WASHINGTON OPERATIONS,
MTR-7142
flir Pollution flssessment of Trichloroethylene
B.B. FULLER
FEBRUARY 1976
JIT
HOT
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MITRE Technical Report
MTR-7142
flir Pollution Assessment of Trichloroethylene
B.B. FULLER
FEBRUARY 1976
CONTRACT SPONSOR Environmental Protection Agency
CONTRACT NO 68-02-1495
PROJECT NO 077B
DEPT W-54
MITRE
• • .r... ..„,..... .. _ This document was prepared for authorized distribution
MCLEAN VIRGINIA 22101 „ na, not been approwed for publie relea$e
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Department Approval:
MITRE Project ApprowafT
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ABSTRACT
Trichloroethylene is an organic solvent primarily used for the
vapor degreasing of metals. Approximately 200,000 industrial workers
are exposed to this solvent annually. Although the major physiological
response in humans from acute or chronic exposure to trichloroethylene
is central nervous system depression, damage to liver, kidney and heart
have also been reported. Since the metabolic fate and toxic effects of
trichloroethylene are similar in many mammalian species to those in
man, the fact that this compound has recently been implicated as a
potent liver carcinogen in mice may be of significance.
Approximately 60% of the total world production of trichloroethylene
is released to the environment each year. However, due to its low water
solubility, high vapor pressure and high atmospheric photodegradation
rate, trichloroethylene is not expected to persist in the environment.
Ambient concentrations in the atmosphere of industrialized areas are
only about 16 ppt. Proper use of local exhaust systems in conjunction
with vapor condensation apparatus and good general ventilation should
be sufficient to maintain levels of trichloroethylene in the workshop
environment well below the recommended 100 ppm and to insure a minimum
release to the ambient atmosphere.
iii
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ACKNOWLEDGEMENTS
I gratefully acknowledge the assistance of E. Preston in
calculating the atmospheric diffusion of trichloroethylene downwind
from production facilities. In addition, I wish' to thank my
colleagues, L. Thomas, R. Ouellette, J. Golden, and B. Baratz, for
their many helpful suggestions and criticisms, and M. Jones,
J. Manning, and R. Johnson of the U.S. Environmental Protection
Agency for their support and assistance during the one month duration
of this project.
iv
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TABLE.OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
I. SUMMARY AND CONCLUSIONS 1
II. AIR POLLUTION ASSESSMENT REPORT 6
A. PHYSICAL AND CHEMICAL PROPERTIES 6
B. EFFECTS 11
1. Humans 11
2. Animals 21
3. Other Effects 31
4. Present, On-going Research 32
C. AMBIENT CONCENTRATIONS, POPULATION AT RISK AND
MEASUREMENT TECHNOLOGY 34
D. SOURCES 44
E. CONTROL 53
1. Substitution of Less Harmful Solvents 53
2. Proper Design of Condensation Apparatus 53
3. Process Ventilation Process Location 53
4. Proper Effluent Treatment 55
5. Proper Handling, Maintenance and Disposal
Procedures 55
REFERENCES 57
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LIST OF FIGURES
Figure Number
1 Trichloroethylene Production Capacity
2 Summary of Product Release Information
Page
46
52
Table Number
I
II
III
IV
V
VI
VII
VIII
IX
LIST OF TABLES
Page
Physical Properties 7
Occurrence of Trichloroethylene in Human Tissue 13
Percent of Workers Exhibiting Each Symptom at
the Given Exposure Level 17
Toxicological Effects 27
Occurrence of Trichloroethylene in :he Typical
Concentrations (W/W) 35
Trichloroethylene Exposures in Swedish
Engineering Workshops 40
Trichloroethylene Production (in 1970) 45
Trichloroethylene in Foodstuffs 49
Industrial or End Use Trichloroethylene 51
vi
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AIR POLLUTION ASSESSMENT OF TRICHLOROETHYLENE
I. SUMMARY AND CONCLUSIONS
Trichloroethylene is a noncorrosive, nonflammable liquid with
excellent solvent properties. The compound is easily oxidized to
products which are both acidic and corrosive. Oxidation inhibitors
are available which are effective at concentrations of less than one
percent.
Over 90 percent of all the trichloroethylene produced is used by
industrial metal fabricating plants for vapor degreasing. The remain-
der is utilized as an extractive solvent in foods and medicines and
as a dry cleaning solvent. Trichloroethylene was also the solvent used
to extract caffein from coffee, and was present to the extent of 10 to
25 ?pn. General Foods, Inc., the largest manufacturer of decaffeinat-
ed coffee, has recently replaced trichloroethylene with methylene
chloride.
The major physiological response in humans from acute or chronic
exposure to trichoroethylene is central nervous system depression.
This response may take the form of visual disturbances, mental con-
fusion, fatigue, nausea and vomiting, dizziness, palpitation, and
other symptoms. These effects have actually been observed in indus-
trial workers exposed to trichloroethylene vapors as well as in ex-
perimental subjects. Evidence indicates that adverse effects are
noticeable in humans even at the allowable level of 100 ppm. Mild
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effects have even been reported at concentrations as low as 5 to
10 ppm. One-hundred-and-four workers were exposed to this chemical
for over 3 years at levels of about 100 ppm. Ninety-two percent of
these workers exhibited some of the symptoms described above. How-
ever, cessation of exposure reversed the effects. Symptoms subsided
in most of the workers within five months. Data relating to this type
of effect are, in general, quite conclusive. Additional effects such
as, damage to liver, kidney, and heart have also been reported. These
data, in many cases, are clouded by the fact that the subjects were
also heavy consumers of alcohol. This factor may have contributed to
or aggravated the observed condition. Therefore, evidence for this
type of damage is inconclusive. Blindness, loss of hearing and
tactile sense, and death from cardiac arrest ind ventricular fibril-
lation following acute exposure have also been reported.
The major products of trichloroethylene metabolism are tri-
chloroethanol and trichloroacetic acid. Trichloroethanol is much more
toxic to the heart and nervous system than trichloroethylene. Thus,
it is believed that this metabolite is responsible for many of the
observed toxic effects. High levels of trichloroethanol are excreted
by persons exposed to as little as 70 ppm of trichloroethylene.
Metabolic fate and toxic effects of trichloroethylene in many
c
mammalian species are similar to those in man. Moderate or re-
versible liver damage was reported in mice, guinea pigs, and dogs
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following inhalation of concentrations 10 to 16 times the acceptable
industrial level (100 ppm). Inhalation at levels of 2 to 20 ppm led
to inhibition of antibody formation and of neutrophil activity.
Cats exposed to 20 ppm for 60 to 90 minutes for A to 6 months showed
damage to liver, kidneys, spleen, and lymph nodes. Concentrations
of 7000 to 14000 ppm (70 to 140 times that of industrial exposure)
produce changes in the electroencephalogram in rabbits, in some cases
resembling epileptic seizures. The applicability of these experi-
mental results to humans is uncertain. Mice are especially sensi-
tive to hepatotoxic agents and rabbits, to convulsions.
Trichloroethylene has recently been implicated as a potent
liver carcinogen in mice. It was administered by gastric intubation
at massive dose levels (900 to 2400 mg/kg), and a maximun of 43.2
percent of the test animals were affected. This claim for carcino-
genicity is not entirely conclusive. Effects produced in highly
susceptible animals (2.5 percent of the controls spontaneously
developed liver cancer) could not be repeated in rats. In any event,
dosage levels are equivalent to a human drinking 50 million cups
of decaffeinated coffee each day for a lifetime.
Inhalation studies conducted at the laboratories of Dow Chemical
Corporation showed that trichloroethylene was not teratogenic in mice
or rats at 300 ppm. No mutagenesis studies have been reported.
Trichloroethylene is not expected to accumulate in the environ-
ment because it is slightly soluble in water, possesses a high vapor
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pressure, and has a high atmospheric photodegradation rate (a half-
life of 0.3 days at sea level). Therefore, it is not felt to represent
an air pollution hazard. Ambient concentrations in the atmosphere of
industrialized areas are about 16 parts per trillion; in rural areas,
they are less than 5 parts per trillion; ambient concentrations in
water are about 0.6 nanograms/liter (0.1 ppt)
Ground-level concentration of trichloroethylene in the atmo-
sphere 500 meters downwind of a production plant is estimated to be
o
approximately 570 g/m , or 0.106 ppm. Assuming that symptoms occur
following chronic industrial exposure to 5 ppm and that the average
industrial worker is exposed for 2,000 hours per year, an individual
must remain at this point 24 hours a day for 11.A years in order to
inhale a similar amount. He must remain there for 228 years in order
to inhale an amount equivalent to that inhaled by an industrial worker
following a 1-year exposure to 100 ppm.
