SRC TH 81-568
SECOND DRAFT
HEALTH RISK ASSESSMENT
DOCUMENT FOR TOLUENE
Prepared by:
Center for Chemical Hazard Assessment
Syracuse Research Corporation
Merrill Lane
Syracuse, New York 13210
NOTICE
This document is a preliminary draft. It
has not been formally released by the EPA
and should not at this stage be construed
to represent Agency policy. It is being
circulated for comment on its technical
accuracy and policy implications.
DRAFT: DO NOT CITE OR QUOTE
June 1981
Contract No. 68-02-377
Assignment No. 6
Task No. L1434-11
""rolect Officer: Dr. Robert M. Bruce
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TABLE OF CONTENTS
Page
1.0 EXECUTIVE SUMMARY 1-1
1.1 ENVIRONMENTAL SOURCES, FATE, AND LEVELS 1-1
1.2 EFFECTS ON HUMANS 1-4
1.3 ANIMAL STUDIES 1-5
1.4 P HA RMA CO KINETICS . 1-7
1.5 CARCINOGE NICETY, MUTAGENICITY, AND TERATOGENICITY 1-8
1.6 EFFECTS ON ECOSYSTEMS 1-8
1.7 RISK ASSESS ME NT 1-9
2.0 INTRODUCTION 2-1
3.0 PHYSICAL AND CHEMICAL PROPERTIES 3-1
3.1 SYNONYMS AND TRADE NAMES 3-1
3.2 IDENTIFICATION NUMBERS " 3-1
3.3 STRUCTURE, MOLECULAR FORMULA, AND MOLECULAR WEIGHT 3-1
3.4 PHYSICAL PROPERTIES 3-1
3.4.1 Description 3-1
3.4.2 Other Physical Properties 3-1
3.4.3 Significance of Physical Properties with
Respect to Environmental Behavior 3-2
3.5 CHEMICAL PROPERTIES 3-3
4.0 PRODUCTION, USE, AND RELEASES TO THE ENVIRONMENT 4-1
4.1 MANUFA CUT RING PROCESS TECHNOLOGY 4-1
4.1.1 Petroleum Refining Processes 4-1
4.1.1.1 Catalytic Reforming 4-1
4.1.1.2 Pyrolytic Cracking 4-3
4.1.2 By-Product of Styrene Production 4-3
4.1.3 By-Product of Coke-Oven Operation 4-3
4.2 PRODUCERS 4-4
4.3 USERS 4-4
4.4 ENVIRONMENTAL RELEASE 4-14
4.4.1 Emission from Production Sources 4-14
4.4.2 Emission from Toluene Usage 4-22
4.4.3 Emission from Inadvertent Sources 4-22
4.4.4 Sum of Emissions .from All Sources 4-26
4.5 USE OF TOLUENE IN CONSUMER PRODUCTS 4-29
5.0 INDUSTRY ABATEMENT PRACTICES 5-1
5.1 ABATEMENT PRACTICES FOR INADVERTENT SOURCES 5-1
5.2 ABATEMENT PRACTIVES FOR SOLVENT USAGE 5-2
5.3 ABATEMENT FOR COKE OVEN EMISSIONS 5-3
5.4 ABATEMENT FOR EMISSIONS FROM MANUFACTURING SITES 5-3
5.5 ABATEMENT PRACTICES FOR RAW AND FINISHED WATERS 5-3
5.6 ECONOMIC BENEFITS OF CONTROLLING TOLUENE EMISSIONS 5-3
ii
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TABLE OF CONTENTS (Cont.)
Page
6.0 ENVIRONMENTAL FATE, TRANSPORT, AND PERSISTENCE 6-1
6.1 AIR 6-1
6.1.1 Fate in Air 6-1
6.1.2 Transport 6-5
6.2 AQUATIC MEDIA " 6-6
6.2.1 Fate ' 6-6
6.2.2 Transport 6-7
6.3 SOIL 6-9
6.3.1 Fate 6-9
6.3.2 Transport ' 6-10
6.3.2.1 Soil to Air 6-10
6.3.2.2 Soil to Water 6-10
6.4 ENVIRONMENTAL PERSISTENCE 6-11
6.4.1 Biodegradation and Biotransformation 6-11
6.4.1.1 Mixed Cultures 6-11
6.4.1.2 Pure Cultures 6-13
7.0 ENVIRONMENTAL AND OCCUPATIONAL CONCENTRATIONS 7-1
7.1 ENVIRONMENTAL LEVELS 7-1
7.1.1 Air 7-1
7.1.2 Aqueous Media 7-4
7.1.2.1 Surface Waters 7-5
7.1.2.2 Industrial Wastewaters 7-5
7.1.2.3 Publicly-Owned Treatment Works (POTW) 7-8
7.1.2.4 Underground Water 7-10
7.1.2.5 Drinking Water 7-10
7.1.2.6 Rainwater 7-11
7.1.3 Sediment 7-11
7.1.4 Edible Aquatic Organisms 7-11
7.1.5 Solid Wastes and Leachates 7-12
7.2 OCCUPATIONAL CONCENTRATIONS 7-12
7.3 CIGARETTE SMDKE 7-17
8.0 ANALYTICAL METHODOLOGY 8-1
8.1 AIR 8-1
8.1.1 Ambient 8-1
8.1.1.1 Sampling 8-1
8.1.1.2 Analysis 8-2
8.1.1.3 Preferred Method 8-4
8.1.1.4 Detection Limits 8-5
8.1.2 Occupational Air 8-5
8.1.2.1 Sampling 8-5
8.1.2.2 Analysis 8-6
8.1.2.3 Preferred Method 8-8
8.1.2.4 Detection Limit 8-9
8.1.3 Forensic Air 8-9
8.1.4 Gaseous Products from Pyrolysis of Organic Wastes 8-9
iii
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TABLE OF CONTENTS (Continued)
8.2 WATER 8-10
8.2.1 Sampling 8-10
8.2.2 Analysis 8-10
8.2.2.1 Purge and Trap 8-11
8.2.2.2 Headspace Analysis 8-12
8.2.2.3 Sorption on Solid Sor.bents 8-13
8.3 SOILS AND SEDIMENTS 8-13
8.3.1 Sampling 8-13
8.3.2 Analysis 8-14
8.4 CRUDE OIL AND ORGANIC SOLVENTS . 8-15
8.5 BIOLOGICAL SAMPLES 8-15
8.5.1 Blood 8-15
8.5.2 Urine 8-16
8.6 FOODS 8-16
8.7 CIGARETTE SMOKE " 8-17
9.0 EXPOSED POPULATIONS 9-1
10.0 EXPOSURE ASSESSMENT 10-1
10.1 EXPOSURE VIA INHALATION 10-2
10.1.1 Theoretical Modeling 10-3
10.1.2 Inhalation Exposure Based on Monitoring Data 10-8
10.2 INGESTION EXPOSURE BASED ON MONITORING DATA 10-11
10.2.1 Exposure from Drinking Water 10-11
10.2.2 Exposure from Edible Aquatic Organisms 10-11
10.3 OCCUPATIONAL EXPOSURE 10-11
10.4 CIGARETTE SMDKERS 10-12
10.5 LIMITATIONS OF EXPOSURE ASSESSMENT BASED ON MONITORING DATA 10-13
10.6 COMPARISON BETWEEN EXPOSURE DATA BASED ON THEORETICAL AND
EXPERIMENTAL VALUES 10-13
11.0 EFFECTS ON HUMANS 11-1
11.1 EFFECTS ON THE NERVOUS SYSTEM 11-1
11.1.1 Central Nervous System 11-1
11.1.1.1 Acute Effects 11-1
11.1.1.2 Subchronic and Chronic Effects 11-9
11.1.2 Peripheral Nervous System 11-18
11.2 EFFECTS ON THE BLOOD AND HEMATOPIETIC TISSUE 11-24
11.2.1 Bone Marrow 11-24
11.2.2 Blood Coagulation 11-34
11.2.3 Phagocytic Activity of Leukocytes 11-34
11.2.4 Immunocompetence 11-34
11.3 EFFECTS ON THE LIVER 11-35
11.4 EFFECTS ON THE KIDNEYS 11-39
11.5 EFFECTS ON THE HEART 11-43
11.6 EFFECTS ON MENSTRUATION 11-44
iv
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TABLE OF CONTENTS (Cont.)
11.7 EFFECTS ON THE RESPIRATORY TRACT AND THE EYES 11-45
11.7.1 Effects of Exposure 11-45
11.7.2 Sensory Thresholds 11-47
11.8 EFFECTS ON THE SKIN 11-49
11.9 SUMMARY . 11-49
12.0 ANIMAL TOXICOLOGY 12-1
12.1 SPECIES SENSITIVITY 12-1
12.1.1 Acute Exposure to Toluene 12-1
12.1.1.1 Acute Inhalation . 12-1
12.1.1.2 Acute Oral Toxicity 12-13
12.1.1.3 Acute Effects from Intraperitoneal
Injection 12-14
12.1.1.4 Acute Effects from Subcutaneous Injection 12-15
12.1.1.5 Acute Effects from Intravenous Injection 12-15
12.1.1.6 Acute and Subactue Effects of
Percutaneous Application 12-15
12.1.2 Subchronic and Chronic Exposure to Toluene 12-16
12.2 EFFECTS ON LIVER, KIDNEY, AND LUNGS 12-21
12.2.1 Liver 12-21
12.2.2 Kidney 12-25
12.2.3 Lungs 12-26
12.3 BEHAVIORAL TOXTCITY AND CENTRAL NERVOUS SYSTEM EFFECTS 12-27
12.4 EFFECTS ON OTHER ORGANS 12-40
12.4.1 Blood-Forming Organs 12-40
12.4.2 Cardiovascular Effects 12-48
12.4.3 Gonadal Effects 12-49
12.5 SUMMARY 12-49
13.0 PHA RMA CO KINETIC CONSIDERATIONS IN HUMANS AND IN ANIMALS 13-1
13.1 ROUTES OF EXPOSURE AND ABSORPTION 13-1
13.2 DISTRIBUTION 13-11
13-3 METABOLISM 13-16
13.4 EXCRETION 13-23
13.5 SUMMARY 13-34
14.0 CARCINOGENICITY, MUTAGENICITY, AND TERATOGENICITY 14-1
14.1 CARCINOGENICITY 14-1
14.2 MUTAGENICITY 14-2
14.2.1 Mutagenesis in Microorganisms 14-2
14.2.2 Growth Inhibition Tests in Bacteria 14-4
14.2.3 Mutagenesis in Cultured Mammalian Cells 14-6
14.2.4 Cytogenetic Test Systems 14-6
14.2.4.1 Micronucleus Test 14-6
14.2.4.2 Chromosomal Aberrations 14-6
14.2.4.3 Sister Chromatid Exchange 14-12
14.3 TERATOGENICITY 14-16
14.3.1 Animal Studies 14-16
14.3.2 Effects in Humans 14-24
14.4 SUMMARY 14-25
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TABLE OF CONTENTS (Cont.)
15.0 SYNERGISMS AND ANTAGONISMS AT THE PHYSIOLOGICAL LEVEL 15-1
15.1 BENZENE AND TOLUENE 15-1
15.2 XYLENES AND TOLUENE 15-3
15.3 TOLUENE AND OTHER SOLVENTS 15-4
16.0 ECOSYSTEM CONSIDERATIONS - 16-1
16.1 EFFECTS ON VEGETATION 16-1
16.1.1 Introduction 16-1
16.1.2 Effects of Toluene on Plants 16-1
16.1.2.1 Algae . 16-1
16.1.2.1.1 Closed System Studies 16-1
16.1.2.1.2 Open Studies 16-2
16.1.2.2 Effects on Higher Plants 16-5
16.2 BIOCONCENTRATION, BIOACCCUMULATION, AND BIOMAGNIFICATION
POTENTIAL ' 16-8
16.3 EFFECTS ON MICROORGANISMS 6-16
17.0 EFFECTS ON AQJATIC SPECIES 17-1
17.1 GUIDELINES FOR EVALUATION 17-1
17.2 EFFECTS OF ACCIDENTAL SPILLS 17-2
17.3 LABORATORY STUDIES OF TOXTCITY 17-3
17.3.1 Lethal Effects 17-3
17.3.1.1 Freshwater Fish 17-3
17.3.1.2 Marine Fish 17-13
17.3.1.3 Freshwater Invertebrates 17-16
17.3.1.1* Marine Invertebrates 17-17
17.3.2 Sublethal Effects 17-20
17.3.2.1 Fish 17-20
17.3.2.2 Invertebrates 17-25
18.0 HUMAN RISK ASESSMENT 18-1
18.1 EXISTING GUIDELINES AND STANDARDS ' 18-1
18.1.1 Air 18-1
18.1.2 Water 18-2
18.1.3 Food 18-3
18.2 INHALATION EXPOSURES 18-4
18.2.1 Effects of Single Exposures 18-4
18.2.2 Effects of Intermittent Exposures Over
Prolonged Periods 18-7
18.2.3 Acceptable Daily Intake (ADI) Based on
Inhalation Exposure 18-12
18.3 ORAL EXPOSURES 18-14
18.4 DERMAL EXPOSURES 18-15
18.5 RESPONSES OF SPECIAL CONCERN 18-16
18.5.1 Carcinogen! city 18-16
18.5.2 Mutagenicity 18-16
18.5.3 Teratogenicity 18-17
REFERENCES R-1
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1. EXECUTIVE SUMMARY
1.1 ENVIRONMENTAL SOURCES, FATE, AND LEVELS
Toluene, a homolog of benzene that contains a single methyl group, is a
clear, colorless liquid at room temperature. The molecular formula of toluene is
C_Hg and the molecular weight is 92.13- The structural formula is given below.
Other physical properties of toluene include a melting point of -95°C, a
boiling point of 110.6°C, a flash point of U.44°C, a vapor pressure of 28.7 torr
at 25°C, and a density of 0.8669 g/ml at 20°C. Toluene is slightly soluble in
both fresh and salt water (535 mg/1 and 379 mg/1, respectively) at a temperature
of 25°C. The physical properties of toluene would indicate that toluene in the
environment is likely to be present in the air, and that toluene originally
present in water may be transferred to the atmosphere. Toluene can undergo
photochemical reactions, particularly under atmospheric smog conditions. In
aqueous media under the conditions of water chlorination, toluene may be
chlorinated followed by subsequent hydrolysis to benzaldehyde. This reaction
may account for the benzaldehyde detected in some finished drinking waters.
The general population may be exposed to toluene through inhalation of air,
ingestion of food or water, or through dermal exposure. The four largest sources
of emission of toluene to the atmosphere are, in descending order of importance,
automobile use, industrial use of toluene as a solvent, coke ovens, and toluene-
producing industries. Other than exposure via the air, toluene has been detected
in drinking water and the flesh of edible fish. Dermal exposure to toluene is
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only important in the workplace. The estimated quantities of toluene taken in by
the general public from each source are between a trace and 94 mg/week by inhala-
tion (depending on whether an individual resides in an urban or rural area or
near an industry that uses toluene) and 0.0 to 0.75 mg/week from food and water.
Occupational exposure (up to 18,000 mg/week) or cigarette smoking (14 mg/week
from 140 cigarettes) will increase an individual's exposure to toluene.
Although there are technical problems with estimating inhalation exposure to
toluene, there is reasonable agreement between the values obtained by dispersion
modeling and those obtained from calculations using monitoring data.
The total amount of toluene produced in the United States in 1978 was
3595 million kg. The majority (96.5$) is produced by catalytic reformation from
selected petroleum fractions, and the remainder is produced from pyrolytic
cracking, and as a recovered by-product of styrene production and coke oven
emission. This value of 3595 million kg is for isolated toluene and accounts for
only 11/6 of the total toluene produced, the remaining 89$ of the toluene produced
is not isolated as pure toluene but is a benzene-toluene-xylene mixture used in
gasoline. Other uses of toluene are feed stock for the production of benzene and
other chemicals, as a gasoline additive, and as a solvent.
Activities associated with automobiles (marketing and evaporation of gaso-
line and automobile exhaust) are the largest single atmospheric source of toluene
(677 million kg/year), with industries using toluene as a solvent (the paint and
coating, adhesive, ink, and pharmaceutical industries) being the second largest
emitter of toluene to the atmosphere (375 million kg/year). These two sources
account for 75% of the toluene emitted to the atmosphere. The amount of toluene
released to other media in the environment is small and is equal to approximately
0.15$ of the total amount released to the atmosphere.
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The preferred method for the monitoring of toluene in ambient air consists
of sorbent collection, thermal elution, and GC-FID determination. For a 25 1
sample, the detection limit is<0.1 ppb. Purge and trap with GC-photoionization
detection is the most widely used method for the analysis of toluene in aqueous
samples. With a 5 ml sample, the method has a detection limit of 0.1 ppb.
Toluene is the most prevalent aromatic hydrocarbon in the atmosphere, with
average measured levels ranging from 0.14 to 59 ppb. Toluene has also been
detected in surface waters and in treated wastewater effluents at levels
generally below 10 ppb. Concentration of toluene as high as 19 ppb has been
detected in a drinking water supply. In a study" of toluene, 95$ of the sample
contained less than 1 ppm of toluene. The atmosphere is the major environmental
receiver for toluene. It has been estimated that approximately 124 million
people in the U.S. are exposed to atmospheric toluene at a concentration level
greater than 1 ug/m .
Toluene released to the aquatic or soil environment is at least partly
removed by biodegradation. There is little information on the rate and extent of
biodegradation in soil; however, in one study a half-life of between 20 and
60 min was observed in soil containing toluene-degrading bacteria and in a second
study 20 to 60$ of toluene was removed following percolation through 140 cm of
sand. As a result of the limited number of studies available, the extent of
toluene degradation in soil cannot be determined although studies with pure
cultures indicate that a variety of bacteria and fungi can utilize toluene, and
some pure cultures have been isolated that can use toluene as a sole source of
carbon. Toluene is also readily biodegraded in aqueous media, both in surface
water and during wastewater treatment; however, disappearance of toluene from
aqueous media is mainly through evaporation and transport to the atmosphere. The
conversion of toluene to compounds that can be utilized as sources of carbon and
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energy suggests that toluene will be degraded rapidly by microbial species pro-
liferating at the expense of the compound and will not accumulate significantly
in the environment.
1.2 EFFECTS ON HUMANS
Exposures of humans to toluene have almost exclusively involved inhalation
in experimental or occupational settings or during episodes of intentional
abuse. The health effect of primary concern is dysfunction of the central
nervous system (CNS). Acute experimental and occupational exposures to toluene
in the range of 200-1500 ppm have elicited dose-related symptoms indicative of
CNS depression, as well as impairments in reaction time and perceptual speed.
Following initial CNS excitatory effects (e.g., exhilaration, lightheadedness),
progressive development of narcosis has characterized acute exposures to exces-
sive concentrations of toluene (i.e., levels approaching the air saturation
concentration of approximately 30,000 ppm). Repeated occupational exposures to
toluene over a period of years at levels of 200-400 ppm have resulted in some
evidence of neurologic effects, and chronic exposure to mixtures of solvent
vapors containing predominantly toluene at levels of 30-100 ppm have resulted in
impaired performance on tests for intellectual and psychomotor ability and mus-
cular function. Prolonged abuse of toluene or solvent mixtures containing
toluene have, on occasion, led to residual or permanent CNS effects.
Early reports of occupational exposures ascribed myelotoxic effects to
toluene, but the majority of recent evidence indicates that toluene is not toxic
toward the blood or bone marrow. The myelotoxic effects previously attributed to
toluene are currently considered to be the result of concurrent exposure to
benzene, which was typically present as a contaminant. Acute exposures to
toluene have not resulted in any definite effects on heart rate or blood pres-
sure.
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Liver enlargement was reported in an early study of painters exposed to 100-
1100 ppm toluene for 2 weeks to more than 5 years, but this effect was not
associated with clinical evidence of liver disease or corroborated in subsequent
studies. Chronic occupational exposure to toluene or intensive exposure via glue
or thinner sniffing has generally not been associated with abnormal liver func-
tion. Evidence of renal dysfunction has been observed in workers who were
accidentally overexposed to toluene and in toluene abusers, but a single occupa-
tional study of women exposed to 60-100 ppm toluene for over 3 years did not
report abnormal urinalysis findings. Several reports have recently appeared
that associate deliberate inhalation of toluene with metabolic acidosis.
Dysmenorrhea has been reported in women exposed for over 3 years to 60-
100 ppm toluene and concommitantly to 20-50 ppm gasoline in a "few" working
places. Disturbances of menstruation have also been reported in female workers
exposed concurrently to toluene, benzene, and xylene, and to toluene and other
unspecified solvents.
Single short-term exposures to moderate levels of toluene have, on occa-
sion, been reported to cause transitory eye and respiratory tract irritation, but
irritative effects have generally not been observed in workers exposed repeti-
tively to toluene. Dermal contact with toluene may cause skin damage due to its
degreasing action.
1.3 ANIMAL STUDIES
The most pronounced effect of toluene in animal studies is on the central
nervous system. Acute exposure to inhalation of high levels of toluene has been
linked with depression of activity. Levels below 1000 ppm vapor have little or
no effect on gross observations of behavior, although lower levels have been
observed to have an effect using more sensitive methods of assay, i.e., detection
of changes in cognition and brain neuromodulator levels.
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Although early studies suggested toluene induced myelotoxicity, most
studies using toluene that contained negligible amounts of benzene have not
produced injury on blood-forming organs; however, three Russian and one Japanese
study have reported leukocytosis, impaired leukopoiesis, or chromosomal damage
in the bone marrow.
Inhalation of concentrations of up to 1085 ppm toluene for 6 weeks or
300 ppm for 24 months and ingestLon of 590 mg toluene/kg body weight for 6 months
produced no liver damage; however, several studies noted increase of liver weight
or slight histological change suggestive of possible liver damage at higher
levels of exposure or in animals treated by the intraperitoneal route.
Renal injury was noted in rats, dogs, and guinea pigs after subacute inhala-
tion of toluene vapors at doses in excess of 600 ppm in three studies, while no
renal damage was found in other subacute and subchronic studies in which rats,
dogs, guinea pigs, and monkeys inhaled vapors up to a concentration of 1085 ppm
or ingested 590 mg toluene/kg body weight.
Although no effect was observed in the lungs of rats, guinea pigs, dogs, or
monkeys after exposure to 1085 ppm toluene vapor intermittently for 6 weeks, in
rats after inhalation of up to 300 ppm toluene for 24 months, or in rats after
ingestion of 590 mg toluene/kg body weight for 6 months, other studies noted
irritation effects in the respiratory tract in dogs, guinea pigs, and rats.
Sensitization of the heart in mice, rats, and dogs was reported after inhalation
of toluene.
The acute oral toxicity (LD50) of toluene in rats is in the range of 6.0 to
7.5 g/kg, which indicates only slight toxicity in this species. An acute dermal
toxicity (LD50) was reported to be 14.1 ml/kg in the rabbit. Slight to moderate
irritation was noted in rabbit and guinea pig skin and the rabbit cornea. An
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LC50 in the range of 5500 to 7000 ppm was reported in mice and of 4050 ppm in
rats.
1.M PHARMACOKINETICS
Toluene is readily absorbed from the respiratory tract. Studies with humans
indicate that the total amount of toluene absorbed is proportional to the concen-
tration of toluene in inspired air, the length of exposure, and pulmonary venti-
lation, which in turn depends upon the level of physical activity. Approximately
50$ of the amount inspired is retained in the body. Absorption of toluene from
the gastrointestinal tract is probably fairly complete, based on excretion data
from experimental animals. Toluene is absorbed" less readily through the skin
than through the respiratory or gastrointestinal tracts.
Animals given toluene orally or by inhalation had high concentrations of
toluene in their adipose tissue and bone marrow, and moderately high concentra-
tions of toluene and its metabolites in liver and kidney. These results are
reasonable based on tissue-blood partition coefficients and known routes of
metabolism and excretion.
The initial step in the metabolism of toluene is side-chain hydroxylation by
the hepatic mixed-function oxidase system, followed by oxidation to benzoic
acid. Benzoic acid is then conjugated with glycine to form hippuric acid and
excreted in the urine. In both humans and animals, 60 to 75$ of the absorbed
toluene can be accounted for as hippuric acid in the urine, regardless of the
dose or whether the chemical was administered orally or by inhalation. Much of
the remaining toluene is exhaled unchanged. The excretion of toluene and its
metabolites is rapid; the major portion occurs within 12 hours of oral adminis-
tration or the end of inhalation exposure.
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1.5 CARCINOGENICITY, MUTAGENICITY, AND TERATOGENICITY
Inhalation exposure to toluene at concentrations of up to 300 ppm for
24 months did not produce an increased incidence of neoplastic, proliferative,
inflammatory, or degenerative lesions in various organs of rats relative to
unexposed controls. Other studies indicate that toluene is not carcinogenic when
applied topically to the shaved skin of laboratory animals and that it does not
promote the development of skin tumors following initiation with DM3A.
Toluene has been shown to be non-mutagenic in a battery of microbial,
mammalian cell, and whole organism test systems. The Russian literature reported
chromosome aberrations in the bone marrow cells of rats exposed subcutaneously
and via inhalation to toluene, but these findings have not been corroborated in
other studies of rats following intraperitoneal injection of toluene, in human
lymphocytes exposed to toluene in culture, or in lymphocytes from workers chroni-
cally exposed to toluene.
Toluene has been reported to induce cleft palates in mice following oral
exposure, but it was not teratogenic in mice or rats following inhalation expo-
sure. Embryo toxic effects (increased incidence of skeletal anomalies and signs
of retarded skeletal development, low fetal weights) and increased maternal
toxicity were, however, noted in some of the rats and mice exposed via inhala-
tion.
1.6 EFFECTS ON ECOSYSTEMS
The effects of toluene on ecosystems have been studied using aquatic organ-
isms, microbiologic organisms, and higher plants. In algae, toluene can both
stimulate and inhibit growth, depending on the species of algae and the concen-
tration of toluene. The no-effect level for most algal species is 10 mg/1.
Significant toxic effects of toluene in fish, except during accidental spills,
are unlikely because of the rapid volatilization of toluene from water. Toluene
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has only a low bioconcentration potential and is metabolized and rapidly lost
from fish, which indicates that toluene is unlikely to biomagnify through the
aquatic food chain. Toluene can impart an unpleasant taste to fish that inhabit
contaminated water. In both microorganisms and higher plants, toluene can dis-
rupt cell membranes as a result of its solvent.action and cause toxic or lethal
effects. Except in cases of intentional application or accidental spills,
toluene is unlikely to be present at levels that would cause adverse effects on
the ecosystem. Even after accidental spills, toluene would volatilize rapidly
and thus limit adverse effects.
1.7 RISK ASSESSMENT
Considerable information is available on the effects of toluene on humans
and experimental animals after inhalation exposures. Based on these data, appro-
ximate dose-response relationships and estimates of acceptable daily intake
(ADI) can be proposed. The data on oral exposure are much less satisfactory,
although one acceptable subchronic oral study using rats is available. No
information on dermal exposures suitable for use in human risk assessment was
encountered.
Based on a few studies involving controlled exposures of humans to toluene
vapors as well as some reports of occupational incidents and voluntary abuse
("glue sniffing"), the dose-response relationships for the acute effects in
humans of single short-term exposures to toluene can be estimated as:
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10,000-30,000 ppm : Onset of narcosis within a few minutes.
Longer exposures may be lethal.
>4,000 ppm : Would probably cause rapid impairment of
reaction time and coordination. Expos-
ures of 1 hour or longer might lead to
narcosis and possibly death.
1,500 ppm : Probably not lethal for exposure periods
of up to 8 hours.
300-800 ppm : Gross signs of incoordination may be
expected during exposure periods up to
8 hours.
400 ppm : Lacrimation and irritation to the eyes and
throat.
100-300 ppm : Detectable signs of incoordination may be
expected during exposure periods up to
8 hours.
200 ppm : Mild throat and eye irritation.
50-100 ppm : Subjective complaints (fatigue or head-
ache) but probably no observable impair-
ment of reaction time or coordination.
>37 ppm : Probably perceptible to most humans.
Because of the deficiencies in the studies on which these estimates are based as
well as variations in sensitivity to toluene that may be expected in the human
population, these estimates should be regarded as approximations only. Nonethe-
less, the weight of the evidence suggests that the precision of the estimates is
likely to be about +50$.
The subchronic and chronic inhalation data lend themselves less to the
definition of dose-response relationships. Most of the reports on human expo-
sures failed to define precisely levels or durations of exposure, involved rela-
tively small numbers of exposed individuals, and did not adequately control
exposure to other toxic agents. The animal data are of little use in supporting
the human data because humans appear to be more sensitive to toluene than the
experimental animals on which data are available.
1-10
-------
An ADI for humans on inhalation exposure can be derived from the available
human data using the current Threshold Limit Value (TLV) of 100 ppm. Using an
uncertainty factor of 10, the ADI is estimated to be 2.69 mg/kg body weight.
Given the limitations and inconsistencies in the human data, a reasonable upper
limit would be 5.38 mg/kg and a lower limit would be 0.27 mg/kg.
For oral exposures, an ADI can be derived from a single subchronic study
using rats. Because the information on the effects of oral exposures is scanty,
an uncertainty factor of 1000 is applied to the results of this study and the ADI
is estimated at 0.59 mg/kg body weight, which is probably more protective than
predictive of a toxic threshold.
Information on the dermal toxicity of toluene cannot be used quantitatively
for human risk assessment. Qualitatively, dermal exposure to toluene can cause
skin damage, as is the case with many solvents, but systemic signs of intoxica-
tion are likely to occur only in cases of gross overexposure.
Based on the available exposure estimates, the only group at possible high
risk from toluene are workers who are exposed at or near the TLV. For non-
occupational exposures, there seems to be a safety margin of about 6 between the
ADI for oral exposure and the current worst-case levels of exposure. Although
this is reassuring, uncertainties over the carcinogenic, and teratogenic effects
of toluene should be a matter of concern and future research.
1-11
-------
2. INTRODUCTION
At the April 18, 1980 meeting of the Toxic Substances Priorities Committee,
a decision was made to develop a multimedia integrated risk assessment document
for toluene. One of the primary objectives of this undertaking was to minimize
or eliminate inter-agency and inter-office duplication of risk assessment docu-
mentation projects. This document on toluene will serve as a pilot to test the
feasibility and value of the multimedia integrated approach to environmental
risk assessment. Toluene was chosen for this pilot study primarily because of
its inclusion on a variety of program office priority lists, since it is a
chemical produced in large quantity and exposure to the compound is widespread.
Development of the toluene documentation project was directed by EPA's Environ-
mental Criteria and Assessment Office, ORD, Research Triangle Park - Project
Officer, Mr. Mark Greenberg.
In addition to the present document for toluene, two other recent reports
contain valuable health and environmental effects data on toluene. The first is
The Alkyl Benzenes, published in 1980 by the Board on Toxicology and Environ-
mental Health Hazards, Assembly of Life Sciences, National Research Council. The
second recent review, developed by the U.S. EPA in 1980, is the Ambient Water
Quality Critiera for Toluene. EPA Report U40/5-80-075.
2-1
-------
3. PHYSICAL AND CHEMICAL PROPERTIES
Toluene is a homolog of benzene in which one hydrogen atom has been replaced
by a methyl group. Some of the relevant physical and chemical properties of
toluene are described below.
3.1 SYNONYMS AND TRADE NAMES
Toluol
Phenylmethane
Methylbenzene
Methylbenzol
Methacide
3.2 IDENTIFICATION NUMBERS
Chemical Abstracts Service (CAS) No.: 108-88-3
Registry of Toxic Effects of Chemical Substances (RTECS) No.: XS5250000
3.3 STRUCTURE, MOLECULAR FORMULA, AND MOLECULAR WEIGHT
Molecular Formula: C7Hg
Molecular Weight: 92.13
3.4 PHYSICAL PROPERTIES
3.4.1 Description
Toluene is a clear, colorless liquid at ambient temperature that has a
benzene-like odor. It is both volatile and flammable (The Merck Index, 1976).
3.4.2 Other Physical Properties
Melting Point (Weast, 1977): -95°C
Boiling Point (Weast, 1977): 110.6°C
Density (g/ml, 20°C) (Weast, 1977): 0.8669
Specific Gravity (15.6/15.6°C) (Cier, 1969): 0.8623
3-1
-------
Vapor Pressure (25°C) (Weast, 1977): 28.7 torr
Vapor Density (air = 1) (Weast, 1977): 3-20
Percent in Saturated Air
(760 mm, 26°C) (Walker, 1976): 3.94
Density of Saturated Air-Vapor
Mixture (760 mm (air =1),
26°C) (Walker, 1976): 1.09
Solubility (Sutton and Calder, 1975):
Fresh water (25°C) 534.8 mg/1
Sea water (25°C) 379.3 mg/1
Flammable Limits (percent
by volume in air) (Walker, 1976): • 1.17-7.10
Flash Point (closed cup) (Walker, 1976): 40°F
Autoignition Temperature (Walker, 1976): 552°C
Log Octanol-Water Partition
Coefficient (Tute, 1971): 2.69
Odor Threshold in Air (Walker, 1976):
Coke derived 4.68 ppm
Petroleum derived 2.14 ppm
Surface Tension (20°C) (Walker, 1976): 28.53 dynes/ cm
Liquid Viscosity (20°C) (Walker, 1976): 0.6 cp
Refractive Index (68°F) (Cier, 1969): 1.49693
Conversion Factor (in air, 25°C): 1 ppm |5«77 mg/nr
'!?' "0.265 ppm
3.4.3 Significance of Physical Properties with Respect to
Environmental Behavior
The volatility of toluene as indicated by its relatively high vapor pressure
is indicative that a substantial fraction of environmental toluene is likely to
be present in the vapor phase mixed with air. The relatively high volatility of
toluene combined with its low solubility in water may lead to intermedia transfer
of toluene from water to the air phase. The details of the environmental fate of
toluene as determined by its physical and chemical properties are discussed in
Section 6.
The log octanol- water partition coefficient for toluene may have signifi-
cance in determining its affinity toward organics in soil and aquatic organisms.
The details of the bioconcentration factor for toluene based on the octanol- water
3-2
-------
partition coefficient value also are discussed in Section 9. The knowledge of
physical properties such as flammable limits and flash point are important for
the safe handling and transport of toluene; data on density and solubility may be
necessary for health effect studies.
3.5 CHEMICAL PROPERTIES
Toluene undergoes substitution reactions, either on the aliphatic side
group (-CH,) or on the benzene ring. These substitutions occur exclusively at
the ortho (1,2) and para (1,4) positions marked in the following figure:
Nitration, sulfonation, halogenation, methylation, and chloromethylation
are some examples of substitution reactions. These reactions occur at a rate
between 467 and 2.1 times faster with toluene than with benzene (Cier, 1969).
The methyl group in toluene is susceptible to dealkylation to produce
benzene (Bradsher, 1977).
Thermal
or
Catalytic'
CH,
At one time, the most significant use of toluene was in the production of
benzene by the above reaction (Cier, 1969).
3-3
-------
Toluene undergoes a reversible disproportionation and transalkylation reac-
tion in the presence of a catalyst (Cier, 1969).
^ //-
\(J
Hydrogenation of toluene takes place readily to produce methylcyclohexane
(Cier, 1969).
n
catalyst
The reverse process of dehydrogenation of methylcyclohexane is the princi-
pal mode of toluene manufacture. Methylcyclohexane is found in petroleum frac-
tions, along with other naphthenes (Cier, 1969).
Oxidation of toluene under catalytic conditions yields benzoic acid as a
principal product (Cier, 1969).
n
catalyst
OOH
Chlorination of toluene under actinic light conditions yields methyl sub-
stitution products (Cier, 1969).
hv
Cl
CH2C1
3-4
-------
The hydrolysis of benzalchloride produces benzaldehyde (Gait, 1967).
n
O
The above reaction may have some significance with respect to chlorination
of drinking water. The presence of benzaldehyde and benzoic acid detected in
drinking water (U.S. EPA, 1980) may be due to the oxidation of toluene found in
drinking water.
In the presence of catalysts and in the absence of light, chlorination
produces £- and £-chlorotoluene (Cier, 1969).
O
n
In the vapor phase, toluene is relatively unreactive toward R0? radicals and
0- found in the troposphere. It is, however, relatively more reactive toward OH
radicals. The products of the reaction are normally benzaldehyde and cresols
(Brown e_t al., 1975). This reaction may have significance with respect to the
fate of toluene in the atmosphere and is discussed in detail in Section 6.1.
Toluene forms azeotropes with a number of solvents, including paraffinics,
naphthenics, and alcoholic hydrocarbons. Azeotropes are important in the puri-
fication of toluene, in solvent technology, and in the recovery of toluene from
reaction mixtures (Cier, 1969).
Toluene is marketed principally as nitration grade (1°, boiling range of
1°C), pure commercial grade (2°C), and all other grades. Generally accepted
quality standards for the first two grades are given by the American Society for
3-5
-------
Testing and Materials (Cier, 1969). The actual concentration of toluene is not
stipulated in these specifications. However, the nitration grade (1°) and pure
commercial grade (2°) toluene are of 99.5$ to 100$ and 98.5$ to 99-4$ purity,
respectively (USITC, 1980). All other grades include toluene used as solvent
grade and for blending aviation and motor gasoline. The non-fuel toluene
(solvent grade) is of 90$ to 98.4* purity (USITC, 1980).
Commercial toluene may contain benzene as an impurity. Therefore, all
health effect studies involving toluene should specify the quality of toluene
used for experimentation. If benzene is present in the toluene, it must be
demonstrated that the observed health effects are not wholly or partly due to
benzene. Because of this contamination, it may also be necessary to determine
the amount of benzene released to the environment due to industrial usage of
toluene.
In general, toluene is quite stable in air, and most of the chemical reac-
tions discussed above require specialized conditions. While some of the reac-
tions may have environmental significance, the majority of the chemical reac-
tions discussed above are conducted under conditions of commercial and research
applications.
3-6
-------
4. PRODUCTION, USE, AND RELEASES TO THE ENVIRONMENT
4.1 MANUFACTURING PROCESS TECHNOLOGY
Toluene is produced primarily from three sources: (1) petroleum refining
processes, (2) by-product of styrene production, (3) by-product of coke-oven
operation.
4.1.1 Petroleum Refining Processes
Low levels of toluene are present in crude petroleum. Toluene is, however,
produced principally from petroleum by two processes: (1) catalytic reforming
and (2) pyrolytic cracking.
4.1.1.1 Catalytic Reforming
The largest quantity of toluene produced in the United States is generated
in the catalytic reforming process. The total estimated toluene produced in this
process in 1978 was 3110 million kg. This represented about 87$ of the total
toluene produced in the United States in 1978 (see Table 4-1).
Catalytic reforming involves the catalytic dehydrogenation of selected
petroleum fractions which are rich in naphthenic hydrocarbons to yield a mixture
of aromatics and paraffins. The proportions of aromatics and paraffins in the
reformate depend on the feedstock used and the severity of the reforming opera-
tion (Cier, 1969). At present, reforming operations are geared primarily to
produce a benzene-toluene-xylene (BTX) reformate from which the individual aro-
matics are recovered (Cier, 1969). Toluene is isolated from the reformate by
distillation followed by washing with sulfuric acid and redistillation. Only a
small fraction of catalytic reformate, however, is utilized for isolating
toluene. The unseparated toluene in catalytic reformate is used for gasoline
blending.
4-1
-------
Table 4-1. U.S. Production of Isolated Toluene in 1978 (Slimak, 1980)
Production
Process
Amount
Produced
do5 kg)
Percent
of Total
Catalytic reforming
Pyrolytic cracking
Styrene by-product
Coke oven by-product
TOTAL
3110
324
135
26a
3595
86.5
9
3.8
0.7
100
value does not include toluene obtained from tar distillers.
4-2
-------
4.1.1.2 Pyrolytic Cracking
The second largest quantity of toluene originates from pyrolytic cracking.
Of the total isolated toluene produced in the United States in 1978, approxi-
mately 9$ (324 million kg) was obtained from this source (see Table 4-1).
When heavier hydrocarbons, such as hydrocarbon condensates, naphtha, and
gas oil, are pyrolytically cracked for the manufacture of olefins, pyrolysis
gasoline is produced as a by-product. The amount of pyrolysis gasoline produced
depends on the feedstock and the manufacturing conditions (Mara et al., 1979).
The by-product pyrolysis gasoline contains a high percent of aromatics. Toluene
can be isolated from pyrolysis gasoline by distillation, removal of any olefins
and diolefins, and redistillation. Not all pyrolysis gasoline produced in the
United States is utilized for the production of isolated toluene.
4.1.2 By-Product of Styrene Production
When styrene is produced by the dehydrogenation of ethylbenzene, some
toluene is also synthesized as a by-product. The toluene isolated from the by-
product is not suitable for chemical and solvent use. Therefore, toluene
obtained from this source is used either for gasoline blending or as feed for the
manufacture of benzene by the hydrodealkylation process (Mara j|t ^1., 1979). In
1978, approximately 135 million kg of isolated toluene, which was about 4? of the
total, was obtained from the by-product of styrene production (see Table 4-1).
4.1.3 By-Product of Coke-Oven Operation
The production of coke by the high-temperature carbonization of coal yields
coal-tar and crude light oil as by-products. Both of these by-products contain
some toluene. The production of toluene from distillation of coal-tar is minimal
(Mara j;_t _§!., 1979). Some toluene, however, is isolated from crude light oil.
As shown in Table 4-1, approximately 26 million kg of toluene were isolated from
4-3
-------
coal-derived toluene in the year 1978. This amounted to about 0.7$ of the total
isolated toluene produced during the same year.
4.2 PRODUCERS
Of the total toluene produced in the United States for internal consumption,
only about 11$ is isolated as toluene (see Table 4-2).. The remainder stays in
gasoline as a benzene-toluene-xylene (BTX) mixture. The total amount of toluene
available in the United States in 1978, both isolated and non-isolated, is shown
in Table 4-2.
The identification of isolated toluene producers, their estimated toluene
producing capacity, and the estimated amount of toluene produced in 1978 from
catalytic reforming, pyrolytic cracking, and styrene by-product are shown in
Tables 4-3 through 4-5. The identification of the producers of isolated toluene
from coke-oven by-product is given in Table 4-6. However, the capacity for
isolated toluene production and the actual amount of toluene produced are not
given because the data are unavailable.
During 1979, the production of toluene from coke-oven operators had a
reported increase of 17.6$ over 1978 (USITC, 1980). The production of toluene
from petroleum refiners has been reported to have decreased by 4.3$ during the
same period (USITC, 1980). This caused a net decrease of 4.2$ of the overall
isolated toluene production in 1979 over 1978 (USITC, 1980).
4.3 USERS
As mentioned in Section 4.2, most of the toluene produced as BTX mixture is
never isolated but remains in various refinery streams for use in gasoline.
Isolated toluene, on the other hand, is used for different purposes. The con-
sumption of isolated toluene in different usage is shown in Table 4-7. The
fluctuating but largest single use of isolated toluene is in the production of
benzene through the hydrodealkylation (HDA) process. The fluctuation in the use
4-4
-------
Table 4-2. Isolated and Non-Isolated Toluene Available
in the United States in 1978 (Slimak, 1980)
Source
Isolated
Quantity
(10b kg)
Non-Isolated as BTX
Catalytic reforming
Pyrolytic cracking
Styrene by-product
Coke oven by-product
Imports
Exports
SUBTOTAL
TOTAL
3,110
324
135
26
192
-364
3,^23
27 , 000
197
NAa
96
NRb
27,293
30,716
TIA = not applicable.
NR = not reported.
4-5
-------
Table 4-3. Producers of Isolated Toluene from Catalytic Reforming in 1978
(Slimak, 1980)
Company and Location
Toluene
Capacity
. (10b kg)
Isolated Toluene Produced
(10b kg)
Amerada Hess - St. Croix, VI
American Petrofina - Big Spring, TX
Beaumont, TX
Ashland Oil - Catlettsburg, KY
N. Tonawanda, NY
Arco - Houston, TX
Wilmington, CA
Charter Oil - Houston, TX
Coastal States - Corpus Christi, TX
Commonwealth - Penuelas, PR
Crown - Pasadena, TX
Exxon - Bay town, TX
Getty - Delaware City, DE
El Dorado, KS
Gulf - Alliance, LA
Philadelphia, PA
Port Arthur, TX
Kerr McGee - Corpus Christi, TX
Marathon - Texas City, TX
Mobil - Beaumont, TX
Monsanto - Chocolate Bayou, TX
Pennzoil - Shreveport, LA
Phillips - Sweeney, TX
Guayama, PR
Quintana-Howell - Corpus Christi, TX
Shell - Deer Park, TX
460
164
125
99
39
125
49
39
56
395
46
411
a
20
194
92
49
148
72
280
33
c
33
335
56
197
310
110
84
67
26
84
33
26
38
266
31
277
NAb
13
130
62
33
100
49
189
22
NA
22
226
38
133
4-6
-------
Table 4-3. Producers of Isolated Toluene from Catalytic Reforming in 1978
(Slimak, 1980) (Cont'd)
Company and Location
Toluene
Capaci ty
. (10° kg)
Isolated Toluene Produced
(105 kg)
Sunoco - Corpus Christ! , TX
Marcus Hook, PA
Toledo, OH
Tulsan, OK
Tenneco - Chalmette, LA
Texaco - Port Arthur, TX
Westville, NJ
Union Oil - Lemont, IL
Union Pacific - Corpus Christi, TX
TOTAL
138
151
217
66 •
115
92
132 .
56
99
1613
93
102
166
44
78
62
89
38
67
3108
1980 capacity for this producer was 85 million kg.
DNA = not applicable.
'1980 capacity for this producer was 72 million kg.
4-7
-------
Table 4-4. Producers of Isolated Toluene from Pyrolysis Gasoline
(Slimak, 1980)
Company and Location
Arco - Chanelview, TX
Commonwealth - Penuelas, PR
Dow - Freeport, TX
Gulf - Cedar Bayou, TX
Mobil - Beaumont, TX
Monsanto - Chocolate Bayou, TX
Union Carbide - Taf t, LA
TOTAL
Toluene
Capaci ty
(10° kg)
Isolated Toluene Produced
(105 kg)
105
49
13
66
16
132
66
447
76
36
9.4
48
15
96
48
328.4
4-8
-------
Table 4-5. Producers of Isolated Toluene from Styrene By-Product
(Slimak, 1980)
Company and Location
S tyrene
Capacity
(10° kg)
Isolated Toluene Produced
(10b kg)
American Hoechst - Baton Rouge, LA
Arco - Beaver Valley, PA
Cos-Mar - Carville, LA
Dow - Freeport, TX
Midland, MI
El Paso Natural Gas - Odessa, TX
Gulf - Donaldsville, LA
Monsanto - Texas City, TX
Standard Oil (Indiana) -
Texas City, TX
Sunoco - Corpus Christi, TX
U.S. Steel - Houston, TX
TOTAL
400
100
590
660
140
68
270
680
380
36
54
3400
16
4
24
26
5.5
2.7
11
27
15
1.4
2.2
134.8
4-9
-------
Table U-6. Producers of Isolated Toluene from Coke-Oven Crude Light Oils
(Slimak, 1980)
Plant
Location
Arm co
Ashland Oil
Bethlehem Steel
CF and I
Interlake
Jones and Laughlin
Lone S tar
Republic Steel
U.S. Steel
Middletown, OH
Catlettsburg, KY
N. Tonawanda, NY
Bethlehem, PA
Sparrows P t., MD
Pueblo, CO
Toledo, OH
Aliquippa, PA
Lone Star, PA
Youngs town, OH
Cleveland, OH
Clairton, PA
Geneva, UT
1-10
-------
Table 4-7. Consumption of Isolated and Non-Isolated Toluene in Different Usages
(Revised from Slimak, 1980)
Usage
Amount-Used/ year
(1
-------
of isolated toluene exists because the HDA process is used as an effective means
of balancing supply and demand for benzene (Mara jst al., 1979). The U.S.
producers of benzene through the HDA process, their capacity, and the amount
produced are shown in Table 4-8.
The second largest use of isolated 'toluene is back-blending into gasoline
for increasing the octane ratings. Approximately 1465 million kg of isolated
toluene representing 35.1$ of 1978 consumption were used for gasoline back-
blending.
The third major use of toluene is in solvent applications, with the major
use being in the paint and coatings industry. Significant amounts also are used
in adhesives, inks, Pharmaceuticals, and other formulated products. With the
establishment of federal and state laws limiting the emission of aromatic sol-
vents in the workplace and in the general environment, the demand for toluene as
a solvent declined significantly since 1975 (Mara ^t al., 1979). Identification
of specific users of toluene as a solvent is difficult because the users are too
widespread.
Another major use of isolated toluene is as a raw material in the production
of toluene diisocyanate (TDI), benzyl chloride, benzoic acid, xylene, and vinyl
toluene. Manufacture of phenol, cresols, toluene sulfonic acids, nitrotoluenes,
terephthalic acid, caprolactam, and styrene are some of the other minor uses of
isolated toluene (Mara gt al., 1979). A small amount of isolated toluene
(6.6 million kg, <1$ of total) is used for the manufacture of p-cresol (Slimak,
1980). The latter compound is used primarily for the manufacture of the pesti-
cide 2,6-di-terfr-butyl-p-cresol (BHT). Judging from the percent of toluene used
in the manufacture of BHT, its emission from this source should be considered
insignificant.
4-12
-------
Table 4-8. Consumers of Toluene for the Manufacture of Benzene by HDA Process
(Anderson _et _al., 1980)
Toluene Used Benzene Production Capacity
Company and Location (10 kg) (10 kg)
American Petrofina - Port Arthur, TX
Big Spring, TX
Ashland Oil - Catlettsburg, KY
Coastal States - Corpus Christi, TX
Commonwealth - Penuelas, PR
Crown - Pasadena, TX
Dow - Freeport, TX
Gulf - Alliance, LA
Philadelphia, PA
Monsanto - Alvin, TX
Phillips - Guayam, PR
Quintana-Howell - Corpus Christi, TX
Shell - Odessa, TX
Sunoco - Corpus Christi, TX
Toledo, OH
Tulsa, OK
59
103
91
156
298
59
65
122
52
103
103
191
18
52
163
39
77
130
120
200
380
77
84
160
67
130
130
250
23
67
210
50
TOTAL 1674 2155
4-13
-------
The identification of primary users of toluene as a chemical intermediate,
their production capacity, and the amount produced is shown in Tables 4-9 and 4-
10. It should be pointed out that the amount of isolated toluene used in the.
United States in 1978 (excluding net export) adds up to 4000 million kg according
to Table 4-7. However, Table 4-2 shows that the total amount of toluene avail-
able for internal consumption during the same period (excluding net export) was
only 3600 million kg. This discrepancy is due to the fact that Table 4-7 is based
on data that are only estimates and the data in Table 4-2 are obtained from the
manufacturers who reported their net toluene production to the U.S.
International Trade Commission.
4.4 ENVIRONMENTAL RELEASE
The three primary sources of toluene release or emission to the environment
are from: production, usage, and inadvertent sources.
4.4.1 Emission from Production Sources
Toluene can be released into the environment during its production as pro-
cess losses, fugitive emissions, and storage losses. Process emissions are those
that originate from the reaction and distillation vents deliberately used for
venting gases. Storage emissions originate from losses during loading and
handling of the product used for manufacturing processes and storage of the final
product. Fugitive emissions are those that have their origin in plant equipment
leaks. The air'emission factors used to estimate the total emission of toluene
from different production sources have been obtained from Mara et ^1. (1979) and
the values are given in Table 4-11.
Based on the emission factors indicated in Table 4-11, the amount of toluene
emitted into the atmosphere from the four production sources has been estimated
in Table 4-12. Atmospheric releases of toluene from each source shown in
Table 4-12 are from production of both isolated and non-isolated toluene. It is
4-14
-------
Table 4H?. Producers of Toluene Diisocyanate (TDI) in 1978
(Mara .et al., 1979)
Company and Location
TDI Capacity
(10b kg)
Toluene Used
(105 kg)
Allied Chemical - Moundsville, WV
BASF Wyandotte - Geismar, LA
Dow Chemical - Freeport, TX
Du Pont - Deepwater, NJ
Mobay Chemical - Bay town, TX
New Martinsville, WV
Olin - Astabula, OH
Lake Charles, LA
Rubicon Chemical - Geismar, LA
Union Carbide - S. Charleston, WV
TOTAL
36 '
45
45 -
32
59
45
14
45
18
25
364
20
25
25
17
32
25
7
25
10
13
199
4-15
-------
Table 4-10. Other Toluene Chemical Intermediate Users in 1978
(Mara .et al., 1979 )
Company and Location
Production
Capaci ty
(10b kg)
Toluene Used
(10b kg)
Arco - Houston, TX
Sunoco - Marcus Hook, PA
TOTAL
Kalama - Kalaraa, WA
Monsanto - St. Louis, MO
Velsical - Beaumont, TX
Chattanooga, TN
Pfizer - Terre Haute, IN
Tenneco - Garfield, NJ
TOTAL
Monsanto - Bridgeport, NJ
Sauget, IL
Stauffer - Edison, NJ
UOP - E. Rutherford, NJ
TOTAL
Dow - Midland, MI
Xylene Producers
89
92 .
181
Benzoic Acid Producers
64
5
23
27
3
7
129
Benzyl Chloride Producers
36
36
5
1
78
Vinyl Toluene Producers
27
48
50
98
33
2
12
14
1
3
65
16
16
3
0.5
35.5
25
4-16
-------
Table 4-11. Toluene Air Emission Factors from Production Sources
(Mara et al., 1979)
Emission Factor
(kg lost/kg produced)
Source
Process
S torage
Fugitive
Total
Catalytic reforming
Pyrolytic cracking
Styrene by-product
Coke oven by-product
0.00002
0.00015
0.00001
0.00050
0.00006
0.00060
0.00060
0.00060
0.00002
0.00015
0.00015
0.00015
0.0001
0.0009
0.00076
0.00125
4-17
-------
Table 4-12. Estimated Atmospheric Toluene Emissions from
Four Major Production Sources
Production Source
Total Amount
Produced
(million kg/yr)
Total
Emission
Factor
Total
Emission
(103 kg/yr)
Catalytic reforming - Isolated 3,110
- Non-isolated 27,000
Pyrolytic cracking - Isolated 324
- Non-isolated 197
Styrene by-product 135
Coke oven by-product - Isolated 26
- Non-isolated 96
TOTAL
0.0001
0.0009
0.00076
0.00125
3,011
469
103
153
3,736
4-18
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assumed that the air emission is dependent only on the manufacturing process and
is the same for both isolated and non-isolated toluene from the same process.
The manufacturing processes may lead also to toluene release to other media.
The release of toluene to water from petroleum refineries performing catalytic
reforming and pyrolytic cracking processes is .assumed to be negligible because
the concentration of toluene has been determined to be below the quantification
limit in more than 90$ of discharged water from the refineries (Slimak, 1980).
Coking operations, however, can lead to toluene release in other media. The
wastewaters from coking plants have the following distribution (Slimak, 1980):
Direct discharge: 33$
Publicly Owned Treatment Works (POTW): 25%
Quenching: 40$
Deep well injection: 2%
Two-thirds of the wastewater from the quenching operation is recirculated
and actually not discharged. Therefore, only 73$ of the total wastewater con-
taining toluene is actually discharged to the environment.
The average volume of effluents produced from coke-oven operation (Slimak,
1980), the toluene concentration in these effluents (Slimak, 1980), and the
emission factors in these effluents are given in Table 4-13.
For a total coke production of 44 x 109 kg in 1978 (Slimak, 1980), the total
q _A
amount of toluene discharged in wastewater amounted to 44 x 10 x 4.43 x 10 x
0.73 = 142 x 10^ kg. Some toluene in wastewater may finally enter other media
because of the following reason. Wastewater from the quenching operation is sent
to sumps that generate only solid and gaseous wastes (Slimak, 1980). Therefore,
the distribution of total released toluene in wastewater can be estimated as
given in Table 4-14.
4-19
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Table 4-13. Toluene Emission Factors in Wastewater from
Coke Oven Operation (Slimak, 1980)
Effluent
Waste ammonia liquor
Final cooler blow down
Benzol plant wastes
TOTAL
Liters of Effluent
Produced/kg Coke
Toluene
Cone.
(mg/1)
0.16
0.13
0.20
3.1
17.0
8.6
Emission
Factor
0.496 x 10
2.21 x 10~6
-6
1.72 x 10"
4.1»3 x 10
-6
4-20
-------
Table 4-14. Toluene Released in Different Media from
Coke-Oven Wastewater
Percent of Amount released/yr
Medium Total Released (103 kg)
Air 20 ' 28
Water 33 47
Land 22 ' 31
POTW 25 36
4-21
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4.4.2 Emission from Toluene Usage
The emission of toluene from various usages has been estimated from emission
factors and the amounts used. The values for the emission factors obtained from
Mara .et al. (1979) are shown in Table 4-15.
The atmospheric emission of toluene from its usage in gasoline as non-
isolated BTX and the isolated form (for back-blending) has already been included
in Table 4-12. The emission factor for miscellaneous uses has been assumed to be
the average of other toluene usages excluding its use as solvent. All the
toluene used in paint and coatings has been assumed to be ultimately released to
the atmosphere (Mara et al., 1979). Therefore, an emission factor of 1.0 has
been estimated for this usage. Fifteen percent of the toluene used as a solvent
for adhesives, inks, and Pharmaceuticals is recovered for fuel use (Mara et al.,
1979). The remainder is emitted to the atmosphere. Hence, an emission factor of
0.85 has been assumed for this usage.
Based on the emission factors given in Table 4-15, the estimated toluene
emissions from its various usages are shown in Table 4-16.
It can be concluded from Table 4-16 that, among the different usages of
toluene, the maximum emission occurs from solvent application.
The released toluene from the different user sources shown in Table 4-16 has
been assumed to enter only one medium, air. The use of toluene as a solvent,
however, has been found to produce toluene in wastewater (Slimak, 1980).
Table 4-17 shows the total estimated release of toluene to aqueous media from its
use as a solvent in different industries.
4.4.3 Emission from Inadvertent Sources
Because gasoline consumes a vast amount of total toluene produced (see
Table 4-7), this use constitutes the largest source of environmental emission of
toluene. The emission of toluene from its use in gasoline can occur from three
4-22
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Table 4-15. Toluene Emission Factors for Its Usages
(Mara _et al., 1979)
Emission Factor
(kg lost/ kg used)
Usage
Process
S torage
Fugitive
Total
Benzene production
Solvent for paint
and coatings
Solvent for adhesives,
ink, Pharmaceuticals,
and others
Toluene diisocyanate
Xylene production
Benzoic acid
Benzyl chloride
Vinyl toluene
Miscellaneous
0.00005
NAa
NA
0.00077
0.00005
0.00100
0.00055
0.00055
NA
0.00010
NA
NA
0.00032
0.00010
0.00040
0.00030
0.00030
NA
0.00005
NA
NA
0.00019
0.00005
0.00010
0.00015
0.00015
NA
0.00020
1.0
0.85
0.00128
0.00020
0.00150
0.00100
0.00100
0.00100
NA = not applicable.
4-23
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Table 4-16. Estimated Toluene Emission from Different Uses
Source
Amount Used/yr
(10b kg)
• Emission
Factor
Total Emission/yr
(10J kg)
Benzene production
Solvent for paint and
coatings
Solvent for adhesives, inks,
Pharmaceuticals, and
others
Toluene diisocyanate
Xylene production
Benzoic acid
Benzyl chloride
Vinyl toluene
Miscellaneous others
TOTAL
1675
263
132
200
98
65
36
25
39
2533
0.0002
1.0
0.85
0.00128
0.0002
0.00150
0.0010
0.0010
0.0010
335
263,000
112,000
256
20
98
36
25
39
375,809
-------
Table 4-17. Toluene Released in Aqueous Media from Use as a Solvent
in Various Industries (Slimak, 1980)
Toluene Cone.
in
Waste water
Source (ug/fc)
Waste water
Discharged
Percent (10° i/d)
Occurrence
Amount of
Toluene
Released
(103 kg/yr)a
Ink formulating
Textile products
Gum and wood chemicals
Paint formulating
Leather tanning
Pharmaceutical s
TOTAL
1600
14
2000
990
78
515
8? 0.092
46 - 2000
78 0.11
87 2.8
25 200
62 250
0.038
3.8
0.17
0.72
1.2
24
29.9
T)ased on 300 operating d/yr.
4-25
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distinct sources: evaporation from its use in the automobile, evaporation from
marketing activities (handling and transfer of bulk quantities), and emission
from automobile exhaust.
Other inadvertent sources of toluene emissions into the environment include
transportation, spills into surface water and. land, other manufacturing pro-
cesses that do not attempt to produce toluene, different combustion sources, and
cigarette smoke. The inadvertent release of toluene from other manufacturing
processes occurs primarily from feedstock contamination, by-product formation,
and the use of oil. An example of the latter source is in the manufacture of
acrylonitrile in which wastewater ponds are covered with oil to control the
release of volatile organ!cs.
The release of toluene into different media from various inadvertent
sources is shown in Table 4-18. Because of the volatility of toluene, intermedia
transfers of the compound will possibly change the emission values given in
Table 4-18.
4.4.4 Sum of Emissions from All Sources
The emissions of toluene into different media from all sources are given in
Table 4-19. The estimates also include toluene emission from coke production
which remains unrecovered. The emission of toluene from coke oven operation is
based on an emission factor of 0.00024 (Mara^_t^l., 1979) and an estimated coke
production of 44 x 109 kg (Slimak, 1980) for the year 1978.
It is evident from Table 4-19 that the toluene released into the environment
predominantly enters one medium, the atmosphere. The three largest sources of
toluene emission in descending order are auto exhaust, solvent use, and evapora-
tive loss from automobile and service stations. A large amount of toluene from
land and water spills is also likely to enter air as a result of evaporation. The
large figure for the combined release of toluene into the atmosphere explains the
4-26
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Table 4-18. Toluene Emission from Different Inadvertent Sources
(Slimak, 1980)
Environmental Release
(103 kg/yr)
Source
Air
Water Land
Gasoline marketing
Automobile gasoline evaporation3
Automobile exhaust3
19,000
18,000
640,000
___ ___
—
_ — —
Transportation spills:
Oil
Gasoline
Toluene
Propylene oxide manufacture
Polychloroprene manufacture
Ethylene-propylene rubber manufacture
Ethylene-propylene terpolymer
production
Wood preserving industry
Insulation board manufacture
Hardboard manufacture
Acrylonitrile manufacture
Combustion processes:
36
460
90
4,200
59
400
680
2.2
5.6
230
11
6.3
neg.
neg.
Coal refuse piles
Stationary fuel combustion
Forest fires
Agricultural burning
Structural fires
Cigarette smoke
0 thers
TOTAL
4,400
13,000
7,000
1,000
< 1 , 000
53
8
708 , 306
—
—
— —
— —
— —
— —
1 , 089 247
According to the estimates of McGinnity (1981), the yearly vehicular toluen
emission amounts to 820,000 x 10 kg.
4-27
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Table 4-19. Total Yearly Release of Toluene into Different Media
Environmental Release
(103 kg/yr)
Source
Air
Water
Land
POTW
Production
Usage
Inadvertent
Coke production
TOTAL
3,764
375,809
708 , 306
10,560
1,098,439
47
30
1,089
NA
1,166
31
NAa
24?
NA
278
36
NA
NA
NA
36
NA = not available.
4-28
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reason for its presence as the arcana tic hydrocarbon of highest concentration in
the ambient atmosphere (see Chapter 7).
4.5 USE OF TOLUENE IN CONSUMER PRODUCTS
The consumer products shown in Table 4-20 may contain some toluene. The
percent of toluene in these products also is indicated in the same table. The
emission of toluene into the environment from this source is already included
under Section 4.4.2.
Information available through the Food and Drug Administration (FDA)
(Bolger, 1981) shows the following: of the 19,500 cosmetic products registered
with the FDA through August 14, 1979, 664 products contain varying percents of
toluene. One of the products contains more than 50% toluene, 166 products
contain 25-50$ toluene, 492 products contain 10-25$ toluene, 1 product contains
1-5$ toluene, and 4 products contain 0.1$ or less toluene. The use of toluene is
related to nail base coats, nail enamel, nail polish removers, and other manicure
products.
4-29
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Table 4-20. Consumer Product Formulations Containing Toluene
(Gleason et al., 1969)
Product
Percent Toluene Content
China cement, solvent type
Contact rubber cement
Microfilm cement, cotton base
Model cement
Plastic cement, polystyrene
Shoe cement
Tire repair, bonding compounds
Paint brush cleaners
Stain, spot, lipstick, rust removers
Nail polish
De-icers, fuel antifreeze
Fabric dyes
Indelible inks
Marking inks
Stencil inks
Solvents and thinners
20 to 30
may contain toluene
27 to 30
up to 20 to 25
24
may contain toluene
> 80
contain 25 to 90 BTX
may contain toluene
35
30
<, 60
may contain toluene
80 to 90
40 to 60
may contain toluene
4-30
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5. ABATEMENT PRACTICES IN INDUSTRY
The four major potential sources of toluene release to the environment, in
order of importance (see Section 5.4.4), are (1) inadvertent sources, such as
vehicular emissions and losses during gasoline transfer, (2) solvent use in
paint, coating adhesives, and inks, (3) coke production, and (4) manufacturing
sites such as petroleum refineries and chemical plants. Therefore, institution
of pollution control devices for these four major industries can be expected to
produce a large impact on the overall toluene level in the environment.
5.1 ABATEMENT PRACTICES FOR INADVERTENT SOURCES '
The two major sources of vehicular emissions of toluene in the atmosphere
are exhaust emissions and evaporative emissions from the gas tank and the car-
buretor. Crankcase emissions have been essentially eliminated through the use of
positive crankcase ventilation technologies (U.S. EPA, 1980b).
The installation of catalytic converters on automobiles has resulted in
significant reduction of hydrocarbon emissions from automobiles. Generally,
tailpipe catalysts control systems remove unsaturated and aromatic hydrocarbons,
including toluene, more efficiently than paraffinic hydrocarbons (U.S. EPA,
1980b). Therefore, both the photochemical reactivity and the mass of hydro-
carbons emitted are reduced by the catalytic converter systems.
Evaporative emissions from automobiles have been reduced through the use of
adsorption regeneration carbon canister technologies (U.S. EPA, 1980b). Such
systems are, however, more effective for regular grade gasoline containing 25$ to
21% arcroatics than for premium grade unleaded gasoline containing 43$ aromatics
(U.S. EPA, 1980b).
5-1
-------
Most of the current diesel exhaust emission studies are concerned with
emission controls through either engine design or the use of fuel additives.
Other control options, such as catalytic reactors, appear to be viable.
Other major sources of automobile emissions are losses from spilled gaso-
line and losses during fuel transfer. The former can be reduced by educating the
public about the necessity of restricting spillage both for economic and environ-
mental reasons. The loss of gasoline during fuel transfer is already controlled
in most areas of the country by incorporating vapor recovery systems.
5.2 ABATEMENT PRACTICES FOR SOLVENT USAGE
Solvent vapors originating from industrial usage of toluene in coatings and
thinners can be controlled or recovered by the application of condensation,
compression, adsorption, or combustion principles. Control efficiencies of 90$
or greater are possible by activated carbon adsorption provided participates are
removed from the contaminated airstream by filtration before the airstream
enters the carbon bed (U.S. EPA, 1980b).
When recovery of the vapor is not desired, an incineration method can be
used for controlling emissions. The choice between direct flame and catalytic
incineration methods must be based on economic factors and on local emission
standards.
Control of toluene emissions from gravure printing can be done in a number
of ways (U.S. EPA, 1980b). Process modifications involving microwave, infrared,
electron beam, or ultraviolet drying and subsequent recovery of organic vapors
will reduce emissions from organic vapors. Another alternative is to replace
inks containing organic solvents with aqueous or solventless inks. Incineration
of the exhaust gases by thermal or catalytic methods provides another method of
emission control. Last, solvent vapors can be adsorbed in activated carbon as a
method of controlling toluene vapor emissions into the atmosphere.
5-2
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5.3 ABATEMENT FOR COKE OVEN EMISSIONS
Hydrocarbon emissions result from the burning of the stripped coke oven gas
for the under-firing of the coke batteries. The combustion exhaust gases from
each oven are combined together and vented through a common stack. Improvement
of combustion efficiency of the coke batteries wauld.be a proper method of
control (U.S. EPA, 1Q80b).
5.4 ABATEMENT FOR EMISSIONS FROM MANUFACTURING SITES
Current technology for the control of gaseous hydrocarbon emissions from
manufacturing sites takes the form of charcoal adsorption, direct flame or cata-
lytic incineration, chemical sorbents, vapor condensation, process and material
change, and improved maintenance (U.S. EPA, 1980b). The feasibility of sorbing
organics by the wet scrubbing method using selected aqueous surfactant systems as
opposed to plain water has been demonstrated (Matunas _et jd., 1978). Organic
removal as high as 90$ to 95$ can be attained by utilizing this method. Conden-
sation of organics by the removal of heat may be an expensive method since
refrigeration must be used for the removal of heat from gases (Matunas et al.,
1978).
5.5 ABATEMENT PRACTICES FOR RAW AND FINISHED WATERS
No information could be found on this subject. Treatment of water with
activated carbon, however, is expected to remove toluene from drinking waters.
5.6 ECONOMIC BENEFITS OF CONTROLLING TOLUENE EMISSIONS
There is no significant geographical area in the United States in which
ambient concentrations of alkylbenzenes are known to be harmful to plants or
animal lives (NRC, 1980); however, as reactive hydrocarbons, they can contribute
to the formation of photo-chemical smog that is known to be harmful to life and
property. B rooks hi re et _al. (1979) selected residential properties in six pairs
of selected neighborhoods and found the property value could increase on the
5.-3
-------
average of $504 annually if the air quality were improved. The authors ascribed
about one-half of the enhanced value to respondent-perceived aesthetic benefits
(visibility) and the other half to perceived health benefits. Thayer and Schulz
(1980) extrapolated the results of Brooks hire _et jd. (1979) to the entire south
coast air basin of California and concluded that the urban benefits from improved
air quality amounted to between $1.6 billion and $3 billion in the basin. The
benefits that an improved air quality would provide for commercial agriculture in
southern California can be added to the urban benefits described above. Adams
e_t _§!. (1980) examined the economic impact of ambient oxidants upon 14 selected
crops in the region. They extrapolated their results of these 14 crops to all
southern California commercial agricultural products and predicted a
$250 million benefit to be derived from control of oxidants in the air.
All of the cost benefits discussed above are based on total pollutants in
air. It is not possible to project the portion of these benefits that may be
attributable to control of toluene pollution alone. For a detailed description
of the cost benefits of controlling alkylbenzene pollution, interested readers
are referred to a recent NRC (1980) document.
5-4
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6. ENVIRONMENTAL FATE, TRANSPORT, AND PERSISTENCE
The environmental fate, transport, and transformation of toluene in three
different media—air, water, and soil are individually discussed below.
6.1 AIR
6.1.1 Fate in Air
Toluene can be persistent in the atmosphere. It is, therefore, a prime
candidate for short- and long-range transport away from urban emission sources.
The dispersion of toluene from a point source to the ambient atmosphere can be
theoretically modeled by using dispersion equations. One such modeling method
has been used in the Integrated Exposure Analysis Section (Section 10) to deter-
mine the transport characteristics of toluene.
The atmospheric toluene concentration downwind from one of the largest U.S.
automobile manufacturing plants was measured by Sexton and Westburg (1980). At a
point 6 km from the plant site, the toluene concentration was found to be
20.5 ppb. The concentration of toluene was still 15.1 ppb at a point 18 km
downwind.
The primary mode of toluene removal from the atmosphere is probably via
photochemical reactions, which occur during the course of its transport. Toluene
itself does not absorb light at wavelengths longer than 295 nm. The solar
spectrum in the troposphere does not contain much light of wavelengths shorter
than 295 nm. Therefore, toluene can absorb only insignificant amounts of sun-
light in the lower atmosphere, but a charge-transfer complex between toluene and
molecular oxygen absorbs light of wavelengths to at least 350 nm. According to
Wei and Adelman (1969), it is the photolysis of this complex that may be respon-
sible for some of the observed photochemical reactions of toluene.
Toluene is apparently removed from the atmosphere entirely through free
radical chain processes (NRC, 1980). Of the free radicals in the atmosphere,
6-1
-------
hydroxy (*OH), atomic oxygen (0), and peroxy (*H02 or *ROp, where R is an alkyl
or acyl group) radicals are potential initiators for the removal of toluene. An
additional reactive species is ozone. The rate constants for the reaction of
these species with toluene and their relative significance for toluene removal
are given in Table 6-1.
It is obvious from Table 6-1 that reactions with hydroxy radicals are the
most important processes for the removal of toluene from the atmosphere. Based
upon an estimated daytime hydroxy concentration given in Table 6-1 and a rate
constant for the reaction of »OH radicals with toluene of 5.5
x 10~ cnr mol" sec~ (Atkinson et al., 1978), the chemical lifetime of toluene
in daylight hours has been estimated to be 50 hours (NRC, 1980). This value is
subject to considerable uncertainty and may vary on a day-to-day basis by as
much as an order of magnitude depending on solar intensity, temperature, and
local trace gas composition of the atmosphere.
