_ TECHNICAL REPORT DATA
(rlette rtfd Jnttrvcnoru on the severer be/ore completion
|1. REPORT NO.
EPA/600/8-89/090
2.
|4. TITLE AND SUiTITLE
Updated Health Effects Assessment for Chloroform
3. RECIPIENT'S ACCESSION NO
PB90-142423/AS
V REPORT DATE
*. PERFORMING ORGANIZATION CODE
7. AUTMOR(S)
. PERFORMING ORGANIZATION REPORT NO
«. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Criteria and Assessment Office
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati. OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/22
IS SUPPLEMENTARY NOTES
16. ABSTRACT
This report summarizes and evaluates information relevant to a preliminary interim
assessment of adverse health effects associated with specific chemicals or compounds.
The Office of Emergency and Remedial Response (Superfund) uses these documents in
preparing cost-benefit analyses under Executive Order 12991 for decision-making under
CERCLA. All estimates of acceptable intakes and carcinogenic potency presented in
this document should be considered as preliminary and reflect limited resources
allocated to this project. The intent in these assessments is to suggest acceptable
exposure levels whenever sufficient data are available. The interim values presented
reflect the relative degree of hazard associated with exposure or risk to the
chemical(s) addressed. Whenever possible, two categories of values have been
estimated for systemic toxicants (toxicants for which cancer is not the endpoint of
concern). The first, RfDs or subchronic reference dose, is an estimate of an exposure
level that would not be expected to cause adverse effects when exposure occurs during
a limited time interval. The RfO is an estimate of an exposure level that would not
be expected to cause adverse effects when exposure occurs for a significant portion
of the lifespan. For compounds for which there is sufficient evidence of
carcinogenicity, qi*s have been computed, if appropriate, based on oral and
inhalation data if available.
i.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b,IDENTIFIERS/OPEN ENDED TERMS
COSATi Field/Croup
1*. DISTRIBUTION STATEMENT
Public
10. SECURITY CLASS (Tha Rtporl/
Unrlassified
21. NO. OF PACES
20. SECURITY CLASS (Thil ptgtl
Unclassified
22. PRICE
EPA F«m 2220.1 (*». 4.77)
BDITION i» OMOLCTC
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EPA/600/8-89/090
April, 1988
HEALTH EFFECTS ASSESSMENT
FOR CHLOROFORM
ENVIRONMENTAL CRITERIA AND ASSESSMENT OFFICE
OFFICE OF HEALTH AND ENVIRONMENTAL ASSESSMENT
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
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DISCLAIMER
This document has been reviewed 1n accordance with the U.S. Environ-
mental Protection Agency's peer and administrative review policies and
approved for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
11
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PREFACE
This report summarizes and evaluates Information relevant to a prelimi-
nary Interim assessment of adverse health effects associated with chloro-
form. All estimates of acceptable Intakes and carcinogenic potency present-
ed 1n this document should be considered as preliminary and reflect limited
resources allocated to this project. Pertinent toxlcologlc and environ-
mental data were located through on-Hne literature searches of the Chemical
Abstracts, TOXLINE, CANCERLINE and the CHEMFATE/DATALOG data bases. The
basic literature searched supporting this document Is current up to May,
1987. Secondary sources of Information have also been relied upon In the
preparation of this report and represent large-scale health assessment
efforts that entail extensive peer and Agency review. The following Office
of Health and Environmental Assessment (OHEA) sources have been extensively
utilized:
U.S. EPA. 1980a. Ambient Water Quality Criteria Document for
Chloroform. Prepared by the Office of Health and Environmental
Assessment, Environmental Criteria and Assessment Office,
Cincinnati, OH for the Office of Water Regulations and Standards,
Washington, DC. EPA-440/4-80-033. NTIS PB 81-117442.
U.S. EPA. 1982. Hazard Profile for Chloroform. Prepared by the
Office of Health and Environmental Assessment, Environmental
Criteria and Assessment Office, Cincinnati, OH for the Office of
Solid Waste, Washington, DC.