The most significant population exposed to trichloroethylene is
industrial workers involved in vapor degreasing or dry cleaning oper-
ations. About 200,000 such workers are exposed each year. In 1973,
OSHA recommended an ambient level of 100 ppm as the allowable time-
weighted average concentration over an 8-hour workday, with a 300
ppm excursion limit. Evidence suggests that excursions considerably
above this level may exist. The general public is exposed to tri-
chloroethylene through inhalation of cleaning fluids and ingestion of
foods, spices, and medicines. Ingestion exposure is a result of
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consuming products whose commercial preparation required an ex-
traction operation with this solvent. Residue concentrations ranging
from 0.02 to 22 yg/kg have been detected in foodstuffs and concentra-
tions of up to 32 yg/kg have been detected in human tissue. Tri-
chloroethylene is rapidly absorbed by the lungs following inhalation,
but only slightly eliminated upon exhalation.
Current measurement technology is adequate to ensure that workers
are not exposed to hazardous levels. Adsorption onto activated
charcoal represents the easiest and most efficient method of collec-
tion, and gas chromatography is the most specific and sensitive method
for analysis. Breath analysis of exposed workers is also feasible.
Trichloroethylene is a synthetic chemical manufactured both
domestically and abroad. Estimated world annual production in 1973
was approximately one million tons and domestic production in 1974
amounted to about 215,000 tons. There are five producers of tri-
chloroethylene in the United States and their production plants are
all located in southern Texas and Louisiana.
About 600,000 tons of trichloroethylene are released to the
atmosphere and 10,000 tons to the ocean each year. This total re-
lease represents approximately 60 percent of total world production.
A proper local exhaust system, vapor condensation apparatus, and
general ventilation system should keep levels below 100 ppm. Care
must be taken to clean up spills, check leaks, and repair faulty
equipment.
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II. AIR POLLUTION ASSESSMENT REPORT
A. PHYSICAL AND CHEMICAL PROPERTIES
Trtchloroethylene, CHC1 = CC12, is at normal temperatures a
clear, colorless, noncorrosive, nonflammable liquid, possessing the
characteristically sweet odor associated with chlorinated hydro-
carbons. Physical properties are listed in Table I (1, 2, 3).
Trichloroethylene is unstable in the presence of oxygen. Degra-
dation is further promoted by elevated temperatures and exposure to
light (especially ultraviolet irradiation). It is quite reactive
to OH, but only very slowly oxidized by alkyl peroxy radicals and
ozone (A). Over 80 percent of the initial oxidation products (as
indicated below).consist of compound (A), which decomposes to yield
dichloroacetyl chloride, C12CHCOC1 (2).
C12C C12C 0
0=0
HC HC 0
I I
Cl Ci
(A) CB)
Compound (B), another initial oxidation product, yields phosgene,
carbon monoxide, and hydrogen chloride upon further decomposition. In
the presence of anhydrous aluminum chloride, compound (A) rearranges
to yield equal amounts of chloroacetyl chloride and chloral, CC1-CHO.
Compounds (A) and (8) are violently explosive and their sudden decom-
position is promoted by the addition of Impurities, including oxidation
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TABLE I
PHYSICAL PROPERTIES
Molecular formula: C1CH = CC1_
Physical state: colorless liquid
Molecular weight: 131.4
Melting point, °C: -87.1
Boiling point
760mmHg, °C: 86.7
Specific gravity
20°/4°C:
25°/4°C:
100°/4°C:
Vapor density,
bp, 1 atm
g/1 (air = 1):
Vapor pressure:
Viscosity,
liquid:
1):
°C
-20
-10.8
0
10
20
°C
-80
-70
-60
-30
-20
1.464
1.456
1.325
4.54
mmHg
5.4
10.8
20.1
35.2
57.8
CP*
2.95
2.10
1.68
1.02
0.9
°C
30
40
50
60
86.7
°C
0
20
40
60
mmHg
94
146.8
212
305.7
760
CP*
0.7
0.58
0.48
0.42
*centipoise
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TABLE I (CONCLUDED)
Solubility of trichloroethylene in water,
g/lOOg H0
25°C:
60°C:
0.11
0.125
Solubility of water in trichloroethylene
g/100 g trichloroethylene
0°C:
25°C:
60°C:
0.01
0.033
0.080
Percent in "saturated" air (25°C): 10.2
Density of "Saturated" air (air = 1): 1.35
Ignition temperature, °C:
Flash point:
Refractive index (20°C) :
Dielectric constant (liquid) 16°C:
Odor threshold (ppm)
463
none by
standard
methods
1.478
3.42
21.4
Conversions:
1 ppm - 5.38 mg/m @25°C
1 mg/liter = 186.1 ppm
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inhibitors. In the presence of moisture, dichloroacetyl chloride is
decomposed to dichloroacetic and hydrochloric acids. The acidic
products of oxidation are highly corrosive. They react with most
metals with which the liquid may contact.
A large variety of pure compounds and mixtures are effective
oxidation inhibitors of trichloroethylene. Normally, these stabi-
lizers are effective at less than one percent by weight. Some current
stabilizers in use include: acetone, acetylenic compounds, aniline,
borate esters, n-butane, 0-cresol, diisopropylamine, ethyl acetate,
hydrazine derivatives, isobutyl alcohol, lactones, 0-nitrophenol,
pyrazoles, stearates, and SO.. With inhibitor addition, trichloro-
ethylene is stable (to 130°C) in the presence of air, moisture,
light, and common construction metals. Above 130°C, inhibitors are
ineffective and corrosion of the metals occurs. When heated above
700°C, the vapor decomposes, yielding a mixture of dichloroethylene,
perchloroethylene, carbon tetrachloride, chloroform, and methyl chlo-
ride. When heated vigorously in the presence of air, trichloro-
ethylene vapor is completely oxidized to carbon dioxide and hydrogen
chloride. Reaction with ozone yields an explosive ozonide which de-
composes to hydrogen chloride, phosgene, carbon monoxide, and chlorine
peroxide (2).
Trichloroethylene is not readily hydrolyzed by water. Under
pressure at 150°C, it reacts with alkaline hydrazides to yield gly-
colic acid, CH2OHCOOH. Reaction with 90 percent sulfuric acid yields
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monochloroacetic acid. Strong alkalis dehydrochlorinate trichloro-
ethylene, with the production of explosive and flammable chloro-
acetylene (2).
10
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B. EFFECTS
1. Humans. Trichloroethylene is rapidly absorbed by the lungs
upon inhalation. However, only slight amounts are eliminated upon
subsequent exhalation. An early indication of the metabolic fate of
absorbed trichloroethylene was revealed in a study by Barrett and
Johnston C5). In this effort, the steam distillate of urine from
human subjects exposed to trichloroethylene was found to contain a
metabolite with three chlorines on a single carbon atom. Further in-
vestigation in dogs led to the conclusion that this metabolite was
trichloroacetic acid. This conclusion was confirmed by Powell in
1942 (6). A somewhat later study by Butler using dogs (7) revealed
that the major, product of trichloroethylene metabolism was trichloro-
ethanol, either free or conjugated with glucuronic acid. Butler con-
cluded that the metabolism of trichloroethylene involves an initial
conversion to chloral hydrate with rapid metabolic conversion to
either trichloroethanol or trichloroacetic acid.
In I960, a detailed quantitative study was performed by Soucek
and Vlachova (8). They showed that an average of 64 percent (range,
58 to 70 percent) of inhaled trichloroethylene vapor was retained by
persons exposed to concentrations of up to 150 ppm.* Within a few
minutes of exposure, monochloroacetic acid (a minor metabolite), tri-
chloroacetic acid, and trichloroethanol were accumulating in the
^Duration of exposure was not reported.
11
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urine. The excretion of monochloroacetic acid was maximal at the end
of exposure and continued for as long as 168 hours after exposure.
Monochloroacetic acid constituted about four percent of the retained
trichloroethylene. The excretion of trichloroacetic acid was maximal
24 to 28 hours following exposure and continued for as long as 520
hours. Trichloroacetic acid constituted from 10 to 30 percent of the
retained trichloroethylene. Finally, excretion of trichloroethanol
was maximal a few hours following exposure and continued for as long
as 216 hours. Trichloroethanol constituted from 32 to 59 percent of
the retained trichloroethy]ene. The total amount of metabolites ex-
creted amounted to 43 to 100 percent of the absorbed trichloroethylene
and were in the ratio monochloroacetic acid: trichloroacetic acid:
trichloroethanol:: 1:5:12. Later studies by Bart^.iicek (9) and Ogata
et al. CIO) generally confirmed the results outlined above. Analyses
of postmortem human tissue revealed the presence of trichloroethylene
in body fat, kidney, liver, and brain, indicating uptake by these tis-
sues. Concentrations in eight subjects are presented in Table II.
In 1972, Ikeda et^ a^. (11) indicated that the high percentage of
trichloroethanol excreted by persons exposed to quantities of tri-
chloroethylene in excess of 70 ppm might have serious toxicological
11
consequences since trichloroethanol is much more neurotoxic* and
cardiotoxic** than trichloroethylene itself. These results suggest
*Poisonous or destructive to nerve tissue.