The reaction products formed from toluene under simulated atmospheric con-
ditions are not known with certainty. According to the study of O'Brien et al.
(1979), the gaseous products of the reaction are £-cresol, m- and £-nitrotoluene,
benzyl nitrate, and benzaldehyde. Of these products, £-cresol and benzaldehyde
are the major components, each composing about 8% of the total product yield.
The mechanisms by which these products are formed are shown in Figure 6-1.
It is obvious that the reaction proceeds via addition of *OH radicals to the
ring or by abstraction of hydrogen from the methyl side chain. Several investi-
gators have determined the relative importance of both reaction pathways. From
the amounts of reaction products formed, it was determined that the addition
mechanism is of much greater significance than the abstraction mechanism (Kenley
etal., 1978; O'Brien et al., 1979; Hoshino et al., 1978).
6-2
-------
Table 6-1. Rate Constants for Reactions of Toluene with Reactive Species
in the Atmosphere3 (NRC, 1980)
Estimated Average Rate of
Daytime Annual Toluene
Concentration Rate Constant, Removal, Fraction of
Species ppm ppm~ min" - ppm/min Hydroxyl Rate
Hydroxyl <.
radical 4 x 10"°
A tomic
oxygen 3 x 10~'
Peroxy a
radical 1 x 10
_2
Ozone 3 x 10
9.5 x 103 3.7 x 10~4 1
1.1 x 102 3.3 x 10~7 10~3
2.5 x 10~7 2.5 x 10~11 4 x 10~8
5 x 10~7 1.5 x ID"8 5 x 10~5
Modified from Hendry, 1979.
6-3
-------
CH,
CH,
•OH
addition __
OH
•OH
NO,
CHn
CIL
CH,
OH
OH
—NO,
H
CH-
CH,
.OH abstraction^
** L
CH-0
NO
CHO
Figure 6-1. Proposed Reaction Pathways of Toluene Under Atmospheric
Conditions (NRC, 1980)
6-4
-------
Other reaction products are also formed from toluene reactions under simu-
lated atmospheric conditions. Some of the ring fragmentation products formed are
acetylene, acetaldehyde, and acetone. The total yield of these products is much
less than 1$. Formaldehyde and formic acid are also formed, but their yields are
not known. A measurement of the total gas phase carbon showed that 60% of the
oxidation products from the photodecomposition of toluene left the gas phase and
deposited on the walls of the reaction vessel or formed an aerosol (NRC, 1980).
The distribution of the products between gas and condensed phases (aerosol) in
the open atmosphere is still not clear.
In addition to the above photooxidation products, photolysis of toluene in
polluted atmospheres (containing NO ) yields ozone and fairly high amounts of
X
peroxyacetylnitrate (PAN) (5% to 30$ nitrogen yield) and peroxybenzoylnitrate
(PBzN) (0% to 5% nitrogen yield) (NRC, 1980). The mechanism of PAN formation is
either by the fragmentation of the aromatic ring or by the secondary reactions
involving products of toluene photolysis. PBzN is formed by the photooxidation
of benzaldehyde produced from the photooxidation of toluene (NRC, 1980). The
formation of the peroxy compounds is significant because these products are
strong eye irritants, oxidizing agents, and may induce plant damage (NRC, 1980).
For an excellent review of the photochemical fate of toluene in the atmosphere,
the reader is referred to a recent NRC document (NRC, 1980).
6.1.2 Transport
The volatility of toluene and its low solubility in water permit it to
volatilize from water surfaces to the atmosphere (MacKay and Wolkoff, 1973).
Studies of actual and simulated oil spills in seawater indicate that virtually
all hydrocarbons smaller than C1(- will be lost to the atmosphere within a few
days (McAuliffe, 1977). The reverse process, that is, transfer of toluene from
air to hydrosphere through rain, is also known to occur (Walker, 1976); however,
6-5
-------
washout should not be considered to be a significant removal process for toluene
from air (NRC, 1980).
6.2 AQUATIC MEDIA
6.2.1 Fate
Sauer et al. (1978) concluded from their studies of the coastal waters of
the Gulf of Mexico that toluene and other alkylbenzenes are persistent in the
marine environment. The probable modes of toluene loss or transformation from
the aquatic environment are discussed below.
Oxidation: Reaction of toluene in water with hydroxy radicals generated
from the irradiation of hydrogen peroxide produces benzaldehyde, benzyl alcohol,
and cresols (Jefcoate £t jd., 1969). No data were found in the literature from
which a relevant rate of oxidation of toluene in the aquatic environment could be
determined.
It has been observed (Carlson et al., 1975) that toluene may form small
amounts of chlorine-substituted products during chlorination under conditions
used for water renovation. The extent of chlorination increases with the
decrease of pH and increase of contact time. At a water temperature of 25°C and a
_a
chlorine concentration of 7 x 10 M, the percent chlorine uptake was determined
to be 11.1$ and 2.9$ at water pH of 3 and 7, respectively (Carlson e_t _al., 1975).
With other conditions remaining the same, no chlorine uptake was observed at
water pH of 10.1.
Hydrolysis: No data have been found that would support any role of hydroly-
sis in the fate of toluene in the aquatic medium.
Bioaccumulation: No measured steady-state bioconcentration factor (BCF) is
available for toluene but, using the equation of Veith jet al. (1979) and the
measured octanol-water partition coefficient (as opposed to the theoretical
value for log BCF of 2.69 [Chiou et al., 1977]), the U.S. EPA (1980b) has
6-6
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estimated the BCF as 27.1. A factor of 3-0/7.6 = 0.395 has been used to adjust
the estimated BCF from the 7.6% lipids on which the Veith^t_al. (1979) equation
is based to the 3$ lipids that is the weighted average for consumed fish and
shellfish in the United States. Thus, the weighted average BCF for toluene from
edible aquatic organisms consumed by Americans has been calculated to be 27.1
x 0.395 = 10.7.
In one experiment (Roubal _et jd., 1978), coho salmon (Oncorhynchus kisutch)
and starry flounder (Platichthys stellatus) were exposed to a soluble fraction of
a crude oil containing aromatic hydrocarbon in a flowing seawater. It was found
that alkylated aroma tics accumulated in tissues to a greater degree than unsub-
stituted derivatives. In both species, accumulations of substituted benzenes
increased with increased alkylation. The tissues were not analyzed for toluene
because of inadequate analytical procedures. It was, however, determined that
the bioconcentration factors in starry flounder for C^ and C_ substituted ben-
zenes were as high as 2600 and as low as near zero (concentration in fish tissue
was below detection limit of 0.05 ppm) for xylenes. Substantial variations in
BCF for individual hydrocarbons were found in both species. The muscle of coho
salmon, which has a higher lipid content than starry flounder, showed a lower
BCF. It was concluded (Roubal _et al., 1978) that factors other than lipid
content were more important in the observed species differences in the BCF
values.
6.2.2 Transport
The primary fate-determining processes of toluene in aqueous media appear
to be its intermedia transport processes (U.S. EPA, 1979). The details of the
transport processes are discussed below.
Water to Air: Although there are no experimentally determined evaporation
rates of toluene from water, there are theoretical models available for
6-7
-------
predicting the rate of evaporation of slightly-soluble materials from aqueous
solution (Mackay and Wolkoff, 1973; Liss and Slater, 1974; Mackay and Leinonen,
1975; Dilling, 1977). The most accurate of these is based on the mass transfer
coefficients for the liquid and vapor phases reported by Liss and Slater (1974)
and the Henry's law constant (the equilibrium concentration of a solute in air
divided by its concentration in water for a solute as calculated by its solu-
bility, vapor pressure, and molecular weight (Mackay and Leinonen, 1975). Based
on these, Mackay and Leinonen (1975) reported the" calculated evaporation half-
life for toluene from 1-m deep water to be 5.18 hours.
The intramedia transfer of toluene in water can be calculated from this
half-life value. If the t1/2 and the current velocity are assumed to be
5.18 hours and 1 m/sec, respectively, the distance downstream that water in a
river would flow before the volatilization of 50$ toluene is:
5.18 hour x 1 m/sec x 3600 sec/hour = 18,648 m
Similarly, Henry's law coefficient (H) can be used to determine toluene
concentration in air phase over seawater. If the height of the air and water
columns are assumed to be the same, the Henry's law coefficient can be given as:
[ toluene]
H = m T^ = 0.349 for seawater (NRC, 1980)
[toluenej.j.
Thus, if equilibrium were attained, only 26$ of toluene would be present in the
gas phase above seawater.
In shallow or deep waters where stratification occurs, it is likely that the
atmospheric mixing layer is 10 to 100 times deeper than the aquatic mixing layer
(NRC, 1980). In such water, 78$ or 97$, respectively, of the toluene would exist
in the gas phase.
Water to Soil: The importance of this transport process can be evaluated by
experimentally determining the toluene content in sediments of surface water
6-8
-------
contaminated with toluene. Theoretical modeling can also be used for this
purpose. Using the U.S. EPA's multi-compartment Exposure Analysis Modeling
System (EXAMS), ADL (1980) has determined that bottom sediments account for over
90/t of the total toluene discharged into surface waters under steady-state con-
ditions. The values for the distribution of toluene between surface water and
sediment as determined by the EXAMS modeling do not agree with experimental
results of Jungclaus ^Jt al. (1978). Jungclaus et al. (1978) determined the
toluene content in the water and sediments of a river receiving wastewater
containing toluene. Although many other compounds were found to accumulate in
the sediments, toluene was not one of these compounds. More research in this
area is needed to explain this discrepancy between the EXAMS modeling and the
experimental results.
6.3 SOIL
6.3.1 Fate
Toluene probably exists in soils in the sorbed state. The sorption of
toluene by clay minerals (bentonite and kaolinite) was studied by El-Dib e_t al.
(1978) and was found to follow Freundlich1s adsorption isotherm. These authors
also found that the adsorption capacity increased as the pH value decreased.
The fate of toluene in soil has not been thoroughly investigated. It can,
however, be anticipated that a part of toluene in soil will undergo intermedia
transfer to air and water, and a part will undergo intramedia transfer. The part
that stays in soil may participate in chemical reactions (including photo-
chemical reactions) and biological degradation and transformation. The relative
importance of intermedia transfer and chemical and biological reactions of
toluene in soils is not accurately known.
Investigations of Wilson _et _al. (1980) indicate that volatilization, bio-
degradation, and biotransformation processes dominate the fate of toluene in
6-9
-------
soils. The intermedia transfer of toluene from soil to water is probably not an
important pathway. No data could be found in the existing literature searched
that would support any role of chemical reactions in determining the fate of
toluene in soils. The intermedia transport of toluene and its biological fate in
soils have been separately discussed below.
6.3.2 Transport
6.3.2.1 Soil to Air
Laboratory experiments of Wilson et al. (1980) show that U0$ to 80$ of
toluene applied to the surface of sandy soils will volatilize to air. The
volatilization rate is dependent on the nature of" soil. The volatilization rate
may be significantly lower for soils with high organic contents due to their
sorption properties (ADL, 1980). This phenomenon may be especially important
with municipal sludges that normally contain high organic substances.
6.3-2.2 Soil to Water
The transfer of toluene from soil to ground or surface waters can be of
importance with regard to the possibility of contamination of these water bodies
and their subsequent use as sources of drinking waters. Unfortunately, very
little information is available on this subject. From the investigations of
Wilson _et _al. (1980), it can be concluded that the transport of toluene from soil
to water is probably not a major transfer pathway. These investigators showed
that 0% to 20$ of the applied toluene on a sandy soil system could be elicited
through a column of 140-cm height. The leaching of toluene from landfill sites
that contain soil originated partly from municipal sludges can be expected to be
even lower. The higher organic content of these soils may retard the aqueous
elution process due to higher sorption properties of the soils toward toluene.
6-10
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6.4 ENVIRONMENTAL PERSISTENCE
6.4.1 Biodegradation and Biotransformation
6.4.1.1 Mixed Cultures
The study of the disappearance of toluene in soil began nearly 75 years ago.
Stormer (1908) and Wagner (1914) showed that toluene was susceptible to bacterial
decomposition in the soil; Gray and Thornton (1928) and Tausson (1929) isolated
soil bacteria that utilized toluene as a sole carbon source. Glaus and Walker
(1964) found that the half-life of toluene in soil inhabited with toluene-
degrading bacteria was 20 to 60 minutes. Wilson et al. (1980) indicated that
from 20 to 60$ of toluene eluted through 140 cm of sandy soil biodegraded. The
authors stated that the process was probably very sensitive to the soil type and
therefore may or may not be an important removal process of toluene from a
particular soil system.
More literature, however, exists on the biodegradation of toluene in aqua-
tic environments. In a report prepared by the Arthur D. Little Company (1981),
the biodegradation of toluene in lakes, rivers, and ponds was discussed using the
U.S. Environmental Protection Agency's (U.S. EPA) Multicompartment Exposure
Analysis Modeling System (EXAMS). The report stated that the biodegradation of
toluene accounted for 0.31, 4.81, 0.36, 0.09, and 18.47$ of the total toluene
loss in oligotrophic lakes, eutrophic lakes, clean rivers, turbid rivers, and
ponds, respectively. Sontheimer (1980) also reported the rate of toluene
disappearance from Rhine River water but did not specify the rate of
disappearance. Using the standard dilution method and filtered wastewater
effluent as the seed to determine the biochemical oxygen demand (BOD), the
biodegradability (percentage bio-oxidized) of toluene ranged from 63 to 86$
after up to 20 days (Price jet al., 1974; Bridie _et al., 1979).
6-11
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Matsui jst _al. (1975) found, that in activated sludge acclimated to various
organic compounds, the total organic carbon (TOO removal efficiency for toluene
was 60$ while the chemical oxygen demand (COD) was 72$ for 24 hours. The authors
concluded, however, that although toluene was a readily biodegradable compound,
in this experiment disappearance was mainly due to evaporation. Using the
Warburg technique, Lutin et _al. (1965) reported a 40$ degradation of toluene in
activated sludge after 144 hours. In comparison, 63$ of the benzene was degraded
in the same time. The degradation of toluene in benzene-acclimated activated
sludge reached 17.2$ of the theoretical BOD after 6 hours and 48$ after 192 hours
(Malaney and McKinney, 1966). Toluene was the most biodegradable of a number of
alkylbenzenes tested by these authors, who also found that the introduction of a
methyl group to benzene retarded the initial (6 hour) rate of oxidation of
toluene but not the extent of degradation compared to benzene. Marion and
Malaney (1964) exposed activated sludge to 500 mg/1 of toluene from three munici-
pal plants and reported that unacclimated sludge showed little ability to oxidize
benzene and toluene after 6 hours and that after 72 hours, less than 11$ oxida-
tion had taken place (compared to 44.7$ reported by Malaney and McKinney, 1966).
However, one sludge sample acclimated to benzene oxidized greater than 30$ of the
toluene after 180 hours.
The degradation of toluene has also been studied in mixed cultures of
bacteria. Chambers j!_t jl. (1963), using phenol-adapted bacteria, reported 38$
degradation of toluene after 180 minutes. In another study, Declev and Damyanova
(1977) grew sludge cultures in either phenol, xylene, or toluene as the sole
carbon source and found that phenol-adapted bacteria proved less able to degrade
xylene and toluene, while toluene-adapted cells showed greater versatility in
being able to oxidize phenol and xylene.
6-12
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6.4.1.2 Pure Cultures
Fungi and bacteria have been shown to utilize toluene (Smith and Rosazza,
1974). In the course of studying the effects of toluene on microbial activity,
Kaplan and Hartenstein (1979) discovered that 6 of 7 fungi imperfecti, 7 of 13
basidiomycetes, and 6 of 14 bacteria grew with 0.1.or 0.05$ toluene as the sole
carbon source. The addition of yeast extract increased the amount of toluene-
utilizing microorganisms. In contrast, no oil-utilizing or hydrocarbon-
degrading fungi grew on toluene as the sole carbon source (Davies and Westlake,
1979). Using an oxygen electrode to measure oxidation, Buswell and Jurtshuk
(1969) found that resting cells of an ji-octane-utilizing Corynebacterium sp.
oxidized only 1% of the available toluene compared to 100$ oxidation of ji-octane.
Toluene did not serve as a growth substrate in this experiment. Kapraleck (1954)
isolated a Pseudomonas-type bacteria from the soil of a petroleum deposit that
utilized toluene. Pseudomonas and Achromobacter spp. from soil used toluene as
the sole carbon source for growth (Glaus and Walker, 1964; Gibson and Yeh, 1973).
Smith and Rosazza (1974) reported that bacteria and yeast hydroxylated toluene.
In contrast, Nei et al. (1973) found little oxidation of toluene by phenol-
utilizing yeast.
The metabolic pathway for the bacterial oxidation of toluene has been
studied with soil microorganisms (Figure 6-2) and reviewed by Gibson (1971) and
Subramanian et al. (1978). On the basis of simultaneous adaptation studies,
Kitagawa (1956) concluded that Pseudomonas aeruginosa oxidized toluene via
/
benzyl alcohol and benzaldehyde to benzoic acid and then to catechol. This
pathway was supported by the investigations of Nozaka and Kusunose (1968). A
Mycobacterium sp. also produced benzoic acid from toluene (Atkinson and Newth,
1968), as did a methanetrophic bacterium (Methylosinus trichosporium) (Higgins
£tal., 1980).
6-13
-------
CH,
X
o
TOLUENE
O Q?
BENZYL ALCOHOL £ij-2. 3-DH-2. 3-DOHTOL
! 1
CHO CH, CH,
6 QC
* Lj=°OH
BENZALOEHYOE 3-METHVLCATECHOL OH
1 / METHYLHYDROXYMUCONIC
1 / SEMIALOEHYDE
COOH «» I
(Q) ^sf°°" »>
BENZOICACID METHYLMUCONIC |" fOOH
1 AC|'° \AoH
y I 2-OH-6-OXO-2,tiI-4.ci|-HA
11 1
f
CATECHOL
/ \
^COOH f^HO
L^ COOH L^ COOH
MUCONIC ACID OH
HVDROXYMUCONIC
SEMIALDEHYDE
1 1
1
ACETATE
PYRUVATE
Figure 6-2. Microbial Metabolism of Toluene (prepared by Syracuse
Research Corporation)
5-14
-------
An alternative pathway was proposed by Glaus and Walker (196M) using a
Pseudomonas sp. and an Achromobacter sp. isolated from soil that used toluene as
a sole carbon source for growth. These investigators found that washed cell
suspensions oxidized toluene to 3-methylcatechol, indicating that the methyl
moiety was not oxidized, as occurred in the pathway proposed by Kitagawa (1956).
A similar oxidation product was found by Nozaka and Kustnose (1969) using
Pseudomonas mildenbergii cell-free extracts. Gibson et al. (1968a) also
reported the detection of 3-methylcatechol from toluene by Pseudomonas putida.
An oxidation product preceding 3-methylcatechol was found in cultures of a mutant
strain of P. putida (strain 39/D) (Gibson et al., -1968b, 1970). This new product
was identified as (+)-ci3-2,3-dihydroxy-1-methylcyclohexa-it. 6-diene (cis-2,3-
dihydro-2,3-dihydroxytoluene) ( cis-2,3-DH-2,3-DOH TOL) (Kobal et al., 1973).
The catechol and 3-methylcatechol can be then cleaved by ortho cleavage to yield
the corresponding muconic acids or by meta cleavage to yield the corresponding
hydroxymuconic semialdehydes (Bayly et al., 1966). Methylmuconic acid was
formed from toluene oxidation by a soil bacterium Nocardia corallina (Jamison
jet jl., 1969). The semialdehydes are further converted to 2-hydroxy-6-oxo-
2,cis-U,cis-heptadienoic acid (2-OH-6-OXO-2.cis-U.cis-HA) and then to acetate,
pyruvate, and acetalydehyde and to CO and energy (Bayley et al., 1966). The
conversion of toluene to compounds that can be utilized as sources of carbon and
energy suggests that toluene will be degraded rapidly by microbial species pro-
liferating at the expense of the compound and will not accumulate significantly
in the environment.
The enzymes responsible for toluene degradation are carried on plasmids
(Williams and Worsey, 1976; Saunders, 1977). Williams and Worsey (1976) isolated
13 bacteria from soil, all of which carried the toluene-degrading plasmids, sug-
gesting that the plasmid-borne gene responsible for toluene degradation is wide
6-15
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spread in the soil microbial population. The plasmid can also be transposed into
other hosts, further increasing the number of toluene-degrading bacteria (Broda
^t^l., 1977; Jacoby et al.t 1978). The toluene plasmid in Pseudomonas putida
coded for the metabolism of toluene to the corresponding alcohol and aldehyde via
the meta pathway, to the semialdehyde and further products (Worsey and Williams,
1975; Worsey ^t al., 1978). A plasmid coding for both toluene and xylene
degradation in a Pseudomonas sp. has recently been isolated and characterized
(Yano and Nishi, 1980). Broda et al. (1977) have speculated that the ortho
pathway of toluene degradation is probably chromosomally coded.
6-16
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7. ENVIRONMENTAL AND OCCUPATIONAL CONCENTRATIONS
Monitoring data for the concentration of toluene has been divided into two
subsections, one pertaining to the environmental levels and the other to the
occupational levels.
7.1 ENVIRONMENTAL LEVELS
Toluene has been detected in the following environmental media: (1) air,
(2) aqueous media, (3) sediments, (M) solid wastes and leachates, and (5) edible
aquatic organisms.
7.1.1 Air
Toluene is the most prevalent aromatic hydrocarbon present in ambient air.
Atmospheric levels of toluene in different locations in the United States and
other parts of the world are given in Table 7-1.
From the experimental measurements of the toluene-to-benzene ratio, Pilar
and Graydon (1973) concluded that the major source of toluene in urban air with
high traffic volume is automobile emission. Recently, Pellizzari (1979) has
measured toluene levels near manufacturing and refining sites in the United
States. The ratio of toluene to benzene in these sites indicates that besides
automobile emission, manufacturing processes are probably a factor in ambient
toluene concentration at many of the sites.
It can be inferred from Table 7-1 that the atmospheric concentration of
toluene in urban areas not containing toluene manufacturing or gasoline refining
sites are in the same range as the sites containing these industries. It can
also be concluded from Table 7-1 that the concentration of toluene has declined
significantly in the past 15 years in Los Angeles, presumably as a result of
automotive emission controls. The concentration of toluene in many urban areas
7-1
-------
Table 7-1. Atmospheric Concentrations of Toluene
Concentration, ppb
Location
Year
Average
Highest, or Range
Manufacturing or Refining Sites:
Baton Rouge, LA
Birmingham, AL
El Dorado, AR
Elizabeth, NJ
El Paso, TX
Houston, TX
Magma, UT
S. Charleston, WV
Upland, CA
Other Urban Areas:
Los Angeles, CA
Azusa, CA
Riverside, CA
Denver, CO
Phoenix, AZ
Oakland, CA
Albany, NY
Troy, NY
Newbury Park CA
Tuscaloosa, AL
NRa
NR
NR
NR
NR
NR
NR
NR
NR
1963-65
1966
1967
1968
1971
1973
1979
1967
1970-71
1973
1979
1979
NR
NR
1978
1977
O.l4b
2.0
11. Ob
17'.0b
4.9b
,1.6b
0.35b
0.05b
7.3b
59C'
37 d
30e
39f
50e
22°
11.7s
14s
NRh
91
8.6s
3.1s
1.3k
1.0k
NRr
38
0.03-0.23
0.21-4.7
2.5-13.6
1.9-39.1
0.05-18.8
0.21-2.93
0.23-0.43
0.04-0.07
0.78-14.8
NR
129
50
NR
NR
NR
1.1-53.4
23
9-18
74
0.54-38.7
0.15-16.9
NR
NR
0.7-13
24-85S
7-2
-------
Table 7-1. Atmospheric Concentrations of Toluene (Continued)
Concentration, ppb
Location
Year
Average
Highest, or Range
Rural and Remote Areas:
Brethway-Gunderson Hill, WA
Camel's Hump, VT
Hell's Canyon, ID
Moscow Mt. , ID
Point Reyes, CA
Grand Canyon, AZ
Talladega Nationa Forest, AL
Global:
Zurich, Switzerland
Toronto, Canada
Berlin, W. Germany
Stockholm, Sweden
The Hauge, Netherland
1971
1971
1971
1971
1971
NR
1977
NR
1971
1975-76
NR
1974
' -0.11
1.01
0.31
0.21
0.21
Traceb
0.4
39m
30n
27°
NRP
18°
NR
NR
NR
NR
NR
Trace
0.2-1.3
NR
188
2.4-^94.2
0-2.7
54
Not reported.
Pellizzari, 1979.
^Leonard ^t al., 1976.
^onneman et al., 1968.
®Altshuller et al., 1971.
Kopcznski _e_t jd., 1972. A single measurement was made.
fSingh et al., 1979 .
^Stephens, 1973.
^Russell, 1977.
"Atwicker et al., 1977.
Robinson et al., 1973.
""Grob and Grob, 1971.
"Pilar and Graydon, 1973-
Lahmann jrt jal., 1977.
pJohansson, 1978.
Hester and Meyer, 1979.
fp. Holzer .et al., 1977.
%urgardt and Jeltes, 1975.
7-3
-------
in the United States in recent years ranged from less than 0.1 ppb to as much as
50 ppb, averaging approximately 1 to 10 ppb. In remote locations of the United
States, the value averaged approximately 0.3 ppb in 1971, but the current level
may be lower as indicated by the toluene concentration at Grand Canyon.
Sexton and Westberg (1980) monitored the air near an automotive painting
plant at Jamesville, Wisconsin, to investigate the effect of emission from paint
solvents on atmospheric toluene level. The toluene concentration downwind
within 1.6 km of the plant was 160 ppb. The concentration of toluene was still
20.5 ppb, 22.9 ppb, 17.5 ppb, and 15.1 ppb at distances 6 km, 10.5 km, 13-5 km,
and 16.5 km, respectively, downwind from the plant. These concentrations are
about 10 to 15 times higher than the background toluene concentrations of 1.5 ppb
determined at a distance of 1.6 km upwind of the plant. These concentrations are
also comparable to or higher than most of the values given in Table 7-1.
In response to numerous complaints from residents about' illness and odors in
the vicinity of a chemical solvent reclamation plant in Maryland, Smoyer e_t al.
(1971) monitored the valley air surrounding the plant. A toluene concentration
as high as 11 ppm was registered in the valley air. Both this result and the more
recent investigation of Sexton and Westberg (1980) indicate that processes
involving solvent use of toluene may result in high emission of toluene in the
vicinity of these sources.
7.1.2 Aqueous Media
Toluene has been monitored in a number of aquatic media including:
(1) surface waters, (2) industrial wastewater, (3) water from publicly-owned
treatment works (POTW), (4) underground waters, (5) municipal drinking waters,
and (6) rainwater. The toluene levels in each of the media have been discussed
separately.
7-4
-------
7.1.2.1 Surface Waters
Information regarding toluene levels in surface water has been primarily
obtained from the STORE! system as given by Slimak (1980). Table 7-2 shows the
toluene levels for major river basins in the United States. It is evident from
Table 7-2 that 83$ of all the monitored surface water contains toluene levels
below a concentration of 10 ppb. The concentration of toluene in surface waters
of the central region (Lake Erie, upper Mississipi, Lake Michigan, etc.) are
higher than surface waters from other regions. This higher level of toluene
cannot be attributed to the emission from production sites since the central
region contains only 8 of the 38 major production sites. Surface waters from
Texas, which contains 20 of the 38 production sites, showed lower levels of
toluene. This indicates that production processes may not be the major source of
toluene emission in surface waters.
Recent studies of the coastal waters of the Gulf of Mexico have shown that
aromatic hydrocarbons comprise 80$ to 90$ of the total dissolved volatile hydro-
carbons fcC-ij.) at most sampling sites (Sauer et jd., 1978). The volatile hydro-
carbons, however, were only a few percent of the total dissolved hydrocarbons.
The concentration of toluene in surface waters at several sites in the Gulf of
Mexico ranged from 4.5 ng/1 to 376.0 ng/1, while the average was 61.U ng/1.
7.1.2.2 Industrial Wastewaters
Table 7-3 shows the levels of toluene in industrial effluents as stored in
the STORET system (Slimak, 1980). It can be concluded from Table 7-3 that 85$ of
the effluents showed toluene concentrations of less than 10 ppb. Fifteen of the
reporting stations showed toluene concentration in excess of 100 ppb.
Wastewaters from a speciality chemicals manufacturing plant were analyzed
by Jungclaus _et _al. (1978). The concentration of toluene in the wastewater was
reported to be in the range of 13 to 20 ppm. Similarly, wastewater from one tire
7-5
-------
Table 7-2. Distribution of U.S. Surface Waters Within a Certain Toluene
Concentration Range (U.S. EPA, 1980)
Number of
Observations
Percent Sample in the Toluene Concentration
Range, ppb
<10
10.1-100 100.1-1000 >1000
Northeast
North Atlantic
Southeast
Tennessee River
Ohio River
Lake Erie
Upper Mississippi
Lake Michigan
Missouri River
Lower Mississippi
Colorado River
Western Gulf
Pacific Northwest
California
Great Basin
Puerto Rico
Unlabeled
TOTAL
1
14
110
16
54
2
18
30
34
8
3
15
80
5
1
1
1
393
100
93
81
98
67
20
44
88
100
100
99
100
100
100
100
83
100
4 4
666
2
100
22 11
77 3
53 3
13
1
14 3
Abbreviation: IA = insignificant amount.
7-6
-------
Table 7-3. Percent Distribution of U.S. Wastewaters Within a Certain
Toluene Concentration Range (U.S. EPA, 1980).
Effluent
Discharged
Number of
Observations
Percent
<10
Sample in the
Range,
10.1-100
Toluene Concentration
PPb
100.1-1000
>1000
Northeast
North Atlantic
Southeast
Tennessee River
Ohio River
Upper Mississippi
Lake Michigan
Missouri River
Color.ado River
Western Gulf
Pacific Northwest
TOTAL
103
48
100
28
70
64
6
16
1
1
45
482
84
88
87
96
84
69
100
100
100
100
91
85
9-
6
10
-4
11
30
7
11
4
6
3
3
2
2
3
3
1
1
7-7
-------
manufacturing company was analyzed by Jungclaus jst _al. (1976) and was found to
contain approximately 10 ppm of toluene. Both of these values are among the
highest values reported in Table 7-3-
Analysis of raw wastewater and secondary effluent from a textile manufac-
turing plant was reported to contain toluene as one of the predominant compounds
(Rawlings and Samfield, 1979). The toluene concentrations in 22 wastewater
samples and 22 secondary effluent samples were in the range of 0.5 to 300 ppb
(Rawlings and Samfield, 1979). Effluents from a paper mill in Hiro Bay, Japan,
were analyzed for organic matter. It was determined that toluene constituted 1$
of the total chloroform extractables from the effluent (Yamaoka and Tanimoto,
1977).
Toluene has also been detected in a variety of industrial wastewaters.
Table 7-M shows the frequency of toluene detection in industrial wastewaters
(U.S. EPA, 1980).
7.1.2.3 Publicly-Owned Treatment Works (POTW)
A pilot study of two POTW's, one handling more organic pollutant than the
other, was conducted for the U.S. EPA (1979). Toluene was detected in 100$ of
the influent samples and 95% of the final effluent samples from the plant con-
taining more organic pollutants. The maximum and median toluene concentrations
in the influent sample from this plant were 440 ppb and 13 ppb, respectively.
The influent sample at the other plant had maximum and median toluene concentra-
tions of 37 ppb and 10 ppb, respectively. The frequency of toluene occurrence at
this plant was 76$ for the influent and 71$ for the final effluent sample.
The state of Ohio (U.S. EPA, 1977) conducted a survey of toxic substances in
2 municipal wastewater treatment plants. The toluene concentration in the waste-
water of the plant dealing primarily with domestic wastewater ranged between
1 ppb and 5 ppb. The treated effluent from the same plant, on the other hand,
7-8
-------
Table 7-4. Detection Frequency of Toluene in Industrial Wastewaters (U.S. EPA, 1980)
Industry
Frequency of Detection
(No. Found/No. Samples)
Soap and Detergents
Adhesives and Sealants
Leather Tanning
Textile Products
Gum and Wood Products
Pulp and Paper
Timber
Printing and Publishing
Paint and Ink
Pesticides
Pharmaceuticals
Organics and Plastics
Rubber
Coal Mining
Ore Mining
Steam Electric Power Plants
Petroleum Refining
Iron and Steel
Foundries
Electroplating
Nonferrous Metals
Coil Coating
Photographic
Inorganic Chemical
Electrical
Auto and Other Laundries
Phosphates
Plastic Processing
Procelain Enameling
Landfill
Mechanical Products
Pubicly-Owned Treatment Works
1/20
2/11
19/81
56/121
11/18
4/98
58/285
50/109
48/94
23/14?
38/95
306/723
15/67
53/249
6/72
32/84
18/76
43/431
2/54
5/18
21/173
2/12
9/25
10/107
1/35
9/56
1/33
1/1
2/19
3/17
23/35
11/40
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showed a concentration of 1 ppb. About 81% of the influent from the other plant
which treated industrial-domestic wastewater showed the presence of toluene in
the concentration range of 8 ppb to 150 ppb. The frequency of toluene detection
in the treated effluent from the same plant amounted to 36$. The toluene
concentrations in these treated effluents ranged from 1 ppb to 10 ppb.
7.1.2.4 Underground Water
The New York State Department of Health and the United States Geological
Survey examined 39 wells in 1978 for organic contamination in groundwater
(Slimak, 1980). Toluene was detected in 85% of the wells tested. However, the
toluene concentration in these waters was below 10 ppb.
Toluene concentration in well water can be obtained from the data recorded
in STORET (U.S. EPA, 1980). Of the 143 monitored data, only 3 indicated the
presence of toluene in the concentration range of 42 ppb to 100 ppb. All of
these 3 wells were in the vicinity of landfill sites.
7.1.2.5 Drinking Water
Toluene has been detected in raw water and in finished water supplies of
several communities in the United States. Levels of up to 11 ppb were found in
finished water from the New Orleans area (U.S. EPA, 1975a). In a nationwide
survey of water supplies from 10 cities, 6 were discovered to be contaminated
with toluene (U.S. EPA, 1975b). Concentrations of 0.1 and 0.7 ppb were measured
in 2 of these water supplies. Toluene was detected in 1 of 111 finished drinking
waters during a second nationwide survey (U.S. EPA, 1977). In a subsequent
phase of this survey, toluene was found in 1 raw water and 3 finished waters out
of 11 supplies surveyed (U.S. EPA, 1977). A level of 19 ppb measured by gas
chromatography/mass spectronetry was found in 1 of these finished waters, and
0.5 ppb was found in another.
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Nineteen volatile organic compounds, including toluene, were detected at
concentrations below 5 ppb in District of Columbia drinking water (Saunders
e_t ^1., 1975). These investigators also found that the concentrations of the
various contaminants in tap water vary from week to week, but the chemical
composition remains the same. . - ' •
7.1.2.6 Rainwater
Toluene has been detected in rainwater from Berlin, West Germany (Lahmann
e_t al^, 1977). The toluene content in the rainwater varied with sample collec-
tion points. The rainwater from a residential area, airport, and a busy traffic
intersection showed toluene concentration of 0.13 ppb, 0.70 ppb, and 0.25 ppb,
respectively.
7.1.3 Sediment
Toluene concentrations in sediment samples as recorded in STORET (U.S. EPA,
1980) show that 91/f of the samples contain less than 10 ppb of toluene. The
concentration of toluene exceeded 500 ppb in only 1% of the samples. Samples
with higher concentrations of toluene were obtained from the vicinity of an
industrial area in San Francisco.
Jungclaus ^t ^1. (1978) monitored the sediment from a river receiving indus-
trial effluent from a specialty chemicals manufacturing plant containing
toluene. However, these investigators could not detect the presence of toluene
in the river sediment.
7.1.4 Edible Aquatic Organisms
Of the 59 monitored tissue samples that were recorded in the STORET system
(U.S. EPA, 1980), 95/6 of the data showed toluene concentrations of less than
1 ppm. The maximum toluene concentration detected in 1 fish tissue was 35 ppm.
Toluene was also detected in fish caught from polluted waters in the proximity of
7-11
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petroleum and petrochemical plants in Japan (Ogata and Miyake, 1973). A concen-
tration of 5 ppm was measured in the muscle of 1 such fish.
7.1.5 Solid Wastes and Leachates
Toluene has been detected in the air samples at a few landfill sites (U.S.
EPA, 1980a) and in well water near a few landfill sites (U.S. EPA, 1980).
However, no data regarding the level of toluene in solid wastes and their
leachates could be found in the literature.
7.2 OCCUPATIONAL CONCENTRATIONS
Several reports describing the presence of toluene in occupational atmos-
pheres were found in the literature. A toluene level of 10,000 to 30,000 ppm was
reported in a merchant ship after it was internally sprayed with a toluene-
containing insecticide (Longley e_t al., 1967). Two hours after the initial
monitoring, concentrations ranging from 5000 to 10,000 ppm were still present in
the atmosphere of the ship.
A monitoring program was instituted in response to a report of an epidemic
solvent poisoning in a rotogravure plant in Milan, Italy. Solvent containing
toluene was largely used in this plant as an ink solvent and diluent. The
results of the monitoring showed that the concentration of toluene ranged from 0
to 277 ppm in different parts of the work areas (Forni at al., 1971). The
determined toluene concentration at different parts of the plant during the
period 1957 to 1965 is shown in Table 7-5.
In 1966, the above rotogravure plant was moved to a different location and
the ventilation system of the plant was improved. Subsequent analysis for
toluene showed annual mean concentrations at 156 ppm and 265 ppm near the folding
machines and between the machine elements, respectively (Forni et jd., 1971).
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Table 7-5. Toluene Concentrations in Different Work Areas of a Rotogravure
Plant in Milan, Italy (Forni et al., 1971)
Toluene concentration, ppm
Work Area
Range
Annual Mean
Center of Room
Folding Machines
Between Machine Elements
140-239
56-277-
306-824
203
203
431
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A study of 8 Japanese factories operating polychromic rotory processes for
photogravure printing reported toluene concentrations in the range of H to
2MO ppm in different work areas of the plants (Ikeda and Ohtsuji, 1969).
Toluene exposures to workers in 11 leather-finishing and rubber-coating
plants have also been reported (Pagnotto and Lieberman, 1967). Toluene is used
as lacquer thinners and stain removers in the leather finishing industry. In
rubber-coating plants, the major source of toluene emission is the fabric-
spreading machine areas. The concentration of toluene in work areas of these
industries is shown in Table 7-6.
Toluene has been detected in other occupational atmospheres. For example, a
toluene concentration of 0.18 ppm Has been reported in a submarine atmosphere
(Chiantella jit al., 1966). The origin of toluene in this atmosphere has been
speculated to be paint solvents and diesel fuel used in the submarine. Toluene
has been detected in the atmosphere of M15 and M19 antitank mines (Jenkins
.et.al., 1973). The origin of toluene in this atmosphere was attributed to mine
casings.
A more recent study (Fraser and Rappaport, 1976) designed to determine the
health effects associated with the curing of synthetic rubber simulated the vul-
canization process in the laboratory. Toluene emission in the vulcanization area
from this experiment amounted to 1.1 ppm. The actual field survey of different
work areas of 10 large tire manufacturing plants across the United States was
conducted by Van Ert e_t jd. (1980). The toluene concentrations in different work
areas measured by these investigators is shown in Table 7-7.
It can be concluded from Table 7-7 that the extrusion process area and the
tire building process area are the 2 areas of tire manufacturing plants that
account for the major toluene emissions from these plants.
7-14
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Table 7-6. Toluene Concentrations in Work Areas of Leather Finishing and
Rubber Coating Plants (Pagnotto and Lieberman, 1967)
Toluene Concentration, ppm
Industry Work Areas Range Average
Leather finishing Jr?a . . %-** 110
* Washing and Topping Area 29-195 112
Rubber Coating Spreading Machines " 3^-120 73
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Table 7-7. Toluene Concentrations in Selected Work Areas of Tire
Manufacturing Plants (Van Ert et al., 1980)a
Work Area
No. of Plants
Surveyed
Area Toluene Concentration, ppm
Mean
Range
Cement Mixing
Extrusion
Tire Building
Curing Preparation
Inspection and Repair
Warehouse
8
4
2
3
3
2
. " - 2.9
14. 0
.8.0
0.6
1-9
0.28
0.2-7.7
3.3-50.0
2.5-13.4
0.1-1.1
0.6-2.7
0.01-0.76
All of the plants, with the exception of plants where the warehouse samples
were taken, were surveyed during 1973-77. The warehouse samples were collected
in 1977.
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7.3 CIGARETTE SMOKE
The concentration of toluene in inhaled cigarette smoke is approximately
0.1 mg/cigarette (NRC, 1980; Dalhamn et al., 1968). Jerimini et al. (1976)
determined the concentration of toluene in the sidestream smoke of cigarettes.
When 30 cigarettes were inhaled in a 30 nr room and the concentration of toluene
in room air was determined, it was found to be 0.23 ppm. This value corresponds
to 0.87 mg of toluene in the sidestream smoke of each cigarette. Holzer e_t al.
(1976) determined the toluene concentration in a 60 m^ room and found an ambient
toluene concentration of 40 ppb. When 1 cigarette was smoked in the room, the
concentration of toluene rose to 45 ppb. This corresponds to 1.1 mg of toluene
contribution from each cigarette. It seems from this discussion that the main-
stream smoke of 1 cigarette contributes 0.10 mg toluene to the smoker. The
sidestream smoke, on the other hand, may contain a higher amount of toluene.
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8. ANALYTICAL METHODOLOGY
Toluene has been analyzed in a multiple of media including the following:
(1) air, (2) waters, (3) soils and sediments, (4) crude oil and organic solvents,
(5) biological samples, (6) some foods, and (7) cigarette smoke. The analytical
methods for the determination of toluene in each of these media are individually
discussed below.
8.1 AIR
In addition to the analysis of test mixtures of toluene in air for the
evaluation of methods, toluene has also been determined in ambient air, occupa-
tional air, forensic air, and air containing the pyrolysis products of organic
wastes.
8.1.1 Ambient Air
The determination of toluene in ambient air consists of two distinct steps:
sampling and analysis.
8.1.1.1 Sampling
Toluene can be collected from ambient air in several different ways includ-
ing grab sampling in aluminized plastic bags (Neligan e_t _al., 1965), Tedlar bags
(Altshuller et _al., 1971; Lonneman _et jil., 1968), and glass containers (Schneider
£t^l., 1978; Pilar and Graydon, 1973). Although the grab sampling is concep-
tually the simplest approach, this collection method without subsequent concen-
trative technique does not provide sufficient quantity of toluene for analytical
detection and quantification. Since ambient samples contain toluene in the parts
per billion range, preconcentration steps are often necessary.
Sample collection by cyrogenic procedures (Seifert and Ullrich, 1978) is an
alternative method for the collection of toluene in ambient air; however, the
drawbacks of this procedure include the inconveniences in sampling and sample
8-1
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regeneration. Also, unless the moisture in air is removed, it condenses in the
collection tube and may reduce or restrict the air flow through the collection
tubes. Various drying agents, such as anhydrone, anhydrous KpCO,, ascarite, LiH,
and molecular sieve can be used. It has, however, been demonstrated by Isidorov
et _al. (1977) that it is impossible to find a drying agent that will preferen-
tially absorb the moisture from air without absorbing some of the trace organics.
Reversible sorption on various high surface area materials provides an
excellent method for preconcentrative collection of toluene from ambient air.
Since the moisture content in the air is normally 3 to 4 orders of magnitude
higher than the total organics (Isidorov ^t ^1., 1977), the chosen sorbents must
show little affinity toward moisture. Otherwise, the retention capacity of the
sorbents will be reached much sooner than desired.
A number of sorbents such as Tenax GC (Holzer et, jd., 1977), various car-
bonaceous materials (Burghardt and Jeltes, 1975; Holzer _et _al., 1977; Isidorov
£t jl., 1977), Polisorbimid (Isidorov et al.. 1977), molecular sieves and
spherisil (Ball, 1976), and Porapak Q (Johansson, 1978) have been successfully
used. Typically, sampling is performed by drawing air through a trap containing
the selected sorbent with battery-operated diaphragm pumps. The air flow through
the trap is controlled by needle valves and measured by a previously calibrated
rotometer. The trap is kept at ambient temperature to avoid condensation of
water. At the end of the sampling, the trap-ends are closed with caps and
transferred to the laboratory in a refrigerated state, to avoid sample loss.
8.1.1.2 Analysis
The method of analysis is usually dependent on the method of sample collec-
tion. The earlier investigators who used plastic bags or glass bottles for
collection of grab samples utilized a trapping system for concentrating a rela-
tively large volume (1 to 10 1) of sample before analysis. In this method, the
8-2
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collected sample is allowed to flow through a cryogenic trap containing suitable
sorbents. At the end of trapping, the coolant is removed from the trap and the
trap is quickly heated to vaporize and transfer the trapped compounds into the
gas chromatographic (GC) columns. The columns used by earlier investigators
(Lonneman e_t al., 1968; Al tshuller e_t al., 1971) for aromatic separations con-
sisted of long open-tubular columns coated with m-bis(m-phenoxy-phenoxy)benzene
combined with Apiezon grease on a packed dual column with SF-96 as the liquid
phase (Pilar and Graydon, 1973).
The more recent methods, which use sorbents for trapping organics, connect
the trap to a GC systems via multiple-port gas sampling valves. The trap is
quickly heated and the desorbed organics are passed through the chromatographic
columns. Since the collected samples contain a multitude of organics, capillary
columns are normally used for the resolution of the organics. The Grob and Grob
(1971) technique, involving the passage of the thermally desorbed organics
through a small uncoated section of the capillary column cooled crypogenically,
is used. When the collection is completed, this section of the capillary is
quickly heated and the sample is separated on the remaining portion of the
analytical column. A number of coating materials for capillary columns including
Emulphor ON-870 (Holzer et al., 1977), UCON 50 HB 2000 or 5100 (Johansson,
1978), dinonyl phthalate (Isodorov e_t al., 1977), A120- (Schneider et al., 1978),
DC-550 (Louw and Richards, 1975), OV-17 and OV-101 (Pellizzari et al., 1976) have
been used.
In one method, the method of thermal desorption of organics from the
sorbents was replaced by solvent desorption (Burghardt and Jeltes, 1975). In
this procedure, the organics sorbed on activated carbon were desorbed by CS_. A
part of the CS- was injected into a packed column GC containing a long column
coated with 1,2,3-tri-(2'-cyanoethoxy)-propane.
8-3
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The quantification of toluene separated by the GC columns is almost exclu-
sively done by flame ionization detectors (FID). Confirmation of the authen
ticity of the GC peaks is often provided by coupled mass spectrometer (MS), with
or without the aid of a computerized data system (Holzer e_t jd., 1977; Pellizzari
et at., 1976).
A continuous automated procedure for the determination of toluene in the
ambient air was developed by Hester and Meyer (1979). This method needs no
sample preconcentration prior to analysis. In this method, a small diaphragm
pump activated by a timer automatically injects air into 1-ml gas-sampling (GS)
loop of a GC every 10 minutes. The separating column was packed with
Chromosorb P coated with N,N-bis(2-cyanoethyl)formamide. Since no concentration
method was employed, the detector used had about two orders of magnitude higher
sensitivity than flame ionization detectors. A photoionization detector was
found to show the required sensitivity.
8.1.1.3 Preferred Method
The preferred method for the monitoring of toluene in ambient air consists
of sorbent collection, thermal elution, and GC-FID determination. Collection by
trapping toluene in a solid sorbent provides a concentration method during sample
collection. Thermal desorption is preferred over solvent elution because of the
higher sensitivity of the former method. Tenax GC is perhaps the most suitable
sorbent for sample collection. The collection and thermal desorption efficiency
of toluene is excellent with Tenax GC. The generation of artifacts during
thermal elution with Tenax GC can largely be eliminated by proper clean up of the
sorbent and GC conditioning procedure (Holzer £t _al., 1977). The greatest
advantage of the ambient sorption-thermal elution method is its extreme simpli-
city and speed.
8-4
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The separation and quantification of sorbent desorbed components can be
achieved by GC-FID method. Although photoionization detectors (PID) may have
higher sensitivity than flame ionization detectors, this higher level of sensi-
tivity is not required when the samples are preconcentrated by solid sorbents.
High resolution capillary columns are a necessity because of the observed com-
plexity and low concentration of the samples. Of the different coating materials
available, N,N-bis-(2-cyanoethyl)formamide and 1,2,3-tris(2-cyanoethoxy)-
propane are probably most suitable for the separation of aromatic components.
8.1.1.1 Detection Limits
The detection limit of toluene in ambient air is dependent on the volume of
air passed through the sorbent trap. For a 25-1 sample, the detection limit is
less than 0.1 ppb (Holzer et al., 1977) with a capillary column and flame ioniza-
tion detector. When direct injection (1 ml) and GC-PID method are used, the
detection limit for toluene is 0.3 ppb (Hester and Meyer, 1979).
8.1.2 Occupational Air
8.1.2.1 Sampling
The concentration of toluene in occupational air is normally much higher
than in ambient air. Therefore, collection of samples in certain instances may
not require a concentration step. The collection of samples by the grab method
has been used by a number of authors (Tokunaga et al., 1971*; Chovin and Lebbe,
1967).
Some of the earlier methods used liquid scrubbers for absorbing toluene from
occupational air. A number of scrubbers, including potassium iodate in dilute
sulfuric acid (Ministry of Labour, 1966), cooled organic solvents such as ethyl
cellusolve acetate, dimethylformamide, and dimethyl sulfoxide in dimethyl forma-
mide (Ogata et al., 1975), and nitrating solution (Chovin and Lebbe, 1967) have
been used. In addition to the inherent limitations in its ability to overcome
8-5
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the interferences, this method is not convenient for the collection of breathing
zone samples.
The more recent methods used solid sorbents for the collection of toluene.
Silica gel (Ogata et ad., 1975; Tokunaga ej; jd., 197M), activated carbon
(Esposito and Jacobs, 1977; Fracchia ^t aL., 1977; Reid and Halpin, 1968; Fraser
and Rappaport, 1976; NIOSH, 1977) and Tenax GC (Nimmo andd Fishburn, 1977) are
some of the sorbents used for this purpose. Aromatic hydrocarbons such as
toluene are easily displaced from silica gel by water vapor, resulting in
possible losses of toluene in humid atmospheres (NRC, 1980). Therefore, both
activated carbon and Tenax GC are the two most frequently used sorbents for the
collection of toluene from occupational air. The suitability of either of the
sorbents is dictated by the method of sample analysis. When thermal desorption
is used, Tenax GC is the preferred sorbent. On the other hand, activated carbon
is preferred when solvent desorption is the method used.
8.1.2.2. Analysis
For grab samples, direct injections into a GC system via syringes or gas
sampling loops have been applied (Tokunaga e_t jd., 1971*; Chovin and Lebbe, 1967).
The separating columns used in these cases were packed columns with stationary
liquid phases of either dioctyl phthalate (Tokunaga et al., 1974) or bis-(beta-
cyanoethyDformamide (Chovin and Lebbe, 1967). Flame ionization detectors were
used for the quantification of toluene in both cases; however, this method is
capable of analyzing toluene in work atmosphere at concentrations of around
10 ppm (Chovin and Lebbe, 1967).
Toluene collected by scrubber methods is usually analyzed by colorimetric
methods. Irrespective of the different variations, most colorimetric methods
show interferences from other chemically similar compounds (e.g., benzene,
xylenes, ethylbenzenes) that are normally cocontaminants of toluene.
8-6
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The first step in the analysis of toluene collected in solid sorbents is
desorption. Two methods are usually available for desorption: thermal and
solvent. Carbon disulfide is the most frequently used solvent for the desorption
of toluene from solid sorbents (Esposito and Jacobs, 1977; Fracchia e_t al^, 1977;
Reid and Halpin, 1968; NIOSH, 1977; Van Ert et al., 1950), although some investi-
gators have used other solvents (Ogata e_t _al., 1975). Solvent desorption is the
method of choice when activated carbon is used as the sorbent. Activated carbon
has not only high efficiency of reversible toluene'sorption, but it has almost
quantitative toluene desorption efficiency with CS? (Fracchia £t _al., 1977). In.
the presence of other common organic solvents found in the work atmosphere (e.g.,
n-butanol, cellosolve acetate, butyl cellosolve, etc.), the CS. extraction
~~
-------
Other methods of analysis, such as high pressure liquid chromatography
(HPLC) on a reverse phase column with methanol-water as the mobile phase and
ultraviolet (UV) detection, have been attempted (Esposito and Jacobs, 1977), but
the sensitivity of detection was poor.
Methods involving the use of detection tubes have been applied for the
determination of toluene in occupational air (Tokunaga e_t al., 197*0. The
accuracy of the detector tubes for toluene quantification is rather poor, parti-
cularly in the presence of other organic vapor (Tokunaga e_t _al., 1974). There-
fore, the detector tubes are suitable for the rough estimation of toluene concen-
tration in the work atmosphere.
A simple directly-combined GC-IR (infrared) system was developed to detect
low molecular weight hydrocarbons in air (Louw and Richards, 1975). In this
method, the grab sample is directly injected into a GC and the effluent from the
GC column is split in a certain ratio (1:49). The major portion of the effluent
is directed toward a cold trap (-50°C) to freeze the organics. At the end of the
trapping process, the trap is quickly heated and the released gases are allowed
to pass through a microlight pipe gas cell of an IR detector. This method has
been claimed to detect 1U-19 ug of each sample component present in air (Louw and
Richards, 1975); however, no field samples have been analyzed with this system.
8.1.2.3 Preferred Method
The preferred method for monitoring toluene in occupational air can be
either the NIOSH (1977) method of activated carbon sorption and CS_ desorption or
Tenax GC sorption and thermal desorption. The quantification of desorbed toluene
by GC-FID is still the method of choice. As in the case of ambient air samples,
N,N-bis(2-cyanoethyl)formamide liquid phase will provide one of the best separa-
tions for the aromatics.
8-8
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8.1.2.H Detection Limit
The detection limit for toluene by carbon sorption-CS. desorption method
depends on the volume of air sampled. Concentrations as low as 0.1 ppm toluene
in a rubber tire manufacturing factory have been detected by this method
(Van Ert, 1980). For a 100-ml sample, the Tenax GG sorption-thermal desorption
method showed a detection limit of 0.5 ppb (Nimmo and Fishburn, 1977).
8.1.3 Forensic Air
In suspected arson cases, the method of Twibell and Home (1977) can be
applied to speculate or even confirm the cause of fire. According to this
method, nickel wires (curie point 358°C) coated" with finely-divided activated
carbon with the aid of an inert adhesive (cement binder LQ/S6) are suspended in
the atmosphere under test for 1-2 hours at room temperature. The apparatus is
connected to a GC-FID system, and the wires are heated by induction heating. The
resulting chromatographic profile obtained from the desorbed gases can be com-
pared with different fire accelerant residues (e.g., gasoline). Although the
method is not quantitative, it has been claimed to show a better sensitivity than
the method of hot headspace analysis (Twibell and Home, 1977).
8.1.4 Gaseous Products from Pyrolysis of Organic Wastes
The gaseous products from a pilot plant burning such organic wastes as wood
shavings, solid municipal wastes, and rice hull were analyzed by Brodowski et al.
(1976). The method consisted of collecting grab samples in stainless steel
sampling bulbs and injecting 0.5 ml of the gas into a GC. The separating columns
were dual stainless steel columns packed with Porapak QS modified with tere-
phthalic acid. Evidently, the method does not have high sensitivity of detec-
tion. The toluene concentration of the pilot plant gaseous products was deter-
mined to be 0.2 to 0.3 mol % by this method (Brodowski ^t al., 1976).
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8.2 WATER
Toluene has been determined in a number of aqueous media including surface
waters, industrial wastewaters, water from publicly-owned treatment works
(POTW), underground water, drinking water, and rainwater.
8.2.1 Sampling
Water samples other than industrial wastewater samples are generally col-
lected by the grab method. In the case of industrial discharges where the
discharge parameters are dependent on the operating process, continuous samples
using a commercial composite sampler have been used (Rawlings and Samfield,
1979). The preservation and handling of the aqueous samples after collection are
especially important for volatile components. The samples are collected in glass
bottles that are filled to overflow and sealed with teflon-backed silicon rubber
septa and screw caps. It has been demonstrated that simple samples in non-
reactive matrix (e.g., drinking water, ground water) collected in the above
fashion can be held under ambient conditions from 10 to 22 days without signifi-
cant loss of volatile compounds (Bellar and Lichtenberg, 1979); however, waste-
water samples should be adjusted to a pH of 2 by adding dilute hydrochloric acid.
Any free chlorine should be neutralized by the addition of 35 mg of sodium
thiosulfate per 1 ppm of free chlorine (Federal Register, 1979) before the
samples are collected in glass bottles. The samples must be iced or refrigerated
during transportation and storage. All such wastewater samples should be
analyzed within 7 days of collection (Federal Register, 1979).
8.2.2 Analysis
Although direct injection (Jungclaus £t ad., 1978) and solvent extraction
(Yukiho and Terumi, 1977; Jungclaus e_t al., 1976) methods have been used to
determine the concentration of organics including toluene in industrial waste-
waters, these methods are not suitable for toluene determination in other media.
8-10
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Even in wastewater, both of these methods have questionable accuracy. The direct
aqueous injection method does not have good sensitivity and the solvent extrac-
tion method is likely to provide low recovery since some of the volatile compo-
nents will be lost during the concentrative evaporating step.
The three most commonly used methods for toluene analysis in aqueous media
are (1) purge and trap, (2) headspace, and (3) sorption on solid sorbents. Each
of these methods is individually discussed below.
8.2.2.1 Purge and Trap
Purge and trap is the most widely used method for the analysis of toluene in
aqueous media. It has been used for the determination of toluene in drinking
waters (Bertsch et al., 1975; Lingg et al., 1977; Ryan and Fritz, 1978), in
wastewaters (Bellar and Lichtenberg, 1979; Rawlings and Samfield, 1979;
Jungclaus et al., 1978), and in rainwater (Seifert and Ullrich, 1978). The U.S.
Environmental Protection Agency recommends the use of this method for toluene
analysis in wastewater (Federal Register, 1979).
In this method, an inert gas (helium) is bubbled through a water sample via
a glass frit contained in a specially designed purging chamber. The aromatics
released into the vapor phase are swept through and trapped in a sorbent tube.
After the purging and trapping is completed, the trap is transferred to the
injection port of a GC. The trap is heated and backflushed into a GC system,
where the separation of the volatiles takes place. Both packed (Bellar et al.,
1979; Lingg et al., 1977; Federal Register, 1979) and capillary columns (Dowty
et al., 1979; Bertsch ^t al., 1975) employing a variety of liquid phases have
been used. The resolution of components can be expected to be better with
capillary columns.
The detection of the GC column effluents can be done either by flame ioniza-
tion detector (Dowty et al., 1979) or photoionization detector (Federal
8-11
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Register, 1979). The use of photoionization detector will provide better selec-
tivity and sensitivity of detection. The confirmation of GC peaks is usually
provided by mass spectroraetry aided by a computerized data system (Lingg et al.,
1977; Dowty .et al., 1979 ; Bellar et al., 1979).
A number of variations of the purge-trap method (Grob and Zucher, 1976;
Lingg et al., 1977; Dowty et al., 1979; Bellar et al., 1979) involving the
variation of water volume, the temperature of the purging system, the stripping
rate, the duration of stripping, the nature of sorbent, and the method of desorp-
tion (thermal versus solvent) are available. Using a 5-ml sample size and flame
ionization detection, Dowty ^t al. (1979) determined the lower detection limit
for toluene to be 0.1 ppb by this method. The detection limit can be further
lowered if a larger volume of sample (Lingg et al., 1977) or photoionization
detection method is used. The purge-trap method is the preferred method for the
monitoring of toluene both in drinking and wastewater samples.
8.2.2.2 Headspace Analysis
This method has not been frequently applied for the analysis of field
samples; however, the method was standardized with water samples spiked with
model compounds (Vitenberg et jil., 1977; Drozd e_t al., 1978).
In the method of Drozd e_t al. (1978), a known volume (50 ml) of water is
introduced into a specially designed enclosed glass apparatus (100 ml) and the
system is thermostatically maintained at 40°C. After the system attains equi-
librium (30 minutes), a known volume of headspace vapor is introduced into a
capillary GC system via a trapping system consisting of a short cooled (-70°C)
precolumn coated with OV-101 (Grob and Grob technique). The separating colum was
coated with squalene.
The method of headspace analysis in the past had faced problems owing to the
difficulty in establishing a calibration procedure. The partition coefficient
8-12
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of a component between gas and liquid phases is dependent on the total ionic
strength in solution. Therefore, the same concentrations of a component present
in two aqueous solutions of different ionic strengths but otherwise identical
conditions, will not produce the same equilibrium vapor pressure. This problem
of a calibration curve has been largely obviated through the development of a
standard addition method (Drozd et al., 1978). Water samples containing toluene
in the parts per billion range can be quantified by this method (Drozd ejt al.,
1978) with a reasonable accuracy; however, the method may not be applicable for
drinking water samples where the concentration may be lower than 1 ppb.
8.2.2.3 Sorption on Solid Sorbents
This method is rarely used for the monitoring of toluene in aqueous samples.
The applicability of the method was explored by Pfaender (1976), and Ryan and
Fritz (1978) utilized the method for monitoring toluene in drinking water.
The method consists of passing a known volume of water through a sorbent
such as XAD-2 (Pfaender, 1976) or XAD-U (Ryan and Fritz, 1978). The sorbed
organics including toluene are desorbed either by solvent extraction (Pfaender,
1976) or by thermal desorption (Ryan and Fritz, 1978) and injected onto a GC-FID
system for component separation and quantification. In the thermal desorption
method of Ryan and Fritz (1978), the use of a trap consisting of a Tenax GC
precolumn to eliminate the excess water showed a good sensitivity for the method.
The recovery of toluene was nearly 90$ when the concentration in drinking water
ranged from 1-10 ppb. For the quantification of toluene in water by this method,
the recovery of toluene from the sorbent should be known.
8.3 SOILS AND SEDIMENTS
8.3.1 Sampling
Bottom sediment samples can be collected either by Hopper-dredge or by clam-
type dredge samplers (U.S. EPA, 1979). Hopper-dredge collected samples
8-13
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generally contain more water than clam-type dredge-collected samples. Bottom
sediment samples can also be collected using a core sampler (U.S. EPA, 1979).
For volatile organic analysis, the samples should be collected in screw-
capped glass containers lined with aluminum foil (Jungclaus ^t al., 1978) or in
glass hypovials with crimped aluminum seals and teflon-backed septa (U.S. EPA,
1979). For best results, the container should be filled to maximum capacity to
reduce 'the amount of headspace and should be transported and stored at wet ice
temperature (U.S. EPA, 1979).
The method of soil sampling is given in detail by de Vera £t _al. (1980). The
soil samples should be taken in a grid pattern over the entire site. A scoop can
be used for collection of soil samples up to 8 cm deep. To sample beyond this
depth, a soil auger or Veihmeyer soil sampler, as described by de Vera et al.
(1980), should be used. After the sample is transferred into glass containers to
a maximum capacity, the container must be tightly capped with contamination-free
lids to prevent loss of volatile components and to exclude possible oxidation.
The samples should be refrigerated (4°C) during transport and storage.
8.3.2 Analysis
Very few reliable methods are available for the analysis of volatile
organics in soil and sediment samples. Solvent extraction methods using highly
volatile solvents are not likely to be successful. The evaporative concentration
step of this method would result in the loss of volatile organics. Headspace
analysis, which has few provisions to concentrate the organics, will produce
unreasonably high detection limits.
A modification of the purge and trap method has been suggested by the U.S.
EPA (1979) for the analysis of soil and sediment samples. The modified purge and
trap apparatus used for this purpose is described by the U.S. EPA (1979). The
sample, contained in a specially-designed glass vial, is heated at 80°C and
8-14
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purged with helium gas. The desorbed organics are trapped in a Tenax GC column.
At the end of trapping, the Tenax GC column is inserted in the injection port of a
GC, and the thermally desorbed organics are analyzed by GC-FID as in the case of
water and wastewater samples. The recovery of toluene was determined to vary
between 32% and UUJ when 0.1 ug to 3.0 yg of toluene was spiked onto a specially
prepared soil matrix. Although the recoveries were low, they were found to be
linear and reproducible (U.S. EPA, 1979). Data on spiked environmental samples
showed much higher recoveries (80-100J).
With the purge-trap system described, the minimum detection limit of
0.1 ppb can be attained. Thus, the method showed at least two orders of magni-
tude higher sensitivity than headspace analysis (U.S. EPA, 1979).
8.4 CRUDE OIL AND ORGANIC SOLVENTS
Benzene and toluene concentration in petroleum crude and other fossil fuel
samples can be determined by a method developed by Grizzle and Coleman (1979).
In this method, the sample is directly injected into a GC system containing two
columns in series. The effluent from the first column containing aromatics is
separated into individual fractions by the second column. Quantification of the
separated components is done by a flame ionization detector.
A combination of liquid chromatography (silica gel column) and GC-FID
method was employed by Fett e_t al. (1968) routinely to determine toluene in
hydrocarbon solvents.
8.5 BIOLOGICAL SAMPLES
Toluene or its metabolites have been determined both in blood and in urine
samples. These methods of analysis are discussed below.
8.5.1 Blood
Toluene in blood has been determined by GC analysis of headspace samples
(Premel-Cabie et al., 1971*; Anthony et al., 1978). According to this method,
8-15
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blood is equilibriated with air in a closed container at a fixed temperature.
The headspace gas is injected into a GC-FID system for detection of toluene. The
method can be used for quantification of toluene in blood by the standard addi-
tion method as described in subsection 8.2.2.2.
8.5.2 Urine
In the body, toluene is mainly oxidized to benzoic acid which, after con-
jugation with glycine, is eliminated as hippuric acid in the urine. Hippuric
acid may be formed from other metabolic processes besides toluene metabolism.
Hippuric acid in urine can be determined by a number of methods including
colorimetry (Umberger and Fioresse, 1963) and -UV spectrometry (Pagnatto and
Lieberman, 1967); however, one of the better methods of hippuric acid analysis in
urine was developed by Caperos and Fernandez (1977). According to this method,
the hippuric acid in acidified urine is extracted with ethyl acetate. The
extracted hippuric acid is esterfied with 1-p_-tolyltriazene. The dried ester is
dissolved in chloroform and quantified by GC-FID. The recovery of hippuric acid
by this method is determined from the recovery of an added internal standard.
The sensitivity of the method with 0.5 ml urine was determined to be 5 mg/1.
8.6 FOODS
A headspace GC technique for quantification and a GC-MS technique for con-
firmation were used to determine trace amounts of toluene in plastic containers
(Hollifield ^t al., 1980). The sample, taken in a specially enclosed vial, was
heated at 90°C for 2 hours and 2 ml of headspace gas was injected into a GC
system. The principle of standard addition was used for the quantification of
toluene. Toluene present in parts per billion range can be determined by this
method.
8-16
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8.7 CIGARETTE SMOKE
The concentration of toluene both in sidestream smoke (Jerimini ^t al.,
1976) and mainstream smoke (Dalhamn jet _al., 1968) has been determined. For the
determination of toluene in mainstream smoke, standard cigarettes were smoked by
machine under standardized conditions (a 2-second 35-ml puff once every minute).
The mainstream smoke is collected in a cold trap (Dalhamn et al., 1968). The
contents of the cold trap can be introduced into the GC by multiport valves and
analyzed by GC-FID for toluene determination.
Toluene determination in sidestream smoke can be accomplished by adopting
the sampling and analysis technique of Holzer ^t al. (1976). The sidestream
smoke can be collected by drawing the smoke through a solid sorbent tube packed
with Tenax GC. The Tenax GC sorbent tube can be thermally eluted onto a glass
capillary column for the determination of toluene content. Adoption of a cold
trap for splitless injection of the sample into the capillary column (Grob and
Grob technique) will enhance the sensitivity and accuracy of the method. Addi-
tional confirmation of the GC peaks can be done by interfacing the GC with a MS
(Holzer et al., 1976).
8-17
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9. EXPOSED POPULATIONS
The number of people exposed to various sources of toluene can be divided
into three categories, namely, general population, occupational group, and
cigarette smokers. The breakdown of general population subjected to inhalation
exposure of toluene from various sources of emissions can be obtained by perform-
ing a population analysis around each source. A computer program was used by
Anderson et_al. (1980) to extract site-specific population patterns from the U.S.
Census figures standardized to 1978 population levels. The number of general
population exposed to various levels of toluene from different sources of
emission as calculated by Anderson et al. (1980) is shown in Table 9-1. For an
explanation of the breakdown of the source variety shown in Table 9-1, see
subsection 8.1.1.
The exposed population count shown in Table 9-1 is derived from the geo-
graphical coordinate of each location. Error in the geographical coordinates of
a source and population center will cause errors in population count. In addi-
tion, the population count figures obtained from U.S. Census Bureau is subject to
undercounting. The result of this undercounting will be lower population expo-
sure estimates than the actual case.
No estimate of the number of general population exposed to toluene from
ingestion of foods and drinking waters can be given. Toluene has been detected
in only a small fraction of total drinking water supplies and foods that have
been monitored. The number of people consuming the contaminated waters and foods
is not known at the present time.
According to the estimate of the Department of Health, Education, and
Welfare (1977), more than 4.8 million people per year are occupationally exposed
9-1
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Table 9-1. Population Distribution and Inhalation Exposure Levels of
Toluene from Different Sources (Anderson et _al., 1980)
Number of People Exposed From
Concentration Specific Prototype Area
Level Point Sources Point Sources Sources
>100 0 159 58,347
100 - >50 0 2,841 446,793
50 - >25 34 10,200 ' 12,348,504
25 - >10 475 22,700 42,478,913
10 - >5 1,434 33,900 66,368,769
5 - >2.5 6,103 75,200 0
2.5 - >1 19,781 240,000 - 0
1 - >0.5 39,064 246,000 0
0.5 - >0.25 95,883 350,000 0
0.25 - >0.1 269,883 1,229,000 0
0.1 - 0 34.316.299 0 34.977.809
Subtotals 34,748,633 2,210,000 158,679,135
Total 195,637,768
9-2
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to toluene. Toluene ranks fourth among all other agents listed in terms of the
number of people exposed to any single agent.
The number of people in the U.S. exposed to toluene through cigarette smoke
has been estimated to be 56 million during the year 1978a. This figure which
considers the exposure to the smokers only, is bound to be an underestimate since
it does not include passive smokers.
This figure is based on the following assumptions 'of the total population of
225 million, 21.4$ are under age 13 (Dept. Commer., 1979) and do not smoke.
Teenagers in the age group 13 years to 17 years constitute 7.6% of the total
population (Dept. Commer., 1979). Of the 7.6$ of the teenagers, only 11.7$
are assumed to be smokers (PKS, 1980). Of the remaining population, 51$
are assumed to be females and 49$ to be males (Dept. Commer., 1979). The
percent of female and male smokers over age 17 are assumed to be 30.4$ and
37.4$, respectively (PHS, 1980).
9-3
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10. INTEGRATED EXPOSURE ANALYSIS
Exposure is the contact between a subject of concern and an agent such as a
chemical, biological, or physical entity. The magnitude of the exposure is
determined by measuring or estimating the amount of an agent available at the
exchange boundaries, that is, lung, gut, and skin, during some specified time.
Exposure assessment is the qualitative estimation or quantitative determination
of the magnitude, frequency, duration, and route of exposure. Exposure assess-
ments are often combined with environmental and health effects data in performing
risk assessments. The exposure of an agent may lead to the intake of some of the
agent. Uptake or an absorbed dose is the amount of the intake which is absorbed
by the subject.
The assessment of human health risks from exposure to any environmental
pollutant requires knowledge of (1) the dosage of the pollutant received by the
exposed human population and (2) the effect of the pollutant on human health.
Because the purpose of this section is not to develop a health effects model, no
attempt will be made to address such parameters as population characteristics
(e.g., age, sex, occupation, racial background), population habits (e.g., food
habits, recreational habits, product-use habits), and population groupings
(e.g., the aged, pregnant women, children, other high health risk groups).
Instead, this section will attempt to derive the human exposure of toluene
received from all sources of emissions.
In order to make an exposure asessment, one must consider the following:
route of entry; magnitude of exposure; frequency of exposure; and duration of
exposure. The general population may be exposed to toluene through the following
three routes: (1) inhalation of air; (2) ingestion of water and foods; and
(3) exposure through skin. The next step toward an integrated exposure analysis
10-1
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combines the estimation of environmental concentrations with the description of
the exposed population to yield exposure profiles and exposure pathway analysis.
