichloro-
acetic acid in the urine. Grandjean, et al. (1955) reported that
workers, most of them exposed to 20-40 ppm TCE, excreted about 8%
of inhaled TCE as trichloroacetic acid in a ratio of 3:1 (3
mg/liter trichloroacetic acid in the urine to 1 ppm TCE in the
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Table III-2
Average Metabolite Concentrations in Urine of Workers
Exposed to Various Concentrations of Trichloroethylene (mg/1)
Metabolite Concentrations
Number of
People Exposed
Concentration
(ppm) ?/
Time Exposed
Total Trichloro- Trichloro- Trichloro-
Corpounds ethanol acetic Acid
36
9
5
6
4
4
5
5
5
4
4
0
3
5
10
25
40
45
50
60
120
175
8
8
8
8
8
8
8
8
8
8
8
hr/day,
hr/day.
hr/day,
hr/day,
hr/day,
hr/day.
hr/day,
hr/day,
hr/day,
hr/day,
hr/day,
6
6
6
6
6
6
6
6
6
6
6
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
days/wk
1
39
45
60
164
324
399
418
468
915
1,210
.4
.6
.5
.3
.9
.0
.9
.0
,3
.9
0
25
24
42
77
220
256
267
307
681
973
.1
.9
.0
.3
.3
.7
,3
.9
.8
.1
1
12
20
17
77
90
138
146
155
230
235
.7
.2
.6
.2
.6
.4
.6
.4
.1
.8
jj/ The parts per million of solvent in the air was measured using Kitagawa (1961) detection
tubes. At least five determinations were made and the averages were recorded.
Sourcei Ikeda et al. (1972).
-------
111-18
Table III-3
Urinary Excretion of Trichloroacetic Acid and Trichloroethanol in Five Subjects
During and Following Trichloroethylene Exposure f|/
Time
Metabolite Concentration (mg/1)
Trichloracetic Acid
Trichloroethanol
1st Exposure day
2nd Exposure day
3rd Exposure day
4th Exposure day
5th Day 'following last exposure
12th Day following last exposure
51 (34 - 84)
175 (113-238)
229 (148-416)
306 (249-439)
50 (35 - 61)
8 (2 - 22)
308 (179-480)
359 (294-480)
399 (296-546)
538 (294-822)
15 (10 - 18)
14 (1 - 37)
*/ Subjects were exposed to 200 ppjn trichloroethylene, 7 hr/day for 5 days.
Source: Stewart (1968).
-------
111-19
urine to 1 ppm TCE in the air). This ratio was larger in younger
people (6:1) than in older people (2:1).
Results from two experiments described below indicate
there may be a variation in the urinary excretion of TCE
metabolites depending on the sex of the subject. More specifi-
cally, there may be a sex difference in human metabolism of
TCE. However, there is not enough evidence to substantiate
this theory.
Nomiyama (1971) exposed five male and five female
students to between 250 and 380 ppm TCE for 160 minutes. Males
and females excrete trichloroacetic acid and trichloroethanol
in different amounts during the first 24 hours after exposure.
Females excreted more trichloroacetic acid in their urine
than did males, while males excreted twice as much trichloroethanol
as females. Of the retained TCE in males, 32.6% was excreted
as trichloroacetic acid and 48.6% as trichloroethanol, whereas
in females, 49.3% of retained TCE was excreted as trichloroacetic
acid and 42.7% as trichloroethanol.
Similar results were obtained by Kimmerle and Eben
(1973b). After exposing eight volunteers (four male and four
female) to either 44+4 ppm or 50+7 ppm of TCE for 4 hours,
-27-
-------
111-20
a difference in the amount of excretion products was noted.
Females showed a higher excretion of trichloroacetic acid
than males. No other differences between sexes in urinary
excretion levels or concentrations of TCE and trichloroethanol
in the blood were observed.
Four male volunteers inhaled 70 and 140 ppm TCE for
4 hours during exercise and at-.rest. Monster et al. (1976)
reported that exercise increased the quantity inhaled but not
the distribution of metabolism. Analysis accounted for 67%
of the dose: 10% unchanged from lungs and 39% trichloroethanol
plus 18% trichloroacetic acid in the urine.
Storage-Biological Half-life
Many articles have been published on the biological
half-life (Tj/2) of TCE and its metabolites in humans. ITceda
and Imamura (1973) collected and summarized these previous
citations of biological half-lives; an expanded version of
these citations is presented in Table III-4. Additional
studies on the half-lives in the urine, not cited by Ikeda
and Imamura, have been collected and added.
Ikeda and Imamura noted a wide variance in biological
half-lives (26-51 hours) of total trichloro-compounds in urine
of factory workers exposed to TCE (Table III-4). There
appears to be no correlation between the number of exposures
-28-
-------
111-21
and variance in biological half-lives. However, IXeda and
Imamura observed that the total mean value calculated was
about 41 hours. This value closely correlates to the
experimental values of half-lives in subjects not previously
exposed to TCE vapors.
Two other observations based on data from Table III-
4 were made by Ike da and Imamura. First, no sex related differ-
ences were observed in the half-life of total trichlorocompounds;
second, the half-life in an "addicted" patient was higher than
in the factory workers.
Few data have been published on the biological half-
lives of TCE in the blood. Table III-5 summarizes the biological
half-lives of metabolites of TCE in the blood of human subjects
exposed occupationally to vapors of trichloroethylene.
The biological half-life in the serum and urine of
rabbits was reported by Ogata and Saeki (1974) (Table III-6).
Results show that, except for TCE and chloral hydrate, the
half-lives of metabolites in urine are longer than in serum.
Four subjects were repeatedly exposed to TCE, 4
hours/day for 5 days, at 50 ppm (48+3 ppm) (Kimmerle and
Eben, 1973). It was noted that trichloroethanol could be
detected in the human blood up to 4 days following a single
exposure to 50 ppm.
-29-
-------
111-22
Table II1-4
Biological Half-Life of Metabolites in the Urine of Human Subjects
Exposed to Vapors of Trichloroethylene
Biological Half-Life (hr.)
Number Total
Group
Affected
Factory
workers
of Exposure Load
People Sex and Time
6 M 10 to 150 ppm
for 4 hr, 1
or 2 times/no
Trichloro-
Ccmpounds Trichloroethanol
42.7
(37.3
+ 4.5V -
+ 6.2) —
Trichloroacetic
Acid References
— Ikeda and Imamura
— (1973)
Volunteers
M 5 to 170 ppm 48.8 + 11.7
for 2 hr, 1 or (47.5 + 7.7)
2 times/no
M Intermittently 26.1 + 4.8
exposed to (22.7 + 4.6)
200 ppm 5
days/week
M 20 to 40 ppm
for 8 hr/day
for 5 days/wk
33.7 + 6.8
(26.9 + 5.0)
P Intermittently 50.7 + 7.7
exposed to (38.3 + 7.5)
50 ppm 5 days/
week
186 ppm for
5 hr
50.3
M 250 to 380 ppm 31.4
for 160 min
F 250 to 380 ppn 36.1
15.1 + 2.2
(14.2 -f 2.3)
39.7 + 8.7
(36.5 + 17.3)
42.7 + 9.1 57.6 + 19.8
(12.6 + 8.9) (50.9 + 22.6)
29.2
19.0
25.8
55.3
38.0
36.1
Ikeda and Imamura
(1973)
Ikeda and Imamura
(1973)
Ikeda and Imamura
(1973)
Ikeda and Imamura
(1973)
Bartonicek
(1962)^
Nomiyama and
Nomiyana (1971)
Nomiyama and
Nomiyama (1971)
-------
111-23
Table III-4 (Continued)
Biological Half-Life (hr.)
Number Total
Group of Exposure Load Trichloro- Trichloroacetic
Affected People Sex and Time Compounds Trichloroethanol Acid References
Volunteers 5
4
M 170 ppm for
7 hr
35.8
M 170 ppm for 48.6
3 hr
Ogata et al.
~
Ogata et al.
(197IJ5T
Addict
5 M,F 50 ppm for —
6hr
1 M — 72.6
(95.1)
12.0
49.7
(49.8)
100.0
72.6
(95.0)
Muller et al.
Ikeda et al.
(197D5T
a/ Values are mean + SE calculated from metabolite concentration corrected for a specific gravity of urine
of 1.016 together with those corrected for creatinine concentration in parenthesis.
b/ Values are calculated by the present authors from results of referred authors.
-------
111-24
Table II1-5
Biological Half-Life of Metabolites in the Blood of Hunan Subjects Exposed
Occupationally or Experimentally to Vapors of Trichlorethylene
Compound
Groups
Type of
Exposure
Biological
Half-Life
-------
Biological Half-Life of TCE
and Metabolites in Rabbits3/
Compound
Trichloroethylene
Chloral hydrate
Free trichloroethanol
Total trichloroethanol
Conjugate trichloroethanol
Monochloroacetic acid
Trichloroacetic acid
Half-life
Urine
30.5
38.0
42.0
36.0
43.5
(hr.)
Serum
3.8
6.4
8.4
8.5
8.5
14.0
18.5
n •
a/ Rabbits were given 13 moles/kg TCE orally.
Source: Ogata and Saeki (1974).
Summary and Conclusion
Information on the quantitative absorption of TCE via ingestion
is not available. However, TCE is expected to be completely absorbed
after ingestion, because of the physico-chemical nature of the chemical.
The extent of absorption by the inhalation route has been reported to
be between 51 and 64 percent. This appears misleading because it is
reasonable to believe that at a given concentration of TCE in air,
equilibrium between the concentration in air and concentration in
blood 'is established. After the equilibrium is established, the
absorption is dependent upon the disposition and metabolism of the
chemical. TCE has been reported to distribute in tissues according to
their fat contents. It crosses the placental barrier and has been
detected in fetal blood.
-33-
-------
Ill-26
TCE is biotransfonned in the mamillian system probably
via the formation of an epoxide. The metabolites identified in-
clude trichloroacetaldehyde, trichloroacetic acid, monochloro-
acetic acid, trichloroethanol and trichloroethanol glucuronide.
In general, the metabolites reported in the animal systems are
qualitatively similar to those found in humans.
TCE and its metabolites are eliminated in urine, by
exhalation and to a lesser degree in sweat, feces, and saliva.
Urinary excretion of the metabolites—trichloroethanol and
trichloroacetic acid appears to be dose dependant—higher the
dose, larger the amount of these metabolites excreted in the
urine. The metabolite, trichloroacetic acid has been reported
to bind with plasma protein. On repeated exposure, this meta-
bolite may stay in the body for a long time.
-34-
-------
V. ACUTE AND CHRONIC HEALTH EFFECTS IN ANIMALS
A. Hepatotoxicity
Several inhalation studies, after single or
multiple exposures, have provided observations on hepato-toxic
effects. Kylin ejt al. (1962) compared the hepatotoxicity of
chloroform, trichloroethylene and tetrachloroethylene. Mice
were given a single 4-hour exposure by inhalation. The animals
were sacrificed on the third day; the livers were analyzed
for fat by histological examination and by acetone-hexane ex-
traction. In addition, activity of serum ornithine carbamyl
transferase was determined. Trichloroethylene, at a concentra-
tion level of 6,400 ppm produced no significant damage to the
liver. In this study, trichloroethylene was the least hepato-
toxic/ whereas chloroform was the most. Similar results were
obtained by Plaa et a1. (1958) and Gehring (1968) when animals
were exposed to halogenated hydrocarbon solvents by subcutaneous
injection and by inhalation. The results of these workers
indicate that the halogenated hydrocarbon solvents rank in the
order of their decreasing capacity to cause liver dysfunction:
carbon tetrachloride, chloroform, 1,1,2-trichloroethane,
tetrachloroethylene, trichloroethylene, and 1,1,1-trichloro-
ethane.