**Having a poisonous or deleterious effect vpon the heart.
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TABLE II
OCCURRENCE OF TRICHLOROETHYLENE IN HUMAN TISSUE.
CONCENTRATIONS IN wg/kg (WET TISSUE)
AGE OF
SUBJECT
76
76
SEX
F
F
F
M
M
M
M
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
TRICHLORO
ETHYLENE
32
< 1
5
1
2
3
2
< 1
1.4
3.2
6.4
3.5
3.4
5.2
14.1
5.8
4.6
4.9
82
48
65
75
66
74
Source: McConnell, G., Ferguson, D.M., and Pearson, D.R. "Chlorinated
Hydrocarbons and the Environment" Endeavor 34 13-18 (1975).
13
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that the standards proposed by the Occupational Safety and Health
Administration (100 ppm allowable time-weighted average concentration
over an 8-hour workday with a 300 ppm limit) may not be adequate.
Many studies of the effects of chronic occupational exposure to
trichloroethylene have been reported. In general, a wide spectrum of
complaints were observed. A study involving 70 young workers (83
percent less than 30 years old) exposed up to 6 years to variable
concentrations of trichloroethylene reported the following symptoms
(12): headache (74 percent), dizziness (31 percent), nausea (43
percent), sleepiness at end of shift (29 percent), fatigue (68 per-
cent), euphoria (31 percent), palpitations (29 percent), disturbances
of vision (21 percent), irritability (56 percent), disturbed sleep
(46 percent), anxiety (27 percent), loss of appetite (50 percent),
excessive sweating (39 percent), and alcohol intolerance (21 percent).
The following additional symptoms were reported in studies by
Andersson (13) and Bardodej and Vyskocil (14): vertigo, tremors,
vomiting, a feeling and appearance of light-headedness or "drunken-
ness," and slowing of the heartbeat (bradycardia). Andersson reported
that only 8 of 104 workers who had been exposed to this chemical for
more than 3 years were without symptoms. However, cessation of
exposure reversed the effects and follow-up studies three to seven
years later showed little residual evidence of trichloroethylene
*A hallucination of movement, a sensation as if the external world
were revolving around the subject or as if he-himself were revolv-
ing in space.
14
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intoxication. Some workers reported that symptoms had subsided with-
in five months after termination of exposure. Effects on skin in-
cluded reddening and dermographism,* skin burns on contact, general-
ized dermatitis resulting from contact with vapor, and possibly
scleroderma** (15, 16, 17). Stewart and Dodd CIS) demonstrated that
unless trichloroethylene is trapped against the skin, absorption by
this route is insignificant.
In one study (.19), an attempt was made to correlate levels of
trichloroacetic acid excreted in the urine of 122 exposed workers
with the results of an independent medical survey. The correlations
were as follows: less than 20 mg trichloroacetic acid per liter of
urine, no symptoms; 40 to 75 mg, 50 percent reported abnormal fa-
tigue, increased need for sleep, diffuse gastric symptoms, irrita-
bility, headache, and intolerance of alcohol; 100 mg to 200 mg, most
workers reported some of the above symptoms; greater than 200 mg,
most workers reported symptoms plus an increased absence from work
because of illness; greater than 300 mg, all of the workers exper-
ienced all of the above symptoms. Andersson (13), in a detailed
study of 104 exposed workers confirmed this report, indicating that
no symptoms appeared when excretion of trichloroacetic acid was less
*A condition in which scratching the skin with a dull instrument
provokes a linear, raised, pale streak.
**A systemic disease which may involve the connective tissues of any
part of the body, including the skin, heart, esophagus, kidney and
lung. The skin may be thickened, hard and rigid and pigmented
patches may occur.
15
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than 20 rag/liter of urine, but that most workers reported symptoms
when excretion was greater than 75 mg/liter.
Frant and Westendorp C20) calculated that a person subjected to
a sustained exposure of 100 ppm for several days will excrete about
200 mg of trichloroacetic acid/liter of urine. Fribert el^ al. (21)
•\
confirmed this estimate by exposing 3 persons for 7 hours daily for
one week to 100 to 150 ppm and noting concentrations of 250 to 300 mg
trichloroacetic acid/liter of urine during the latter days of the
study. Thus, some idea of the levels to which the above workers were
exposed is possible.
In another study (14), Bardodej and Vyskocil examined 75 workers
exposed to trichloroethylene in dry cleaning and degreasing operations
for periods of from less than one year to ten or niore years. In
general, symptoms increased with length of exposure. These investi-
gators also attempted to correlate symptoms with levels of exposure.
The results are summarized in Table III. Cases of chronic over-
exposure resulting in total blindness (22, 23) and in total loss of
tactile* sense and inability to grasp objects between thumb and fore-
finger (16) have been reported. Physiologic changes observed follow-
ing chronic exposure include Increased levels of leukocyte alkaline
phosphatase and blood acid phosphatase (24). It is suggested that
these findings might indicate an increased capacity to metabolize
*Pertaining to the touch.
16
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TABLE III
PERCENT OF WORKERS EXHIBITING EACH
SYMPTOM AT THE GIVEN EXPOSURE LEVEL
Headache
Intolerance
to alcohol
Disturbance
of sleep
Fatigue
Bradycardia
Elec trocard iogram
Disturbance
30-630 ppm
70
92
83
92
33
16
100-154 ppm
26
63
26
47
40
21
5-10 ppm
67
22
22
61
16
6
Source: Bardodej, Z., and Vyskocil, J. "The problem of trichloro-
ethylene in occupational medicine" Arch. Ind. Health 13,
581-592, 1956.
17
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alcohols; represent a response to changes in blood pH; or might be
related to glycogen metabolism in the liver. Exposure to trichloro-
ethylene may either speed or slow the heart rate. Andersson (13)
reported abnormal electrocardiograms with disturbance of cardiac
rhythm in 77 out of 104 exposed workers studied.
To what extent trichloroethylene damages the liver is not clear.
Albahary e£ al. (25) and Talot et^ al. (26) conducted liver function
tests on exposed workers and reported no evidence of liver disorders.
Milby C27) noted normal liver and kidney function in a severely over-
exposed worker who was excreting 780 mg trichloroacetic acid per liter
of urine. On the other hand, Guyotjeannin and Van Steenkiste (28)
reported abnormalities of cephalin flocculation,* total lipids', and
unsaturated fatty acids and an increase in beta and gamma globulins
in 18 regularly exposed workers.
Laboratory studies on human volunteers have been conducted in
order to elucidate the effect of exposure to trichloroethylene on
performance in various psychophysiological tests. Vernon and Fergu-
son (29) subjected 8 male volunteers to two-hour exposures of 0,
100, 300, and 1000 ppra of trichloroethylene. Decrements in per-
formance were significant only at 1000 ppm. In a later study, Stewart
*Cephalin flocculation test (Hanger's test) is a test for the pres-
ence of liver cell disease, based on the flocculation of a cephalin-
cholesterol emulsion by the patient's serum. Cephalin is a crude
phospholipid which is used as a clotting agent in blood coagula-
tion work.
18
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et al. (30) exposed 5 subjects to 200 ppm for 7 hours on 5 consecutive
days and reported normal performance on tests. On the other hand,
Salvini et al. (31) exposed 6 male volunteers to an average concentration
of trichloroethylene of 110 ppm (range 90 to 130 ppm) in two 4-hour
sessions separated by 1.5 hours. He reported a significant decrement in
performance on tests of memory, perception, and manual dexterity and
concluded that 100 ppm was very close to the average concentration capable
of interfering with psychophysiological efficiency. These studies would
appear to support those of Ikeda et al. (11), again suggesting that present
occupational exposure levels may be unhealthy.
Cases of acute exposure with extremely serious and often fatal
consequences have been reported. Toxic action primarily involves
the central nervous system, with specific paralysis of the trigeminal
nerve,* but the gastrointestinal system, circulatory system, and occa-
sionally the kidneys are affected as well.
The first report of deaths resulting from acute overexposure in
the United States was presented by Kleinfeld and Tabershaw (32). In
one case, the victim died of apparent hepatorenal** failure after
accidentally drinking trichloroethylene. The man had, however, been
a heavy drinker, which might have been a contributing factor. Secchi
*The fifth cranial nerve.
**Pertaining to the liver and kidneys.
19
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et al. C33) reported that no liver damage was observed when pure tri-
chloroethylene was ingested. Four other victims were all employed at
degreasing operations where concentrations of trichloroethlene ap-
proached 8000 ppm. All four complained of nausea, drowsiness, dizzi-
ness, and vomiting and died suddenly within a few hours after leaving
work. The cause of death was ventricular fibrillation.*
In 1963, James (30) reported the case of a man employed as a
vapor degreaser who had become addicted to trichloroethylene. He
exhibited all of the usual symptoms associated with chronic exposure
but also lost his sense of smell. He died suddenly of cardiac arrest
17 hours after his last known exposure. Autopsy also revealed fatty
degeneration of the liver.