Certain segments of population may be exposed to toluene through occupa-
tional exposure and cigarette smoking. Because exposure of this segment of the
population falls under a special category, these scenarios will be discussed
separately. It should be mentioned that this section does not include toluene
exposure from the use of consumer products. As has been mentioned in Sub-
section 10.5, some consumer products contain high percentages of toluene.
Undoubtedly, the use of these consumer products would lead to various degrees of
toluene exposure in the general population; however, no data are available from
which estimates of toluene exposure from consumer products could be derived.
10.1 EXPOSURE VIA INHALATION
Estimation of toluene exposure via inhalation can be done in two ways. The
exposure can be estimated from the total nationwide toluene emission data by the
use of mathematical models simulated to reflect the actual environmental
setting. The exposure can also be estimated from actual monitoring data. Esti-
mating exposure on the basis of monitoring data is often a preferred method
because these data directly provide the environmental distribution of toluene;
however, this method has its own limitations. Although the monitoring data
available for toluene are more abundant than those available for many other
organic chemicals, they do not include many exposure scenarios. The monitoring
data may not provide information on the extent of concentration variation due to
chemical reactivity (e.g., photoreaction, oxidation in the atmosphere, etc.).
These data also do not yield relationships between materials balance of the
emitted toluene and the environmental concentration distribution in an area.
Therefore, the approach toward exposure estimation in this section has utilized
10-2
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both the available ambient monitoring data and the theoretical dispersion
modeling of toluene emission data.
10.1.1 Theoretical Modeling
The estimation of inhalation exposure to toluene among different segments
of the general population involves the following computational tasks: (1) esti-
mation of annual average toluene concentration in the air at different distances
from the emission sources and (2) estimation of the population distribution
around each source of emission (available through the U.S. Census Bureau). This
part has already been discussed in Section 7.
The performance of the first task requires the following data: (1) emission
inventories of toluene, which are already available (see Subsections 10.4.1 and
10.M.U); (2) atmospheric reactivity of toluene; (3) meteorological data, which
are available through the U.S. or local weather bureau; and (M) a dispersion
equation to estimate concentration distribution of toluene.
Toluene concentration downwind from a source can be estimated using the
following dispersion equation of Turner (1969):
C(X,0,0) = Q e*P -^—
y z w 2a
y
where
C(X,0,0) = concentration of toluene at various x coordinates and at zero y
and z coordinates (mg/mj)
Q = emmission rate (mg/s)
a = horizontal dispersion coefficient of the plume concentration
y distribution
a = vertical dispersion coefficient of the plume concentration
distribution
U = wind speed (m/s) (w = the heat of the source)
h = the effective stack height; i.e., the sum of the stack height and
plume rise (m)
10-3
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Assuming U = 5 m/s; Q = 200 x 10 kg/year = 6.3*1 x 10 mg/s; plume
height = 10 m and 20 m; and the values of a and a from the following equation
(Anderson e_t al., 1980):
-1 /?
a (m) = 0.06x(1 + 0.0015x)
z
_i /o
a (m) = 0.08x(1 + O.OOOIx) "*
one can calculate the concentration of toluene at different distances from the
source, as given in Table 10-1.
The calculations of the values in Table 10-1 for toluene distribution from a
stationary source do not consider the chemical reactivity of toluene in the
atmosphere and the effect of plume temperature on the concentration distribution
of toluene. A more detailed calculation that incroporates these two variables,
as well as building wake effect (enhanced dispersion due to buildings), has been
made for the estimation of spatial concentration of toluene from the major
stationary and mobile sources of toluene emission (Anderson £t al., 1980).
The dispersion equation developed by Anderson e_t al. (1980) was used to
compute annual average concentration pattern of toluene from each point source.
A computer program was used to evaluate these concentration patterns from the
given meteorological and emission data. Because there are numerous sources of
emission, the sources were divided into three types, which are defined below.
Specific Point Sources: These sources were treated using parameters
appropriate to each source. These sources included emissions from produc-
tion sources and from chemical intermediate users.
General Point Sources; For such sources, a prototype analysis was done
and the results were multiplied by the estimated number of sources. These
sources included emissions from gasoline marketing, from the coke-oven
industry, and from isolated and non-isolated toluene producers (not
included in the previous categories).
10-4
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Table 10-1. Concentration of Toluene (mg/m ) at Different Distances (m) From
A Source Emitting 200 Million kg/Year Toluene (Slimak, 1980)
Plume Height
(m) 100 500 1,000 1,500 5,000 10,000
10 1.36 0.45 0.15 0.12 0.02 0.01
20 0.003 0.31 0.13 0.10 0.02 0.01
10-5
-------
Area Sources; Such sources were treated as emission per unit area over
identified areas. These sources included mobile emission, emission from
solvent use, and emissions from miscellaneous sources.
The three equations used to calculate the spatial concentration distribu-
tion of toluene from all sources are given in considerable detail in Anderson
e_t ^1. (1980); interested readers are referred to that document. The final
results of the calculations of Anderson ^t _al. (1980) led to the estimate of
spatial concentration range of toluene around different sources of emissions.
These values are given in Table in Section 7.
Anderson e_t ^. (1980) listed the following factors that could cause uncer-
tainties in their calculated exposure levels given in Table 10-2:
Emission Estimates Errors; Some of these are (1) error in the esti-
mates of production and use of toluene; (2) the assumption that all plants
operate at the same capacity; (3) omission of certain emission sources;
(U) error in derivation of emission factors and, in certain cases, the use
of a uniform emission factor, which implies that all these plants have
similar emission controls. It is difficult to project whether the emission
estimates used by Anderson et al. (1980) will lead to higher or lower
exposure estimates. This can be done, however, by comparing these
estimates with the experimentally determined concentration patterns
obtained from sources that are reasonably isolated from other sources.
Concentration Pattern Errors; The concentration patterns used in the
exposure computations were obtained through atmospheric dispersion model-
ing. Any deviations in these estimates from the true pattern directly
affect the exposure results. Many assumptions were used in calculating the
concentration distribution. The exposure errors will be more severe in the
case of prototype point sources where a prototype model was used for cal
10-6
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Table 10-2. Population Distribution and Inhalation Exposure Levels of
of Toluene From Different Sources (Anderson e_t al., 1980)
Number of People Exposed From
Concentration Specific Prototype Area
Level Point Sources Point Sources Sources
(yg/m3)
>100
100 - >50
50 - >25
25 - >10
10 - >5
5 - >2.5
2.5 - >1
1 - >0.5
0.5 - >0.25
0.25 - >0.1
0.1 - 0
0
0
34
475
1,434
6,103
19,781
39,064
95,560
269,883
34,316,299
159
2,841
10,200
22,700
33,900
75,200
240,000
246,000
350,000
1,229,000
0
58 , 347
446,793
12,348,504
42,478,913
68,368,769
0
0
0
0
0
34,977,809
Subtotals 34,748,633 2,210,000 158,679,135
Total 195,637,768
10-7
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culating exposure from all other similar sources. The same can be said
about the exposure estimates from area sources where a box model method that
incorporated a number of uncertainties was used.
Interpolation Errors: The interpolation of population and concentra-
tion patterns used to develop patterns of exposure can introduce errors.
With the available information, it is not possible to quantify any of the
errors described above. The theoretical model may provide qualitative insights
in certain instances to predict whether the exposure estimate is either too high
or too low compared to the actual values.
10.1.2 Inhalation Exposure Based on Monitoring Data
Exposure of the general population to toluene by inhalation can occur under
a wide range of exposure scenarios. Because it may be considered impractical to
measure toluene concentration from all possible exposure scenarios, an attempt
has been made to develop a few of the most prevalent exposure scenarios.
The four largest sources of toluene emission, in descending order, are
automobile use (exhaust emission, engine evaporative loss, gasoline marketing
evaporative loss); industry sites using toluene as a solvent; coke oven sites,
and toluene production sites (see Subsection 10.4.4). In place of dispersion
modeling, one can use the monitoring data from each of the four sites to evaluate
the four different exposure scenarios. The difficulty with this approach is that
the available monitoring data were often developed for sites with various degrees
of intermixing between these exposure scenarios. Therefore, inhalation exposure
has been classified under three scenarios—the urban areas; areas containing the
user sites; and rural or remote areas. In this manner, the exposure estimates
developed may be representative of a broad range of the possible exposure
scenarios. It should be remembered that the urban areas may contain sites with
10-8
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high automobile use, production and other manufacturing sites, and coke-oven
sites.
Human exposure to toluene through inhalation of urban air is shown in
Table 10-3. The concentration of toluene in urban areas in the United States in
recent years ranged from 0.1 ug/nr to 204 ug/nr (see Table 7-1). The intake
estimate is based on a breathing rate of 1.2 nr/hour for an adult during waking
hours and 0.4 m^/hour during sleeping hours (Slimak, 1980). It is also assumed
that the sleeping period for an adult is 8 hours/day. This results in an
inspired volume of 1.2 x 16 x 7 + 0.4 x 8 x 7 = 156.8 m^/week.
Near user sites, the range of toluene concen-tration has been assumed to be
5.5-600 ug/m . This range corresponds to the measured value of Sexton and
Westberg (1980) near an automotive painting plant (see Subsection 7.1.1). The
concentration of toluene at a distance 18 km from the plant measured
•3
55.5 ug/nr—a value 10 times higher than the background concentration (Sexton
and Westberg, 1980). Therefore, even workers who commute more than 18 km from
the plant are susceptible to inhale toluene concentration in the range of
5.5-600 ug/m for the entire 168 hours in a week. The toluene concentrations
near manufacturing sites range from 0.1 to 147 ug/m . The estimated toluene
exposure range from the manufacturing and user sites shown in Table 10-3 is based
on a concentration range of 0.1 to 600 ug/m .
In rural and remote areas, the concentration of toluene has been reported to
be in the range of a trace to 3.8 yg/nr (see Table 7-1). These concentrations
were determined in 1971. The current level may be lower than this range as
indicated by the toluene concentration mentioned recently at Grand Canyon. The
estimated toluene exposure in rural and remote areas is shown in Table 10-3.
It should be remembered that Table 10-3 shows the amount of toluene inspired
per week by humans around certain exposure scenarios and not the amount absorbed.
10-9
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Table 10-3. Toluene Exposure Under Different Exposure Scenarios
o
i
Scenario
Observed
Range of
Concentration
Frequency
of
Exposure
Total Volume
Exposed or
Amount Consumed
Inhalation or
Ingestion Rate
(mg/wk)
General Population
Inhalation
Urban areas
Rural and remote areas
Areas near manufacturing
and user sites
Ingestion
Drinking water
Food
Occupational Group
Inhalation
Dermal
Cigarette Smokers
Inhalation
0.1-201 ug/m3
trace-3.8 ug/nr
0.1-600 ug/m3
0-19 ug/1
0-1 mg/kg
377,000 yg/m3
0-170 yg/la
0.1 mg/cigarette
168 h/wk
168 h/wk
168 h/wk
2 1/d
6.5 g/d
40 h/d
0-30 min/wk
156.8 m3
156.8 m3
156.8 m3
14 1
45.5 g
48 m3
5.9 1
20 cigarettes/d 140 cigarettes
0.02-32
trace 0.6
0.02-94
0-0.3
' 0-0.45
18,100
0-1.0
14
Abbreviations: h = hour; wk = week; d = day; rain = minute.
aThis value represents exposure to blood due to dermal contact.
-------
Only a certain fraction of the toluene inhaled is absorbed by human organs.
Also, part of the absorbed toluene is rapidly excreted from the body.
10.2 INGESTION EXPOSURE BASED ON MONITORING DATA
No theoretical modeling method is available for estimating toluene exposure
from ingestion. Therefore, the exposure estimate from this source has been
attempted by using the limited monitoring data that are available.
10.2.1 Exposure from Drinking Water
The concentrations of toluene in drinking water range from 0-19 Ug/1 (see
Subsection 7.1.2.5). The concentration of toluene measured in well waters in New
York State was below 10 ug/1 (see Subsection 7.1.-2.4). Therefore, a concentra-
tion range of 0 to 19 ug/1 has been used for exposure assessment shown in
Table 10-3. A consumption rate of 2 I/day has also been assumed for exposure
asessment.
10.2.2 Exposure from Edible Aquatic Organisms
The concentration range of toluene in edible aquatic organisms has been
assumed to be 0-1 mg/kg, based on the level of toluene found in fish tissues
(Subsection 7.1.4). On the basis of these data and the assumption that the per
capita consumption of aquatic organisms in the United States is approximately
6.5 g/day (Stephan, 1980), the exposure range of toluene from food is shown in
Table 10-3.
10.3 OCCUPATIONAL EXPOSURE
Occupational exposure to toluene can take place from two scenarios—
inhalation of air containing toluene, and skin contact with toluene or other
solvent mixtures containing toluene. The concentration of toluene in the air of
working atmosphere has been assumed to be 377,000 ug/m • This value corresponds
to the OSHA (Occupational Safety and Health Administration) recommended workroom
air standard of 100 ppm toluene vapor as a time-weighted average (TWA) exposure
10-11
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for an 8-hour work day (OSHA, 1973). Based on the above assumptions, the
inhalation exposure of toluene by occupational groups as shown in Table 10-3 far
exceeds that for any other group.
Sato and Nakajima (1978) studied the absorption of toluene through human
skin. These investigators immersed one hand of 5 male subjects in pure toluene
for 30 minutes and monitored the blood levels of toluene. A peak concentration
of 170 Ug/1 of blood was observed after a 30-minute immersion. This maximum
concentration was maintained for 10-15 minutes after exposure had ended and
decreased thereafter.
Although the standard set forth by OSHA (19730 requires all workers handling
toluene to wear gloves, it is conceivable that short-term exposure of bare skin
to toluene takes place under certain circumstances. For assessment of exposure
through skin as shown in Table 10-3, a maximum concentration of 170 ug/1 in blood
and a blood volume of 5.9 1 for an adult male have been assumed. It has also been
assumed that the skin exposure duration does not exceed 30 minutes/week. It
should also be recognized that the value for blood concentration through dermal
contact given in Table 10-3 does not represent the total exposure value as it
ignores exposure to other organs.
10.4 CIGARETTE SMOKERS
The concentration of toluene in inhaled cigarette smoke has been determined
to be 0.1 mg/cigarette (see Subsection 7.3). In assessing toluene exposure from
cigarette smoking, it was assumed that an individual smokes 20 cigarettes (per
pack) per day. On the basis of these assumptions, it can be predicted from
Table 10-3 that cigarette smoking may be the second largest source of human
exposure to toluene.
10-12
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10.5 LIMITATIONS OF EXPOSURE ASSESSMENT BASED ON MONITORING DATA
As discussed earlier, exposure assessment on the basis of monitoring data
has the following limitations:
(1) The limited monitoring data do not provide information
for estimating exposure under different exposure
scenarios. Even when some data are. available, they may
be inadequate and even susceptible to error. It is very
difficult to assess the errors in the monitoring data.
(2) The monitoring data often do not relate to the source of
emissions in terms of material balancing of the amount
emitted and the concentration measured.
(3) The population distribution around the monitoring area is
rarely provided in these data.
(4) The estimate for toluene exposure to the general popula-
tion from food and drinking water as given in Table 10-3
is very crude. Toluene has been detected in only a small
fraction of total drinking water supplies monitored (see
Subsection 7.1.2.5). The exposure estimate does not
specify either the number of people or the locations
where people are exposed to toluene from drinking water.
The same can be said with respect to toluene exposure
from food.
10.6 COMPARISON BETWEEN EXPOSURE DATA BASED ON THEORETICAL
AND EXPERIMENTAL VALUES
If the concentration values ranging from 0 vig/m to greater than 100 ug/nr
are combined with the value of 156.8 nr for inspired volume of air per week, an
inhalation exposure estimate as shown in Table 10-4 can be developed.
A comparison of inhalation exposure data shown in Table 10-4 which are based
on dispersion equations, with inhalation exposure data in Table 10-3, which are
derived from monitored concentrations, shows reasonable agreement between the
two sets of data. The monitoring data estimate toluene inhalation by the general
population in urban areas to be 0.02-32 mg/week. The exposure data developed
from dispersion equations estimate this value to be in the range of zero to
greater than 15.7 mg/week.
10-13
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Table 10-4. Exposed Population and Exposed Amount of Toluene
From Dispersion Modelling (Slimak, 1980)
Concentration
Level . Exposed Concentration
(ug/nr) rag/week
>100 >15.7
100-10 15.7-1.6
10-1 1.6-0.15
1-0.1 0.15-0.02
0.1-0 0.02-0
10-14
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11. EFFECTS ON HUMANS
Exposures of humans to toluene have almost exclusively involved inhalation,
and the effect of greatest concern is dysfunction of the central nervous system.
The exposures may be classified into three groups: occupational exposures,
experimental studies and deliberate inhalation of toluene or toluene-containing
substances ("glue sniffing"). It should be noted that occupational exposures and
glue sniffing often involve complex mixtures of solvents, and that in the older
studies, benzene was a common contaminant to toluene. In evaluating the effects
of toluene exposures, the purity of the compounds used must be considered.
Glue sniffers inhale the vapors from a wide variety of volatile hydrocarbons
(usually poorly defined mixtures) contained in products such as glues and
thinners for their euphoric or intoxicating effects. The most popular of these
products contain toluene, and toluene is the hydrocarbon most frequently impli-
cated as the cause of the adverse effects associated with deliberate inhalation.
The practice has been extensively reviewed (Massengale, 1963; Barman et aj,.,
1964; Press and Done, 1967a, 1967b; Gellman, 1968; Wyse, 1973; Linder, 1975;
Faillace and Guynn, 1976; Oliver and Watson, 1977; Walter .et .al., 1977; Watson,
1979). Excessive levels of toluene are generally inhaled over a short time
interval, and repeated inhalation of the vapors is associated with the develop-
ment of tolerance and psychological dependence. The most common methods of
inhalation involve (1) placing the solvent in a plastic bag and inhaling the
fumes, (2) soaking a rag or handkerchief with the solvent and sniffing the rag,
or (3) sniffing the solvent from a container. The concentrations of toluene
inhaled under these conditions can approach 30,000 ppm (i.e., saturation concen-
tration at 20°C), and may be regarded as a type of maximum tolerated dose.
11-1
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11.1 EFFECTS ON THE NERVOUS SYSTEM
11.1.1 Central Nervous System
11.1.1.1 Acute Effects
Experimental exposures of up to 800 ppm toluene have produced acute dose-
related symptoms of central nervous system .(CNS) depression (Von Oettingen
.et al., 1942a, 1942b; Carpenter et al., 1914). Von Oettingen et al. (1942a,
1942b) provided what is generally acknowledged to be the most complete descrip-
tion of the effects of pure toluene (benzene <_ 0.01$) on the CNS. In single 8-
hour exposures, 3 human subjects were subjected to concentrations of toluene in
an exposure chamber that ranged from 50-800 ppm (Table 11-1). A maximum of two
exposures a week were performed over an 8-week period, and a number of these
exposures were to pure air; exposures to the different levels of toluene were
replicated only 1 to 4 times within the 8 weeks. The effects that were observed
are also summarized in Table 11-1. Subjective complaints such as fatigue, mus-
cular weakness, confusion, impaired coordination, and enlarged pupils and accom-
modation disturbances were reported at levels of 200 ppm. These effects
increased in severity with increases in toluene concentration, until at 800 ppm
the subjects experienced severe fatigue, pronounced nausea, mental confusion,
considerable incoordination and staggering gait, strongly impaired accommodation
to light, and after-effects (muscular fatigue; nervousness and insomnia) that
lasted for several days.
Carpenter and coworkers (1944) exposed 2 male subjects to known concen-
trations of toluene (purity not stated) for periods of 7 to 8 hours and noted
slight exhilaration at 200 ppm, and lassitude, nausea, and hilarity at 400 ppm.
Lassitude, hilarity, verbosity, and boisterousness occurred at 600 ppm (anorexia
and listlessness were reported as after-effects), and transitory headaches,
extreme lassitude, scotomata (areas of depressed vision), verbosity, slight
11-2
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Table 11-1. Effects of Controlled 8-hour Exposures to Pure Toluene on
Three Human Subjects3 (Von Oettingen et al., 1942a, 19425)
Concentration No. of Effects
Exposures
0 ppm (control) 7 No complaints or objective symptoms, except occasional
moderate tiredness toward the end of each exposure,
which was attributed to lack of physical exercise,
unfavorable illumination, and monotonous noise from
fans.
50 ppm 2 Drowsiness with a very mild headache in 1 subject. No
aftereffects.
100 ppm 4 Moderate fatigue and sleepiness (3), and a slight
headache on one occasion (1).
200 ppm 3 Fatigue (3), muscular weakness (2), confusion (2),
impaired coordination (2), paresthesia of the skin
(2), repeated headache (1), and nausea (1) at the end
of the exposure. In several instances the pupils were
dilated, accommodation to light was impaired, and the
fundus of the eye was engorged. Aftereffects included
fatigue, general confusion, moderate insomnia, and
restless sleep in all 3 subjects.
300 ppm 2 Severe fatigue (3), headache (2), muscular weakness
and incoordination (1), and slight pallor of the
eyeground (2). Aftereffects included fatigue (3) and
insomnia (1).
400 ppm 2 Fatigue and mental confusion (3), headache,
paresthesia of the skin, muscular weakness, dilated
pupils, and pale eyeground (2). Aftereffects were
fatigue (3), skin paresthesia (1), headache (1), and
insomnia (2).
600 ppm 1 Extreme fatigue, mental confusion, exhilaration,
nausea, headache and dizziness (3), and severe
headache (2) after 3 hours of exposure. After 8
hours' exposure, the effects included considerable
incoordination and staggering gait (3), and several
instances of dilated pupils, impaired accommodation
and pale optic discs; aftereffects included fatigue
and weakness, nausea, nervousness and some confusion
(3), severe headache (2), and insomnia (2). Fatigue
and nervousness persisted on the following day.
800 ppm 1 Rapid onset of severe fatigue and, after 3 hours,
pronounced nausea, confusion, lack of self-control,
and considerable incoordination and staggering gait in
all 3 subjects. Also, accommodation to light was
strongly impaired (1) and optic discs were pale (2).
All 3 subjects showed considerable aftereffects,
lasting at least several days, which included severe
nervousness, muscular fatigue, and insomnia.
aExposures were twice weekly for 8 weeks. The number of subjects affected
is noted in parentheses.
. 11-3
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nausea, and "inebriation" were found at 800 ppm. Marked unsteadiness was also
observed in the subjects during exposure to 800 ppm toluene. Steadiness was
determined by a test that involved holding at arms' length a wire in a hole for 3
minutes; the percentage of time the wire was actually in contact with the side of
the hole was determined, and compared with the normal value from each test
session.
Short-term experimental exposures to toluene have also elicited increases
in reaction time and reductions in perceptual speed (Ogata e_t al., 1970;
Gamberale and Hultengren, 1972). Ogata and coworkers (1970) reported that 23
Japanese subjects given single exposures to 200 ppm toluene showed a prolon-
gation of eye-to-hand reaction time, but no effect on flicker fusion frequency.
Exposures were for 3 hours, or 3 hours and a 1-hour break period followed by 4
additional hours of exposure. No changes in either reaction time or flicker
value were obvious at 100 ppm. It should be noted, however, that no other
information regarding the design of these experiments was presented.
In a more extensive study, Gamberale and Hultengren (1972) exposed 12 male
subjects to 100, 300, 500, or 700 ppm toluene (via breathing valve and mouth-
piece) during successive 20-minute exposure periods, and measured their perfor-
mance on four tests of perceptual speed and reaction time at each level of
exposure (Table 11-2). The tests were always made in the same sequence (i.e.,
Identical Numbers, Spokes, Simple Reaction Time, Choice Reaction Time) during
the final 15 minutes of each exposure period. Toluene concentrations were
increased from 100 to 300 ppm and from 500 to 700 ppm without interruption, but
the increase from 300 to 500 ppm was made following a 5-minute interval without
exposure. Menthol crystals contained in the mouthpiece tubing camouflaged the
taste and the smell of the toluene. The 12 subjects were divided into two groups
of equal size: subjects in one group were studied individually, first under
-------
Table 11-2. Effect of Toluene Exposure on the Performance of Perceptual
Speed and Reaction Time Tests (Gamberale and Jultengren, 1972)
Mean Teat Scorea
Performance Teat
Identical Numbers'1
(minutes)
Spokesc
(seconds)
Reaction- Time - Simple
(meters/second)
Reaction Time - Choice6
(meters/second)
Concentration
(ppm)
100
300
500
700
100
300
500
700
100
300
500
700
100
300
500
700
' Experimental
Conditions
5.62
5.25
5.13
5.19
50.5
46.7
43.6
45.4
228
236
246
253
425
429
432
442
• Control (Air)
• Conditions
5.53
5.29
5.04
4.80
50.8
43.7
40.2
- 36.9
230
222
219
214
422
416
400
408
t.-Value
+0.50
-0.39
+1.34
+2.65f
-0.08
+ 1.18
+ 1.28
+2.51*
-0.31
+2.35»
+3.88"
+4.81"
+0.34
+1.99
+2.91*
+3.59"
Degrees of freedom s 11; *P < 0.05; »*P < 0.01; «*P < 0.001
12 male subjects were exposed to toluene concentrations of 100, 300, 500, and 700 ppm duping-four successive
20-minute periods. The tests were performed at each concentration sequentially in the order listed. The number
of times each test sequence was repeated was not stated.
Perceptual speed: Identical Numbers. Subjects were instructed to underline the 3-digit number , from a
total of 60 columns, that was identical to the number at the head of each column. Performance was measured as the
time taken to complete the test.
Perceptual speed: Spokes. Subjects were instructed to connect circles located at random on four pages and
numbered from 1 to 20 in the correct numerical order using a pen. Performance was measured as the mean time taken
for the four assignments.
Simple Reaction Time. Subjects were instructed to respond to a signal from a lamp by pressing a pushbutton.
Stimuli were administered at intervals of approximately 10 seconds, an acoustic warning signal was given 3 seconds
prior to onset of stimuli, and 30 stimuli were given in each trial. Performance was measured as the mean reaction
time for the last 20 stimuli administered.
Choice Reaction Time: Stimulus/reply test as above, but there were three pushbuttons equipped with
matching stimulus lamps. Stimulus administration followed a random sequence with the number of light signals
evenly distributed among the lamps, but the trial and performance measurements were otherwise the same as for
simple reaction time.
11-5
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experimental conditions with exposure and then under control (atmospheric air
containing menthol) conditions 7 days later, and subjects in the other group were
studied under similar conditions but in the reverse order. The camouflage of the
inspiratory air with menthol made it impossible for 11 of the 12 subjects to
distinguish between exposure to toluene and exposure to pure air.
Results of the Gamberale and Hultengren (1972) study showed that both reac-
tion time and perceptual speed were impaired during exposure to toluene as
compared to exposure to pure air (Table 11-2). With respect to reaction time, a
significant effect was noted upon exposure to 300 ppm toluene in one test (Simple
Reaction Time), and a performance decrement which reportedly approached statis-
tical significance at the 0.05 level was noted for the other test (Choice Reac-
tion Time). Subject reaction time was further impaired at higher levels of
exposure (500 and 700 ppm toluene), but no impairment in either reaction time
test was noted for exposure to 100 ppm. (The 100 ppm reaction time no-effect
level is consistent with the aforementioned results of Ogata j^t _al., 1970.) No
statistically significant impairment in subject perceptual speed was observed
until the concentration of toluene in the inspiratory air was 700 ppm. Because
perceptual speed was unaffected at concentrations below 700 ppm, the authors
suggested that the simpler CNS functions may be affected at lower levels of
toluene exposure than the more complex functions.
Wineke et al. (1976) noted, in the Proceedings of the 2nd International
Industrial and Environmental Neurology Congress (Prague, Czechoslovakia), that
experimental exposure to 98 ppm toluene for 3 hours did not affect psychophysio-
logical performance in 20 subjects. The parameters evaluated in this study
included performance in a bisensory (auditory and visual) vigilance task,
psychomotor performance, critical flicker frequency, and auditory evoked poten-
tials. It should be noted that the available meeting abstract did not provide
11-6
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any additional information on the experimental design, the nature of the psycho-
physiological tests, or the results of this study.
Gusev (1965) examined the effects of acute low-level toluene exposure on the
electroencephal©graphic (EEC) activity of ^ human subjects who were trained to
develop synchronous and well-marked alpha rhythms when stimulated by light.
Toluene exposures of 1 mg/nr (approximately 0.27 ppm) for 6 minutes were
reported to cause statistically distinct changes in EEC activity from the left
temporal-occipital region in all subjects; these changes persisted through a
6-minute recovery period. It should be noted that the 1 mg/nr concentration is
slightly lower than the odor threshold determined" for toluene in the same experi-
ment (1.5 mg/m , see subsection 11.7.2). Toluene concentrations of 0.6 mg/m
caused no variations in the electric potentials of the EEGs. Exposure sessions
consisted of 10 separate observation periods in which inhalation of toluene
(5 periods) alternated with inhalation of pure air (5 periods). A single period
consisted of 18 one-minute cycles. Every cycle included the sequential presenta-
tion of a sound stimulus (10 seconds), a wait for the light stimulus (7 seconds),
the presentation of the light stimulus (18 seconds), and an interval of active
physical exercise (25 seconds) for recovery of normal EEC rhythm. Of the
18 minutes allotted for EEG recording in each period, 3 minutes were used for
training, the next 3 minutes for background observations, the following
6 minutes for the toluene exposure, and the final 6 minutes for recovery. It
should be noted that no other studies have reported any effect on the CNS at such
low levels of exposure, and that the purity of the toluene used was not stated.
Narcosis is the primary result of acute toluene exposure at high concentra-
tions. A number of accounts of workers who were rendered unconscious by toluene
vapor have been published in the medical literature (Lurie, 19^9; Andersen and
Kaada, 1953; Browning, 1965; Longley .et.al., 1967; Reisin e_t _aL., 1975). Most of
11-7
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these cases have involved the entry of workmen into confined areas with poor
ventilation and subsequent exposure to high levels of toluene during maintenance
operations. Longley £t al. (1967) described two episodes of acute toluene
intoxication involving 26 men who were exposed in the holds of cargo ships.
Toluene concentrations were estimated to .have.ranged from 10,000 ppm at waist
level to 30,000 ppm at floor level, but it was emphasized that this estimate was
purely conjectural. Effects at these concentrations ranged from exhilaration,
lightheadedness, and cluminess and dizziness to collapse and unconsciousness.
No deaths occurred and recovery was quite rapid, with no after-effects following
removal from the contaminated atmosphere. The durations of the exposures were
not indicated, but loss of consciousness occurred within minutes.
Episodes of toluene abuse are characterized by the progressive development
of CMS symptoms. Toluene sniffers experience an initial excitatory stage that is
typically characterized by drunkenness, dizziness, euphoria, delusions, nausea
and vomiting, and, less commonly, visual and auditory hallucinations (Press and
Done, 196?a, 1967b; Wyse, 1973; Lewis and Patterson, 1974; Hayden et ^L., 1977;
Oliver and Watson, 19775 Barnes, 1979). As duration of exposure increases,
symptoms indicative of CNS depression become evident: confusion and disorienta-
tion, headache, blurred vision and reduced speech, drowsiness, muscular incoor-
dination, ataxia, depressed reflexes, and nystagmus. In extreme cases, loss of
consciousness, possibly with convulsions (Helliwell and Murphy, 1979), occurs.
The duration and severity of these effects vary greatly, depending upon the
intensity of exposure; the duration may range from 15 minutes to a few hours
(Press and Done, 1967b). Also, not all of the symptoms described are exhibited
in any single sniffer, nor in any single episode of sniffing.
Winek e_t al. (1968) published partial results of an autopsy on an adolescent
who had died as a result of sniffing toluene-containing model airplane glue. At
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autopsy the cut surfaces of the lungs of this individual were found to be
extremely frothy and congested, with diminished amounts of crepitation through-
out the lung tissue. Other gross observations that were noted included some
petechial hemorrhages in the larynx and upper trachea, firmness and congestion in
the spleen, and a dark red brown color and congestion in the liver. No hemor-
rhages, obstructions, or ulcerations were seen anywhere in the gastrointestinal
tract, and all other organs were unremarkable. The results of toxicological
analyses of various body tissues for toluene are presented in Section 12.2.
Congestion in various organs, swelling of the brain, subseromucous petechiae,
and pulmonary edema were associated with 19 other cases of acute death from
thinner intoxication (Chiba, 1969). The English abstract of this Japanese study
indicated that toluene was the major component of the inhaled thinner. Nomiyama
and Nomiyama (1978) described an instance in which 4 adolescents were found dead
after sniffing 99% pure toluene in a car, but post-mortem results other than
levels of toluene (blood and alveolar air) and hippuric acid (urine) were not
presented. Sudden death due to solvent sniffing has been reported in at least
122 cases (Bass _et al., 1970; Alha et al., 1973). These deaths have been
attributed to severe cardiac arrhythmia, and are discussed in subsection 11.5
(Effects on the Heart).
11.1.1.2 Subchronic and Chronic Effects
Wilson (19^3) described the effects of exposure to commercial toluene vapor
on 100 workers (out of a total of 1000 workers) who showed symptoms severe enough
to cause them to present themselves to a hospital for examination. The workers
were exposed daily to toluene concentrations ranging from 50-1500 ppm for
periods of 1 to 3 weeks, but the composition of the commercial formulation and
the type of industry were not described. Also, it is unclear whether the
remaining 900 workers evidenced any symptoms of toluene exposure. The
11-9
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concentration of toluene was determined shortly after any exposed person
appeared at the hospital with symptoms, and the patients were classified into
groups by degree of exposure. The following effects were reported:
50 to 200 ppm (approximately 60% of the patients) - headache, lassitude,
and loss of appetite. These symptoms were so mild that
they were considered to be due primarily to psychogenic
and other factors rather than to toluene fumes.
200 to 500 ppm (approximately 30$ of the patients) - headache, nausea,
bad taste in the mouth, anorexia, lassitude, slight but
definite impairment of coordination and reaction time,
and momentary loss of memory.
500 to 1500 ppm (approximately 10$ of the patients) - nausea, headache,
dizziness, anorexia, palpitation,"and extreme weakness.
Loss of coordination was pronounced and reaction time
was definitely impaired.
Characteristic CNS symptoms have been described in foreign reports of
workers exposed for longer durations to moderate levels of toluene. Parmeggiani
and Sassi (1954) found signs of "nervous hyperexcitability" in 6 out of 11 paint
and pharmaceutical industry workers who were exposed to 200-800 ppm toluene
vapor for "many" years. Capellini and Alessio (1971) noted symptoms of stupor,
nervousness, and insomnia in 1 worker who was employed for "diverse" years in
preparing a toluene-containing mixture for use in the manufacture of V-belts.
The mean atmospheric concentration of toluene in the mixing department was
250 ppm, with extremes of 210 ppm and 300 ppm. No CNS effects were observed,
however, in 17 other workers who were exposed to 125 ppm toluene (range, 80-
160 ppm) while engaged in the manufacture of the belts.
In a more extensive study, Suhr (1975) found no evidence of adverse neuro-
logical effects in a group of 100 rotogravure printers with at least 10 years of
exposure to 200-400 ppm pure toluene (
-------
and abnormal Sphallograph test results were not found to occur significantly more
often in the printers than in an unexposed control group of equal size. The
Sphallograph is an instrument that is used to detect slight disturbances of
muscular coordination by sensing variations in the balance of two metal plates; a
test person stands on the plates, and balance disturbances are detected by strain
gauges.
The Suhr (1975) conclusion that chronic occupational exposure to 200-
HOO ppm toluene did not cause adverse neurological effects in the rotogravure
workers is equivocal for several reasons. First, the nature of the control group
used in this study is not defined, other than that they "were from the same firm
and not exposed to toluene." Additionally, the worker and control groups were
only roughly matched by groups for age distribution, years of exposure, and
nature of workshift (i.e., 2- or 3-shift work). Second, the venous blood levels
measured in the printing room workers at the end of their shifts indicate expo-
sure to toluene levels of at least 300 ppm and possibly as high as 600 ppm.
These levels are consistent with the reported air concentration measurements,
which ware made with a "measuring cell" device. It is not clear, however, when
workers were examined for reflex reactions and Sphallograph measurements. If it
was after or before the workshifts (as the data for the 33 Sphallograph groups
would indicate), then blood levels of toluene may have declined significantly.
Astrand et al. (1972) have shown major drops in levels within minutes after the
removal of human subjects from exposure. Third, the Sphallograph appears to be a
very infrequently used device in the United States; several behavioral toxicolo-
gists who were contacted by Syracuse Research Corporation (SRC) indicated that
they have never heard of the instrument, and the device does not appear to have
been described in standard texts. Suhr (1975) also cites the work of Pohl and
Schmidle (1973), who tested the effects of "extreme" concentrations of 11 fre
11-11
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quently used organic solvents in humans with the Sphallograph and found only
minimal effects. This would argue that the Sphallograph is not a sensitive test
for determining CNS effects of solvents. Last, until more is known concerning
the exposures of the control group, the significance of the reportedly negative
results of the subjective symptom survey is questionable.
Chronic occupational exposure to toluene has also been associated with
behavioral changes. Munchinger (1963) diagnosed an "organic psychosyndrome" in
21$ of a group of printers exposed on the average to 300 ppm toluene for 18 years
(mean age, 42 years), and in 40$ of a group of printers' helpers exposed to
430 ppm for 12 years (mean age, 44 years). The" tests involved a total of 110
workers, but testing on control subjects was not performed. This syndrome was
characterized by subjective memory, thinking, and activity disturbances.
Results of the Rorschach testing were consistent with the psychosyndrome diagno-
sis in 83$ of the cases. The Rorschach test and Knoepfel's 13-Error Test results
in combination agreed with the diagnosis in 95$ of the cases.
More recently, several groups of investigators have shown that long-term
exposure to combinations of toluene and other common organic solvents caused
impairments in visual intelligence and psychomotor performance of workers. In
1973, Lindstrom compared the psychological test performances of a group of 168
male workers who had been exposed to hydrocarbon solvents for 0.1-30 years (mean,
6 years) to those of an unexposed control group (N = 50). Twenty-six of the
workers had been exposed primarily to toluene and 25 to a combination of toluene
and xylene; the other workers (numbers in parentheses) were exposed primarily to
trichloroethylene (44), tetrachloroethylene (8), "thinners" (44), and miscel-
laneous solvents (21). Exposure concentrations were not reported. Results
showed that the solvent-exposed workers were inferior in performance to the
11-12
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controls in sensorimotor speed performance, psychomotor performance, and visual
accuracy as determined by standardized test procedures (e.g., Bourdon-Wiersma
vigilance test, Santa Ana dexterity test, Mira psychomotor test). The perfor-
mance of the workers on the Rorschach personality test was comparable to that of
the control group.
Hanninen jit _aL. (1976) compared the behavioral responses of a group of 100
car painters with those of 101 age-matched nonexposed subjects. The painters
(mean age 35 ^ 11 years) were exposed to different organic solvents for 1 to
40 years (mean, 14.8 ± 8.5 years), but, as detailed in Table 11-3, toluene was
present in the greatest amount (30.6 ppm). A battery of tests included one test
for verbal intelligence, three visual tests, five memory or learning tasks, four
tests of psychomotor performances, and the Rorschach test for measuring per-
sonality changes (Tables 11-4 and 11-5). Results of this study showed signifi-
cant differences between the exposed and reference group in almost all intel-
lectual performances and memory tasks. Impairments in visual and verbal intel-
ligence and in memory as well as a reduction of emotional reactivity as indicated
by the Rorschach test were the predominant effects of solvent exposure
(Tables 11-4 and 11-5). Differences in psychomotor performances between the
exposed and control subjects were less consistent; impairments were seen only in
some of the Santa Ana dexterity and finger tapping test scores, and reaction
times were unaffected by exposure. It should be noted that in other studies,
reaction time increased as a result of acute (Ogata _et _al., 1970; Gamberale and
Hultengren, 1972) and subchronic (Wilson, 1973) exposures to toluene concentra-
tions in excess of 200 ppm. The possible influence of differences in initial
intelligence levels on the performance scores was controlled in the Hanninen
j3t _ajL. (1976) study by a separate comparison of the test results of 33 pairs of
exposed and unexposed subjects who were matched for age and for intelligence.
11-13
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Table 11-3. Mean Concentrations of Organic Solvents in the
Breathing Zone of 40 Car Painters (Hanninen
et aL.f 1976)
Mean
Solvent Concentration
(ppm)
Toluene 30.6
Xylene 5.8
Butyl Acetate 6.8
White Spirit 4.9
Methyl Isobutyl Ketone 1.7
Isopropanol 2.9
Ethyl Acetate 2.6
Acetone 3-1
Ethanol 2.9
Sampling Period = 1 hour; Number of Car Repair
Garages = 6; Number of Samples = 54.
11-14
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Table 11-4. Performance Tests: Means, Standard Deviations, and Significance
Between the Group Means (Age-Matched) Groups (Hanninen et al.,
1976)
Means and Standard Deviations
Teat
WAISa Similarities testb
WAIS Picture Completion0
WAIS Block Designd
Figure Identification6
WAIS and WMSfDigit Span8
WHS Logical Memory11
WMS Associate Learning
Benton Test for Visual Reproduction
Benton Test for Visual Retention
SADT - right hand^
SADT - left handj
SADT - coordination with both hands^
Finger Tapping - right hand11
Finger Tapping - left hand14
Reaction Time (Simple) - right hand
Reaction Time (Simple) - left hand
Reaction Time (Choice)
Mira Test1
Mira Test1
Exposed (N = 100)
19.4 +
14.9 +
34.6 *
32.0 +
10.6 r.
11.7 +
. 15.3 ±
21.1 +
8.2 ±
44.7 +
42.3 ±
29.0 +
202.5 *
186.7 +
12.4 +
12.1 +
9.1 +
18.8 +
2.2 +
3.1
2.9
7.0
9.0
1.6
3.7
3.6
3.1
1.5
5.7
5.4
5.4
29.2
28.5
2.9
3.0
1.8
3.8
1.0
Nonexpoaed (H = 150)
2.9
16.2
39.6
36.7
11.5
13.9
17.1
22.6
8.7
47.5
U3.6
31.5
209.6
196.4
11.9
11.7
9.1
20.3
2.0
* 2.1
* 2.3
* 5.6
t 9'.8
+ 1.8
t 3.1
+ 2.6
± 2.3
+ 1.3
+ 5.8
± 5.1
* 5.7
+ 23.8
+ 22.4
± 1-"
* T-"
+ 1.2
* 4.6
+ 0.8
Significance
of Differences
(t-teat)
•i*
*••
*••
•••
*••
•••
>•*
••*
i
•*
*•
i
••o
*
»P < 0.05; "P < 0.01; »"P < 0.001
aWechsler Adult Intelligence Scale.
Measures verbal intelligence and abstraction.
°Measures visual intelligence and observation.
Measures visual intelligence and abstraction.
eMeasures speed of perception and memory for visual details.
Wechsler Memory Scale.
8Measures memory for digits.
'Pleasures verbal memory.
Measures verbal memory and learning.
•^Santa Ana Dexterity Test; measures psychomotor speed.
if
Measures motor speed.
Test for psychomotor behavior and psychomotor ability; two variables tested.
"Paired £-test.
11-15
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Table 11-5. Rorschach Personality Test Variables: Means, Standard Deviations, and
Significances Between the Group Means (Age-Matched Groups) (Hanninen e_t al.. 1976)
Variable
Means and
Exposed (N = 100)
Standard Deviations
Nonexposed (N = 101)
Significance
of Differences
(t-test)
Number of responses
Number of rejections
Average latency time of responses
Adaptability
Emotionality
Spontaneity
Rational self-control
Originality of perception
Hostility
Anxiety
Bodily Preoccupation
13.6 + 6.4
0.7 ± 1.1
16.4 + 8.5
11.6 + 3.1
8.8 ± 3.3
11.8 + 2.4
8.6 + 2.8
1.6 + 1.7
1.6 + 1.6
3.9 ± 2.0
0.4 + 0.8
13.8 + 4.5
0.4 + 1.0
16.5 ± 8.1
12.1 + 3.1
10.4 + 3.2
11.9 ± 2.6
7.3 +2.8
1.5 ± 1.2
2.4 + 1.7
3.8 + 2.2
0.8 + 1.1
"3
""
...b
...
.a
«P < 0.05; «*P < 0.01; *««P < 0.001
Paired Chi Square-test for dichotomized scores.
^Paired t-test.
-------
In a related study, Seppalainen et al. (1978) examined the same cohort of
car painters studied by Hanninen and coworkers (1976) for neurophysiological
effects. Results of EEC analysis on 102 solvent-exposed car painters and 102
nonexposed control subjects showed no increase in abnormalities (abnormal EEGs
were encountered in 32 painters and 37 controls). It was noted, however, that
the incidence of abnormal EEGs in both groups was higher than expected (approxi-
mately 10/6) on the basis of EEC literature. It was further reported that 26 of
the car painters had a complex of four subjective symptoms indicative of CNS
disturbance (interrupted sleep, absentmindedness, easy to fall asleep when
watching television, frequent headaches); this symptom complex was found only in
12 controls. EEG testing on the workers with these symptoms showed abnormalities
in 46$ (12/26) of the cases, but 26% (20/76) of those without the symptom complex
also displayed EEG abnormalities. This difference was not statistically signi-
ficant (Chi squared = 2.68)
Rouskova (1975) did observe changes in EEG response to photic stimulation in
a group of 20 workers with a 13.5-year (average) history of exposure to higher
concentrations of toluene (>250 ppm) and 1,1,1-trichloroethane (concentration
not stated). Photic stimulation was applied in a series of rhythmic flashes,
each lasting 10 seconds with intervals of 10 seconds between each flash series;
frequences ranged from 1 to 30 per second. Evaluated as a normal response was
the occurrence of EEG activity of the same frequency as stimulation or of a
harmonic or a subharmonic multiple of that frequency lasting at least 1 second.
Results showed that abnormal EEG responses were found in 18 of the 20 workers
(90$), but in only 1 of 20 unexposed control subjects.
Residual effects indicative of cerebellar and cerebral dysfunction have
been observed in a number of persons who had abused toluene or solvent mixtures
containing toluene over a period of years (Grabski, 1961; Satran and Dodson,
11-17
-------
1963; Knox and Nelson, 1966; Kelly, 1975; Boor and Hurtig, 1977; Weisenberger,
1977; Keane, 1978; Sasa et aL., 1978; Tarsh, 1979; Malm and Lying-Tunell, 1980).
Boor and Hurtig (1977) also described a case of cerebral involvement in an
optician who regularly used toluene occupationally to clean eyeglasses and
contact lenses in a small, unventilated room. Clinical signs in these indivi-
duals included ataxia, intention tremors, nystagmus, equilibrium disorders,
positive Babinski reflex, impairment of speech and hearing, reduced vision,
disturbance of concentration and memory, emotional lability, and psychosis.
These reports, which are summarized in Table 11-6, indicate that the severity of
the encephalopathic effects generally varied with the intensity and duration of
exposure and that the effects were largely reversible, particularly when the
exposures were not too extreme. Prolonged toluene abuse had, however, on occa-
sion led to permanent encephalopathy and brain atrophy as evidenced by EEC and
neuroradiological (pneumoencephalogram, angiogram) changes (Knox and Nelson,
1966; Boor and Hurtig, 1977; Sasa^t^l., 1978).
11.1.2 Peripheral Nervous System
Matsushita £t jl. (1975) found evidence of peripheral neuropathy in a group
of 38 female shoemakers (mean age 20.7 ± 5.2 years) who had been exposed to a
glue containing mainly toluene and "slight" gasoline for an average duration of
3 years and 4 months. The results of neurological and muscular function tests
reportedly showed abnormal tendon reflexes, reduced grasping power of the domi-
nant hand, and decreased finger tapping tempo in the exposed workers relative to
a group of 16 unexposed control women (Table 11-7), but descriptions of the tests
were not provided. A significant decrease in finger agility was also noted in
the exposed shoemakers; agility of the fingers was estimated by measuring the
time needed to move 25 "bulbs" using glass chopsticks. The average toluene
concentration in the air varied with time of year from 60 to 100 ppm (range 15-
11-18
-------
Table 11-6. Encephalopathic Effects of Chronic Toluene Abuse
Subject (Age)
Exposure History
Effects and Diagnosis
Reference
Male (33 years)
Male (30 years)
Female (19 years)
Male (25 years)
Regularly sniffed toluene for 11 years.
Subject purchased a gallon of pure
toluene every 4-6 weeks, and inhaled the
toluene on an almost daily basis at fre-
quent Intervals throughout the day.
10-year history of toluene abuse.
Almost daily sessions of prolonged paint
sniffing for 1-1/2 years. Ingredients
not specified but it was indicated that
toluene was a common ingredient in all
the brands sniffed. Previous M-year
history of multiple drug and solvent
abuse.
10-year history of lacquer thinner (99$
toluene) abuse; during the last 5 years he
had spent virtually all his waking hours
inhaling the vapors (1 gallon used every
2 weeks)
Patient initially examined after 6 years by
Grabskl; signs included ataxia, intention
tremors, pyramidal signs and psychosis which
were concluded to be consistent with cerebellar
degeneration. After 8 more years of abuse, Knox
and Nelson reexamlned the patient and concluded
that the syndrome was primarily a diffuse
cerebral disorder based on findings of ataxia,
tremors, limb incoordination, emotional lability,
marked snout reflex, and positive Babinski toe
reflex; cerebral atrophy was confirmed by EEC
and pneuraoencephalography.
Recurrent headaches, "inappropriate" speech,
brief episodes of memory loss, Increased
irritability, and exaggerated swings in mood.
Unremarkable clinical and neurological exam,
but nonspecific EEC changes were found that
were regarded as consistent with diffuse
encephalopathy.
Ataxia, intention tremors of hands and feet,
incoordination, hallucinations. Normal EEC,
brain scan, arterlography, and pneumoencephalo-
graphy. The diagnostic impression was
cerebellar dysfunction secondary to sorte toxic
factor in the paint. Objective neurological
Improvement 5 months after sniffing was
discontinued.
Ataxia, mildly slurred speech, nystagmus, and
bilateral Babinski signs. Normal EEC, nuclide
brain scan, electromyogram, and nerve conduction
studies, but a computerized brain scan showed
diffuse widening of the cortical and cerebellar
sulci. Subjective Improvement in condition
following abstinence from exposure, but a
neurological exam after 9 months was
essentially unchanged.
Orabski, 1961;
Knox and Nelson, 1966
Satran and Dodson, 1963
Kelly, 1975
Boor and Hurtig, 1977
-------
Table 11-6. Encephalopathic Effects of Chronic Toluene Abuse (Cont.)
Subject (Age)
Exposure History
Effects and Diagnosis
Reference
Male (59 years)
Male (age not stated)
Male (27 years)
Male (20 years)
Male (25 years)
Female (18 years)
Optician who frequently but inter-
mittently used 994 toluene in a small
unventllated room to clean eyeglasses
and contact lenses. Unable to smell
toluene because of chronic anosmia.
Duration of exposure not stated.
Habitual inhalation of paint thinner
(toluene) on the job. Duration not
stated.
Sniffed unspecified glues and paint
thinners for 10 years. From age 25,
toluene Mas Involved 4-5 times per week
(200-300 ml/week used), and from age 26,
he Inhaled 1-7 times per day (100 ml/day
used.
3-year history of daily aerosol spray
paint inhalation. Product contained
copper, toluene, and xylene as solvents
and i so butane propane and methylene
chloride as propellants.
Sniffed toluene for 4 months, starting
While on the Job using toluene as a
solvent In the rubber processing
industry.
Inhaled pure toluene since age 12,
regularly since age 16 (2 liters used
per month). Sniffed more heavily than
usual during the last 2 months.
Fatigue and clumsiness of the left side which
got progressively worse. Occasional staggering
and mildly slurred speech, disturbed concen-
tration and memory. Normal neurological exam,
EEC, and brain scans. Dally improvement without
specific treatment following cessation of exposure.
Bizzare behavior prior to hospital admission.
Admitted in an agitated, violent, nearly catatonic
state.
Arm and neck tremors, ataxia, incoordlnation,
and equilibrium disorders. No abnormal
psychiatric symptoms. Pneumoencephalographic
and anglographical evidence of midbrain and
cerebrum atrophy. Degeneration of the
cerebellum suspected.
Reduced vision, poor color perception, con-
stricted visual fields, normal optic fundi, im-
paired papillary response, ataxia, and nystagmus.
Symptoms slowly subsided following cessation
of paint sniffing.
Delusions and unpredictable behavior.
Largactll prescribed because he was thought to
have a schizophrenic illness. Symptoms dis-
appeared and did not recur following termina-
tion of sniffing.
Personality changes (apathy, Irritability,
emotional lability, carelessness), vomiting,
difficulty in walking, and slurred speech
1-2 weeks before admission. Gait ataxia,
incoordination, dysarthria, downbeat nystagmus,
bilateral positive Bablnski sign, visual and
color sense loss, impaired concentration and
abstracting ability upon admission. Symptoms
consistent with mainly cerebellar-brain stem
Involvement and possibly optic neuritis.
Symptoms decreased when she did not inhale
toluene, and disappeared after 8 months.
Boor and Hurtig, 1977
Weisenberger, 1977
Sasa et al., 1978
Keane, 1978
Tarsh, 1979
Malm and Lylng-Tunell, 1980
-------
Table 11-7. Results of Neurological and Muscular Function Tests
of Toluene-Exposed Female Shoemakers (Matsushita
et al.f 1975)
Test3
Exposed Group
Control Group
Abnormal tendon reflex:
Biceps and triceps
Patellar
Ankle
Pathological reflex
Grasping power (dominant hand)
Tapping tempo (M + S.D.)C
Cold pressure test
Postural hypotension
Cuff test (upper arm)
D erm a to gr aphi sm
Blocking test (M + S.D.) (seconds)
Numbers investigated
6(l6)b
1*»(37)»
7(18)"
K 3)
11(29)»«
162.9 ± 16.6
6(16)
2( 5)
5(13)
5(13)
68.2 + 13.3
38(100)
3(19)
U 6)
0( 0)
0( 0)
K 6)
168.6 + 17-3
2(13)
K 6)
K 6)
K 6)
61.8 + 13.7
16(100)
Statistical significance (Chi Square- and t-tests): »P < 0.05; **P < 0.01;
M = mean; SD = standard deviation.
aNumbers of subjects with abnormal scores reported.
The percentage of subjects affected is indicated in the parentheses.
Unit of measurement not stated.
11-21
-------
200 ppm); in a "few" working places, gasoline ranged from 20-50 ppm. An
increased urinary hippuric acid level among the exposed women (3-26 4- 0.82 mg/ml
versus 0.35 + 0.24 mg/ml for controls) supported the role of toluene as the
causative agent in producing the toxic effects.
Electroneuromyographic measurements were made in the Seppalainen et al.
(1978) study (described in Section 11.1.1) on 59 of the toluene-exposed car-
painters and 53 referents with a similar age distribution for an indication of a
possible peripheral neurotoxic effect of exposure'. Maximum motor conduction
velocity (MCV), conduction velocity of the slower motor fibers (CVSF), maximal
sensory conduction velocity (SCV), and motor distal latencies were recorded from
nerves in the upper and lower extremities (median, ulnar, deep peroneal, pos-
terior tibial, and sural nerves). Results of these measurements showed that the
mean conduction velocities and motor distal latencies of the car painters were
almost identical to those recorded for the unexposed control group. In several
instances, however, individual nerve conduction velocities were found to be
slower than the normal historical value (not stated) for Seppalainen1 s labora-
tory. When the conduction velocities of the study group were compared with the
historical values, abnormally slow MCVs or SCVs and/or prolonged motor distal
latencies were found in 12 of the 59 painters, but in none of the 53 controls.
Although the two previous reports (Matsushita et al., 1975; Seppalainen
£t jd., 1978) indicate a possible effect of toluene on the peripheral nervous
system, toluene's role in the causation of human peripheral neuropathies has not
been clarified. Reports of polyneuropathies in abusers exposed to excessive and
prolonged concentrations of glues and solvents have appeared in the Japanese and
American literature, but have in all cases involved mixtures of toluene and other
solvents (Matsumura et al.. 1972; Takenaka _et al., 1972; Goto et al., 1974;
Shirabe et al., 1974; Suzuki .et al., 1974; Korobkin et al., 1975; Oh and Kim,
11-22
-------
1976; Towfighi jet al., 1976; Altenklrch et al., 1977). The cases described in
these reports were characterized by the sudden onset and rapid progression of a
symmetric, predominantly motor polyneuropathy (although sensory nerve involve-
ment of the glove and stocking type has been reported), even after exposure has
ceased. Symptoms included extremity weakness, numbness, paresthesia, marked
amyotrophy, and occasional flaccid paresis. The collective results of electro-
myographic studies have shown signs of denervatLon with delayed nerve conduction
velocity, and biopsies of nerves have shown axonal 'degeneration, demyelination,
and enlargement of some axons with focal accumulation of neurofilaments. Muscle
biopsies revealed extensive neurogenic atrophy. -
The earlier reports regarded either ji-hexane alone (Korobkin et al., 1975;
Towfighi jst al., 1976) or a combination of jn-hexane and toluene (Matsumura
e_tal., 1972; Goto jst al., 1974; Shirabe et al., 1974; Suzuki et al., 1974) as
the cause of glue sniffers' neuropathy. The following observations have been
offered as evidence to indicate that ji-hexane plays an important role in its
etiology: (1) in many of the reported cases, neuropathy did not develop until
the patients began to sniff glue products that contained j}-hexane, and (2) it is
known that continuous occupational exposure to jn-hexane under poor ventilation
conditions produces a neuropathy among workers that is clinically and patho-
logically similar to that observed among the glue sniffers. From a recent
outbreak of polyneuropathy among 18 glue thinner sniffers in West Germany,
however, Altenkirch j§t al. (1977) presented data that implicate methyl ethyl-
ketone (MEK) as the causative agent and argues against _n-hexane and toluene as
the causes. These data are summarized as follows (Altenkirch j_t _al., 1977):
1. In a number of sniffing adolescents (1000-2000), no
adverse neurological effects were observed during the
abuse of a thinner with a high ji-hexane (31$) and
toluene (30$) content over a period of 7 years.
11-23
-------
2. The clinical picture of neuropathy occurred when the
ji-hexane fraction had been decreased by approximately
one-half (16$) and MEK (11$) had been added; the amount
of toluene was not significantly changed (29$).
3. Individuals who had discontinued sniffing prior to the
introduction of the new formulation or who had used
only the old composition were not affected. Neuro-
pathies occurred, however, after 3-4 months in sniffers
who had used only the new mixture.
4. Sniffing even a relatively small amount of the MEK-
containing composition led to neurotoxic damages, while
comparatively large amounts of the old composition were
tolerated for a long time without consequences.
5. After the MEK-containing thinner was taken off the
market, new cases of the disease were not observed.
Altenkirch and coworkers (1977) further noted that the exact composition of the
glues that contained ji-hexane and toluene cited in many of the aforementioned
reports is incompletely characterized, and concluded that it remains open to
question whether ji-hexane was the sole causative agent in those cases. It should
be emphasized that no report was located in the literature in which peripheral
neuropathy is attributed to the inhalation of toluene alone. Further, it is
noteworthy that no sensory or neuromuscular involvement was detected in a patient
who experienced permanent cerebral dysfunction following prolonged inhalation of
99$ pure toluene (Boor and Hurtig, 1977).
11.2 EFFECTS ON THE BLOOD AND HEMATOPOIETIC TISSUE
11.2.1. Bone Marrow
The action of toluene on human bone marrow has been the subject of per-
sistent controversy. Early reports of occupational exposures (generally prior
to the 1950s) ascribed myelotoxic effects to toluene (Ferguson £t al., 1933;
Greenburg ej al., 1942; Wilson, 1943), but the majority of recent evidence
indicates that the chemical is not toxic to the blood or bone marrow. The
myelotoxic effects previously attributed to toluene are generally regarded by
recent investigators to be the result of concurrent exposure to benzene, which
11-24
-------
was present as a contaminant. Banfer (1961) noted that it first became possible
to supply industry with adequate quantities of "pure" toluene (<_0.3/6 benzene) in
1955; earlier, workers were typically exposed to toluene that was derived from
coal tar and contaminated with as much as 2Q% benzene.
Greenburg et jl. (1942) found mild depression of erythrocyte levels, abso-
lute lymphocytosis, macrocytosis, and elevation of the hemoglobin level and the
mean corpuscular hemoglobin concentration in 61 airplane painters who had been
exposed to 100-1100 ppm toluene for periods extending from 2 weeks to 5 years
(Table 11-8). Exposure was also associated with liver enlargement in 13 of the
61 painters (Section 11.3), but not with abnormal" leukocyte counts, differential
leukocyte counts, reticulated erythrocyte counts, basophilic aggregation esti-
mates, platelet counts, erythrocyte sedimentation rates, coagulation time, hema-
tocrit values, erythrocyte fragility, or serum bilirubin levels. Approximately
75% of the painters were exposed to concentrations of 500 ppm or less, and the
group had no known prior exposure to benzene. Because these blood changes are
consistent with those of benzene poisoning, however, the contamination of the
toluene vehicle in the paint with benzene cannot be precluded (NIOSH, 1973).
Volatile components such as ethyl alcohol, ethyl acetate, butyl alcohol, and
petroleum naphtha were present in quantity in the lacquers, dopes, and brushes
used by the workers (Table 11-9).
In 19^3, Wilson found that of approximately 1000 industrial workers
(industry not stated) exposed to 50-1500 ppm of commercial toluene vapor for 1 to
3 weeks, 100 showed symptoms attributable to toluene intoxication. Ten of the
100 workers had been exposed to concentrations in excess of 500 ppm and showed
signs of serious CNS depression (Section 11.1.1.1). In most of these 10 cases,
all blood elements remained normal except for the red cell count, which was
"usually" reduced. In 2 of the 10 cases, other blood elements were reduced as
11-25
-------
Table 11-8. Results of Blood Examinations Performed on Toluene-Exposed
Airplane Painters (Greenburg et al., 1942)
Toluene-Exposed
Workers
Unexposed
Workers
Erythrocyte,Count
<5.2 x 10b/mm
Absolute Lvmphocyte Count
>5000/mm
Mean Corpuscular Volume
>100 y3
Hemoglobin
>j6g/100cc
Mean Corpuscular Hemoglobin
35 micromicrograms
Mean Corpsucular Hemoglobin
Concentration
$ of cases >34$
13.1? (N = 61)
5.2$ (N = 346)
20.4$ (N = 59) 7.7$ (N = 395)
21.3$ (N = 61)
13.1$ (N = 61)
34.4$ (N = 61)
7.2$ (N = 111)
29.5$ (N = 61) 2.4$ (N = 81)
0$ (N = 73)
2.5$ (N = 81)
11-26
-------
Table 11-9. Analysis of Paint Used by Painters3
(Greenburg et al., 1942)
Percentage
in Mixture
100.0
Spray painters
Primer (75$ of paint used):
Zinc chromate 10.8
Magnesium silicate 0.7
Synthetic resin 12.8
Driers (lead and cobalt compounds) ' 0.3
Xylene 5.8
Toluene 69.6
Lacquer 1 (15$ of paint used):
Volatile portion:
Ethyl alcohol
Ethyl acetate
Butyl alcohol
Butyl acetate
Petroleum naphtha
Toluene
Nonvolatile:
Nitrocellulose, synthetic resin,
titanium oxide, ferrocyanide blue,
iron oxide, carbon black, zinc oxide,
etc. No lead compounds
Lacquer 2 (10$ of paint used):
Volatile portion:
Toluene
Xylene
Petroleum naphtha
Novolatile:
Resin, titanium oxide, zinc oxide,
ultramarine blue, ferrocyanide
blue, iron oxide, diatomaceous
earth, amorphous silica, carbon
black
100.0
11-27
-------
Table 11-9. Analysis of Paint Used by Painters3
(Greenburg e_t al., 19^*2)
Percentage
in Mixture
Brush painters
Dope:
Volatile portion:
Ethyl acetate
Ethyl alcohol
Butyl acetate
Butyl alcohol
Petroleum naphtha
Toluene
100.0
Nonvolatile:
Nitrocellulose, glycol sebacate,
aluminum, cadmium sulfide, barium
sulfate
Brush wash:
Acetone
Ethyl alcohol
Toluene
1 100.0
Dip painters used a primer only of the same composition
as given for spray painters.
11-28
-------
well (leukocytes, platelets, polymorphonuclear cells, reticulocytes), and
sternal bone marrow biopsies showed partial degeneration of the blood-forming
elements, which resulted in a diagnosis of aplastic anemia. No clinical blood
changes were seen in the workers who had been exposed to the lower concentrations
of toluene (i.e., 0500 ppm).
Von Oettingen e_b al. (19U2a, 19^2b) were the first workers to document the
effects of essentially pure toluene on human subjects. The toluene used was
shown, on spectrophotometric analysis, to contain not more than 0.01$ benzene.
In this study, no significant changes in the total or differential white cell
count were found in 3 volunteers following controlled 8-hour exposures to various
concentrations of toluene within the range of 50-800 ppm. Not more than two
exposure sessions were performed per week to provide sufficient time for recovery
in between exposures, and the experiments were conducted over a period of 8 weeks
(Section 11.1.1.1). Erythrocyte counts were not made.
Parmeggiani and Sassi (195*0 concluded from a clinical study of 11 paint and
pharmaceutical workers exposed to 200-800 ppm toluene and 13 others with expo-
sure to a combination of toluene (150-1900 ppm) and butyl acetate (150-2HOO ppm)
that toluene had no particular injurious action on the bone marrow (or other
organs). The English summary of this study indicated that the workers were
exposed for "many" years, but the purity of the toluene was not reported. Among
the workers in the two groups, 3**$ reportedly showed slight anemia (04,000,000
erythrocytes/mnr), 26J had a mild neutropenia (03500/mm^) with lymphocytosis
(&2000/mm ), and U5/t of the cases showed a decrease in blood platelets
(0150,000/mm ) not accompanied by evident signs of capillary fragility.
In a more recent investigation, Banfer (1961) examined 889 rotogravure
printers and helpers who were exposed to the vapors of toluene-containing
printing inks for at least 3 years. Four hundred seventy eight non-exposed
11-29
-------
persons from two groups served as controls; one group was composed of 155 manage-
ment workers from the same plant, and the second group was composed of 323
persons from outside the plant. The available commercial toluene used in these
inks reportedly contained only traces of benzene (<0.3$); when 5 samples of the
toluene were examined by Banfer, no traces of benzene were found, but the method
of analysis and detection limits were not stated. Analysis of the room air for
toluene was performed by infrared spectroscopy but limited to 5 samples taken
from different sites on a single day. Ambient toluene concentrations were not
specified but three of the samples were determined to be below the "MAK-Wert,"
the fourth sample was at the "MAK-Wert," and the-fifth sample, taken near one of
the presses, exceeded the "MAK-Wert" by 400 ppm. A translation of this study by
NIOSH (1973) indicates that the "MAK-Wert" was 200 ppm. Hematologic examina-
tions of the workers and controls did not reveal any significant changes in the
total number of leukocytes, lymphocytes, granulocytes, or erythrocytes, or hemo-
globin levels (Table 11-10). Sternal biopsies from 6 printers with white cell
counts of less than 5000/cmm were normal.
Capellini and Alessio (1971) performed hematological examination on 17
workers who had been exposed for "diverse" years to 125 ppm toluene (range, 80-
160 ppm) in a plant manufacturing V-belts for industrial machinery. Results
showed that the hemoglobin values, red cell counts, white cell counts, and
platelet counts of the workers were within the same limits as those of 19
nonexposed control subjects from the same plant. The benzene content of the
toluene was not reported. Blood findings were also within normal limits in
another worker employed in a different department who was exposed to mean toluene
concentrations of 250 ppm (range, 210-300 ppm) and who demonstrated symptoms of
CNS toxicity and conjunctiva! irritation.
11-30
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Table 11-10. Hematologic Examination of 889 Rotogravure Workers (Banfer, 1961)
Printers
(N = 889)
Controls,
Group 1a
(N = 155)
Controls,
Group 2
(N = 323)
Leukocytes, total
counts > 8500/cnnn
counts <5000/cmm
counts < 4500/cmm
counts <4000/cmm
Lymphocytes
<35% total leukocytes
total counts < 5000 /cmm
78 (8.77$)
71 (8.32%)
28 (3.15?)
3 (0.33$)
25 (2.81$)
889 (100$)
. 11 (7.09$)
18 (11.61$)
4 (2.58)
1 (0.64$)
3 (4.16$)
155 (100$)
26 (8.04$)
38 (11.76$)
12 (3.71$)
1 (0.30$)
4 (1.32$)
323 (100$)
Granulocytes
total counts >2000/cmm
Erythrocytes
counts < 4 million/cmm
Hemoglobin
value <13g/100ml
889 (100$) 155 (100$) 323 (100$)
16 (1.79$)
4 (0.45$)
3 (1.93$)
4 (2.58$)
7 (2.10$)
4 (1.23$)
Unexposed management workers from the same plant
Unexposed individuals not employed at the plant
11-31
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In 1975, a report by the West German Association of Gravure Printers (Suhr,
1975) identified a study population of 100 printers with at least 10 years of
exposure to pure toluene (<0.3$ benzene) and an unexposed control group of equal
size from the same plant. Analysis of air samples collected from the workplace
indicated that the potential exposure to toluene ranged from 200-400 ppm. Blood
analyses (hemoglobin, erythrocyte, leukocyte, thrombocytes, differential analy-
sis) demonstrated no unusual frequency of abnormalities in either the exposed or
control groups.
Matsushita et al. (1975) found no alterations in the specific gravity of
whole blood, hemoglobin content, hematocrit, or white blood cell counts in a
group of 38 female shoemakers who had been exposed to toluene (60-100 ppm
average) and, in a "few" places, gasoline (range, 20-50 ppm) for an average
duration of 3 years and 4 months. The hematological test results from the
shoemakers were compared with those from an unexposed control group of 16 female
workers. A significantly increased number of Mommsen's toxic granules were
observed, however, in the neutrophils of the exposed workers. Thirteen of the 38
workers showed an abnormal appearance of the granules (mean number per neutro-
phil, 7.6 + 5.6) compared with 1 of 16 controls (mean number per neutrophil, 3-8
± 3.4).
Further evidence of the relative non-toxicity of toluene to the hematopoie-
tic system was presented by Francone and Braier (1954). Toluene, because of its
supposed myelotoxic action, was administered orally as a treatment for leukemia.
It was found that daily doses of up to 10 g of toluene in olive oil for 3 weeks
(to a total of 130 g) were tolerated by leukemia patients without complaints or
evidence of side effects, but the treatment had no clinical effect on the
leukemia process.
11-32
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Hematological abnormalities have been infrequently reported in sniffers of
toluene-based glues. In a total of 90 cases surveyed by four groups of investi-
gators (Christiansson and Karlsson, 1957; Massengale et al., 1963; Barman et al.,
1964; Press and Done, 196?b), there were no instances of anemia or lymphopenia, a
single report of neutropenia, and 6 cases of eosinophilia of greater than 5%.
Christiansson and Karlsson (1957) also performed bone marrow examinations on 17
individuals; 10 of these showed changes suggestive of disturbances in maturation
of leukocytes, although these changes were not reflected in the peripheral blood
of the same individuals. The individuals examined in this study were habituated
to the inhalation of toluene-based paint thinners, rather than model glues as
were the subjects in other surveys. In a fifth clinical survey of 89 glue
sniffers, however, Sokol and Robinson (1963) found abnormalities of the blood in
68 of the cases. An effect on the white blood cells was indicated by findings of
eosinophilia (25 subjects), leukocytosis (12 cases), and lymphopenia (4 sub-
jects). Sokol and Robinson (1963) also reported low hemoglobin values in 20
subjects, basophilic stippling of erythrocytes in U2 of the patients, and noted
the frequent occurrence of poikilocytosis (25 cases), anisocytosis (20 cases),
hypochromia (14 cases), and polychromasia (10 cases). There is no obvious
explanation for the discrepancy between the hematologic findings of Sokol and
Robinson (1963) and those of the other investigators. Because none of the
aforementioned cases deal with exposure to pure toluene, however, the abnormali-
ties observed should be considered to be the possible result of contamination of
the toluene by benzene or some other organic solvent.
Powers (1965) diagnosed 5 cases of acute aplastic anemia that were asso-
ciated with glue sniffing in black adolescents with pre-existing sickle-cell
disease. The 5 children had apparently used three different glues, two contain-
ing toluene and one containing acetone. All of these patients recovered
11-33
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following transfusion and cessation of sniffing. A case of fatal aplastic
anemia, uncomplicated by the presence of sickle-cell disease, was described in a
sixth individual with a 3-year history of glue sniffing.
11.2.2 Blood Coagulation
Pacseri and Emszt (1970; cited in NIOSH, 1973) reported that an increase in
the prothrombin time was found in 191 printers exposed to 170-340 ppm toluene
(duration of exposure not stated). Two of the subjects showed a reduced number
of red blood cells, but no other hematologic abnormalities were found in these
workers. The benzene content of the toluene was not reported.