Multiple inhalation exposure studies have been reported
utilizing mice, rats and dogs. Seifter (1944) observed degener-
ation of liver parenchyma cells in dogs that were exposed either
-35-
-------
V-2
to 750 ppm TCE 8 hours /day, 6 days/week for 3 weeks or 500 to
750 ppm TCE 6 hours/day, 5 days/week for 8 weeks. Slight fatty
infiltration of the liver of mice was detected by Kylin et al.
(1965). The female albino mice were exposed to 1,600 ppm TCE
by inhalation for 4 hours daily, six days a week, over periods
of one, two, four and eight weeks. The increase in liver fat
content was detectable after one week's exposure and subsequent-
ly the liver fat showed no further increase. In terms of fatty
degeneration, the authors noticed that tetrachlorethylene was
approximately 1/10 times less toxic than trichloroethylene.
Male Wistar II rats inhaling 55 ppm TCE for 14 weeks, exhibited
elevated liver weights but did not cause pathological changes
measured by hematological examinations, liver function tests,
renal function tests and blood glucose (Kimmerle and Eben,
1973). Four animal species—rabbits, guinea pigs, rats and
monkeys—were exposed to 100-3,000 ppm TCE vapors seven hours
daily, 5 days a week, for periods up to approximately six months
by Adams et al. (1951). Rats exposed to 300-3,000 ppm TCE for a
period of 36 days (total of 27 exposures) showed an increase
in liver and kidney weights. However, histopathological exami-
nation of the tissues failed to reveal any abnormality in male
rats, but some female rats showed fat vacuoles in the cytoplasm
of the liver. Rats exposed to 200 ppm TCE for 205 days (total
exposures 151) showed no significant abnormality from the
controls. The authors concluded that the maximum concentrations
-36-
-------
without adverse effects were as follows: monkey, 400 ppm;
rat and rabbit, 200 ppm? guinea pig, 100 ppm.
B. Nephrotoxicity
There are conflicting reports in the literature
regarding renal damage resulting from parenteral and inhalation
exposure of animals to TCE. Kidney damage was observed in rats
(maintained on a high protein di«t) exposed to 5 mg/liter
(935 ppm) TCE, 5 hours/day for 7 days (Kalashnikova et al.,
1974). Investigators observed focal dystrophic changes in
the renal tubule epithelium. A long-terra inhalation study on
rats, guinea pigs, dogs, rabbits, and monkeys by Pendergast
et al. (1967) showed that no nephrotoxicity occurred at
continuous concentrations of 35 ppm (189 mg/m3) for 90 days
and 730 ppm (3825 mg/m3) for 8 hours/day, 5 days/week for 6
weeks.
Plaa and Larson (1965) found that after injecting
mice intraperitoneally with 0.6 ml/kg of TCE, no renal
toxicity was observed. The acute nephrotoxic properties were
studied using phenol sulphthalein excretion, the presence of
proteinuria and glucosuria, and histopathology. However, when
Bartonicek and Soucek (1959) injected six rabbits (av. wt. 4.2
kg) intramuscularly with 33-55 g of TCE over a period of 55-
100 days, two of the rabbits died from renal failure.
-37-
-------
V-4
C. Nervous System
Because of its effects on the nervous system,
TCE has been used as a general anesthetic agent. Studies
performed as early as 1944 give information concerning the
blood concentration of TCE for lethal as well as anesthetic
effects. Dogs, rabbits, guinea pigs and cats were administered
TCE by inhalation. Blood levels were determined at death and at
anesthesia stages. Lethal blood TCE concentration in dogs were
found to be 100-110 mg/100 ml blood. At the anesthetic stage,
TCE blood levels were 24-37, 23-28, 14-18, 25-32 mg/100 ml
blood for dogs, rabbits, guinea pigs and cats, respectively.
The blood-brain ratio at anesthetic dosages was approximately
1:2 for both guinea pigs and dogs (Kulkarni, 1944).
Histopathological changes have been observed on acute
and long-term exposure of animals to TCE. A single exposure
of dogs to 30,000 ppm TCE in air resulted in death within 20
minutes. No obvious changes were found in the nervous system.
In a longer terra experiment, the animals were subjected to TCE
concentration ranging from 500-3,000 ppm for periods varying
2-8 hours daily, often for 5 days weekly. The total exposure
period was between 60-162 hours. The exposures appear to
selectively destroy the Purkinje layer of the cerebellum. The
cerebral hemispheres showed mild changes—scattered cortical
neurons became swollen or pyknotic and the white matter of
-38-
-------
V-5
the myelin developed a mild focal swelling (Baker, 1958).
Bartonicek and Brun (1970) injected TCE intramuscularly in
female rabbits and observed moderate neurological changes in
the exposed animals. The dosage regimen included subacute
exposure for 29 days. Animals were injected with 2.47 g/kg
body weight three times a week. For the chronic exposure experi-
ment, animals were injected intramuscularly for 41-247 days
with 1.62 g/kg twice a week. The rabbits were sacrificed at
different times during the test and the brains examined
histologically and histochemically for any pathological
change. Round cell infiltration around blood vessels and in
the parenchyma occured in all animals of the subacute and in
one of the chronic experiments but not in the controls.
Disappearance of Purkinje cells and basket cells was defi-
nitely shown only in the chronic experiment.
Grandjean (1960) exposed male rats to 200 and 800
ppro TCE vapors for 4-11 weeks. The rats were subjected to a
single 3-hour TCE exposure just before testing. After the
exposure, trained rats responding to signals climbed up a
rope to reach a feeding trough where they found a small
dextrose pellet as a reward. The results indicate that the
increase in the number of spontaneous climbs after exposure
to the solvent is significant in comparison with the control
-39-
-------
V-6
tests. The observed effect was not dose-dependent. The
authors conclude: TCE in doses stud-led modified the psycho-
logical equilibrium of rats by increasing excitability. The
author in the 1963 report described the effect of TCE vapors
on the swimming performance and on the motor activity of rats.
The animals were exposed for six hours and swimming tests were
performed 5-15 minutes later. At 400 ppm, TCE retarded only
the rats swimming with an additional load in a manner barely
significant while 800 ppm adversely affected the performance
both with the load and without, in a significant manner. One
hour after termination of exposure/ no significant changes in
the swimming times could be observed.
D. Cardiovascular Effects
TCE causes depression in myocardial contractility
(Aviado e£ al., 1976). The minimum inhaled concentration of
500 ppm caused a depression in the myocardial contractility in
dogs. Transitory arrythmia was observed in the isolated guinea
pig heart at a concentration of 5,300 ppm.
E. Teratogenic Effects
Trichloroethylene does not appear to be tetrato-
genic in animals. Pregnant rats and mice were exposed to 300 ppm
TCE vapor for 7 hours daily on days 6-15 of gestation. This
exposure resulted in a slight but statistically significant reduc-
tion in mean body weights of maternal rats, but not mice during
-40-
-------
V-7
and/or following exposure. No teratogenic abnormalities were
observed in either of the species.
In another study, Dorfmueller, e_t al. (1979) exposed,
by inhalation, female Long-Evans hooded rats to trichloroethylene
at a concentration of 1800 +_ 200 ppm (9810 +_ 1090 mg/m3) for two
weeks before mating and during the first twenty days of pregnancy.
Rats were observed for changes in the body weight every 4 days.
Fetuses were weighed and examined for skeletal and soft tissue
anomalies. Postnatal behavioral changes were examined by
activity measurements with aid of electronic Motility Meters.
The most frequent, skeletal anomaly observed was incomplete ossi-
fication of sternum, indicative of delayed skeletal ossification
rather than a true malformation. No overt maternal toxicity,
embryotoxicity or teratogenicity were seen as a result of TCE
treatment.
F. Mutagenic Effects
There have been a number of recent studies using
various assay techniques to determine the mutagenic potential of
TCE. Current results are tabulated (Table V-l) with both positive
and negative results depending on the test system and whether or
not the system was metabolically activated.
-41-
-------
V-8
Table V-l
Mutagenicity Testing — Trichloroethylene
Test System
Reaction Tested
Result
Reference
Microbial:
sairnonella typhimnrium
gaincnella typhimarium
salmonella typhimuriuni
Escherichia coli
K-12
Sacchromyces cerevisiae
Sacchromyces cerevisiae
SV185-14C
Animal:
Fischer Rat entoryo
Gene nutation
Gene nutation
Gene nutation
Gene nutation
Mitotic gene
conversion
Gene nutation
Frameshift
nutation
Mutagenic in
activated system
Mutagenic in
activated system
Nbn-Mutagenic
Mutagenic in
activated system
Positive
Positive
Greim et al.
(19757 ~~
Bartsch et al.
J(1975)
Waskell
(1978)
Griem et al.
(1977T
Bronzetti et
al. (1978l~
Shahin and
VonBorstel
Cellular Trans'
nation
i- Positive
Price et al.
(1978T
-42-
-------
V-9
Bacterial mutagenesis system is most commonly used as
a screening technique to determine the mutagenic and carcino-
genic potential of chemicals. Trichloroethylene was found
mutagenic in salmonella typhimurium strains and the E. coli
K 12 strain, utilizing liver microsomes for activation (Greim
et al., 1975; 1977). Bartsch et al. (1979) used S-9 fractions
from liver specimens for activation instead of microsomes for
mutagenesis test. The authors reported trichloroethylene as
marginally mutagenic. Waskell (1978) reported trichloroethylene
nonmutagenic in Ames test system with activation. The negative
response obtained by later researchers cannot be explained at
the present time.
Sacchromyces cerevisiae (yeast), and Fischer rat
embryo, have also been used to study mutagenic response. After
activation with liver microsomal fractions trichloroethylene was
mutagenic in strains of yeast in such as sacchromyces cerevisiae
strains D4,.D7 and XV185-14C (Bronzetti et al. 1978, Shahin and
von Borstel 1977). Price et al. (1978) tested TCE for in vitro
cell transforming potential in a Fischer rat embryo system
(F1706). The transformed cells grew in a semisolid agar and
produced undifferentiated fibrosarcomas when inoculated into
newborn Fischer rats.
-43-
-------
V-10
G. Carcinogenic Effects
The National Cancer Institute (NCI, 1976) con-
ducted a study to delineate the carcinogenic potential of
trichloroethylene. They used both sexes of Osborne-Mendel
rats and 8^3?^ mice. For rats, the initial doses were 1,300
and 650 rag/kg body weight. The dosages were changed, based
upon survival and body weight data, so that "time-weighted"
average doses were 549 and 1,097 rag/kg for both male and female
animals. The time-weighted average daily doses were 1,169 and
2,339 mg/kg for male mice and 869 and 1739 rag/kg for female
mice. Animals were exposed to the compound by oral gavage 5
times per week for 78 weeks. They were observed until the termi-
nal sacrifice at 110 weeks for rats and 90 weeks for mice. A
complete necropsy and microscopic evaluation were conducted
on all the animals (except 7 out of the original 480, who died
at unscheduled times).