Other cases of sudden death occurring within a short time after
acute exposure to trichloroethylene have been reported (31-33). In
one case, death was preceded by the usual symptoms and also paralysis
of the face and neck muscles. In another case', the cause of death
was ventricular fibrillation and, in the third case, massive liver
necrosis** was observed. Lilis et al. (12) offered a theory that
changes in epinephrine secretion associated with hypersympathico-
tonia*** induced by trichloroethylene exposure, particularly when
*A condition characterized by twitching of the ventricular muscle,
the impulses traversing the ventricles so rapidly that coordinated
contractions cannot occur.
**Death of tissue, usually as individual cells, groups of cells, or in
small localized areas.
***An increased tone of the sympathetic nervous system.
20
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accompanied by physical exertion or stress, might account for the
cases of unexplained or sudden death.
Other effects resulting from acute exposure to trichloro-
ethylene include loss of taste and trigeminal paralysis (38), com-
plete loss of hearing for tones over 1000 cycles per second (39),
and temporary paranoid psychosis with distortion of both vertical
and horizontal vision (40).
No evidence for carcinogenicity of trichloroethylene in humans
has been reported to date.
2. Animals. The metabolic fate of trichloroethylene is
qualitatively the same in many mammalian species as it is in man.
However, in some cases, there are quantitative differences. Rabbits,
for instance, were shown to excrete 10 times more trichloroethanol
than trichloroacetic acid and about 50 tiroes less trichloroacetic
acid than man (41). Rats, just as humans, excreted increasing amounts
of trichloroacetic acid, with maximum excretion at 24 hours after
exposure to 640 ppm, 1150 ppm, or 2500 ppm for 4 hours. They continued
to excrete trichloroacetic acid for up to 144 hours (21).
Fabre and Truhaut (42) studied tissue homogenates from animals
following exposure to trichloroethylene. They found trichloro-
ethylene present in all of the tissues examined. Trichloroacetic acid
was present in greatest concentrations in spleen, suprarenal glands,
reproductive organs, and urine. In vitro metabolic studies concluded
that the most active conversion of trichloroethylene to its metabo-
21
-------
lites occurred in the spleen, followed by lung, brain, liver, and
kidney.
Toxic effects following inhalation have been observed in a
variety of species under both chronic (low concentration for long
period of exposure) and acute (high concentration for short period
of exposure) conditions. The highest levels of exposure with no
observable effects on rats were: 0.3 hours at 20,000 ppm; 0.6 hours
at 12,000 ppm; 1.4 hours at 4800 ppm; and 5 hours at 3000 ppm. The
"no effect" levels for chronic exposure (7 hours a day, 5 days a week)
were: 400 ppm, monkeys;200 ppm, rats and rabbits; and 100 ppm, guinea
pigs (43). Prendergast et_ a^. (44) demonstrated no effects levels in
rats, guinea pigs, rabbits, dogs, and monkeys to be 730 ppm, 8 hours
daily, 5 days per week, for 6 weeks and 36 ppm, °4 hours a day, for
90 days.
The wide range of adverse effects arising from chronic exposure
to trichloroethylene can be seen from the study of Cagianelli et al.
(45). In this effort, male rats were sprayed twice a day with this
substance for 40 days. By the 40th day, some damage to the liver and
heart and more serious damage to the kidneys was noted. Transaminase
and Y globulin levels were increased and serum albumin levels were
decreased. The experimental animals showed a marked decrease in
weight and a reduction in mature red cells, reticulocytes,* leuko-
*A young red blood cell.
22
-------
cytes,* and platelets** in the peripheral blood. Bone marrow activi-
ty was greatly depressed. Rats injected with 0.004 moles trichloro-
ethylene per kilogram showed evidence of functional hepatic changes
and microscopic evidence of liver damage 12 to 16 hours following ex-
posure. These effects were apparently reversible and disappeared
after 24 hours (46). Moderate liver damage was reported in guinea
pigs exposed for over 1100 hours to levels of 1200 ppm trichloro-
ethylene (47); in dogs exposed to 750 ppm repeatedly for 3 weeks
(48); and in mice exposed to 1600 ppm, 4 hours a day, 6 times per
week.
Cats exposed to 20 ppm trichloroethylene for 60 to 90 minutes
for 4 to 6 months showed damage to liver, kidneys, spleen, and lymph-
atic ganglions*** (50) , lending additional support to the Ikeda
hypothesis (11).
Rats and rabbits exposed to trichloroethylene for 40 to 50 min-
utes, 5 to 6 times per week, showed levels of glutamic-oxalacetic
transaminase and glutamic-pyruvic transaminase increased above normal
by 58 percent and 27 percent, respectively (51). An intramuscular
injection of a total of 8.75 to 9 mg/kg trichloroethylene in rabbits
resulted in a 26 percent decrease in the level of ATP**** in the retina.
*White blood cells.
**A circular or oval disk found in the blood of all mammals which is
concerned in coagulation of the blood and contraction of the clot.
***Lymph nodes.
****Adenosine triphosphate.
23
-------
Levels of aldolase, glucose-6-phosphate dehydrogenase, lactic dehy-
drogenase, and hexokinase were also decreased, whereas malate dehydro-
genase and NAD* -sorbitol dehydrogenase were elevated. Most of the
changes in enzyme activity were reversible; however, aldolase and
glucose-6-phosphate dehydrogenase activity as well as ATP concentra-
tion failed to return to normal levels by two weeks following ex-
posure (52).
Effects on the immune system were reported in rabbits exposed
to 10 mg/rn3, 4 hours daily, for 9 weeks. These effects consisted of
inhibition of antibody formation and of the activity of neutrophils**
(53). Exposure of rabbits to 100 mg/m3, 3 hours daily, for 8 to 10
months, resulted in a decreased total antibody titer following typhoid
immunization.
Bradycardia was induced in guinea pigs by intraperitoneal in-
jection of either trichloroethylene or its metabolite, trichloro-
ethanol. The latter proved twice as effective in slowing the heart
and the authors suggested that metabolic conversion to trichloro-
ethanol was responsible for many of the observed toxic effects of tri-
chloroethylene (55) .
Effects on the brain and behavioral abnormalities have also been
reported. Acute exposure of rabbits to 7000 ppm to 14,000 ppm for 15
*Nicotinamide-adenine-dinucleotide.
**A white blood cell stainable by neutral dyes.
-------
to 60 minutes produced changes In the electroencephalogram ranging
from minor up to electroclinical epileptic seizures (56). Further
studies on rabbits that were chronically intoxicated with alcohol
revealed that subsequent exposure to trichloroethylene induced graver
functional disturbances of longer duration even though the dose of
trichloroethylene was half the strength used previously (57). These
studies constitute evidence for the suggestion that alcohol may ag-
gravate the effects of trichloroethylene intoxication. Rats exposed
to 400 ppm for 8 hours, 5 times per week, exhibited decreased perfor-
mance in swimming tests and increased exploratory behavior (58).
Exposure to 800 ppm and 1600 ppm produced further decrements in per-
formance with the animals exhibiting 65 percent and 58 percent of
their normal activity, respectively (.59).
The lethal concentration via inhalation for rats exposed for
A hours was 8000 ppm (60). The lethal concentration in rabbits ex-
posed for 50 minutes was 11,000 ppm (61). The concentration lethal
to 50 percent of flatfish exposed for 96 hours (96 hours LCcQ) was
16 mg/1 (2).
Trichloroethylene has recently been implicated as a potent liver
carcinogen* in mice by the National Cancer Institute. Striking dif-
ferences were observed between the incidence of hepatocellular
*A cancer-producing substance.
25
-------
carcinomas* in mice given trichloroethylene and in controls. Male
mice were given either 2400 mg/kg or 1200 mg/kg doses, while females
received 1800 mg/kg or 900 mg/kg. Doses were given by gastric intu-
bation. Of the mice given the lower doses, 30.6 percent developed
liver cancer. Of those receiving the higher doses, 43.2 percent were
affected. The incidence of spontaneous liver cancer in the control
group was 2.5 percent (63) . Rats given a 500 mg/kg or 1000 mg/kg
dose failed to develop cancer, but it was suggested that the extreme-
ly high dose was very toxic to the animals and might have clouded the
study. Inhalation studies conducted at Dow laboratories, showed that
trichloroethylene was not teratogenic** in mice or rats at 300 ppm
(64). No mutagenesis studies have been reported. Toxicologic effects
in all species, including man, are presented in Table IV.
Of all the effects reported in both animals and man, only those
relating to central nervous system depression seem entirely conclu-
sive. These effects, all of which are summarized in Table II, appar-
ently occur at concentrations to which certain industrial workers may
realistically be exposed and have, in fact, been shown to occur in
such workers. Evidence on damage to the liver is not conclusive.