11.2.3 Phagocytic Activity of Leukocytes
It has been reported that the phagocytic activity of leukocytes from
printing-plant workers exposed to toluene vapors was significantly reduced rela-
tive to a control population (Bansagi, 1968). There was no relationship,
however, between the decrease in activity and the concentration of toluene in the
air. The English summary of this study did not detail any of the exposure
information or mention the benzene content of the toluene.
Friborska (1973; cited in NRC, 1980) noted increased concentrations of
alkaline phosphatase and lactic acid dehydrogenase in leukocytes and increased
acid phosphatase in both leukocytes and lymphocytes from workers who were rou-
tinely exposed to toluene. The authors associated these alterations with
increased functional capacity of the cells.
11.2.4 Immunocompetence
Serum immunoglobulin level (Lange et al., 1973a) and leukocyte agglutinins
(Lange et al.. 1973b) were studied in a group of 35 workers with a history of
exposure to benzene, toluene, and xylene. The duration of exposure ranged from
1-21 years and the concentration of these compounds in the air ranged from 0.011-
0.17 mg/1, 0.08-0.23 mg/1, and 0.12-3.0 mg/1, respectively. Serum IgG and IgA
11-34
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levels were found to be significantly lower in the solvent-exposed workers than
in nonexposed controls, although IgM levels tended to increase (Lange et al.,
1973a). Lange and coworkers (1973b) also found that 10 of the 35 workers had
leukocyte agglutinins for autologous leukocytes, and demonstrated an increase of
leukoagglutination titer in human sera after incubation with benzene, toluene or
xylene; this suggested that some workers exposed simultaneously to these
aromatic compounds may exhibit allergic blood dyserasias. In another group of
workers (N = 79) with a similar history of exposure to benzene, toluene, and
xylene (i.e., levels and durations of exposure comparable to those of the workers
examined by Lange et al.), Smolik et al. (1973) found a decreased level of serum
complement. It should be noted that in all of the aforementioned studies, the
specific solvent(s) responsible for the changes was not identified.
11.3 EFFECTS ON THE LIVER
Greenberg eit al. (19^2) found enlarged livers in 13 out of 61 airplane
painters (21$) who were exposed to 100 to 1100 ppm toluene for from 2 weeks to
more than 5 years. Toluene was the major solvent used in the paints, although
significant quantities of other volatile components were present (Table 10-9);
these workers reportedly had no history of inhalation exposure to any other toxic
volatile solvents, including benzene. This incidence of liver enlargement was 3
times that observed in a control group of 430 workers who had never been exposed
to toluene, but it cannot be correlated with exposure level because only the
numbers of workers exposed at different exposure levels (and not hepatomegaly
incidences) were reported. The liver enlargement was diagnosed by palpitation,
and in no cases were the livers tender. There was also no correlation between
the enlarged livers and either clinical or laboratory evidence of disease, and it
was suggested that the enlargement might have been compensatory in nature.
11-35
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Greenburg and coworkers' (1942) finding of hepatomegaly has not been sub-
stantiated in subsequent studies of workers with histories of occupational
toluene exposure. Parmeggiani and Sassi (1954) found a comparable incidence
(27%} of enlarged livers in a group of 11 paint and pharmaceutical production
workers exposed to 200-800 ppm toluene for "many" years and in a control group of
unexposed workers from the same plant. Normal liver function, as determined by
electrophoresis, serum colloid stability testing, and galactose tolerance
testing, was also observed in the exposed workers. Capellini and Alessio (197D
observed no changes in "the function of the liver" in 17 workers exposed for
"diverse" years to mean atmospheric concentration of 125 ppm toluene (range, 80-
160 ppm) in a plant manufacturing V-belts for industrial machinery. Liver
function was evaluated by determinations of total serum protein and protein
electrophoresis.
More recently, Suhr (1975) also found comparable, but high, incidences of
enlarged livers and elevated liver enzymes in a group of 100 gravure printers
with at least 10 years' exposure to 200-400 ppm pure toluene (benzene <_0.3$), and
in a control group of 100 workers from the same company who had not been exposed
to toluene. It should be noted that the nature and history of the control group
was not defined in any greater detail. Enlargement of the liver was established
in 22$ of the printers and 20$ of the control group, and liver enzyme assays
showed that about half of all test persons (50$ of the printers, 51$ of the
controls) had increases in serum glutamic oxalacetic transaminase (SCOT), serum
glutamic pyruvic transaminase (SGPT), glutamic dehydrogenase (CLDH), or gamma
glutamyl transferase levels. It was concluded that because of the equal
distribution of affected persons in both groups, the deviations in these
parameters could not be attributed to toluene exposure. The cause of the
hepatomegaly and liver enzyme deviations was not further investigated. Blood
alcohol determinations before
11-36
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and after the workshifts indicated comparably elevated levels in both the
printers and control group (less than half of the 100 subjects in each group were
tested; approximately half of the tested subjects had levels between 0.01 and
0.1$); but the significance of this finding is unclear because of the small
number of subjects tested, because only single blood alcohol determinations were
performed on each subject, and because the data was presented ambiguously.
Other studies have reported significant effects on indices of liver func-
tion in groups of toluene-exposed workers. In an examination of 94 rotogravure
printers with a history of exposure to 18-500 ppm toluene and of a reference
group of 30 municipal clerks, Szadlowski ]5t al. "(1976) found significant reduc-
tion in bilirubin and alkaline phosphatase in the exposed group, but no dif-
ference from controls in SCOT, SGPT, leucinamino-peptidase, or cholinesterase
levels. The 94 rotogravure workers were divided into four groups depending upon
the intensity of exposure to toluene. The mean exposure levels, durations of
exposure and ages of the groups were, respectively (Szadkowski et al., 1973):
Group 1 (N = 68) - 300 ppm, 7.3 ± 5.3 years, 32 years; Group 2 (N = 4) - 426 ppm,
newly appointed on day of investigation, 24.3 years; Group 3 (N = 11) - 82 ppm,
5.6 +_ 5.2 years, 42.9 years; Group 4 (N = 11) - 18 ppm, 8.5 + 4.4 years,
35.8 years. Blood alcohol levels ranged from 0.02$ to 0.07$ in the exposed
workers.
Trevisan and Chiesura (1978) performed the following hepatic function tests
on 47 subjects who were exposed occupationally to toluene via inhalation:
bilirubin, SCOT, gamma glutamyl transpeptidase (GGT), alkaline phosphatase (AP),
ornithine-carbamyl transferase (OCT), Quick's test, and protein measurement.
All tests gave normal results with the exception of GGT, which was reportedly
above normal in 34$ of the cases. In a group of 12 subjects controlled before and
after toluene entered in the working operation, mean GGT activity increased
11-37
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2-fold after exposure, with no effects on any of the other tests. Although GOT
has proved to be a very sensitive screening enzyme for slight changes in liver
function (Dragosics et al., 1976), it should be noted that these data were
presented in abstract form and no information on exposure or type of occupation
was presented.
English summaries of two Polish studies of women with histories of occupa-
tional exposure to toluene indicated abnormalities in the glucoprotein, serum
mucoid and haptoglobin patterns of 53 women (Kowal-Gierczak et al., 1969), and
changes in the serum levels of iron and copper and urinary excretion of porphyrin
in 51 women (Cieslinska e_t al., 1969). Clinical signs of liver function impair-
ment were not observed in these subjects, but the changes were interpreted by the
investigators to indicate a hepatotoxic effect of toluene. The concentrations of
toluene, durations of exposure, and the possibility of exposure to other chemi-
cals were not discussed in summaries that were reviewed.
Intensive exposure to toluene via glue or thinner sniffing appears to have a
minimal effect on the liver. Results of hepatic function tests (SCOT, SGPT, AP,
bilirubin, sulfobromophthalein excretion, serum proteins, cephalin flocculation)
on a total of 179 sniffers who were examined in early clinical surveys were
essentially unremarkable (Christiansson and Karlsson, 1957; Massengale e_t al.,
1963; Sokol and Robinson, 1963; Barman e± al., 196U; Press and Done, 1967a,
1967b). Christiansson and Karlsson (1957) did detect liver enlargement in 5 out
of 32 Swedish lacquer thinner sniffers, but other signs of liver function were
normal. More recently, Litt and coworkers (1972) found elevated SGPT and AP
levels in 2% and 5%, respectively, of a group of 982 glue sniffers.
Grabski (1961) described an individual who had abused pure toluene for
6 years and showed signs of cerebellar degeneration, hepatomegaly, and impaired
liver function. Complete series of liver function tests were normal, however, in
11-38
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an optometrist and a glue sniffer exposed independently to 99$ pure toluene, both
of whom also exhibited encephalopathic effects (Boor and Hurtig, 1977). Rever-
sible hepatorenal damage was diagnosed in an individual with a 3-year history of
inhaling a cleaning fluid that contained 80$ toluene (other components not known)
coupled with alcohol ingestion (O'Brien, 1971); the hepatic effect was indicated
by elevated serum bilirubin and AP.
11.4 EFFECTS ON THE KIDNEYS
Exposure to mean concentrations of 60-100 ppm toluene and 20-50 ppm gaso-
line in a "few" working places for an average duration of 3 years and 4 months did
not result in any abnormal urinalysis findings, except for excretion of hippuric
acid, in 38 female shoemakers (Matsushita e_t al., 1975). Proteinuria and
hematuria were noted, however, in a worker who was exposed to concentrations of
toluene sufficient to cause unconsciousness while cleaning the inside of a tank
that was coated with an emulsion of 45$ toluene and 27$ DDT (Lurie, 1949).
Reisin and coworkers (1975) published a report concerning the development
of severe myoglobinuria and non-oliguric acute renal failure in a paint factory
laborer who was exposed to pure toluene by skin contact and aspiration when a
hose burst. The patient had inhaled sufficient amounts of toluene to cause a
loss of consciousness for 18 hours and subsequent development of chemical pneumo-
nitis and sustained superficial burns on approximately 10$ of his body surface
area. Acute renal failure apparently developed from the lack of fluid intake
accompanied by heavy myoglobinuria rather than from a direct effect of toluene.
The early administration of intravenous fluids and diuretics, and the use of
hemodialysis led to complete recovery.
Pyuria, hematuria, and proteinuria have been the most frequently observed
signs of renal dysfunction associated with the deliberate inhalation of toluene-
based glues (Christiansson and Karlsson, 1957; Massengale e_t al., 1963; Sokol and
11-39
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Robinson, 1963; Barman et al., 1964; Press and Done, 1967a, 196?b). The clinical
findings observed in 159 cases surveyed between 1957 and 1967 are tabulated in
Table 11-11. These indications of renal dysfunction have not been universally
observed in glue sniffers, are generally transient, and follow closely the inten-
sive exposures (Press and Done, 1967b).
O'Brien et al. (1971) more recently described a case of reversible hepato-
renal damage in a 19-year old male who had a 3-year history of glue sniffing
while employed in the sign-painting trade. Prior to hospital admission, the
subject had spent 6 hours inhaling a cleaning fluid that contained BQ% toluene
(the other components were not identified). Upon admission, the patient was
vomiting and anuric, and after 8 hours, periorbital edema and subconjunctival
hemorrhages developed. Blood concentration of toluene was determined to be
160 ppm. Other evidence of renal damage included hematuria, proteinuria, ele-
vated serum creatinine, and renal insufficiency required peritoneal dialysis.
The effects of these exposures on hepatic function are discussed in Section 11.3
(Effects on the Liver).
Although serious involvement of the kidney with human intoxication by
toluene has not been stressed in the early literature, several reports have
recently appeared that associate deliberate inhalation of toluene with metabolic
acidosis (Taher et al., 1971*; Fischman and Oster, 1979a; Kroeger et al., 1980;
Bennett and Forman, 1980; Moss et al., 1980). The cases of acidosis described by
these investigators (Table 11-12) are characterized by serious electrolyte
abnormalities (hypokalemia, hyperchloremia), and are related primarily to
toluene's ability to impair hydrogen ion secretion in the distal renal tubule
(distal renal tubular acidosis). In addition to findings compatible with distal
renal tubule acidosis, Moss et al. (1980) found pathologically increased excre-
tions of amino acids, glucose, phosphate, uric acid, and calcium that indicated
11-40
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Table 11-11. Renal Function Investigations of Glue Sniffersc
(Adapted from Press and Done, 1967b)
Number of
Patients
Pyuria
Hematuria
Proteinuria
Clearances
Azotemia
Reference
32
27
89 C
15
16
All 32 urine
samples "normal";
details not given
0
32
0
6
NDb
2
14
0
3
ND
0
12
1
5/13
ND
ND
ND
PSPd
0/13
Urea
1/7
ND
0
ND
0/7-
0/9
Chris tiansson and
Karlsson, 1957
Massengale et al.,
1963
Sokol and Robinson,
Barman et al., 1964
1963
Press and Done, 1967b
Exposure were to toluene-containing plastic cements except in the Christiansson and Karlsson (1957) study,
in which the subjects examined had sniffed paint thinner.
ND = not determined.
Urinary abnormalities were found in 67 of the 89 glue sniffers.
Phenosulfonphthalein clearance in 2 hours.
-------
Table 11-12. Toluene Induced Metabolic Acidosis
Subject/Age
Exposure History
Symptoms
Clinical Findings
Reference
Male (23 yr) Sniffed glue and pure toluene
Intermittently for 6 yr.
Female (20 yr) Two 3- to 5-d episodes of sniffing
aerosol paint containing 60?
toluene within 4 wk.
Several episodes of muscle
weakness following prolonged
(e.g., 1-7 d) Inhalation
sessions. One Instance
of flaccid paralysis.
Nausea.
Hypokalemla with hyperchloremic
metabolic acidosis. Elevated
urinary pH. Toluene detected in
blood.
Hyperchloremic acidosis.
Elevated urinary pH. Toluene
detected in blood.
Taher et al., 1971
Taher et al., 1971
I
*r
ro
Female (17 yr)
Female (21 yr)
Female (25 yr)
Sniffed transmission fluid con-
taining 100$ toluene for 5 d.a
Intermittently sniffed trans-
mission fluid containing 100f
toluene for at least 5 yr.a
Frequent sniffing of transmission
fluid containing 100)1 toluene
during a 5-yr period.3
Persistent vomiting.
Hospitalized on 6 occasions
within a 16 mo. period. Severe
weight loss (18 kg) at first
admission. Recurrent
symptoms of vomiting, muscle
weakness, and lethargy. After
the 6th episode, patient died
of cardlopulmonary arrest.
Persistent vomiting, lethargy,
and muscle weakness.
High anlon gap
acidosis.
metabolic
Hypokalemla. Hyperchloremic
metabolic acidosis and high
urinary pH on 1st and 6th
admissions. High anion gap
metabolic acidosis on the
other admissions.
Normal anlon gap hyperchloremic
metabolic acidosis with severe
hypokalerala.
Fischman and Oster,
1979a
Fischman and Oster,
1979a
Fischman and Oster,
1979a
Male (23 yr)
Female (27 yr)
Four individuals
(details not
stated)
Male (22 yr)
Sniffed toluene on a "regular"
basis for 5 yr. Form not
specified.
Dally inhalation of glue for
9 mo.
Glue or paint sniffers (details
not stated).
Abused a lacquer thinner (99>
toluene) for 8 yr.
Hospitalized 4 times within
15 mo. History of vomiting,
flank pain, and paralysis of the
lower extremities.
Lethargy, weakness, and ataxia.
Microscopic hematuria and
sterile pyuria.
Not stated.
Abdominal pain, vomiting,
generalized weakness, and
diminished reflexes.
Recurrent uretal and renal
calculi (1 stones total).
Hyperchloremic metabolic
acidosis and hypokalerala.
Acidic urine.
Hyperchloremic metabolic
acidosis, hypokalemia,
hypocalcemia, hypophoaphatemia,
and hypouricemla. Increased
excretion of 14 amino acids
and glucose.
Hyperchloremic metabolic
acidosis with hypobicar-
bonatemia.
Hypokalemic and hypochloremic
metabolic acidosis.
Kroeger et al., 1980
Moss et al., 1980
Moss et al., 1980
Bennett and Forman,
1980
Abbreviations: yr = year; d = day; wk = week; mo. = month.
3Toluene is not ordinarily a component of transmission fluid (Fischman and Oster, 1979b).
Anion gap is defined as serum Na - (Cl + HCO,) in tnllliequivalents per liter.
-------
proximal tubule dysfunction consistent with Fanconi's syndrome. Kroeger et al.
(1980) reported the case of a patient with toluene-induced renal tubular acidosis
who developed recurrent urinary calculi. It should be noted that each of the
subjects who developed acidosis had a history of multiple toluene abuse and,
although the acute consquences of renal tubular acidosis associated with toluene
sniffing were on occasion life threatening, these effects were completely rever-
sible with abstinence from toluene exposure. These symptoms also responded
promptly to electrolyte repletion therapy with potassium chloride and sodium
bicarbonate.
Fischman and Oster (1979a) found a high anion gap metabolic acidosis with
hypokalemia in two patients who had sniffed 100/8 toluene; this condition is
reportedly indicative of an increased production of acid by the body. Although
it was noted that renal failure, ketonemia, and elevated lactate levels could
have accounted in part for the abnormal increases in anion gap, it was suggested
that the acid metabolites of toluene (e.g., benzoic and hippuric acids) may have
caused the high anion gap metabolic acidosis.
Clinical manifestations associated with the reported metabolic alterations
included nausea, lethargy, ataxia, muscular weakness, and paralysis
(Table 11-12). NRC (1980) noted that some of these manifestations may mimic
those usually attributed to the effects of toluene on the CNS, and that altered
pH and electrolyte balance may be more commonly responsible for the manifesta-
tions of toluene abuse than is usually recognized. In particular, hypokalemia
often produces significant muscular weakness including flaccid paralysis.
11.5 EFFECTS ON THE HEART
Ogata et al. (1970) found an apparent decrease in the pulse rate of 23
volunteers exposed to 200 ppm toluene for periods of 3 hours or of 7 hours with
one break of 1 hour, but no effect at 100 ppm. Systolic and diastolic blood
11-43
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pressure were not affected by exposure. Exposure to 100 and 200 ppm toluene for
30 minutes did not, however, have any effect on the heart rates or electrocardio-
grams of 15 other subjects during either rest or light exercise (Astrand e_t al.,
1972). Other studies have shown that experimental exposure to toluene at levels
of 100-700 ppm for 20 minutes (Gamberale and Hultengren, 1972) or 50-800 ppm for
8 hours (Von Oettingen et al., 1942a, 19^2b) did not cause any definite effects
on heart rate or blood pressure. Suhr (1975) noted that the pulse rates and
blood pressures of a group of 100 printers with a 10-year history of exposure to
200-UOO ppm toluene and those of an unexposed control group of identical size
were similar at the beginning and end of work shifts.
Sudden deaths that were not due to suffocation secondary to solvent sniffing
but rather were attributed to a direct effect of the solvent itself have been
reported in at least 122 cases (Bass, 1970; Alha et al., 1973)- Toluene,
benzene, and gasoline have been individually implicated in a small number of
these deaths (10, 6, and 4 cases, respectively), but the volatile hydrocarbons
most frequently involved were trichloroethane and fluorinated aerosol pro-
pellants. Severe cardiac arrhythmia resulting from light plane anesthesia seems
to be the most likely explanation for the cause of the sudden sniffing deaths.
Bass et ad. (1970) noted that stress, vigorous activity, and hypoxia in combina-
tion with sniffing appear to increase the risk of death.
11.6 EFFECTS ON MENSTRUATION
Dysmenorrhea was reported by 19 out of 38 Japanese female shoemakers (mean
age, 20.7 years) who were exposed to mean toluene concentrations of 60-100 ppm
for an average duration of 3 years and 4 months (Matsushita et al., 1975). In an
unexposed control group of 16 women from the same plant, this effect was noted in
3 individuals (19$). It should be noted that these women were concomitantly
exposed to 20-50 ppm of gasoline in a "few" working places.
-------
Michon (1965) reported disturbances of menstruation in a group of 500 women
(age 20-40 years) who had been exposed to a mixture of benzene, toluene, and
xylene in the air of a leather and rubber shoe factory. The concentration and
component distribution of this mixture were not specified, but it was stated in
the English summary of this study to be within permissible occupational limits
established at the time in Poland (100 mg/nr (31 ppm) for benzene, 250 mg/m
(67 ppm) for toluene, and 250 mg/m^ (58 ppm) for xylene). When the menstrual
cycles of the exposed women were compared with those of 100 women from the same
plant with no exposure to these hydrocarbons, prolonged and more intense men-
strual bleeding was found in the exposed group. The regularity of the cycle was
not affected.
It has also been noted in the English summary of a Russian study that
occupational exposure to average concentrations of 25-350 mg/m toluene and
other solvents, through the use of organosiliceous varnishes in the manufacture
of electric insulation materials, caused a high percentage of menstrual dis-
orders (Syrovadko, 1977). The newborn of these women were reportedly more often
underweight and experienced more frequent fetal asphyxia and "belated" onset of
nursing.
11.7 EFFECTS ON THE RESPIRATORY TRACT AND THE EYES
11.7.1 Effects of Exposure
Carpenter e_t al. (1944) observed that 2 male subjects who were exposed to
toluene for 7-8 hours experienced transitory mild throat and eye irritation at
200 ppm, and lacrimation at 400 ppm. Parmeggiani and Sassi (1954) found irrita-
tion of the upper respiratory tract and conjunctiva in 1 of 11 paint and pharma-
ceutical product workers who were exposed to 200-800 ppm toluene for "many"
years. In the studies of Von Oettingen e_t al. (1942) and Wilson (1943), however,
no complaints of respiratory tract discomfort were recorded in volunteers or
11-45
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workers exposed to levels of toluene as high as 800-1500 ppm for 8-hour periods
(Section 11.1, Effects on the Nervous System). .In two episodes of accidental
poisoning on ships that involved estimated short-term exposures to 10,000-
30,000 ppm toluene, Longley et al. (1967) recorded no complaints of respiratory
tract or eye irritation among 26 men.
Three workers accidentally splashed with toluene have transient epithelial
injury to the eyes that consisted of moderate conjunctival irritation and corneal
damage with no loss of vision (McLaughlin, 1916; Grant, 1962, both cited in
NIOSH, 1973). Complete recovery generally occurred within 48 hours. The results
of opthalmologic examinations of 26 spray painters who were exposed to toluene at
levels of 100-1000 ppm for 2 weeks to more than 5 years were reported to be
negative (Greenburg et al., 1942); results were not published, the examinations
in each case consisted of a "history of ocular complaints, visual acuity, fundus,
pupil and slit lamp investigation of the media of the eye.
Raitta and coworkers (1976) found lens changes in a group of 92 car painters
who were exposed to a mixture of organic solvents for 1 to 40 years (mean 15 +
9 years). Of the organic solvents detected in the breathing zones of the
workers, toluene was present in the greatest amounts (30.6 ppm). This study was
part of a large investigation performed to evaluate the effects of chronic
solvent exposure on the nervous system of the car painters (Hanninen et al.,
1976; Seppalainen et al., 1978) (Section 11.1.1.2); the mean concentrations of
the other solvents present in the air are included in the summary of the Hanninen
study (Table 11-3). Among the 92 car painters (mean age 34.9 + 10.4 years, range
21-64 years), 2 had been operated on for a cataract and 46 had ocular changes
that consisted mainly of lens opacities and/or nuclear sclerosis. To eliminate
the influence of age on the development of the lens changes, the painters were
compared with age-matched unexposed railroad engineers; 69 age-matched pairs
11-46
-------
were generated for comparison. Results showed that in 27 instances, more lens
changes were present in the car painters than in the age-matched engineers, and
in 4 instances, there were more changes in the engineers (Table 11-13). In the
remaining 38 pairs, both the painters and the unexposed engineers had similar
lens changes. The lens changes were further found to occur with increased
frequencies after 10 years of exposure (Table 11-13).
11.7.2 Sensory Thresholds
Gusev (1965) investigated the olfactory threshold for toluene in 30
subjects with a total of 744 observations. The minimum perceptible concentration
was found to be within 0.40-0.85 ppm (1.5-3.2 mg/nr) and the maximum imper-
ceptible concentration within 0.35-0.74 ppm (1.3-2.8 mg/nr). In sniff tests
with 16 subjects (8 male, 8 females), May (1966) determined the minimum per
ceptible concentration to be a much higher 37 ppm (140 mg/nr); toluene was found
to be clearly perceptible at 70 ppm. In the latter study, the number of observa-
tions used to establish the average values were not stated.
Odor thresholds and sensory responses to inhaled vapors of Toluene Concen-
trate were recently determined by Carpenter e_t al. (1976b). Toluene Concentrate
is a hydrocarbon mixture containing 45.89? toluene, 38.69? paraffins, 15.36?
naphthenes, and 0.06? benzene. The most probable concentration for odor
threshold, determined in two trials with 6 subjects, was 2.5 ppm. Based on
sensory thresholds for irritation (eye, nose, throat), dizziness, taste, and
olfactory fatigue, 6 of 6 volunteers indicated their willingness to work for
8 hours in a concentration of 480 ppm (corresponding to 220 ppm of toluene).
Only 3 subjects thought they could work in an atmosphere containing 930 ppm
(corresponding to about 427 ppm toluene).
11-47
-------
Table 11-13. Frequency of Lens Changes and Distribution by Exposure Time
in 69 Age-Matched Pairs of Car Painters and Railvray
Engineers (Raitta jet al., 1976)
Result
Frequency of
Lens Changes
(no. pairs)
Distribution of Lens Changes
by Years of Exposure
< 10
11-20
Car painters had fewer
changes than the engineers
No noticeable difference
between the pairs
Car painters had more
changes than the engineers
38
27
22
13
17
11-48
-------
11.8 EFFECTS ON THE SKIN
Toluene is poorly absorbed through the skin (Section 13.1), and has an
affinity for fat. When toluene is applied to the skin, its degreasing action
will remove natural lipids, possibly causing dryness, fissures, and contact
dermatitis (Gerarde, 1960; Browning, 1965).
Malten £t al. (1968) found that exposure of human forearm skin for 1 hour on
6 successive days to toluene (volume and conditions not stated) resulted in
injury to the epidermal stratum corneum (horny layer). The skin damage was
assayed by measurements of water vapor loss, and daily measurements following the
exposures indicated that regeneration took about "4 weeks.
Koilonychia and hapalonychia of the fingernails (conditions in which the
nails are, respectively, concave and soft, uncornified) were observed in 6 of 16
cabinet makers who were dermally exposed to a thinner mixture that contained 30$
toluene, 30$ xylene, and 40$ methyl alcohol (Ancona-Alayon, 1975). These defor-
mities involved primarily the thumb, index, and middle fingernails, and were
attributed to the practice of cleaning metal parts on furniture with solvent-
soaked rags and unprotected hands. Most of the affected workers had an average
exposure of 2 years.
11.9 SUMMARY
Exposures of humans to toluene have almost exclusively involved inhalation
in experimental or occupational settings or during episodes of intentional
abuse, and the health effect of greatest concern is dysfunction of the central
nervous system.
Single eight-hour experimental (Von Oettingen e£ al., 1942a, 19^2b;
Carpenter et al., 194U) and subchronic occupational (Wilson, 1942) exposures to
toluene in the range of 200-300 ppm have elicited subjective symptoms indicative
of CNS depression (e.g., fatigue, nausea, muscular weakness, mental confusion,
11-49
-------
and impaired coordination). These types of effects were generally dose-
dependent, and increased in severity with increasing toluene concentration.
Acute experimental exposures to toluene have also caused objective increases in
reaction time at 200-300 ppm (Ogata et al., 1970; Gamberale and Hultengren,
1972), and decreases in perceptual speed at 700 ppm (Gamberale and Hultengren,
1972). Gusev (1965) observed disturbances of EEC activity in several subjects
exposed to 0.27 ppm toluene for 6-minute intervals, but this effect does not have
any apparent toxicological significance.
Short-term accidental workplace (Lurie, 1949; Andersen and Kaada, 1953;
Browning, 1965; Longley et al., 1967; fteisin et al., 1975) and deliberate (Press
and Done, 1967a, 1967b; Wyse, 1973; Lewis and Patterson, 1974; Hayden et al.,
1977; Oliver and Watson, 1977; Barnes, 1979; Helliwell and Murphy, 1979) inhala-
tion exposures to excessive levels of toluene (i.e., levels approaching air
saturation concentrations of 30,000 ppm) have initially resulted in CNS stimula-
tory effects such as exhilaration, lightheadedness, dizziness, and delusions.
As exposure durations increase, narcotic effects characteristic of CNS depres-
sion progressively develop, and, in extreme cases, collapse, loss of consious-
ness, and death (Winek et al., 1968; Chiba, 1969; Nomiyama and Nomiyama, 1978)
have occurred.
Chronic occupational exposure to toluene has been associated with "nervous
hyperexcitability" (Parmeggiani and Sassi, 1954) and subjective memory,
thinking, and activity disturbances (Munchinger, 1963) in workers exposed,
respectively, to concentrations of 200-800 ppm and 300-430 ppm. No evidence of
adverse neurological effects have been reported, however, in other studies of
printers exposed to 200-400 ppm toluene (Suhr, 1975) or manufacturing workers
exposed to 80-160 ppm toluene (Capellini and Alessio, 1971), although the nega-
tive findings in the fomrer study are equivocal and symptoms of stupor,
11-50
-------
nervousness, and insomnia were noted in one worker exposed to 210-300 ppm toluene
in the latter study. Exposure to mixtures of varpors of organic solvent contain-
ing predominately low-levels of toluene (approximately 30 ppm) for an average of
15 years has produced a greater incidence of CNS symptoms and impaired perfor-
mance on tests for intellectual and psychomotor ability and memory in car
painters (Hanninen et _al., 1976; Seppalainen ^t ^1., 1978). Matsushita et al.
(1975) reported impaired performance in neurological and muscular function tests
in female shoemakers who had been exposed to 15-200 toluene for an average
duration of over 3 years, but these workers were exposed to "slight" levels of
gasoline. Changes in EEC response to photic- stimulation were reported by
Rouskova (1975) in workers exposed to >250 ppm toluene and unspecified levels of
1,1,1-trichloroethane for an average of 13.5 years.
Residual effects indicative of cerebellar and cerebral dysfunction have
been observed in a number of persons who had abused toluene or solvent mixtures
containing toluene over a period of years (Grabski, 1961; Satran and Dodson,
1963; Knox and Nelson, 1966; Kelly, 1975; Boor and Hurtig, 1977; Weisenberger,
1977; Keane, 1978; Sasa .et al., 1978; Tarsh, 1979; Malm and Lying-Tunell, 1980).
These effects were largely reversible upon cessation of exposure, but prolonged
toluene abuse has, on occasion, led to permanent encephalopathy and brain atrophy
(Knox and Nelson, 1966; Boor and Hurtig, 1977; Sasa e_t jd., 1978). Reports of
polyneuropathies in abusers of glues and solvents have appeared in the litera-
ture, but have in all cases involved mixtures of toluene and other solvents such
as ji-hexane and methyl ethyl ketone (Matsumura ^t al.. 1972; Takenaka et al.,
1972; Goto^tal., 1974; Shirabe .et al., 1974; Suzuki et al., 1974; Korobkin
et al., 1975; Oh and Kim, 1976; Towfighi et al., 1976; Altenkirch et al., 1977).
Early reports of occupational exposures (generally prior to the 1950s)
ascribed myelotoxic effects to toluene (Greenburg et al. 1942; Wilson, 1943), but
11-51
-------
the majority of recent evidence indicates that toluene is not toxic towards the
blood or bone marrow (Von Oettingen et al., 1942a, 1942b; Parmeggiani and Sassi,
1954; Banfer, 1961; Capellini and Alessio, 1971; Suhr, 1975; Matsushita et al.,
1975). When administered orally to leukemia patients, it has been further
reported that toluene had no effect on the leukemic process (Francone and Braier,
1954). Hematological abnormalities have been infrequently reported in sniffers
of toluene-based glues and thinners (Christiansson and Karlsson, 1957;
Massengale et al., 1963; Sokol and Robinson, 1963; Barman et al., 1964; Press and
Done, 1967b). Other investigators have noted increases in prothrombin time
(Pacseri and Emszt, 1970), decreases in progocytic activity of leukocytes
(Bansagi, 1968), and increased enzyme concentrations in leukocytes and lympho-
cytes (Friborska, 1973) of workers who were exposed to toluene. Decreases in
serum immunoglobin and complement levels (Lange et al., 1973a; Smolik et al.,
1973) and leukocyte agglutinins (Lange et al., 1973b) have been reported in
workers exposed simultaneously to benzene, toluene, and xylene.
Liver enlargement was reported in an early study of painters with exposures
to 100-1100 ppm toluene for 2 weeks to more than 5 years (Greenburg et al.,
19^2), but this effect was not associated with chemical evidence of liver disease
or corroborated in subsequent studies of workers (Parmeggiani and Sassi, 1954;
Suhr, 1975). Chronic occupational exposure to toluene has generally not been
associated with abnormal liver function (Greenberg et aJL., 1942; Parmeggiani and
Sassi, 1954; Capellini and Alessio, 1971; Suhr, 1975), although reductions in
serum bilirubin and alkaline phosphatase (Szadlowski et al., 1976) and gamma
glutamyl transpeptidase (Trevisan and Chiesura, 1978) have been noted. Inten-
sive exposure to toluene via glue or thinner sniffing appears to have a minimal
effect on the liver (Christiansson and Karlsson, 1957; Grabski, 1961; Massengale
11-52
-------
et al., 1963: Sokol and Robinson, 1963; Barman et al., 196M; Boor and Hurtig,
1977; Press and Done, 1967a, 1967b).
Exposure to mean concentrations of 60-100 ppm toluene for over 3 years did
not result in abnormal urinalysis findings in female shoemakers (Matsushita
et al., 1975), but clincial case reports have described proteinuria and hema-
turia (Lurie, 19^9; O'Brien et al., 1971) and myoglobenuria and renal failure
(Reisin ^t al., 1975) in workers who were accidentally overexposed to toluene.
Pyria, hematuria, and proteinuria have been the most frequently observed signs of
renal dysfunction associated with the deliberate inhalation of toluene-based
glues, but these effects have not been universally observed in glue sniffers
(Christiansson and Karlsson, 1957; Massengale et al., 1963; Sokol and Robinson,
1963; Barman e_t al., 1964; Press and Done, 1967a, 1967b). Several reports have
recently appeared that associate deliberate inhalation of toluene with metabolic
acidosis (Taher et al., 197^; Fischman and Oster, 1979a; Koeger et al., 1980;
Bennett and Forman, 1980; Moss et al., 1980).
Acute experimental exposure to toluene within the range of 50-800 ppm have
not caused any definite effects on heart rate or blood pressure (Von Oettingen
et al., 1942a, 19**2b; Ogata et al., 1970; Astrand et al., 1972; Gamberale and
Hultengren, 1972). Toluene has been implicated in a small number of sudden
deaths due to solvent sniffing which appear to result from cardiac arrhythmias
(Bass, 1970; Alha et al., 1973), but trichloroethane and fluorinated aerosol
propellants have most frequently been associated with these deaths.
Dysmenorrhea has been reported in a significant number of female shoemakers
exposed to 60-100 ppm toluene and concomitantly to 2050 ppm gasoline in a "few"
working places for an average duration of 3 years and 4 months (Matsushita
et al., 1975). Disturbances of menstruation have also been reported in women
exposed concurrently to toluene, benzene, and xylene in the workplace (Michon,
11-53
-------
1965), and in women exposed occupationally to toluene and other unspecified
solvents (Syrovadko, 1977).
Minimum perceptible concentrations of toluene have been determined to be
O.MO-0.85 ppm (Gusev, 195) and 37 ppm (May, 1966), but the reasons for this
discrepancy are not apparent. Toluene has been reported to cause transitory eye
and respiratory tract irritation as a result of 8-hour exposures in the range of
200-800 ppm (Carpenter £t al., 1944; Parmeggiani and Sassi, 1954; Capellini and
Alessio, 1971), but no complaints of respiratory tract discomfort were recorded
in volunteers or workers exposed to levels as high as 800-1500 ppm for 8-hour
periods in other studies (Von Oettingen et al., '1942; Wilson, 1943). No com-
plaints of respiratory tract or eye irritation were recorded in men accidentally
exposed to 10,000-30,000 ppm toluene for brief durations (Longley e_t a_l., 1967).
Opthalmologic examinations of spray painters who were exposed to
100-1000 ppm toluene for 2 weeks to more than 5 years were normal (Greenburg
est al., 1942), but Ratta et al. (1976) found lens changes in a group of car
painters exposed concurrently to approximately 30 ppm toluene and much lower
concentrations of other solvents for an average of 15 years. The little
information that is available on the dermal toxicity of toluene indicates that
moderate contact may cause skin damage due to its degreasing action (Gerarde,
1960; Browning, 1965; Molten et al., 1968).
11-54
-------
12.1 SPECIES SENSITIVITY
Information on the toxic effects of chronic exposure to low levels of
toluene may be more relevant to greater numbers of people than information on
acute toxicity from the viewpoint of industrial health. However, for those rare
exposures to high levels, e.g., "glue sniffing", data obtained from acute
toxicity studies are valuable. In the sections to follow consideration will be
given to acute, as well as chronic, studies.
Inhalation has been a principal route of exposure in humans; therefore,
animal studies have centered on intoxication by this route. In all species
studied the progressive symptoms typically found-after increasingly higher doses
were irritation of the mucous membranes, incoordination, mydriasis, narcosis,
tremors, prostration, anesthesia, and death. Cats appeared to be more resistant
than dogs and rabbits. Rats and mice were less resistant than dogs or rabbits
(see Tables 12-1 and 12-2).
12.1.1 Acute Exposure to Toluene
12.1.1.1 Acute Inhalation
Carpenter _et al. (197&b) reported 100$ mortality in rats exposed to
4 hours' inhalation of 12,000 ppm of "toluene concentrate" comprising a mixture
of paraffins, naphthenes, and aromatics (45.9$ toluene and 0.06$ benzene).
Tremors were seen in 5 minutes and prostration in 15 minutes. At 6300 ppm,
inhalation produced head tremors in 1 hour and prostration in 2 hours, while only
slight loss of coordination was seen after 4 hours at 3300 ppm. A calculated
LC50 of 8800 ppm for a 4-hour period of inhalation was reported in this study.
Inhalation of a thinner containing less toluene (=33?) and only 0.01$ benzene,
elicited less toxic symptoms at a similar range of doses in rats in a companion
study by the same laboratory (Carpenter et al., 1976a).
12-1
-------
Table 12-1. Acute Toxicity of Toluene
Route
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
inhalation
Species
rats
rats
rats
rats
rats
rats
rats
rats
rats
nice
mice
Swiss mice
mice
mice
mice
cats
Dose
4,000 ppm for 4 h
24,400 pom for 1.5 h
12,200 ppm for 6.5 n
13,269 ppm
12,000 ppm for 4 h
("toluene concentrate")
6,300 ppm for 4 h
("toluene concentrate")
3,300 ppm for 4 h
("toluene concentrate")
1 ,700 ppm for * h
("toluena concentrate")
3,800 ppm for U h
("toluene concentrate")
24,400 ppm for 1 .5 h
12,200 ppo for 6.5 h
5,320 ppm for 7 h
(less than 0.01?
benzene present)
6,942 ppm for 6 h
(99.5? purity)
6,634 ppm
9,288 ppm
7,800 ppm for 6 h
Effect
1/6 dead
60} mortality
50J mortality
Lethal dose
Lethal dose
Head tremors in 1 h
Prostration in 2 h, nornal
3 h after exposure
Slight loss of coordination
So- effect- level
LC50
10* mortality
100 % mortality
LC50
LC50
LC50
Lethal dose
Progressive signs: slight
Reference
Smyth e_t al. , 19&9a
Cameron at al. , 1938
Cameron e_t al. , 1938
Faustov, 1958
Carpenter at aj,. , I976b
Carpenter ^t al. , 1976b
Carpenter _et al. , 1976b
Carpenter _et al. , 1976b
Carpenter e£ al. , 1976b
Cameron e_t aj.. , 1933
Cameron £t al. , '938
Svirbely at al. , 1943
Bonnet jat al. , 1979
Faustov, 1958
Faustov, 1958
Carpenter _e_t al. , !976b
inhalation guinea pigs
inhalation rabbits
inhalation dogs
("toluene concentrate")
4,000 ppm for 4 h
5,500 ppm
850 ppm for 1 h
loss of coordination,
mydriasis, and slight hyper-
sensitivity to light within
20 ain
Prostration - 80 min
Anesthesia - 2 h
One death during 14 d
observation period
2/3 dead within a few days
Lethal within 40 min
Increased respiration rate,
decreased respiration
volume
Smyth and Smyth, 1928
Carpenter et al., 1944
von Oettingen e_t al.,
1942b
12-2
-------
Table 12-1. Acute Toxicity of Toluene (Cont'd)
Route
inhalation
inhalation
inhalation
inhalation
oral
oral
oral
oral
i.p.
i.p.
i.p.
i.p.
i.p.
i.p.
i.p.
i.p.
Species
mice
mica
dogs
n = 2
dogs
n = 2
rats
Wistar rats
adult
Sprague-Dawley rats
( 150-200 g)
rats
lU-d-old, both sexes
young adults
older adul ta
rats and mice
rats
rats
rats (both sexes)
mice (male)
nice (female)
mice
guinea pigs
Dose
3,600 ppm, 15,000 ppm
("toluene concentrate")
3,000 ppo "toluene
concentrate"
760 ppm "toluene con-
centrate" 6 h/d x 2 d
rested for U d, exposed
again for 3 d
1,500 ppm "toluene con-
centrate" 6 h/d x 3d
7.53 g/kg (6.73-3.43)
7.0 g/kg
5.58 g/kg
(5.3-5.9 g/kg)
3.0 ml/kg (2.6 g/kg)
5.U ml/kg (5.5 3/kg)
7.4 ail/kg (6.4 g/kg)
2.0 co/kg (1.7 g/kg)
0.75 co/kg (0.7 g/kg)
1.75 to 2.0 cc/kg
(1.5 g/kg to 1.7 g/kg)
800 mg/kg at 26°C
530 mg/kg at 8°C
255 mg/kg at 36°C
1.15 g/kg in olive oil
(1.04-1.31 g/kg)
(graded doses between
0.79 and 1.65 g/kg)
Lot g/kg
4 g/kg
2.0 ml pure solvent
Effect
50$ reduction respiratory
rate
No-effect-level on
respiratory rate
Weight loss of 1.1 *g in
I dog, otherwise normal
Slight lacrimation and head
tremors
LD50
LD50
LD50
LD50
LD50
L350
Lethal dose
Apathy
Death from respiratory
failure
Approximate lethal dose
LE50
Observed for 24 h
Cause of death:
respiratory failure
LD50
Lethal dose
'6/10 dead after 2 h
Reference
Carpenter _et al. , 1976b
Carpenter £t al. , 1976b
Carpenter ?t al. , 1976b
Carpenter _8t al. , 1976b
Smyth at al. , !969a
Wolf st al. , 1956
Withey and Hall, 1975
Kiraura et al. , 1S71
Cameron _et al. , '938
3atchelor, 1927
3atchelor, 1927
Xeplinger _at al. , 1959
Xoga and Ohmiya, 1978
Ikeda and Ohtsuji, 1971
Tsuzi, 1956
Wahlberg, 1976
(1.7 g)
All dead after 6 h
12-3
-------
Table 12-1. Acute Toxicity of Toluene (Cont'd)
Route Species
3.0. rats and nice
i.v. rabbits
eternal rabbits
(single
application)
dermal, rabbits
abdomen
5-10
0.15
o.ao
1U. 1
Dose
cc/kg
cc/kg
cc/kg
ml/kg
uncovered
(U.3-8.2 g/kg)
(.13 g/kg)
(.17 g/kg)
application
Effect
Lathal dose
13$ mortality
100$ mortality
LD50
Slight irritation
Reference
Cameron
Sraier,
Smyth e_
Smyth e_
e_t al.
1973
t al . ,
t al.,
, i938
1969a
I969a
deraal
dermal
dermal
rabbits
guinea pigs
guinea pigs
corneal rabbits
sorneal rabbits
corneal rabbits
10 to 20 applications of
undiluted toluene to
rabbit ear and bandaged
to shaved abdomen
1 mi for 16 h
2.0 ol, covered
0.005 ml
0.005 ml
2 drops
Perceptible erythema,
thin layer of devitalized
tissue which exfoliated
No effect on gross appearance,
behavior, or weight
Karyopyknosis, karyolysis,
perinuclear edema,
socngicsis,
junctional separation.
cellular infiltration in
dennis,
no liver and kidney damage
Completely absorbed by 5th
to 7th ci
No mortality up to u wk
Weight less than controls
for wk 1-3, no difference at
wit 4
Moderately severe injury
Moderately severe injury
Perceptible irritation of
conjunctiva! membranes
Mo corneal injury
Wolf .et al. , 1956
Kronevi et al., 1979
Wahlberg, 1976
Smyth e_t al., 1969a
Carpenter and Smyth, 19t6
Wolf et al., 1956
Abbreviations: h = hour; min = minute; d = day; wk = week;
i.v. = intravenous; n = number; ns = not specified.
i.p. = intraperitoneal; 3.c. = subcutaneous;
12-4
-------
Table 12-2. Subchronic Effects of Toluene
Species
Route
Dose
Effect
Reference
Rat
Inhalation
1600 ppm
18-20 h/d
Initial effect of instability
and incoordi nation, con June-
Batchelor,
1927
Rat
Inhalation
Rat
Rat
Rat
Inhalation
Inhalation
Inhalation
(NO
Rat
Inhalation
1600 ppm
18-20 h/d x 3 d
1250 ppm
18-20 h/d
620 ppm, 1100 ppm
18-20 h/d
1000 ppm solvent mix-
ture (50-60* benzene,
30-35* toluene, 4$
xylene)
7 h/d x 5 d x 28 wk
240, 480, 980 ppm
"toluene concentrate"
6 h/d x 5 d/wk x 65 d
tivitis, lacrimation, and
sniffles; then narcosis
Mild twitching; drop in body
temperature; death. Histology:
severe cloudy swelling of
kidneys, no effect on liver,
heart, or testes
Slight instability and
incoordination; mucous
membrane irritation
No-effect-level on symptoms;
hyperplasia of bone marrow
No effect on body weight;
lymphopenia followed by leuco-
cytosis and lymphocytosis; tran-
sient changes in1 blood picture
before or after each daily
exposure; splenic hemosiderosis
greater than that found after
inhalation of benzene only:
slight to moderate reduction
2-1/2 wk after exposure. Nar-
rowing of peri-follicular collars
of cells in sleen, no fat in
livers and kidney; iron-negative
pigment in kidneys of few animals.
No effect on red blood cell count
white blood cell count, hemato-
crit, hemoglobin, total and dif-
ferential white count, blood urea
nitrogen, SCOT, SGPT, alkaline
phosphatase, or body weight.
Batchelor, 1927
Batchelor, 1927
Batchelor, 1927
Svirbely et al.,
Carpenter et al., 1976b
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Reference
Rat
Inhalation
318*4 ppm
4 h/d x 30 d
Increased levels of SCOT,
SGPT, 3- lipo proteins
Khinkova, 197^
Rat
Inhalation
200 ppm ,
7 h/d x
600 ppm
5 d x 6 wk
IV)
CTi
Rat
Inhalation
2500 ppm , 5000 ppm
7 h/d x 5 d x 5 wk
decreased levels of gluta-
thione, catalase, peroxi-
dase, total cholesterol
No narcosis; body weight
normal; no significant
change in WBC count, RBC
count,or hemoglobin during
weekly sampling; increase in
percentage of segmented cells;
histological changes: slight
pulmonary irritation; few
casts in straight collecting
tubules in rats at 600 ppm;
no change in liver, spleen,
heart, and bone marrow
Transient decrease in body
weight; hyperactivity, -marked
incoordination, recovery after
cessation of exposure; mor-
tality in 5000 ppm group 18/25;
increased bleeding time; blood
picture: total leucocytes
reduced after each exposure;
pulmonary lesions occurred
earlier than in group exposed
to 200 or 600 ppm; casts in
renal tubules in all rats
within 2 wk of exposure; rest
of histology same as 200
and 600 ppm
von Oettingen, 1942b
von Oettingen et al., 19l*2b
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Reference
Rat
Inhalation
300 ppm; 6 h/d x
Increase of hepatic enzy
mes Elovaara et al.,
1979
Rat, guinea
pig, dog,
monkey
rats
n=U-6 animals
Inhalation
inhalation
ro
Dogs
n=2
experimental,
1 control
Inhalation
107 ppm continuously
for 90 d; 1085 ppm
8 h/d, 5 d/wk x 6 wk
7 consecutive cycles
daily, 5 d/wk x 8 wk:
each cycle, 10 min to
1200 ppm followed by
20 min solvent-free
internal
2000 ppm 8 h/d x
6 d/wk x U mo, and
then 2660 ppm 8 h/d,
6 d/wk x 2 mo
(cytochrome P-450, ethoxy-
coumarin 0-deethylase increased;
UDP glucuronslytransferase in-
creased only at end of exposure)
No effect on leukocytes, hemo-
globin, or hematocrit; no effect
on liver, kidney, lungs, spleen
or heart; no effect on brain or
spinal cord of dogs and monkeys
Depression of body weight;
increased SCOT, LDH levels;
no effect on BUN levels
Depression of kidney, brain,
and lung weights. Histology:
no effect on brain, lung, liver
heart, or kidney, no sign of
lipid vacuolation' in liver
Death on days 179 and 180; slight
nasal and ocular irritation; motor
incoordination and paralysis of
extremities during terminal phase;
congestion in lungs, hemorrhagic
liver, reduced lymphoid follicles
and hemosiderosis in spleen;
hyperemic renal glomeruli; albumin
in urine
Jenkins et al., 1970
Bruckner and Peterson, 1981a
Fabre _et al., 1955
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Reference
Dogs
Inhalation
Dogs
mice
n=4-6 animals
Inhalation
Inhalation
ro
OO
Mice
Mice
Mice
Inhalation
Inhalation
Inhalation
200, 400, 600 ppm
3 8-h exposures
for 1 wk, then 5 x 7-h
for 1 wk and finally
850 ppm for 1 hr
No effect on circulation, spinal
pressure; increase of respiratory
rate, small increase of minute
volume, decrease of respiratory
volume
von Oettingen et al., 1942b
400 ppm; 7 h/d x 5 d Moderate temporary lymphocytosis
7 consecutive cycles
daily, 5 d/wk x 8 wk:
each cycle, 10 rain, to
12,000 ppm followed
by 20 min. solvent-
free interval
4000 ppm 99.9$ pure
toluene for 3 h
4000 ppm 99.9$ pure
toluene for 3 h/d x
1, 3, or 5 d
4000 ppm 99.9$ pure
for 3 h/d x 5 d/wk
x 8 wk
Depression of body weight gain;
no effect on LDH; decreased BUN
levels; SCOT levels increased
(not significantly) depression
of kidney, brain and lung weights;
Histology: no effect on brain,
lung, liver, heart, or kidneys;
no sign of lipid vaculoation in
liver.
No effect on LDH activity
significant increase of
SCOT 24 h post exposure only
von Oettingen et al., 1942b
Bruckner and Peterson, 1981 a
SCOT levels increased after
and 3 days of treatment; no
effect 24 h after 5 d
1
Depression of body weight gain
during first 7 wk; increased
liver-to-body weight ratio after
4 wk exposure, no effect at 1, 2,
or 8 wk; no increase in kidney,
brain, and lung; SCOT activity
increased after 4 wk of exposure,
and 2 wk post-exposure, but not
2 wk of exposure, or 8 wk; no
change in BUN. Histology: no
effect on heart, lung, kidney,
brain and liver
Bruckner an dPeterson, 198lb
Bruckner and Peterson, 198lb
Bruckner and Peterson, 198lb
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Reference
Mice
Inhalation
ro
vt
Guinea pig
Inhalation
Inhalation
CFY rats
(both sexes)
1, 10, 100, 1000 ppm
6 h/d x 20 d
1250 ppm H h/d x
6 d/wk (18 exposures)
1000 ppm 1 h/d x
6 d/wk (35 exposures)
265 ppm 6 h/d x
5 d/wk x 1, 3 or
6 mo
No effect on body weight; 1 and
10 ppm caused increase of RBC
count on 10th day; recovery on
day 20; 100 ppm, 1000 ppm -
decrease of RBC count; all doses
increase (HO-10%) of WBC count
on day 10; recovery for all
doses except 1000 ppm; 10 ppm-
1000 ppm - decrease of thrombo-
cytes; histology: 100 ppm -
slight decrease in density
of bone marrow cells and in
megakaryocytes and red cell
elements; 1000 ppm - slight
hypoplasia of red cell elements;
slight to moderate disturbance
in maturity of neutrophils and
thrombocytes, moderate increase
of reticulocytes; no change in
brain, lung, liver, spleen,
or kidney.
Prostration, marked liver
and renal degeneration,
marked pulmonary inflammation
No symptoms; slight toxic
degeneration in liver and
kidney
Bromsulphthalein retention
decreased; Cytochrome P-U50
increased independent of
period of exposure; SCOT
and SGPT activity unaffected
Horiguchi and Inoue, 1977
Smyth and Smyth, 1928
Ungvary et al., 1980
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Reference
CFY rats
(males)
ro
i
CFY rats
(males)
Rats
929 ppm 8 h/d x
5 d/wk x 1 wk,
6 wk, 6 mo.
298, 796, 1592 ppm
8 h/d x 5 d/wk x
4 wk
Subcutaneous 1 cc/kg x 21 d
Cytochrome P-450 increased
independent of exposure
period; no effect on SCOT
or SGPT; aniline hydroxylase
and aminopyrine N-demethylase
activity; cytochrome b[-
concentrations increased.
Histological effects:
dilation of cisternae of
rough endoplasmic reticulum;
increase of autophagons
bodies which was dose and
time dependent; retarded
growth of females but not
males glycogen content
decreased
Cytochrome P-450 increased
with dose
Slight induration at injec-
tion site; 5-14? loss of
body weight; transient slight
drop in RBC and WBC counts;
hyperplasia of bone marrow;
moderate hyperplasia of
malpighian corpuscle in spleen;
marked pigmentation of spleen;
focal necrosis in liver, slight
cloudy swelling in kidney; no
effect on heart, testes, or lungs
Batchelor, 192?
-------
Table 12-2. Subchronic Effects of Toluene (Cont'd)
Species
Route
Dose
Effect
Ref erence
Guinea pig
Subcutaneous
0.25 cc/d x 30-70 d
Local necrosis at injec-
Sessa, 1948
Rabbit
Subcutaneous
ro
t
Rats
Oral
1 cc/kg x 6 d
4 cc/kg
118 mg/kg/d,
354 mg/kg/d,
590 mg/kg/d x 138 d
tion site; survival period:
30-70 days; polypnea and
convulsions during last
days of survival; hemorrhagic,
hyperemic, and sometimes
degenerative changes in
lungs, kidneys, secondary
adrenals, liver, and spleen
Transient slight granulo-
penia followed by granulo-
cytosis; no change in bone
marrow
More marked effect on
granulocytes; all rabbits
dead by end of second day;
no effect on bone marrow
None; parameters observed:
body and organ'weights,
adrenals, pancreas, femoral
bone marrow, lungs, heart,
liver, kidney, spleen,
testes, bone marrow, BUN,
blood counts
Braier, 1973
Wolf et al., 1956
Abbreviations: h = hour; d = day; wk = week; SCOT = serum glutamic oxalacetic transaminase; SGPT = serum
glutamic pyruvic transaminase; WBC = white blood cell; RBC = red blood cell; UDP = uridine 5'-phosphate;
BUN = blood urea nitrogen; mo = month.
-------
In a study by Smyth et al. (1969), inhalation of 4000 ppm technical grade
toluene for 4 hours produced 1 death in 6 rats. In an early study Batchelor
(1927) noted that inhalation of 1600 ppm of toluene for 18-20 hours daily pro-
duced initial effects of instability and incoordination, conjunctivitis, and
lacrimation, then narcosis and mild twitching. A drop in body temperature in
rats, followed by death occurred after 3 days of exposure. At necropsy, a severe
cloudy swelling of the kidneys was found. In this study there were no effects on
liver, heart, or testes, although hyperplasia of- the bone marrow was noted,
suggesting possible contamination of the solvent with benzene.
In the study of Cameron e_t al. (1938), a concentration of 24,400 ppm of
toluene produced a mortality of 60$ and 10$ in rats and mice, respectively, after
1.5 hours of exposure. In another group of rats and mice exposed to 1/2 the
concentration but for a longer period, 6.5 hours, the mortality was 50$ and 100$,
respectively. These two species are probably equally sensitive. Other studies
of mice include that of Svirbely e^t al. (1943), in which the LC50 in Swiss mice
was a concentration of 5320 ppm for 7 hours, and that of Bonnet e_t al. (1979), in
which an LC50 of 6942 ppm for 6 hours of exposure was noted.
In the study of Carpenter ej: al. (1976b), 4 cats survived exposure to
inhalation of 7800 ppm "toluene concentrate" for 6 hours, but during exposure
they showed progressive signs of toxicity, including slight loss of coordina-
tion, mydriasis, and slight hypersensitivity to light within 20 minutes, pros-
tration within 80 minutes, and light anesthesia within 2 hours. All survived the
exposure, and only 1 cat died during the 14-day observation period.
Inhalation of 4000 ppm toluene (purified by distillation) for 4 hours daily
was lethal within a few days to 2 of 3 guinea pigs. The other animal was severely
prostrated. Under the same regimen, animals exposed to less than 1/3 of this
concentration (1250 ppm) for 6 days a week survived 3 weeks of exposure,
12-12
-------
although they .were severely affected. At 1000 ppm, guinea pigs were not affected
even after 35 exposures, although there were slight toxic degenerative changes
in the liver and kidney (Smyth and Smyth, 1928).
Carpenter e_t al. (1944) reported that inhalation of a concentration of about
55,000 ppm was lethal for 6 rabbits in about 40 minutes (range of 24 to
62 minutes).
Von Oettingen ^t al. (1942b) observed that inhalation of 850 ppm of toluene
containing 0.01/S benzene for 1 hour by 6 dogs produced an increase of respiratory
rate and a decrease of respiratory volume. Exposure to 1500 ppm of "toluene
concentrate" for 6 hours daily for 3 days produced only slight lacrimation and
head tremors in dogs. Reduction of the concentration to 1000 ppm did not
alleviate the head tremors (Carpenter ^_t al., 1976b).
Bruchner and Peterson (1981) found an age-dependent sensitivity in rats and
mice. Mice, 4 weeks of age, were found to be more susceptible to exposure of
2600 ppm toluene vapor for 3 hours than 8 and 12 week old animals.
12.1.1.2 Acute Oral Toxicity
An LD50 of 7.53 g/kg and 7.0 g/kg body weight for a single oral dose in rats
has been reported by Smyth e_t al. O969a) and Wolf et al. (1956), respectively.
Withey and Hall (1975) found 5.58 g/kg to be the LD50 in male Sprague-Dawley
rats. Immature 14-day-old Sprague-Dawley rats were more sensitive than young or
mature adult male rats of the same strain to the acute effects of toluene
(analytical grade) in the studies of Kimura e_t al. (1971). These investigators
determined an oral LD50 of 3-0 ml/kg body weight, 6.4 ml/kg body weight, and
7.4 ml/kg body weight for each group, respectively. This age-dependent sen-
sitivity was also noted by exposure to inhalation (see Section 12.1.1.1).
Cameron e_t al. (1938), however, reported that very young rats were more
resistant to toluene than adult animals of the Wistar strain. Thirty-three
12-13
-------
percent of a group of 12 9-day-old rats survived 5.25 hours of exposure to air
saturated with toluene, in contrast to 100% mortality in the same period in a
group of adult rats.
Based on the results of their studies on the oral toxicity of toluene in
animals of different age groups, Kimura e_t al. (1971) suggested a maximum per-
missible limit for a single oral dose of 0.002 ml/kg body weight. This was
obtained by taking 1/1000 of the dose giving the first observable gross signs of
drug action on the central nervous system.
12.1.1.3 Acute Effects from Intraperitoneal Injection
Mortality is produced by a single intraperitoneal injection of toluene in
the range of 0.8 to 1.7 g/kg in rats and mice. In a series of doses of toluene
graduated between 0.79 and 1.65 g/kg and diluted in olive oil, Koga and Ohmiya
(1978) determined an LD50 of 1.15 g/kg body weight in male mice. Respiratory
failure was the main cause of death in these animals. An LD50 of 1.64 g/kg was
reported in female mice by Ikeda and Ohtsuji (1971). Whether the disparity is
due to interlaboratory differences or whether a sexual difference in sensitivity
exists has not been tested. In rats 0.75 cc/kg produced apathy, while 1.75-
2.0 cc/kg produced death from respiratory failure (Batchelor, 1927); 2.0 cc/kg
was a lethal dose in rats, mice (Cameron e_t al., 1938), and guinea pigs
(Wahlberg, 1976).
Savolainen (1978) observed that after an intraperitoneal injection of
radiolabeled toluene, concentration of the label in the central nervous system
(CNS) was highest in the cerebrum. The content of label in the CNS was unde-
tectable by 24 hours after injection, which may be a simulation of acute toluene
intoxication where clinical signs of toxicity are lost within 24 hours.
A temperature-dependent sensitivity to the solvent was observed in adult
rats of both sexes by Keplinger et al. (1959). At 26°C the lethal dose was
12-14
-------
800'rag/kg while at 8°C and 36°C, lethal doses were 530 rag/kg and 225 mg/kg,
respectively. The toxicity of toluene is greater in hot and cold environments.
Whether increased susceptibility to the solvent is caused by the stress of
altered environmental temperature or by altered physiological processes, e.g.,
absorption, diffusion, distribution, or metabolic rate, is unknown.
12.1.1.4 Acute Effects From Subcutaneous Injection
Ranges of 1.25 to 2.0 cc/kg and 5 to 10 cc/kg have been found to produce
mortality in rats and mice, respectively, when injected subcutaneously
(Batchelor, 1927; Cameron et al., 1938). Braier (1973) reported that
4 cc toluene/kg toluene injected into rabbits produced marked transient granulo-
penia within 24 hours and marked granulocytosis and ensuing death in all animals
by the end of the second day. A slight area of induration was seen at the
injection site.
12.1.1.5 Acute Effects from Intravenous Injection
Intravenous injection of 0.2 cc/kg produced 100? mortality in rabbits
(Braier, 1973).
12.1.1.6 Acute and Subacute Effects of Percutaneous Application
Repeated application of undiluted solvent to the rabbit ear or shaved skin
of the abdomen produced slight to moderate irritation (Wolf ^t al., 1956; Smyth
e_t al., 1969a) and increased capillary permeability locally (Delaunay et al.,
1950). Continuous cutaneous contact in the guinea pig resulted in slower weight
gain, karyopyknosis, karyolysis, spongiosis, and cellular infiltration in the
dermis within 16 hours (Kronevi et al., 1979; Wahlberg, 1976). Application to
the abdominal skin of the rat produced hemoglobinuria (Schutz, 1960). Slight
irritation of conjunctival membranes but no corneal injury (Wolf et _al., 1956) or
moderately severe injury (Carpenter and Smyth, 1946; Smyth e_t al., 1969a) fol-
lowed direct application to the eye.
12-15
-------
12.1.2 Subchronic and Chronic Exposure to Toluene
Subchronic and chronic exposures to toluene in animals reveal little toxic
effect with the exception of the study of Fabre e_t al. (1955) in 2 dogs subjected
to much higher concentrations. Svirbely e_t al., (1944) found that repeated
inhalations of 1000 ppm of a solvent mixture containing 30-35^ toluene, 50-60$
benzene, and a small amount of xylene for 28 weeks (7 hours/day, 5 days/week) had
no effect on body weight in rats or dogs. There was no significant increase of
liver volume, and no fat was found in the liver or kidneys; however, narrowing of
perifollicular collars was observed in the spleen (see Table 12-2). Splenic
hemosiderosis was greater than that found after- exposure to benzene (Svirbely
et al., 19*»4).
Neither continuous exposure to 107 ppm toluene for 90 days nor repeated
exposure to 1,085 ppm for 6 weeks (8 hours/day, 5 days/week) affected liver,
kidney, lungs, spleen, or heart in 30 rats, 30 guinea pigs, 4 dogs, or 6 monkeys.
In addition, there were no effects of treatment seen in the brain or the spinal
cord of dogs or monkeys. No significant change was observed in any of the
hematologic parameters (hemoglobin, hematocrit, or leucocyte count). All
animals except 2 of 30 treated rats survived exposure, and all gained body weight
with the exception of the monkeys (Jenkins es_t al., 1970).
Similarly, repeated inhalation of 240, 480, or 980 ppm of "toluene concen-
trate" for 13 weeks (6 hours/day, 5 days/week) produced no treatment-related
organ damage in rats or dogs. SAP, SGPT, SCOT, and blood urea nitrogen (BUN)
activities were normal. Prior treatment with toluene did not render the animals
either more susceptible or more resistent to a subsequent challenge dose of
12,000 ppm (Carpenter £t al., 1976b).
Fabre e_t al. (1955) exposed 2 dogs for 8 hours daily, 6 days a week, to
inhalation of 7.5 mg/1 (2000 ppm) pure toluene for 4 months and then to 10 mg/1
12-16
-------
(2660 ppm) for 2 months. Slight nasal and ocular irritation occurred at the
lower concentration. Motor incoordination preceding paralysis of the extremi-
ties occurred in the terminal phase. Death occurred on days 179 and 180. There
was no effect on gain in body weight, on the bone marrow, adrenal glands,
thyroid, or pituitary gland. Congestion in the lungs, hemorrhagic liver, a
decrease of lymphoid follicles, and hemosiderosis in the spleen were observed.
Glomeruli of the kidney were hyperemic, and albumen was found in the urine.
In a recent chronic 24-month study (CUT, 1980) where Fischer 344 rats of
both sexes were exposed to 30, 100, or 300 ppm 99.98? pure toluene for
6 hours/day, 5 days/week, a battery of clinical chemistry tests (BUN, SAP,
SGPT), hematologic studies, and urinalyses (specific gravity, blood, ketones,
protein, and pH) (see Table 12-3) revealed normal levels in the treated animals
except for two hematologic parameters in the female. Females exposed to 100 or
300 ppm showed significantly reduced hematocrit levels, while the mean corpus-
cular hemoglobin concentration was significantly increased in females exposed to
300 ppm. Body weights in males of the treatment groups were significantly higher
than body weights of controls from approximately week 48 until termination of the
study, while body weights of females in the treatment group were higher than body
weights of controls from week 70 until the final 4 weeks of the study when the
effect disappeared (see Table 12-4). No dose-response relationship was noted.
Mortality in the treatment groups did not differ from controls (14.6$). Although
a variety of proliferative, degenerative, and inflammatory lesions were observed
in various organs, the lesions occurred with equal frequency in all control and
treatment groups, and the authors concluded that no tissue changes could be
attributed to toluene inhalation. Neoplasms were observed frequently in the
lungs and liver, as well as in the endocrine organs, lymphoreticular system,
12-17
-------
Table 12-3. 24-Month Chronic Exposure of Fischer 344 Rats Exposed 6 Hours/Day,
5 Days/Week, to Toluene by Inhalation (CUT, 1980)
I
—A
O5
Group
Number of
Animals
(103
WBC
/cu mm)
,RBC
(KT/eu
HB HCT
mm) (g/DL) ($)
MCV
(Cu. Mic.)
MCH
(MM
g)
MCHC
(*)
Control
30 ppm
100 ppm
300 ppm
Control
30 ppm
100 ppm
300 ppm
Control
30 ppm
100 ppm
300 ppm
Control
30 ppm
100 ppm
300 ppm
89
89
89
90
89
89
89
90
90
90
90
90
90
90
90
90
6
9
6
6
7
8
8
7
4
4
3
4
4
5
5
4
.03
.96*
.54
.53
.51
.66
.13
.50
.04
.59
.91
.21
.93
.40
.74
.87
18 Months
8.757
8.766
8.700
8.894
24 Months
9.866
8.736
9.925
9.407
18 Months
8.022
7.956
7.915
8.010
24 Months
8.397
8.274
8.076
8.090
of Exposure
16.56
16.61
16.47
16.80
of Exposure
18.91
16.58
18.47
18.33
of Exposure
15.67
15.77
15.75
15.78
of Exposure
16.46
15.89
15.94
15.86
(Males)
43.10
42.42
41.93
42.34
(Males)
51.78
46.51
51.61
47.35
(Females)
41.70
41.25
40.83
41.20
(Females)
44.99
43.06
42.47*
42.02**
50
49
49
48
51
52
50
50
53
52
52
52
54
53
53
53
.4
.6
.5
.8**
.2
.5
.7
.9
.0
.8
.7
.4
.7
.3
.9
.1
18.87
18.90
18.91
18.85
19.
19.
18.
19.
19.
19.
19.
19.
19.
19.
19.
19.
24
05
67
44
49
77
85*
63
50
11
68
52
38.04
38.82
38.93
39.30**
37.87
36.33
38.84
39.33
37.26
37.90*
38.24*
37.98
36.10
36.42
37.08
37.46*
"Statistically significant difference from control (P <0.05)
"Statistically significant difference from control (P <0.01)
Abbreviations: WBC = white blood cell count; RGB = red blood cell count; HB - hemoglobin concentration;
DL = 100 milliliters; HCT = hematocrit; MCV = mean corpuscular volume; Mic. = micron; MCH = mean corpuscular
hemoglobin; MCHC = mean corpuscular hemoglobin concentration.
-------
Table 12-4. 24-Month Chronic Exposure of Fischer 344 Rats Exposed 6 Hours/Day,
5 Days/Week, to Toluene by Inhalation (CUT, 1980)
Males
Control
30 ppm
100 ppm
300 ppm
89
89
89
90
Mean Body Weight in Grains
Group Number Weeks of Exposure Total
Animals 0 26 52 78
100 104 Weight
Change
141
141
141
142
340
349*
351"
341
384
396»»
404**
403**
426
-445**
447**
446**
430
456**
454**
451**
430
454«*
452**
445
286
314**
312**
304**
Females
Control
30 ppm
100 ppm
300 ppm
90
90
90
90
109
109
109
109
203
191**
194
195**
213
211
211
211
214
246**
248**
248**
260
272**
272**
271**
265
273*
275
272
156
164
166
163
"Statistically significant difference from control (P <0.05)
••Statistically significant difference from control (P<0.01)
12-19
-------
mammary gland, integument, testis, and uterus. Chronic progressive nephropathy
was present in the urinary system (CUT, 1980).
Although this study was comprehensive and is the only chronic study of
toluene in laboratory adrenals, there are several deficiencies in this study
which might becloud interpretation. The high spontaneous incidence (16/&) of
mononuclear cell leukemia in aging Fischer 344 rats reported by Coleman and
coworkers (1977) suggests that this strain may be inappropriate for the study of
a chemical that might be myelotoxic. A high testicular interstitial cell tumor
incidence (66.2$ reported by Coleman e_t al., 1977 and Q5% bilaterial tremors
reported by Mason £t al., 1971) atuomatically removes this organ from any assess-
ment of carcinogenicity, although this might not be a target organ for toluene.
Therefore it would be an irrelevant point. The low mortality of rats in this
study (14.6/&) differs from the mortality rate (up to 25$) associated with main-
taining these animals under barrier conditions (NCI, 19 a,b,c). If these
animals were not raised under barrier conditions (which is not stated), then
still higher mortality rates could be expected in this age group of Fischer 344
rats. No quality assurance of the study was extant after 6 months into the
chronic study (CUT public review of toluene study, May 12, 1981).
A higher exposure level, 1000 ppm, was dropped from this study based on a
pilot investigation which revealed that body weight loss might interfere with
maintenance of these animals for 24 minutes. Lack of a group at this level,
where behavioral and central nervous system effects have been reported, or a
group at some intermediate level precluded information on a possible effect/no-
effect level.
In the only subchronic oral study, female rats fed up to 590 mg toluene/kg
by intubation for periods of up to 6 months did not show ill effects as deter-
mined by gross appearance, growth, periodic blood counts, analysis for blood urea
12-20
-------
nitrogen, final body and organ weights, bone marrow counts, or histopathological
examination of adrenals, pancreas, lungs, heart, liver, kidney, spleen, and
testis (Wolf e_t al., 1956).
12.2 EFFECTS ON LIVER, KIDNEY, AND LUNGS
Organ effects in the kidney and, possibly in the liver and lungs after
higher doses, have been reported.