No significant difference was noted in neoplasms
between experimental and control groups of rats. However,
in both male and female mice, the higher dose-induced primary
malignant tumors in the liver. For males, 26 of 50 mice who
received the low dosage and 31 of the 48 mice who received
the high dosage developed hepatocellular carcinomas while only
1 out of 20 of the controls showed neoplasms. In female mice,
4 of the 50 receiving the low dosage and 11 out of 47 receiving
-44-
-------
V-ll
the high dosage developed neoplasms as compared to zero out of
20 of the controls.
The results of this experiment indicate that trichloro-
ethylene induced a hepatocellular carcinoma response in mice.
Under the conditions of this experiment, the rats did not
elicit the carcinogenic response.
In the NCI study citeM above, the test chemical,
trichloroethylene was later found to contain epichlorohydrin-
a carcinogen. Therefore, NCI repeated the bioassay with epi-
chlorohydrin-free trichloroethylene. Rats (F344/N) and mice
(BgCsFi) of both sexes were used. Trichloroethylene was mixed
with corn oil and administered by gavage five times per week
for 103 weeks. Rats received dosages of 500 and 1,000 mg/kg.
These dose levels were lower than the initial doses used in the
earlier bioassay in Osborne-Mendel rats (650 and 1,300 mg/kg
for both sexes). As with the rats, the dosage levels used in
the mice were lower than in the earlier study. The dose
selected for the study in mice was 1,000 mg/kg for both sexes.
Trichloroethylene was not found to be carcinogenic
for female F344/N rats. The experiment with male rats was
considered inadequate because these rats received dose levels
of trichloroethylene which exceeded the maximum tolerated dose.
-45-
-------
V-12
Trichloroethylene was carcinogenic f,or both sexes of 8503?!
mice, producing hepatocellular carcinomas.
In another study by Rudali (1967), oral doses of TCE
were administered by gavage to 28 NLC mice (age not specified).
Dosages of 0.1 ml of a 40% solution of TCE in oil were admin-
istered twice weekly for an unspecified time. No liver lesions
or hepatomas were observed. In a similar set of experiments,
chloroform was slightly oncogenic.
H. Synergistic and/or Antagonistic Responses
There are a few reports which suggest interaction
of TCE and the drugs/chemicals, when given concurrently and/or
in sequence. The interactions have been reported at very high
dose levels for short durations. Interaction studies for longer
durations are not available. Therefore, information cited below
should not be used for making any adjustment to the standard.
Cornish and Adefuin (1966) found that the hepatoxic
response was markedly potentiated by prior ingestion of ethanol.
These workers exposed rats to TCE (10,000 ppm) for 1.5 hours.
Pretreatment of rats with phenobarbital (50 mg/kg, 2.p.) or 3
methylcholanthrene (40 mg/kg) increased TCE-induced liver
damage as indicated by SCOT and SGPT (Carlson, 1974). The
possible mechanism behind these observations have been described
in the Section "mechanisms of toxicity."
-46-
-------
V-13
Summary and Conclusions
1. Trichloroethylene has been reported to adversely affect
the livers of the exposed animals.. In acute exposures, it is
ranked in the following order of decreasing capacity to cause
liver dysfunction: Carbon tetrachloride, chloroform, 1,1,2-tri-
chloroethane, trichloroethylene and 1,1,1-trichloroethane.
2. Animal species whioh have been reported to respond to
the toxic effects on liver are mice, rats, rabbits, guinea pigs,
dogs, and monkeys; however, which of the species is the most
sensitive, has not been precisely determined.
3. Chronic exposure of animals to trichloroethylene in-
duces nephrotoxic response.
4. At very high dose levels, TCE produces anesthesia. At
the anesthetic stage, TCE blood levels have been reported as
24-37, 23-28, 14-18, and 25-32 mg/ml blood for dogs, rabbits,
guinea pigs and cats respectively.
5. TCE was not found to be teratogenic.
6. TCE is considered a weak mutagen as indicated by micro-
bial test system.
7. In a repeat study with epichlorohydrin free trichloroethy-
lene, NCI found it carcinogenic in both sexes of B^FX mice. The
-47-
-------
V-14
experiment with male rats was considered inadequate for estab-
lishing carcinogenicity.
8. Interaction of TCE with ethanol ingestion has been
reported. This information cannot be used in deriving a standard
for TCE in drinking water, because the duration of exposure was
too short. In addition, it is reasonable to believe that the
interaction was dose-dependent and at lower concentration, the
interaction may not exist.
-48-
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VI. HUMAN HEALTH EFFECTS
A. Acute Exposure
The following section includes information con-
cerning the acute effects of trichloroethylene either by in-
gestion or by inhalation exposure. Special attention has been
given to the dosages in rag/kg body weight which have been
reported to produce an effect.
Single oral dosages ranging from 7.6 to 35 g have
been reported to exhibit clinical symptoms in humans. A 4-
1/2-year old child who ingested an estimated 7.6 g of trichlo-
roethylene, vomited, became inebriated, and lost consciousness
within a few minutes, but recovered after 4 hours (Gibitz and
Plochl, 1973). Two persons, who each consumed 15-25 ml (21-35g)
of trichloroethylene experienced vomiting and abdominal pain,
followed by inebriation and transient unconsciousness (Stephens,
1945).
Morreale (1975) reported one 56-year old patient who
drank 15 ml TCE and, along with neural intoxication, suffered
a myocardial infarct, which was attributed to the TCE.
Bernstein (1954) stated that a 19-year old marine who
underwent TCE anesthesia suffered cardiac arrest (due to an
excessive concentration of TCE in the body), but subsequently
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VI-2
recovered. In another report, electrocardiographic abnormali-
ties were seen in 15 of 30 patients exposed acutely to high
levels of TCE. Arrhythmia was the most frequent effect (Pelka
and Markiewicz, 1977).
Tomasini (1976) reviewed Italian case histories of
TCE-related toxicity. In about one-fourth of a group of 35
patients, cardiac arrhythmia of. some degree had occurred after
TCE exposure. Accidental, intentional, and industrial exposures
were included in the population. TCE levels that produqed the
fatalities ranged from oral introduction of 50cc pure TCE in a
21-year old male to a "pitcher" of Trilene in a 38-year old
female. Cardiac histories of the industrial workers were not
described, nor were quantities of TCE producing cardiac effects
reported. The author suggested that the mechanism of cardio-
toxicity was depression of normal rhythm which permitted any
other ectopic foci present to break the normal myocardial rhythm.
The fact was stated that TCE, as sold, is sometimes a mixture of
several chlorinated solvents. The relationship, if any, of
specific Italian additives to the cardiac effects described was
not further developed.
Dependent upon the dosages, the inhalation of TCE
results in a mild to severe central nervous system depression.
Salvini et al. (1971) observed psychophysiological changes in
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VI-3
human volunteers in a controlled inhalation study using TCE at
as low a level as 110 ppm for two fo'ur-hour periods. At 200
ppm TCE, Stopps and McLaughlin (1967") noted a slight decline
in performance of subjects, which became increasingly pronounced
at 300 and 500 ppm exposure levels.
Industrial accidents provide some information about
the toxic effects of trichloroethylene, however, these reports
do not provide precise dosages.. Buxton and Haywood (1967)
described four cases of industrial accidents that involved TCE.
Pour workers were required to climb inside tanks containing TCE
and scoop the remaining liquid out with buckets. All four workers
became ill, and one subsequently died. The symptoms of trichloro-
ethylene intoxication noted in two men who spent less than 30
minutes inside the tanks were nausea and headaches. The symptoms
observed in the third man who remained inside the tanks for 2-1/2
hours were nausea, diplopia, and facial displegia. The fourth
man, exposed to TCE vapors for the longest time period, died
after developing severe multiple cranial nerve palsies 51 days
after initial exposure. The authors ascribed the effects to
unidentified decomposition products of TCE.
Six women employed in the cleaning of optical lenses
for binoculars used their fingers to apply TCE for removal of
small spots of wax remaining on the lenses. After a few months,
they reported difficulty handling the lenses because they could
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VI-4
no longer feel the lenses properly. Examination showed persistent
loss of tactile sense, inability to grasp objects between thumb
and fingers, and loss of motion. Disability lasted for several
months (McBirney, 1954). No skin damage was noted in any of these
cases.
Maioof (1949) reports a worker who, after entering a
freshly drained, heated degreasing tank, became comatose, suffered
convulsions and had to be treated for first, second, and third
degree chemical burns. Upon awakening, the worker complained of
blurred and double vision and burning sensation of the skin. He
recovered 31 days later. Another worker involved in the incident
became unconscious, but regained consciousness almost immediately.
A man employed for one month as a metal degreaser lost
his sense of taste and after two months of employment, developed
trigeminal analgesia. Non-recovery of taste and trigeminal sensa-
tion was reported ten months later (Mitchell and Parsons-Smith,
1969).
Trichloroethylene has been shown to cause hepatic
necrosis in man following either inhalation or ingestion
(Ossenberg et al., 1972; Chiesura and Corsi, 1961). However,
liver damage does not always occur in TCE intoxication. Most
occupational studies on man show an increase in serum transaminases,
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VI-5
which indicates damage to the liver parenchyma (Albahary et
al., 1959; Lachnit, 1971). These increases are transient and
usually disappear after exposure is terminated.
B. Chronic Exposure
Toxic hepatitis was observed in a patient who had
been cleaning a tank in which trichloroethylene was used to
clean machine parts. Evidence of liver damage was based on
rising serum glutamic-oxalacetic transaminase (SCOT), serum
glutamicpyruvic transaminase (SGPT), and lactic dehydrogenase
(LDH) levels (Bauer and Rabens, 1974). These levels returned
to normal 6 weeks later. It was not stated how long this person
had been employed or whether he had cleaned more than one tank
as part of his regular duties.
Milby (1968) reported a case of TCE intoxication of a
39-year old female employed for two years as a paint-stripping
operator. Six months prior to medical attention she had been
assigned to a newer model stripping machine. She showed no
signs of liver injury even though she complained of daily nausea
and vomiting, drunkenness, abdominal cramps, flushing, sleepiness,
loss of appetite and swelling of the eyes, face, and hands.
Her physician observed a nonspecifically abnormal electrocardiogram
and excretion of 780 mg trichloroacetic acid per liter in her
urine on the day of examination. One week later, she excreted
40 mg trichloroacetic acid per liter of urine.
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VI-6
Eight workers were exposed to TCE in an electroplating
plant for 2-3 weeks. The concentrations in the workroom ranged
from 115-384 ppm (627-2,093 mg/m3). Symptoms began almost
immediately after exposure and included headaches/ muscle and
joint pains, nausea, vomiting, loss of appetite, depression,
dizziness, and narcosis. All eight subjects showed an increase
in globulin fraction and a decreased albumin fraction. It was
concluded that liver damage was present as indicated by the
cephalin cholesterol flocculation test (CCF) and hyperglobulinemia
observations (Nomura, 1962).