"Moderate" or "reversible" damage has been demonstrated in animals at
relatively high concentrations (10 to 16 times the typical industrial
concentrations). The extent to which trichloroethylene damages the
*A malignant new growth made up of epithelial cells tending to
infiltrate the surrounding tissues and spread.
**The production of physical defects in offspring in_ utero.
26
-------
TABLE IV
TOXICOLOGICAL EFFECTS
ANIMAL ROUTE DOSE
Rat Spray
Injection 530 ppm
Inhalation 400 ppm
800 ppm
1600 ppm
Mouse Gastric 900 -
intubation 2400 ppm
Inhalation. 1600 ppm
Guinea pig Inhalation 1200 ppm
Injection varied
Dog Inhalation 750 ppm
LENGTH OF EXPOSURE EFFECTS
2 times/day; 40 days damage to liver,
heart, kidneys
loss of weight
pancytopenia
bone marrow de-
pression
changes in enzyme
activities
16 hours reversible liver
damage
progressive loss
8 hours; 5 times/week of activity
liver cancer
4 hours/day liver damage
6 days/week
1100 hours liver damage
bradycardia
3 weeks liver damage
REF.
45
46
59
63
49
47
55
48
•o
VI
-------
TABLE IV (CONTINUED)
ANIMAL
ROUTE
DOSE
LENGTH OF EXPOSURE
EFFECTS
REF.
Cat
Rabbit
to
oo
Inhalation
Lnhalation
Injection
20 ppm
Varied
9 ppm
Inhalation 10 ppm
Inhalation 100 ppm
Inhalation 7000 -
14,000 ppm
60-90 minutes
4-6 months
40-50 minutes
5-6 tinier/week
4 hours/d.iy
9 weeks
3 hours/day
8-10 months
15-60 minutes
damage to liver, 50
spleen, kidneys
and lymphatic
ganglions
increased trans- 51
aminase levels
decreased ATP level 52
changes in enzyme
activity
inhibition of anti- 53
body formation
and neutrophil
activity
decreased total
antibody titre
54
minor to major 56
changes in elec- 57
troencephalogram
which are aggreva-
ted by alcohol
-------
TABLE IV (CONTINUED)
ANIMAL
ROUTE
DOSE
LENGTH OF EXPOSURE
EFFECTS
REF.
Human
ro
Inhalation 1000 ppra
Inhalation
Oral
Inhalation
Cnhalatlon
up to 8000
ppm
varied
Inhalation varied
Inhalation varied
Inhalation varied
Inhalation varied
2 hours
90-130 ppm two 4-hour sessions
separated by 1.5
hours
chronic
chronic
acute
acute
acute
acute
decreased perfor- 29
mance in psycho-
physiological
tests
decreased perfor- 31
mance on tests
of memory, per-
ception and
manual dexterity
death from hepa- 31
torenal failure
death from ventrlc- 32
ular fibrillation
lost sense of smell, 34
death from cardiac
arrest; fatty de-
generation of liver
paralysis of face, 35
neck muscles; death
loss of taste; trige- 38
minal nerve paralysis
complete loss of hear- 39
ing for tones over
1000 cps
temporary paranoid 40
psychosis; distortion
of horizontal, vertical
vision
-------
TABLE IV (CONCLUDED)
ANIMAL
ROUTE
DOSE
LENGTH OF EXPOSURE
EFFECTS
Human
Inhalation
u
o
Inhalation
varied
( >20 ppm)
varied
3-6 years
chronic
headache, dizziness,
nausea, sleepiness,
fatigue, euphoria,
palpitation, dis-
turbance of vision,
irritability, dis-
turbed sleep, anxiety,
loss of appetite,
excessive sweating,
alcohol intolerance,
vertigo, tremors,
vomiting, bradycardia,
other electroencepho-
lograph disturbances
total blindness
12
13
14
19
22
23
Inhalation
Inhalation
Inhalation
varied
varied
varied
chronic
chronic
chronic
total loss of tactiJe 16
sense
increased levels of 24
leucocyte alkaline
ohosphatase and blood
acid phosphatase
abnormalities of cephalin 28
flocculation, total
lipids and unsaturated
fatty acids, increase
in beta and gamma glo-
bulins
*An abnormal or exaggerated sense of well-being.
-------
human liver is difficult to ascertain since many of the subjects
were heavy users of alcohol and this fact tended to cloud the
studies Csee, for example, 32).
The claim for carcinogenisis also is inconclusive. Studies were
done using massive doses in highly susceptible animals (mice with a
2.5 percent incidence of liver cancer in the controls). In less
susceptible animals (rats), no effects were observed. In any event,
the dose used would be equivalent to a human drinking 50 million cups
of decaffeinated coffee each day for a lifetime.
3. Other Effects. Exposure to 0.6 percent trichloroethylene
was shown to decrease the output of light emitted by the luminous
bacteria Photobacterium phosphoreum (65). A general bacteriostatic
effect on alpha hemolytic streptococci, gram-positive and gram-
negative diplococci, Corynebacterium and Brucella melitensis, was
noted in the human oropharyngeal* cavity following exposure to tri-
chloroethylene during anaesthesia (66). E. coli exposed to 1.9
to 3.9 percent trichloroethylene exhibited reduced survival in pro-
portion to the dose, with the higher dose being 100 percent lethal
(67).
While trichloroethylene is itself a noncorrosive chemical, it
readily undergoes oxidation to acidic materials that are highly
corrosive, damaging many metal surfaces with which they come into
*The oropharynx is the division of the pharynx that lies between
the soft palate and upper edge of the epiglottis.
31
-------
contact.
4. Present, On«-golng Research. C68).
o "Correlation Between Breathing Zone Solvent Concentrations
and Solvent Losses from Vapor Degreasers." N. A. Esmen,
University of Delaware, School of Engineering.
A study for the U.S. Department of Defense at Frankford Arsenal
is in progress to determine whether or not present ventilation
systems offer adequate protection to workers from trichloroethylene
vapor loss. Actual concentrations in the presence and absence of
ventilation will be measured and compared to those expected from the
particular ventilation system. Causes of overexposure will be
identified and recommendations made.
o "Hepatotoxic Potential of Solvent and Amphetamine Abuse."
G..J. Troiger, University of Kansas, School of Pharmacy.
While trichloroethylene in itself does not exhibit significant
potential for the production of liver injury, its abuse, via inhala-
tion of cleaning fluids in conjunction with potentiating agents such
as acetone (via inhalation of airplane glue) or amphetamines, may
represent a potential hazard. This project will evaluate the ef-
fects of acetone and amphetamine on chlorinated hydrocarbon hepato-
toxicity under conditions similar to those present during abuse.
Both adult and immature animals will be tested.
o "Behavioral/Neurological Evaluation of Solvent Exposures."
B. Gutnik and C. Xintaros, U.S. Department of Health,
Education and Welfare, P.H.S. Center for Disease Control.
Approximately 150 workers who experience chronic occupational
exposure to trichloroethylene will be studied to: (a) detect behav-
32
-------
ioral and neurological changes; (b) correlate these changes with
exposure, body burden, accidents, and illnesses derived from their
records; and (c) ascertain the effectiveness of behavioral function
measurements as an early warning indicator of adverse exposure.
o "Quick Response Evaluation of Behavioral Effects of Tri-
chloroethylene." C. Xintaros and H. Cohen, U.S. Department
of Health, Education and Welfare, P.H.S. Center for Disease
Control.
This project will assess the validity of findings reported by
Salvini et al. 1971 C31) concerning trichloroethylene effects on
human performance capabilities at the current exposure level of 100
ppm. This work is necessary before the Department of Labor estab-
lishes a new Trichloroethylene Standard.
33
-------
C. AMBIENT CONCENTRATIONS, POPULATION AT RISK AND MEASUREMENT
TECHNOLOGY
It has been estimated that approximately 600,000 tons of tri-
chloroethylene are released to the atmosphere each year and that
10,000 tons are released to the ocean (64), a combined loss of 610,000
tons per year, or approximately 60 percent of total world production.
However, trichloroethylene is not considered to be a persistent envi-
ronmental contaminant because it has a low water solubility, high vapor
pressure, and rapid atmospheric photodegradation rate (sea level half-
life of 0.3 days). Using the methodology described in the NAS publi-
cation "Assessing Ocean Pollutants" (1975), a transport model for
trichloroethylene has been prepared (64). From this analysis, it is con-
cluded that trichloroethylene is leaving the biosphere as rapidly as
it is being introduced, and is not accumulating. The short half-life
and low concentration suggest that trichloroethylene will not contri-
bute significantly to the levels of chlorine in the stratosphere.
Based on data concerning water solubility and vapor pressure and by
comparision with similar compounds, CC1, and CoCl,, bioconcentration
of trichloroethylene should not be a significant environmental
factor.