12.2.1. Liver
No histological damage was observed after subchronic and chronic inhalation
of 1000 ppm of a solvent mixture containing 30-35$ toluene for 28 weeks, 980 ppm
of "toluene concentrate" for 13 weeks, 1085 ppm of toluene for 6 weeks, and
300 ppm of 99-98$ pure toluene for 24 months in a variety of species in studies
described in Subsection 12.1.2 (Svirbely et al., 1944; Carpenter £t al., 19?6b;
Jenkins ejb al., 1970; CUT, 1980). Furthermore, no liver damage was detected in
feaale rats after subchronic daily oral doses of 590 mg/kg for 6 months (Wolf
et, al., 1956). Two preliminary reports (abstracts of presentations) from the
laboratory of Bruckner and Peterson noted no effect on hepatorenal function. In
a regimen mimicking solvent "sniffing," male rats and mice were exposed to
12,000 ppm toluene for 7 10-minute periods (with 20-minute solvent-free periods
intervening) 5 days/week for 8 weeks. No organ pathology was found. Lactic
dehydrogenase, SGPT activities, BUN content, and liver triglyceride content were
normal (Bruckner and Peterson, 1978). In another study, inhalation of 4000 ppm
toluene (3 hours/day, 5 times weekly) for up to 8 weeks failed to reveal toluene
induced hepatorenal injury by a battery of toxicological tests (SCOT activity,
BUN levels, urinary glucose and protein concentration, and urinary cell count)
and upon histopathological examination of the liver, kidney, and lung (Bruckner
and Peterson, 1976).
12-21
-------
Although these early reports revealed no effect on SCOT activity or BUN
levels in mice and rats, a recent paper (Bruckner and Peterson, 1981b) noted an
increase in SCOT activity in mice and rats during intermittent exposure to
1200 ppm toluene (see Section 12.3). Increase in LDH activity was seen in rats
and decrease in BUN levels was seen in mice. No histological changes were
observed, but an increase of organ weight to body weight was found.
In a study in which reagent grade toluene that was dissolved in corn oil was
injected intraperitoneally in doses of 150, 300, 600, or 1200 mg/kg into adult
male guinea pigs, there was no change in serum ornithine carbamyl transferase
activity at any dose level in blood collected.24 hours later. Histological
examination revealed no liver abnormalities or lipid accumulation with the
exception of the highest dose where there was evidence of lipid accumulation
(Divincenzo and Krasavage, 197^).
Two hours after male rats (weighing 150 to 300 g) were administered
2600 umol/100 g body weight of toluene in mineral oil by gavage, there was no
evidence of injury to the microsomal function of the liver. There was no effect
on protein synthesis, cell sap RNA, glucose 6-phosphatase, oxidative
demethylase, nicotinamide adenine dinucleotide phosphate (NADPH) neotetrazolium
reductase, or lipid conjugated diene content of microsomes (Reynolds, 1972).
Inhalation of 300 ppm toluene (6 hours/day, 5 days/week) for 15 weeks slightly
increased cytochrome P-450 content in liver, appreciably enhanced ethoxycoumarin
o-deethylase, and at the end of exposure increased UDP glucuronyltransferase
activity. The content of toluene in perirenal fat tended to decrease during
continued exposure, while the presence of toluene in the brain was detected
throughout exposure. The diminution of toluene content in perirenal fat at the
same time that drug metabolizing enzymes increased suggests an adaptation to
continued presence of thee solvent (Elovaara et, al., 1979).
12-22
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Continuous cutaneous contact with a dose of 2.0 ml toluene, which was com-
pletely absorbed within 5 to 7 days, produced no change in liver morphology
(Wahlberg, 1976).
Although the studies just cited indicate the absence of toluene-induced
toxicity, there are others which suggest a slight toxic effect. In a study by
von Oettingen et al. (1942b) inhalation of concentrations of 600 to 5000 ppm
toluene containing 0.01$ benzene for 5 weeks (7 hours/day, 5 days/week) in rats
caused an enlargement of the liver (increase of weight and volume) in a dose-
dependent manner 16 hours after the last exposure. Histologically, there was a
progressive decrease of density of the cytoplasm in the liver cells as the
concentration of toluene increased. These observations were not seen in rats
sacrificed 2 weeks after the last exposure. No evidence of hyperemia was seen in
the liver. Matsumoto e_t al. (1971) reported an increase in liver weight and
liver weight to body weight ratio in rats exposed 9 hours/day, 6 days/week for
43 weeks to 2000 ppm toluene vapor. This was not noted at lower doses (100 ppm
or 200 ppm).
In the study of Fabre et' al. (1955) 2 dogs exposed for 4 months
(8 hours/day, 6 days/week) to inhalation of 7.5 mg/1 (2000 ppm) pure toluene
and, subsequently, to 10 mg/1 (2660 ppm) for 2 months had hemorrhagic livers.
Tahti e_t al. (1977) observed that inhalation of 1000 ppm toluene
8 hours/day, for 1 week increased SCOT and SGPT activity and induced metabolic
acidosis in rats.
Histological changes in the liver were found when male CFY rats were
injected intraperitoneally with 0.05 or 0.1 ml/100 g body weight of analytical
grade toluene for up to 4 weeks. There was a dose-dependent increase in the
number of mitochondria per unit of cytoplasmic area in the liver. Total area,
nuclear density, and nucleus/cytoplasmic ratio increased at the higher dosage.
12-23
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Dose-dependent decreases in nuclear volume were seen after intraperitoneal or
subcutaneous injection, with subcutaneous injection being less effective than
intraperitoneal injection. The authors suggested that the considerable accumu-
lation of mitochondria was related to increased metabolism of the liver and that
oxidative detoxification of the solvent might involve mitochondrial enzymes as
well as hepatic microsomal enzymes (Ungvary ^t _al., 1976). In an earlier paper
Ungvary e_t _al. (1975) found that intraperitoneal or subcutaneous administration
of toluene produced degenerative changes, i.e., separation of ribosomes and
vacuolar dilation of the rough endoplasmic reticulum. In these studies the
higher concentrations of toluene also decreased glycogen content. Following
discontinuation of exposure, the hepatic changes indicating increased load on
detoxification processes (increased succinate dehydrogenase (SDH) activity,
increase of mitochondria and smooth endoplasmic reticulum, decreased glycogen
content) as well as degeneration (dilation of endoplasmic reticulum, accumu-
lation of autophagous vacuoles) rapidly regressed, indicating that the toxic and
liver loading effects of toluene are reversible. The regenerative property of
the liver after hepatectomy was not significantly affected by exposure to toluene
(Hudak et al., 1976).
In a more recent study by Ungvary et al. (1980) where male CFY rats were
exposed to inhalation of 265 ppm (6 hour daily), 929 ppm or 1592 ppm (8 hour
daily), analytical grade toluene and female rats were exposed to lowest dose only
(five times a wseek up to 6 months) growth was inhibited in male's at the higher
concentration and in females only at the low dose. No abnormal histological
changes were found in the liver. Liver weight was increased by treatment. Signs
of adaptive compensation that were observed include proliferation of smooth
endoplasmic reticulum, increased cytochrome P450 and cytochrome b_ activity,
increased aniline hydroxylase activity and aminopyrine N-demethylase activity.
12-24
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These changes which were dose-dependent and reversible showed no or slight
dependence on exposure time. There was no effect on SCOT or SGPT activity. The
authors concluded from their latest studies that subchronic toluene exposure to
toluene vapors has no specific hepato toxic effect. The results of toluene
inhalation corroborated earlier histological findings (by the intreperitoneal or
subcutaneous route of this laboratory except that necrotic areas were not found
after inhalation. Whether this reflects the different route of exposure or the
higher concentration of toluene administered intraperitoneally has not been
ascertained.
12.2.2 Kidney
No histological effects of renal toxicity were seen in subchronic inhala-
tion studies (see Table 12-2) in mice exposed to 1000 ppm for 20 days (Honuguchi
and Inoue, 1977), in rats, guinea pigs, dogs, or monkeys exposed to 1085 ppm for
6 weeks (Jenkins e_t al., 1970), in rats and mice exposed to 4000 ppm vapors for
8 weeks (Bruckner and Peterson, I198lb), or in chronic inhalation studies in rats
exposed to 300 ppm for 24 months (CUT, 1980). Neither was any effect of toluene
observed in renal histology after subchronic oral dosing of 590 mg/kg for
138 days in rats (Wolf et al., 1956).
Pathological renal changes, however, have been observed in some studies.
Von Oettingen et _al. (1942b) found increasing numbers of casts in the collecting
tubules of rat kidneys during inhalation of concentrations ranging from 600 ppm
to 5000 ppm for 5 weeks (7 hours daily, 5 days/week). A few casts in the kidney
were seen after the third week of exposure at 600 ppm and earlier in the higher
doses. Appreciable fat in the convoluted tubules and hyaline casts in the
collecting tubules of the kidney were observed in dogs after inhalation of 200 to
600 ppm for approximately 20 daily 8-hour exposures, then inhalation of 400 ppm
for 7 hours/day, 5 days/week for 1 week, and finally to 850 ppm for 1 hour. In
12-25
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the studies of Matsumoto e_t al., (1971) exposure of rats to inhalation of
2000 ppm for 8 hours/day, 6 days/week for 43 weeks produced histopathological
findings of hyaline deplete in renal tubules. There was an increase of kidney
weight and an increase of the ratio of kidney weight to body weight.
After inhalation of 7.5 mg/1 toluene 8 hours/day, 6 days/week, for 4 months
and followed by exposure to 10 mg/1 during the remaining two months, hyperemic
renal glomeruli and albuminuria were observed at autopsy in dogs by Fabre e_t al.
(1955). Inhalation by guinea pigs of 1000 ppm (of distillation pure toluene)
4 hours/day, 6 days/week, for a total of 35 exposures produced slight toxic
degeneration in the kidney. Eighteen exposures at a higher dose of 1250 ppm
produced more marked degeneration (Smyth and Smyth, 1928). Degeneration of
convoluted tubular epithelium in guinea pigs exposed by the subcutaneous route
was reported in an abstract of a paper by by Sessa (1948).
12.2.3 Lungs
No histological damage of the lungs were seen after inhalation of 1000 ppm
vapors for 20 days in mice (Hougnchi and Inoue, 1977), inhalation of 1085 ppm for
6 weeks in rats, guinea pigs, dogs, or monkeys (Jenkins e_t al., 1970), inhalation
of 4000 ppm for; 8 weeks in rats and mice (Bruckner and Peterson, 198lb), 300 ppm
for 24 months in rats (CUT, 1980), a ingestion of 590 mg/kg for 138 days in rats
(Wolf et al., 1956).
Irritative effects on the respiratory tract, however, have also been
reported (Browning, 1965; Gerarde, 19595 Fabre et al., 1955; von Oettingen
et al., 1942b).
Marked pulmonary inflammation was seen in guinea pigs after exposure to
inhalation of 1250 ppm distillation pure toluene 4 hours daily, 6 days/week, for
18 exposures (Smyth and Smyth, 1928).
12-26
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Hemorrhagic, hyperemic, and sometimes degenerative changes in the lungs
have been observed in guinea pigs after a subcutaneous injection of 0.25 cc of
toluene daily for 30 to 70 days as reported in an abstract (Sessa, 19^8).
Congestion in the lungs of dogs which had undergone repeated exposure to concen-
trations of 200 to 600 ppm toluene and to a final exposure by inhalation of
850 ppm for 1 hour, and pulmonary lesions in rats after 1 week of inhalation of
2500 ppm (7 hours/day, 5 days/week) were reported by von Oettingen et al.,
(W2b).
Congestion in the lungs was noted by Fabre et, al. (1955) in dogs and in
rabbits at the higher doses.
12.3 BEHAVIORAL TOHCITY AND CENTRAL NERVOUS SYSTEM EFFECTS
Excessive depression of the central nervous system has been linked with
acute exposure to high levels of toluene. A concentration of 20,000 ppm toluene
was lethal to rats after 30 to 50 minutes of exposure with death attributed to
depression of the CNS (Kojima and Kobayashi, 1975, cited in NRS, 1980).
Inhalation of 12,000 ppm of "toluene concentrate" containing 0.06$ benzene was
lethal to rats following tremors which appeared within 5 minutes of exposure and
prostration which occurred within 15 minutes of exposure (Carpenter et al.,
1976b).
A dose-related effect on instability, incoordination, and narcosis was
found in rats exposed 18-20 hours daily to toluene concentrations of 1600 ppm and
1250 ppm. No symptoms were seen at 1100 ppm (Batchelor, 1927). Carpenter et al.
(1976b) reported that rats were unaffected by exposure to inhalation of 1700 ppm
of a "toluene concentrate" for U hours and suffered only slight incoordination at
3300 ppm. Dogs were unaffected by exposure to vapors of 760 ppm for 6 hours, but
exhibited head tremors at 1500 ppm. After inhalation of 7800 ppm "toluene
concentrate" for 6 hours, cats exhibited loss of coordination followed by
12-27
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prostration and, finally, light anesthesia within 2 hours. All survived
exposure.
Within 10 seconds after 1 intravenous injection of 0.07 cc toluene per kg
body weight in 1 dog, generalized rigidity with hyperextension of the back was
noted in a study made by Baker and Tichy (1953). Recovery occurred within
12 minutes. A second injection 5 days later produced a similar sudden rigidity.
When a series of 10 doses of 0.07 cc toluene/kg was given intravenously every 3
to 5 days to another dog, the effect was rigidity in the animal and twitching of
the extremities. Recovery occurred in 5 to 10 minutes. At necropsy after the
last dose was given, cortical and cerebellar atrophy was found. Marked shrinkage
and hyperchromaticity of many cortical neurons, patchy myelin pallor, and frag-
mentation, especially in perivascular areas, were found. Multiple fresh
petechiae, especially in the white matter, was seen. There was a decrease and
degeneration of Purkinje cells in the cerebellum (Baker and Tichy, 1953).
In the section on effects on humans (Section 10.1), inhalation of readily
available thinners by young adults has been described as a prevalent practice
which typically affects the CNS. Inhalation of solvent mixtures containing
toluene in the laboratory rat have demonstrated similar effects. Inhalation of a
mixture of solvents containing 25% methylene chloride, 5% methanol, ^3% heptane,
and 23% toluene for 10 minutes (60 to 226 mg/liter) caused a decrease in rearing
and grooming, the appearance of ataxia, abnormal scratching, hind limb flaccid
paralysis, and, finally, unconsciousness in male Fischer rats. Cumulative
effects were noted with 4 intermittent 10 minute exposure periods with
15 minutes between exposures. When the interval between . each exposure was
increased to 40 minutes, recovery was almost complete (Pryor e_t al., 1978).
Subchronic exposure to a thinner containing toluene impaired acquisition of
a complex behavior. Rats inhaled 50,000 ppm of a readily available commercial
12-28
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paint thinner composed of 42? toluene, 25% methanol, 10$ methyl iso-butyl ketone,
and minor amounts of other solvents for 4, 8, or 16 weeks (twice-daily for
10-minute periods, 5 days a week) and then were observed for acquisition of
temporal discrimination in a differential reinforcement of low rate schedule
(DRL 20). In this test, the animal is rewarded for single responses, e.g., bar
press made every 20 seconds. The results suggested that persistent inhalation of
thinner vapors impaired temporal discrimination when the animals were tested
within a relatively short time after the period of inhalation. However,
responses in rats that had a period of rest after exposure did not differ from
controls (Colotla and Bautista, 1979).
Studies in laboratory animals have shown that toluene contributes to the
symptoms of thinner toxicity. In the studies of Peterson and Bruckner (1978),
impairment of cognitive functional and muscular coordination were used to
monitor CNS depression and narcosis. Behavioral performance (visual placing,
grip strength, wire maneuver, tail pinch, and righting reflex) in mice exposed to
3980 ppm (15 mg/liter) toluene for 3 hours decreased over time of exposure,
which was inversely correlated with toluene concentration in brain tissue.
Concentration of toluene in the brain increased exponentially with the length of
exposure and similarly decreased after termination of exposure, as did levels of
toluene in liver and blood (see Figure 12-1). A single 10-minute exposure to a
higher concentration (10,615 ppm) followed the pattern elicited by the lower
concentration for a longer period. Recovery of behavioral performances occurred
as solvent concentration in the brain decreased after exposure. Buckner and
Peter (198la) noted that ataxia, immobility in the absence of stimulation,
hypnosis with difficult arousal and unconsciousness were apparent in mice at
concentrations in blood of 40-75 ug/g, 75-125 yg/g, 125-150 ug/g and >150 lug/g,
respectively, as measured by the air bleb method.
12-29
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CD
2
800-i
600-
400-
P 200-
TISSUE LEVELS
BRAIN
— LIVER
— BLOOD
0123
HOURS OF EXPOSURE
T
2
i
3
HOURS POSTEXPOSURE
100-1
50-i
a:
UJ
o.
NORMALIZED TISSUE LEVELS
0
1
1
1
2
i
3
i
1
2
3
i
4
HOURS OF EXPOSURE HOURS POSTEXPOSURE
LU
I
600-1
BRAIN CONCENTRATION VERSUS
CHANGE IN PERFORMANCE SCORE
BRAIN
^PERFORMANCE
0 1 2
HOURS OF EXPOSURE
1234
HOURS POSTEXPOSURE
-5
-4
Figure 12-1.
Toluene Levels in Tissue and Behavioral Performance (Mice were con-
tinuously exposed for 3 hours to an intoxicating concentration of
toluene (15 mg per liter of air). Groups of animals were analyzed for
air bleb concentration, reflex performance, and tissue levels after
15, 30, 60, 120, and 180 minutes of exposure and 1, 2, and 4 hours
postexposure. Figure 12-1A shows toluene levels in liver, brain, and
blood. Figure 12-1B shows toluene normalized to the highest mean
level in each tissue. Figure 12-1C compares brain levels of toluene
with change in performance of the animals. Lines represent means.
N = 7 mice on all but 4 hours postexposure, in which case, N = 6.)
(Peterson and Bruckner, 1978)
12-30
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Bruckner and Peterson (198lb) observed that the onset of narcosis and the
depth of CNS depression was dose-dependent. In mice exposed to inhalation of
12,000 ppm toluene the rapidity and depth of depression was greater than that of
mice exposed to 5200 ppm. In the latter group these parameters exceeded those
found in mice exposed to one-half the concentration (2600 ppm). Recovery was
rapid. After exposure to 12,000 ppm for 20 minutes mean performance levels
scored prior to exposure were resotred within approximately one-half hour in
4-week old rats.
A study was made by Peterson and Bruckner (1978) in mice to mimic the
conditions typical of human solvent-sniffing abuses. During intermittent expo-
sure to 10,615 ppm (5 minutes of exposure followed by 10 minutes without toluene
or 10 minutes of exposure followed by 20 minutes without toluene) for approxi-
mately 3 hours or 11,9^2 ppm (10 minutes of exposure followed by 20 or 30 minutes
without toluene) for approximately 3 hours, reflex performance became progres-
sively lower throughout the experimental period for the regimens allowing
20 minutes or less toluene-free intervals. A 30-minute toluene-free interval
between exposures permitted almost unimpaired performance indicating complete
recovery between exposures (Peterson and Bruckner, 1978).
In a later acute study Bruckner and Peterson (198la) exposed mice and rats
to 7 consecutive cycles each cycle consisting of 10-minute exposure to
inhalation of 12,000 ppm toluene followed by a 20-minute solvent-free recovery
period. Unconditioned performance and reflexes of the animals were tested
immediately prior to an following exposure. The mice showed almost complete
recovery during the course of treatment while performance scores of rats
exhibited a progressive decline. The authors speculated that the rapidity of
recovery in mice might be attributed to the higher circulatory, metabolic, and
respiratory rates of mice; that the increasing CNS depression seen in rats over
12-31
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the 3-hour period of intermittent inhalation might recur from a progressive
accumulation of the chemical. Substantial residual quantities in the brain
1 hour post exposure had been noted by the same authors in an earlier paper
(Bruckner and Peterson, 1981a).
In a subchronic study, groups of 6 mice or 4 rats with comparable numbers of
controls were subjected to 7 consecutive cycles (as described in the perceding
paragraph) on a daily basis, 5 times a week for 8 weeks. Depression of body
weight gain was seen in both rats and mice during' 8 weeks of the intermittent
toluene exposure. An increase in SCOT levels was noted in rats and mice but the
increase in mice was not statistically significant. An increase in LDH was seen
only in rats exposed to toluene at all sampling intervls. BUN levels in rats
were unaffected by treatment whereas BUN levels in mice were consistently lower
during the period of exposure. Recovery ocurred within 2 weeks post exposure.
There were noe ffects on hair, lung, liver, heart, or kidney histology, although
a depression in gain of age weights (kidney, brian, lung) was noted in treated
mice and rats (Bruckner and Peterson, 198la).
After a single exposure to 800 ppm toluene for 4 hours, unconditioned
reflexes and simple behavior (corneal, grip, and righting reflexes, locomotor
activity, and coordination) began to fail (Krivanek and Mullin, 1978). In these
studies, male rats were exposed to concentrations of 0, 800, 1600, 3200, and
6400 ppm and tested at 0.5, 1, 2, and 4 hours during exposure and 18 hours after
exposure (see Table 12-5).
Concentrations of toluene as low as 1 ppm administered 6 hours/day
depressed wheel turning performance (a spontaneous activity) after 10 days of
exposure in adult male mice (Horiguchi and Inoue, 1977). No effect on body
weight was seen at any of the dosages used (1, 10, 100, and 1000 ppm) during the
20 daily exposures. However, there were alterations in blood elements in animals
exposed to 10, 100, and 1000 ppm, which are noted in Section 12.5.
12-32
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Table 12-5. Effect of Toluene on Behavior
Route
Species
Dose
Effect
Reference
inhalation Wistar rats
inhalation Sprague-Davley rats
inhalation rats (male)
inhalation rats
inhalation rats (male)
inhalation rats (male)
inhalation rats (male)
574, 11148, 2296, and
4595 ppm
150 ppm for 0.5, 1, 2 or
4 h
550 to 800 ppm for
4 h/d x 2 wk
4000 ppm 2 h/d x 60 d
3000 ppm for 4 h
(no effect at 1000 ppm)
3200 ppm for 4 h
1600 ppm for 4 h
300 ppm for 4 h
Deficit in multiple
response schedule
.1 ni ti al s timul a ti on
followed by depression in
multiple response schedule
No effect on avoidance
response
Multiple response schedule
No effect on CRF or FR30
Deficit in DHL 12 sec
schedule
Deficit in conditioned
avoidance response
Deficit conditioned
avoidance response
Mo-effect-level
Deficit in unconditioned
reflexes and sinple
behavior
Colotla and Sautista,
1979
Geller s_t al., 1979
3attig and Grandjean, 1964
Ikeda and Miyake, 1978
Shigeta e_t ai., 1978
Krivanek and Mullin, 1973
Srivar.ek and Mullin, 1973
inhalation rats
i.p.
mice (male)
inhalation mice
inhalation mice
inhalation mice (male)
inhalation mice
4-5 ml in 40-50 1 of air
for 1/2 h/d x 7.6 d
0.96 g/kg
3980 ppm for 3 h
10,615 ppm for 10 min
4,000 ppm for 3 h/d x
5 d/wk for 3 wk
1, 10, 100, 1,000 ppm for
6 h/d x 10 d
2650 ppm
Induced forced turning
Loss of righting reflex in
5/7 in 20.6 + 1.5 min
Interval from loss of
righting reflex to re-
covery 35.0 * 3.2
14.3$ lethality in 24 h
Deficit in visual placing,
grip strength, wire maneuver
tail pinch, righting reflex
Deficit on an accelerating,
rotating bar
Deficit in wheel-turning
Ishikawa and Schnidt, 1973
Koga and Ohmiya, 1978
Peterson and Bruckner,
1978
Bruckner and Peterson,
1976
Horiguchi and Inoue, 1977
Causes mice to fall on side raustov, 1958
Abbreviations: h = hour; d = day; wk = week; i.p. ^ intraperitoneal; min = minute; sec = second.
12-33
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An exposure as small as 1 ppm of toluene suppressed wheel-turning activity
whereas exposure to 100 ppm benzene approximated the depression caused by
exposure to 10 ppm toluene; therefore, the narcotic action of toluene appears to
be greater than benzene (Horiguchi and Inoue, 1977).
The positive findings at 1 ppm reported by Horiguchi and Inoue (1977) and
the change of motor chronaxies in rats exposed continuously to 4 ppm toluene for
85 days (Gusev, 1967; cited by NRC) have been questioned in the NRC (1980) review
as being at variance with negative effects observed' in other experiments at much
higher levels. For example, Ikeda and Miyake (1978) did not find any effect on
spontaneous activity in their studies of repeated-exposure to 4000 ppm toluene in
rats. However, the behavioral tests of the latter authors were carried out
4 days after final exposure. Rapid recovery of behavior after exposure (Shigeta
e_t al., 1978; Peterson and Bruckner, 1978; and Ishikawa and Schmidt, 1973) may
explain the disparate results just cited.
A single exposure to 3000 ppm toluene for 4 hours disrupted established
timing of bar pressing in a conditioned avoidance response test in adult male
Wistar rats (Shigeta e_t al., 1978). Concentrations of 0 and 1000 ppm toluene did
not affect this operant behavior. At 3000 ppm increased response and shortening
of the inter-response-interval were noted, but no change in shock counts was
seen. Behavioral recovery occurred 1 hour after exposure. Krivanek and Mullin
(1978) reported a decrease in conditioned avoidance reflexes after inhalation by
male rats of 3200 ppm toluene for 4 hours, but they reported no effect at dose
levels of 1600 or 800 ppm.
In another study of operant behavior, Colotla and Bautista (1979) used rats
that had been trained to reinforced bar pressing in a multiple schedule com-
prising fixed ratio (FR) 10 and differential reinforcement of low rates (DRL) 20-
second components with 60-second time out between reinforcement periods. Five
12-34
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trained adult Wistar rats were exposed to concentrations of 574, 1148, 2296, and
4595 ppm toluene. Test sessions were 36 minutes long. Control sessions inter-
vened between solvent exposure sessions to assess recovery. A decrease in
response of FR performance and an increase of frequency rate of the DHL component
were observed with all doses in a dose-dependent manner. No residual effects
were observed. An effect on behavioral rate was shown.
A lower concentration, 150 ppm toluene, for periods of 0.5, 1, 2, or 4 hours
affected a multiple fixed ratio—fixed interval schedule of reinforcement in
3 male Holtzman, Sprague-Dawley rats. An initial enhancement of FR and FI rates
occurred during shorter exposure periods followed by a decrease in rates during
longer exposure periods (Geller e_t al., 1979); however, only a small number of
animals was used, and the response was not uniform. Battig and Grandjean (1964)
found no effect on acquisition or consolidation of an avoidance response after
inhalation of toluene varying from 550 to 800 ppm, 4 hours/day for 2 weeks, by
6 adult male rats. Continued exposure at similar levels for another week
effected a somewhat slower extinction of the avoidance response.
Repeated exposure of rats to inhalation of 4000 ppm toluene, 2 hours daily
for 60 days, did not affect spontaneous locomotor activity, emotionality, or
learning on 2 operant schedules: memory in a continuous reinforcement schedule
(CRF) where every bar press was rewarded by food and extinction of a fixed ratio
(FR 30) schedule where only a bar press every 30 seconds was rewarded. This
exposure did impair learning on a third operant schedule, acquisition of a
differential reinforcement of a low rate of responding (DRL 12 seconds) schedule
that required the rat to allow at least 12 seconds between responses to receive a
reward. Impaired performance was present 80 days after final exposure. Exposure
to toluene appears to more seriously affect higher levels of cognition. Histo-
logical examination of the brain did not reveal any changes (Ikeda and Miyake,
1978).
12-35
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Inhalation of 4000 ppm toluene by mice for 3 hours/day, 5 times weekly for
up to 8 weeks, caused a steady deterioration of performance on an accelerating,
rotating bar during the initial hour of each session of exposure. Solvent levels
in blood and liver increased during each exposure session and decreased quickly
after exposure (Bruckner and Peterson, 1976).
Circling (forced turning) was produced within a mean of 7.6 days in
90-day-old male Sprague-Dawley rats (n=10) by repeated toluene inhalation (4-
5 ml in 40-50 liters of air) for 1/2 hour per day.- After 15, 21, or 34 days of
recovery, the rats were reexposed daily to toluene. When only 15 days of
recovery had elapsed, the number of exposures required to elicit forced turning
was significantly less than the number required to acquire the behavior
originally. This effect was not seen when a longer period of recovery had
elapsed. Thus, toluene has a residual effect. Furthermore, the effect is
reversible. This turning was not associated with any histological lesions in the
brain (Ishikawa and Schmidt, 1973).
The effect of toluene on electrical, as well as behavioral, parameters in
the brain was studied by Contreras e_t al. (1979). Twenty cats were exposed for
up to 40 days (10-minute periods, 7 days/week) to 25.5 to 204.7 mg/l/min
(approximately 7,000 to 52,000 ppm) toluene administered through a tracheal
cannula in increments of 25.5 mg/l/min with 10-minute recovery intervals between
exposures. During the first seconds of acute intoxication at 12,000 ppm the
behavior consisted of restlessness, polypnea, coughing, sneezing, and vegetative
responses consisting of salivation, mydriasis, and lacrimation. Ataxia appeared
2 minutes later, ending with postural collapse. Changes of electrical activity
at this point were found in the anterior lobe of the cerebellum, the amygdala,
and the visual cortex. There was no behavioral response to light, sound, or pain
stimuli (see Table 12-6).
12-36
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Table 12-6. Central Nervous System Effects of Toluene
Route
Species
Dose
Effect
Reference
inhalation
cats
inhalation
inhalation
inhalation
inhalation
rats
rats (male)
rats and mice
rats (male)
Sprague-Dawley
n = 6
ca. 7,000 to 52,000 ppm
10 min/d x 40 d
1000, 2000, or 4000 ppm
for 4 h
2000 ppm toluene for
8 h/d x 1 wk
265 ppm
500 ppm 6 h/d x 3 d
Killed 16-18 h after
exposure
1000 ppm 6 h/d x 5 d
decapitated 4 h after
exposures
Restlessness
Autanomic nervous system
stimulation, ataxia,
collapse
EEC changes
Seizures
EEC changes
Increased excitability
Changed sleep cycle
Increased pulse rate
Decreased threshold for
Bemegri de-induced
convulsions
Threshold affecting CMS
Increase of catechoiamines
in lateral palisade
zone of median eminence
Increase of catecholamines
in subependymal layer of
median eminence
Increase of FSH
Contreras et al., 1979
Takeuchi and Hisanaga,
1977
Takeuchi and Suzuki,
1975
Faustov, 1958
Andersson jit al., 1980
Abbreviations: min = minute; d = day; h = hour; wk = week; EEC = electroencephalogram; FSH = follicle-stimulating
hormone; CNS = central nervous system.
-------
Threshold dose for restlessness was approximately 7,000 ppm. No behavioral
response to external stimuli occurred at approximately 39,000 ppm. Recovery
from ataxia occurred 12 minutes after removal from exposure. With repeated
exposure, at a concentration of 102.3 mg/I/minutes, hypersynchronous rhythms
spread from the amygdala to the reticular formation, visual cortex, and
cerebellum, and electrical activity appeared in the gyrus cinguli, which
coincided with a display of hallucinatory behavior. These EEC and behavioral
signs are similar to complex partial seizures in man (Contreras e_t al., 1979).
Takeuchi and Hisanaga (1977) found that 1000, 2000, or 4000 ppm toluene
administered for 4 hours to groups of 4 or 5 male Vistar rats elicited changes in
the sleep cycle, altered cortical and hippocampal EEC rhythms, and increased
pulse rates. All phases of sleep were disturbed at a concentration of 2000 and
4000 ppm, while 1000 ppm deterred entry of sleep into the slow-wave phase but
facilitated entry into the paradoxical phase.
A similar observation was made by Fodor e_t al. (1973), where an increased
percentage of REM during sleep was found in female albino rats during exposure to
1000 ppm. A concentration of 1000 ppm decreased cortical and hippocampal compo-
nents of the EEC (Takeuchi and Hisanaga, 1977). Exposure to 2000 ppm toluene
increased cortical fast components and1 hippocampal components, whereas exposure
to 4000 ppm increased the hippocampal fast component as well. At 4000 ppm
excitability measured by rearing reactions (standing on hind legs) increased
during the first hour of exposure, but this phase was followed by a depression
and the rats were unable to stand or walk. Excitability increased again after
exposure. At 2000 ppm only increased excitability was observed. At 1000 ppm
excitability was not increased significantly. Myoclonic seizures were seen in
both 2000 and 4000 ppm treated groups with greater frequency at the higher
concentration.
12-38
-------
Convulsion threshold after intraperitoneal injection of Bemegride was
decreased significantly by preexposure to 2000 ppm toluene for 8 hours/day in
6 Sprague-Dawley male rats. The change was noted after 1 week of exposure. The
convulsion threshold continued to decrease for 6 weeks of exposure. After
8 weeks of exposure the difference from the controls was not significant,
although the convulsion threshold remained lower. The data suggest that toluene
renders the CNS more susceptible to induction of a convulsion state. Body
weights of these rats were lower than those of controls during the exposure
period, although differences were not significant (Takeuchi and Suzuki, 1975).
Andersson e_t al. (1980) reported an increase of dopamine and noradrenaline
in the median eminence after inhalation of 500 ppm and 1000 ppm toluene, respec-
tively, by male rats. The higher levels also produced increases of noradrenaline
turnover within the median eminence and the anterior periventricular and para-
ventricular hypothalamic nuclei. A significant increase of plasma levels of
follicle-stimulating hormone (FSH) and a non-significant elevation of prolactin
and corticosterone were also noted.
Although most studies, acute as well as chronic, indicate minor effects of
toluene at concentrations under 1000 ppm and most reviews (NRC, 1980; EPA, 1980;
NIOSH, 1973) have emphasized the negligible effects on the CNS at this level,
several recent studies indicate that lower level exposures may not be innocuous.
Horiguchi and Inoue (1977) found a decrement in performance during a simple task,
Gusev (1967) found lengthened motor chronaxies at 4 ppm, Colotla and Bautista
(1979) noted a decrement in operant behavior at concentrations of 574 ppm, and
Anderson e_t al. (1980) reported histochemical changes in the brain at 500 ppm.
In all of these studies, sensitive parameters of CNS activity were measured.
Higher concentrations tended to affect more complex tasks. Furthermore, the
studies of Andersson jet al. (1980) indicate that 500 ppm affects an area of the
12-39
-------
brain which regulates many vegetative, as well as reproductive, functions. These
findings indicate that effects of toluene on the CNS at levels below 1000 ppm
cannot be totally ignored.
12.4 EFFECTS ON OTHER ORGANS
12.4.1 Blood-Forming Organs
Myelotoxicity is an effect that has been attributed to toluene. Prior to
the early 1940's it was believed that toluene had the same effect as benzene;
however, in most of the earlier studies toluene was contaminated with benzene.
Since then there have been studies indicating a lack of myelotoxicity and several
which indicate a positive effect (Table 12-7). -
One of the first studies using toluene free of benzene which demonstrated
that it had no injurious effect on blood-forming organs was that of Von Oettingen
et al. (1942b) in rats and dogs. Exposure of rats to 200 to 5000 ppm toluene
contaminated with less than 0.01$ benzene for 5-6 weeks (7 hours/day,
5 days/week) did not affect blood-forming organs, as indicated by the absence of
anemia and changes in the bone marrow and spleen. Exposure to the higher
concentrations of 2500 and 5000 ppm did produce a daily temporary shift in the
blood picture, characterized by a decrease of lymphocytes and total white blood
count with a moderate increase of segmented cells Table 12-8). Exposure of dogs
to inhalation of 400 ppm toluene on five consecutive days for 7 hours daily
produced no appreciable changes in the blood picture with the exception of a
temporary lymphocytosis at the end of exposure (Von Oettinger e_t al., 1942b).
Exposure of dogs to inhalation of higher concentrations of toluene containing
less than 0.1$ benzene (7.5 mg/1 for 8 hours daily, 6 days weekly during 4 months
and then 10 mg/1 for the 2 remaining months) had no effect on the bone marrow
(Fabre .et al., 1955).
12-40
-------
Table 12-7. Myelotoxicity Studies in Animals
Species
Route
Dose
Effect
Reference
Rats
n=20/group
Inhalation
Rats n=15
Guinea pigs
n=15
Dogs n=15
Monkeys n=3
Rats n=90
male + female
Inhalation
Inhalation
ro
4=-
Rats
Dogs
Inhalation
200, 600, 2500,
5000 ppm 7 h/d x 5 d
x 5-6 wk
107 ppm continuous
exposure for 90 d
or 1085 ppm 8 h/d,
5 d/wk, for 6 wk
30, 100, 300 ppm
6 h/d x 5 d/wk x 24 mo
210, 180, 980 ppm
6 h/d x 5 d/wk
x 65 d
At highest doses: a
temporary decrease of
lymphocytes and total
white blood cell count;
no anemia; no effect on
bone marrow or spleen
No significant change in
leukocyte count, hemo-
globin, or hematocrit
No effect on any hemato-
logical parameter except
2 parameters in females:
at 100 or 300 ppm hernato-
crit was reduced, at
300 ppm mean corpuscular
hemoglobin concentration
was higher; no histo-
pathology on any organ
including spleen and bone
marrow
No effect on red blood
cell count, white blood
cell count, hematocrit,
hemoglobin, total and
differential white count,
SAP, SGPT, SCOT, or BUN;
no effect on bone marrow.
von Oettingen et al., 19l2b
Jenkins et al., 1970
CUT, 1980
Carpenter et al., 1976b
-------
Table 12-7. Myelotoxicity Studies in Animals (Cont'd)
Species
Route
Dose
Effect
Reference
Dogs
Dogs
Rats
Rats
Mice
Inhalation
Inhalation
Subcutaneous
Oral
Inhalation
s=
to
Donryu strain
rats n=6/group
Inhalation
400 ppm 7 h/d x 5 d
7.5 mg/1, 8 h/d x
6 d/wk x 4 mo, and
then 10 mg/1, 8 h/d
x 6 d/wk x 2 mo
1 cc/kg body weight
x 14 d
118, 354, 590 mg/kg/d
x 138 d
1, 10, 100, 1000 ppm
6 h/d x 20 d
200, 1000, 2000 ppm
99.9% pure toluene
for 32 wk
No change in blood picture;
temporary lymphocytosis
No effect on bone marrow
Normal leukocyte count,
spleen, and bone marrow
Normal bone marrow,
spleen, bone marrow
counts, blood count
Leukocytosis at all dose
levels; 100, 1000 ppm:
depressed red cell count;
10-1000 ppm: decreased
thrombocyte count;
1000 ppm: trerid toward
hypoplasia in bone marrow
Significant retarded weight
gain at 2 higher doses during
initial 4 wk; no significant
difference in hemoglobin
hematocrit and total plasma
protein; no significant in-
crease of RBC; significant
increase of leucocytes at
highest dose at first week
of exposure followed by
recovery; eosinophile counts
decreased rapidly in the
first 2-4 weeks and the
recovered; increase of
Momonsin1 s toxi-c granules.
von Oettingen et al., 1942b
Fabre et al., 1955
Gerarde, 1960
Wolf et at., 1956
Horiguchi and Inoue, 1977
Takeuchi, 1969
-------
Table 12-7. Myelotoxicity Studies in Animals (Cont'd)
(V)
I
4=-
Species
Route
Dose
Effect
Ref erence
Rat
Inhalation
420 rag/m3
Leukocytosis and chromo-
Dobrokhotov and
4 h/d x 4 mo some damage in bone marrow Enikeev, 1977
(cited in EPA, 1980)
Rat Subcutaneous 1 g/kg/d x 12 d 11.5$ chromosome damaged Lyaphalo, 1973
cells vs. 3-9$ in controls
Rat Dermal 10 g/kg body weight/d Impaired leukopoiesis Yushkevich and Malysheva,
1975
Abbreviations: n = number; h = hour; d = day; wk = week; mo = month; SAP = serum alkaline phosphatase;
SGPT = serum glutamic pyruvic transaminase; SCOT = serum glutamic oxalacetic transaminase; BUN = blood urea
ni trogen.
-------
Table 11-8. Weekly Blood Picture of Normal Rats and Rats Exposed to 600 and
2500 ppo of Toluene 7 Hours/Day, 5 Days/Week, for 5 Weeks
(von Oettingen et al., 1942b)
MORMAL
Weeks
Preexposure period:
First
Second
Exposure period:
First
Second
Third
Fourth
Fifth
2 Weeks After
Exposure
Number of Animals 1
5
15
20
_
20
20
20
20
20
20
20
20
20
9
9
1
•H
A.M.
P.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
Million red blood cells 1
7.0
6.2
w.
6.2
6.6
6.5
6.7
6.2
6.7
6.4
6.5
6.1
7.4
6.7
g/100 cc hemoglobin
12.0
11.3
__
12.0
11.8
10.7
11.5
10.9
12.8
11.2
11.5
10.1
13.3
12.4
Percent reticulocytes
3.6
4.0
__
6.5
3.6
3.9
4.8
4.2
4.4
4.7
6.6
6.2
4.7
4.6
Thousand white blood
cells
11.9
16.4
__
17.9
14.0
17.5
15.9
16.2
18.3
15.5
17.6
18.2
16.5
19.2
Percent mononuclear cells!
68
69
„
70
65
64
70
66
73
65
66
59
68
66
Percent segmented cells I
32
31
_
30
35
36
30
34
27
35
34
41
32
34
Thousand total mono-
nuclear
8.1
11.3
„
12.5
9.1
11.2
11.1
10.7
13.4
10.1
11.6
10.7
11.2
12.7
Thousand total segmented
cells
3.
5.
.»
5.
4.
6.
4.
5.
4.
5.
6.
7.
5.
6.
8
1
4
9
3
8
5
9
4
0
5
3
5
600 ppm
Preexposure period:
First
Second
Exposure period:
First
Second
Third
Fourth
Fifth
2 Weeks After
Exposure
Preexposure period:
First
Second
Exposure period:
First
Second
Third
Fourth
Fifth
2 Weeks After
Exposure
15
5
20
»
20
__
20
__
20
20
20
20
20
10
10
10
10
20
20
20
20
20
20
20
20
20
20
20
10
10
A.M.
P.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
A.M.
P.M.
6.8
—
_
—
__
__
_«
__
6.5
6.3
6.5
5.9
7.2
6.8
6.3
6.6
6.5
6.0
6.5
6.6
6.4
6.5
6.5
6.4
6.0
6.5
7.2
5.6
11.4
—
__
..
__
—
._
—
12.3
11.5
11.1
10.6
15.0
13.6
2500 P
12.3
12.1
11.6
10.4
11.5
10.9
11.5
11.2
11.8
11.0
10.5
10.8
14.4
11.7
3.0
4.6
-_
5.4
__
4.6
__
4.0
4.4
3.9
4.8
6.2
5.2
5.0
pm
4.0
4.2
6.6
7.7
4.6
5.2
4.8
4.2
5.5
6.1
5.3
5.3
4.5
4.9
13.1
~
__
-.
__
—
__
._
12.2
14.5
12.5
14.5
11.0
12.3
11.0
13.4
16.6
12.1
15.4
11.3
15.9
11.3
14.0
12.0
13.3
9.9
15.8
11.1
70
74
__
78
„.
82
__
75
71
66
71
65
75
68
77
73
67
51
70
55
69
56.
64
55
67
53
73
63
30
26
„
22
__
18
*—
25
29
34
29
35
25
32
23
27
33
49
30
45
31
44
36
45
33
47
27
37
9.2
--
__
-_
__
__
__
._
8.7
9.6
8.9
9.4
8.3
8.4
3.5
9.8
11.1
6.2
10.3
6.2
11.0
6.3
9.0
6.6
3.9
5.3
11.5
7.0
3.
—
_•
__
__
__
__
__
3.
4.
3.
5.
2.
3.
2.
3.
5.
5.
4.
5.
4.
5.
5.
5.
4.
4.
4.
4.
9
5
9
6
1
7
9
5
6
5
9
6
1
9
0
0
4
4
6
3
1
12-44
-------
Male Wistar rats administered a daily subcutaneous dose of 1.0 cc/kg body
weight for 14 days had a normal leucocyte count, thymus and spleen weight,
femoral marrow nucleated cell count, and femoral marrow nucleic acid content
(Gerarde, 1956).
Wolf ^t al. (1956) could find no effect on femoral bone marrow, spleen, bone
marrow counts, or hematological parameters in female Wistar rats orally dosed
with concentrations of 94.4$ pure toluene of up to 590 mg/kg/day for 24 weeks.
Neither did exposure of Fischer 344 rats for 24 months (6 hours/day,
5 days/week) to 30, 100, or 300 ppm 99.98$ pure toluene have any hematological
effects (Table 12-3). There were no changes in the bone marrow or spleen (CUT,
1980).
Speck and Moeschlin (1968) noted that subcutaneous injection of 300 mg/kg
or 700 mg/kg pure toluene administered daily to rabbits for 6 and 9 weeks,
respectively, had no myelotoxic effects. There were no changes in DNA-synthesis
of bone marrow cells as measured by incorporation of H-methylthymidine or in
peripheral blood elements (leucocytes, thrombocytes, reticulocytes, or erythro-
cytes).
In a study made by Braier (1973), subcutaneous injection of 862 mg/kg body
weight daily for 6 days produced a moderate depression of granulocytes during the
first 2 days of treatment. This was followed by a sharp rise in granulocytes by
the end of 6 days, a rise which was twice that of the pretreatment level. No
significant change was noted in the bone marrow. In contrast, subcutaneous
injection of benzene at the same dosage elicited a progressive decrease in
granulocyte count throughout the period of treatment.
59
The effects of toluene and benzene on the incorporation of Fe in erythro-
cytes were studied by Andrews e_t al. (1977). While benzene inhibited the incor-
cq
poration of Fe, toluene did not.
12-45
-------
The studies suggesting a myelotoxic effect include Horiguchi and Inoue
(1977) who exposed groups of 6 male mice to toluene vapor at concentrations of 1,
10, 100, and 1000 ppm for 6 hours daily over a period of 20 days and found that
the two highest doses decreased red cell count. Concentrations of 10 ppm and
above decreased thrombocyte count. All groups showed an increase in white cell
count midway in the study, followed by recovery except in the 100 ppm group.
Slight hypoplasia of the bone marrow was noted at the highest dose.
Taheuchi (1969) observed a transient increase in ceucocytes in 6 Donryu
strain rats exposed to 2000 ppm 99.9$ pure toluene containing less than 0.2 ppm
benzene in the course of 8 hour daily exposures for 32 workers as well as a
transient decrease of eosinophile counts upon exposure to 200, 100, or 2000 ppm
toluene under the same regimes (see Table 12-7). After 32 weeks of toluene
exposure all groups including an unexposed control group were subjected to 39
8-hour daily exposures to benzene prior to histopathological examination after
sacrifice. Adrenal weight to body weight was depressed significantly in all
groups which had been exposed to toluene. Histologically the zona glomerulosa of
the adrenal cortex of toluene exposed rats was thicker while the zxona
fasciculata and zona reticularis were reduced. The authors suggested that
toluene affected the hypothalama-pituitary-adrenal system. While that
hypothesis is tenable since the rats exposed to toluene differed from unexposed
controls, all grops exposed and unexposed to toluene were also exposed to
benzene, therefore, this conclusion can only be regarded as sensitive. An
alotract of a lates paper (Taheuchi et al*, 1972 cited in CA79:28056e), which was
not available for review, noted that exposure of male rats to toluene for 8 hours
daily for 4 weeks increased adrenal weight and eosinophil counts and decreased
corticosteroid concentration after 1 week.
12-46
-------
Topical application of 10 g/kg toluene to rats 4 hours daily for 4 months
had no effect on maturation of erythroblasts in the bone marrow, but an increase
of plasmic and lymphoid reticular cells in the marrow indicated an impairment of
leucopoiesis. A lower dosage of 1 g/kg toluene daily had no effect (Yushkevich
and Malysheva, 1975).
Chromosomal damage in the bone marrow and leucocytosis was noted in rats
that had been exposed to inhalation of 112 ppm of toluene, 4 hours daily, for
4 months. Recovery from leucocytosis occurred one month after termination of
exposure, but the chromosomal damage was unchanged. On the other hand,
inhalation of a combination of toluene and benzene produced chromosomal
aberrations, which were approximately equal to the sum of aberrations induced by
single administration of the solvents. Whereas benzene caused leukocytopenia,
the mixture caused leukocytosis (Dobrokhotov and Enikeev, 1977).
In the studies of Matsumoto e_t al., (1971) exposure of Donryu male rats to
inhalation of 2000 ppm toluene vapor 8 hours/day, 6 days/week for 43 weeks
decreased the ratios of thymus weight to body weight and spleen weight to body
weight.
Although the evidence tends to weigh more heavily toward the absence of a
myelotoxic effect from toluene exposure in animals, the suggestion made in NRC
(1980) that the positive findings may indicate subtle unrecognized hematopoietic
responses is sound. For example, the effect of toluene on hematocrit and mean
corpuscular hemoglobin concentration in female Fischer rats and not in male rats
is of interest in view of the observation of Hirokawa (1955) where there appears
to be a higher susceptibility of the female rabbit to benzene. In that study the
pattern of decrease of erythrocytes, hemoglobin content, while blood cells,
increase of mean corpuscular volume, decrease of mean corpuscular hemoglobin
concentration in the female was simulated in the estradiol propionate treated
orchidectomized male.
12-47
-------
There was no increase of erythrocyte fragility seen in 6 rats that inhaled
20,000 ppm "toluene concentrate" for 45 minutes (Carpenter et al., 1976b). A
slight increase in coagulation time was noted in rabbit blood by Fabre e_t al.
(1955) and in rats by von Oettigen e_t al. (1942b).
12.4.2 Cardiovascular Effects
Several animal studies have shown that massive doses cause a number of
electrocardiographic changes. In addition, a sensitization of the heart to low
oxygen levels was observed.
Inhalation of glue fumes containing toluene for 1 minute significantly
slowed sinoartrial heart rate of 8 ICR mice and slightly lengthened the P-R
interval. Subjecting the animals to 5 minutes of asphyxia after inhalation of
the glue fumes produced a 2:1 atrioventricular block in all animals within an
average of 42 seconds of asphyxia. In contrast after 24 5-minute periods of
asphyxia the sinoatrial heart rate rose the P-R internal did not lengthen, and
atrioventicular (AV) block did not occur in 12 mice (Taylor and Harris, 1970).
In acute inhalation of toluene atrial fibrillation, bradiarrhythmia, and
asystole, along with respiratory paralysis occurred. Injection subcutaneously
of 2 doses of 0.1 ml/100 g body weight daily for 6 weeks elicited repolarization
disorders, atrial fibrillation, and in some of the rats, ventricular extra-
systoles (Moravai e_t al., 1976).
Intravenous injection of 0.01 mgm/kgm epinephrine into dogs following
inhalation of toluene vapors (concentration did length of exposure varied, but
unspecified) elicited ventricular fibrillation (Chenoweth, 1946). This observa-
tion is of interest because the "sudden death" syndrome following "glue sniffing"
in humans might possibly be explained by an increased secretion of epinephrine
which could cause fibrillation of the heart as a result of the combined effect of
the two compounds.
12-48
-------
Intravenous injection of 0.05 mg/100 g body weight of toluene into rats
reduced arterial blood pressure; however, injection of the same dosage by the
intraperitoneal or subcutaneous route had no effect on blood pressure (Moravai
e_t al., 1976). No effect on blood pressure was seen in the chronic inhalation
studies of von Oettingen et al. (1942b) where dogs were exposed to inhalation of
200 to 600 ppm toluene several times weekly for several months. In this study
there was no effect observed on circulation, heart rate, venous pressure, spinal
pressure, respiratory rate, minute volume, or respiratory volume.
12.4.3 Gonadal Effects
Matsumoto et al. (1971) found that Donyru strain male rats exposed to
inhalation of 100 or 200 ppm toluene vapor 8 hours/day, 6 days/week for one year
produced no change in erythrocyte and leucocyte counts, and no change in seven
total protein or cholinesterase activity. However at the higher dose degenera-
tion of germinal cells of the testes was found in four of 12 animals while normal
germinal epithelium was found in controls. Testicular weight was lower than
controls at both dose levels. There was a trend toward a decrease of testicular
to body weight ratio.
12.5 Summary
The most pronounced effect of toluene in animal studies is on the central
nervous system. Acute exposure to high levels of toluene has been linked with
depression of the central nervous system. A level of approximately 1000 ppm
toluene vapor appears to have little or no effect on gross observations of this
parameter. While a dose related response of instability, incoordination and mild
narcosis was observed in rats exposed daily to toluene vapor at concentrations of
1250 and 1600 ppm. No effects was noted at 1100 ppm (Batchelor, 1927). Inhala-
tions of 1000 ppm toluene vapor for 4 hours did not increase rearing reactions
(standing on hind legs) in rats (Takeuchi and Hisanaga, 1977). Operant behavior
12-49
-------
(conditioned avoidance response) was unaffected at 1000 ppm of vapor in the
studies of Shigeta e_t al. (1978) and at 800 ppm in the studies of Krivanck and
Mullin (1978). Neither did inhalation of 1000 ppm for 6 hours/day, 5 days/week
for 13 weeks produce observable behavioral effects in rats in the pilot study for
the chornic CUT report (CUT, 1980). Smyth and Smyth (1928) noted that daily
inhalation of 1250 ppm for 4 hours each day for 18 days produced narcosis in
guinea pigs while no effect was noted at 1000 ppm during a longer period of
exposure. Fabre e_t al. (1955) noted that exposure to 2000 ppm toluene for
8 hours daily 6 days weekly for 4 months produced only slight nasal and ocular
irritation after a transient initial hyperactivity in one of two dogs. No
behavioral effects were found in rats and dogs after inhalation of 980 ppm
"toluene concentrate" (450 ppm toluene) for 6 hours daily for 13 weeks.
However, use of more sensitive Imethods of detection have revealed an effect
in single behavioral parameters and the central nervous system at lower levels.
EEC changes were seen in rats after inhalation of 1000 ppm (Fodov et al., 11973;
Takeuchi and Hisanaga, 1977). A deficit was noted in unconditioned reflexes and
simple behavior at 800 ppm for 4 hours in rats (Krivanck and Mullin, 1978), in
multiple response schedule at 574 ppm in rats (Colotla and Bautista, 1979); in
wheel-turning in rats at 1 ppm (Houguchi and Inoue, 1977). Neuromodulator
content in the hypothealamus was affected at 500 ppm (Anderson et al., 1980).
Early studies suggested a myelotoxic effect by toluene. However, several
studies done since the early 1940's using toluene of greater purity have
indicated an absence of injurious effect on blood-forming organs by toluene in
rats and dogs (von Oettingen et al., 11942; Gerarde, 1959; Wolfe et al., 1956;
Fabre et al., 1955; Jenkins et al., 1970; Carpenter et al., 1976b, CUT, 1980).
Nonetheless there is no unanimity on this point. Leukocytosis impaired
leukoporesis and chromosomal damage in the bone marrow have been observed in some
12-50
-------
studies (Houguchi and Inoue, 1977; Dohokhotor and Enichiev, 1977; Lyapkalo,
1973; Yushkench and Malsheva, 1975).
Inhalation of concentrations of up to 1085 ppm toluene for 6 weeks or
300 ppm for 24 months, and ingestion of 590 mg toluene/kg body weight for
61 months produced no liver damage (Svirbely £t al., 1944; Carpenter e_t al.,
1976b; Jenkins et al., 1970; CUT, 1980; Wolf etal., 1956). Exceptions were the
studies of von Oettingen e_t al. (1942) where inhalation of 600 ppm toluene caused
increase of weight and volume in the liver of rats; the studies of Fabre e_t al.
(1955) in dogs were hemorrhagic livers were found at Ungavny ^t al., 1976 where
0.05 or 0.1 ml/100 g toluene injected intraperrtoneally produced histological
changes in the liver.
However, in a more recent study by Ungvary ^t al. (1980) where male CFY rats
were exposed to daily inhalation of 265 ppm or 929 ppm analytical grade toluene
and female rats were exposed to lower doses only five times a week up to 6 months
no abnormal histological changes were found in the liver although growth was
inhibited at the higher concentration in males and at the lower dose in females.
Subchronic exposure to inhalation of toluene had no specific hepatoxic effect,
although signs of adaption compensation were observed.
Renal changes consisting of casts in collecting tubules of rats were
observed in the studies of von Oettingen e_t al. (1942b) after exposure to inhala-
tion of 600 ppm. Hyperemic renal glomeruli and albuminuria were seen in 2 dogs
after inhalation of toluene vapors at concentrations of 2000 ppm followed by
2660 ppm for 4 and 2 months, respectively (Fabre e_t al., 1955). Slight renal
degeneration was observed in guinea pigs (Smyth and Smyth, 1928; Sessa, 1948).
No renal damage was found after repeated inhalation of 1085 ppm toluene for
6 weeks in rats, guinea pigs, dogs, or monkeys, up to 300 ppm for 24 months in
rats or ingestion of 590 mg toluene/kg body weight for 6 months in rats (Jenkins
etal., 1970; CUT, 1980; Wolf .etal., 1956).
12-51
-------
Irritation effects were noted in the respiratory tract in dogs, guinea pigs,
and rats (Browning, 1965; Gerarde, 1960; Fabre et al., 1955; von Oettingen
et al., 1942b; Smyth and Smyth, 1928; Sessa, 1948). Sensitization of the heart
after inhalation of toluene was observed in mice, rats, and dogs (Taylor and
Harris, 1970; Nowai ejb al., 1976; Chenoweth, 1946).
The acute oral toxicity (LD50) of toluene is in the range of 6.0 to 7.5 g/kg
in rats (Kimura et al., 1971; Smyth et al., 1976b; Withey and Hall, 1975; Wolf
e_t al., 1956). Exposure to toluene by the dermal route revealed in LD50 of
14.1 mg/kg in the rabbit (Smyth ej; al., 1969). Slight to moderate irritation of
the rabbit and guinea pig skin was observed after acute and subacute application
of toluene (Kronen e_t al., 1979; Wolf et al., 1956) while application to the
rabbit cornea caused slight to moderate irritation (Wolf et al., 1956; Smyth
ejb al., 1965; Carpenter and Smyth, 1946).
The LC50 for mice is in the range of 5500 to 7000 ppm of vapor for an
exposure period of 6 to 7 hours (Svirbely e_t aj.., 1943; Bonnet e_t jil., 1979). An
LC50 of 8800 ppm of "toluene concentrate" for 4 hours (4,038 ppm toluene) was
observed in rats (Carpenter e_t al., 1976b). In guinea pigs exposure inhalation
to 4000 ppm for 4 hours caused death in 2 of 3 animals (Smyth and Smyth, 1928).
Subchronic treatment of rats (von Oettingen e_t al., 1942b) and rats, guinea
pigs, dogs, and monkeys (Jenkins et al., 1970; Smyth and Smyth, 1928) reveal that
exposure to inhalation levels of 200 and 1085 ppm, respectively, do not hae a
deleterious effect on hematology and organ pathology with the exception of the
study of Hougenchi and Inonu (1977) in mice which showed changes in blood
elements at levels as low as 10 ppm. Toluene levels of 590 mg/kg/day
administered orally for six months were tolerated by rats with no adverse effects
(Wolf et al., 1956).
12-52
-------
The only chronic study was the study performed for CUT (1980) in rats
exposed for 24 months to inhalation of toluene at levels up to 300 ppm. No
effect on hematology, clinical chemistry, body weight or histopathology were
noted except for two hematologic parameters in the females. Females exposed to
100 or 300 ppm showed reduced hematocrit levels and mean corpuscular hemoglobin
concentration was increased at 300 ppm concentrations of toluene.
12-53
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13. PHARMACOKINETIC CONSIDERATIONS IN HUMANS AND IN ANIMALS
13.1 ROUTES OF EXPOSURE AND ABSORPTION
For humans, the most common routes of exposure to toluene are through the
respiratory tract and the skin. Toluene is readily absorbed through the respira-
tory tract. In experimental exposures of humans to toluene conducted by Astrand
and coworkers (1972; also reported in Astrand, 1975), toluene was detected in
arterial blood during the first 10 seconds of exposure. Toluene was supplied in
the inspired air at 100 or 200 ppm through a breathing valve and mouthpiece.
Unless otherwise specified, in the experiments reported here, human subjects
breathed toluene vapor from some type of respiratory apparatus. In resting
subjects, the concentration of toluene in arterial blood increased rapidly
during the first 10 minutes of exposure and then began to level off, approaching
an apparent steady state by 30 minutes. The concentration of toluene in alveolar
air (i.e., an air sample taken at the end of a normal expiration) increased
concomitantly.
Alveolar and arterial concentrations of toluene were proportional to the
concentration in inspired air. At the end of 30 minutes of exposure to 100 or
200 ppm (0.375 or 0.750 mg/1) toluene, the concentration of toluene in alveolar
air (mg/1) was lQ% of that in inspired air (mg/1), while the concentration in
arterial blood (mg/kg) was 270$ of that in inspired air (mg/1) (Astrand et al.,
1972; Astrand, 1975). The ratio between arterial blood and alveolar air concen-
trations was 15, which is similar to the in vitro blood/air partition coeffi-
cients (at 37°C) of 14.6, 15.6, and 15.6 reported for human blood by Sato et al.
(1974b), Sherwood (1976), and Sato and Nakajiraa (1979a), respectively.
According to Veulemans and Masshelein (1978a), subjects' lung clearances
(i.e., the virtual volume of inspired air from which all available toluene is
absorbed per unit time) decreased during exposure at rest, reaching an apparent
13-1
-------
steady state 9 to 13 minutes from the beginning of exposure. Lung clearance =
C. - C
V where C. is the concentration of toluene in inspired air (mg/1), C
Q 1 6
is IBie concentration of toluene in expired air (mg/1), and V is the respiratory
e
minute volume (I/minute).
Nomiyama and Nomiyama (197*13) measured the pulmonary retention
C. - C
( e 100) of volunteers exposed to about 115 ppm toluene for 4 hours. The
C1
subjects may have been fairly sedentary because the authors did not mention
exercise. Retention at the end of 1 hour was approximately 52$ and decreased to
37$ at the end of 2 hours, remaining constant at that level for the remaining
2 hours. These results suggest a slower approach to steady-state concentrations
in expired or alveolar air than was indicated by the time courses obtained for
lung clearance by Veulemans and Masschelein (1978a) or for alveolar air concen-
trations by Astrand ^t _al. (1972). The results also suggest a lower percentage
of uptake or retention than was reported by Veulemans and Masshelein O978a) and
others as will be presented subsequently. The reasons for these discrepancies
are unclear.
Exercise affected the absorption of toluene through the respiratory tract.
In the experiments of Astrand and coworkers (Astrand et al., 1972; Astrand,
1975), exercise greatly increased the concentrations of toluene in arterial
blood and alveolar air of the subjects during exposure, and these concentrations
did not level off as soon in exercising subjects as in resting subjects. The
concentrations of toluene in arterial blood and alveolar air were approximately
the same at 30 minutes of exposure to 200 ppm during rest as at 30 minutes of
exposure to 100 ppm during light (50 watts) exercise. At 30 minutes exposure to
100 or 200 ppm (0.375 or 0.750 mg/1) toluene, the concentrations in milligrams
per liter expressed relative to the concentration in inspired air (mg/1) were 33$
for alveolar air and 620$ for arterial blood at exercise of 50 watts, and 47$ for
13-2
-------
alveolar air and 725? for arterial blood at exercise of 150 watts. The ratio of
arterial to alveolar concentration remained about the same as at rest. Thus,
alveolar concentrations appeared to reflect arterial concentrations during ex-
posure to 100 to 200 ppm toluene at rest and various intensities of exercise.
The inhalation of 4$ C0? by resting subjects during exposure to 100 ppm
toluene increased their alveolar ventilation (I/minute) and the concentrations
of toluene in their arterial blood and alveolar air (Astrand e_t _al., 1972). The
increased toluene concentration in blood and alveolar air were similar to those
obtained with a corresponding increase in alveolar ventilation during exercise.
Because exercise increased both alveolar ventilation and heart rate while CO-
increased only alveolar ventilation, the effect of exercise on toluene absorp-
tion appears to be due to increased alveolar (or pulmonary) ventilation.
In the experiments of Veulemans and Masshelein (1978a), the "steady state"
lung clearances of 6 different subjects during exposure to 50 ppm toluene at rest
and at workloads of 25 and 50 watts on a bicycle ergometer correlated well
(r = 0.96) with their respiratory minute volumes. Lung clearance was deter-
mined from the regression line to be equal to 0.47 V . The uptake rate in
milligrams per minute, which equals lung clearance times the inhaled concentra-
tion, therefore was equal to 0.47 V C. (where C. is expressed in mg/1) and total
6 i 1
uptake in milligrams equaled 47% of the total amount inhaled. Lung clearances
and respiratory minute volumes doubled with an exercise intensity of 25 watts and
tripled with an exercise intensity of 50 watts over the corresponding values at
rest (Veulemans and Masschelein, 1978a).
Carlsson and Lindqvist (1977) found that the uptake of toluene by 7 male
subjects exposed to 100 ppm for 30 minutes (0.375 mg/1) during rest or various
levels of exercise (50, 100, and 150 watts on a bicycle ergometer) correlated
13-3
-------
o
inversely (r = 0.72) with the alveolar concentration determined at the end of
30 minutes exposure, as described by the following equation:
< n _n fi^ alveolar concentration (mg/1) x 100 + 72.9
» uptake = -u.oj inspired concentration (mg/1)
This relationship is logical and applies to other solvents as well (Astrand,
1975; Ovrum et al., 1978). Percent uptake was determined on the basis of the
total amount of toluene inhaled and exhaled during the entire exposure period,
i.e., the expired air was collected continuously throughout exposure, and thus
was a mean value. The uptake ranged from about 47 to 67$ at rest and from about
36 to 57$ at an exercise level of 150 watts. This group of men comprised 3 thin,
one slightly overweight, and 3 obese subjects (Carlsson and Lindqvist, 1977).
Ovrum and coworkers (1978), monitoring 4 workers exposed to toluene in a
printing plant, found good agreement between the value for percent uptake deter-
mined directly from the total amounts of toluene inspired and expired during a
sampling period and the value determined indirectly from the instantaneous con-
centrations in alveolar and inspired air, using the equation given in the pre-
ceeding paragraph. Percent uptake determined by the direct method was 47$ and by
the indirect method was 51$. The total uptake of toluene that would occur during
exposure to 80 ppm (0.3 mg/1) for an 8-hour work day was calculated using the
mean value for pulmonary ventilation of 16 1/min measured for these 4 workers and
a percent uptake of 50. The total uptake amounted to approximately 1150 mg
(Ovrum jet al., 1978).
The percent uptake values determined by Carlsson and Lindqvist (1977) and by
Ovrum j^tjal. (1978) are in reasonable agreement with those previously reported in
abstracts from the foreign literature: 54$ average uptake during 5 hours' expo-
sure to 271 to 1177 ug/1 (Srbova and Teisinger, 1952) and 72$ initial retention
decreasing to 57$ retention towards the end of 8 hours' exposure to 100 to
800 yg/1 (Piotrowski, 1967).
13-4
-------
Another factor, in addition to exercise, that has been reported to affect
the absorption of toluene through the respiratory tract is the amount of adipose
tissue in the body. Carlsson and Lindqvist (1977) found that mean alveolar air
concentrations were slightly higher in 3 thin men than in 3 obese men at the end
of 30 minutes of exposure to 100 ppm (0.375 mg/1) toluene during rest or exer-
cise. The ranges, however, overlapped. Conversely, the total uptake of toluene
during 30 minutes of exposure (determined as previously described) was lower for
the thin subjects than for the obese ones (Table 13-D. The thin subjects had a
mean adipose tissue content of 6 kg and the obese ones had a mean adipose tissue
content of 44 kg. It appears, from Figure 6 in the Carlsson and Lindqvist (1977)
paper, that the obese men inspired a greater total quantity of toluene than did
the thin men. Because the concentrations of toluene in the inspired air were the
same for both thin and obese subjects, pulmonary ventilation must have been
greater in the obese ones. Thus the differences in uptake between the thin and
obese men may have been at least partially due to greater ventilation (respira-
tory minute volume) in the obese subjects rather than to their adipose tissue per
se. Veulemans and Masschelein (1978a) reported finding no correlation between a
subject's content of adipose tissue and uptake of toluene during exposures to 50
to 150 ppm toluene lasting about 4 hours. Astrand and coworkers (1972) stated
that they found no systematic differences between male subjects (N = 11, adipose
tissue 5.7 + 1.5 kg, mean +_ S.D.) and female subjects (N = 4, adipose tissue
13.3 kg, mean; 9.6-20.2 kg, range) in alveolar air and arterial blood concentra-
tions of toluene.
Dahlmann and coworkers (1968a, 1968b) investigated the absorption of
toluene contained in cigarette smoke through the mouths and respiratory tracts of
volunteers. The uptake of toluene from smoke that stayed in the subject's mouth
for 2 seconds or less and was not inhaled was 29$; uptake when the smoke was
13-5
-------
Table 13-1. Uptake of Toluene in Thin and Obese Men During Exposure to a Toluene
Concentration of 375 mg/m^ (100 ppm)a
Number of
Subjects
Adipose
Tissue
(kg)
Rest
Uptake
50 W
(mg)
Exercise
100 W
150 W
Thin (N = 3)
Mean
Range
6.0
1.4-10.7
61
55-69
148
133-158
193
168-211
228
181-271
Slightly overweight
(N = 1) 22.8 71 179 246 299
Obese (N = 3)
Mean 44.0 84 198 258 319
Range 35.1-49.0 72-73 183-206 237-275 258-358
The subjects were exposed during one 30-minute period of rest and three
consecutive 30-minute periods of exercise in order of increasing intensity. A
20-minute pause without exposure occurred between rest and exercise. Expired air
was collected continuously during exposure. (Adapted from Carlsson and
Lindqvist, 1977)
13-6
-------
inhaled into the lungs was 93?• It is unclear whether each subject was exposed
to a single puff of smoke, the smoke from 1 cigarette (8 puffs), or the smoke
from 2 cigarettes.
During inhalation exposure of resting subjects, the concentration of
toluene in peripheral venous blood (from the cubital vein of the arm) attained
apparent steady state more slowly than did lung clearance or concentrations in
alveolar air or arterial blood and was more variable among subjects than were the
above mentioned values (Veulemans and Masshelein, 1978a; 1978b; Astrand et al.,
1972; Sato and Nakajima, 1978). Peripheral venous concentrations appeared to
level off during the second or third hour of exposure. Von Oettingen (1942a,
19^2b) had observed that toluene concentrations in subjects' peripheral venous
blood at the end of 8 hours of exposure were roughly proportional to the concen-
trations of toluene (200 to 800 ppm) in the atmosphere of the exposure chamber.
Veulemans and Masshelein (1978b) reported that the steady-state concentrations
of toluene in peripheral venous blood were correlated with the rate of uptake at
different inspired concentrations (50, 100, and 150 ppm) (r = 0.73) and at
o
different levels of rest and exercise (r = 0.74). In both instances, the
relationship between peripheral venous concentrations and uptake rate was:
venous concentration (mg/1) = 0.3 minute/1 x uptake rate (mg/minute).
The concentration of toluene in peripheral venous blood of exercising subjects
increased more rapidly and appeared to reach steady-state values sooner than in
resting subjects (Astrand ^t _al., 1972; Veulemans and Masshelein, 1978b).
Absorption through the respiratory tract has been less extensively studied
in experimental animals than in humans. The initial uptake of a relatively low
concentration of toluene was found to be approximately 90? in dogs inhaling
toluene (Egle and Gochberg, 1976). Varying the ventilatory rate from 5 to
40 inhalations per minute, the tidal volume from 100 to 250 ml, or the concentra
13-7
-------
tion of toluene from 0.37 to 0.82 yg/1 (approximately 100 to 220 ppm) had no
significant effect on the animals' initial respiratory uptake. Toluene was
readily absorbed from the upper as well as from the lower respiratory tract. The
dogs were anesthetized with sodium pentobarbital for these experiments and
breathed toluene from a recording respirometer for 1 to 2 minutes. The percent
uptake was calculated from the total amounts of toluene inhaled and exhaled
during the 1 to 2 minute exposure.
Von Oettingen and coworkers (1942b) found that the concentration of toluene
in the peripheral venous blood of dogs at the end of 8 hours of exposure was
proportional to the concentration of toluene (200, 400, or 600 ppm) in the air of
the exposure chamber. As previously described, similar observations had been
made wi th humans.
Mice exposed singly to an extremely high initial concentration of raethyl-
14
C-toluene in a closed chamber for 10 minutes retained about 60$ of the readio-
activity when removed from the chamber at the end of the exposure (Bergman,
1979). This value is a rought approximation of absorption because some of the
toluene may have been adsorbed to the animals' fur. A substantial portion of the
retained dose appears to have been absorbed, however, as shown by its subsequent
excretion in the urine (Section 13.4). The initial concentration of toluene in
the chamber (10 ul evaporated in a volume of about 30 ml, or about 71,000 ppm)
would have been above the saturation concentration even if the temperature had
been as high as 30°C (saturation concentration = 48,900 ppm at 30°C)
(Verschueren, 1977). Bergman (1979) noted that exposure to toluene under these
conditions markedly reduced the respiratory rate of the mice and attributed this
reduction to irritation. It seems more likely that the decreased respiratory
rate was due to narcosis.