Guyotjennin and van Steenkiste (1958)* reported that
18 workers exposed regularly to TCE showed signs of abnormal
lipid metabolism characterized by total lipid content determination,
analysis of lipid fractions and unsaturated fatty acid content.
There was also an increase in v~9lobulins.
Joron et al. (1955) found massive liver necrosis in a
patient exposed to TCE vapors previously and in an acute episode
lasting 2-1/2 hours where no protective mask was used. The patient
died more than 1 month after the last known exposure to the TCE.
Cotter (1950) examined 10 workers who were exposed
for several days to TCE vapors arising from a spill on board a
ship. Symptoms included dizziness, nausea and vomiting, mental
agitation, and coma, and later persistent abdominal pain.
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VI-7
cramps, diahrrea, and pain in the lower back. None were
clinically jaundiced and none of the 10 sera gave positive
reactions in cephalin cholesterol flocculation test. Cotter
suggested that liver damage was present because of changing
globulin level despite the absence of bilirubin or phosphatase
retention or a disturbance of the esterification of serum
chlolesterol. A full recovery of the subjects within 2 months
was noted.
It was noted that children are highly susceptible to
TCE liver pathology when compared to adult susceptibility (Kusch
et al., 1976}*.
Toxic effects of TCE on the urinary system in man are
not well defined. Only a few incidences of renal damage due to
TCE intoxication have been reported. Acute hepatic and renal
damage was reported in three patients with histories of drug
abuse. In one patient centrilobular hepatic necrosis was found
(Baerg and Kimberg, 1970). These effects were attributed to
sniffing Carbona cleaning fluid or Carbona No. 10 special spot
remover, which may contain TCE, petroleum solvents, and 1,1,1-
trichlorethane.
Gutch et al. (1965) reported that a needle biopsy
test showed acute tubular degenerative changes in the kidney of
•Foreign language article. The information was obtained from
a secondary source.
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VI-B
a 41-year old man who had inhaled TCE vapors. The man had been
replacing asphalt floor tile in a small, enclosed room (10 by 20
feet) with a small ventilation opening in one window. TCE (99.5%
pure) was used as a solvent to clean tile cement* A gallon
container of TCE remained open during the cleaning operations
which lasted over 2 hours. Inhalation exposure was estimated
to be between 166-3,700 ppm. After leaving work, the man
complained of headache, shortness of breath, and vomiting. He
admitted himself to a hospital '-5 days later and was diagnosed
as having acute renal failure. Kidney function returned to
normal after a 5-weeTc rest. It is important to note that
consistent moderate to heavy use of alcohol had been reported
in this case.
Another case of renal failure after accidental oral
ingestion was reported by Kleinfeld and Tabershaw (1954). A
patient who had ingested liquid TCE developed jaundice and
oliguria and died as a result of acute hepato-renal failure.
The amount ingested is unknown. The patient had been in good
health, was a moderate beer drinker, and had consumed several
bottles of beer on the morning of the accident.
Cardiac arrhythmia is the most frequent effect of TCE
on the heart. The most direct proof that TCE can cause
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VI-9
ventricular fibrillation and cardiac arrest is that these
changes can be demonstrated in electrocardiograms (ECGs) of
subjects who have accidentally ingested TCE. There are also
reports of TCE-related deaths occurring which were due to
ventricular fibrillation.
TCE is believed to sensitize the heart to epinephrine,
resulting in ventricular fibrillation; thus, any form of stress
would help induce cardiac sensitization. Anesthetic concentra-
tions of TCE have been shown to cause changes in the ECG indica-
ting tachycardia and arrhythmias. The ECG changes that occur
during TCE anethesia in man usually cease when exposure is
terminated.
Radonov et al. (1973)* reviewed the cases of 200,000
women given TCE as an analgesic during therapeutic abortions.
Seven deaths occurred; the deaths were attributed to cardiac
arrest.
Starodubtsev and Ershova (1976)* successfully used
TCE-air anesthesia in 128 cases of dental surgery in all three
levels of stage 1 anesthesia. The electrocardiograms showed no
apparent toxicity.
Four deaths were reported by Kleinfeld and Tabershaw
(1954) from chronic exposure to TCE. Exposure concentrations
•Foreign language article. The information was obtained
from a secondary source.
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VI-10
were unknown for three of the four cases. In one case, the
concentrations measured after the final incident were between
200 ppm and 8,000 ppm. All four workers continued to work at
their jobs even though they complained of nausea and vomiting,
drowsiness, and dizziness. They all died within a few hours
after leaving the plant. The mechanism of death was considered
to be ventricular fibrillation. Autopsies revealed no gross
anatomical abnormalities, but toxicological analysis of the tissues
revealed the presence of trichloroethylene.
C. Epidemiology
Grandjean et al. (1955) examined 50 workers exposed
to trichloroethylene in degreasing operations in the Swiss
mechanical engineering industry. Clinical exams, case histories,
trichloroacetic acid analysis of urines and other clinical blood
and urine analyses were done. Medical histories and urine samples
were taken from an additional 23 workers. Of the 50 examined
clinically, the average age was 43 years; length of exposure ranged
from 1 month to 15 year; workplaces were at both open and closed
degreasing tanks; air TCE concentrations in 96 samples ranged
between 1 and 355 ppm; and TCA in urines ranged from 8-444 mg/1.
These authors found that the air measurements did not
adequately reflect exposures due to great variations in concen-
tration with ventilation and operating schedules for degreasers.
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VI-11
They found that the general health of the men examined was
frequently bad; they felt this was related to the pay and the
poor standard of living. Although the authors stated they
were not acquainted with the normal incidence of disease in
Swiss workmen, they did not examine an unexposed control or
comparison group. Of greater importance they noted the follow-
ing dose-effect relationships: neurological and vegetative
nervous system disorders were more frequent in men with the
longest history of work exposure; subjective symptoms were the
same regardless of length of exposure; and subjective symptoms,
vegetative and neurological disorders, were more frequent in the
higher exposure groups as determined by the amount of trichloro-
acetic acid in urine. Persons with symptoms of chronic poison-
ing were from workplaces with measured air concentrations of
trichloroethylene between 20 and 80 ppm, and had between 10
and 250 mg/1 TCA in their urines. Finally, 10% of the workers
examined (5) showed evidence of slight impairment of liver
function but the authors were not sure if this could be related
to trichloroethylene exposure.
Bardodej and Vyskocil (1956) examined 75 persons
engaged in work with trichloroethylene, 12 of these in dry-
cleaning establishments and 55 in degreasing metal parts.
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VI-12
Length of exposure varied between one-half year and 25 years.
Air concentration in these plants varied between 0.028 and
3.4 mg TCE per liter (5-630 ppm). Eight disabled former
employees were also followed clinically. Intolerance to
alcohol, shivers, giddiness, neurasthenic syndrome with anxiety
states, bradycardia, and conduction disturbance of the heart
muscle were found to be significantly correlaterd (P <0.01)
with duration of exposure in years. The frequencies of
lacrimation. reddening of skin, decreased sensitiveness of
of hands, and disturbances of sleep among this mixed group
of workers was also significantly correlated with duration
of exposure (P <0.05). No control group was observed, and
the age and sex distribution in this group of workers was not
given in the description of this study.
Takamatsu (1962) studied 50 male and female workers
exposed to trichloroethylene during degreasing operations in
communicating machine factory for approximately 2-1/2 years.
Screening of workers in January and November, 1960, included a
questionnaire, blood cell count, blood pressure measurement
and analysis of urine for albumin, sugar, urobilinogen and TCA.
Urines were collected twice for each worker, once in the morn-
ing and once in the afternoon. On the basis of these results,
workers were selected for further examination, including fatigue
tests. A control group of 48 non-exposed workers was referred
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VI-13
to in the paper but no information on their characteristics
was given.
Eighty percent of the air values in January, and 70%
in November fell between 25-100 ppm TCE. Variations in air
concentrations were related to proximity to the degreasing
apparatus and location of air currents. A mean value of
urinary TCA found was 66 mg/1. Wide variations in TCA occurred,
depending again on proximity to main currents of vapor. A
majority of the 50 exposed workers had some complaints including
headache, vertigo, diplopia, sleeplessness, fatigue, etc.
Thirty-eight percent of the workers had slight or moderate
visual disturbances and 15% had diplopia. Diastolic blood
pressure exceeded the (unknown) control groups by 5 mm Hg. No
significant differences in blood count were observed. Decreases
in albumin concentration and increases in -globulin were
observed in exposed workers and were more frequent in those
exposed to highest air concentrations (150-250 ppm). Thirty
percent of the workers had albumin in urine and elevated uro-
bilinogen was found in 36% of workers. Some of the workers
reported constriction of the visual field.
Six employees who worked in the degreasing room, had
urinary TCA values from 370-1,000 mg/1, and frequent complaints
but few other clinical findings after short-term (7-30 days)
exposure. In workers with the highest exposures (150-250 ppm)
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VI-14
subjective complaints included headache, dizziness, giddiness,
drunken feeling, flushing of the face, burning throat, and
fatigue. TCA in urine was >100 mg/1 and increased during the
work week. Malfunctions of the liver were observed as were
changes in serum protein fractions. Workers exposed to 50-100
ppm complained of headache, burning eyes, flushing of the face
and fatigue. Half of these workers had urinary TCA exceeding
100 mg/1. Changes in serum prfctein fractions were observed
and visual disturbances were found in workers exposed for
several years. Work efficiency was reduced by the end of the
work week. Workers exposed to less than 50 ppm TCE showed no
apparent ill effects. Their urinary TCA was less than 50 mg/1.
Lilis et al. (1969) examined 70 workers in a Rumanian
semiconductor manufacturing plant. Eighty-three percent of
these workers were less than 30 years old and 74% were women.
Duration of exposure of 55% of these workers was less than 2
years and not more than 6 years for the remaining workers. Two
hundred fourteen air samples were collected at work places of
which 40% exceeded 50 mg/m3, and 12% were higher than 200 mg/m3.
Trichloroacetic acid concentrations in urines of these workers
exceeded 20 mg/1 in 46% of cases, 40 mg/1 in 24% of examined
workers, and exceeded 100 mg/1 in 7.3% of workers. Examination
included a detailed occupational history questionnaire with
information on the onset of and occurrence of persistent symptoms
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VI-15
The physical examination paid special attention to the nervous
system, heart and vessels and liver, and included electrocardio-
grams and presence of a metabolite of catecholamine in the urine.
Seventy-five percent of the workers examined reported prenarcotic
symptoms during the work shifts, including dizziness (88% of
cases), headache (74%), nausea (43%), euphoria (31%), palpitation
(29%) disturbances of vision (21%), and sleepiness at end of shift
(29%). These symptoms appeared daily in more than 1/3 of the
examined workers. Persistent symptoms of the pseudo-neurasthenic
type appeared after several months of exposure and included
fatigue, headache, irritability, anxiety, loss of appetite and
alcohol intolerance, along with signs of autonomic system
inbalance such as excessive sweating, palpitation, and nausea.
Physical exams showed few abnormalities. In 14% of cases moderate
tachycardia was found. Electrocardiographic abnormalities did
not appear to be related to their toxic exposure but were said
to be similar in frequency to every population group.