U.S. EPA. 1983. Review of Toxlcologlc Data 1n Support of Evalua-
tion for Carcinogenic Potential of Chloroform. Prepared by the
Office of Health and Environmental Assessment, Carcinogen Assess-
ment Group, Washington, DC for the Office of Solid Waste and
Emergency Response.
U.S. EPA. 1985. Health Assessment Document for Chloroform.
Office of Health and Environmental Assessment, Environmental
Criteria Assessment Office, Research Triangle Park, NC. EPA
600/8-84/004F. NTIS PB 86-105004.
U.S. EPA. 1987a. Integrated Risk Information System (IRIS).
Reference dose (RfD) for oral exposure for chloroform. On-Llne:
(Verification date 12/02/85). Office of Health and Environmental
Assessment, Environmental Criteria and Assessment Office,
Cincinnati, OH.
U.S. EPA. 1987b. Integrated Risk Information System (IRIS). Risk
estimate for carclnogenldty for chloroform. On Line: Input
pending. (Verification Date 8/26/87). Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office, Cincinnati, OH.
111
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The Intent 1n these assessments Is to suggest acceptable exposure levels
for noncardnogens and risk cancer potency estimates for carcinogens
whenever sufficient data were available. Values were not derived nor were
larger uncertainty factors employed when the variable data were limited 1n
scope, which tended to generate conservative (I.e., protective) estimates.
Nevertheless, the Interim values presented reflect the relative degree of
hazard or risk associated with exposure to the chemlcal(s) addressed.
Whenever possible, two categories of values have been estimated for
systemic toxicants (toxicants for which cancer 1s not the endpolnt of
concern). The first, RfDg (formerly AIS) or subchronlc reference dose, Is
an estimate of an exposure level that would not be expected to cause adverse
effects when exposure occurs during a limited time Interval (I.e., for an
Interval that does not constitute a significant portion of the Hfespan).
This type of exposure estimate has not been extensively used, or rigorously
defined, as previous risk assessment efforts have been primarily directed
towards exposures from toxicants 1n ambient air or water where lifetime
exposure Is assumed. Animal data used for RFD$ estimates generally
Include exposures with durations of 30-90 days. Subchronlc human data are
rarely available. Reported exposures are usually from chronic occupational
exposure situations or from reports of acute accidental exposure. These
values are developed for both Inhalation (RfD$i) and oral (RfD$0)
exposures.
The RfD (formerly AIC) 1s similar 1n concept and addresses chronic
exposure. It 1s an estimate of an exposure level that would not be expected
to cause adverse effects when exposure occurs for a significant portion of
the Hfespan [see U.S. EPA (1980b) for a discussion of this concept]. The
RfD Is route-specific and estimates acceptable exposure for either oral
(RfD0) or Inhalation (RfDj) with the Implicit assumption that exposure
by other routes 1s Insignificant.
Composite scores (CSs) for noncardnogens have also been calculated
where data permitted. These values are used for Identifying reportable
quantities and the methodology for their development 1s explained In U.S.
EPA (1984).
For compounds for which there 1s sufficient evidence of carclnogenlclty
RfD$ and RfD values are not derived. For a discussion of risk assessment
methodology for carcinogens refer to U.S. EPA (1980b). Since cancer 1s a
process that 1s not characterized by a threshold, any exposure contributes
an Increment of risk. For carcinogens, q-|*s have been computed, 1f appro-
priate, based on oral and Inhalation data 1f available.
1v
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ABSTRACT
In order to place the risk assessment evaluation In proper context,
refer to the preface of this document. The preface outlines limitations
appl'icable to all documents of this series as well as the appropriate
Interpretation and use of the quantitative estimates.
Chloroform has been shown to be carcinogenic by the oral route In
rodents In several Independent Investigations. Human data are suggestive
for chlorinated drinking water, but are Inadequate for chloroform alone.
Chloroform Is classified as an EPA Group B2 carcinogen, probable human
carcinogen, based on sufficient evidence from animal studies and Inadequate
evidence from human studies.