Absorption of toluene also occurs through the skin. Dutkiewicz and Tyras
(1968a, 1968b), in experiments with humans, measured the absorption of liquid
13-8
-------
toluene into the skin of the forearm and found the rate of absorption to be 14 to
2
23 mg/cm /hour. This rate was calculated from the difference between the amount
of toluene introduced under a watch glass affixed to the skin and the -amount
remaining on the skin at the end of 10 to 15 minutes. Absorption of toluene from
2
aqueous solutions during immersion of both hands was 160 to 600 ug/cm /hour and
was directly proportional to the initial concentration of toluene (180 to
600 mg/1). From these results, Dutkiewicz and Tyras (1968a, 1968b) calculated
that the absorption of toluene through the skin of both hands during contact with
a saturated aqueous solution of toluene for 1 hour could be in the same range as
absorption through the respiratory tract during 8 hours of exposure to 26.5 ppm
(0.1 mg/1) toluene.
Sato and Nakajima (1978) found, however, that the maximum toluene concen-
tration (170 ug/1) in blood of subjects who immersed one hand in liquid toluene
for 30 minutes was only 22$ of the maximum concentration (790 yg/1) in blood of
subjects who inhaled 100 ppm toluene vapor for 2 hours. Blood was collected from
the cubital vein of the (unexposed) arm at invervals during and after exposure.
Sato and Nakajima (1978) suggested that some of the toluene that penetrates the
stratum corneum may, rather than entering the systemic circulation, be subse-
quently given off into the air. Toluene does appear to pass from the skin into
the bloodstream relatively slowly after penetrating the skin. Guillemin et al.
(1974) reported that the elimination of toluene in alveolar air sometimes
increased during the first 20 minutes after the termination of exposure of both
hands to liquid toluene and Sato and Nakajima (1978) noted that the maximum
levels of toluene in venous blood were maintained for about 15 minutes after the
end of exposure.
Absorption of toluene vapor through the skin does not appear to result in a
significant contribution to the body burden of toluene as compared to absorption
13-9
-------
through the respiratory tract. In experiments conducted by Riihimaki and Pfaffli
(1978), volunteers wearing light, loose-fitting clothing and respiratory protec-
tion were exposed to 600 ppm toluene for 3.5 hours. The subjects remained at
rest except for three exercise periods, each lasting for 10 minutes, which
occurred at 0.5, 1.5, and 2.5 hours of exposure.. The exercise was sufficient to
stimulate perspiration and raise the skin temperature slightly, conditions which
are thought to enhance percutaneous absorption. The concentration of toluene in
peripheral venous blood, measured at the end of 1, 2, and 3 hours of exposure,
was constant at approximately 100 ug/1.
Riihimaki and Pfaffli (1978) compared total uptake through the skin (cal-
culated from the amount of toluene exhaled assuming that 16$ of absorbed toluene
is exhaled) with theoretical uptake through the respiratory tract (assuming
pulmonary ventilation of 10 I/minute and retention of 60$) at the same (600 ppm)
level of exposure. They estimated that uptake through the skin was approximately
1$ of the theoretical uptake through the respiratory system.
In similar experiments conducted by Piotrowoski (1967, reviewed in NIOSH,
1973), subjects exposed dermally to 1600 mg/nr (427 ppm) toluene for 8 hours had
no increase in urinary excretion of a metabolite (benzoic acid) of toluene.
Based on this result, Piotrowoski (1967) concluded that absorption of toluene
through the skin would not exceed 5% of absorption through the respiratory tract
under the same conditions.
The absorption of toluene from the gastrointestinal tract appears to occur
more slowly than through the respiratory tract, but to be fairly complete, based
on experiments with animals. The concentration of radioactivity in the blood of
adult male rats reached a maximum 2 hours after gastric intubation of 100 u
14- H-toluene in 400 ul peanut oil (Pyykko ^t al., 1977). The oil may have
retarded absorption. Based on the percentages of the dose excreted unchanged in
the expired air and as hippuric acid in the urine of rabbits, toluene appears to
13-10
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be completely absorbed from the gastrointestinal tract (El Masri e_t al., 1956;
Smith jet al., 1954).
13.2 DISTRIBUTION
Toluene is highly soluble in lipid and sparingly soluble in water, as
indicated by the partition coefficients in Table 13-2. Judging from the
fluid/air partition coefficients for water, plasma, and blood, much of the
toluene in blood may be associated with the lipid and lipoprotein components,
including the cellular elements. The tissue/blood partition coefficients for
fatty tissues were very high (113 for adipose tissue and 35 for bone marrow); for
other tissues, they ranged from about 1 to 3.
Little is known about the tissue distribution of toluene in humans. During
inhalation exposure to 50 to 200 ppm toluene, the slow approach to steady-state
of peripheral venous concentrations as compared to arterial concentrations
(described under absorption) indicates that equilibration with the tissues may
take at least 2 to 3 hours. Concentrations in peripheral venous blood do not,
however, reflect the discharge of toluene to the tissues as fully as would
concentrations in central venous blood. A teenage boy who died from sniffing
glue had the following levels of toluene in his tissues: heart blood, 11 mg/kg;
liver, 47 mg/kg; brain, 44 mg/kg; and kidney, 39 mg/kg (Winek e_t _aL. 1968; also
reported in Winek and Collum, 1971).
Several laboratories have investigated the tissue distribution of toluene
and its metabolites in animals exposed by inhalation to relatively high concen-
trations of toluene. The concentrations of toluene in liver, brain, and blood of
mice exposed to 15 mg/1 (3950 ppm) toluene for 3 hours in a dynamic exposure
chamber rose continuously throughout the exposure period, as shown previously in
Figure 12-1. Concentrations of toluene reached 625 mg/kg in liver, 420 mg/kg in
brain, and 200 rag/kg in blood at the end of exposure (Peterson and Bruckner,
13--11
-------
Table 13-2. Partition Coefficients for Toluene at 37°C
Partition Coefficient
Reference
I. Fluid/Air or Material/Air
Water
Oil, olive
Blood, Human
Fat, human, peritoneal
Oil, olive
Lard
Blood, human
Blood, human
Blood, rabbit
Plasma, rabbit
II. Tissuea/Blood (Rabbit)
Liver
Kidney
Brain
Lung
Heart
Muscle, femoral
Bone marow, red
Fat, retro peritoneal
2.23
492
15.6
1296
1380
1270
15.6
14.64
10.41
16.99
2.58
1.54
3.06
1.92
2.10
1.18
35.43
113.16
Sato and Nakajima, 1979a
Sherwood, 1976
Sato .et al. , 1974a, 1974b
Sato .et al. , 1974a, 1974b
20$ fat by volume.
13-12
-------
1978; Bruckner and Peterson, 198la). Exposure of mice to 40 mg/1 (10,600 ppm)
toluene for 10 minutes resulted in lower tissue and blood concentrations. Inter-
mittent exposure to 40 mg/1 in cycles of 5 minutes on/10 minutes off or
10 minutes on/20 minutes off for a total of 3 hours produced tissue and blood
levels approximately 3 times higher than those produced by the single 10 minute
exposure to 40 mg/1 and similar to those produced by the 3 hour exposure to
10 mg/1. The intermittent exposures were an attempt to simulate solvent abuse
(e.g., glue sniffing) by humans (Peterson and Bruckner, 1978; Bruckner and
Peterson, 198lb).
After adult male rats were exposed by inhalation to radioactively-labeled
toluene, the highest concentrations of radioactivity were found in their white
adipose tissue (Carlsson and Lindqvist, 1977; Pyykko et al., 1977). In the
experiments of Pyykko and coworkers (1977) the concentration of radioactivity
reached a maximum in all tissues but white adipose tissue within 15 to 30 minutes
after the end of 10 minutes' exposure to 4600 ppm 4- H-toluene. The concentra-
tion in white adipose tissue reached a maximum 1 hour after the end of exposure.
In the experiments of Carlsson and Lindqvist (1977), a similar increase in the
concentration of radioactivity in white adipose tissue occurred during the first
14
hour after cessation of exposure for 1 hour to 1.950 mg/1 (550 ppm) methyl- C-
toluene. No such increase occurred in other tissues.
Carlsson and Lindqvist (1977) found that, after white adipose tissue, the
next highest concentrations of radioactivity occurred in adrenals and kidneys,
followed by liver, cerebrum, and cerebellum. At the end of exposure white
adipose tissue contained a 6-fold higher concentration of radioactivity than did
cerebrum or cerebellum. Pyykko ^_t _al. (1977) reported that after white adipose
tissue, the next highest concentration of radioactivity was found in brown adi-
pose tissue, followed in order of decreasing concentrations by adrenal, stomach,
13-13
-------
liver and kidney, brain and other tissues, blood, and bone marrow. The loss of
radioactivity from adipose tissue and bone marrow appeared to occur more slowly
than the loss from other tissues (Pyykko e_t jl.f 1977). Radioactivity in the
tissues presumably represented toluene and its metabolites.
Bergman (1979), using three-step whole-body autoradiography, investigated
the distribution of toluene, its metabolites, and covalently bound reactive
14
intermediates in mice exposed to an extremely high concentration of methyl- C-
toluene. This work was briefly described in a previous report (Bergman, 1978).
The mice were exposed singly to a very high initial concentration of toluene for
10 minutes in a closed chamber, as described in Section 13.1, and sacrificed at
intervals thereafter. Low temperature autoradiography, performed at -80°C,
allowed the detection of both volatile radioactivity (representing toluene) and
non-volatile radioactivity (representing metabolites). In a second step, sec-
tions were dried and heated to remove volatile material before autoradiography,
thus permitting detection of non-volatile metabolites only. In the third step,
sections that had been dried and heated were then extracted to remove water-
soluble and lipid-soluble radioactivity, presumably leaving only the radio-
activity that was covalently bound to proteins and nucleic acids.
Low temperature autoradiography performed immediately after exposure
revealed high levels of radioactivity in adipose tissue, bone marrow, and spinal
nerves, with some radioactivity also present in the brain, spinal cord, liver,
and kidney (Bergman, 1979). Bergman reported that the adrenal did not contain
high concentrations of radioactivity but did not discuss whether radioactivity
was found in the stomach.
The only radioactivity visible in dried, heated sections appeared in the
liver, kidney, and blood (Bergman, 1979). This indicates that significant
amounts of metabolites had already been formed by the end of exposure and that
-------
the radioactivity in fat and nervous tissue was due to the parent compound.
Similarly, as early as 8 minutes after intraperitoneal injection of 290 ug
C- toluene/kg into mice, the majority of radioactivity in the kidney (78$) and
liver (6^%) and about half the radioactivity in blood (48$) was reported to
represent non-volatile metabolites, while most of the radioactivity in brain and
virtually all in the adipose tissue was volatile and thus represented toluene
itself (Koga, 1978). The methods used in Koga's study are unclear because the
text of the paper is in Japanese, with only the figures, tables, and summary in
English. Bergman (1979) reported that no radioactivity was detected in auto-
radiograms prepared from dried, heated, and extracted sections, indicating an
absence of covalent binding.
As had been observed in the studies of Pyykko e± ^1 . (1977) and Carlsson and
Lindqvist (1977), radioactivity disappeared from the tissues relatively quickly
after exposure was terminated. The distribution patterns observed in mice killed
more than 4 hours after exposure were the same on low temperature autoradiograms
as on dried, heated sections. Thus, the radioactivity remaining in the tissues
at this time represented non-volatile metabolites. At 8 hours after exposure
only the kidney and the intestinal contents had detectable radioactivity
(Bergman, 1979).
Oral administration of 4- H- toluene (100 ul toluene in UOO ul peanut oil by
intubation) to adult male rats produced a pattern of tissue distribution similar
to that produced by inhalation exposure (Pyykko ^_t al. , 1977). Distribution
appeared to be delayed, however, by absorption from the digestive tract. Maximum
tissue concentrations occurred 2 to 3 hours after administration for most
tissues and 5 hours after administration for adipose tissue.
In summary, toluene was preferentially accumulated in adipose tissue and
was retained in adipose tissue and bone marrow, which is reasonable on the basis
13-15
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of the high tissue/blood distribution coefficients of these tissues. Toluene and
its metabolites were found in relatively high concentrations in tissues active in
its metabolism and excretion (i.e., liver and kidney). Levels in brain relative
to those in other tissues were perhaps lower than would be expected on the basis
of. the tissue/blood distribution coefficients reported by Sato et _al. (1974a,
1974b). Tissue distribution was similar after inhalation and oral exposure.
13.3 METABOLISM
Toluene is thought to be metabolized in humans'and in animals by the path-
ways outlined in Figure 13-1. Some of the absorbed toluene is excreted unchanged
in the exhaled air, but the major portion is metabolized by side-chain oxidation
to benzoic acid, which is conjugated with glycine to form hippuric acid and then
excreted in the urine. Small amounts of benzoic acid may be conjugated with
glucuronic acid. Minor amounts of toluene undergo ring hydroxylation, probably
via arene oxide intermediates, to form o-cresol and p-cresol, which are excreted
in the urine as sulfate or glucuronide conjugates.
Humans exposed to toluene by inhalation exhaled about 16$ of the absorbed
toluene after exposure was terminated, according to Nomiyama and Nomiyama
(1974b) and Srbova and Teisinger (1952, 1953), or 4$, according to Veulemans and
Masshelein (1978a). Volunteers inhaling 50 to 150 ppm toluene for about 4 hours
during rest or exercise excreted 60 to 70$ of the absorbed dose as hippuric acid
in the urine during and after exposure (Veulemans and Masshelein, 1979). A
similar value was obtained when subjects were exposed to toluene (67 ppm) and
xylene (83 ppm) simultaneously for 3 hours; 68$ of the absorbed toluene was
excreted as urinary hippuric acid during and after exposure (Ogata ^t _al., 1970).
Srbova and Teisinger (1953) reported that although most of the benzoic acid in
the urine of subjects who inhaled 0.271 to 2.009 mg/1 toluene (72 to 532 ppm) was
excreted as hippuric acid, 10 to 20$ was excreted as a glucuronide conjugate.
13-16
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EXHALED
UNCHANGED
CH,
TOLUENE
CH2OH
CONHCH2COOH
HIPPURICACID
/GLYCINE
COOH
BENZYL ALCOHOL BENZOIC ACID
\
GLUCURONIC ACID
BENZOYL GLUCURONIDE
GLUCURONIDE AND
SULFATE CONJUGATES
Figure 13-1. Metabolism of Toluene in Humans and Animals
(Adapted from Laham, 1970)
13-17
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The excretion of hippuric acid in the urine was elevated within 30 minutes
of the initiation of inhalation exposure, indicating that the metabolism of
toluene is rapid (Nomiyama and Nomiyama, 1978; Ogata _et _al., 1970; Veulemans and
Masshelein, 1979). The maximum rate of hippuric acid formation from benzoic acid
was reported by Amsel and Levy (1969) to be about 190 umol/minute, and it appear-
ed to be limited by the availability of glycine (Amsel and Levy, 1969; Quick,
193D. Assuming retention of 60% of the inhaled concentration, Riihimaki (1979)
estimated that uptake of toluene may saturate the conjugation capacity at a
toluene concentration of 32 mmol/nr (780 ppm) during light work (pulmonary ven-
tilation of 10 1/rainute) or 11 mmol/nr (270 ppm) during heavy work (pulmonary
ventilation of 30 I/minute).
^-Cresol, a compound which is often not detected in normal urine, was
identified in the urine of workers exposed to 7 to 112 ppm toluene (Angerer,
1979 ; Pfaffli _et al., 1979). The concentration of jo-cresol in urine collected at
the end of exposure was directly proportional to the time-weighted average expo-
sure of the workers (Pfaffli et al.. 1979). Angerer (1979) estimated that
approximately 0.05$ of the retained toluene had been metabolized to _o-cresol.
£-Cresol may also have been a metabolite of toluene as its concentration was
higher in the urine of workers exposed to toluene than in the urine of unexposed
workers (Angerer, 1979). The difference, however, was not significant. Wiowode
et ^1. (1979) reported finding jn-cresol in addition to ^-cresol and £-cresol in
the urine of workers exposed to 280 ppm toluene. No jn-cresol was detected in the
urine of unexposed workers. No other studies of in vivo human or animal meta-
bolism or in vitro microsomal metabolism reviewed for this document have detected
jD-cresol as a metabolite of toluene.
The concentration of phenol has been reported to be slightly elevated in the
urine of exposed workers as compared to controls (Angerer, 1979; Szadkowski
13-18
-------
e_t^l., 1973). The origin of the increased phenol excretion was thought to be
the small amount of benzene present in industrially-used toluene (Angerer,
1979).
The metabolism of toluene has been more fully studied in animals than in
humans. The initial step in the metabolism of toluene to benzoic acid appears to
be side-chain hydroxylation of toluene to benzyl alcohol by the microsomal mixed-
function oxidase system. Toluene has been shown to produce a type I binding
spectrum with cytochrome PM50 from rats and hamsters, indicating that it is
probably a substrate for the mixed-function oxidase system (Canady e_t jd., 1974;
Al-Gailany £t _al., 1978). When incubated with rabbit hepatic raicrosomes, toluene
was metabolized primarily to benzyl alcohol (Daly e_t_al., 1968) and small amounts
of benzyl alcohol have been detected in the urine of rats given toluene orally
(Bakke and Sheline, 1970).
Additional evidence that toluene is metabolized by mixed-function oxidases
has been obtained by Ikeda and Ohtsuji (1971) who demonstrated that the induction
of hepatic mixed-function oxidases by pretreatment of adult female rats for
i> days with phenobarbital increased the metabolism of toluene. When given
1.18 mg toluene/kg body weight intraperitoneally, phenobarbital-pretreated
(induced) rats had greatly elevated urinary excretions of hippuric acid and
decreased concentrations of toluene in the blood compared to non-induced rats
given the same dose of toluene. Induced rats had high levels of benzoic acid in
the blood; non-induced rats had none (blood was obtained at decapitation).
The increased metabolism of toluene by induced rats appeared to reflect an
increase in side-chain hydroxylation of toluene because the activity of hepatic
side-chain hydroxylase, assayed in vitro with the model substrate £-nitro
toluene, was significantly increased per gram liver. The in vitro oxidation of
the resultant alcohol (p-nitrobenzyl alcohol) to the acid (p-nitrobenzoic acid)
13-19
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was not affected. The conjugation of benzole acid with glycine, measured in vivo
as the total amount of hippuric acid excreted after benzole acid administration,
was also unaffected (Ikeda and Ohtsuji, 1971).
It has been assumed (Ikeda and Ohtsuji, 1971; Nomiyama and Nomiyama, 1978;
NRC, 1980), by analogy with the metabolism of the model substrate p-nitrotoluene
(Gillette, 1959), that benzyl alcohol is metabolized to benzaldehyde by alcohol
dehydrogenase and that benzaldehyde in turn is oxidized to benzoic acid by
aldehyde dehydrogenase. These enzymes are both found in the soluble fraction
from liver. Benzaldehyde itself has not been detected in the urine or expired
air of animals given toluene orally (Smith ejt al., 1954; Bakke and Sheline,
1970). Metabolism of toluene probably occurs primarily in the liver, based on
the previously discussed tissue distribution of metabolites, the demonstrated
metabolism of toluene by liver microsomal preparations, and by analogy with the
metabolism of other xenobiotics.
Rabbits intubated with 300 mg toluene/kg body weight eliminated approxi-
mately 18$ of the dose in the expired air (Smith ^_t _§!., 1954) and, in another
study from the same laboratory, excreted about 74$ of the dose as hippuric acid
in the urine (El Masri ^t al., 1956). These results are similar to those
obtained with humans who inhaled toluene. None of the toluene appeared to be
converted to benzoyl glucuronide (Smith .et ^1., 1954), although about 14$ of an
oral dose of benzoic acid was excreted by rabbits as the glucuronide conjugate
(Bray et al., 1951).
Toluene metabolism appears to be rapid in animals, as shown by the
appearance of metabolites in the livers, kidneys, and blood of mice within
minutes of exposure to toluene (Bergman, 1979; Koga, 1978) (discussed in
Section 13.2) and by the increased urinary excretion of hippuric acid in rabbits
within 0.5 hour of the initiation of inhalation exposure (Nomiyama and Nomiyama,
13-20
-------
1978). As was previously mentioned for humans, the rate of conjugation of
benzoic acid with glycine may be limited, in animals, by the availability of
glycine. Administration of glycine to dogs exposed by inhalation to 200, 400, or
600 ppm toluene enhanced the rate of hippuric acid excretion (Von Oettingen,
19^2b). At the end of 8 hours of exposure to 600 ppm toluene, the concentrations
of toluene in peripheral venous blood from glycine-treated dogs were lower than
the concentrations in dogs that had not been treated with glycine. No such
difference was observed at the 2 lower exposure levels. This result suggests
that conjugation of benzoic acid with glycine may have limited metabolic elimina-
tion at the highest level of exposure. The level of exposure at which glycine
treatment produced a difference in venous blood levels of toluene is similar to
that (780 ppm) calculated by Riihimaki (1979) for saturation of the glycine
conjugation capacity of humans.
A minor pathway for the metabolism of toluene is ring hydroxylation by
mixed-function oxidases. Incubation of toluene with rat or rabbit liver micro-
somes resulted in the production of small amounts of ^-cresol and £-cresol (Daly
JsJi .§1• i 1968; Kaubisch et jl., 1972). The migration of deuterium when toluene
was labeled in the 1-position and a comparison of the rearrangement products of
arene oxides of toluene with the cresols obtained by microsomal metabolism of
toluene indicated that arene oxides are intermediates in the metabolism of
toluene to <>• and £-cresols (Daly et ^1., 1968; Kaubisch et jal., 1972).
Because phenols, including cresols, are eliminated in the urine as sulfate
conjugates, thereby increasing the excretion of organic sulfates and decreasing
the excretion of inorganic sulfate, investigators have used urinary sulfate
excretion after toluene administration as an indicator of cresol formation. Oral
doses of 350 mg toluene/kg body weight produced no increase in organic sulfate
excretion in rabbits (Smith et al., 1954). In rats, high doses (2.2 and
13-21
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4.3 g/kg) of toluene, administered orally, resulted in slight but significant
decreases in the ratio of inorganic sulfate to total sulfate in the urine, while
lower doses did not (Gerarde and Ahlstrom, 1966). This vrould appear to be a
relatively insensitive and nonspecific assay for metabolism to cresols.
Bakke and Sheline (1970) analyzed urinary phenols (after hydrolysis) from
male rats placed on purified diets containing neomycin, which reduced the urinary
levels of naturally occurring phenols. Toluene, administered orally in a dose of
100 mg/kg body weight, was metabolized to o-cresol (0.04 to 0.11$ of the dose)
and p-cresol (0.4-1.0$ of the dose).
Metabolism to cresols is of concern because of the putative arene oxide
intermediates, which are highly reactive and may bind to cellular macro-
molecules. Very little toluene is metabolized via this pathway, however, and the
studies already discussed in the distribution section indicate that binding of
toluene metabolites to proteins and nucleic acids does not occur to any signifi-
cant extent.
Van Doom and coworkers (1980) have reported detecting small amounts of a
mercapturic acid, tentatively identified as benzylmercapturic acid (N-acetyl-S-
benzyl-L-cysteine), in the urine of male rats treated with toluene. Approxi-
mately 0.4 to 0.7$ of a dose of 370 mg/kg toluene body weight, administered
intraperitoneally, was recovered as the mercapturic acid. The concentration of
glutathione in the liver was decreased slightly by administration of toluene.
Benzylmercapturic acid would arise from conjugation with glutathione of an
electrophilic product of side-chain oxidation of toluene.
The metabolism of toluene appears to result in its detoxification. The
length of the sleeping time produced by high doses of toluene (1.18 to 1.45 g/kg
intraperitoneally) was decreased in phenobarbital-induced female rats to 50$ or
less of the sleeping time of controls (Ikeda and Ohtsuji, 1971). Similar results
13-22
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were obtained with male mice (Koga and Ohmiya, 1968). Phenobarbital-induced
animals did not, however, have significantly different mortality rates than
controls when given high doses of toluene (Ikeda and Ohtsuji, 1971; Koga and
Ohmiya, 1968). Male mice given various inhibitors of drug metabolism (SKF 525A,
cyanamide, and pyrazole) 30 minutes before.the i.njection of toluene had sleeping
times that were significantly longer than those of control mice and had higher
mortality rates than did control mice (Koga and Ohmiya, 1978).
13.4 EXCRETION
In both humans and animals, toluene is rapidly excreted as the unchanged
compound in expired air and as a metabolite, hippuric acid, in the urine. Most
of the absorbed toluene is excreted within 12 hours of the end of exposure.
The concentrations of toluene in exhaled air and in arterial and venous
blood of human subjects declined very rapidly as soon as inhalation exposure was
terminated (Astrand ^t al., 1972; Carlsson and Lindqvist, 1977; Ovrum es_t al.,
1978; Sato ^t al., 1974b; Veulemans and Masshelein, 1978a, 1978b). Sato ^t al.
(1974b) reported that semilogarithmic plots of toluene concentrations in
alveolar air and in peripheral venous blood versus time after the end of exposure
suggested that desaturation occurred in three exponential phases: an initial
rapid phase, followed by an intermediate phase and then a slow phase. The data
were obtained from 3 male subjects who inhaled 100 ppm toluene for 2 hours (Sato
et al., 1974b; clarified in Sato and Nakajima, 1979b). The desaturation curves
were resolved graphically into three components and constants were determined by
the least squares method. The rate coefficients and corresponding half-lives
(t1/2) for the decay of toluene in peripheral venous blood were 0.355 min" (t1/2
= 1.95 minutes), 0.0197 min"1 (t1/2 = 35.2 minutes), and 0.00339 min"1 (t1/2 =
204 minutes). Rate coefficients and half lives for the decay of toluene in
13-23
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alveolar air were 0.437 min~1 (t1/2 = 1.59 minutes), 0.0262 rain"1 (t1/2
= 26.5 minutes), and 0.00313 rain" (t1/2 = 221 minutes).
Because the rate coefficient for the rapid phase was derived from only two
points (at 0 and 5 minutes), the second of which belonged with the intermediate
phase, Sato et al. (1974b) noted that the coefficient for the rapid phase
involved some error. The coefficient data of Sato ^t jil. (1974b) indicate that
the decay of toluene concentrations in peripheral venous blood was more gradual
than that in expired air. Similar conclusions have been reported by Astrand
et al. (1972), and Veulemans and Masshelein (1978b). Astrand et jd. (1972)
have reported that peripheral venous concentrations declined more gradually than
did arterial concentrations.
Veulemans and Masshelein (1978a) and Nomiyama and Nomiyama (1974b) found
the excretion curves for toluene in expired air to be adequately described as the
sum of 2 exponential terms rather than 3- Subjects for these studies were
exposed to 50, 100, or 150 ppm toluene for about 4 hours. The sampling regimens
differed from that of Sato £t al. (1974b), in that Veulemans and Masshelein
(1978a) did not begin monitoring expired air as soon after exposure ended and
Nomiyama and Nomiyama (1978b) sampled expired air infrequently during the period
used by Sato £t al. O974b) to determine the first 2 exponential phases. Rate
coefficients for the rapid and slow phases were calculated by Veulemans and
Masshelein (1978a) to be 0.340 min" and 0.00608 min" , respectively, using a
curve-fitting computer program. These rate coefficients corresponded to half-
lives of 2.04 and 114 minutes. Nomiyama and Nomiyama (1974b) reported rate
coefficients for the rapid phase of 5.10 h~ (t1/2 = 8.16 minutes) for men and
3.22 h~ (t1/2 = 12.9 minutes) for women; the rate constant for the slow phase
was 0.335 h~1 (t1/2 = 124 minutes) for both sexes.
13-24
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In the desaturation period, men and women expired 17.6? and 9«4/&, respec-
tively, of the total amount of toluene calculated to have been absorbed during
exposure (Nomiyama and Nomiyama, 1974b). These values are close to what had been
reported previously (i.e., 16/S) by Srbova and Teisinger (1952, 1953) in abstracts
from the foreign literature. Veulemans and Masshelein (1978a) estimated that
about 4$ of the toluene absorbed during exposure was subsequently excreted in the
expired air. Unlike the continuous exposures employed in the other pertinent
investigations, however, the exposure regimen employed by Veulemans and
Masshelein (1978a) was discontinuous (i.e., four 50-minute periods of exposure
separated by 10-minute intervals of nonexposure)."
According to Veulemans and Masschelein (1978a) a much greater variability
was observed for the excretion of toluene in expired air during the first 4 hours
after the end of exposure than had been observed for the related lung clearances
during exposure. This variability could partially be explained by differences in
respiratory minute volume during the post-exposure period; the percent of
absorbed toluene excreted in the expired air during the first 4 hours after
2
exposure correlated positively with respiratory minute volume (r = 0.71).
Another factor that appeared to affect excretion was the amount of body fat,
because there was a significant (p < 0.025) negative correlation between fat
content as measured by the index of Broca and the percent excretion in expired
2
air after exposure at rest (r = 0.213*0. This indicates that less of the
absorbed toluene would be excreted in the expired air of an obese person than in
the expired air of a thin person during the first 4 hours of desaturation. Addi-
tionally, subjects who had been exposed to toluene while exercising expired less
of the absorbed amount during the first 4 hours of desaturation than did subjects
who had been exposed while resting (Veulemans and Masshelein, 1978a).
13-25
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As previously described, 60 to 70% of the toluene absorbed by humans during
inhalation can be accounted for as hippuric acid in the urine (Veulemans and
Masshelein, 1979; Ogata _et al., 1970). The excretion rate of hippuric acid in
the urine of subjects inhaling 50, 100, or 150 ppm toluene increased during the
first 2 hours, leveling off at about the third hour after initiation of exposure
(Veulemans and Masshelein, 1979; Nomiyama and Nomiyama, 1978). Hippuric acid
excretion (mg/hour) declined fairly rapidly after cessation of about 4 hours'
exposure. Nomiyama and Nomiyama (1978), treating this decline as a monoexponen-
tial process, determined a half-life for hippuric acid in urine of 117 minutes
for men and 7** minutes for women. Veulemans and "Masshelein (1979) reported an
initial, fairly rapid decrease with a half-life between 2.0 and 2.3 hours,
followed by a more gradual return to baseline excretion levels by about 2U hours
after the start of exposure.
The excretion rate of hippuric acid, measured at the end of about 4 hours of
experimental exposure or 8 hours of occupational exposure, correlated reasonably
well with the uptake rates (Veulemans and Masshelein, 1979) or total uptake
(Wilczok and Bieniek, 1978) during exposure. At a given level of physical
activity and exposure concentration the intra and interindividual variability in
hippuric acid excretion was greater than that noted for uptake rates and was
attributed to the variable baseline excretion of this compound because it was not
explained by factors (body weight, body fat, cardiorespiratory parameters)
(Veulemans and Masshelein, 1979). Exercise during exposure increased the rate of
excretion of hippuric acid (Veulemans and Masshelein, 1979) in accordance with
the increase in uptake rate.
Hippuric acid is a normal constituent of urine derived from benzoic acid and
precursors of benzoic acid in the diet (Quick, 193O- Concentrations of hippuric
acid in the urine of 101 workers not exposed to toluene ranged from 0.052 to
13-26
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1.271 mg/ml (corrected to urine specific gravity of 1.024) and rates of excretion
of hippuric acid ranged from 18.47 to 23.00 mg/h for diuresis of greater than
30 ml/h (Wilczok and Bieniek, 1978). Others have also reported great variability
in the physiological concentrations of urinary hippuric acid (Ikeda and Ohtsuji,
1969; Imamura and Ikeda, 1973; Engstrom, 1976; Kira, 1977; Ogata and Sugihara,
1977; Angerer, 1979).
Volunteers exposed in a chamber to 200 ppm toluene for 3 hours followed by a
one hour break and an additional 4 hours of exposure excreted hippuric acid as
shown in Figure 13-2 (Ogata ^t _al., 1970). This exposure regimen was chosen to
simulate exposure in the workplace. After leveling off at about the end of
3 hours exposure, excretion increased again during the afternoon's exposure.
The rate of hippuric acid excretion remained elevated for about 2 hours after
exposure was terminated and then declined almost to baseline levels by 18 hours
after the end of exposure. The total quantity of hippuric acid excreted during
the period lasting 26 hours from the initiation of exposure was directly propor-
tional to the degree of exposure (ppm x time) up through the highest toluene
concentration of 200 ppm and could be used to calculate exposure with a fairly
high degree of accuracy. Less accurate for this purpose were excretion rates
during exposure (i.e., total hippuric acid excreted during exposure *• time) and
concentrations in urine, corrected for specific gravity. Concentrations of
hippuric acid in urine collected during the entire exposure period and corrected
to a specific gravity of 1.024 were 0.30 + 0.10, 2.55 ± 0.55, and 5.99 +
1.20 mg/ml (mean + standard deviation) for control, 100 ppm, and 200 ppm-exposed
subjects, respectively. Values for controls were lower and more uniform than
those reported by others, as described previously.
13-27
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I
NJ
CO
O>
< 8
DC
I-
I 6
I
Q 4
o
<
o
E 2-
D
o.
Q.
I 0-J
> -o
CONCENTRATION (mg/ml)
RATE (mg/minute)
T— '
0
2
i
4
i
6
i
8
10
12
i
14
16
i
18
20
22
24
26
r12
-10
-4
O "«
b I
21
-6 2
O H-
< D
O Z
cr S
? a:
.
a.
UJ
± O.
HOURS
Figure 13-2.
Urinary Concentrations and Excretion Rates of Hippuric Acid in
Volunteers Exposed to Toluene (Volunteers were exposed to 196 ppm
toluene for 3 hours in the morning and for 4 hours in the after-
noon with one hour's break in between. Points are means + SEM.)
(Ogata et al., 1970)
-------
Spot urine samples collected from workers after at least 3 hours of exposure
to toluene (and from nonexposed workers at the same time) have not given as good
a distinction between unexposed and exposed workers.
Imamura and Ikeda (1973) have pointed out that the upper fiduccial limit (P
= 0.10) of normal hippuric acid concentrations, whether or not corrected for
specific gravity, is so close to the lower fiducial limit of workers exposed to
100 ppm toluene (the threshold limit value) that such a measurement would not be
reliable in screening for overexposure. This conclusion was based on data
reported by Ikeda and Ohtsuji (1969). The correlations between concentrations of
toluene in workplace air and the concentration of hippuric acid in urine of
individual workers have been relatively poor (Veulemans _et al., 1979;
Szadkowski, 1973; Ogata ei_t^l., 1971). The correlation between exposure concen-
tration and excretion rate during exposure, although slightly better, was also
2
poor: r = 0.096 for the correlation with hippuric acid concentration (corrected
2
for specific gravity) and r = 0.116 for the correlation with rate of excretion
of hippuric acid (Veulemans ^t _aL., 1979). Some of the variance in excretion
rates was accounted for by differences in lung clearance, and, hence, uptake
among workers (Veulemans e_t _al., 1979).
in
Mice exposed to a very high initial concentration of methyl- C-toluene in a
closed chamber for 10 minutes, excreted about 10^ of the absorbed dose as vola-
tile material in the exhaled air and about 68$ as unidentified compounds in the
urine within 8 hours (Bergman, 1979). Details of exposure were discussed in
Section 13.1. In these experiments, volatile expired radioactivity (thought to
represent the parent compound) was collected continuously in a trapping device.
The total volatile radioactivity expired during each time interval was converted
to the mean percent dose excreted per minute during that interval and plotted at
the end of the interval. The resultant semilogarithmic plot of mean percent dose
13-29
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exhaled per minute versus time was a curve. Computerized non-linear regression
analysis of the data according to the method of least squares yielded 3 exponen-
tial components with rate coefficients of 0.0659, 0.0236, and 0.0044 min~
corresponding to apparent half-lives of 10.5, 29.4, and 158.7 minutes, respec-
tively.
The respiratory rates of the mice were, according to Bergman (1979),
"remarkably reduced" during exposure, and hence probably were reduced during at
least part of the post-exposure period. If respiratory minute volumes were also
decreased, this would, on the basis of the observations of Veulemans and
Massehelein (1978a), be expected to reduce the pulmonary excretion of toluene.
The results of Bergman (1979) may therefore not be relevant to exposures at lower
concentrations of toluene.
After inhalation exposure of rats or mice to toluene, the disappearance of
toluene and its metabolites from blood and from most tissues, including brain,
was rapid (Peterson and Bruckner, 1978; Carlsson and Lindqvist, Pyykko et al.,
1977; Bergman, 1979) as described in Section 13.2. The exceptions were white
adipose tissue, for which both accumulation and elimination were slow, and bone
marrow, for which elimination was very slow (Carlsson and Lindqvist, 1977 ; Pyykko
e± al., 1977). By 24 hours after exposure to radioactively-labeled toluene, the
concentration of radioactivity remaining in most tissues was less than 1% and
that remaining in adipose tissue was about 5% of the initial whole-body concen-
tration (Pyykko .et al., 1977).
Rabbits exposed to toluene vapor at 350 ppm for 100 minutes or 4500 ppm for
10 minutes had increased rates of urinary hippuric acid excretion which reached
maximum values 1.5 hours after exposure (Nomiyama and Nomiyama, 1978). Excre-
tion rates returned to baseline levels at 7 hours after the initiation of
13-30
-------
exposure to 350 ppm for 100 minutes and at about 3 hours after the initiation of
exposure to 4500 ppm for 10 minutes.
Dermal exposure of human subjects to toluene liquid or vapor resulted in the
appearance of toluene in the expired air (Guilleman e_t ^1., 1974; Riihimaki and
Pfaffli, 1978) as discussed in Section 13.1. The excretion of toluene in the
expired air of subjects exposed to 600 ppm toluene for 3 hours appeared to
consist of at least 2 exponential phases (Riihimaki and Pfaffli, 1978). The mean
amount of toluene expired during the "quantitatively significant" portion of the
excretion curve was calculated to be 45.9 umole (4.23 mg) Riihimaki and Pfaffli,
1978). Piotrowski (1967, reviewed in NIOSH, 1973) found that subjects exposed
dermally (with respiratory protection) to 1600 mg/m (427 ppm) toluene for
8 hours had no detectable increase in urinary excretion of benzoic acid (pre-
sumably analyzed after hydrolysis of conjugates).
Oral administration of toluene to rabbits resulted in a pattern of excretion
similar to that observed after inhalation exposure of humans. Rabbits (N = 2)
intubated with 350 mg toluene/kg body weight expired "iSI of the dose as the
parent compound within 14.5 hours; less than 1% of the dose was eliminated in the
expired air in the period from 14.5 through 35 hours after dosing (Smith eijt al.,
1954). In similar experiments from the same laboratory, rabbits intubated with
274 mg toluene/kg body weight excreted an average of 74? of the dose in the urine
as hippuric acid; excretion was complete with 24 hours of doseing (El Masrs
jet.al., 1956). The elimination of toluene and its metabolites from tissues and
blood of rats given toluene orally (Pyykko £t al., 1977) was similar to the
pattern already described after inhalation exposure (Pyykko et _al., 1977) except
that elimination after oral administration appeared to be delayed by a slower
rate of absorption than had been observed for inhalation exposure.
13-31
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The excretion of other metabolites of toluene (i.e., cresols, benzyl
alcohol, glucuronide and sulfate conjugates, benzylmercapturic acid) in the
urine of humans and animals has already been described in Section 13.3. With the
possible exception of benzoylglucuronide (Srbova and Teisinger, 1953)i none of
these excreted metabolites represented more than about 1% of the total dose of
\
toluene administered or absorbed (Angerer, 1979; Bakke and Sheline, 1970; Van
Doom .et al., 1980; Smith ^t al., 1954). Trace amounts of toluene were eli-
minated in the urine of humans exposed to toluene (Srbova and Teisinger, 1952).
Biliary excretion of toluene or its metabolites appeared to be negligible.
14
Rats given 50 mg C-toluene/kg body weight intraperitoneally excreted less than
2% of the administered radioactivity in the bile within 24 hours
(Abou-El-Markarem et al., 1967).
Most of the experimental work on the disposition of toluene in humans and
animals has focused on single exposures. The elimination of toluene is rapid
enough that few investigators have studied its potential accumulation with
repeated daily exposure. Ovrum and coworkers (1978) took samples of capillary
blood daily before work from 8 printers exposed occupationally to 35 to 353 ppm
toluene. No cumulative increase in blood concentrations of toluene was found
during the course of a 5-day work week. Konietzko and coworkers (1980) observed,
however, that toluene concentrations in peripheral venous blood tended to
increase during the course of a 5-day work week, although the ranges overlapped
(Table 13-3). Mean exposure concentrations, measured by a personal air sampling
method, did not increase during the week. The blood samples were taken before
work on Monday, Wednesday, and Friday from 8 workers exposed to 184 to 332 ppm
daily in a plastic processing factory. Concentrations in blood samples taken
after work were highly variable and did not seem to follow a consistent pattern.
13-32
-------
Table 13-3. Toluene Concentrations in Air and Peripheral Venous Blood (Konietzko et al., 1980)'
•
Monday Tuesday
Wednesday
Thursday Friday
[ Toluene in air
First week t
LO
i
LO
OJ
Second week
(ppm)
Toluene in blood before
exposure (ug/ml)
After exposure
'Toluene in air
(ppm)
Toluene in blood before
1 exposure (ug/ml)
[After exposure
225 233
(95-303) (153-383)
0.12
(0.09-0.24)
3.63
(2.3-4.75)
285 304
(145-473) (190-521)
0.27
(0.07-0.57)
11.60
(6.99-17.10)
209
(107-341)
0.51
(0.28-0.82)
6.69
(4.21-10.36)
309
(213-413) .
1.00
(0.35-151)
10.49
(3.24-20.31)
212 203
(92-314) (124-309)
0
(0
6
(3
.77
.29-1.67)
.70
.99-10.67)
232 191
(125-451) (105-432)
1
(0
5
(1
.21
.44-2.29)
.85
.94-9.78)
Means and range of eight workers are given in parentheses.
-------
In an analysis of 3155 samples of urine taken in the course of biological
monitoring from different workers on different days of the week and in different
workplaces, Lenhert _et ^1. (1978) observed that concentrations of hippuric acid
in the urine did not vary with the day of the week except on Monday, when the
concentrations were significantly higher than on other days. The authors conjec-
tured that the elevation of hippuric acid concentrations on Mondays was a result
of different eating habits on the weekend.
In experiments with dogs, exposure to 400 ppm for 7 hours/day for 5 consecu-
tive days did not result in an increase in the total amount of hippuric acid
excreted per day over the period of 5 days or change the time course of urinary
excretion (Von Oettingen et jl., 1942b). Nor did the concentration of toluene in
peripheral venous blood sampled at the end of exposure increase with day of
exposure.
13.5 SUMMARY
Toluene is readily absorbed through the respiratory tracts of humans and
experimental animals, as would be expected from its blood/air partition coeffi-
cient of approximately 15 (Sato and Nakajima, 1979 ; Sato _et al., 197Ma, 1974b;
Sherwood, 1976). The amount of toluene absorbed (uptake) is proportional to the
concentration in inspired air, length of exposure, and pulmonary ventilation
(respiratory minute volume) (Astrand e_t _al., 1972; Astrand, 1975; Veulemans and
Masshelein, 1978a).
The uptake of toluene by humans was about 50$ of the amount inspired
(Veulemans and Masshelein, 1978a; Carlsson and Lindqvist, 1977, Ovrum et al.,
1978). Total uptake (absorption) can be approximated as follows: Uptake = 0.5
• •
Ve Ci t, where Ve is the respiratory minute volume in 1/min, Ci is the inspired
concentration in mg/1, and t is the length of exposure in minutes (Ovrum et al.,
1978; Veulemans and Masshelein, 1978a). Because of its dependence on respiratory
13-34
-------
minute volume, the uptake of toluene is affected by the subjects' level of
physical activity (Astrand e± al., 1972; Astrand, 1975; Veulemans and
Masshelein, 1978a; Carlsson and Lindqvist, 1977). A subject's content of adipose
tissue had little or no effect on the uptake of toluene during exposure lasting
4 hours or less (Veulemans and Masshelein, 1978a; Astrand ^t al., 1972) except in
the case of extremely obese individuals (Carlsson and Lindqvist, 1977), and even
then the increased uptake may have been at least partly due to greater pulmonary
ventilation in the obese subjects than in the thin ones. Under "steady state"
conditions, peripheral venous concentrations of toluene correlated roughly with
exposure concentrations. Inter- and intraindtvidual variability were high
enough to make this an insensitive estimate of exposure concentration or uptake
(Von Oettingen _et al., 19**2a, 1942b; Veulemans and Masshelein, 1978b).
Although toluene appears to be absorbed less readily through the skin than
through the respiratory tract, percutaneous absorption of liquid toluene may be
significant. The maximum toluene concentration in peripheral venous blood of
subjects who immersed one hand in liquid toluene for 30 minutes was about 22$ of
the maximum concentration in peripheral venous blood of subjects who inhaled
100 ppm toluene vapor for 2 hours (Sato and Nakajima, 1978). Absorption of
toluene vapor through the skin in humans, however, probably amounts to less than
5% of the total uptake through the respiratory tract under the same conditions of
exposure (Riihimaki and Pfaffli, 1978; Piotrowski, 1967; reviewed in NIOSH,
1973). Absorption of toluene through the gastrointestinal tract appears to be
fairly complete, based on the amounts of toluene and its metabolites excreted by
experimental animals after administration of toluene (Pyykko _et al., 1977;
El Masri et al., 1956; Smith e_tal., 1954).
Toluene appers to be distributed in the body in accordance with the tissue/
blood distribution coefficients and its metabolic and excretory fate. Thus,
13-35
-------
toluene itself is found in high concentrations in adipose tissue and bone marrow,
and toluene and its metabolites are found in moderately high concentrations in
liver and kidney (Peterson and Bruckner, 1978; Bruckner and Peterson, 198la;
Carlsson and Lindqvist, 1977; Pyykko et al., 1977; Bergman, 1979). The time
course of toluene concentrations in the brain appeared to correlate with beha-
vioral effects (Peterson and Bruckner, 1978; Bruckner and Peterson, 198la).
The major portion of inhaled or ingested toluene is metabolized by side-
chain oxidation to benzoic acid, conjugated with glycine to form hippuric acid,
and excreted in the urine. Regardless of the route of administration, dose, or
species, 60 to 75$ of the absorbed (inhalation) or administered (oral) toluene
could be accounted for as hippuric acid in the urine (Veulemans and Masshelein,
1979; Ogata jjt al., 1970; El Masri _et jil., 1956). Much of the remaining toluene
(to 18$) was exhaled unchanged (Nomiyama and Nomiyama, 1971b; Srbova and
Teisinger, 1952, 1953; Smith e_t _al., 195*0. Two percent or less appeared in the
urine as cresols and benzylmercapturic acid. These metabolites are of concern
because they indicate formation of reactive intermediates that potentially could
bind to tissue macromolecules. No evidence of covalent binding to tissue com-
11
ponents has been detected, however, by autoradiography of mice that inhaled C-
toluene (Bergman, 1979).
Most of the toluene absorbed by humans or animals after inhalation or oral
exposure is excreted within 12 hours of the end of exposure (Ogata et al_., 1970;
Veulemans and Masschelein, 1979; Nomiyama and Nomiyama, 1978; Smith^t jil., 1951;
Bergman, 1979). In experimental animals, elimination of toluene and its metabo-
lites from most tissues, including brain, was rapid; elimination from fat and
bone marrow was slower (Peterson and Bruckner, 1978; Bruckner and Peterson,
198la; Pyykko et al., 1977; Carlsson and Lindqvist, 1977).
13-36
-------
In humans, the time course of desaturation after cessation of inhalation
exposure appeared to consist of 3 exponential phases with half-lives of 1.95,
35.2, and 204 minutes for toluene concentrations in peripheral venous blood and
1.59, 26.5, and 221 minutes for toluene concentrations in alveolar air (Sato
e_t al., 1974). Toluene concentrations in expired air or peripheral venous blood
after the end of inhalation exposure were not reliable indicators of toluene
uptake or of exposure concentrations because of the great variability among
individuals (Veulemans and Masshelein, 1978a, 1978b'; Astrand e_t al., 1972). Some
of this variability, particularly in expired air concentrations, could be
explained by differences in exercise load during'-exposure, in respiratory minute
volumes after exposure, and in adipose tissue content (Veulemans and Masshelein
1978a, 1978b). Similarly, although the excretion of hippuric acid in the urine
is roughly proportional to the degree of exposure to toluene, inter- and intra-
individual variations in the physiological excretion of hippuric acid render
quantification of exposure or uptake from urinary hippuric acid concentration or
excretion rates unreliable (Immamura and Ikeda, 1973; Veulemans e_t al., 1979;
Veuleroans and Masshelein, 1979; Ogata _et al., 1971; Wilczok and Bienick, 1978;
and others as reported in Section 13.4).
13-37
-------
14. CARCINOGENICITY, MUTAGENICITY, AND TERATOGENICITY
14.1 CAR CINOGENI CITY
In the 24-month chronic inhalation study described in Section 12.2.2, CUT
(1980) concluded that exposure to toluene at concentrations of 30, 100, or
300 ppm did not produce an increased incidence of neoplastic, proliferative,
inflammatory, or degenerative lesions in Fischer-344 male or female rats rela-
tive to unexposed controls.
The NCI/NTP Carcinogenesis Testing Program has initiated bioassays of com-
mercial toluene in rats and mice exposed via inhalation and gavage (NTP, 1981).
Prechronic testing is currently in progress.
Toluene has been utilized extensively as a solvent for lipophilic chemicals
being tested for their carcinogenic potential when applied topically to the
shaved skin of animals. Results of control experiments with pure toluene have
been uniformly negative. Poel (1963), for example, applied toluene (volume not
stated) to the shaved interscapular skin 3 times a week throughout the lifetime
of 54 male SWR, C3HeB, and A/He mice and found no carcinogenic response. Coombs
et, al_. (1973) treated the dorsal skin of 20 randomly bred albino mice with 1 drop
of toluene (6 ul) twice a week for 50 weeks. There was no evidence of squamous
papillomas or carcinomas in the mice 1 year following termination of exposure,
but survival was only 35% (7/20). Doak e_t _al. (1976) applied estimated toluene
volumes of 0.05-0.1 ml/mouse to the backs of CF1, C,H, and CBaH mice (approxi-
mately 25 mice of each sex of each strain) twice weekly for 56 weeks, and failed
to elicit skin tumors or a significantly increased frequency of systemic tumors
over untreated controls. It is not clear in these studies, however, whether the
toluene was applied under an occlusive dressing or allowed to evaporate.
Lijinsky and Garcia (1972) did report a skin papilloma in 1 mouse and a skin
14-1
-------
carcinoma in a second mouse in a group of 30 animals that were subjected to
topical applications of 16-20 ul of toluene twice a week for 72 weeks.
Frei and Kingsley (1968) examined the promoting effect of toluene in Swiss
mice following initiation with 7,12-dimethylbenzfa]anthracene (DM3A). In this
study, the ears of the mice were topically treated once with 0.1 ml of 1.5$ DM3A
in mineral oil and subsequently, beginning a week later, twice a week with the
same volume of 100$ toluene for 20 weeks. Results showed that 11 of 35 mice
developed tumors (6 permanent, 5 regressing) compared with 8 of 53 negative
controls treated with 100$ mineral oil (Table 14-1). In 14 mice painted with
100$ toluene but no DM3A initiator, 2 developed tumors (1 permanent, 1 regress-
ing). In another study with an identical experimental design, Frei and Stephens
(1968) similarly found that 100$ toluene promoted a yield of tumors no different
from that found in the controls (Table 14-1). In this study, a total of 7 tumors
were found in 35 surviving mice treated with toluene following initiation with
DM3A; the negative control group (DM3A followed by biweekly applications of
mineral oil) had 8 skin tumors in 53 survivors after the 20 weeks.
14.2 MUTAGENICITY
14.2.1 Bacterial DNA Damage/Repair Assays
The ability of toluene to induce DNA damage has been evaluated in two
studied by comparing its differential toxicity to wild-type and DNA repair-
deficient bacteria (Fluck ^t al., 1976; Mortelmans and Riccio, 1980). Two
species have been tested with negative results: Escherichia coli W3110 and p3478
(polA* and polA", respectively) and Salmonella typhimurium SL4525 (rfa) and
SL4700 (rfa) (rec* and rec", respectively). In the first study, Fluck et al.
(1976) applied toluene (25 ul/plate) without metabolic activation directly to
wells in the center of culture plates containing the E. coli and found no zones
of growth inhibition with either strain. In the Mortelmans and Riccio (1980)
14-2
-------
Table 14-1. Epidermal Tumor Yield in 20-Week Two-Stage Experiments'
DHBA Promoting Agent
+ None
+ 5* oroton oil6
+ 100* toluene
-f 100* mineral oil
5* croton oilc
_, - 100* toluene
-tr
' + None
+ 5* croton oll°
+ 100*
+ 5* croton oil
5* croton oil°
100* toluene
No. Surviving
Mice
23b
33b
35b
53b
25b
Ilb
23d
33e
35d
53e
20d
,1d
Tumor
bearing
survivors
NR
NR
NR
NR
NR
NR
1*
88*
It*
11*
5*
0*
Number of Tumors
Permanent
0
381
6
8
1
1
-
NR
NR
NR
NR
NR
0
Regressing
0
70
5
0
2
1
NR
NR
NR
NR
NR
0
Total
0
451
11
8
3
2
1
352
7
8
1
0
Tumors
per
Survivor
0
13.7
0.31
0.15
0.11
0.11
0.04
10.7
0.2
0:15
0.05
0
Regressing
Tumors
(» Reference
0 Frei and Kingsley,
1968
15.5
45.4
0
66.6
5.0
NR Frei and Stephens,
1968
NR
NR
NR
NR
0
NR = not reported. aEars of Swiss mice treated once with 0.1 ml of 0.5* DMBA and subsequently, beginning 1 week later, twice a week with the promoting
agent.
Not specifically stated whether this is the number of surviving mice. Also, the number of mice at the start not stated.
In mineral oil.
30 mice at the start.
e60 mice at the start.
-------
study growth inhibition was also found to be comparable with both the wild-type
and repair-deficient strains of the IS. coli and Salmonella typhimurium when
sterile filter discs inoculated with 0.001-0.01 ul toluene were placed in the
centers of culture plates; these assays were performed both with and without
metabolic activation. In quantitative growth inhibition tests, Mortelmans and
Riccio (1980) again found that toluene (0.001-0.01 ul/plate) was not differen-
tially toxic to either the DNA re pair-sufficient or re pair-deficient strains of
the E. coli or Salmonella typhimurium. In these assays, the toluene was pre-
incubated in liquid suspension with the bacteria, with and without S-9 activa-
tion, prior to plating; following plate incubation, the numbers of surviving
cells were counted and recorded (instead of measuring the diameter of the zone of
growth inhibition).
14.2.2 Mutagenesis in Microorganisms
Reverse mutation testing of toluene was negative in Salmonella typhimurium
tester strains TA1535, TA1537, TA1538, TA98, and TA100 (Litton Bionetics, Inc.,
1978a; Mortelmans and Riccio, 1980; Nestmann _et _al., 1980 ; Bos e^t al., 1981 ; Snow
jet al., 1981), Escherichia coli WP2 (Mortelmans and Riccio, 1980), and
Saccharomyces cerevisiae 07 (Mortelmans and Riccio, 1980). The details of these
studies are summarized in Table 14-2. All assays were performed in the presence
and in the absence of Aroclor 1254-induced rat liver homogenate (S-9) and
employed positive and negative controls. It should be noted that there may have
been significant losses of toluene from the culture media during incubation in
all but one of the aforementioned studies (Snow £t jl., 1981), particularly at
the higher doses tested. Snow_et_al. (1981) conducted plate incorporation assays
in sealed plastic bags and chambers as well as vapor exposures in desiccators to
prevent excessive evaporation. The design of the Snow ^t jl. (1981) study is
14-4
-------
Table 14-2. Microbial Mutagenicity Assays
Table 11-2. Microbial Mutagenicity Assays
•P-
I
Test
Reverse Mutation
Salmonella
typhimurium
Salmonella
typhiffiurium
Salmonella
typhiraurium
Salmonella
typhimurium
Salmonella
typhimurium
Escherichia
coll
Sacoharomyees
cerevislae
Mi to tic Crossing-Over
Saccharoroyces
cerevisiae
Indicator Metabolic
Strains Activation8
Footnote b +
Footnote b +
Footnote b +
Footnote b +
d
TA98, TA100 id
WP2 +
VI +
D7 +
Mitotic Gene Conversion
Saccharoroyces „,. +
cereviaiae
Saccharoroyces
cerevisiae
D7 +
Dose
0. 001-5. Oul/plate
0.001-0.031$
0.01-IOMl/plate
5 pi/ plate
0. 115-2.3 Ill/plate
0.3 ill- 100 |il/ plate
11-3761 ppm
0.01-10 ul/ plate
0. 001-0. 5*g
0. 001-5. OJg
0.001-5. Ogl/plate
0. 138-1. 1J°
0. 001-5- OJ6
Application Response
Plate incorporation
Liquid suspension
Plate Incorporation
Plate incorporation
Plate incorporation
Plate incorporation
Vapor exposure
P.I ate incorporation
Liquid suspension
Liquid suspension
Plate Incorporation
Liquid suspension
Liquid suspension
Reference
Litton Bionetics, Inc.
Mortelmans and Riccio,
Nesbnann et al. , 1980
Bos et al. , 1981
Snow jet a±. , 1981
Mortelmans and Riccio,
Mortelraans and Riccio,
Mortelmans and Riccio,
Litton Bionetics, Inc.
Mortelmans and Riccio,
, 1978a
1980
1980
I960
1980
, 1978a
1980
Aroclor 1251-induced rat liver homogenate S-9 fraction.
Strains TA98, TalOO, TA1535, TA1537, and TA1538 tested.
50i mortality at the highest dose.
The toluene was tested with both Aroclor-induced S-9 and toluene-induced S-9.
The plates were incubated In sealed plastic bags or chambers for part of a 72-hr incubation period; in the Aroclor-induced S-9 tests,
the plates were removed from the bags after 18 hr, counted, incubated an addition 21 hr, and recounted; in the experiments with toluene-induced
S-9 the plates were removed after 21 hr to prevent moisture and spreading problems, and then incubated an additional 18 hr before counting.
The assays were run in a sealed incubation chamber with a second glass plate (open) which contained the toluene; after 21 hr the chambers
were opened and the plates incubated for an additional 18 hr.
8100> mortality at 0. \% and 0.5*.
-------
also noteworthy because the toluene was tested with toluene-induced rat liver S-9
fraction as well as with Aroclor-induced S-9.
Toluene, with and without metabolic activation, was also tested for its
ability to induce mitotic crossing-over in the yeast Saccharomyces cerevisiae D7
(Mortelmans and Riccio, 1980) and mitotic gene conversion^, cerevisiae D4 and D7
(Litton Bionetics, Inc., 1978a; Mortelmans and Riccio, 1980). Toluene did not
elicit a positive response in any of these tests (Table 14-2).
14.2.3 TK Mutation in L5178Y Mouse Lymphoma Cells '
Litton Bionetics, Inc. (1978a) reported that toluene failed to induce
specific locus forward mutation in the L51?8y Thymidine Kinase (TK) mouse
lymphoma cell assay. Toluene was tested at concentrations of 0.05-0.30 yl/ml,
with and without mouse liver S-9 activation.
14.2.4 CytogenetLc Test Systems
14.2.4.1 Micronucleus Test
It was recently reported by SRI International (Kirkhart, 1980) that the
intraperitoneal administration of toluene to male Swiss mice failed to cause an
increase in micronucleated polychromatophilic erythrocytes in the bone marrow.
Doses of 250, 500, and 1000 mg/kg were administered to groups of 32 mice at 0 and
24 hours, with sacrifices 30, 48, and 72 hours after the first dose
(8 mice/sacrifice). Five hundred polychromatic erythocytes per animal were
evaluated for the presence of micronuclei. The highest dose tested (1000 mg/kg)
approximated the LD50 for male mice (Koga and Ohmiya, 1978).
14.2.4.2 Chromosomal Aberrations
Two reports from the Russian literature have concluded that toluene induced
chromosomal aberrations in rat bone marrow cells following subcutaneous injec-
tion (Dobrokhotov, 1972; Lyapkalo, 1973). In an analysis of 720 metaphasal disks
from the bone marrow of 5 rats that had been subcutaneously injected with
14-6
-------
0.8 g/kg/day toluene for 12 days, Dobrokhotov (1972) found that 78 (13$) showed
metaphase aberrations. Sixty-six percent of the induced aberrations were
chromatid breaks, 24$ were chromatid fractures, 7% were chromosome fractures,
and 3% involved multiple aberrations. The frequency of spontaneous aberrations
in 600 metaphasal marrow disks from 5 control rats injected with vegetable oil
averaged 4.16$ (65.8$ were breaks and 32.4$ were chromatid aberrations; no frac-
tures vor multiple injuries were recorded.). It was further found that similar
administration of 0.2 g/kg/day of benzene induced a frequency of chromosomal
damage (13.6$) comparable to that of 0.8 g/kg/day of toluene, and that when a
mixture of 0.2 g/kg benzene and 0.8 g/kg benzene was injected daily for 12 days,
the damage was approximately additive (33.33$ aberrations). The significance of
the positive elastogenic effects attributed to toluene are difficult to assess,
however, because the purity of the sample employed was not stated, and because
the distinction between chromatid breaks and gaps is unclear.
Lyapkalo (1973) administered 1 g/kg/day toluene to 6 rats and 1 g/kg/day
benzene to 8 rats by subcutaneous injection for 12 days. Treatment with toluene
reportedly resulted in chromosome aberrations in 11.6$ of the bone marrow cells
examined (84 aberrant metaphases/724 cells) compared with 3.87$ (40/1033) in
olive oil injected controls. The types of aberrations that were observed con-
sisted of gaps (60.47$), chromatid breaks (38.37$) and isocromatid breaks
(1.16$). Benzene caused a greater degree of chromosome damage than the toluene
(57-2$ of the cells examined had aberrant chromosomes (573/1002)), and the dis-
tribution of aberration types was different (44.72$ gaps, 50.94$ chromatid
breaks, 4.34$ isochromatid breaks). The purity of the toluene used in this study
was not stated.
In a third Russian study, Dobrokhotov and Einkeev (1975) reported that rats
exposed to 80 ppm (610 mg/nr) toluene via inhalation, 4 hours daily for
14-7
-------
4 months, showed damaged metaphase chromosomes in 21.6? of the bone marrow cells
analyzed. The percentage of metaphases with damaged chromosomes in bone marrow
cells from air-exposed control rats was 4.02$. Inhalation of 162 ppm benzene
caused damage to chromosomes in 21.56$ of the marrow cells, and a mixture of the
toluene and benzene (80 and 162 ppm, respectively) damaged chromosomes in an
additive manner (41.21$ of the cells were involved). Chromosome damage was also
observed in all of the groups 1 and 2.5 months after the initial exposure and one
month after inhalation, the frequency of chromosome damage was still elevated. A
total of 96 rats were used in this study, but the number of rats sacrificed in
each group was not stated; it should also be emphasized that the number of cells
scored and the purity of the toluene used were not reported.
In contrast to the aforementioned Russian cytogenetics studies, Litton
Bionetics, Inc. (1978) found that intraperitoneal injection of pure toluene into
Charles River rats did not induce bone marrow chromosomal aberrations. Toluene
was injected at dose levels of 22, 71, and 214 mg/kg in two different experi-
ments. In one study, 5 rats were sacrificed at 6, 24, and 48 hours following
injection of each dose; in a second study, 5 rats were dosed daily at each level
for 5 days, and the rats were sacrificed 6 hours after injection of the last
dose. Approximately 50 cells per animal were scored for damage. Dimethyl
sulphoxide (DM50) (the solvent vehicle) administered intraperitoneally at
0.65 ml/rat was used as a negative control, and triethylene melamine (TEM) in
saline at 0.3 mg/kg was used as a positive control. The results of the bone
marrow cytogenetic analyses following sacrifice are summarized in Table 14-3.
It was also noted that none of the observed aberrations differed significantly in
frequency or type from either concurrent or historical spontaneous values.
Gerner-Smidt and Friedrich (1978) reported that toluene at concentrations
of 1.52, 152, and 1520 ug/ml did not influence the number of structural
11-8
-------
Table 14-3.
Rat Bone Marrow Cell Aberrations Following Intraperitoneal Injection of Toluene
(Litton Bionetics, Inc., 1978a)
Treatment Dose
DHSO 0.65 ml/rat
(Solvent)
Triethylene 0.3 rag/kg
Helarolne
Toluene 22 rag/ kg
Toluene 71 mg/kg
Toluene 211 mg/kg
Time of
Sacrifice
6 h
21 h
MB h
6 h (SA)D
21 h
6 h
21 h
48 h
6 h
6 h
21 h
48 h
6 h
6 h
21 h
18 h
6 h (SA)d
No. of
Animals
5
5
5
5
5
5
5
5
5
5
5
3
5
5
5
5
5
Total No.
of Cells
225
250
250
227
250
250
212
250
238
239
227
150
212
250
250
250
250
Type and Frequency
of Aberrations
Structural0 Numerical
2f,ltd
—
1tb,1f
ltd
11tb,2sb,5ar,l5r, 2pp
26t,1r,10td,12>,
Ipu, 1qr,2ao, 3tr
—
—
—
3f
ltd 1pp
2td,1af,1f
—
--
If 2pp
1PP
Itb.ltd
1td,3af
No. of Cells
With One or More
Aberrations
3 (1.3*)
0 (0.0*)
2 (0.851)
1 (O.i)»)
72 (28.8*)
0 (0.0*)
0 (0.0»)
0 (0.0*)
2 (0.8*)
2 (0.8*)
1 (1.8*)
0 (0.0»
0 (0.0*)
3 (1.2*)
1 (0.1)*)
2 (0.8*)
2 (0.3*)
No. of Animals
Without
Aberrations
3
5
1)
1|
0
5
5
5
3
i)
3
3
5
3
M
3
3
Mltotiq
T j d
Index
3.8
6.0
6.1
5.0
1.D
3-1
5.9
7.0
6.3
2.5
').3
5.7
3.3
M.5
3.6
5.1
5.1
8The toluene used was 99-96 wt. J pure (ethylbenzene, 0.03*; jg-xylene, <0.01*; m-xylene, <0.01>; sulfur, 0.1 ppm) (Fowle, 1981).
SA = subacute study; rats were dosed dally for 5 days, with sacrifice 6 hours after the last dose.
'af = acentric fragment (2 tid); f = fragments; pp = pclyplold; pu = pulverized chromosome; qr = quadriradlal; r = ring; sb = chromosome break;
t = translocation; tb = chroma tid break; td = chromatld deletion; tr = triradial; > = greater than 10 aberrations.
based on a count of at least 500 cells per animal.
-------
chromosomal aberrations in cultured human lymphocytes. Benzene and xylene at the
same concentrations also had negative clastogenic effects but toluene (152 and
1520 ug/ml) and xylene (1520 ug/ml) caused a significant cell growth inhibition
which was not observed with benzene. The data from this study cannot be ade-
quately evaluated, however, because the source and purity of the toluene were not
stated, no positive control experiments were performed, no metabolic activation
system was employed, and the type of chromosome damage scored was not specified.
Peripheral blood lymphocytes of toluene-exposed rotogravure workers have
also been examined for chromosome aberrations with negative results. In one
study, Forni and coworkers (1971) examined the lymphocyte chromosomes from 34
workers from a single plant and 34 controls from outside the plant matched for
age and sex. Ten of the workers were exposed daily to minimum concentrations of
131-532 ppm benzene for 2-7 years and subsequently to toluene in the general
range of 200-400 ppm for 14 years; 24 of the workers were exposed only to toluene
for 7-15 years. (The ink solvent used in this plant was changed from benzene to
toluene which contained some xylene, but reportedly no benzene, after an outbreak
of benzene poisoning in 1954.) No significant differences were found between the
toluene and control groups in frequencies of stable and unstable chromosome
aberrations or in chromosome counts (Table 14-4). Approximately 100 metaphases
from each subject or control were scored. The proportion of chromosome changes
were significantly higher statistically in the benzene/toluene group compared
with controls, and in the benzene/toluene group relative to the toluene group.
Maki-Paakkanen je_t jl. (1980) recently found no evidence of clastogenicity
in cultured peripheral blood lymphocytes from 32 printers and assistants from two
different rotoprintLng factories who had a history of exposure to pure toluene
(benzene concentration, >Q.Q5%', average benzene concentration, 0.006/&) at 8-hour
time-weighted average (TWA) concentrations of 7-112 ppm. The average age of the
14-10
-------
Table 14-4. Frequency of Unstable and Stable Chromosome Changes and Chromosome Counts in
Subjects Exposed to Benzene or Toluene or Both (Forni et_ al., 1971)
4=-
I
No. of
Expsoure Subjects Cases
Age
Range
Total
Cells
Counted
% Cells
c a
u
% Cells With Chromosome Number
cb
3
16
(Polyploid)
Benzene (+ toluene) 10
Toluene 21
Control subjects 34
36 -5 'I
29-60
25-60
96'l
2,100
3,262
1.66(1.87)c>d'e
0.80(0.83)°
0.61(0.67)
0.62d'e
0.08
0.09
13.1 86.0
1'l.3 85.1
10.2 89.5
0.9(0.52)
0.3(0.29)
0.3(0.3)
Cells with "unstable" chromosome aberrations (fragments, dicentrics, ring chromosomes). The presence of each
fragment was considered as one break, the presence of a dicentric or ring chromosome as two breaks.
Cells with "stable" chromosome changes (abnormal monocentric chromosomes due to deletions, translocations,
etc., trisomles).
Numbers in parentheses show percentage of calculated breaks.
Difference from toluene group was significant (P < 0.05).
Difference from control was significant (P < 0.01).
-------
workers was 34.2 years and the average length of employment was 14.6 years.
Results of analyses showed that when frequencies of chromosome aberrations were
compared with those of 15 unexposed research institute workers, there were no
significant differences (Table 14-5). Similarly, no significant deviations were
observed in the frequencies of aberrations in relation to duration of exposure.
In a report on chromosome aberrations of women in laboratory work,
Funes-Cravioto et _al. (1977) also presented data on 14 workers who were exposed
to toluene in a rotogravure factory. Exposures ranged from 1.5-26 years and air
concentrations of toluene showed TWA values of 100-200 ppm, with occasional
rises up to 500-700 ppm; the exposures were sufficient in most cases to elicit
frequent headaches and fatigue, and occasional vertigo, nausea, and feelings of
drunkenness. The workers had been exposed to toluene since approximately 1950;
)
before 1958, it was stated that the toluene was probably contaminated by a "low"
percentage of benzene. Results of lymphocyte analysis showed an excess of
chromosome aberrations (abnormal chromosomes and breaks) in the 14 toluene-
exposed workers relative to a control group of 42 adults. It should be noted,
however, that only a small number of subjects were examined in this study and the
exposure background (e.g., extent of exposure to benzene and other chemicals) of
the group was not well characterized. The results of this study are presented in
Table 14-6. The results of chromosome analyses of 8 other workers with definite
exposure to benzene (concentration not measured) for 2-10 years prior to 1950,
and subsequently to toluene as stated above, are included for comparison.
14.2.4.3 Sister Chrcmatid Exchange
Gerner-Smidt and Friedrich (1978) reported that in vitro exposure to
toluene at concentrations of 15.2, 152, and 1520 yg/ml had no effect on the
number of sister-chromatid exchanges (SCEs) in cultured human lymphocytes, but
no positive control experiments were performed and no metabolic activation
14-12
-------
Table 14-5 Effect of Occupational Toluene Exposure and Smoking on Chromosomal Aberrations
and Sister Chromatid Exchanges (Maki-Paakkanen e^ al., 1980)
Cells with Chromosomal Aberrations (!)
Gaps Excluded
•
—A
-Cr
1
OJ
Occupational
Toluene Exposure
(yr)
Total Worker
( 11.6-yr average
Total Control
0 (controls)
Non smokers
Smokers
Total
1-10 (mean, 8.0)
Non smokers
Smokers
Total
>10 (mean, 19-3)
Non smokers
Smokers6
Total
No. of
Subjects
32
exposure)
15
1
11
15
3
10
13
11
8
19
Mean
Age
(yr)
34. 2d
31.2"
31-0
35.5
31.3
27-7
28.2
28.1
38.5
35.9
37.5
Cells
Analyzed3
—
800
1100
1900
300
1000
1300
1100
800
1900
Chromatid
Type
1.0
0.7
0.5
0.9
0.7
0.7
0.7
0.7
0.8
1.8
1.2
Chromosome
Type
0.5
0.9
0.8
1.0
0.9
0.3
0.3
0.3
0.5
0.8
0.6
Total
1.5
1.6
1.3
1.8
1.6
1.0
1.0
1.0
1.1
2.5
1.8
Sister Chroraatid Exchanges (SCEs)
Gaps Included Cells ,_
Total
2.5
2.7
2.3
3-1
2.7
2.3
1.9
2.0
2.5
3-1
2.8
Analyzed
—
231
318
552
79
295
371
330
205
535
Mean per Subject
per Cell0
8.5
8.9
8.0
9.7"
9.2
7.9
9- 1""
8.8
7.5
9.6""
8.3
Abbreviation: yr = year
a100 cells
~*n —— .1 i « «
analyzed per Individual.