Systemic hemodynamic parameters were compared in 44
exposed workers and 10 non-exposed controls similar in age and
sex. Significantly raised mean values of stroke volume, cardiac
output, cardiac index and heart work in the exposed workers were
found and considered as signs of epinephrine type hypersympathi-
cotonia. In support of this, the authors reported that urinary
vanililmandelic acid (3-methoxy-4-hydroxymandelic acid) values
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VI-16
differed significantly between exposed workers and controls using
a student test (P <0.01).
The scanty description of the control group and their
participation in only selected parts detracts from this otherwise
interesting study. Also, the selection of exposed workers in
this study is not described in detail.
Szulc-Kuberska et al< (1976) studied 50 Polish workers,
28 men and 22 women, age 25-50 years, with between 1 and 23 years
of occupational exposure to trichloroethylene. Forty-four percent
(22) of these workers complained of excessive somnolence, 18% (9)
headaches, 20% drowsiness during work time. Two instances of loss
of consciousness at work were reported. Thirteen workers (26%)
reported intolerance to alcohol, 14 persons (28%) signs of
vegetative dystonia (excessive sweating) were present. Four men
reported impotencyi 3 women reported disorders of menstruation
including one with signs of menopause before age 35. Disturbances
of affection like apathy and inclination to weeping were also
observed. One person revealed signs of psycho-organic syndrome
with disturbances of memory, loss of interest and bradyphrenia.
A distinct correlation was found between the duration of work
and the frequency of occurrence of symptoms in these workers.
These authors also examined the auditory and vestibular
apparatus in 40 workers and reported perceptive hearing impair-
ments in 60% of TCE-exposed workers. Workers with previous or
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VI-17
present, exposure -to noise were excluded from this portion of the
study. Hearing disturbances found were always bilateral and
symmetric in the high frequencies beginning from 2,000-3,000 hz.
Hearing loss was not always correlated with vestibular pathology.
Impairment of auditory and labyrinthine function was found more
frequently among workers with longest period of work. These
authors also stated that disorders of hearing and vestibular
reactions are early signs of the adverse health status of workers
exposed to trichloroethylene.
In all of these workers the trichloroacetic acid level
in the urine exceeded 40 mg/1. No control group was examined,
and the type of work or circumstances of the workplace were
not described. Air concentrations of TCE in the workplace(s)
were also not given. The possible confounding effect of age and
length of employment on hearing loss is also not discussed. For
these reasons it is difficult to evaluate the results of this
study or to determine whether different results would be obtained
in a similar but unexposed (to TCE) industrial population.
Axelson et al. (1978) examined causes of death in a
small cohort of 518 men whose trichloroethylene exposure was
estimated through trichloracetic acid (TCA) in the urine.
Average TCA in urine above 100 mg/1 was considered high exposure
corresponding to more than 30 ppm in air. Close agreement was
found between observed and expected numbers of cancer deaths
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VI-18
based on national Swedish cause-age-specific death rates. Five
hundred forty-eight and 3,643 person-years of observation comprised
the high and low exposure groups, respectively. Due to the small
sample size, the cancer risk to man from trichloroethylene could
not be ruled out by these investigators, particularly with regard
to uncommon malignancies.
All of the epideraiolpgic studies described above examine
workers exposed to trichloroethylene in their workplace. A
frequent criticism of these studies is that they rarely have
included an unexposed group for comparison. Secondly, the
age and sex distribution in the groups of workers being examined
was not always provided in the papers, nor were other demographic
characteristics. Exposed groups were lumped together by intensity
of exposure and it was difficult to separate out effects which
may have been related to age, sex, or length of employment. Dis-
cussion of exposure to other chemical substances in these work-
places, and their possible influence on the findings was also
scanty, and made the lack of control groups a greater deficiency.
In view of these difficulties, information can best be derived
by examining consistent findings among studies conducted under
different circumstances. Four out of the six studies noted some
dose-effect relationship. All but one were able to document
exposure to trichloroethylene by measuring trichloroacetic acid
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VI-19
in the urine of workers. The most consistent findings were
complaints of fatigue, alcohol intolerance, disturbances of
sleep (both sleepiness and insomnia) headache, dizziness,
excess sweating, tachycardia or palpitations, and visual disturb-
ances. It should be noted that the studies may not have used
comparable methods of ascertaining these symptoms. Some of the
similarity of findings may have been related to historical
experience of previous investigators and the particular objective
of each study.
D. Synergistic and/or Antagonistic Response
Intolerance to alcohol has been reported among the
TCE-exposed workers. Stewart, et al. (1974) performed experiments
to substantiate this observation. They gave small oral doses of
ethanol to seven subjects and exposed them to 20,100 and 200 ppm
of TCE for 1, 3, or 7-1/2 hours. Transient vasodilation of the
superficial skin vessels reaching maximum intensity at 30 minutes
was noted.
Summary and Conclusions
1. Reports on the accidental ingestion of TCE are available.
A single oral dose of 7.6 g in a 4-1/2 year old child produced
toxic effects. Assuming a 20 kg body weight of the child, the
estimated dose is approximately 380 mg/kg. In another incident,
an adult who ingested 21 g trichloroethylene exhibited symptoms
such as vomiting, abdominal pain, inebriation, transient uncon-
sciousness and myocardial infarction. In the second case, the
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VI-20
dose is estimated at 300 mg/kg. Therefore, the lowest toxic
dose in humans is 300-380 mg/kg.
2. Occupational exposures give some information with regard
to exposure and obvert adverse health effects. However, these
data do not provide precise exposure levels and are cofounded by
the fact that the workers are also exposed concurrently to other
chemicals. And it is not possible to associate adverse health
effects with the chemicalfs) with certainty. In an electroplating
plant, when the exposure was between 627-2093 mg/m3 for 2-3 weeks,
the workers complained of headaches, muscle and joint pains,
nausea, vomiting, loss of appetite, depression, dizziness a-nd
narcosis. The workers had liver damage as indicated by chlo-
esterol flocculation test and hyperglobinemia.
3. Epidemiological evidence cannot be related to the exposure
levels with confidence, however, exposure of workers to trichloro-
ethylene and its association with observed health effects - fatigue,
dizziness, alcohol intolerance, conduction of disturbance of heart
muscle, nervous system disorders, increase in plasma Y -globulin
and decrease in albumin concentration, is worth mentioning. Some
workers had albumin and elevated urobilinogen in urine. These
studies cannot be used for determing recommended maximum
contaminant levels.
4. Intolerance to ethanol among the factory workers exposed
to ethanol has been reported.
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VII. MECHANISMS OF TOXICITY
Exposure to trichloroethylene has been reported to
produce: disturbances in the central nervous system, arrhythmia
(cardiotoxic effect), hepato- and nephrotoxic effects and
carcinogenic response in animals. Very little is known about
the mechanisms by which TCE exerts the bioeffectsr however,
several attempts have been made to elucidate the mechanisms
for some of these bioeffects.
Information concerning the hepatotoxic and possibly
potential carcinogenic effects have been generated by the
experiments of several workers. The first step in this
mechanism appears to involve epoxidation of trichloroethylene
in the mammalian system. This system requires cytochrome
P-450 and the NADPH-generating enzymes. The trichloroethylene-
epoxide thus formed may interact: (1) with low molecular
weight nucleophiles by conjugation reaction; (2) with cellular
macromolecules by alkylation; and (3) with water to produce
diols or undergo intramolecular rearrangement.
The evidence for macromolecule binding of TCE has been
generated by Allemand et al. (1978); Uehleke and Poslawski-
Tabarelli (1977); Van Duuren and Banerjee (1976); and Bolt and
Filser (1977). In in vitro experiments, Allemand et al. (1978)
incubated 14C-trichloroethylene with rat liver microsomes, with
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VI I-2
and without the NADPH-geDerating system. Without the NADPH-gen-
erating system, there was negligible radioactivity bound to
raicrosomal proteins. This suggests that TCE itself does not
bind to proteins. The TCE-binding was increased after pretreat-
ment with microsomal enzyme inducers and decreased under the
influence of CO/O2 atmosphere and piperonyl butoxide—the inhib-
ibitor of microsomal enzymes. Intraperitoneal administration
of 100 uraol (13.14 mg/kg) of 'TCE to normal and phenobarbital-
pretreated animals gave higher activity in the treated animal
tissues; hepatic-protein bound radioactivity was 40 times more
than that of the muscle protein. Inhalation exposure of male
Wister rats to 14C-TCE for 5 hours at concentrations of 9 ppm,
100 ppm, and 1,000 ppm (49, 545, 5,450 mg/m3) demonstrated
irreversibly-bound radioactivity maximum to the liver and
minimum to the muscle (Bolt and Filser, 1977) . These authors
also carried out ii\ vitro covalent-binding experiments utilizing
14C-TCE. Incubating 14C-TCE with NADPH-generating liver micro-
somes and albumins and globulins, Bolt and Filser (1977) found
large amounts of radioactivity bound to albumin (bovine and
rabbit). Binding was reduced by the addition of glutathione.
This was in contrast to vinyl chloride where the metabolites
preferentially bind to SH groups.
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VI I-3
VanDuuren and Banerjee (1976) incubated rat liver
microsomes with 14C-TCE. The results showed that TCE binds
covalently to microsomal protein. The binding was decreased
by the addition of microsomal inhibitors—7,8-benzoflavone,
blocked by compound SKF-525A and enhanced by pretreatment of
the animals with phenobarbital. The experiments with 3,3,3-
trichloropropene oxide (TCPO), a potent inhibitor of epoxide
hydrase showed that this agent causes an enhancement of TCE
binding to microsomal proteirrs. These results suggest that
the binding is via an epoxide or other related electrophilic
species. Similar results have been obtained by Uehleke and
Poplawski-Tabarelli (1977). Mice were injected intraperitoneally
with solution of 14C-labeled TCE. Microsomes contained the
highest number of irreversibly bound radioactivity. The
concentration declined after 6 hours.
The information cited above suggests that the metabol-
ites of TCE covalently bind with microsomal proteins and the
binding can be increased/decreased by utilizing the enzyme in-
ducer and inhibitors. Covalent protein binding of metabolites
of xenobiotics had been used as a tool that allow us to detect
whether reactive and possibly hazardous, metabolites are formed.
In addition, interaction with nucleic acids moieties has to be
examined.
DiRenzo and his coworkers (1982) studied ^n vitro cova-
lent binding of a series of !4C-labeled aliphatic halides to calf
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VI1-4
Table VII-1
MICROSOMAL BIOACTIVATION AND COVALENT BINDING OF ALIPHATIC HALIDES
TO CALF THYMUS DNA
Aliphatic halidesa Binding to DNAb
1,2 Dibromoethane 0.52+0.14(6)
Bromotrichloromethane 0.51+0.18(6)
Chloroform 0.46+0.13(6)
Carbon tetrachloride 0.39+0.08(6)
Trichloroethylene 0.36+0.14(7)
1,1,2-Trechloroethane 0.35+0.07(7)
Dichloromethane 0.11+0.05(5)
Halothane 0.08+0.01(6)
1,2-Dichloroethane 0.06+0.02(6)
1,1,1-Trichloroethane 0.05+0.01(3)
a 14c-iabeled aliphatic halides (1 mM) were incubated with hepatic
microsomes. Carbon tetrachloride, bromotrichloromethane and halothane
were incubated under an N2 atomosphere while all other incubations
were under an 03 atmosphere for reasons as stated in MATERIALS AND
METHODS.
b nmol bound/mg DNA/h. Values are the mean + standard deviation
for the number of experiments in parentheses.