A summary of typical concentrations of trichloroethylene in the
various sectors of the environment is presented in Table V. Ambient
concentrations in air are about 11 nanograms/m-*, or 20 parts per
trillon (ppt). In water, background concentration levels are approx-
imately 0.6 nanograms/liter (0.1 ppt) (64). A background concentra-
34
-------
TABLE V
OCCURRENCE OF TRICHLOROETHYLENE IN THE ENVIRONMENT
TYPICAL CONCENTRATIONS (W/W)
Air
Rainwater
Surface water
Potable water
Sea water
Marine sediments
Marine invertebrates
Fish
Waterbirds
Marine mammals
Fatty foods
Non-fatty foods
Human organs
Human body fat
MINIMUM
io-9
io-11
-11
10 1J-
io-11
io-10
io-10
io-9
10"9
_q
10 y
-9
10
io-9
io"9
io-9
io-9
MAXIMUM
io-8
io-9
_Q
10
io-9
io-9
io-9
io-8
io-8
_-J
> 10
Q
> 10 B
ID'8
io-9
io"9
io-8
Source: McConnell, G., Ferguson, D.M. and Pearson, C.R.
"Chlorinated Hydrocarbons and the Environment."
Endeavor 34. 13-18 (1975).
35
-------
tion in western Ireland of 15 ppt for the period June-July 1975 was
reported (69). Areas far removed from urban industrialized centers,
however, reported values of less than 5 ppt. Such areas include
sites over the North Atlantic (October 1973) (64) and rural Pullman,
Washington (December 1974-February 1975) (70).
Ambient levels of trichloroethylene in the vicinity of the
production facilities have not been reported. However, it is
possible to develop a computed estimate of expected levels.
Five plants in the United States produce trichloroethylene with
total annual production of 430 million pounds. Specific details on
the operational characteristics and the atmospheric emissions of
individual plants are not readily available. It is known, however,
that trichloroethylene is emitted from vents, not stacks (71). In
order to estimate ambient levels of trichloroethylene in the vicinity
of its production units, the use of diffusion equations is necessary.
Hypothetical plant conditions could be used as inputs to a Gaussian
plume equation* from Turner's Workbook of Atmospheric Dispersion Esti-
*Ground-level downwind concentrations resulting from a point source
are predicted by the following equation:
X(x, 0, 0; H) = 9 exp |"-l/2(Ji)2l
™y az V I °z J
where: Q = uniform emission rate (grams/sec)
u = mean wind speed affecting the plume (meter/sec)
H = effective stack height; that is, sum of stack height
plus plume rise (meters)
a = horizontal dispersion coefficient evaluated in terms of
downwind distance to the point for which the concentra-
tion is being computed (meters) -
az = vertical dispersion coefficient evaluated in terms of
downwind distance to the point for which the concen-
tration is being computed (meters)
X = ground-level concentration on plume axis (grams/meter^)
36
-------
mates (72). The basic diffusion equation should be modified, however,
due to the effect of the plant itself on the flow of air. Mechanical
turbulence in the wake of a building tends to produce aerodynamic down-
wash, resulting in the fairly rapid diffusion of a gaseous emission down
to the ground. This region of disturbed flow extends downwind a distance
equal to several times the height of the building. While this situation
does not result in a Gaussian distributed plume, a modification of
the formula still can be employed. This is because the turbulent
mixing in the wake of the building is assumed to be distributed uni-
formly in the vertical direction, analogous to the situation where a
plume is trapped below an inversion layer. A limited vertical mixing
height can be modeled using the equation:
X(X« °' Z; H) =
where L is the limit of the mixing depth and z is <_ L. In the case
of an isolated rectangular building, it is assumed that L equals
1.5 times the building height.
In addition, there is a horizontal wind turbulence which is
assumed to result in an initial horizontal plume spread equal to the
width of the building normal to the wind direction. This is analo-
gous to an area source emission where the area source is the build-
ing top. This can be modeled using a further modification of the
basic Gaussian diffusion equation. A virtual point source is assumed
upwind from the building at a distance where the plume spread (for
37
-------
the given stability conditions) would equal the crosswind width of
the building. The modified diffusion equation is therefore:
x(x, 0, z; H) = , (1<2h)
y
where H is the building height and o1 is based on the downwind distance
to the receptor point plus the upwind distance to the vertical point
source.
Assuming that a typical plant producing trichloroethylene is
equipped with control equipment having a 98 percent removal effi-
ciency, a plant producing 280 million pounds of trichloroethylene
annually would have a potei tial trichloroethylene emission rate of
80 grams per second. With reasonable assumptions, the concentration
500 meters downwind of a plant would be approximately 570 yg/m , or
0.106 ppm.* An individual standing 500 meters downwind of a pro-
duction facility would have to remain there for 11.4 years in order
to inhale the minimum amount of trichloroethylene reported to result
in slight central nervous system depression (5 ppm, 40 hours/week
for 50 weeks). He must remain for 228 years in order to inhale an
amount equivalent to that inhaled by an industrial worker occupa-
tionally exposed to 100 ppm over an 8-hour work day.
Several studies have been performed on atmospheric concentra-
tions of trichloroethylene in vapor degreasir.g workshops where the
*Assumptions employed are: (1) trichloroethylene is nonreactive;
(2) atmospheric stability class is neutral; (3) wind speed is 6
meters/sec.; (4) building height is 50 feet (15.24 meters); and (5)
width is 100 feet (30.48 meters).
38
-------
major danger of exposure exists. In one study, Grandjean (73)
measured trichloroethylene concentrations in the air surrounding
cold trichloroethylene vats wholly lacking in safety devices or
ventilation systems. Measured values ranged from 67 to 157 ppm
(average, 105 ppm) trichloroethylene. While vapor degreasing oper-
ations were being performed, the average concentration in the air
was 167 ppm. Installation of appropriate ventilation and exhaust
systems decreased the concentration to 53 ppm. Atmospheric con-
centrations during a twice-weekly cleaning procedure were 1120
ppm outside the tank as emptying took place and 815 ppm inside
the tank for the-duration of the 30-minute cleaning operation.
Ahlmark et. al. (74) performed an extensive study of 18 degreas-
ing tanks in 14 plants in Sweden. The extent of exposure was deter-
mined in terms of time and concentrations by sampling breathing
zones for a variety of operations. Mean exposure was 50 ppm (range
0 to 400 ppm) for degreasing operations, while the highest mean
value was 225 ppm (range 10 to 375 ppm) for the cleaning operation.
Results of this study are summarized in Table VI.
The National Institute of Occupational Health and Safety has
estimated that approximately 200,000 workers are exposed to tri-
chloroethelene in the United States (1). No detailed statistics
were provided. It was estimated, however, that the majority of exposed
workers are employed in industry associated with vapor degreasing of
metals. The smaller number of workers also exposed are primarily
39
-------
TABLE VI
Job Location
TRICHLOROETHYLENE EXPOSURE IN
SWEDISH ENGINEERING WORKSHOPS*
Trichloroethylene (ppm)
Minutes** Range Mean
Open air
Less than 5 meters
from tank
Greater than 5
meters from tank
Sorting, before
degreasing
Degreasing
Sorting, after
degreasing
Cleansing
Inspection of tank
Refilling
2.5
0-0
0
4.8
4.5
2.7
4.7
2.4
4.8
4.7
4.8
0-140
0-80
0-375
0-400
0-375
10-375
0-375
10-415
23
7
32
50
46
46
70
36
*Ahlmark, A., Gerhardsson, G. and Holm, A. "Trichloroethylene
Exposure in Swedish Engineering Workshops" in Proceedings of
the XIVth Internation Congress on Occupational Health, Madrid,
Sept. 1963, pp.448-450.
**Mean time spent by each operator at the various locations.
It is understood that an operator may perform at a given
location with greater frequency than another operator.
40
-------
employed in industries which, consume trichloroethylene (e.g., dry
cleaning plants). A negligible number of workers is believed to be
exposed at production facilities. The main exposure hazard is for
the users, not the producers, of trichloroethylene, since the chemical
is synthesized in a closed-system apparatus. Dow Chemical and PPG
Industries, the two largest producers of trichloroethylene in the
United States, claim that levels in their production plants are
well below 100 ppm (63). A Dow spokesman noted that, in contrast,
the average level in degreasing plants is usually below 100 ppm, but
considerable levels above this limit are common (63). In 1973,
OSHA recommended a 100 ppm ceiling in the air as a time-weighted
average during an 8-hour workday. They also recommended a 200 ppm
maximum for 15 minute's exposure and a 300 ppm upper limit (1).
Dow and PPG claim that none of their trichloroethylene
customers use this chemical in a consumer product (73). However, it
is found in products sold directly to the public. A home cleaning
fluid found on the shelf of a suburban Washington, D.C. drugstore
was labeled as containing trichloroethylene (63). And since tri-
chloroethylene is commonly used to extract caffein from coffee and
oleoresin flavorings from spices, ingestion of this substance by the
public does occur. Current FDA limits are 10 ppm of trichloro-
ethylene In decaffeinated instant coffee, 25 ppm In decaffeinated
ground coffee; and 30 ppm in spices (63).