Calculated from individual means.
Mean value.
eSCEs vere analyzed from 7 subjects: f*P < 0.01 and •»• P< 0.001 compared to nonsmokers in the group, one-tailed S tudent1 s ^-test.
-------
Table 14-6. Chromosome Aberrations in Rotoprinting Factory Workers
(Funes-Cravioto e_t al., 1977)
Control
Group
Toluene
Benzene/T oluene
No. of Subjects
Age (year)
Range
Mean
No. of Cells Analyzed
Total
Abnormal
Total
Frequency range (%)
Mean frequency (?)
No. of Chromosomes Analyzed
Total
Breaks
Total
Range (per 100 cells)
Mean (per 100 cells)
49
0.16-63
24.4
5000
217
0-20
4.3
230 , ooo
233
0-22
5.1
14.
23-54
37.2.
1,400
108
2-15
7.7
64,400
124
2-17
8.9
8
54-65
61.3
800
76
4-17
9.5
36 , 800
95
6-17
11.9
Exposure details provided in accompanying text.
14-14
-------
system was employed. Twenty-six cells/dose were scored for SCEs andcytotoxicity
was observed at the highest dose. Evans and Mitchell (1980) concluded that
toluene did not alter SCE frequencies in cultured Chinese hamster ovary (CHO)
cells. In the latter study, CHO cells without rat liver S-9 activation were
exposed to 0.0025^-0.04$ toluene for 21.4 hours, and CHO cells with activation
were exposed to 0.0125/6-0.21$ for 2 hours.
In an analysis of cultured peripheral blood lymphocytes from 32 rotogravure
workers with daily chronic exposure to 8-hour TWA concentrations of 7-112 ppm
pure toluene, Maki-Paakkanen ^t jl. (1980) found no increase in SCEs relative to
a group of 15 unexposed control subjects. The a'verage age of the workers was
34.2 years and their average length of employment was 14.6 years. The SCE
analysis was part of a study examining chromosomal aberrations in these workers;
the exposure history of the subjects is described in more detail with the summary
of the aberration findings (Subsection 14.2.4.1), and the results of the SCE
analyses are included in Table 14-5.
Funes-Cravioto ^t _al. (1977) studied SCE formation in groups of 4 rotogra-
vure printers, 12 laboratory technicians, and 4 children of female laboratory
technicians. The printers had been exposed to benzene during the 1940's for 2-
10 yers and subsequently to toluene; exposure to benzene and toluene ranged from
2-26 years. TWA concentrations of toluene generally ranged from 100-200 ppm
(occasionally to 500-700 ppm), but benzene concentrations were not measured.
The technicians also had a history of exposure to toluene, but the exposures were
poorly characterized (duration and concentrations not stated) and each had con-
siderable concurrent exposure to other solvents as well, particularly benzene
and chloroform. Results of peripheral lymphocyte analysis (20 cells/individual
scored) showed a statistically significant increase in SCEs in the laboratory
technicians and the children of female technicians, but not in the exposed
14-15
-------
printers; however, due to the nature of the exposure, the increases noted cannot
be exclusively attributed to toluene.
14.3 TERATOCENICITY.
14.3.1 Animal Studies
Toluene was reported in a recent abstract, to be teratogenic in CD-1 mice
following oral exposure (Nawrot and Staples, 1979). Toluene was administered by
gavage from days 6-15 of gestation at levels of 0.3, 0.5, and 1.0 ml/kg/day and
from days 12-15 at 1.0 ml/kg/day. The vehicle used was cottonseed oil (0.5$ of
maternal body weight per dose). A significant increase in embryonic lethality
occurred at all dose levels on days 6-15, and a significant reduction in fetal
weight was measured in the 0.5 and 1.0 ml/kg groups. After exposure to toluene
on days 6-15 at 1.0 ml/kg, a statistically significant increase in the incidence
of cleft palate was noted which reportedly did not appear to be due merely to a
general retardation in growth rate; however, when toluene, at a level of
1.0 ml/kg, was administered on days 12-15 decreased maternal weight gain was the
only effect observed. Maternal toxicity was not seen after exposure to toluene
on days 6-15 at any dose level. It should be emphasized that the numbers of mice
exposed and the numbers of fetuses examined were not stated in the available
abstract of this study; a complete copy of this report is not available for
review but has been submitted for publication.
Hudak and Ungvary (1978) recently concluded that toluene was not terato-
genic to CFLP mice or CFY rats when administered via inhalation according to the
following schedule:
Dose Days of Pregnancy Duration
CFPL mice 133 ppm (500 mg/m3} 6-13 24 hours/day
399 ppm (1500 mg/m3) 6-13 24 hours/day
CFY rats 266 ppm (1000 mg/m3) 1-21 8 hours/day
399 ppm (1500 mg/m3) 1-8 24 hours/day
399 ppm (1500 mg/m3) 9-14 24 hours/day
14-16
-------
It was found that the entire group of mice exposed to 399 ppm toluene died within
24 hours. Toluene administered to rats at 339 ppm also had an effect on material
survival, but none of the exposures adversely affected the incidence of external
or visceral malformations in either species relative to air-exposed controls
(Table 14-7). An increased incidence of skeletal anomalies (fused sternebrae,
extra ribs) was observed, however, in the rats exposed continuously to 399 ppm
toluene on days 9-14, and signs of retarded skeletal development (including
poorly ossified sternebrae, bipartite vertebra centra, and shortened 13th ribs)
were found in the rats exposed on days 1-8 (399 ppm) and during the entire period
of pregnancy (days 1-21) at 266 ppm for 8 hours/day. An embryo toxic effect of
toluene was further indicated by low fetal weights in the mice, and in the rats
exposed on days 1-8 of pregnancy. Fetal loss (percent of total implants), mean
litter size, mean placental weight, and maternal weight gain were unaffected by
exposure in either species.
In a more recent teratogenicity study, groups of 20 CFY rats were exposed to
266 ppm (1000 mg/nr) toluene, 125 ppm (400 mg/nr) benzene, or a combination of
these concentrations of toluene and benzene for 24 hours/day on days 7-14 of
gestation (Tatrai e_t al., 1980). A group of 22 rats inhaling pure air served as
controls, and the fetuses were examined on day 21 of pregnancy. The results of
the toluene exposures in this study are consistent with those of Hudak and
Ungvary's continuous 399 ppm toluene exposures with rats on days 9-14 of gesta-
tion. Tatrai £t al. (1980) concluded that the exposures to 266 ppm toluene were
not teratogenic (no external, internal, or skeletal malformations were
reported), although the exposures were associated with evidence of skeletal
retardation (not detailed) and an increased incidence of extra ribs (Table 14-8).
It was additionally found that the incidence of extra ribs was higher in the
group exposed to toluene in combination with benzene than in the groups exposed
14-17
-------
Table 14-7. Teratogenicity Evaluation of Toluene in CFY Rats and CFLP Mice (Hudak and Ungvary, 1978)
Air Inhalation
Days 1-21
8 h/d
Toluene
266 ppm
Days 1-21
8 h/d
399 ppn>
Days 1-8
24 h/d
Rats
Air Inhalation
Days 9-14
21 h/d
Toluene
399 ppm
Days 9-14
24 h/d
Air Inhalation
Days 6-13
24 h/d
Mice
Toluene
133 ppm
Days 6-13
24 h/d
399 ppm
Days 6-13
24 h/d
No. pregnant animals examined
No. pregnant animals died
Maternal weight gain3 (*)
No. live fetuses
No. resorbed fetuses
No. dead fetuses
Fetal loss (J)
Mean litter size
Mean fetal weight (g)
Mean placental weight (g)
Weight retarded fetusesb (%)
External malformations
No. fetuses dissected
Internal malformations6
Anophthalmia
llydrocephalus
Hydronephorosis
No. of Alizarin-stained
fetuses
Skeletal retardation signs
10
0
46.6
111
8
0
6.7
11.1
3.8
0.5
7-2
0
54
0
—
1
57
0
10
0
44.1
133
3
0
2.2
13.3
3.6
0.5
16
0
64
0
—
6
69
17"
9
5
44.0
95
6
0
5.9
10.6
3.3"
0.5
46 "
0
49
0
4
4
42
7"
26
0
46.9
348
15
0
4.1
13.1
3-8
0.5
6.9
0
179
1
_..
16
169
11
19
2
41.8
213
18
0
7.8
11.2
3.8
0.5
17.3
0
110
0
—
4
102
24»»
14
0
—
124
6
1
6.1
9.0
1.1
—
6.5
0
64
0
—
1
60
3
11
0
—
112
10
0
8.2
10.2
1.0*
—
27.6"
0
58
0
—
3
54
1
0
15
0
0
0
0
—
—
—
—
0
—
—
—
—
—
-------
Table 14-7. Teratogenicity Evaluation of Toluene in CFY Rats and CFLP Mice (Hudak and Ungvary, 1978) (Cont.)
Air Inhalation Toluene
Days 1-21
8 h/d
266 ppm
Days 1-21
8 h/d
399 ppm
Days 1-8
21 h/d
Hats
Air Inhalation Toluene
Days 9- It
21 h/d
399 ppm
Days 9-11
21 h/d
Air Inhalation
Days 6-13
21 h/d
Mice
Toluene
133 ppm
Days 6-13
21 h/d
399 ppm
Days 6-13
21 h/d
Skeletal anomalies
Fused sterne brae 0
Extra ribs 0
Skeletal malformations8
Missing vertebrae 0
Brachlmelia 0
0
0
0
0
0
0
0
0
2
0
0
0
7"
22"«
2
0
0
0
0
1
0
0
0
0
—
—
Abbreviations: h = hour; d = day.
•P < 0.01 U-test); «» V < 0.05 (Mann Whitney U Test); ••• P < 0.01 (Mann Whitney U Test)
Percent of starting body weight.
Percent of living fetuses weighting <3-3 g (rats) or 0.9 g (mice).
cAgnathia, brachimelia, missing tall.
The rats were sacrificed on day 21 of pregnancy, the mice on day 18.
^hymus hypolasia also looked for.
Including poorly ossified sternebrae, bipartite vertebra centra, and shortened 13th ribs.
°Fissura sterni and agnathia also looked for.
-------
Table 14-8. Teratogenic Effects of Exposure to Toluene, Benzene, and a Combination
of Toluene and Benzene in CFY Rats (Tatrai et al., 1980)
Inhalation on days
7-14 of pregnancy
24 h/d
Toluene
Air 266 ppm,
(1000mg/nr)
Benzene Toluene/Benzene Significance
125 ppm 266 ppm + 125 ppm of
(400 mg/m3) (1000 mgZ400 mg) Interaction
m
Number of females
treated
died
non pregnant
total resorption
Number of liters
Mean implantation/ dam
Maternal weight gain
in % of starting body
weight
Relative liver weight
(*)
Mean placental weight
(g)
Number of fetuses
live
dead
resorbed
Mean fetal weight (g)
Weight retarded
21
1
21
14.0
68.82
+2.40
4.25
+0.08
0.58
+0.006
294
280
14
3.94
+0.02
2.8
20
2
18
14.4
65.82
+2.13
4.37*
+0.07
0.60
+0.006
259
239
20
3.91
+0.02
3.3
20
3
17
14.6
46.74***
+2.69
4.67*
+0.12
0.48***
+0.006
248
236
2
10
3.16***
+0.03
57.6**
20
1
19
13.8
53.94***
+ 1.84
4.10
+0.09
0.54»»»
+0.004
262
234
28
3.79**
+0.02
9.8*
—
p < 0.05
p < 0.01
p < 0.05
p < 0 . 00 1
fetuses in % of living
fetuses
External malformations —
Fetal loss/total
implantation sites (?)
No. Alizarine-stained
fetuses
Skeletal retarded
fetuses in % of
Alizarine-stained
fetuses
4.7
142
13
7.7
121
31*
4.8
122
77***
10.7*
118
39 >•
14-20
-------
Table 14-8. Teratogenic Effects of Exposure to Toluene, Benzene, and a Combination
of Toluene and Benzene in CFY Rats (Tatrai e_t al., 1980) (Cont.)
Inhalation on days
7-14 of pregnancy
24 h/d
Skeletal anomalies
sternum misaligned
asymmetric vertebra
extra ribs
Skeletal malformations
No. fetuses dissected
Internal malformations
polycystic lungs
pyelectasia
dystopia renis
vesica giganta
microphthalmia
anophthalmia
hydrocephalus
internus
Air
4
1
1
—
138
1
2
—
—
—
—
——
Toluene
266 ppm
(1000mg/m3)
4
—
7+
—
118
—
5
1
3
—
—
— —
Benzene
125 ppm
(400 mg/nH)
5
3
1
—
114
—
—
—
1
—
2
3
Toluene/Benzene Significance
266 ppm + 125 ppm of
(1000 rag/400 mg) Interaction
nr
1
1
19**
—
116
—
1
—
1
1
—
— —
= p<0.1;
* =
0.05; ** = p <0.01 ; »»* = p < 0.001 ; + = SEM
14-21
-------
to toluene alone. Maternal loss, maternal weight gain, number of litters, mean
implantation/dam, placental weight, fetal loss, and fetal weight loss were not
significantly affected by the toluene exposures. Exposure to 125 ppm benzene did
cause decreases in maternal weight gain, placental weight and fetal weight, but
these effects appeared to be inhibited by concurrent exposure to 266 ppm toluene.
Further, it was reported that post-implantation fetal loss (the number of dead
and resorbed fetuses relative to the number of total implantation sites in
percent) was significantly increased in the group exposed to benzene in combina-
tion with toluene; fetal loss was not, as indicated earlier, affected by exposure
to the toluene (or benzene) alone.
In a third inhalation study, Litton Bionetics, Inc. (1978b) reported no
evidence of teratogenicity in the 20-day old fetuses of Charles River rats that
were exposed to 100 ppm or 400 ppm toluene vapor for 6 hours/day on days 6-15 of
gestation. Histological examinations revealed no unusual incidence of visceral
or skeletal abnormalities (Table 14-9); unusual skeletal variations were
observed in a small but comparable number of fetuses from both the exposed and
control groups, but these changes were in most cases related to retarded bone
ossification and were not considered to be malformations as such. It was also
noted that there were no maternal deaths during this study, and that the sex
ratio of the offspring did not differ significantly between the treted and
control groups.
In a brief abstract, Roche and Hine (1968) noted that toluene was not
teratogenic to either the rat fetus or the chick embryo. Parameters evaluated
included body weight, bone length, and gross abnormalities, but no dose or
exposure information or other quantitative data were provided.
Elovaara ^t jal. (1979b) injected toluene into the air space of developing
chicken eggs at doses of 5, 25, 50, and 100 umol/egg on the 2nd and 6th days of
14-22
-------
Table 14-9. Teratogenicity and Reproductive Performance Evaluation in
Rats Exposed to Toluene (Litton Bionetics, Inc., 1978b)
0
Dose (ppm)
100
400
Pregnancy ratio
(Pregnant/Bred)
No. pregnant rats that died
Live litters
Implantation sites
(Left Horn/Right Horn)
Resorptions
Litters with resorptions
Dead fetuses
Litters with dead fetuses
Live fetuses/implantation site
Mean live litter size (fetuses)
Average fetal weight (g)
Number of fetuses examine for soft
tissue (visceral) changes
Number of fetuses examined for
skeletal changes0
Number of fetuses with normal
skeletal examinations
Fetuses with commonly encountered
skeletal changes '
Fetuses with,,unusual skeletal
variations6'
26/27
0
26
152/194
26
13
0
0
320/346
12
3.6
108(51/57)
212
139
67(20)
6(4)
27/27
0
27
181/177
28
- 20
1
1
329/358
12
3.5
105(47/58)
221
150
62(20)
9(4)
27/27
0
26
179/190
41s
17
0
0
328/369
12
3.8
104(51/53)
224
158
58(20)
8(6)
The increase in total resorptions at this dose was attributed to the total
resorption of the litter of one particular female.
Numbers of male/females examined in parentheses.
cFour specimens from one litter were not examined (missing).
A qualitative examination of the observations recorded for the fetuses
indicates that bilateral ribs, unilateral ribs, and reduced ossification of
various bones were the most frequently encountered changes.
lumber of litters in parenthesis.
f
generally
These were
ossification.
cases of more severe and extensive retarded
14-23
-------
incubation. Survival incidence after 14 days of incubation appeared to be
influenced only after injection of toluene on day 6 at 100 umol/egg; the "approx-
imate LD50" for toluene was judged to be in excess of 100 umol/egg. Macroscopic
examination on day 14 indicated that only 3 of 46 of the chick embryos treated
with 5-100 umol/egg of toluene were malformed; 1 displayed profound edema and 3
had skeletal abnormalities (muscul©skeletal defects of the lower extremities,
but not wings).
McLaughlin _et _al. (1964) injected toluene at dose levels of 4.3, 8.7, and
17.4 mg into the yolk sac of fresh fertile chicken eggs before incubation.
Following incubation, the percentages of hatch at the three doses were, respec-
tively, 85$, 25$, and 0$. Teratogenic effects were not observed in either the
eggs that failed to hatch or in the chicks that did hatch.
14.3.2 Effects in Humans
Holmberg (1979) gathered information on exposure to noxious agents during
the pregnancies of 120 mothers of children with congenital CNS defects and their
matched-pair controls. The matched-control mother is the mother whose delivery
immediately preceded that of the case mother in the same Finnish maternity
welfare district. Results showed that 14 of the 120 case mothers had been
exposed more often than control mothers (3/120) to organic solvents during the
first trimester of pregnancy. Among the 14 exposed mothers, 2 had been exposed
to toluene. One of the toluene-exposed mothers (age 18) had reportedly been
exposed in the metal products manufacturing industry (no other details of expo-
sure given), and gave birth to a child that died after 2 hours and showed
internal congenital hydrocephaly and agenesis of the corpus callosum upon
autopsy; other findings included pulmonary hypoplasia and a diaphragmatic
hernia. The other mother was exposed to toluene concomitantly with other sol-
vents (xylene, white spirit, methyl ethyl ketone) during rubber products
14-24
-------
manufacturing; her child was hydranencephalic and died 24 days after birth. It
was noted that in this case parental age (maternal, 42 years; paternal, 44 years)
and a previous child with brain injury (born 20 years previously, died at age 4)
were more likely than the recent exposure to have predisposed the more recent
child to the defect.
Toutant and Lippman (1979) described the birth of a child with "nearly
classic" fetal alcohol syndrome to a 20-year-old primigravida whose major addic-
tion was to solvents (reportedly, primarily toluene). This woman had a 14-year
history of daily heavy solvent abuse (no details provided) and a 3-year history
of alcohol intake of about a six-pack of beer weekly. On admission, she
exhibited signs compatabile with severe solvent and/or alcohol abuse (ataxia,
resting and intention tremors, mild diffuse sensory deficits, short-term memory
loss, and poor intellectual functioning). The child was born at term, was small
(10th percentile in weight, 5th percentile in head size), and exhibited abnormal
features that included microcephaly, a flat nasal bridge, hypoplastic mandible,
short palpebral fissures, mildly low-set ears, pronounced sacral dimple, sloping
forehead, and uncoordinated arm movements. It was noted that although solvent
abuse rather than alcohol predominated in this mother's addiction pattern, the
case seemed no different from reports of fetal alcohol syndrome.
14.4 SUMMARY
CUT (1980) concluded that exposure to 30, 100, or 300 ppm toluene for
24 months did not produce an increased incidence of neoplastic, proliferative,
imflammatory, or degenerative lesions in mice relative to unexposed controls.
Other studies indicate that toluene is not carcinogenic when applied topically to
the shaved skin of mice (Poel, 1973; Linsky and Garcia, 1972; Coombs et al.,
1973; Doak et al., 1976), and that it does not promote the development of
14-25
-------
epidermal tumors following initiation with DM3A (Frei and Kingsley, 1968; Frei
and Stephens, 1968).
Toluene has yielded negative results in a battery of microbial, mammalian
cell, and whole organism test systems. The microbial assays conducted include
differential toxicity testing with wild-type and DNA repair-deficient strains of
J2. coli and S. typhimurium (Fluck e_t jd., 1976; Mortelmans and Riccio, 1980),
reverse mutation testing in various strains of S. typhimurium, E. coli WP2, and
S;. cerevisiae D7 (Litton Bionetics, Inc., 19?8a; Mortelmans and Riccio, 1980;
Nestman _et _al., 1980), and mitotic gene conversion and crossing-over evaluation
in^. cerevisiae D4 and D7 (Litton Bionetics, Inc.", 19?8a; Mortelmans and Riccio,
1980). Toluene also failed to induce specific locus forward mutation in the
L5178Y Thymidine Kinase mouse lymphoma cell assay (Litton Bionetics, Inc.,
1978a), and was negative in the micronucleus test (Kirkhart, 1980). Sister-
chromatid exchange (SCE) frequencies were not altered in Chinese hamster ovary
cells (Evans and Mitchell, 1980) or in human lymphocytes (Gerner-Smidt and
Friedrich, 1978) cultured with toluene, or in the peripheral lymphocytes
cultured from workers with a history of chronic exposure to toluene (Funes-
Cravioto _et al., 1977; Maki-Paakkanen .et al., 1980).
In the Russian literature, chromosome aberrations were reported in the bone
marrow cells of rats exposed subcutaneously (Dobrokhotov, 1972; Lyapkalo, 1973)
and via inhalation (Dobrokhotov and Einkeev, 1977) to toluene. These findings
were not corroborated, however, in a Litton Bionetics, Inc. (1978b) study in rats
following intraperitoneal injection, in cultured human lymphocytes exposed to
toluene i.n vitro (Gerner-Smidt and Friedrich, 1978), or in lymphocytes from
workers chronically exposed to toluene (Forni £t al., 1971; Maki-Paakkanen
e_t jd., 1980). Funes-Cravioto ^_t al_. (1977) did report an excess of aberrations
in the lymphocytes from 14 printers exposed to 100-200 ppm toluene for
14-26
-------
1-16 years, but it is probably that part of the exposure was to benzene-
contaminated toluene.
Toluene was reported in a recent abstract from NIEHS to induce cleft palates
at a level of 1.0 ml/kg following oral exposure to mice on days 6-15 of gestation
(Nawrot and Staples, 1979). The effect reportedly did not appear to be due
merely to a general retardation in growth rate. Three other studies concluded
that toluene is not teratogenic in mice (Hudak and Ungvary, 1978) or rats (Hudak
and Ungvary, 1978; Litton Bionetics, Inc., 1978b; Tatrai £t al., 1980) following
inhalation exposure. Embryotoxic effects (increased incidence of skeletal
anomalies and signs of retarded skeletal develo'pment, low fetal weights) and
increased maternal mortality were noted, however, in some of the rats and mice
exposed via inhalation. Injection of toluene into the yolk sac (McLaughlin
j5t ^1., 1964) or air space (Elovaara ^t al., 1979b) of chicken eggs before
incubation or during development, respectively, did not result in teratogenic
effects.
14-27
-------
15. SYNERGISMS AND ANTAGONISMS AT THE PHYSIOLOGICAL LEVEL
15.1 Benzene and Toluene
Animal studies have shown that benzene and toluene may be metabolized by
similar enzyme systems in parenchymal cells of the liver. In the studies of
Pawar and Mungikar (1975), the activities of hepatic aminopyrine N-demethylase,
NADPH-linked peroxidation, and ascorbate-induced lipid peroxidation were
reduced, while acetanilide hydroxylase was increased by either benzene pretreat-
ment or toluene pretreatment in male rats. Induction of aminopyrine N-
demethylase and components of the electron transport system was seen when the
animals were given phenobarbital (Pawar and Mungikar, 1975; Mungikar and Pawar,
1967a, 1967b). When phenobarbital was coadministered with benzene or toluene,
the changes in the activity of these enzymes produced by single administration of
the xenobiotics were attenuated (Pawar and Mungikar, 1975). That induction of
hepatic enzymes by phenobarbital affects metabolism of toluene is indicated by
the reduction of toluene toxicity (decreased narcosis) in female rats or male
mice given phenobarbital prior to intraperitoneal injection of toluene (Ikeda
and Qhtsuji, 1971; Koga and Ohmiya, 1978) and the accelerated excretion of
toluene metabolites from female rats as described in Sections 12.3 and 12.4
(Ikeda and Ohtsuji, 1971).
The following studies indicate that toluene has the potential for altering
the bioactivity of benzene when given in sufficiently large quantities. When
benzene was given in combination with toluene, the conversion of benzene to its
metabolites (phenols) was suppressed in rats (Ikeda jst al., 1972) and in mice
(Andrews ^t _al., 1977). Ikeda _et _al. (1972) administered a mixture of benzene
and toluene (equivalent to 110 mg benzene/kg and 430 mg toluene/kg) intraperi-
toneally to female rats and observed a reduced excretion of total phenols. When
a mixture of toluene and benzene (110 mg toluene/kg and 440 mg benzene/kg) was
15-'
-------
administered, hippuric acid excretion was reduced up to 4 hours after injection.
Induction of hepatic micro somal enzymes by phenobarbital prior to administra-
tion of the mixture alleviated the suppression.
Andrews _et al. (1977) coadministered 440 mg/kg or 880 mg/kg benzene and
1720 mg/kg toluene intraperitoneally to mice and found a significant reduction
in urinary excretion of benzene metabolites and a compensatory increase of pul-
monary excretion of unmetabolized benzene. When toluene and benzene were coad-
ministered by subcutaneous injection, toluene did'not significantly change the
total amount of benzene found in fat, liver, spleen, blood, or bone marrow, but
it did reduce significantly the accumulation of- metabolites in these tissues.
Coadministration of toluene and benzene also counteracted benzene-induced reduc-
59
tion of red cell Fe uptake in developing erythrocytes, suggesting that the
myelotoxicity of benzene might be attenuated by toluene-inhibition of benzene
metabolism in the bone marrow. In an in vitro study of a liver microsome
preparation, Andrews and coworkers (1977) determined that toluene is a competi-
tive inhibitor of benzene metabolism.
In the studies of Ikeda _et al. (1972) and Andrews .et al. (1977), however,
benzene and toluene were given intraperitoneally in large amounts. Sato and
Nakajima (1979b) used doses in the range of 24.2 to 390.6 mg/kg of benzene and
28.6 to U60.8 mg/kg of toluene to assess concentrations which might be found in
the workplace. They found that when benzene was given to rats in the range of
24.2 to 97.7 mg/kg, there was no significant difference in the rate of disap-
pearance of benzene from the blood whether the benzene was administered singly or
in combination with an equimolar amount of toluene. At a dose of 390.6 mg/kg
benzene, an equimolar dose of toluene delayed the disappearance of benzene from
blood, and the excretion of phenol was reduced. A dose-dependent inhibition of
the metabolism of benzene by toluene was found. In a study of human exposure,
15-2
-------
inhalation of a mixture of 25 ppn> benzene and 100 ppm toluene for 2 hours did not
exert any influence on the disappearance rate of benzene and toluene in either
blood or end-tidal (alveolar) air as compared to inhalation of either solvent
singly. Desaturation curves (concentration versus time) for blood or end-tidal
air obtained for each solvent after inhalation of the specified mixture were
virtually suprimposable on desaturation curves obtained after inhalation of the
same solvent (25 ppm benzene or 100 ppm toluene) by itself. These results
indicate that in the range of threshold limit value "the pharmacokinetic
processes ... of absorption, distribution, excretion, and metabolism of either
benzene or toluene are not influenced by simultaneous exposure to the other"
(Sato and Nakajima, 1979b). The data for the single-solvent exposures had been
published previously (Sata _et ^1., 1974b); details of the experiment with toluene
were discussed in Section 12.4.
15.2 XYLENES AND TOLUENE
When 0.1 ml/kg or 0.2 ml/kg toluene was coadministered with similar doses
of jn-xylene intraperitoneally into male rats, the amounts of hippuric and
m-methylhippuric acid excreted in urine over a period of 24 hours were not
different from the amount of metabolites formed by single injection of toluene or
ra-xylene. The velocity of excretion of metabolites in the simultaneously
injected group was slightly delayed in comparison with that in singly injected
groups. Thus, simultaneous administration of the compounds does not signifi-
cantly interfere with the metabolism of either compound (Ogata and Fujii, 1979).
To study the excretion kinetic interactions between toluene and xylene,
Riihimaki (1979) determined the conjugation and urinary excretion of metabolites
of toluene and jn-xylene, benzoic acid and methylbenzoic acid, respectively, in
vivo in 1 man. Forty-one millimoles benzoic acid or 7.4 mmol methylbenzoic acid
was ingested singly or in combination by 1 adult human male. In the 25 to
1.5-3
-------
30 hours that urine was collected after ingestion, the total recovery of the
ingested compounds with the exception of 1 sample (dose excreted in that case:
84%) indicated that all excretion took place via the kidneys. The combined
intake of methylbenzoic acid and benzoic acid did not significantly affect conju-
gation or excretion of either metabolite. This study indicates that during
simultaneous exposures to toluene and m-xylene, even at a relatively high level
of occupational exposure, conjugation and excretion of metabolites are not
likely to be rate-limiting steps except under conditions of limited availability
of glycine.
15.3 TOLUENE AND OTHER SOLVENTS
Simultaneous intraperitoneal injection of 1.18 g/kg toluene with 0.91 g/kg
ji-hexane into female rats did not affect the concentrations of ji-hexane in the
blood nor was excretion of hippuric acid affected by coadministraton of ji-hexane
(Suzuki et al., 1974).
Coadministration of ethanol by ingestion and of toluene by inhalation
(4000 mg toluene/ra , 6 hours daily, 5 days a week for 4 weeks) into rats did not
change the electrocardiogram, hematocrit values, or histological and histoc-
hemical structure of the heart. Toluene increased vascular resistance of the
myocardium and reduced cerebral blood flow, while alcohol ingestion reduced
arterial blood pressure, the cardiac index, and blood flow to the myocardium,
kidney, skin, and carcass. Myocardial and cutaneous vascular resistance, as well
as cerebral blood flow, increased after alcohol ingestion. It was concluded that
combined exposure to the two substances produced additive effects on myocardial
vascular resistance (Morvai and Ungvary, 1979). During subchronic exposure of
rats to toluene and ethanol, there is a potentiation of microsomal and mito-
chondrial changes in the liver (Hudak j_t _al., 1978).
15-4
-------
In their study of joint toxic action, Smyth et al. (1969) suggested that
perchloroethylene is capable of enhancing the toxicity of toluene administered
orally in rats. Withey and Hall (1975) observed that administration by intuba-
tion into rats of trichloroethylene and toluene in combinations of mixtures at 5
different dose levels revealed a departure from an additive model. They con-
cluded that the effect of coadministration of the'solvents could not be described
in terms of synergism or potentiation until further studies were made.
Ikeda (197*0 observed that coadministration of trichloroethylene and
toluene (730 mg/kg and 430 mg/kg, respectively) by the intraperitoneal route
into rats reduced the amounts of metabolites of both solvents compared with
amounts excreted after administration of either solvent alone.
15-5
-------
16. ECOSYSTEM CONSIDERATIONS
16.1 EFFECTS ON VEGETATION
16.1.1 Introduction
Toluene volatilizes rapidly from solutions (Mackay and Wolkoff, 1973).
Most studies investigating the phototoxicity of toluene have been with algae. Of
these studies, only one (Dunstan et al. , 1973) was done under conditions that
maintained a nearly constant concentration of toluene in the culture medium
throughout the experiment. Other studies were done with culture vessels capped
with metal caps or with cotton plugs, allowing ' the toluene to volatilize and
escape from the exposure solutions. Even though steady-state concentrations are
lacking, these studies do approximate situations in the environment where a point
source of toluene exists to a body of water. The discussion of these studies
will, therefore, be under the headings of "closed" and "open" experimental
systems.
16.1.2 Effects of Toluene on Plants
16.1.2.1 Algae
16.1.2.1.1 Closed System Studies
Dunstan et al. (1975) exposed 4 marine algal species to toluene concen-
trations ranging from 1 to 10 ug/1. Axenic algal cultures were inoculated at
18°C and grown with a 12-hour light/ dark cycle under cool-white fluorescent light
o
(4000 yW/cm , 380-700 nm) in filtered enriched seawater. To minimize loss of
toluene by vaporization, the 125-ml Erlenmeyer flasks were made airtight with
rubber stoppers. Experiments were never run beyond a cell density at which C0?-
limitations might limit growth. The four species used were the diatom,
Skeletonema costatum; the dinof lagellate , Amphidinium carterae; the cocolitho-
phorid, Cricosphaera carterae; and the green flagellate, Dunaliella tertiolecta.
16-1
-------
To illustrate the difficulty of establishing absolute concentration when
working with toluene, Dunstan et al. (1975) observed the toluene concentrations
at three intervals in stoppered flasks (Table 16-1). Eighty-four percent of the
theoretial initial concentration was lost at the beginning of the experiment
during the handling and dispensing of the toluene into culture flasks, even when
the toluene was rapidly dispensed under sterile conditions.
Figure 16-1 shows how toluene can both stimulate and inhibit algal growth
depending on the species and the concentration of toluene. The dinoflagellate,
Amphidinium carterae was inhibited at all concentrations of toluene (1 to
10 ug/1) from 20-50%. The other three species, however, were stimulated by 1 to
ii
10 ug/1, but higher concentrations of toluene either had no effect (Dunaliella
tertiolecta) or became inhibitory (Skeletonema costaturn and Cricosphaera
carterae). This work indicated that one of the most significant environmental
effects was in the short-term selection of certain phytoplanktonic species by the
growth stimulation brought about by low levels of toluene. Dunstan _et _al. (1975)
concluded that the differential growth of phytoplanktonic species within the
phytoplankton population ultimately determines the community structure, its
succession, and its trophic relationship.
Potera (1975) evaluated the effect of toluene on saltwater phytoplankton
dominated by Chlorella sp. using Warburg manometry. Toluene inhibited photo-
synthesis 29$ at 34 mg/1 and 35% at 342 mg/1 (at 20°C). Respiration (at 20°C)
was inhibited 62$ at 34 mg/1 and 16$ at 342 mg/1.
16.1.2.1.2 Open Studies
Illustrative of the "open" type of experiment is that of Kauss and
Hutchinson (1975). The freshwater alga, Chlorella vulgaris, was exposed to
toluene for 10 days in 125-ml cotton-plugged Erlenmeyer flasks. Each flask was
16-2
-------
Table 16-1. Concentrations of Toluene in Stoppered Flasks
(Dunstan et al., 1975) -
Time of Measurement Percent of Theoretical
Concentration
Theoretical initial concentration 100
Measured initial concentration " 16
Concentration after 3 days of growth
Stoppered flask 14
Cotton-plugged flask 1
16-3
-------
150-.
150-1
UJ 2
£
_i Q.
UJ —
CC -I
1 2
I— CC
°
50-
CONCENTRATION (pg/C)
150-,
U4 2
< £
-J a.
UJ —
CC _l
10
50-
150-,
Skeletonema costatum
105
CONCENTRATION
Dunaliella tertiolecta
103 104
CONCENTRATION (//g/C)
10s
Cricosphaera carterae
102 103 104
CONCENTRATION (/ig/£)
10s
Figure 16-1.
Phytoplankton Growth in Various Concentrations of Toluene (Organisms were grown in stoppered
flasks. Growth, measured by cell numbers and in vivo chlorophyll, was determined on the 2nd
and 3rd days of logarithmic growth. Concentrations of low molecular weight hydrocarbons are
in theoretical values.) (Dunstan et al., 1975)
-------
agitated to resuspend the cells daily. The concentrations listed in Figure 16-2
are nominal initial concentrations. In this open experiment, toluene was less
toxic to the alga because the toluene concentration diminished by volatilization
during the experiments. Comparison with controls revealed that a lag phase that
lasted for 1 day existed between inoculation and commencement of growth for 50
and 100 mg/1. Recovery was less rapid with 250 rag/1. At concentrations
approaching toluene saturation (i.e., 505 mg/1), toluene was lethal to the
cells.
Table 16-2 summarizes the toxic effects of toluene on algae. In assessing
the toxicity of toluene to algae, both the inherent toxicity of toluene and the
exposure time need to be considered. The no-effect concentration for most algal
species studied appears to be at the 10 mg/1 level. The evaporation rate from
solution (fresh or saltwater), however, rapidly diminishes the exposure concen-
tration of toluene (Dunstan et al., 1975). The toxicity of toluene is more
closely approximated by levels of 100 mg/1 in "open" systems, as shown by Kauss
and Hutchinson (1975).
16.1.2.2 Effects on Higher Plants
Currier (1951) exposed barley, tomatoes, and carrots to toluene vapor. Air
at a flow rate of 11.5 I/minute passed through a small vaporizing chamber con-
taining the toluene and into the top of a bell jar containing the plants. The
concentration of toluene in the vapor chamber was varied by changing the tempera-
ture of the toluene. The concentration of vapor in the air was determined by
measuring the amount of toluene evaporated per unit of time. Three tomatoes,
20 carrots, and 12 barley seedlings were tested 32, 32, and 14 days, respec-
tively, after planting. Plants were exposed in the gas chamber for 1/4, 1/2, 1,
and 2 hours. The kind and extent of injury were recorded after 1 month to allow
for a recovery period. Temperature of the plants was held at 25°C.
16-5
-------
(M
§
«M
CD
150
100
I
o
QC
m 10
§
LU
O
T
•* CONTROL
•o 25 ppm
A- -A 50 ppm
D D 100ppm
A A 250 ppm
*-
* 505 ppm
0
2
_L
468
TIME (DAYS)
10
12
Figure 16-2. Growth of Chlorella vulgaris in Medium Containing
Toluene (Data plotted are the average of three
replicates. Lines of best fit were determined using
regression coefficients. Numbers represent initial
hydrocarbon concentration on a parts per million basis.
The arrow on the ordinate indicates starting cell
concentration.) (Kauss and Hutchinson, 1975)
16-6
-------
Table 16-2. Toxic Effects of Toluene to Algae
Species
Concentration
Effect
Reference
FRESHWATER
Chlorella vulgaris 245 mg/1
Chlorella vulgaris 250 mg/1
Microcystis aeruginosa 105 mg/1
Soenedesmus quadricauda >400 mg/1
24-h EC50
(cell number)
96-h no-effect cone.
(cell number)
8-d no-effect cone.
(chlorophyll a)
8-d no-efrect cone.
(chlorophyll a)
Kauss and Hutchinson,
1975
Kauss and Hutchinson,
1975
Bringmann and Kuhn,
1978
Bringmann and Kuhn,
1978
SALTWATER
Amphidinium carterae
Skeletonema costaturn
Ectocarpus sp.
Enteromorpha sp.
<0.001 mg/1
Dunaliella tertiolecta 10 mg/1
10 mg/1
Cricosphaera carterae 10 mg/1
1730 mg/1
1730 mg/1
2- to 3-d no-effect
cone, (cell number
and chlorophyll)
2- to 3-d no-effect
cone, (cell number
and chlorophyll)
2- to 3-d no-effect
cone, (cell number
and chlorophyll)
2- to 3-d no-effect
cone, (cell number
and chlorophyll)
inhibits asexual
spore germination
inhibits asexual
spore germination
Dunstan et al.,
1975
Dunstan et al.,
1975
Dunstan et al.,
1975
Dunstan et al.,
1975
Skinner, 1972
Skinner, 1972
Abbreviations: h = hour; cone. = concentration; d = day.
16-7
-------
Results showed that toxic effects of toluene vapor were influenced by expo-
sure period and dosage (Table 16-3). Toluene was observed to be toxic at
concentrations of 6.4-12.0 mg/1 after 15 minutes of exposure (Currier, 1951).
Fifteen minutes of exposure at 12 mg/1 toluene produced a 50%, 0%, and 60$ injury
to tomato, carrot, and barley, respectively. .The effects of the exposures on
flower and fruit development were not determined. For lethality to occur at
12.0 mg/1, barley required 1 hour, tomato 2 hours, and carrot over 2 hours. The
toxicity appeared to. vary markedly within a narrow limit. By lowering the
concentration of toluene from 12.0 mg/1 to 6.4 mg/1, the percentage of injury to
barley after a 2-hour exposure was reduced from 100$ (lethal) to 15$. At
24.1 mg/1, toluene was only twice as toxic to barley seedlings as at 12.0 mg/1
after a 30-minute exposure.
Toluene entered the plant rapidly through the cuticle and stomata. Symptoms
of injury included a darkening of the tips of the youngest leaves, presumably as
a result of leakage of sap into the cellular spaces (Currier, 1951). This
darkening spread to the older leaves. There was a loss of turgor, with draping
stems and leaves. In bright sunlight, the chlorophyll was destroyed.
Toluene is classified as a contact poison that quickly kills the plant
tissue with which it comes in contact (Currier, 1951). This material is not
accumulated in plants nor is it translocated. The mechanism of toxicity involves
disorganization of the outer membrane of the cell due to solvent action on the
lipoid constituents, resulting in disruption of photosynthesis, respiration, and
turgor pressure.
16.2 BIOCONCENTRATION, BIG-ACCUMULATION, AND BIOMAGNIFICATION POTENTIAL
Limited information is available concerning toluene's potential for accumu-
lating in aquatic organisms and aquatic food chains. Possible pathways of
toluene uptake are directly from water (bioconcentration) and from both water and
16-8
-------
16-3. Toxic Effects of Toluene Vapor on Carrots, Tomatoes, and Barley
(Currier, 1951)
o
Percent Injury
Material
Concentration
Exposure Time (h)
1/4
1/2
1
2
Tomato
Carrot
Barley
Barley
Barley
12.0 mg/1
12.0 mg/1
12.0 mg/1
6.4 mg/1
24.1 mg/1
50
0
60
0
ND
60
50
50
25
100
75
75
98
15
100
100
75
100
15
ND
Abbreviations: h = hour; ND = not determined.
aO% = no effect; 100/S = lethal 1 month after exposure.
-------
food (bicaecumulation). Biomagnification occurs if the concentration of a com-
pound in an organism increases with its trophic level as a result of passage
through food chains.
Nunes and Benville (1979) studied the uptake and depuration of toluene and
other monocyclic aromatic components of the water-soluble fraction (WSF) of
Alaskan Cook Inlet crude oil in Manila clams (Tapes semidecussata). Clams were
exposed for 8 days to a constant WSF concentration under continuous-flow expo-
sure conditions. The toluene concentration in water was measured daily. The
toluene concentration in a pooled sample of 10 clams was measured at 2, 4, 6, and
8 days. At the end of the exposure period, remaining clams were transferred to
clean-flowing seawater and pooled tissue samples were analyzed for toluene after
1, 7, and 12 days of depuration. The data are provided in the following tabula-
tion:
Toluene Concentration (ppm)
Exposure
Depuration
Days
1
2
3
4
5
6
7
8
1
7
Water
1.2
1.3
1.7
1.4
1.2
0.9
1.0
1.1
Tissue
2.3
2.2
0.87
2.0
3.30
0.80
1.10
The mean water concentration during the uptake period was 1.2 ppm toluene.
Tissue concentrations reached a maximum by 2 days of exposure and remained rela-
tively constant except for a temporary decline on day 6. The average tissue
concentration during the exposure period was 1.5 ppm. The calculated bioconcen
16-10
-------
tration factor (BCF) is 1.25 (which is equivalent to 1.5 ppm in tissue/1.2 ppm in
water). The depuration study showed that toluene was lost rapidly during the
first week of depuration, but that a significant concentration of toluene
remained in the clams by 2 weeks after beginning depuration.
14
Hansen e_t _al. (1978) investigated the uptake and depuration of C-toluene
by blue mussels (Mytilus edulis). Groups of mussels were exposed under static
conditions to four concentrations of C-toluene for up to 8 hours, followed by
in
exposure to clean recirculating seawater for up to 192 hours. The C-toluene
concentration in water and tissue (pooled sample from 4 mussels) was measured by
liquid scintillation counting at 1, 2, 4, and 8 hours after beginning the uptake
phase and periodically in tissue during the depuration phase.
14
The C-toluene concentration in tissue exceeded the water concentration by
1 hour at all exposure concentrations except the highest (40 ul/kg = ppm), which
was toxic as shown by closure of the mussels at this concentration (Hansen
et jal., 1978). Equilibrium was reached by 4 hours in all groups. The BCF values
at 8 hours, expressed as the tissue concentration divided by the mean water
concentration, were as follows:
Water concentration
(ul/kg) BCF
0.05 3.8
0.4 5.7
4.0 3-6
4.0 3.6
The BCF values, which averaged 4.2, seemed to be independent of the exposure
concentration, indicating that accumulation was proportional to the level in
water (Hansen e^t _al., 1978). More than half of the accumulated C-toluene was
eliminated by 1 hour after the depuration phase began at all exposure concentra-
14
tions. The depuration time by which no C-toluene was detectable in tissue was
14
1 hour in the mussels exposed to 0.05 ul C-toluene/kg; 4 hours for those
16.-11
-------
exposed to 0.4 ul/kg, 120 hours for those exposed to 4 yl/kg, and 192 hours for
the animals exposed to 40 ul/kg.
Lee _et al. (1972) reported that the same species of mussel (Mytilus edulis)
took up 3 to 10 ug of C-toluene per mussel (average dry weight tissue = 0.3 g)
during static exposure for an unspecified period of time to 0.1 to 0.5 mg/1.
Using tissue toluene concentrations of 10 to 33 Ug/g> the BCF is calculated to
have been between 66 and 100. Because these values are based on dry tissue
weights rather than wet weight, they are considerably higher than those reported
by Nunes and Benville (1979) and Hansen ^t jd. (1978).
Berry (1980) investigated the uptake of C-toluene by bluegill sunfish
(Lepomis macrochirus) and crayfish (Orconectes rusticus). The exposure solu-
14
tions were prepared by adding 1 ml of C-toluene to 100 1 of water for the fish
14
experiment and by adding 1 ml C-toluene to 10 1 of water for the crayfish
experiment. A group of 40 animals was added after thorough mixing of the solu-
tions. Duplicate water samples and 2 to 4 animals were taken at 0, 0.5, 1, 2, 4,
8, 12, 16, 20, 24, and 48 hours after beginning exposure. The C-toluene
concentration, expressed as nanograms per milligram (= ppm), was determined in
water and in 7 (crayfish) or 9 (fish) tissues or organs by liquid scintillation
counting. The BCF for each tissue was also calculated. Analysis of water
samples showed that the toluene concentration in water decreased at a much
greater rate in the crayfish experiment than in the bluegill experiment (89$
versus 51$ loss by 48 hours). The maximum BCF of bluegill tissues ranged from
about 3 for brain to 45 for spleen. Fish muscle tissue was not analyzed. The
maximum BCF for most fish tissues was reached by 8 hours. The maximum BCF of
crayfish tissues ranged from about 8 for muscle to 140 for hepatopancreas. The
BCF values increased throughout the 48-hour exposure period for all tissues
except testes and muscle. These results indicate that toluene is accumulated
16-12
-------
above the water concentration by many tissues in these two species. The BCF of 8
in the edible portion (muscle) of crayfish is considered to be a minimum value
because of the rapidly decreasing toluene exposure concentration during this
experiment.
Berry _et al. (1978) also measured the uptake of %-toluene by fed and unfed
mosquito (Aedes aegypti) larvae and the uptake of H-toluene by fed larvae in the
presence or absence of benzene. The larvae were exposed to an initial concentra-
tion of 0.5 ml ^-toluene/1 water. Duplicate water samples and 2 to 5 larvae
were taken at 1, 2, 4, 8, 12, 16, 20, and 24 hours and counted individually by
liquid scintillation counting. Maximum -^-toluene counts per minute (cpm) were
equal in fed and unfed larvae, but were reached more quickly (1 hour versus
4 hours) by the fed animals. The •%-toluene counts-per-minute values in larvae,
expressed as the percentage of initial water counts, were greater during the
first 4 hours in the benzene and toluene mixture than in the solution containing
toluene alone. BCF values cannot be calculated because the authors expresssed
•%-toluene uptake as counts per minute per larvae rather than counts per minute
per gram. The weight of the larvae was not provided. Interpretation was also
complicated by rapid loss of H-toluene (half-time about 4 hours) during the
uptake period. It is likely, however, that uptake by ingestion of toluene
adsorbed to food particles can be a significant route of accumulation in aquatic
organisms.
Ogate and Miyake (1973) identified toluene as the cause of offensive odor in
the flesh of grey mullet (Mugil Japanicus) taken from a harbor receiving efflu-
ents from refineries and petrochemical industries. Toluene was identified in
sea water and fish tissue by gas chromatography, infrared (IE) and ultraviolet
(UV) absorption, and mass spectrometry. The toluene concentration in most fish
was not quantified; however, the flesh of 1 mullet with an offensive odor con
16-13
-------
11.2
2.6
5.1
30.8
12.4
9.0
2.5
5.2
2.5
0.70
0.16
0.32
1.91
0.77
0.56
0.16
0.32
0.16
tained 5 ppm toluene. Additional experiments showed that toluene was accumu-
lated by caged eels kept for 10 days in several locations in the harbor to an
average of 2.4 times the water concentration. These eels had the same offensive
odor as mullet collected from the harbor. In another experiment, 4 eels were
exposed in seawater to which a mixed solution of benzene, toluene, and xylenes
was added daily for 5 days. The concentration of each chemical was then measured
in seawater, muscle, and liver. The results with toluene were as follows:
Toluene Concentration
Fish No. (ppm) BCF
Muscle 1
2
3
4
Mean
Liver 1
2
3
M
Mean 4.8 0.30
Water -- 16.1
The results indicate that BCF in muscle was equal to or greater than the BCF in
liver and that tissue concentrations rarely exceeded the water concentration.
In later experiments, Ogata and Miyake (1978) found that eels (Anguilla
japonica) accumulated toluene to whole-body concentrations greater than the
water concentration in freshwater. For this study, the authors studied the
uptake and elimination of toluene by eels exposed in freshwater to crude oil.
The animals were exposed for 10 days to a recirculating oil suspension (50 ppm,
w/v) which was renewed every day. During this period, the toluene concentration
was measured in pooled groups of 5 eels taken on 1, 5, and 10 days after
beginning exposure. The concentration of toluene in water was measured each day
at 1, 3, 6, 9, 14.5, and 24 hours after preparing the crude oil suspensions. The
16-14
-------
remaining eels were then transferred to clean seawater and sampled after 3, 5,
and 10 days of depuration. The average toluene concentration in water during the
uptake period was 0.130 ppm. The concentration in eels was 0.641 ppm after
1 day, 1.547 ppm after 5 days, and 1.718 ppm after 10 days. The respective BCF
values were 4.9, 11.9, and 13.2. A semilogarithmic plot of the logarithm of
tissue concentration versus time indicated that equilibrium had not quite been
reached by 10 days. The depuration phase of the experiment showed that tissue
concentration decreased rapidly from 1.718 ppm at the beginning of depuration to
0.315 ppm after 3 days, 0.121 ppm after 5 days, and 0.035 ppm after 10 days. A
semilog plot showed that toluene was eliminated "in 2 phases. The elimination
half-time during the first phase, lasting from 0 to 5 days, was 1.4 days. About
93? of the accumulated toluene was eliminated by the end of this period. The
remaining toluene was eliminated at a somewhat slower rate, with about 2% of the
accumulated toluene remaining after 10 days of depuration.
The only information found concerning food-chain transfer of toluene is
provided by Berry and Fisher (1979), who exposed mosquito larvae (Aedes aegypti)
14
to C-toluene for 3 hours and then fed them to bluegill sunfish (Lepomis
macrochirus). In duplicate experiments, each of 25 fish in separate containers
were fed with 10 contaminated larvae. The mean level of radioactivity in 10
larvae was 736 cpm in the first experiment and 3196 cpm in the second experiment.
Internal organs (spleen, gall bladder, liver, stomach, intestine, and kidney)
from 5 fish, sampled at each interval of 1, 4, 8, 24, and 48 hours after feeding,
were analyzed for radioactivity by liquid scintillation counting. Radioactivity
was expressed as counts per minute per organ rather than on a weight basis. The
only organ that had counts-per-minute values significantly greater than back-
ground levels was the stomach at 1, 4, and 8 hours after feeding. The authors
concluded that an insignificant amount of toluene, if any, leaves the digestive
16-15
-------
tract to be accumulated in other organs of sunfish. The validity of this
conclusion is unknown because the dose was so low that absorption, if it had
occurred, could not have been differentiated from background counts and because
the counts were not expressed on a tissue weight basis, even in the stomach.
In summary, the available information indicates that the primary path of
toluene uptake in aquatic organisms is direct absorption from water. The
reported or calculated BCF values for edible portion or whole organism ranged
between <1 to about 14, indicating that toluene has a low bioconcentration
potential. These BCF values are lower than the value predicted on the basis of
the relationship established between octanol-water partition coefficient (P) of
lipophilic compounds and steady-state BCF (Veith^t^l., 1979). This relation-
ship, expressed by the equation "log BCF = (0.85 log P) - 0.70," would predict a
BCF of 39, using a log P value of 2.69 for toluene (see Subsection 3.4.2).
Low bioconcentraton potential, rapid depuration, and the ability of fish to
metabolize toluene all indicate that toluene is unlikely to bioraagnify through
aquatic food chains. Aquatic organisms do accumulate toluene, however, and con-
centrations in edible species from polluted areas have reached levels that cause
organoleptic effects in humans.
16.3 EFFECTS ON MICROORGANISMS
Toluene has been used for quite some time as an antimicrobial agent.
Sabalitschka and Preuss (1954) sterilized a urine sample containing Escherichia
coli and Pseudotnonas fluorescens within 24 hours with 4000 mg/1 toluene.
Threshold concentrations for toluene have been established by Bringmann and Kuhn
(1959, 1976, 1977, 1980) for various microorganisms. These investigators
reported values of 29 mg/1 for £. putida, 200 mg/1 for E. coli, and greater than
450 mg/1 for the ciliated protozoan Uronema parduczi. Partial sterilization of
soil was achieved by adding toluene to the soil (Pochon and Lajudie, 1948).
16-16
-------
The effects of toluene on bacterial activity and growth have also been
studied. As measured by methane evolution rates, 20 mg/1 toluene increased the
growth rate of bacteria in sewage sludge deposits, while 200 mg/1 produced a
toxic effect (Barash, 1957). Similarly low levels of toluene allowed good growth
of P_. putida and Nocardia sp., while saturation levels (515 mg/1 at 20°C) were
toxic (Gibson, 1975). Depending on the concentration (173 to 17,300 mg/1), a
rotifer (Dicranophorus forcipatus) was unaffected, or temporarily inhibited, or
permanently inhibited by toluene (Erben, 1978). Death and disintegration of
rumen ciliates occurred between 460 and 645 mg/1 of toluene (Eadie _et ^1., 1956).
At sublethal concentrations (1000 and 6000 mg/1-), toluene caused a negative
chemotactic response or totally inhibited the chemotatic response of all marine
bacteria tested (Mitchell ejb aL., 1972; Young and Mitchell, 1973). Although the
effects were reversible, the authors of the 1972 paper expressed concern that the
inhibition could seriously undermine the capacity of the marine microflora to
control the self-purification processes in the sea. Beck and Poschenrieder
(1963) found that high concentrations of toluene (50-100,000 mg/g of soil) sup-
pressed soil microflora activity. In addition, they found that gram-positive
bacilli sporefonners, streptomycetes, and cocci were especially resistant, while
gram-negative bacteria were sensitive.
Toluene has been shown to affect the integrity of the microbial cell wall
and cytoplasmic membrane (Dean, 1978). Thompson and Macleod (1974) reported that
marine pseudomonad cells washed and suspended in 0.5 M NaCl were lysed by treat-
ment with 20,000 mg/1 toluene and released 95? of the cells' alkaline phos-
phatase. Because the cells remained intact with 0.05 M MgSCL and 20,000 mg/1
toluene, the authors concluded that Mg ions prevented cellular disruption by
strengthening the integrity of the cell wall. Woldringh (1973) established that
a 2500 mg/1 solution of toluene partially dissolved the inner cytoplasmic
16-17
-------
membrane of Jj. coli and displaced nuclear material to the periphery of the cell.
DeSmet _et al. (1978) reported that at 100,000 mg/1 toluene, the cytoplasmic
membrane was completely disorganized. The presence of Mg ions at lower toluene
concentrations (up to 10,000 mg/1), however, prevented extensive damage to the
cytoplasmic membrane and loss of intracellular material; thus, permeability
depended on the integrity of the outer membrane (DeSmet ^t _al., 1978). Deutscher
(197^) found that the effects of toluene treatment were dependent on various
cultural conditions including pH, temperature, Mg ion concentration, and age of
the culture. Temperature-dependent effects of toluene treatment were also
reported by Jackson and DeMoss (1965). Toluene changed the asymmetric unit
membrane profile to a symmetric profile in vegetative cells of Bacillus subtilis
and caused gaps in the membrane to appear (Silva et al., 1978). Fan and
Gardner-Eckstrom (1975) found that toluene-treated Bacillus megaterium cells
liberated a membrane protein essential for peptidoglyca synthesis and that this
protein could be added back to the membrane to reconstitute peptidoglycan syn-
thesis. Toluene at 86,000 mg/1 induced the autolysis of Saccharomyces
cerevisiae. the release of UV-absorbing substances from the cells, and the
deacylation of phosphoplipids (Ishida, 1978). At saturation concentrations of
toluene, however, no cytolysis of yeast occurred (Lindenberg ^t al., 1957).
Scholz et al. (1959) noted that toluene-treated yeast cells accumulated hexo-
sephosphates. Bucksteeg (19^2) found that the concentration of toluene and time
of exposure determined its effect on Cytophaga sp. and Azotobacter chroococcum.
The lower the concentration, the longer the contact time needed to produce lethal
effects. Azotobacter was more resistant than the Cytophaga sp. Bucksteeg
theorized that toluene affected the physical and chemical constitution of the
cell. An alteration in plaque morphology in two coliphages (T/-rt and T,)
occurred with 1$ toluene (Brown, 1957).
16-18
-------
The ability of toluene to disrupt cell membranes led to the use of this
compound as an unmasking agent in microbial research to assay a variety of
enzymes (Herzenberg, 1959; Dobrogosz and DeMoss, 1963; Levinthal _et al., 1962).
The in vitro assays using toluene have been used to make enzymes within a cell
accessible to exogenous substrates (Jackson and DeMoss, 1965; DeSmet et al.,
1978). Generally, toluene treatment makes the cells permeable to low molecular
weight compounds (such as deoxynucleoside triphosphate dNTP) and several
macromolecules while remaining impermeable to proteins larger than approximately
50,000 daltons (Deutscher, 1974; DeSmet _et al., 1978). Several investigators
have used these findings to study DNA replication in bacteria (E. coli, B.
subtilis), bacteriophage (EJ. coli, T^), and diatoms (Cylindrotheca fusiformis)
after treating the organisms with 0.1 to 1? toluene in solution (Miller et al.,
1973; McNicol and Miller, 1975; Moses and Richarson, 1970; Matsushita _et al.,
1971; Winston and Matsushita, 1975; Sullivan and Valeani, 1976). Other uses of
toluene-treated cells are in studying the synthesis of heteroribonucleotides,
RNA, and peptidoglycan and the repair synthesis of DNA (DeSmet et al., 1978;
Moses and Richardson, 1970; Segev ^t _al., 1973; Winston and Matsushita, 1975).
Burger (1971) showed that toluene-treated E. coli cells continued DNA replica-
tion, but only in that chromosomal region that was about to be replicated
d.n vitro. Toluene-treated cells can also be used to study the effects of various
antibiotics in cell growth and DNA replication (Hein, 1954; Burger and Glaser,
1973).
Although the exact mechanisms of toluene-induced disaggregration of cell
membranes are not knowi, Jackson and DeMoss (1965) state that the mechanisms fall
into two classes: (1) a disaggregrating (autolytic) enzyme(s) perhaps syn-
thesized in the presence of toluene or (2) a direct denaturation of cell membrane
16-19
-------
constituents such as phospholipids; a condition inhibited by stabilizing factors
such as divalent cations (e.g., Mg).
16-20
-------
17. EFFECTS ON AQUATIC SPECIES
17.1 GUIDELINES FOR EVALUATION
Evaluation of the available information concerning the effects of toluene
on aquatic organisms must take into account several factors. A primary con-
sideration for evaluation of toxicity test results is toluene's high volatility.
The half-life for volatilization of toluene from a water column 1 m deep has been
reported to be between about 30 minutes (Mackay and Wolkoff, 1973) and 5 hours
(Mackay and Leinonen, 1975). Benville and Korn (1977) analyzed the toluene
concentration in test containers during a 96-hour static toxicity test and showed
that the percentage of toluene lost was 48/6 by 24 hours, 53% by 48 hours, and
greater than 99$ by 72 hours. Korn jit _al. (1979) reported that toluene was lost
at a greater rate from bioassay containers at 12°C (99? loss by 72 hours) than at
8°C (>99% loss by 96 hours) or at 4°C (15% loss by 96 hours). Potera (1975)
found that the observed half-life of toluene in bioassay containers was 16.5
± 1.13 hours. The rate of volatilization of toluene from water varies with the
amount of mixing, temperature, surface area to volume ratio, and other factors.
Adsorption of toluene to sediments and suspended particles may interfere with
volatilization and may influence the availability of toluene to aquatic organ-
isms.
Most of the reported aquatic toxicity studies with toluene have used a
static exposure technique. In most cases, the LC50 has been calculated on the
basis of initial nominal (unmeasured) or initial measured concentrations. The
test organisms in these static experiments, however, are exposed to rapidly
decreasing toluene concentrations. Most of the reported acute static toxicity
studies show little or no change in the LC50 value between 24 and 96 hours. This
lack of change indicates that most, if not all, of the mortalities in these tests
17-1
-------
occurred during the first 24 hours when toluene concentrations were highest. In
contrast, those flow-through studies that reported acute LC50 values at more than
one exposure period showed that LC50 values decreased significantly with time.
Numerous other factors may affect the results of toxicity tests with
toluene. It has been shown that the acute toxicity of toluene is affected in
some cases by temperature and salinity (Subsection 17-3). These effects on
toxicity may be due to effects on the test organisms (metabolism, uptake, stress,
etc.), effects on the physicochemical behavior of toluene (solubility, volatili-
zation, etc.), or interactive effects of both. For example, toluene is less
soluble in saltwater than in freshwater and is bo'th more soluble and more vola-
tile at higher temperatures. Laboratory results may also be influenced by the
loading ratio (gram organism per liter water); dissolved oxygen concentration;
age, health, and species of test organisms; and other exposure conditions, all of
which may interact to affect the results in an unpredictable manner.
Prediction of environmental effects from laboratory results must consider
the influence of the variables associated with laboratory tests and with the
natural variability intrinsic to the aquatic environment. Results of static
acute toxicity tests with volatile compounds such as toluene are most closely
related to the effects that may occur in nature during accidental spills, because
toluene concentrations rapidly decrease in both situations. Flow-through tests
provide some insight into the expected effects of chronic release of toluene into
the aquatic environment, as might occur in areas receiving refinery or petro-
chemical effluents.
17.2 EFFECTS OF ACCIDENTAL SPILLS
No information was found concerning the effects of accidental spills of
toluene per se^ on aquatic organisms; however, toluene is one of the major
aromatic components of crude oil and such refined petroleum products as diesel
17-2
-------
fuel, gasoline, and jet fuel, all of which have been released in large amounts to
the aquatic environment during spills.
The long-term ecological impact of accidental spills of pure toluene is
unlikely to be serious because toluene is so rapidly lost through volatilization.
For instance, McAuliffe (1976) reported that toluene, benzene, and xylene could
be found in the water under crude oil slicks only during the first 30 minutes
after spillage; however, toluene spills are likely to cause acute mortality of
aquatic species if the spillage occurs in areas of shallow water and restricted
water flow, such as in certain portions of estuaries, lakes, and streams.
Toluene is acutely toxic to many aquatic species of concentrations well below its
water solubility, and lethal exposure may well occur during spills in shallow
water.
Although chronic, low-level pollution by toluene has been reported in a
Japanese river (Funasoka e_t _aL., 1975) and a harbor (Ogate and Miyake, 1973) that
received refinery and petrochemical effluents, the effects of such low-level
chronic pollution are unknovm.
17.3 LABORATORY STUDIES OF TOHCITY
17.3.1 Lethal Effects
The lethal effects of toluene have been reported for numerous species of
freshwater and marine fish and invertebrates. No information was found concern-
ing the effects of toluene on amphibians.
17.3.1.1 Freshwater Fish
The earliest investigation of toluene toxicity to freshwater fish was con-
ducted by Shelford et _al. (1917), who reported that 1 hour of exposure to 61-
65 mg/1 toluene was lethal to orange-spotted sunfish (Lepomis humilis). This
test was conducted under static conditions at 20°C in freshwater of unspecified
temperature and composition.
17-3
-------
Degani (1943) conducted static toxicity tests with 15 day-old lake trout
(Salvelinus namaycush) fry and 1.5-g mosquitofish (Gambusia affinis) in dechlor-
inated tapwater at 17-18°C using 3 to 5 fish per container (2-liter volume). The
time to death at a nominal exposure concentration of 90 ppm toluene was
390 minutes for trout and 47 minutes for mosquitofish. The time to death of
trout fry exposed to 50 ppm toluene was 258 minutes.
Wallen _et jd. (1957) also conducted static acute toluene toxicity tests with
female mosquitofish (Gambusia affinis) of unspecified size in turbid pond water
(150 ppm turbidity as measured by Jackson turbidimeter, pH 7.5-8.5, methyl
orange alkalinity < 100 ppm, temperature 17-22°C.). For these toxicity tests,
10 fish per concentration were added immediately after addition of different
amounts of toluene to the bioassay containers (15-liter volume). The test
solutions were constantly aerated and mortalities were recorded daily for
96 hours. The 24-, 48-, and 96-hour LC50 values were 1340, 1260, and 1180 ppm,
respectively. These values were estimated on the basis of the initial nominal
toluene concentrations. Because the test containers were vigorously aerated, it
is probable that the actual toluene concentrations decreased rapidly during the
exposure period. It was also observed that the turbidity of the toluene solu-
tions decreased from 150 to 100 ppm over the 96-hour exposure period. At concen-
trations of 560 ppm and below, all fish appeared to be unaffected. The remainder
of the test results are presented below:
Concentration Percent Mortality (N = 10)
(ppm)
<_ 560
1,000
1,800
3,200
5,600
10,000
24 h
0
20
80
80
100
100
48 h
0
30
80
90
100
100
96 h
0
40
100
100
100
100
17-4
-------
Pickering and Henderson (1966) investigated the acute toxicity of toluene
to fathead minnows (Pimephales promelas), bluegill sunfish (Lepomis
macrochirus), goldfish (Carassius auratus), and guppies (Lebistes reticulatus
= Poecilia reticulata). The length and weight of the fish used for testing were
3.8-6.1 cm and 1-2 g for the first 3 species and 1.9-2.5 cm and 0.1-0.2 g for
guppies. Each test utilized 10 fish per concentration or control in either 10 1
(minnows, sunfish, goldfish) or 2 1 (guppies) of soft water (pH 7.5, alkalinity
18 mg/1, EDTA hardness 20 mg/1) made by mixing 5 parts of hard natural spring
water with 95 parts of distilled demineralized water. In addition, fathead
minnows were tested (10 fish/concentration) in the hard spring water (pH 8.2,
alkalinity 300 mg/1, EDTA hardness 360 mg/1) to investigate the effect of these
water characteristics on toluene toxicity. All tests were conducted at 25°C.
The test solutions were not aerated, and dissolved oxygen concentrations were
measured but not reported. The 24-, 48-, and 96-hour LC50 values and their 95J
confidence limits, as calculated by the moving average-angle method of Harris
(1959) using initial nominal toluene concentrations, are presented in
Table 17-1. The 96-hour LC50 values increased in the order of bluegill sunfish
(24.0 mg/1), fathead minnow (34.3 mg/1 in soft water, 42.3 mg/1 in hard water),
goldfish (57.7 mg/1), and guppies (59-3 mg/1). The 96-hour LC50 for fathead
minnows in soft water was not significantly different from the 96-hour LC50 for
the same species in hard water. Comparison of the 95? confidence limits of the
96-hour LC50 values in soft water for the 4 species indicated that the LC50
values were not significantly different between fathead minnows and bluegill
sunfish or between goldfish and guppies. Both fathead minnows and bluegill
sunfish had 96-hour LC50 values significantly lower than goldfish and guppies.
The 96-hour LC50 was not significantly different from the 24-hour LC50 for any of
the species tested in soft water.
17-5
-------
Table 17-1. Acute Toxicity of Toluene to Fish and Aquatic Invertebrates
cr>
Species
Temp. Type 21-h
(°C) Test
LC50
18-h 72-h
No Effect
96-h Concentration
Reported
Concentration
Units
Comments
Reference
FISH
Freshwater
Ide
(Leuclscus idua
melanotus)
Mosquito fish
(Cambusia affinis)
Goldfish
(Carassiua auratus)
Goldfish
(Caraaaiua auratus)
Goldfish
(Carasslus auratus)
Fathead minnow
(Pimephales promelas)
Fathead minnow
(Pimephales promelas )
Blueglll sunfish
(Lepoala macrochirus)
20+1 SU
20+1 SU
17-22 SU 1310
20+1 SM 58
25 SO 57.7
(18.9-
68.8)
17-19 FM 11.6
(32.0-
71.7)
25 SU M6.3
(37.0-
59.1)
25 SU 56 .0
(11.7-
67.1)
25 SU 21.0
(18.9-
30.5)
70
122
1260
57.7
(18.9-
68.8)
27.6 25.3
(21.6- (20.1-
36.0) 31.9)
16.3
(37.0-
59.D
56 .0
(16.7-
67.1)
21.0
(18.9-
30.5)
52
365
1180 560
— —
57.7
(18.9-
68.8)
22.80
(17.1-
30.0)
31.3
(22.8-
15.9)
12.3
(33.5-
53.5)
21.0
(10.9-
30.5)
mg/1
ppm
mg/1
rag/1
ppm
mg/1
mg/1
mg/1
Lab 1, 100$ kill at
88 mg/1.
Lab 2, 100} kill at
170 mg/1. 3uf(,oi^^
Tests were^ conducted
under identical
conditions.
Tests were conducted
in aerated turbid
pond water.
Test was conducted
in tap water (pH
7.8)
Test was conducted
in soft water.
Tests were conducted
under flow-through
conditions In soft
dechlorinated tap
water. The test was
continued to 720 h
(30 d) at which
time the LC50 (and
95J confidence inter-
val) was 11.6 (10.7-
20.0) ppm.
Tests were conducted
in soft water.
Tests were conducted
in hard water.
Tests were conducted
in hard water.
Juhnke and
Ludemann, 1978
Ha lien et al. ,
1957
Bridie et al.,
1979
Pickering and
Henderson, 1966
Brenniroan et al. ,
1976
Pickering and
Henderson, 1966
Pickering and
Henderson, 1966
-------
Table 17-1. Acute Toxicity of Toluene to Fish and Aquatic Invertebrates (Cont.)
Species
Temp. Type 2l-h
(°C) Teat
LC50
18-h 72-h
No Effect
96-h Concentration
Reported
Concentration
Units
Comments
Reference
Blueglll sunfish
(Lepomla macrochlrua)
Guppiea
(Poecllia reticulatr)
Zebrafiah
(flrachydanio rerio)
Medaka
(Oryziaa latipes)
Medaka
(Oryzlas latipes)
Coho salmon fry
(Oncorhynchus kisuteh)
MARINE
Coho salmon
(Oncorhynchua kisuteh)
Pink salmon fry
(Oncorhynchus klautch)
Pink salmon
(Oncorhynchua klautch)
NR SU 16.6
(15.0-
19.1)
25 SU 62.8
(55.0-
73.7)
20+1 FU
25+2 SU 80
(mean=
80)
25+2 SU 11
FM
FM
8 SU
12 SM 5-1
(1.1-
6.5)
1 SM
8 SM
12 SM
13.3 12.7
(11.6- (11.5-
11.8) 11.5)
61.0
(52.8-
71.9)
25-27
20-135
(mean:
63)
36
—
22.1 22.1
"""~~ — — —
12.7 10.0
(11.5-
11.5)
59.3
(50.9-
70.3)
23-110 £16
(mean:
51)
32
9.36
3.08
22.1 10
— — — —— —
6.11
(5.73-
7.18)
7.63
(6.86-
8.18)
8.09
(7.15-
8.78)
ppm
mg/1
mg/1
mg/1
mg/1
ul/1
ul/1
ppra
ppm
Only these data
cited in U.S. EPA,
1980.
Testa were conducted
in hard water.
Tests were conducted
in closed aquaria
with dechlorinated hard
tap water at a flow
rate of 6 1/h.
Range and mean of
LC50 values for dif-
ferent atage embryos
LC50 values for fry.
The 168-h LC50 was
23 mg/1.
Unparasltized
Parasitized
Teats were conducted
in artificial aalt-
water (pH 8.1, 30°/oo
aalinity).
Tests were conducted
according to methods
of Korn et al. , 1979.
Tests were conducted
with salmon fry
acclimated to 28°/oo
seawater at dif-
ferent temperatures.