Source: DiRenzo et al. 1982
thymus DNA following bioactivation by hepatic microsomes isolated
from phenobarbital-treated rats. Six compounds—1,2,-dibromo-
ethane, bromotrichloromethane, trichloroethylene, carbon tetra-
chloride, chloroform and 1,1,2-trichloroethane were incubated for
60 minutes (time-period previously determined to produce maximal
covalent binding). Halides to DNA adducts were isolated utiliz-
ing Sephadex LH-20 column chromatography. Table VII-1 gives
comparative binding to DNA of the selected aliphatic halides.
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VI I-5
It is noteworthy that the compounds containing bro-
mine are readily bioactivated and.bound to DNA to a greater
extent than the related chlorine-containing compounds in this
series. This is illustrated by the binding to DNA of 1,2-dibro-
moethane (0.52+0.14) and 1,2-dichloroethane (0.06^0.02). Also
those aliphatic halides that had the highest levels of covalent
binding are those most frequently shown to be carcinogenic in
laboratory animals.
Banerjee and Van Duuren (1978) carried out studies
on the in vitro covalent binding of trichloroethylene to salmon
sperm DNA, in the presence of microsomal preparation from
B6C3F1 hybrid mice. TCE metabolite-DNA adduct was purified
by precipitation/reprecipitation technique with solvents. It
was checked for protein and RNA contamination. TCE-DNA binding
was dependent on the concentration of microsomal protein. Amount
of binding of TCE to DNA in the presence of microsomes from male
mice was higher than those from female mice. This correlates
with the NCI cancer bioassay on trichloroethylene. The binding
to DNA was enhanced by the in vivo pretreatment of the animals
with phenobarbital.
12. v*vo TCE-DNA binding researches were performed by
Stott and his coworkers. Male BgC3Fi1 mice were dosed with
1,200 mg/kg 14C-TCE by gavage in corn oil. The animals were
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VI1-6
sacrificed 5 hours later by decapitation. Livers were frozen
and processed for DNA isolation and purification. Three out
of four animals had a maximum estimate of the average DNA
level of 0.62+0.42 alkylations/106 nucleotides. The authors
suggested an epigenetic mechanism of tumor formation in the
B6C3F1 mouse because of the so-called low maximum estimation
of alXylation. This conclusion appears to be far reaching
based on a single experiment where only a single dose was
given and only four animal were used. In addition their esti-
mate of alkylation with higher standard deviation does not
instill confidence in the mind of the reviewer.
In order to establish a correlation of covalent
binding and hepatotoxicity, Allemand et al. (1978) demonstated
that intraperitoneal administration of TCE (1,460 mg/Tcg) to
rats resulted in raised SGPT levels, without detectable
histologic lesion of the liver. Phenobarbital pretreatment
of the animals increased hepatic cytochrome P-450, in vitro
formation of the chemically reactive metabolite of TCE, the
amount of metabolite bound in vivo, and the hepatotoxicity of
a (1,460 mg/Tcg) dose of TCE. The inhibition of TCE metabolism
with CoCl2 decreased the hepatic cytochrome P-450, the in
vitro formation rate of the chemically reactive metabolite
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VI I-7
of TCE, and the hepatotoxicity of a 1 ml/kg dose of TCE. In
an inhalation experiment, Carlson (1974) observed enhancement
of TCE hepatotoxicity in male rats pretreated with phenobarbi-
tal and 3-methylcholanthrene. Indices of hepatotoxicity were
serum isocitrate dehydrogenase, SGPT, SCOT and hepatic glucose-
6-phosphatase; while TCE exposure levels ranged from 10,400 ppm
to 6,900 ppm, lasting for a 2-hour periods. Moslen ejt a_l. (1977)
also exposed male rats, after pretreatment with five different
inducers of hepatic mixed function oxidases, to 1% (10,000 ppm)
TCE for 2 hours. The magnitude of induction of cytochrome
P-450 correlated with the extent of TCE-induced liver injury
measured by serum transaminases level (r=0.95), with prolonga-
tion of anesthesia recovery time (r=0.95), and with enhanced
urinary excretion of trichlorinated metabolites (r*0.88).
Factors other than enzyme induction could also influ-
ence the hepatotoxicity of trichloroethylene. For example,
influences include changes in the redox state of the hepato-
cytes or depletion of co-factors required for specific metabolic
steps. Cornish and Adefunin (1966) reported increased hepato-
toxicity of rats pretreated with ethanol. An explanation for
observed interaction of ethanol and trichloroethanol is the
availability for NAD and NADPH—the co-factors required for
the metabolism of trichloroethylene—at the step involving
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VI1-8
bi©transformation of chloral hydrate. The concentration of
glutathione, an endogenous compound responsible for varied types
of metabolic reaction in mammalian systems has been affected by
the administration of trichloroethylene to the animals. After
TCE administration to normal rats, hepatic glutathione was
decreased. This was not true when the animals were pretreated
with the chemicals which inhibit metabolism, suggesting that
glutathione depletion was related to trichloroethylene meta-
bolism. Also, in vitro addition of glutathione to the incuba-
tion mixture decreased the amount of trichloroethylene metabol-
ite bound to microsomal proteins. Earlier it had been reported
that tissue binding of TCE metabolite was related to hepatotoxi-
city.
Salvolainen (1977) reviewed some aspects of the
mechanisms by which industrial solvents produced neurotoxic ef-
fects. Neurotoxic action may be described as responses that
are related to nervous system function, to structure, or to
both. The acute effects appear to be derived from the direct
interaction of solvents on nerve cell membranes, whereas the
development of chronic effect depends more on the metabolic
effects of the individual chemical. To elicit anesthesia in
surgical operations may be considered an example of the former
effect. The majority of such effects are probably reversible.
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VII-9
It appears that for anesthesia, TCE would fall in the category
of chemicals which interfere with nerve cell membrane. For
chronic effect, metabolic changes have been cited for the
neurotoxic effects of many chemicals. Specific effects on
neuronal metabolisms and functions due to the exposure to TCE
have not been examined.
Summary and Conclusions
1. Evidence has been generated that it is the metabolite
of TCE rather TCE which is responsible for the hepatotoxic and
potential carcinogenic response.
2. A metabolite of TCE covalently binds with the macromole-
cules including DNA.
3. It appears that TCE may fall in the category of chemicals
which interfere with nerve cell membrane for its anesthetic response
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VIII. RISK ASSESSMENT
The National Academy of Sciences (NAS, 1977) made
an assessment of human cancer risk associated with TCE in
drinking water. The risk assessment was based upon the
results of a carcinogenesis bioassay experiment with animals
(NCI, 1976). In this study, highly significant differences in
the incidence of hepatocellular carcinomas were found between
treated and controlled mice of both sexes.
The available sets of dose-response data were individual-
ly considered according to the risk section in the chapter on
margin of safety. Each set of dose response data was used to
statistically estimate both the lifetime risk and an upper 95%
confidence bound on the lifetime risk at the low-dose level. These
estimates are of lifetime human risks and have been corrected for
species conversion on the dose/surface area basis. The risk
estimates are expressed as a probability of cancer after a life-
time consumption of 1 liter of water/day containing Q ppb of the
compound of interest. For example, a risk of 1 x 10~6 Q implies
a lifetime probability of 2 x 1CT5 of cancer if 2 liters/day were
consumed and the concentration of the carcinogen was 10 ppb (i.e.,
Q=10). This means that at a concentration of 10 ppb during a
lifetime of exposure this compound would be expected to produce
one excess case of cancer for every 50,000 persons exposed. If
the population of the United States is taken to be 220 million
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VIII-2
people this -translates into 4,400 excess lifetime deaths from
cancer or 62.8/year. Since several data sets is typically
available the range of the low-dose risk estimates are reported.
For TCE at a concentration of 1 ug/liter (Q=l) the estimated
risk for man would be 0.36-1.1x10"^ 0. The upper 95% confidence
estimate of risk at the same concentration is 0.55-1.6xlO~7.
It should be emphasized that these extrapolations
are based on a number of unverifiable assumptions: extrapola-
tion from high exposure to low exposure in mice, on the basis
of a multi-stage mathematical model; extrapolation from mouse
to man, on the basis of the surface-area rule; and extrapolation
from gavage exposure to oral exposure assumed equal. These
estimated human risks should be taken as crude estimates at
best.
The CAG, using an "improved" multi-stage model has
determined that 27 ug/1 at 2 liters/day over a lifetime would
result in an excess cancer risk estimate of 10~5 at the 95%
confidence limit.
The National Academy of Sciences (HAS) and EPA's
Carcinogen Assessment Group (CAG) have calculated projected
incremental excess cancer risks associated with the consumption
of a specific chemical via drinking water by mathematical
-79-
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VIII-3
extrapolation from high-dose animal studies. Using the risk
estimates generated by the HAS (197?-1979) where the multi-stage
model was utilized, that range of trichloroethylene concentra-
tions were computed that would nominally increase the risk of
one excess cancer per million (106), per hundred thousand (105)
or per ten thousand (104) people over a 70-year lifetime assum-
ing daily consumption at the stated exposure level. From the
NAS model it is estimated at the 95% confidence limit that con-
suming two liters per day over a lifetime having a trichloroethy-
lene concentration of 450 ug/1, 45 ug/1 or 4.5 ug/1 would increase
the risk of one excess cancer per 10,000; 100,000 or 1,000,000
people exposed, respectively. Using the revised GAG approach
and thus the "improved" multi-stage model, it can be estimated at
the 95% confidence limit that consuming two liters per day over a
lifetime having a trichloroethylene concentration of 280 ug/1,
28 ug/1, or 2.8 ug/1 would increase the risk of one excess cancer
per 10,000; 100,000 or 1,000,000 people exposed, respectively.
The numerical differences observed after utilizing the NAS and
the CAG risk estimates are partly due to the fact that the dose
extrapolation model used by the two groups is similar but not
identical. The NAS has used the multi-stage model whereas the
CAG has used the "improved" version of the multi-stage model
recently discussed by Crump (U.S. EPA, 1980). In addition, the
selection of the data and other parameters in each model will
also result in some differences in risk assessments.
-80-
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VIII-4
Table VIII-1
Drinking Water Concentrations And Associated Cancer Risks
Range of Concentrations (ug/1)*
Excess Lifetime
Cancer Risk
ID'4
10-5
10~6
CAG
(95% confidence
limit)
280
28
2.8
NAS
(95% confidence
limit)
450
45
4.5
NAS
(point estimate)
1400-450
140-45
14-4.5
*Assume 2 liters of water are consumed per day.
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IX-1
IX. Quantification of Toxicological Effects
The quantification of toxicological effects of a chemical
consists of an assessment of the non-carcinogenic and carcino-
genic effects. In the quantification of non-carcinogenic
effects, an Adjusted Acceptable Daily Intake (AADI) for the
chemical is determined. For ingestion data, this approach
is illustrated as follows:
Adjusted ADI = (NOAEL or MEL in mg/kg)(70 kg)
(Uncertainty factor)(2 liters/day)
The 70 kg adult consuming 2 liters of water per day is used
as the basis for the calculations. A "no-observed-adverse-effeet-
level" or a "minimal-effect-level" is determined from animal
toxicity data or human effects data. This level is divided
by an uncertainty factor because, for these numbers which are
derived from animal studies, there is no universally acceptable
quantitative method to extrapolate from animals to humans,
and the possibility must be considered that humans are more
sensitive to the toxic effects of chemicals than are animals.