Determination of concentrations of trichloroethylene in air
41
-------
samples is a two-step process, requiring collection and analysis.
Collection methods include evacuated gas sampling flasks (75), plastic
bags, absorbents (79), and activated charcoal (80-82). Three types
of analytical methods are available: physical methods, such as inter-
ferometry or gas chromatography; chemical methods, which depend upon
a specific reaction of trichloroethylene; and destructive methods,
such as combustion techniques that decompose trichloroethylene and
liberate hydrochloric acid (76). Field methods for estimation of
trychloroethylene vapor in the air include use of the Davis Halide
Meter and direct reading colorimetric indicator tubes (83, 84).
Adsorption onto activated charcoal represents the easiest and
most efficient method of collection. Utilization of adsorbing
liquids is inconvenient, especially for collecting breathing-zone
samples. Use of plastic bags or evacuated containers often results
in loss of sample due to adsorption onto the walls, permeation
through the plastic, or escape around joints. On humid days, the
excessive water vapor tends to displace trichloroethylene from silica
gel when this method is employed (85).
Gas chromatography is the most specific and sensitive of all
the measurement methods in use and is the method of choice (81, 85-87).
Other methods are subject to inaccuracy dug tJ interferences by other
chlorinated solvents or chloride-containing compounds, and are accept-
able only if trichloroethylene is the sole contaminent (78, 83).
42
-------
Biologic monitoring of the exposed workers is also possible.
A preferred method consists of breath analysis—that is, determina-
tion of the trichloroethylene concentration in the exhaled air of a
given worker. It has been determined that a breath sample collected
approximately three hours after exposure will provide a concentration
of trichloroethylene that is directly proportional to the time-
weighted average concentration experienced during exposure (30).
43
-------
D. SOURCES
Trichloroethylene was first prepared by Fischer in 1864 in the
course of experiments on the reduction of hexachloroethane with
hydrogen. A process for the manufacture of trichloroethylene from
acetylene was developed in Vienna between 1903 and 1905, and commer-
cial production commenced in 1908. Trichloroethylene was not pro-
duced commercially in the United States until 1925. At that time,
only a few hundred tons per year were consumed in minor extraction
processes and in such products as boot polish and printers' ink
driers. It was not until the 1930's that the applications in metal
degreasing and dry cleaning operations placed trichloroethylene in
strong demand (2).
Before 1967, 85 percent of the trichloroet^vlene produced in
the United States was prepared from acetylene by chlorination to
form 1,1,2,2-tetrachloroethene, followed by dehydrochlorination of
the latter to the desired product. At present, 85 percent of tri-
chloroethylene production proceeds via the chlorination or oxyhy-
drochlorination of ethylene, with the intermediate formation of
ethylene dichloride. The latter is then further chlorinated to tri-
chloroethylene (1) .
There are five producers of trichloroethylene in the United
States today. The locations of their plants and their production
capacities are listed in Table VII. A map of the production facil-
ities is given in Figure 1. Trichloroethylene is also produced in
44
-------
TABLE VII
TRICHLOROETHYLENE PRODUCTION (in 1970)'
PRODUCER
Diamond Shamrock
Dow Chemical
Ethyl Corporation
Occidental Petroleum
(Hooker)
PPG Industries
LOCATION
Deer Park, Texas
Freeport, Texas
Baton Rouge, Louisiana
Taft, Louisiana
CAPACITY
Million Lbs./Yr.
100 (5 x 104 tons)
150 (7.5xl04 tons)
50 (2.5xl04 tons)
40 (2 x 104 tons)
Lake Charles, Louisiana 280 (1.4x10 tons)
Total 620 x 10 Ibs.
(3.1 x 10 tons)
Source: Chemical Information Services, Stanford Research Institute,
1975 Directory of Chemical Producers - USA Page 725.
45
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FIGURE 1
TRICHLOROETHYLENE PRODUCTION CAPACITY
= 100 million pounds/year
(5 x 10A tons)
-------
many countries around the world and a significant amount has been
imported into the United States over the years.
The annual peak production level of trichloroethylene in the
United States occurred in 1970. During that year, 610 million pounds
(305,000 tons) were manufactured. In 1966, the classification of
trichloroethylene as a photochemically reactive smog contributant re-
sulted in a decreased use of the chemical, which was subsequently re-
flected in production figures. At present, about 430 million pounds
(215,000 tons) are manufactured in the United States (63). The world
annual production capacity is estimated (1973) to be approximately
one million tons (62).
Trichloroethylene is produced by feeding oxygen-free high-purity
chlorine gas and acetylene into a packed tower at 50°C and atmo-
spheric pressure. The tower is equipped with a condenser to reflux
part of the tetrachloroethane product. Chlorine and acetylene react
to form tetrachloroethane, which is partially withdrawn from the
reactor, vaporized, and superheated to 300°C. It is then fed to a
tower filled with activated carbon (dehydrochlorination), where
trichloroethylene is formed. Hydrogen chloride, trichloroethylene,
and unconverted tetrachloroethane from the dehydrochlorination are
fed to a stripping column where the hydrogen chloride is stripped off
overhead and absorbed in water as hydrochloric acid. Bottoms are
fed to a second stripper where trichloroethylene is taken off over-
head. This process for producing trichloroethylene has two air
47
-------
pollution emission points, the vent on the reflux condenser connected
to the reactor and the vent on the tail gas absorber (71).
Over 90 percent of all trichloroethylene produced is used by
industrial metal fabricating plants for vapor degreasing. Since
the late 1960's, tetrachloroethylene and methylene chloride have also
been used for this purpose. However, trichloroethylene still com-
mands 50 percent of the vapor degreasing market. The remaining 5 to
10 percent of the trichloroethylene produced is utilized for a wide
variety of applications (2). As an extractive solvent, trichloro-
ethylene has been used for the selective extraction of foods and
medicines, including fish meal, meat meal, oil-containing seeds, soya
beans, coffee beans (for decaffeination), spices, and alkaloids.
Analyses of a wide range of foods of both anima^ and vegetable origin
for trichloroethylene residues have been performed. The results are
presented in Table VIII. General Foods, Inc., the largest producer of
decaffeinated coffee, has recently disclosed that it is abandoning
the use of trichloroethylene for decaffeinating coffee. Instead, it
is replacing this solvent with methylene chloride (88). As a dry
cleaning solvent, trichloroethylene has been used for removing oils
and waxes from both natural fibers (cotton and wool) and synthetic
fibers (rayon, fiberglass, and cotton polyester material) by the
textile industry. Other minor applications include: fur cleaning
agent, motion picture film cleaner, dilutent or carrier in paints,
adhesives and varnishes, formulation in paint removers, low tempera-
48
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TABLE VIII
TRICHLOROETHYLENE IN FOODSTUFFS
(CONCENTRATIONS IN ug/kg)
FOODSTUFF TRICHLOROETHYLENE
Dairy Produce:
Fresh milk 0.3
Cheshire cheese 3
English butter 10
Hen's eggs 0.6
Meat:
English beef (steak) 16
English beef (fat) 12
Pig's liver 22
Oils and fats:
Margarine 6
Olive oil (Spanish) 9
Cod liver oil 19
Vegetable cooking oil 7
Castor oil ND
Beverages:
Canned fruit drink 5
Light ale 0.7
Canned orange juice ND
Instant coffee 4
Tea (packet) 60
Wine (Yugoslav) 0.02
Fruit and vegetables:
Potatoes (S.Wales) ND
Potatoes (N.W. England) 3
Apples 5
Pears 4
Tomatoes* 1.7
Black grapes (imported) 2.9
Fresh bread 7
*Tomato plants were grown on a reclaimed lagoon at Runcorn Works of
ICI.
ND - Not detected.
Source: McConnell, G., Ferguson, D.M. and Pearson, C.R. "Chlorinated
Hydrocarbons and the Environment." Endeavor 34. 13-18 (1975)
49
-------
ture heat transfer agent, and chemical Intermediate in the synthesis
of glycolic and dichloroacetic acids. Trichloroethylene also ex-
periences limited use as an analgesic and general anaesthetic, with
about 60,000 patient exposures per year (63). Industrial uses are
summarized in Table IX and a flow chart of distribution is presented
in Figure 2.
50
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TABLE IX
INDUSTRIAL OR END USE OF TRICHLOROETHYLENE (1974)
USE
Vapor degreasing of metals
Food and drug extraction
(fish meal, meat meal, oil containing seeds,
soyabeans, coffee beans, spices and alkaloids)
Drycleaning solvent
Solvent in textile industry
Fur cleaning agent
Motion picture film cleaner
Dilutent or carrier in paints, adhesives, and
varnishes
Formulation in paint remover
Low temperature heat transfer agent
Chemical intermediate in the synthesis of glycolic
and dichloroacetic acids
Analgesic and general anesthetic
PERCENT
> 90
AMOUNT
(Millions Lbs.)