U.S. EPA, 1978
Pickering and
Henderson, 1966
Slooff, 1978
Slooff, 1979
Stoss and Hainea,
1979
Stoss and llaines,
1979
Molea, 1980
Moles, 1980
Morrow et al. ,
1975
Thomas and Rice,
1979
Korn et al. , 1979
-------
Table 17-1. Acute Toxicity of Toluene to Fish and Aquatic Invertebrates (Cont.)
A>
Species Temp.
Striped bass 16
(Morone aaxatilis)
Sheepshead minnow A/fl
(Cyprinodon variegatus)
INVERTEBRATES
Freshwater
Water flea 22+1
(Daphnia magna )
Water flea 23
(Daphnla magna)
Mosquito larvae 25+1
(Aedes aegypti)
Marine
Brine shrimp nauplli 21.5
(Artemla salina)
Bay shrimp 16
(Crago franclscorum)
Shrimp 1
(Eualus spp. )
8
12
LC50 No Effect
Type 21-h 18-h 72-h 96-h Concentration
Test
SM 7.3 7.3
SU >277 >277 >277 277
<185 <185 <185
SU 310 310 28
(210- (210-
120) 120)
SU 60
SM 21.52 9.95
(21.36-
21.68)
SU 33
SM 12 1.3
(10-13) (3.1-5.8)
SM — 21.1
(19.5-
23-5)
SH 20.2
(17.9-
22.8)
SM 11.7
(13.1-
16.6)
Reported
Concentration
Units
pl/1
ppm
mg/1
mg/1
1
ppm
mg/1
pl/1
pl/1
pl/1
pl/1
Comments
Tests were conducted
in 25°/oo salinity
sea water with juvenile
fish.
Data only cited in
U.S. EPA, 1980.
Test was conducted
with reconstituted
well water (hardness
72+6 mg/1 as CaCO,,
pH 7.0+0.2) in 3
containers sealed with
plastic wrap.
Test was conducted
in natural water (pH
7.5, hardness 211 mg/1)
Test was conducted
with distilled
water.
Test was conducted
with artificial sea-
water.
Tests were conducted
with 25°/oo
salinity seawater.
Reference
Benville and
Korn, 1977
U.S. EPA, 1978
LeBlanc, 1980
Brlngmann and Kuhn,
1959
•
Berry and
Brammer, 1977
Price et al. , 1971
Benville and
Korn, 1977
Korn et a.1 . , 1979
Korn et al. , 1979
Korn el al., 1979
-------
Table 17-1. Acute Toxicity of Toluene to Fish and Aquatic Invertebrates (Cont.)
Species
Grass shrimp
(Pacaemonetes pugio)
Grass shrimp
(Pacaemonetea pugio)
Grass shrimp
(Palaemonetes pugio)
Mysld shrimp
(Hysidopaia bahia)
Dungeness crab
(Cancer magister)
Copepod
(Hitocra splnipes)
Pacific oyster
(Craasostrea gigas)
LC50 No Effect
Temp. Type 21-h 18-h 72-h 96-h Concentration
(°C) Teat
20 SM 20.2
(16.3-
22.5)
20 SM 17.2 .
(11.9-
19.1)
10 SM 37.6
(35.0-
10.3)
10 SM 38.1
(36.1-
39.6)
20 SM 30.6
(21.3-
11.5)
20 SM 25.8
(18.8-
31.6)
NR SU 9.5
NR SU 61.8 56.3 56.3 56.3 27.7
(50.9- (13.0- (13.0- (13.0-
82.5) 70.8) 70.8) 70.8)
NR FU 170 28
20 SM 21.2
(19.8-
30.2)
20 SM 71.2
(52.0-
100.5)
20- SU 1050
21.5
Reported
Concentration Comments
Units
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
ppm
mg/1
mg/1
mg/1
mg/1
Adults at 15°/oo
salinity.
Adults at 25°/oo
salinity.
Adults at 15°/oo
salinity.
Adults at 25°/oo
salinity.
Larvae at 15°/oo
salinity.
Larvae at 25°/oo
salinity.
—
Data only cited in
U.S. EPA,- 1980.
Larvae.
15°/oo salinity.
25°/oo salinity.
Larvae.
Reference
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Neff et al. , 1976
U.S. EPA, 1978
Caldwell et al.,
1976
Potera, 1975
Potera, 1975
Legore, 1971
Abbreviations: Temp. - temperature; h = hour; d = day; NR = not reported.
-------
Static acute LC50 values for bluegill sunfish have also been reported by the
U.S. EPA (1978, cited in U.S. EPA, 1980). The 24-, 48-, 72-, and 96-hour LC50
values were 16.6, 13.3, 12.7, and 12.7 ppm, respectively. No effects were
observed at or below 10 ppm. Additional information concerning these tests was
not available.
Berry (1980) mentioned that the upper non-lethal toluene concentration for
bluegill sunfish (Lepomis macrochirus) was 8.7 mg/1. The duration of exposure
and lowest lethal concentration were not specified.-
Bridie ^t_al. (1979) and Brenniman et _al. (1976) also investigated the acute
toxicity of toluene to goldfish. Bridie ^t al. (J979) used goldfish of slightly
greater weight (mean 3-3 g, range 2.3-4.3 g) than Pickering and Henderson (1966)
to determine the static 24-hour LC50. In this test, 6 fish per concentration
were exposed without aeration to a toluene series in 25 1 of tapwater that had a
pH of 7.8 and contained (in milligrams per liter): Cl~ = 65; NO ~= 0; NO ~ = 4;
S042" = 35; P043" = 0.15; HC03" = 25; Si02 = 25; NH^* = 0; Fe = 0.05; Mn = 0;
Ca = 100; Mg = 8; and alkali as Na+ = 30. The toluene concentration was
measured at the beginning and end of the test. The 24-hour LC50, obtained by
interpolation from a graph of the logarithm of concentration versus percent
mortality, was 58 mg/1, which is the same as the 24-hour LC50 for goldfish
reported by Pickering and Henderson (1966).
Much larger goldfish (length, 13-20 cm; weight, 20-80 g) were used by
Brenniman ^_t al. (1976) to determine the acute toxicity of toluene under flow-
through exposure conditions. The LC50 values were determined by exposing 6 fish
per 38-1 aquarium to three toluene concentrations (and a control) in
dechlorinated soft tapwater (methyl orange alkalinity = 34 ppm as CaCO-; phenol-
phthaline alkalinity = 37 ppm as CaCO..; total hardness = 80 ppm as CaCO-;
calcium = 21.6 ppm; magnesium = 5.3 ppm; SiO, = 8 ppm; chromium = <0.002 ppm;
17-10
-------
pH 7.0 + 0.3; temperature 17-19°C) at a flow rate calibrated to renew the test
chamber volumes every 1.5 hours. This flow rate was sufficient to maintain
dissolved oxygen concentrations at >7 ppm and to maintain constant toluene con-
centrations, as measured by continuous monitoring at 210 nm by spectrophoto-
meter. The 24-, 48-, 72-, and 96-hour LC50 values, calculated by probit analy-
sis, were 41.6, 27.6, 25.3, and 22.8 ppm, respectively. Although most of the
fish died during the first 24 hours, the 96-hour LC50 was significantly lower
than the 24-hour LC50. These LC50 values are somewhat lower than those reported
by Pickering and Henderson (1966) and Bridie e_t al. (1979) for goldfish tested
under static conditions. In addition, the LC50 values reported by Pickering and
Henderson (1966) did not decrease significantly from 24 to 96 hours. These
differences are probably due to a rapid decline in the toluene concentration
through evaporation in the static tests in contrast to constant toluene concen-
trations in the flow-through test.
Juhnke and Ludemann (1978) investigated the static acute toxicity of
toluene to the ide (Leuciscus idus melanotus) using comparable procedures in two
different laboratories. The toxicity tests were conducted according to the
methods of Mann (1975, 1976), i.e. 48 hours of exposure with 10 fish (1.5 +
0.3 g, 5-7 cm) per concentration in tapwater (pH 7-8, hardness 268 + 54 mg/1) at
20 + 1°C. The 48-hour LCD (0% mortality), LC50, and LC100 (100$ mortality)
values determined at each laboratory were as follows:
48-Hour Lethal Concentration Values (mg/1)
LCO LC50 LC100
Laboratory 1 52 70 88
Laboratory 2 365 422 470
Although it was stated that these tests were conducted under comparable
conditions, the results were clearly different. The concentration that caused no
deaths of fish in laboratory 2 (365 mg/1) was about 4 times higher than the
17-11
-------
concentration that killed all fish in laboratory 1 (88 mg/1). The authors did
not discuss the reasons for the difference in results.
Slooff (1978, 1979) reported that the 48-hour LC50 of toluene to zebrafish
(Brachydanio rerio) was 25-27 mg/1. This test was conducted under flow-through
(6 I/hour) exposure conditions using 10 fish per concentration in 10-1 sealed
aquaria and dechlorinated tapwater (20 + 1°C; pH 8.0 + 0.2; hardness 180 +
1.8 mg/1 as CaCO,).
The acute effects of toluene on parasitized and unparasitized coho salmon
(Oncorhynchus kisutch) fry were studied by Moles (1980). The parasitized fry
were artificially infected before toluene exposure with glochidial larvae of the
freshwater mussel, Anodonta oregonensis. Toluene exposure was conducted under
flow-through conditions, using five measured concentrations and 20 fish per
concentration. The temperature and characteristics of the water used were not
specified. The 96-hour LC50, as calculated by probit analysis, was
9-36 yl/1 (ppm) for unparasitized fish and 3-08 yl/1 for fish parasitized with a
mean number of 69 glochidia per fish. The LC50 values were significantly dif-
ferent, indicating that parasitized fish were less resistant to the effects of
toluene.
Stoss and Haines (1978) investigated the effects of static exposure to
toluene on the survival of fertilized eggs and newly hatched fry of the medaka,
Oryzias latipes. Groups of 10 eggs or fry were exposed in loosely capped vials
containing 20 ml of the exposure medium (synthetic rearing medium: pH 7.6;
akalinity 99 mg/1 as CaCO_) at 23 ± 2°C. Toluene concentrations were prepared by
diluting a water-soluble extract of 10 ml toluene/1 medium. In order to deter
mine the sensitivity of different stages of embryo development, tests were begun
with eggs of various age's after fertilization. Tests with fry were all begun
within 24 hours after hatching. Nominal initial toluene concentrations were
17-12
-------
used for calculation of LC50 values. The LC50 values for embryos varied with
length of exposure and the age at time of introduction. The mean 24-, 48-, and
96-hour LC50 values for all ages of embryos were 80, 63, and 54 mg/1. The range
of LC50 values was 20 to 135 mg/1 at 48 hours and 23 to 110 mg/1 at 96 hours
(Stoss, personal communication). Early (<_3.5 hours old) and late (>_192 hours
old) embryos had significantly lower LC50 values at each exposure period than
embryos of intermediate age at time of introduction. The 24-, 48-, 96-, and
168-hour LC50 values for fry were 44, 36, 32, and 23 mg/1, respectively (Stoss,
personal communication). These values were lower than the mean embryo LC50
values for the same exposure period; however, fry LC50 values were greater than
the LC50 values for the susceptible early and late stage embryos and lower than
most of the LC50 values for intermediate stage embryos. Stoss and Haines (1978)
also investigated the sublethal effects of toluene on hatching time and induction
of developmental abnormalities. These sublethal effects are discussed in
Section 17.3.2.1.
17.3-1.2 Marine Fish
Morrow _et al. (1975) studied the effects of toluene on young coho salmon
(Oncorhynchus kisutch) that had been acclimated to artificial seawater (30 °/oo
(parts per thousand) salinity; 8°C; pH 8.1) for up to 2 weeks. A static exposure
technique was used in which toluene was added directly to exposure aquaria
containing fish and 73 1 of seawater (<_1 g fish/1 water) to give nominal concen
trations of 0, 1, 10, 50, and 100 ppm toluene. The average weight of the fish
used during triplicate tests ranged from 5 g/fish in the fall of the year to
nearly 40 g/fish in the spring. The mortality data provided in the paper are
given below:
17-13
-------
Percent Mortality
Concentration No. of
(ppm)
0
1
10
50
100
Tests
3
3
3
1
3
No. of Fish per
Concentration
30
30
30
10
30
0 h
0
0
0
0
0
24 h
7
7
0
90
93
48 h
7
7
0
100
100
72 h
13
13
3
100
100
96 h
13
13
10
100
100
Using 2x2 contingency table analysis, the authors determined that mortal-
ity was significantly different from control mortality at 50 and 100 ppm, but not
at 10 and 1 ppm. The reasons for control mortality were not discussed but may
have been due to salinity stress; the authors mentioned that smaller fish adapted
less easily to seawater than larger fish. In order to incorporate these data
into Table 17-1, the LC50 values were calculated as the geometric mean of 50 ppm
(mortality = 100?) and 10 ppm (mortality corrected for control mortality = 0/t).
This value for the 48-, 72-, and 96-hour LC50 was 22.4 ppm. The authors state
that fish exposed to 50 and 100 ppm toluene exhibited rapid, violent, and erratic
swimming within 15 to 20 minutes, followed by "coughing," loss of equilibrium,
and death of most fish within the first few hours.
The acute effects of toluene on another species of salmon in seawater were
investigated by Korn ^t_al. (1979). Pink salmon (Onchorhynchus gorbuscha) fry,
weighing about 0.35 g each, were acclimated to natural seawater (6-8°C;
26-28 °/oo salinity). Groups of fry were then acclimated to 4, 8, or 12°C for
determination of the 96-hour LC50 at 3 temperatures. Each toxicity test was
conducted with 10 to 15 fry per concentration (< 1 g fish/1 water). Fish were
added to the test containers after addition of an appropriate amount of toluene-
in-water stock solution. The containers were not aerated until after the first
48 hours of exposure to minimize evaporative loss. Even so, analysis showed that
toluene decreased to nondetectable levels by 72 hours at 12°C and by 96 hours at
8°C and to 25$ of the initial concentration by 96 hours at 4°C. The 96-hour LC50
17-14
-------
values, estimated by probit analysis using initial measured concentrations
expressed as microliters per liter toluene (= ppm), were 6.4 at 4°C, 7.6 at 8°C,
and 8.1 at 12°C. The 95? confidence intervals of the 4°C and 12°C LC50 values did
not overlap, indicating that temperature affected the toxicity of toluene. There
was no significant difference between 24- and 96-hour LC50 values because almost
all deaths occurred within the first 24 hours of exposure. The effect of
temperature may have been caused by greater sensitivity of the fish at the lower
temperature and/or by the longer persistence of toluene at the lower temperature.
Thomas and Rice (1979) used the previously described techniques of Korn
et al. (1979) to determine the static 24-hour LC50 of toluene with somewhat
larger (1-2 g, 4.5-5.5 cm) pink salmon fry at 12°C in seawater. The 24-hour LC50
(and 95% confidence interval) was 5.4 (4.4-6.5) ppm, which is significantly
different from the 96-hour LC50 value of 8.1 ppm (7.5-8.8) obtained with younger
fry at 12°C by Korn _et _al. (1979). The reasons for this difference cannot be
determined from the information provided.
A similar static exposure technique was used by Benville and Korn (1977) in
their study of the acute toxicity of toluene to juvenile striped bass (Morone
saxatilis) in seawater (25 °/oo salinity, 16°C). The test was initiated by
adding different amounts of saturated toluene in water stock solution to the test
aquaria, each containing 10 fish. Toluene concentrations were measured at the
beginning of the test and every 24 hours thereafter to the end of the test. The
24- and 96-hour LC50 values were both 7.3 ul/1 (ppm). Almost all mortalities
occurred within 6 hours. The average percent loss of toluene was 40? by
24 hours, 53? by 48 hours, and >99? by 72 hours.
The only other information available concerning the lethal effects of
toluene on marine fish is provided in a U.S. EPA unpublished study (1978, cited
in U.S. EPA, 1980). The 24-, 48-, and 96-hour static acute LC50 values for
17-15
-------
sheepshead minnows (Cyprinodon variegatus) were all reported to be greater than
277 ppm and less than 485 ppm. The no-effect concentration was 277 ppm. No
other information concerning these results was available.
17.3.1.3 Freshwater Invertebrates
Berry and Brammer (1977) investigated the acute static toxicity of toluene
to fourth-instar larvae of the mosquito, Aedes aegypti. The larvae were reared
from eggs and tested in distilled water at 25 + 1°C. For each of four replicate
tests, duplicate groups of 20 larvae each were exposed to 14 toluene concentra-
tions. The mortality data were pooled (160 larvae/concentration) to calculate
the 24-hour LC50 by probit analysis. Initial exposure concentrations were deter-
mined by gas-liquid chromatography. The 24-hour LC50 ( + standard error) was
21.52 + 0.16 ppm. The highest concentration (+_ standard error) that caused no
mortality over the 24-hour exposure period was 9.95 + 1.30 ppm.
Berry (1980) mentioned that the upper non-lethal toluene concentration for
crayfish (Orconetes rusticus) was 104.4 mg/1. The duration of exposure and
lowest lethal concentration were not specified.
The acute toxicity of toluene has also been determined with the cladoceran,
Daphnia magna, by Bringmann and Kuhn (1959) and by LeBlanc (1980). Bringmann and
Kuhn (1959) reported a 48-hour LC50 of 60 mg/1. This static test was conducted
with first instar (<24 hours old) Daphnia magna in natural freshwater (pH 7.5;
hardness 214 mg/1) at 23°C.
LeBlanc (1980) conducted static tests with first instar (<24 hours old)
animals in deionized well water reconstituted to a total hardness of 72 ± 6 mg/1
as CaCO- and a pH of 7.0 ± 0.2 at 22 + 1°C. Three groups of 5 daphnids each were
exposed to each of at least five toluene concentrations and uncontaminated water
in covered 250-ml beakers containing 150 ml of test solution. The 24- and
48-hour LC50 values (and 95$ confidence intervals), based on initial nominal
17-16
-------
concentrations, were both 310 (240-420) mg/1. The "no discernible effect con-
centration" was 28 mg/1. This LC50 value is considerably higher than that
reported by Bringmann and Kuhn (1959). The reasons for this difference cannot be
determined from the data provided.
17.3.1.4 Marine Invertebrates
Price jit _al. (1974) determined the static 24-hour LC50 of toluene to brine
shrimp nauplii (Artemia salina) in artificial seawater (27.87 g/1 NaCl; 1.36 g/1
CaS04; 3.17 g/1 MgS(y7H20; 8.42 g/1 MgCl2; 0.79 g/1 KC1; 0.16 g/1 MgBr2»6H20)
at 24.5°C. Groups of 30-50 newly hatched brine shrimp were exposed to 5 toluene
concentrations in 100 ml seawater. The estimated 24-hour LC50, based on initial
nominal concentrations, was 33 ng/1.
Bay shrimp (Crago franciscorum) were shown by Benville and Korn (1977) to be
somewhat more sensitive to toluene. The 24-hour static LC50, determined in
natural seawater (25 °/oo salinity) at 16°C, was 12 ul/l(ppm). The 96-hour LC50
for this species (4.3 ul/1) was significantly lower than the 24-hour LC50 (non-
overlapping 95$ confidence limits). These values were calculated from initial
measured toluene concentrations.
Korn £t al. (1979) investigated the effects of temperature on the acute
toxicity of toluene to another genus of shrimp (Eualus spp.). Shrimp (0.8 g;
6 cm long) were acclimated to the test temperatures in natural 26-28 °/oo
salinity seawater for 4 days and then exposed in groups of 10-15 animals to a
series of toluene concentrations, prepared by dilution of a saturated water
solution. The tissue loading in the test containers was less than 1 g/1. Mea-
surement by UV spectrophotometry showed that toluene concentrations decreased to
nondetectable levels by 72 hours at 12°C and by 96 hours at 8°C, and to 25$ of
the initial concentration by 96 hours at 4°C. The 96-hour LC50 values, calcu-
lated from initial measured toluene concentrations, were 21.4 ul/1 at 4°C,
17-17
-------
20.2 yl/1 at 8°C, and 14.7 yl/1 at 12°C. The 96-hour LC50 values at 4°C and 8°C
were not significantly different (overlapping 95$ fiducial limits) from each
other, but both were significantly higher than the 96-hour LC50 at 12°C. This
trend of greater toxicity at higher temperatures was opposite to the relationship
found by these authors for pink salmon fry (Section 17.3-1.2) and by Potera
(1975) for grass shrimp (see below). The reasons for this difference could not
be established but may have been due to some combination of effects of tempera-
ture on persistence of toluene in water, altered toluene uptake and metabolic
rates, and possible interaction of toluene toxicity and temperature stress. The
authors concluded that temperature affected the-toxicity of toluene to these
species of shrimp and salmon but that it would be impossible to predict the
effects of temperature change on the toxicity of toluene to other species.
Potera (1975) investigated the effects of temperature (10 and 20°C),
salinity (15 and 25 °/oo), and life stage (larvae and adults) on the static
24-hour LC50 of toluene to the grass shrimp, Palaemonetes pugio. The 24-hour
LC50 values, based on measured initial concentrations, ranged from 17.2 to
38.1 mg/1.
As shown by overlapping 95% confidence intervals (Table 12-1), there was no
significant difference in LC50 values between adults and larvae at the same
salinity and temperature, or between adults tested at the same temperature but at
different salinities. The LC50 was significantly lower at 20°C, however, than
at 10°C for adults tested at either 15 °/oo or 25 °/oo salinity. The time to
produce narcosis in at least 50$ of adult shrimp at 20°C was less than 30 minutes
at initial exposure concentrations of 19.8 mg/1 and greater. Recovery of more
than 90$ of exposed shrimp could occur if shrimp were transferred to clean water
after exposure to up to 30 mg/1 for 30 minutes.
17-18
-------
Potera (1975) also determined the 24-hour LC50 for the copepod, Nitocra
spinipes, at a temperature of 20°C and at salinities of either 15 °/oo or
25 °/oo. The 24-hour LC50 values from replicate tests were 24.4 at 15 °/oo
salinity and 74.2 mg/1 at 25 °/oo salinity. These values were significantly
different (non-overlapping 95$ confidence intervals). Potera (1975) suggested
that the lower salinity may have stressed the copepods, resulting in a lower LC50
value.
Neff et al. (1976) also determined the static 96-hour LC50 of toluene to
grass shrimp, Palaemonetes pugio. This value, based on initial nominal concen-
trations, was 9.5 ng/1, which is lower than the 24-hour LC50 values reported by
Potera (1975).
Caldwell _et al. (1976) determined the 48- and 96-hour LC50 of toluene to
larval stages of the dungeness crab (Cancer magister) under flow-through expo-
sure conditions. The 48- and 96-hour LC50 values were 170 and 28 mg/1, respec-
tively.
Static acute LC50 values for mysid shrimp (Mysidopsis bahia) have been
reported by the U.S. EPA (1978, cited in U.S. EPA, 1980). The 24- and 48- to
96-hour LC50 values were 64.8 and 56.3 ppm, respectively. The "no effect"
concentration was 27.7 ppm. Additional information concerning this test was not
available.
The ' 48-hour static LC50 of toluene to larvae of the Pacific oyster
(Grassestrea gigas) was reported to be 1050 mg/1 (LeGore, 1974). This test was
conducted with filtered seawater (25.3-30.8 °/oo salinity) at 20-21.5°C using
30,000 larvae per exposure concentration.
17-19
-------
17.3.2 Sublethal Effects
17.3.2.1 Fish
Very little information is available concerning the sublethal effects of
toluene exposure on fish. Morrow e_t _al. (1975) studied the effects of several
aromatic hydrocarbons, including toluene, on the levels of Na+ and K+ in the
blood of young coho salmon (Oncorhynchus kisutch) in seawater. Static exposure
to 30 ppm toluene caused a small increase in these blood cations, reaching a
maximum at about 2 hours after beginning exposure. The Na* concentration
returned to the control level by 3 hours. Blood K"1" decreased after 2 hours but
was still elevated at 4 hours, the last sampling"period. The toluene exposure
concentration of 30 ppm was sufficient to cause some mortalities and behavioral
effects. The authors suggested that toluene increased membrane permeability,
particularly in the gills. In the hypertonic seawater medium, this change would
result in ion influx and water loss in the fish, perhaps accounting for the
initial rise in blood ion concentration.
Brenniman j_t _al. (1979) conducted a series of experiments to determine the
effects of toluene exposure on blood gas physiology, hippuric acid content, and
histopathology of goldfish (Carassius auratus). The fish used in these experi-
ments were exposed to two or more toluene concentrations under flow-through
conditions using dechlorinated tapwater.
For the pathology study, groups of six fish were exposed for up to 30 days
to 0, 5, 10, and 21 ppm toluene (Brenniman e_t _al., 1979). No gross or micro-
scopic lesions were observed in fish during the first week of exposure. After
the first week, ascites developed in 3 fish at 21 ppm and in 2 fish at 10 ppm. In
exposed fish that survived 15 to 30 days, about 50$ had a white epidermal exudate
of unknown origin, and some fish at all toluene concentrations had gross lesions
in gill, liver, or gall bladder. Excessive mucus production in gills occurred in
17-20
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all fish at 21 and 10 ppm and in 50% of the fish at 5 ppm. Microscopic lesions
were found in gills (fusion), liver (decreased cytoplasmic nuclear ratio), and
kidney (tubular vacuolization) of many exposed fish but not in control fish.
Exposed fish did not eat food and had livers which were paler and smaller than
control fish.
For the blood gas study, groups of 3 or 4 fish were exposed for 4 hours to 0,
60, or 80 ppm toluene (Brenniman ^_t al., 1979). The blood samples were analyzed
for pH, percent oxygen saturation, partial pressures of carbon dioxide (prn ) and
co2
oxygen (pn ), and bicarbonate. The results are presented below:
°2
Mean Values
Toluene Cone.
(ppm)
0
60
80
\
M2. 33a
I6.25a
15.63a
Pco2
11.50
23.25a
19.27
pH
7.56
6.90a
6.96a
05 -Saturation
£ V,* )
48.67
27.00a
20.33a
Bicarbonate
9.83
5.10
4.17a
P < 0.05 when compared to control.
Toluene exposure caused significant changes in all parameters (Brenniman
et al., 1979). The authors suggested that the decreased p0 , increased p,,,. , and
°2 C02
resultant acid-base imbalance may have been due to lowered 0. and C0_ exchange at
the gills. Two proposed mechanisms for impaired gas exchange were lowered
respiratory rate and gill damage. The former mechanism is less likely because
sublethal toluene exposure has been shown to increase the respiratory rate in
fish (Slooff, 1978, 1979; Thomas and Rice, 1979). The latter mechanism is
supported by the authors' observation that toluene caused excess mucus produc-
tion and fusion of gill lamellae in gills.
The whole-fish content of hippuric acid was measured in fish exposed in
groups of 6 fish to 0, 5, 10, or 21 ppm toluene for 96 hours (Brenniman et al.,
17-21
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1979). This experiment was conducted to determine whether the fish were able to
metabolize toluene ultimately to hippuric acid, as occurs in mammals (Section
12.). The results, presented below, indicated that hippuric acid was elevated at
all the toluene concentrations tested and that this metabolic pathway occurs in
goldfish.
Toluene Concentration Mean Hippuric Acid Concentration
(ppm) (ppm)
0 . 1539.50
5 3608.67a
10 3536.67a
21 2829.17a
P < 0.05 when compared to control.
The pattern of decreasing hippuric acid concentration with increasing toluene
concentration was attributed to increasing stress and lower metabolic efficiency
as toluene concentration increased. Hippuric acid was elevated above the control
levels, however, even at the highest toluene concentration.
The only other information available relevant to toluene metabolism in fish
is provided by Ohmori e_t al. (1975), who investigated the comparative in vitro
metabolism of a toluene analog, p_-nitro toluene, by liver homogenates of rats and
eels. The species of eel was not specified. Both species were able to metabo-
lize £-nitrotoluene (PNT) to £-nitrobenzoic acid (PNB acid), via oxygenation of
PNT to £-nitrobenzyl alcohol (PNB alcohol), to £-nitrobenzaldehyde (PNB alde-
hyde), and finally to PNB acid. The rate of the overall reaction (PNT to PNB
acid) in eel liver, however, was only 34$ (at 25°C) to 46$ (at 37°C) of the rate
in rat liver. The rate of formation of PNB alcohol from PNT in eel liver was 29%
(at 25°C) to 16$ (at 37°C) of the rate in rat liver. This step was the rate-
limiting step for the overall reaction because the formation of PNB acid from PNB
alcohol was faster in eels than in rats.
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Thomas and Rice (1979) measured the effects of flow-through toluene expo-
sure on the respiratory rate and oxygen consumption of pink salmon (Oncorhynchus
gorbuscha) fry at two temperatures (4°C, 12°C) in seawater. The fish were placed
in sealed chambers fitted with a water inlet and outlet, mesh electrodes (for
measuring opercular breathing rate), and oxygen electrodes (for measuring oxygen
concentration of inflowing and outflowing water). After determining the 24-hour
LC50 (5.38 ppm), the authors exposed fry to several toluene concentrations,
expressed as percentages of the LC50. Significant increases in opercular breath-
ing rate at 12°C occurred at exposure concentrations of 94$ and 69? of the LC50,
but not at 45? or 30? of the LC50. The breathing rate remained elevated through-
out the 15-hour exposure period only at 94? of the LC50, at which concentration 6
of 23 fish died. The breathing rate at a toluene exposure concentration of 69?
of the LC50 reached a maximum at 3 hours and returned to control level by
15 hours. Additional experiments showed that exposures to 71? of the LC50
increased oxygen consumption. The percent increase in both oxygen consumption
and breathing rate was greater at 4°C than at 12°C. The authors suggested that
these effects were due to the energy requirements for metabolism of toluene and
that this requirement was greater at the lower temperature. The threshold for an
effect on breathing rate at 12°C was estimated to be about 46? of the LC50, or
about 2.5 ppm.
Slooff (1978, 1979) conducted similar experiments to determine the sensi-
tivity of a biological monitoring system using fish respiratory rates as an
indicator of water pollution by toluene and other chemicals. Adult rainbow trout
(mean weight 56 g) were acclimated to dechlorinated tapwater at 20 + 1°C and
tested individually in sealed flow-through chambers equipped with stainless
steel mesh electrodes for measuring breathing rate. After the normal breathing
rate for a fish over a 3-day period had been determined, toluene-contaminated
17-23
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water was added continuously and the breathing rates were monitored over a period
of 48 hours. Measurements were taken at the same time of day during the pre-
exposure and exposure periods. A toxic effect was considered to have occurred if
the respiration frequency of at least 75$ of the test fish exceeded the prede-
termined individual normal frequencies measured at the same hourly interval. The
lowest toluene concentration that caused an increase in respiratory rate was
2.5 mg/i. This concentration is identical to the estimated threshold concentra-
tion for an effect on breathing rate in pink salmon' (Thomas and Rice, 1979).
Leung and Bulkley (1979) investigated the effects of 100 yl/1 toluene on the
rate of opercular movement by 8-day old embryos of the Japanese medaka, Oryzias
medaka. The basal (unexposed) rate was determined for each of 3 embryos and then
toluene was added to the culture medium to obtain a nominal concentration of
100 ul/1. The rate was then determined for each embryo at about 5-minute inter-
vals for 10 minutes. The average rate before exposure was 0 movements/minute.
The average of 8 counts (each 1 minute long) over 40 minutes after beginning
exposure was 2.28 movements/minute. The standard deviation was so great,
however, that this increase was not statistically significant.
The sublethal effects of toluene on medaka were also investigated by Stoss
and Haines (1978). The exposure techniques and lethal effects reported by these
authors have been discussed in Subsection 17.3.1.1. Static exposure of eggs to
initial nominal concentrations of 41 and 82 mg toluene/1 resulted in a signifi-
cant delay in time to hatching and a decrease in the proportion of embryos that
hatched successfully. Exposure to 41 mg/1 and greater caused numerous develop-
mental abnormalities, including disruption of cell cleavage patterns, defor-
mation of eyes, appearance of isolated blood islands in the circulatory system,
and abnormal heart structure, tail flexures, and visceral organ formation and
placement. No abnormalities were observed in embryos exposed to 16 mg toluene/1.
17-24
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The only other information available concerning sublethal toluene effects
on fish is provided in a U.S. EPA unpublished study (1978, cited in U.S. EPA,
1980). An embryo-larval subchronic test with the sheepshead minnow (Cyprinodon
variegatus) in seawater showed that toxic effects were observed at a toluene
concentration of 3.2 ppm, but not at 7.7 ppm. The type(s) of toxic effects were
not specified in the U.S. EPA (1980) report, which was simply a data compilation.
The 96-hour LC50 for this species was between 277 and 485 ppm (Subsection
17.3.1.2). The application factor between acute and sub-chronic toxicity was
between 36 and 152.
17.3.2.2 Invertebrates
Berry gt al. (1978) conducted a series of experiments to determine the
effects of 24 hours of exposure to sublethal concentrations of water-soluble
fractions (WSFs) of gasoline, benzene, xylenes, and toluene on oxygen consump-
tion by fed and unfed larval stages of the mosquito, Aedes aegypti. Control
experiments with untreated animals showed that there was no significant dif-
ference in Op consumption between fed and unfed larvae. Treatment with the WSF
of 1 ml/1 gasoline, however caused an increased 02 consumption in fed, but not
unfed, larvae relative to untreated controls. Treatment of fed larvae with
individual WSFs of benzene (1 ml/1), xylenes (0.3 ml/1), or toluene (0.1-
0.5 ml/1) had no effect on 0? consumption relative to fed controls. A WSF
mixture of benzene, xylenes, and toluene and a mixture of benzene and toluene
(0.2 ml/1 for each compound) caused significant increases in 0? consumption.
Exposure to a WSF mixture of benzene and xylenes or toluene and xylenes (0.2 ml/1
for each compound) had no effect. The authors also conducted experiments on the
uptake of H-labeled toluene in fed and unfed animals, as well as uptake of H-
toluene by fed larvae in the presence or absence of benzene (Subsection 15.3).
Maximum H-toluene counts were equal in fed and unfed larvae, but were reached
17-25
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more quickly (1 hour versus 4 hours) by the fed animals. The H-toluene counts
in larvae, expressed as the percentage of the initial water counts, were greater
in the benzene and toluene mixture than in the solution containing toluene alone.
The authors concluded that the effects of gasoline on 0,, consumption were due to
the enhanced uptake and synergistic effects of toluene and benzene, two of the
major aromatic components of gasoline. They also suggested that the presence of
food accelerated the uptake of toluene through absorption of toluene to the
consumed food particles.
Blundo (1978) investigated the effects of toluene on the swimming activity
and survival of barnacle (Balanus eburneus) larvae. Groups of larvae were
exposed for 1 hour in specially constructed tubes to 10, 20, 30, 40, 50, 60, 70,
80, and 90$ of the water soluble fraction (WSF) made by saturating seawater with
toluene. The tubes were designed so that actively swimming photopositive larvae
would be attracted to light at the top of the tube. After 1 hour of exposure, the
inactive larvae were collected from the bottom of the tubes and stained with a
vital dye (neutral red) to determine percent mortality. The remaining portion,
containing the active larvae, was then collected and counted. The interpolated
concentration that immobilized 50$ of the larvae was 12.5$ of the WSF. All
larvae were immobilized at 30$ WSF and higher. About 33-1/3$ of the larvae were
immobilized at 10$ WSF, the lowest concentration tested. The percent mortality
of the immobilized larvae ranged from about 3$ at 10$ WSF to a maximum of 12$ at
90$ WSF. The author also measured the effects of WSFs that had been aged in
covered containers for 1 day in a refrigerator or exposed to air for up to
3 days. The percent WSF that immobilized 33-1/3$ of the larvae was 10$ in the
fresh solution, 37.5$ in the refrigerated solution, and 90$ in the evaporated
solution. Additional experiments showed that aeration of the WSF for 6 hours
lowered the toxicity to the same extent as 3 days of exposure to air.
17-26
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Bakke and Skjoldal (1979) investigated the effects of toluene on activity,
survival, and physiology of the isopod, Cirolana borealis. For determination of
median effective times (ET50, partial or complete narcotization as endpoint),
groups of 15 isopods were exposed in duplicate to nominal initial concentrations
of 0, 0.0125, 1.25, 5.7, 12.5, 25, and 125 ppm toluene for 4 days. The exposure
medium (33.5-34.5 °/oo salinity seawater at 8-10°C) was changed every 2 days.
The interpolated or extrapolated ET50 values were as follows:
Toluene
Concentration ET50
(ppm) (hours)
0
0.0125
1.25
5.7 400
12.5 69
25 28
125 3
No effects on activity were observed in animals exposed to 1.25 ppm or less
(Bakke and Skjoldal, 1979). The authors also investigated the recovery of
isopods after exposure for varying periods to 12.5 or 125 ppm toluene. Exposure
to 125 ppm for 1 hour caused complete inactivity, but all animals recovered
within 12 hours after transfer to clean water. Exposure for 2 or more hours to
125 ppm caused partial or complete mortality. All isopods could recover after
exposure to 12.5 ppm for 30 hours but not longer. Additional experiments showed
that there was no significant effect of 4 days of exposure to up to 5.7 ppm
toluene on oxygen consumption, ATP concentration, or energy charge. Exposure to
12.5 ppm resulted in a progressive decrease in ATP level and energy charge over
8 days of exposure, at which time all organisms had died. Exposure to the
rapidly lethal concentration of 125 ppm toluene showed no effect on ATP level or
energy charge. These results with 12.5 and 125 ppm were essentially the same as
those reported by the authors in a previous paper (Skjoldal and Bakke, 1978).
17-27
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Bakke and Skjoldal (1979) concluded that the effect of toluene on activity was
much more sensitive as an indicator of sublethal toluene toxicity than its
effects on respiration, ATP level, and energy charge.
17-28
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18. HUMAN RISK ASSESSMENT
18.1 EXISTING GUIDELINES AND STANDARDS
18.1.1 Air
The Occupational Safety and Health Administration (OSHA) currently limits
occupational exposure to toluene to 200 ppm as an 8-hour time-weighted average
(TWA), with an acceptable ceiling concentration of 300 ppm (40 CFR 1910.1000);
the acceptable maximum peak above the ceiling concentration is 500 ppm for a
maximum duration of 10 minutes. The National Institute for Occupational Safety
and Health (NIOSH, 1973) currently recommends an exposure limit of 100 ppm as an
8-hour TWA with a ceiling of 200 ppm. An 8-hour TWA concentration of 100 ppro is
also recommended by the American Conference of Governmental Industrial
Hygienists (ACGIH, 1980) as a Threshold Limit Value (TLV) for toluene; the short-
term (15-minute) exposure limit recommended by the ACGIH is 150 ppm. ACGIH
(1980) has further noted that there may be significant contribution to the
overall exposure by the cutaneous route.
Threshold limit values that have been established for occupational exposure
to toluene in other countries are listed as follows (Verschueren, 1977):
USSR 13 ppm (50 mg/m3) 1972
Czechoslavakia 52 ppm (200 mg/nr) 1969
West Germany (BDR) 200 ppm (750 mg/m3) 1972*
East Germany (DDR) 52 ppm (200 mg/n£) 1973
Sweden 98 ppm (375 mg/m3) 1975
There are no standards for general atmospheric pollution by toluene in the
United States, although a National Ambient Air Quality Standard specifies that
nonmethane hydrocarbons shall not exceed 0.24 ppm (160 ug/nr) as a maximum
3-hour average concentration (6-9 a.m.), more than once per year (40 CFR 50).
Ambient air quality standards have, however, been promulgated for toluene in
other countries. These foreign standards are summarized as follows:
18-1
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Country
USSR
West Germany (BRD)
East Germany (DDR)
Bulgaria
Hungary
Hungary (protected areas)
Yugoslavia
Concentration
0.15 ppm (0.6 mg/n£)
0.15 ppm (0.6 mg/nr)
15 ppra (60 mg/nr)
5 ppm (20 mg/nr)
0.5 ppm (2.0 mg/nr}
0.15 ppm (0.6-mg/nr)
0.15 ppm (0.6 mg/nn)
0.15 ppm (0.6 mg/nr)
13.3 Ppm (50.0 mg/in^)
5.3 ppm (20.0 mg/nr)
0.16 ppm (0.6 mg/nn)
0.16 ppm (0.6 mg/nr)
0.16 ppm (0.6 mg/m^)
0.16 ppm (0.6 mg/m )
Averaging Time
20 min
24 hr
30 min
24 hr
30 min
24 hr
20 min
24 hr
30 min
24 hr
30 min
24 hr
20 min
24 hr
18.1.2 Water
The Committee on Safe Drinking Water of the National Academy of Sciences
concluded in 1977 that toluene and its major metabolite, benzoic acid, were
relatively nontoxic, and that there was insufficient toxicological data avail-
able to serve as a basis for setting a long-term ingestion standard (NAS, 1977).
It was recommended that studies be conducted to produce relevant information.
Toluene has recently been considered for a second time by a reorganized Toxi-
cology Subcommittee of the Saf ty Drinking Water Committee of the National Academy
of Sciences (U.S. EPA, 1980), but the results of the deliberations of this group
have not yet been made public.
The U.S. EPA (1980) has recently derived an ambient water criterion level
for toluene of 14.3 mg/1. This criterion is intended to protect humans against
the toxic effects of toluene ingested through water and contaminated aquatic
organisms, and is based on an ADI calculated from the maximum-no-effect dose
reported in the Wolf _et al. (1956) subchronic oral study in rats and an uncer-
tainty factor of 1000. The criterion level for toluene can alternatively be
18-2
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expressed as 424 mg/1 if exposure is assumed to be from the consumption of fish
and shellfish products alone.
18.1.3 Food
Toluene has been approved by the Food and Drug Administration for use as a
component of articles intended for use in contact with food (i.e., an indirect
food additive). Articles that contain residues of toluene may be used in produc-
ing, manufacturing, packing, processing, preparing, treating, packaging, trans-
porting, or holding food. The use of toluene in the food industry is summarized
as follows:
Component of adhesives 21 CFR 175.105
Adjuvant substance in resinous and
polymeric coatings for polyolefin films
used as food contact surfaces 21 CFR 175.320
Component of the uncoated or coated
surfaces of paper and paperboard
articles intended for use with
dry foods 21 CFR 176.180
Used in the formulation of semirigid
and rigid acrylic and modified acrylic
plastic articles 21 CFR 177.1010
Additive for cellophane (residue limit
0.1%) 21 CFR 177.1200
Additive for 1,4-cyclohexylene dimethy-
lene terephthalate and 1,4-cyclo-
hexylene dimethylene isophthalate
copolymer 21 CFR 172.1240
Solvent for 4,4'-isopropylidenediphenol-
epichlorohydrin resins with a minimum
molecular weight of 10,000 (residue
limit <_1000 ppm in the finished resin) 21 CFR 177.1440
Solvent for polysulfide polymer-polyepoxy
resins 21 CFR 177.1650
Solvent for poly(2,6-dimethyl-1,4-
phenylene)oxide resins (residue limit
0.2% by weight) 21 CFR 177.2460
18-3
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Blowing agent adjuvant used in the manu-
facture of foamed polystyrene (residue
limit <_0.35$ by weight of finished
framed polystyrene) 21 CFR 178.3010
Toluene has also been exempted from the requirement of a tolerance when it
is used as a solvent or cosolvent in pesticide formulations which are applied to
growing crops (40 CFR 180.1001).
18.2 INHALATION EXPOSURES
As detailed in Section 11 of this report, many studies have reported the
effects on humans of inhalation exposures to toluene. Because most of these
studies involved relatively small numbers of human subjects, failed to precisely
define the levels or durations of the exposures, and/or did not consider the
potential role of exposures to other toxicants, none of these studies would be
suitable for human risk assessment if taken individually. In combination,
however, they constitute a considerable body of human experience and provide a
relatively consistent pattern of dose-response relationships. Although acute
and subchronic inhalation studies on experimental animals are available, the
uncertainties inherent in extrapolating from experimental mammals to human popu-
lations outweigh the benefits of the controlled nature of these studies.
18.2.1 Effects of Single Exposures
The effects on humans of single exposures to toluene for periods of up to
8 hours are relatively well documented. Data on both toluene glue sniffers
(Press and Done, 1967a, 196?b; Wyse, 1973; Lewis and Patterson, 1974; Helliwell
and Murphy, 1979; Hayden et jal., 1977; Oliver and Watson, 1977; Barnes, 1979) and
workers accidentally exposed to high levels of toluene (Lurie, 1949; Anderson and
Kaada, 1953; Browning, 1965; Longley et al., 1967; Reisen^tal., 1975) indicate
that exposure to air saturated or nearly saturated with toluene can cause a
spectrum of effects, from lightheadedness to unconsciousness, in a very short
period of time. Deaths attributed to the deliberate inhalation of toluene have
18-4
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been reported in at least 24 cases (Winek e_t al., 1968; Chiba, 1969; Nomiyama and
Nomiyama, 1978). Although most of these reports do not provide quantitative
exposure estimates, glue sniffers are probably exposed to nearly saturated air-
vapor mixtures of about 30,000 ppm toluene. The occupational report of Longley
£t _al. (196?) indicated that a loss of consciousness occurred within minutes
after exposure to atmospheres estimated to contain 10,000 ppm toluene at waist
level and 30,000 ppm toluene at floor level. The acute inhalation toxicity data
on experimental mammals, summarized in Table 12-1, suggest that exposure periods
of several hours to toluene levels greater than 4000 ppm may be lethal. Based on
the results of longer term human studies discus'sed below, short exposures to
concentrations of up to 1500 ppm are not likely to be lethal (Wilson, 1943; Ogata
_et al., 1970 —see following discussion). The single report by Gusev (1965) of
effects on EEC activity in 4 individuals exposed to 0.27 ppm for 6-minute inter-
vals may be a subtle indication of the perception of toluene at this low level
but does not have any apparent toxicologic significance.
For single exposure periods that approximate a normal working day
(7-8 hours), von OettLngen .et al. (1942a, 1942b) and Carpenter et al. (1944)
provide relatively consistent information on sublethal dose-response relation-
ships. As summarized previously in Table 10-1, von Oettingen e_t al. (1942a,
1942b) noted a range of subjective complaints from 8-hour exposures to toluene
concentrations ranging from 50 ppm (drowsiness) to 800 ppm (severe fatigue,
nausea, incoordination, etc., with aftereffects lasting at least several days).
Although the terminology used by Carpenter e_t al. (1944) is somewhat different
from that used by von Oettingen, the effects noted seem comparable over the
common exposure range (200 ppm to 800 ppm). Although the consistency between
these two studies is reassuring, it should be noted that even combined both
studies involve exposures of only 5 individuals who were placed on multiple
18-5
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exposure/recovery schedules. The impact that such multiple exposures could
potentially have on the results cannot be determined. Given the small number of
individuals involved in the exposures to toluene, an attempt to generalize for
the human population a detailed dose-response gradient comparable to that pre-
sented in Table 11-1 does not seem justifiable. When these studies are con-
sidered along with the results of Ogata and coworkers (1970) and Gamberale and
Hultengren (1972), however, it seems reasonable to conclude that exposure
periods of 8 hours or less to toluene concentrations below 100 ppm may result in
mild subjective complaints (fatigue or headache) but are not likely to induce
observable effects. Concentrations above 100 ppm may cause impaired reaction
time (200 ppm x 3 hours, Ogata £t jl., 1970; 300 ppm x 20 minutes, Gamberale and
Hultengren, 1972). At concentrations of 300-800 ppm and above, gross signs of
incoordination may be expected (von Oettingen _et _§!., 1942a, 1942b; Carpenter
£t al., 1944).
Accidental acute overexposure to toluene may be limited to some extent by
the organoleptic or irritant properties of the compound. Gusev (1965) reports
ranges of maximum imperceptible concentrations and minimum perceptible concen-
trations of 0.35-0.79 ppm and 0.40-0.85 ppm, respectively. May (1966) reports a
mimimum perceptible concentration of 37 ppm. The reasons for this discrepancy
between the Russian and American values are not apparent. Although the Russian
study entailed a total of 30 subjects and 744 observations and the American
report involved 16 individuals (number of observations not specified), it is
unlikely that the difference in the reported detectable levels is due simply to
sample size. In any event, toluene appears to be detectable in the air at levels
below those causing impaired coordination (i.e., >100 ppm). In addition,
Carpenter and coworkers (1944) reported that toluene caused mild throat and eye
irritation at 200 ppm and also caused lacrimation at 400 ppm.
18-6
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In summary, the estimated dose-response relationships for the acute effects
of single short-term exposures to toluene are presented below:
10,000-30,000 ppm : Onset of narcosis within a few minutes. Longer
exposures may be lethal.
>4,000 ppm : Would probably cause rapid impairment of reaction
time and coordination. Exposures of 1 hour or
longer might lead to narcosis and possibly death.
1,500 ppm : Probably not lethal for exposure periods of up to
8 hours.
300-800 ppm : Gross signs of incoordination may be expected
during exposure periods up to 8 hours.
HOO ppm : Lacrimation and irritation to the eyes and throat.
100-300 ppm : Detectable signs of incoordination may be expected
during exposure periods up to 8 hours.
200 ppm : Mild throat and eye irritation.
50-100 ppm : Subjective complaints (fatigue or headache) but
probably no observable impairment of reaction time
or coordination.
>37 ppm : Probably perceptible to most humans.
From the above discussion, it should be evident that these approximations are
crude composites and contain several areas of uncertainty and overlap.
18.2.2 Effects of Intermittent Exposures over Prolonged Periods
Limited information is available on the effects of subchronic or chronic
continuous exposures to toluene on humans or experimental animals. Most of the
studies either involve occupational exposures or are designed to mimic occupa-
tional exposures. Consequently, while the data described below may be directly
applicable to estimating effects from occupational exposures, an additional ele-
ment of uncertainty must be considered in any attempt to estimate the effects of
continuous exposures that may occur from ambient air.
18-7
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One of the more striking features of the data on the subchronic and chronic
effects of toluene exposure on humans is the failure of increased periods of
intermittent exposures to cause clearly increasingly severe effects. Although
the utility of the available studies for estimating firm dose-response relation
ships is somewhat limited by the failure to define precisely levels and durations
of exposure, problems of sample sizes, the potential role of other toxic agents
in eliciting the reported effects, and some apparent inconsistencies among the
available studies, the weight of the evidence suggests that the types of effects
seen and the levels at which these effects are seen are relatively independent of
the duration of exposure.
Wilson (1943) provides the only acceptable data on the effects of repeated
occupational exposures to toluene over a period of weeks (Section 11.1.1.2). In
this study, the workers were classified into three groups by the levels of
toluene to which they were exposed: 50-200 ppm, 200-500 ppm, and 500-1500 ppm.
The effects noted at the various levels were essentially the same as those seen
in single exposures. In the low exposure group, the reports of headache and
lassitude are consistent with symptoms noted by von Oettingen and coworkers
(1942a, 1942b) over the same range of exposure. Although Wilson (1943) did not
attribute these effects to toluene exposure, his failure to include an unexposed
control group makes this judgment questionable in view of the von Oettingen data.
In the middle and high exposure groups, the reports of headache, nausea, and
concentration-related impairment of coordination and reaction time are also con-
sistent with the symptoms reported by von Oettingen and coworkers (1942a, 1942b)
and Carpenter and coworkers (1944). The major discomforting feature of the
Wilson (1943) report is that it involved only 100 out of a total of 1000 workers.
It is unclear whether the remaining 900 workers evidenced any symptoms of toluene
exposure.
18-8
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The only other study that reports effects of repeated exposures to toluene
for relatively short periods of time is that presented by Greenburg and coworkers
(1942). In this study, repeated occupational exposures to toluene at levels of
100-1100 ppm for periods of 2 weeks to 5 years were associated with enlarged
livers in 13 of 61 airplane painters. This incidence of liver enlargement was
reported to be 3 times that of a control group of 430 workers not exposed to
toluene. Because Greenburg and coworkers (1942) were not able to associate liver
enlargement with clinical evidence of liver disease, because the painters were
also exposed to significant quantities of other volatile paint components
(Table 11-9), and because the liver effect has not been corroborated by other
investigators (e.g., Parmeggiani and Sassi, 1954; Suhr, 1975), the hepatomegaly
reported by Greenburg should be given relatively little weight in risk assess-
ment.
Other reports of repeated occupational exposures to toluene involve periods
of several years. For mean exposure levels above 200 ppm, all of the available
studies except that of Suhr (1975) report some evidence of neurologic effects
(Capellini and Alessio, 1971; Parmeggiani and Sassi, 1954; Munchinger, 1963;
Rouskova, 1975).
The Suhr (1975) study involved a group of 100 printers exposed to
200-400 ppm toluene for over 10 years. Compared to a group of 100 non-exposed
individuals, no significant differences were seen in symptoms of central nervous
system (CNS) depression or Sphallograph tests, which are designed to measure
muscular coordination. An interpretation of the significance of the Suhr (1975)
study is confounded, however, by several factors. As discussed in Sections
11.1.1.2 and 11.3, the limitations of this studdy include an undefined control
group, uncertainties involving the time of reflex reaction and sphallograph
testing (i.e., blood toluene levels may have declined significantly if the
18-9
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workers were examined before or after the work shifts), and the use of an
apparently unvalidated device (sphallograph) for the detection of slight distur-
bances of muscular coordination.
The other studies that do report effects at equal or higher levels of
exposure can be challenged for various reasons. The report of "nervous hyper-
excitability" in 6 of 11 exposed to 200-800 ppm toluene for "many years"
(Parmeggiani and Sassi, 1954) does not seem to be characteristic of toluene
intoxication. This report is from the Italian literature, however, and a full-
text translation has not yet been made available for this review. The Capellini
and Alessio (1971) study, which associated stupor, nervousness, and insomnia
with occupational exposure to 250 (210-300) ppm toluene for several years,
involved only a single worker. The "organic psychosyndrome" diagnosed by
Munchinger (1963) in workers exposed to 300 and 430 ppm toluene for 18 and
12 years, respectively, is supported by the results of Rorschach tests and
Knoepfel's 13-Error tests. Because Munchinger did not use a control group,
however, the utility of this study is limited. The changes in EEC response to
photic stimulation that were reported by Rouskova (1975) in workers exposed to
>250 ppm toluene for an average of 13-5 years also involved exposure to unspeci-
fied levels of 1,1,1-trichloroethane. Thus, the interpretation of the dis-
crepancies between the study by Suhr (1975) and these other reports is problema-
tic. Considering the relatively well-documen ted CNS effects of single exposures
to toluene at levels above 200 ppm (Section 18.1.1) and the effects noted by
Wilson (1943) at comparable levels for much shorter periods of time, however, it
would seem imprudent to accept the Suhr (1975) data as a "no-observed-effect
level" for human risk assessment.
An alternative approach could be to use the study by Capellini and Alessio
(197D in which no CNS or liver effects were noted in a group of 17 workers
18-10
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occupationally exposed to 125 (80-160) ppm toluene for "diverse years." In
addition to the problems of small sample size, failure to precisely define the
duration of exposure, and lack of a control group, however, the use of this study
is compromised by reports of effects in two other groups of workers at lower
levels of toluene exposure. Matsushita and coworkers (1975) reported impaired
performance in neurological and muscular function tests in a group of 38 female
shoemakers who had been exposed to 15-200 ppm toluene for an average of 3 years
and 4 months. In addition, 19 of 38 exposed women, compared to 3 of 16 in the
control group, complained of dysmenorrhea. The second group of workers was
composed of 100 car painters who had been occupati'onally exposed to an average of
30.6 ppm toluene for an average of 14.8 years. As reported by Hanninen and
coworkers (1976) and Seppalainen and coworkers (1978), the exposed workers had a
greater incidence of CMS symptoms and impaired performance on tests for intelli-
gence and memory, as well as for visual and verbal ability. Both of the studies
on this group of workers used control groups of approximately 100 unexposed
individuals. The major problem with the reports of adverse effects on the female
shoemakers and male car painters is that both groups were exposed to other
potentially toxic agents. The female shoemakers were exposed to "slight" levels
of gasoline (Matsushita et _al., 1975) and, as detailed in Table 11-3, the male
car painters were exposed to several other organic solvents.
The subchronic and chronic data on experimental mammals are of only limited
use in helping to resolve the uncertainties in the human data. Jenkins and
coworkers (1970), and CUT (1980) report no-observable-effect levels (NOELs) in
experimental mammals 1085 ppm (8 hours per day, 5 days per week for 6 weeks) and
300 ppm (6 hours per day, 5 days per week for 24 months), respectively. For
reasons discussed in detail in Section 12.1.2, the CUT study is not considered
appropriate for human risk assessment; interpretation of this study is compli-
18-11
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cated by the absence of quality assurance throughout the study and the use of an
inparropriate strain of rats for study of myelotoxicity. As discussed above in
this section, a NOEL of 1085 ppm is contradicted by human experience, suggesting
that humans are more sensitive than experimental mammals to toluene exposure.
Similarly, the continuous-exposure NOEL of 107 ppm for 90 days in rats, guinea
pigs, dogs, and monkeys (Jenkins ^t al., 1970) does not, in itself, negate the
concerns with effects reported in humans at lower levels.
18.1.3 Acceptable Daily Intake (ADI) Based on Inhalation Exposure
Given the uncertainties detailed above in the data on the effects of long-
term toluene exposure on humans and experimental "animals, the reported NOELs in
both humans and experimental animals must be regarded with caution in attempting
to estimate an ADI for intermittent (occupational) or continuous (environmental)
exposures.
The American Conference of Governmental Industrial Hygienists (ACGIH)
(1979) has set the Threshold Limit Value (TLV) for toluene at 100 ppm which is
the same as the NIOSH criteria and OSHA has adopted a standard of 200 ppm;
however, both the acute data on humans provided by von Oettingen and coworkers
(19^2a; 19^2b) as well as the suggestive, if equivocal, data on occupational
exposures near or below 100 ppm (Matsushita e_t _al., 1975; Hanninen e_t ^1., 1976;
Seppalainen j3t _al., 1978) suggest that these values have little, if any, margin
of safety. Nonetheless, given the reported human NOELs above 100 ppm (Suhr,
1975; Capellini and Alessio, 1971) and the continuous subchronic exposure NOEL
for experimental animals at 107 ppm (Jenkins jst al., 1970), the TLV can be used,
albeit somewhat arbitrarily, as an equivocal NOEL for humans in deriving an ADI.
Because of the uncertainty of this value, a safety or uncertainty factor should
be applied following the guidelines of the National Academy of Sciences (NAS,
1977) as recently expanded by the U.S. EPA (1980c). The use of these safety
18-12
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factors for deriving acceptable limits of exposure to air pollutants has recently
been proposed by Kim (1981) and Su and Wurzel (1981).
Based on all of the available toxicity information, reasonable arguments
could be made for using uncertainty factors ranging from 5 to nearly 100. An
uncertainty factor of 5 would put the presumed safe occupational exposure level
at 20 ppm, only 10 ppm below the lowest reported observed-effect level (i.e.,
30 ppm: Hanninen e_t al., 1976; Seppalainen et al., 1978). The uncertainty
factor of 5 could be defended because the 30-ppm" effect level also involved
exposure to several other known toxic agents. A safety factor of 100 would give
considerable weight to the reported human effects below 100 ppm and to the fact
that the carcinogenic and teratogenic potential of toluene has not been ade-
quately investigated (Section 18.U). Although the uncertainty factor of 100
would certainly be protective of CNS impairment or other toxic effects, it could
easily be challenged as overly conservative. The weight of the evidence suggests
that an uncertainty factor of 10 would be protective for most individuals and is
consistent with the general approach for applying uncertainty factors recom-
mended by the National Academy of Sciences (1977).
Using an uncertainty factor of 10, the ADI for humans based on inhalation
data could be estimated at 2.69 mg/kg body weight, using a modification of the
Stokinger and Woodward (1958) approach where:
TLV x BR x AC
AUi = UF x BW
TLV = Threshold Limit Value, 100 ppm = 377 mg/m
BR = Cubic meters of air breathed per workday = 10 m
UF = Uncertainty Factor
BW = Human Body Weight = 70 kg
AC = Absorption Coefficient = 0.50
18-13
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Here, the absorption coefficient of 0.5 was taken as the approximate mid-range of
retention values reported by Ovrum and coworkers (1978) and Carlsson and
Lindqvist (1977). As detailed in Section 13, the absorption coefficient is not a
true pharmacokinetic parameter and varies with period of exposure and level of
activity. The absorption coefficient is used here only to obtain a reasonable
approximation of the ADI.
As discussed in the beginning of Section 18.2.2, the ADI derived above is
applicable to intermittent occupational exposures that are assumed to occur
5 days per week. Spreading the ADI over a 7-day per week exposure yields an ADI
•3
of 1.92 mg/kg/day. Assuming that humans breathe a total of 24 m per day, an
equivalent ambient air level can be estimated to be 2.98 ppm or 11.2 mg/m
(100 ppm/10 x 5/7 x 10/24). Because toluene is rapidly absorbed and rapidly
eliminated on inhalation exposures, this simplistic derivation of a "safe"
ambient air level should be regarded with skepticism and is at best a crude
approximation. Given the known pharmacokinetic patterns of toluene and its
apparent lack of cumulative toxicity, a safe ambient air level may be substan-
tially higher. Conversely, given the paucity of actual data on continuous
exposures, an upward adjustment of this "safe" ambient air level does not seem
prudent.
18.3 ORAL EXPOSURES
Very little information is available on the acute, subchronic, or chronic
effects of toluene in experimental mammals. As summarized in Table 12-1, acute
oral LD50s in adult rats range from 5500 mg/kg to 7530 mg/kg. Using the cubed
root of the body weight ratios for interspecies conversion (U.S. EPA, 1980c;
Freireich ejt _al., 1966; Rail, 1969), an approximate lethal dose for humans can be
1 /^
estimated at 983 mg/kg (5500 mg/kg -f (70 kg T 0.4 kg) J). The conversion
factor, as used here, assumes that humans are more sensitive than rats, which, as
18-14
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discussed above, is consistent with the available data on inhalation exposure.
This estimate of the approximate lethal dose is also consistent with the report
by Francone and Braier (1954) that leukemia patients were able to tolerate
cumulative doses of up to 130,000 rag of toluene given over a 3-week period
(approximately 88 mg/kg/day).
The only subchronic oral data are reported in the study by Wolf and
coworkers (1956), indicating a NOEL in rats at 590 mg/kg/day, given five days per
week for six months. An ADI could be derived from this study by averaging the
five-day dose over a several day week and using an uncertainty factor as dis-
cussed above. Given the scant data available on oral exposures, the uncertainty
of route-to-route as well as species-to-species conversions, and the potential
teratogenic effects of toluene (Section 18.5.3), a conservative uncertainty
factor of 1000 seems appropriate. This is identical to the approach taken by the
U.S. EPA in deriving an ambient water quality criterion for toluene. Because the
estimate is based on a free-standing NOEL, the resulting ADI of 0.42 mg/kg or
29-5 mg for a 70 kg human may be more protective than predictive of a toxic
threshold (U.S. EPA, 1980c).
18.4 DERMAL EXPOSURES
Studies on the dermal toxicity of toluene are not adequate for quantitative
risk assessment. Qualitatively, the little information that is available sug-
gests that moderate dermal contact with liquid toluene—i.e., exposure of human
forearm skin to toluene for 1 hour on 6 successive days—may cause skin damage
but does not result in overt signs of toxicity (Mai ten ^_t ^1., 1968). Similarly,
the acute and subchronic data on toluene exposure in experimental mammals do not
suggest that toluene is a potent toxicant on dermal contact. A method for
quantitatively using such data to'estimate equivalent human dose-response rela-
tionships, however, has not been fully formulated or validated. As discussed in
18-15
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Section 13.1, exposure to toluene vapor results in relatively little dermal
absorption compared to absorption across the lungs.
18.5 RESPONSES OF SPECIAL CONCERN
18.5.1 Carcinogenicity
CUT (1980) concluded that exposure to 30, 100,. or 300 ppm toluene for
24 months did not produce an increased incidence of neoplastic, proliferative,
inflammatory, or degenerative lesions in Fischer 344 rats; however, the high
spontaneous incidence (16$) of mononuclear cell leukemia in aging Fischer 3****
male rats has been reported by Coleman and coworkers (1977), suggesting that this
strain may be inappropriate for the study of a chemical that might be myelotoxic.
Other studies suggest that toluene is not carcinogenic when applied topi-
cally to the shaved skin of animals. Toluene is used extensively as a solvent
for lipophilic chemicals being tested for carcinogenic potential; negative
control studies employing 100$ toluene have not elicited carcinogenic effects.
Also, no evidence of a promotion effect was noted when toluene was painted on the
skin of mice twice weekly for 20 weeks following initiation with 7,12-dimethyl-
benz-a-anthracene (Frei and Stephens, 1968; Frei and Kingsley, 1968).
Although the above data are not adequate for assessing the potential carcin-
ogenicity of toluene with great assurance, they are also inadequate for support-
ing carcinogenicity as a valid biologic endpoint in quantitative risk assess-
ment.
18.4.2 Mutagenicity
Toluene has yielded negative results in a battery of microbial, mammalian
cell, and whole organism test systems as indicated in the following:
18-16
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Differential Toxicity/DNA Repair Assays
Escherichia coli
Salmonella typhimurium
Reverse Mutation Testing
Salmonella typhimurium (Ames test)
Escherichia coli WP2 assay
Saccharomyces cerevisiae D7
Mi totic Gene Conversion/Crossing Over
Saccharomyces cerevisiae D4, D7
Thymidine Kinase Assay
L5178Y mouse lymphoma cells
Sister-Chromatid Exchange
cultured CHO cells
human lymphocytes in vitro
human lymphocytes in vivo (workers)
Micronucleus Test
mouse
In the Russian literature, chromosome aberrations were reported in the bone
marrow cells of rats exposed subcutaneously (Dobrokhotov, 1972; Lyapkalo, 1973)
and via inhalation (Dobrokhotov and Einkeev, 1977) to toluene. These findings
were not corroborated in a Litton Bionetics, Inc. (1978b) study in rats following
intraperitoneal injection, in cultured human lymphocytes exposed to toluene
in vitro (Gerner-Smidt and Friedrich, 1978), or in lymphocytes from workers
chronically exposed to toluene (200-400 ppm—Forni ^t al., 19715 7-112 ppm
toluene—Maki-Paakanen e_t al., 1980). Differences in doses employed may
account, at least in part, for these conflicting results. Funes-Cravioto et al.
(1977) did report an excess of aberrations in the lymphocytes from 14 printers
exposed to TWA concentrations of 100-200 ppm for 1-16 years, but it is probable
that part of the exposure was to benzene-contaminated toluene. Also, the number
of workers was small in this study.
18.5.3 Teratogenicity
Toluene was reported in a recent abstract from NIEHS to induce cleft palates
at a level of 1.0 ml/kg (approximately 866 mg/kg) following oral exposure to
18-17
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mice on days 6-15 of gestation (Nawrot and Staples, 1979). This effect
reportedly did not appear to be due merely to a general retardation in growth
rate. Levels of 0.3 and 0.5 ml/kg (approximately 260 and 433 mg/kg) toluene had
no teratogenic effect, but the number of mice exposed and number of fetuses
examined were not stated. Nawrot and Staples .(1979) also noted a significant
increase in embryonic lethality at all dose levels and a significant reduction in
fetal weight at the two higher dose levels. No frank signs of maternal toxicity
were seen at any dose level; however, at the highest dose, decreased maternal
weight gain was reported on days 12 to 15 of gestation. A complete copy of this
report has not been made available for review but has been submitted for publica-
tion.
Three other studies have concluded that toluene is not teratogenic in mice
(Hudak and Ungvary, 1978) or rats (Hudak and Ungvary, 1978; Litton Bionetics,
1978b; Tatrai ^_t al., 1980) following inhalation exposure. Hudak and Ungvary
(1978) and Tatrai e_t _al. (1980) have noted, however, an increased incidence of
skeletal anomalies and signs of retarded skeletal development in the rats that
were not considered malformations as such. Embryotoxicity was also indicated by
low fetal weights in mice and some rats (Hudak and Ungvary, 1978). At the high
exposure levels in the study by Hudak and Ungvary (1978), increased maternal
mortality was noted in rats (399 ppn, 24 hours/day, days 1-8) and mice (399 ppm,
24 hours/day, days 6-13). No increased maternal mortality was noted by either
Hudak and Ungvary (1978) or Tatrai ^t al. (1980) at lower exposure levels in rats
(266 ppm, 8 hours/day, days 1-21 ; 266 ppm, 24 hours/day, days 7-14) or mice
(133 ppra, 24 hours/day, days 6-13). In the study by Litton Bionetics, Inc.
(1978b), no signs of maternal toxicity were noted in rats exposed to 100 or
400 ppm, 6 hours/day, on days 6-15 of gestation.
18-18
-------
The extrapolation of these results to define potential human risk is an
uncertain process. The dose that produced cleft palates in mice on oral expo-
sure, 866 mg/kg, is only slightly higher than the NOEL in rats, 590 mg/kg/day,
from which the ADI is derived. As discussed in Section 18.3, this was one
consideraton in recommending an uncertainty factor of 1000. Because teratogenic
effects were not noted at the two lower dose levels in a study by Nawrot and
Staples (1979), a more conservative approach does not seem justified. Although
this approach may be protective, it is not predictive of levels of human exposure
that might pose a teratogenic or embryotoxic hazard. One possible approach to a
predictive teratogenic/embryo toxic exposure is to again use the cubed root of the
body weight ratios for interspecies conversion (U.S. EPA, 1980c, Freireich
et al.f 1966; Rail, 1969) (see Section 18.3). Assuming a body weight for mice of
0.035 kg and a human female body weight of 55 kg, the dose that might be expected
to induce a teratogenic effect in humans is 74.5 ing/kg (866 mg/kg x (55 kg
x 0.035 kg)1/3) or a total daily dose of about 4100 mg (74.5 mg/kg x 55 kg). As
discussed in the following section, this is much higher than current levels of
human exposure from environmental sources. Although this suggests a substantial
margin of safety, quantitative methods for high-to-low dose or species-to-
species extrapolation for teratogenic chemicals have not yet been validated.
Consequently, the above approach should be considered speculative, at best, and
perhaps superficial.
Although inhalation exposure to toluene have not been shown to be tera-
togenic, embryotoxicity is an endpoint of concern. The effects noted in rats and
mice at the high exposure level (400 ppm) in the study by Hudak and Ungvary
(1978) may be of limited use in human risk assessment because of the occurrence
of maternal mortality. The lowest effect level not associated with maternal
mortality was 133 ppm, 24 hours/day, on days 6-13, which caused low fetal
ia-19
-------
weights in mice. No fetal effects were noted in the study by Litton Bionetics,
Inc. (1978b), however, when rats were exposed to 100 ppm or 400 ppm, 6 hours/day,
on days 6-15 of gestation, or in the Tatrai g_t al. (1980) study when rats were
continuously exposed to 266 ppm toluene on days 7-14. As is the case with oral
exposure studies, a quantitative approach for using this type of data in human
risk assessment has not been validated. Nonetheless, the derived "safe" level
for occupational exposure of 10 ppm seems protective in view of the negative
results of the Litton and Tatrai et al_. (1980) studies. The derived "safe" level
for ambient air, 2.98 ppm, is about 45 times below the lowest effect level on
continuous exposure noted by Hudak and Ungvary (1978). Since the effect noted
was low fetal weight rather than skeletal growth retardation or anomalies, the
margin of safety seems adequate, although it would be desirable to have a no-
effect level for embryo toxic effects on continuous exposures.
18.5 CURRENT POTENTIAL HAZARDS TO HUMANS
The following ADIs have been estimated for humans:
Inhalation: 2.69 mg/kg
10 ppm (37.5 mg/nr) occupational air
2.98 ppm (11.2 mg/nr) ambient air
Oral: 0.42 mg/kg
Dermal: none—probably not highly toxic
As detailed in Section 10 (Tables 10-2, 10-3, and 10-4), the only group at
possible high risk are workers who are exposed to toluene at or near the TLV. The
small or nonexistent margin of safety associated with this TLV has been discussed
in Section 18.1.3.
For non-occupational exposures, the worst-case total daily dose from
Table 10-3 is about 15.5 rug/day or 0.22 mg/kg/day (15.5 x 70), which is not
corrected for incomplete retention of inhaled toluene. Correcting this estimate
by using an inhalation absorption coefficient of 0.5, the estimated worst-case
18-20
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daily dose is 0.11 rag/kg. Thus, compared to the most conservative ADI
(0.42 mg/kg), there is a margin of safety of about four between the ADI and the
current worst-case levels of exposure. This analysis suggests that ambient
exposure to toluene does not currently present a human health hazard given the
known toxic effects of this compound. Although this is reassuring, uncertainties
over the carcinogenic and teratogenic effects of toluene should be a matter of
concern and future research. In addition, dysmenorrhea in female workers
(Matsushita e± _al., 1975), degeneration of germinal epithelium in the testes of
rats (Matsushita £t al., 1971), and increased follicle-stimulating hormone (FSH)
levels in rats (Andersson et al., 1980) have been associated with toluene expo-
sure and suggest that the reproductive effects of this compound should also be
considered in formulating research needs.
18-21
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