For human toxicity data, an uncertainty factor is used to
account for the heterogeneity of the human population in
which persons exhibit differing sensitivity to toxins. The
guidelines set forth by the National Academy of Sciences
(Drinking Water and Health, Vol. 1, 1977) are used in estab-
lishing uncertainty factors. These guidelines are as follows:
an uncertainty factor of 10 is used if there exist valid
experimental results on ingestion by humans, an uncertainty
factor of 100 if there exist valid results in chronic or long-
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IX-2
term feeding atudies on experimental animals, and an uncertainty
factor of 1000 is used if only limited data are available.
In the quantification of carcinogenic effects, mathematical
models are used to calculate the estimated excess cancer
risks associated with the consumption of a chemical through
the drinking water. EPA's Carcinogen Assessment Group has
used the multistage model, which is linear at low doses and
does not exhibit a threshold, to extrapolate from high dose
animal studies to low doses of the chemical expected in the
environment. This model estimates the upper bound (95%
confidence limit) of the incremental excess cancer rate that
would be projected at a specific exposure level for a 70 kg
adult, consuming 2 liters of water per day, over a 70 year
lifespan. Excess cancer risk rates also can be estimated
using other models such as the one-hit model, the
model, the logit model and the probit model. Current
understanding of the biological mechanisms involved in cancer
do not allow for choosing among the models. The estimates
of incremental risks associated with exposure to low doses
of potential carcinogens can differ by several orders of
magnitude when these models are applied. The linear, non-
threshold multi-stage model often gives one of the highest
risk estimates per dose and thus would usually be the one
most consistent with a regulatory philosophy which would
avoid underestimating potential risk.
t
The scientific data base, which is used to support the
estimating of risk rate levels as well as other scientific
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IX-3
endeavors, has an inherent uncertainty. In addition, in
many areas, there exists only limited knowledge concerning
the health effects of contaminants at levels found in drinking
water. Thus, the dose-response data gathered at high levels of
exposure are used for extrapolation to estimate responses at
levels of exposure nearer to the range in which a st idard
might be set. In most cases, data exist only for am
uncertainty exists when the data are extrapolated to humans.
When estimating risk rate levels, several other areas of
uncertainty exist such as the effect of age, sex, species
and target organ of the test animals used in the experiment,
as well as the exposure mode and dosing rates. Additional
uncertainty exists when there is exposure to more than one
contaminant due to the lack of information about possible
additive, synergistic or antagonistic interactions.
Trichloroethylene studies which provide dos<
adverse health effects in humans are not available. Therefore,
estimations based upon the best scientific judgments in
experimental animals are required to quantify toxicological
effects (QTE) with respect to concentrations in drinking
water. With this objective in mind, this section analyses
the data taking into consideration interspecies variation,
observed adverse health effects (both carcinogenic and non-
carcinogenj.c) and dosages.
-------
A. Non-Carcinogenic Effects
Among the acute and chronic adverse effects due to TCE
exposure, hepatotoxicity appear to be of most significance.
All the animal species which have been studied, respond to
the hepatotoxic effects of TCE - intensity of response dependent
upon the dose and the duration of exposure. There are re --ts
concerning the nephrotoxic effects of trichloroethylene.
Central nervous system and cardiotoxic effects are observed
at very high concentrations.
Several inhalation studies, after single or multiple exposures
have provided observations on hepatotoxic effects. Kylin et
al. (1962) compared the hepatotoxicity of chloroform, trichloro-
ethylene and tetrachloroethylene. Mice were given TCE by
inhalation for a single 4-hour time-period. The animals were
sacrificed on the third day; the livers were analyzed by
histological examination and by acetone-hexane extraction
for fat. In addition, activity of serum ornithine carbamyl
transferase was determined. Trichloroethylene at a concentration
level of 6,400 ppm produced no significant damage to the liver.
In this study, trichloroethylene was the least hepatotoxic,
whereas chloroform was the most. Similar results were obtained
by Plaa ejt al. (1958) and Gehring (1968) when animals were
exposed to halogenated hydrocarbon solvents by subcutaneous
injection and by inhalation. The results of these workers
indicated that the halogenated hydrocarbon solvents rank in
the order of their decreasing capacity to cause liver dysfunction:
carbon tetrachloride, chloroform, 1,1,2-trichloroethane,
-------
IX-&
tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethane
Multiple inhalation exposure studies have been reported
utilizing mice, rats and dogs. Seifter (1944) observed
degeneration of liver parenchyma cells in dogs that were
exposed either to 750 ppm TCE 8 hours/day, 6 days/week for 3
weeks or 500 to 750 ppm TCE 6 hours/day, $ days/week for 8
weeks. Slight fatty infiltration of the liver of mice was
detected by Kylin et al. (1965). These workers exposed
female albino mice to 1,600 ppra TCE by inhalation for 4
hours daily, six days a week, over periods of one, two1, four
and eight weeks. The increase in liver fat content was
detectable after one week's exposure and subsequently the
liver fat showed no further increase. In terms of fatty
degeneration of liver, the authors noticed that tetrachloro-
ethylene was approximately 1/10 times less toxic than tri-
chloroethylene. Male Wistar II rats inhaling 55 ppm TCE for
14 weeks, exhibited elevated liver weights but did not cause
pathological changes measured by histopathological examinations,
liver function tests, renal function tests and blood glucose
(Kimmerle and Eben, 1973). Four animal species - rabbits,
guinea pigs, rats and monkeys were exposed seven hours daily,
5 days a week, 100 to 3,000 ppm TCE vapors for approximately
up to six months by Adams et al. (1951). Rats exposed to
300 - 3,000 ppm TCE for a period of 36 days (total of 27
exposures) showed an increase in liver and kidney weights.
However, histopathological examination of the tissues failed
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IX-6
to reveal any abnormality in male rats, but some female rats
showed fat vacuoles in the cytoplasm of the liver. Rats
exposed to 200 ppm TCE for 205 days (total exposures 151)
showed no significant abnormality from the controls. The
authors concluded that the maximum concentrations without
adverse effects were as follows: monkey, 400 ppm; rat and
rabbit, 200 ppm; guinea pig, 100 ppra.
Because of the effects of TCE.on the nervous system, it has
been used as a general anesthetic agent. Studies performed
as early as 1944, give information concerning the blood
concentration of TCE for lethal as well as anesthetic effects.
Dogs, rabbits, guinea pigs and cats were administered TCE by
inhalation and blood levels were determined at death and
anesthesia stages. Lethal blood TCE concentration in dogs
were found to be 100-110 mg/100 ml blood. At the anesthetic
stage, TCE blood levels were 24 - 37, 23 - 28, 14-18, 25 -
32 mg/100 ml blood for dogs, rabbits, guinea pigs and cats,
respectively. As with the liver, guinea pigs appear to be the
most sensitive'species among the studied experimental animals
with respect to the anesthetic response. The blood-brain
ratio at anesthetic dosages were approximately 1:2 for both
guinea pigs and dogs (Kulkarni, 1944).
Hisptopathological changes in neural tissues have been observed
on acute and long-term exposure of animals to TCE. A single
exposure of dogs to 30,000 ppm TCE in air resulted in death
within 20 minutes. No obvious changes were found in the nervous
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IX-7
system. In a longer-term experiment, the animals were
subjected to TCE concentration ranging from 500 - 3,000 ppm
for periods varying 2-8 hours daily, often for 5 days
weekly. The total exposure period was between 60 - 162 hours.
The exposures appear to selectively destroy the Purkinje
layer of the cerebellum. The cerebral hemispheres showed
mild changes — scattered cortical neurons became swollen or
pyknotic and the white matter of the myelin developed a mild
focal swelling (Baker, 1958)'. Bartonicek and Brun (1970)
injected TCE intramusculary in female rabbits and observed
moderate .neurological changes in the exposed animals. The
dosage regimen included subacute exposure for 29 days, injected
animals with 2.47 g/kg body weight three times a week. For
chronic exposure experiment, the animals were injected
intramuscularly for 41 to 247 days with 1.62 g/kc
week. The rabbits were sacrificed at different times during the
test and the brains examined histologically and histochemically
for any pathological change. Round cell infiltration around
blood vessels and in the parenchyma occurred in all animals of
the subacute and in one of the chronic experiments but not in
the controls. Disappearance of Purkinje cells and basket
cells was definitely shown only in the chronic experiment.
Grandjean (1960) exposed male rats to 200 and 800 ppm TCE
vapors for 4 to 11 weeks. The rats were subjected to a single
3-hour TCE exposure just before testing. After the exposure,
trained rats responding to signals, climbed up a rope to reach
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IX-8
a feeding through where they found a small dextrose pellet
as a reward. The results indicated that the increase in the
number of spontaneous climbs after exposure to the solvent is
significant in comparison with the control tests. The observed
effect was not dose-dependent. The authors concluded that TCE
in doses studied modified the psychological equilibrium of rats
by increasing excitability. The author in the 1963 report
described the effect of TCE vapors on the swimming performance
and on the motor activity of rats. The animals were exposed
for six hours and swimming tests were performed 5 - 1*5 minutes
later. At 400 ppmr TCE retarded only the rats swimming with
an additional load in a manner barely significant while 800
ppm adversely affected the performance, both with load and
without, in a significant manner. One hour after termination
of exposure, no significant changes in the swimming times
were observed.
Reports on the accidental ingestion of TCE are available.
A single oral dose of 7.6 g in a 4 1/2 year old child produced
toxic effects. Assuming a 20 kg body of weight of the child,
the estimated dose is approximately 380 mg/kg. In another
incident, an adult who ingested 21 g of trichloroethylene
exhibited symptoms such as vomiting, abdominal pain, inebriation,
transient unconsciousness and myocardial infarction. In the
second case, the dose is estimated at 300 mg/kg. Therefore,
the lowest toxic dose in humans is 300-380 mg/kg.
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IX-9
Occupational exposures give some information with regard to
exposure and obvert adverse health effects. However, these
data do not provide precise exposure levels and are cofoun-
ded by the fact that the workers are also exposed concurrently
to other chemicals. Also, it is not possible to associate
adverse health effects with the chemical(s) with certainty.
In an electroplating plant, when the exposure was between 627-
2093 mg/m^ for 2-3 weeks, the workers complained of headaches,
muscle and joint pains, nausea, vomiting, loss of appetite,
depression, dizziness and narcosis. The workers had liver
damage as indicated by .Cholesterol flocculation test and hyper-
globinemia.
Epidemiological evidence cannot be related to the exposure
levels with confidence, however, exposure of workers to
trichloroethylene and its association with observed heaita
effects - fatigue, dizziness, alochol intolerance, conduction
of disturbance ;of heart muscle, nervous system disorders,
increase in plasma Y -globulin and decrease in albumin
concentation, is worth mentioning. Some worker had albumin
and elevated urobilinogen in urine. These studies cannot be
used for determining the quantification of toxicological effects
(QTE).