389 (1.95xl05 tons)
< 10
341 (1.7x10 tons)
-------
FIGURE 2
SUMMARY OF PRODUCT RELEASE INFORMATION
Ln
to
Trichloroethylene
R = 429.5 million Ibs/yr
(2.15 x 105 tons/yr)
Imports
60.7 million Ibs/yr
(3 x 10* tons/yr)
Export.,
42.0 million 3bs/yr
(2.1 x 10* tons/yr)
Total
Productio
(P)
426.7 mil
(2.13x105
i
Loss of c
6.4 mill!
(3.2 x 10
FPI. " °'°
U.S.
n 1974
. Ibs/yr
tons/yr)
N
r
ompound
on Ibs/yr
3 tons)
15
X
Loss of by-produc
N.A.
1 t
Total U.S.
Consumption
(0
445.4 million Ibs/yr
(2.23xl05 tons/yr)
t
FD = 0.95
Dispersive use
42J.1 million Ibs/yr
(2.12 x 105 tons/yr)
1.7 x 1C
Million Ib
389 ^
1.95 x 105
34.1.
tons/yr
s/yr
Metal
Cleaner
tons/yr
Other
extractant
In food proc. ,
solvent,
chemical
intermediate,
anesthetic
Source: S.L., Chan, F.Y., Jones, J.L., Liu, D.H., McCaleb, K.E., M.N.T., Sopios, K.N.
and Schendel, D. E. "Research Program on Hazard Priority Ranking of Manufactured
Chemicals." SRI Project ECU-3386. Stanford Research Institute, Menlo Park, California.
R = production rate
F = fraction dispersal
PL = fraction of production lost
-------
E. CONTROL
Workers in industrial or commercial operations utilizing tri-
chloroethylene run the major risk of exposure. Therefore, it is
essential that careful controls be implemented such that the time-
weighted average concentration in the atmosphere over an 8-hour work
day for these personnel does not exceed 100 ppm. Several methods
are available to control the emission of solvent vapors into the
general work environment (1)•
1. Substitution of Less Harmful Solvents. Any solvent con-
sidered a potential replacement for trichloroethylene must first be
examined in terms of effectiveness, relative volatility, volume of
air required to dilute the vapor in the work environment to a safe
level, relative amounts of each solvent required for the task, like-
lihood of control of vapor concentration, and flammability. Tetra-
chloroethylene. and dichloroethylene have been found effective in both
degreasing and dry cleaning applications (63, 2).
2. Proper Design of Condensation Apparatus. High concentrations
of trichloroethylene in the atmosphere, especially around degreasing
operations, are a result of solvent escape from evaporation and
spills. It is, therefore, important to control the evaporation and
condensation rates by an appropriate balance between heat input and
condensation capacity of refrigerated condenser coils.
3. Process Ventilation and Process Location. Ventilation is
by far the most common engineering method for controlling solvent
53
-------
vapors and vapor recovery systems are possible when a high airflow
exhaust system is required for good ventilation. Grandjean (73)
investigated the effectiveness of a fixed lateral exhaust system,
intended to remove rising trichloroethylene vapor at the top of a
degreasing tank. The system lowered the average trichloroethylene
concentration from 167 to 112 ppm. In one case where both an ex-
haust system and a vapor condensation system were operating, the
average concentration of atmospheric trichloroethylene was reduced
from 105 to 30 ppm.
A further decrease in the concentration of trichloroethylene
vapors can be expected if the degreasing operation is located in a
large room with good ventilation wherein the entire work area is
continuously flushed with uncontaminated air. I." the exhaust system
is properly designed, it will prevent the accumulation or recircula-
tion of trichloroethylene vapors in the operation area. In the
Grandjean study (73), addition of an air-blowing system to improve
general ventilation further lowered the trichloroethylene concentra-
tion from 112 to 53 ppm. Areas in the vicinity of doors, windows,
or other possible sources of draft conditions should be avoided
since excessive air movements could decrease the effectiveness of
local exhaust systems. Skinner (89) reported the use of baffles on
windows near degreasers to control high velocity drafts. This pro-
cedure reduced the trichloroethylene concentration from a range of
170 to 230 ppm to 30 to 40 ppm.
54
-------
Finally, trtchloroethylene vapors should be kept away from
high energy-high temperature sources to reduce the possibility of
decomposition Into chlorine, hydrogen chloride, or phosgene.
4. Proper Effluent Treatment. Scrubbers used on packed towers,
such as those used for the production of trichloroethylene, have
control efficiencies ranging from 90 percent to close to 100 per-
cent (90, 91).
5. Proper Handling, Maintenance, and Disposal Procedures. In
small quantities, trichloroethylene should be stored and transported
in lined tins or galvanized mild steel drums fitted with screwcaps
or other suitably tight tops. Small quantities may also be stored in
amber or green-colored glass containers. Large quantities should
be stored in mild steel tanks fitted with a drier to prevent the
ingress of moist air. Ventilation should lead to a safe point out-
side the storage area (2).
Immediate cleanup of spills, periodic inspection of equipment,
and immediate repair of damaged equipment and leaks must be practiced
to minimize both atmospheric contamination and accidental skin contact
with trichloroethylene. Waste materials from cleaning that are con-
taminated should be stored in a well-ventilated area until ready for
disposal, and eventually incinerated. Small quantities of trichloro-
ethylene should be poured into a mixture of 10 percent soda ash and
sand, placed in a suitable container, and incinerated (1).
Since a wide spectrum of adverse effects, ranging from head-
55
-------
aches to fatalities, have been reported subsequent to trichloroethy-
lene exposure, it is essential that concentrations to which workers
are exposed remain below the presently established "no effects"
level of 100 ppm. Thus, effective monitoring programs must be es-
tablished. Breathing-zone samples should be collected frequently for
each type of job in which exposure is suspected. The sample should
be collected by drawing air through a charcoal tube to trap the
organic vapors and extraction of the trapped sample may be accom-
plished with carbon disulfide. An aliquot may then be injected into
a gas chromatograph and trichloroethylene concentration determined
(60).
56
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86. Ahlmark, A., Gerhardsson, G., and Holm, A., "Trichloroethylene
exposure in Swedish engineering workshops," Proceedings of
the XlVth International Congress on Occupational Health, Madrid,
September 1963, pp 448-50.
63
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87. Stock, V. T., Jr., Forrest, D. E., and Wahl, K. K., "Determination
of trichloroethylene in air," Am. Ind. Hyg. Assoc. J. 22, 184-
86, 1961.
88. Anonymous, Washington Post, July 17, 1975.
89. Skinner, J. B., "Control of health hazards in the operation of
metal degreasers," Am. Ind. Hyg. Assoc. Quart 13, 11-16, 1952.
90. Kempner, S. K., E. N. Seller, and D. H. Bowman, "Performance of
commercially available equipment in scrubbing hydrogen chlorid
gas," J. of the Air Pollution Control Association, Volume 20,
No. 3, pg. 139-143.
91. Dyer, J., and J. W. Wett, "Scrubber collects HC1 and other pollu-
tants,1' Chemical Processing, January 1969.
92. U.S. Dept. of Health Education and Welfare, J. A. Danielson,
editor—Air Pollution Engineering Manual, 1967.
64
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
MTR-7142
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
Air Pollution Assessment of Trichloroethylene
5. REPORT DATE
February 1976
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
B. B. Fuller
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
The Mitre Corporation
McLean, Virginia 22101
10. PROGRAM ELEMENT NO.
11 CONTRACT/GRANT NO.
68-02-1495
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-AWM
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Trichloroethylene is an organic solvent primarily used for the vapor
degreasing of metals. Approximately 200,000 industrial workers are exposed
to this solvent annually. Although the major physiological response in
humans from acute or chronic exposure to trichloroethylene is central nervous
system depression, damage to liver, kidney and heart have also been reported.
Since the metabolic fate and toxic effects of trichloroethylene are similar
in many mammalian species to those in man, the fact that this compound has
recently been implicated as a potent liver carcinogen in mice may be of
significance.
Approximately 60% of the total world production of trichloroethylene is
released to the environment each year. However, due to its low water solubility,
high vapor pressure and-high atmospheric photodegradation rate, trichloroethylene
is not expected to persist in the environment. Ambient concentrations in the
atmosphere of industrialized areas are only about 16 ppt. Proper use of local
exhaust systems in conjunction with vapor condensation appratus and good
general ventilation should be sufficient to maintain levels of trichloroethylene
in the workshop environment well below the recommended 100 ppm and to insure
a minimum release to the ambient atmosphere.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cos AT i Field/Group
Organic Compounds
Organic Solvents
Physiological Effects
Industrial Plants
Air Pollution Control
Stationary Sources
Hydrocarbons
Carcinogens
Air Pollution
18 DISTRIBUTION STATEMENT
Unlimited
19 SECURITY CLASS (This Report!
Unclassified
21 NO OF PAGES
70
20 SECURITY CLASS (Thispage)
Unclassified
22 PRICE
EPA Form 2220-1 (9-73)
65
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