B. Quantification of Non-Carcinogenic Effects
Similarities in bioeffects, across species - humans,
dogs, rabbits, guinea pigs, rats and mice, as a result of
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IX-10
TCE exposure either by inhalation, intramuscular injection
or gavage have effects on the central nervous system, liver
and the heart. TCE also has been .shown to be carcinogenic
in mice in two studies. Because of the special nature of the
carcinogenic effect, it is discussed separately in this
section.
The central nervous system and the liver of the mammalian
system appear to be the sensitive endpoints with respect to
the adverse health effects. There are limited data concerning
the dosage, duration of exposure and the effects on the
central nervous system. There is only one study in which
human volunteers were exposed to 600 mg/m3 TCE for two 4-hr.
periods. In this study psychophysiological changes were
noted in human volunteers. This study cannot be used for
recommending a longer-term exposure or QTE.
Liver toxicity should be used as an end point, for et^
QTE for TCE in drinking water. TCE has been shown to damage
liver of humans as indicated^by cholesterol flocculation test
and hyperglobinemia. The exposure related to this effect was
between 627-2093 mg/m3 for 2-3 weeks. The exposure in
mg/kg/day can be estimated as:
627 x 10 x 0.3 =26.B7 rag/kg
70
627 = lowest estimated exposure dose in mg/m3
10 = cubic meter of air-TCE mixture inhaled
0.3 = assumed fraction of TCE retained in the body
after inhalation
70 = average body weight of an adult human
-------
IX-11
Rats exposed to 300 mg/m-* (55 ppm) , five days a week for 14
weeks, had elevated liver weights. Assuming the lung-whole
body weight ratios for humans (adults) and rats (adults) to
be roughly equivalent, the total dose of trichloroethylene to
humans can be estimated. The calculations are:
(300 mg/m3) 8 mg3/day (5)(0.30) = 514 mg/day
Where: 55 ppm = 300 mg/m^ minimum effect level
8 n»3 = air inhaled duriny the experiment
5/7 = fraction converting from 5 to 7-day exposure
0.30 = absorption rate
Estimated dosages which adversely affect the liver of humans are
26.87 - 89.7 mg/kg for an exposure period of 2-3 weeks. Two -
three weeks exposure is too short a period to estimate an ADI
for humans. Furthermore, this was a very crude estimate and
the studies were not well controlled. The estimate of 7.34
mg/kg (513.8 mg for a 70 kg adult) as an adverse health
effect dose from the rat study appear to be a reasonable
level for the calculation of an ADI.
If 7.34 mg/kg dose is accepted as a minimum effect dose, an
uncertainty factor of 1,000 can be applied to calculate an
ADI. The calculation is:
ADI = 7.34 rag/kg x 70 kg - Q.514 mg/day
1000
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IX-12
The ADI of TCE using non-carcinogenic data and assuming 100
percent exposure from drinking water is 0.514 mg/day. It should
be appropriately reduced if there is also TCE exposure from
other sources such as food and air. In case, 100 percent
exposure is assumed from drinking, then an adjusted ADI can be
calculated as:
Adjusted ADI = 0.514 mg = Q.257 mg/1
2 1
C. Carcinogenic Effectsv
Bacterial mutagenesis systems are most commonly used as a
screening technique to determine the mutagenic and carcinogenic
potential of chemicals. Trichloroethylene was found mutagenic
in Salmonella typhimurium strain and the E. coli K 12 strain,
utilizing liver_microsomes for activation (Greim et al. 1975;
1977). Bartsch et al. (1979) used S-9 fractions from liver
specimens for activation instead of microsomes for mutagenesis
test. The authors reported trichloroethylene as marginally
mutagenic. Waskell (1978) reported trichloroethylene nonmutagenic
in Ames test system with activation. The negative response
obtained by later research cannot be explained at the present
time.
Sacchromyces cerevisiae (yeast), and Fisher rat embryo,
have also been used to study mutagenic response. After
activation with liver microsomal fractions, trichloroethylene
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IX-13
was mutagenic in strains of yeast such as sacchromyces
cervevisiae strains 04, 07 and XV185-14C (Bronzetti e_t al.
1978, Shahih and Von Borstel 1977). Price et al. (1978)
tested TCE for in vitro cell transforming potential in a
Fisher rat embryo system (F1706). The transformed cells grew
in a semisolid agar and produced undifferentiated fibrosarcomas
when inoculated into new born Fisher rats.
The National Cancer,:Institute (NCI) (1976) reported that TCE
induced cancer in mice. TCE was administered by oral gavage
five times per week for 78 weeks. The time weighted average
daily doses were 1,169 and 2,339 mg/kg for male mice and 869
and 1,739 mg/kg for female mice. These tests were conducted
using industrial grade (99% pure) TCE on Osborne-Mendel rats
and B6C3F1 mice. A complete necropsy and microsc^ nluation
were conducted on all the animals (except 7 who died at
unscheduled -times out of the original 480).
No significant difference was noted in neoplasms between
experimental and control groups of rats. However, in both
male and female mice, the higher dose induced primary malignant
tumors in the liver. For males, 26 of 50 mice who received
the low dosage and 31 of the 48 mice who received the high
dosage developed hapatocellular carcinomas while only 1 out of
20 of the controls showed neoplasms. In female mice, 4 of
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IX-14
the 50 receiving the low dosage and 11 out of 47 receiving
the high dosage developed neoplasms as compared to 0 out of
20 of the controls.
In the NCI study cited above, the test chemical, trichloro-
ethylene, was later found to contain epichlorohydrin - a
carcinogen. Therefore, NCI repeated the bioassay with
epichlorohydrin-free trichloroethylene. Rats (F344/N) and mice
(B6C3F1) of both sexes were used. Trichloroethylene was
mixed with corn oil and administered by gavage five times per
week for 103 weeks. Rats received dosages of 500 and 1,000
rag/kg. These dose levels were lower than the initial doses
used in the earlier bioassay in Osborne-Mendel rats (650 and
1,300 mg/kg for both sexes). As with the rats, the dosage
levels used in the mice were lower than in the earlier study.
The dose selected for the study in mice was 1,000 mg/kg for
both sexes.
Trichloroethylene was not found to be carcinogenic for female
F344/N rats. The experiment with male rats was considered
inadequate because these rats received dose levels of
trichloroethylene which exceeded the maximum tolerated dose.
Trichloroethylene was carcinogenic for both sexes of B6C3F1
mice, producing hepatocellular carcinomas in males and females.
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IX-15
D. Quantification of Carcinogenic Effects;
To assist the regulators in making decision for the Control of
Chemical Carcionogens in the environment, several scientists
have attempted to estimate excess cancer risk on exposure from
carcinogens. With respect to contamination of water with
carcinogens, the National Academy of Sciences and EPA's
Carcinogen Assessment Group (CAG) calculated additional
cancer risk estimates.
Using the revised CAG approach and thus the "improved" multi-
stage model, it can be estimated that water with TCE concen-
trations of 280 ug/1, 28 ug/1 or 2.8 ug/1 would increase the
risk of one excess cancer per 10,000; 100,000 or 1,000,000
people exposed, respectively. These estimates were
from the NCI bioassay data utilizing TCE contaminated with
epichlorohydrin. Since then, NCI-bioassay utilizing epichloro-
hydrin free TCE has become available, the data form this
bioassay has been reviewed and evaluated for carcinogenicity.
Epichlorohydrin-free TCE has again been reported to be
carcinogenic in mice.
E. QTE Development
Several organizations have attempted to derive acceptable
levels of TCE in water. These values are given in Table IX-1.
The National Academy of Sciences (1977) estimated excess
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IX-16
cancer risk due to the exposure of humans to TCE in drinking
water. They used a multistage model for their calculations.
Cancer risk estimate at the upper 95 percent confidence
level for 1 ug/1 TCE was 0.55 x 1Q~7. This translated
into a concentration of 45 ug/1 for a risk of 10~^. The
estimates reported by the EPA's Office of Water Regulation
and Standards for an identical risk is 27 ug/1. These calcu-
lations take into consideration the average amount of fish
consumed daily by an individual. The differences in the two
estimates may be attributed to the different mathematical
model used, the assumption made for these calculations, such
as the consumption of fish by an individual and the animal
species used, such as the rat or mouse. The World Health
Organization published a tentative guideline level o:'
ug/1. This was based on the NCI mouse data utilizing a
linear multistage extrapolation model. It is noteworthy
that these risk estimates are made utilizing the total
exposure from drinking water. The risk would be proportionally
increased if the exposure from air and food is taken into
consideration.
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IX-17
Table IX-1. Recommended Concentrations of
TCE in Drinking Water
Organization
Non-Carcinogenic
Endpoint
Carcinogenic
Endpoint
The National Academy
of Sciences (1977)
The National Academy
of Sciences (1980)
U.S. EPA (OWRS)
U.S. EPA (ODW, HA'S)
World Health Organization
105 mg/1 for 1-day
15 mg/1 for 10-day
6.77 mg/1 for lifetime 27 ug/1
2 mg/1 - 1-day -
0.2 mg/1 - 10-day
0.080 mg/1 for Longer-term
30 ug/1
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IX-18
The Academy (1980) also calculated levels of TCE for a short-term
exposure. In these estimations, the carcinogenic potential
of TCE was not taken into consideration. They estimated
concentrations for one-day and seven-day exposures as 105 mg/1
and 15 mg/lf respectively . Their calculations were based
on the rough approximation of a toxic dose in an accidental
exposure case; it was not a controlled experiment where the
subjects were exposed to several dose levels and the no effect
dose level was not established. EPA's Office of Water Regula-
tion and Standards established a level of 6.77 mg/1, estimated
from TLV of 100 ppm and an average daily consumption 6.5 gm
fish by an individual. It is worth mentioning that TLVs
are established for healthy adult workers, mostly males and
are not recommended for the general public where the population
consists of healthy as well as sick subjects of both sexes.
They also calculated an alternate level utilizing Van Duuren's
study, where a single dose of 2.38 mg/kg/day was used. This
study was for a short duration and should not be used for
estimating a lifetime acceptable level.
The Office of Drinking Water issued a Health Advisory (formerly
called SNARL) in 1977. This Health Advisory estimated
negligible risk levels of 1-day, 10-day and longer-term as 2
mg/1, 0.2 mg/1 and 0.080 mg/1, respectively. Since then,
more data have become available, therefore, these levels
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IX-19
should be evaluated and revised, if necessary. It should be
remembered that these health advisories were established for
transient exposures, they do not take cancer risk estimate
into consideration, and do not incorporate the exposure of
humans to TCE from sources such as food and air.
Use of a two year feeding study, in at least two experimental
animals, one of them being a rodent, would be the best means
of calculating an ADI. Since these data are not available,
an attempt has been made and an ADI of 0.514 ing/day has been
calculated from a 3-month inhalation study in rats.
Since, it is assumed that humans consume about two liters of
water per day, the adjusted ADI, would be:
Adjusted ADI = 0.514 mg = 0.257 mg/1
2 1
The carcinogenic potential of TCE was not taken into consideration
in the above calculations for the ADI, however, this aspect
of adverse health effects should not be ignored. There is
limited evidence concerning the carcinogenicity of TCE.
-------
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