U.S. EPA (1985) has estimated a unit risk for Inhalation exposure of
2.3xlO~5 (vg/m3)"1 based upon route extrapolation from a q-j* of
8.1xlO"2 (mg/kg/day)"1. This assessment Is based upon data for
Incidence of liver tumors In male and female mice (NCI, 1976).
U.S. EPA (1987b) has estimated an oral q-|* of 6.1xlO~8 (mg/kg/day)'1
based upon kidney tumors In male rats exposed In the drinking water In a
study by Jorgenson et al. (1985).
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ACKNOWLEDGEMENTS
The Initial draft of this report was prepared by Syracuse Research
Corporation under Contract No. 68-03-3112 for EPA's Environmental Criteria
and Assessment Office, Cincinnati, OH. Dr. Christopher DeRosa and Karen
Blackburn were the Technical Project Monitors and Helen Ball was the Project
Officer. The final documents In this series were prepared for the Office of
Emergency and Remedial Response, Washington, DC.
Scientists from the following U.S. EPA offices provided review comments
for this document series:
Environmental Criteria and Assessment Office, Cincinnati, OH
Carcinogen Assessment Group
Office of Air Quality Planning and Standards
Office of Solid Waste
Office of Toxic Substances
Office of Drinking Water
Editorial review for the document series was provided by the following:
Judith 01 sen and Erma Durden
Environmental Criteria and Assessment Office
Cincinnati, OH
Technical support services for the document series was provided by the
following:
Bette Zwayer, Jacky Bohanon and K1m Davidson
Environmental Criteria and Assessment Office
Cincinnati, OH
v1
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TABLE OF CONTENTS
1.
2.
3.
ENVIRONMENTAL CHEMISTRY AND FATE
ABSORPTION FACTORS IN HUMANS AND EXPERIMENTAL ANIMALS . . .
2.1.
2.2.
ORAL
INHALATION
TOXICITY IN HUMANS AND EXPERIMENTAL ANIMALS
3.1.
3.2.
SUBCHRONIC
3.1.1. Oral
3.1.2. Inhalation
CHRONIC
3.2.1. Oral
3.2.2. Inhalation
Page
. . . 1
. . . 3
. . . 3
. . . 3
. . . 5
. . . 5
. . . 5
, . , 7
, , , 7
. . . 7
. . . 8
4.
5.
w * w *
3.4.
i ui\n i uuuna v.1 i i mil* u i nun i\L.ri\uuuu i i *u LI I u\»
3.3.1. Oral ,
3.3.2. Inhalation
TOXICANT INTERACTIONS
CARCINOGENICITY ,
4.1.
4.2.
4.3.
4.4.
HUMAN DATA
4.1.1. Oral ,
4.1.2. Inhalation
BIOASSAYS
4.2.1. Oral ,
4.2.2. Inhalation
OTHER RELEVANT DATA
WEIGHT OF EVIDENCE
REGULATORY STANDARDS AND CRITERIA
9
10
10
12
12
12
12
12
12
16
16
19
20
V11
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TABLE OF CONTENTS
Page
6. RISK ASSESSMENT 22
6.1. SUBCHRONIC REFERENCE DOSE (RfDs) 22
6.2. REFERENCE DOSE (RfD) 22
6.3. CARCINOGENIC POTENCY (q-|*) 22
6.3.1. Oral 22
6.3.2. Inhalation 22
7. REFERENCES 25
APPENDIX: Summary Table for Chloroform 36
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LIST OF TABLES
No. Title Page
3-1 Subchronlc Tox1c1ty of Chloroform 6
4-1 Oral Bloassays of Chloroform Cardnogenldty 13
4-2 Kidney Tumors In Hale Osborne-Mendel Rats Exposed to
Chloroform In Drinking Water for 104 Weeks 17
1x
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LIST OF ABBREVIATIONS
ADI Acceptable dally Intake
ATP Adenoslne trlphosphate
bw Body weight
CAS Chemical abstract service
CS Composite score
DENA Dlethyl nltrosamlne
DNA Deoxyrlbonuclelc add
GGTase Gamma glutamyl transpeptldase
Koc Soil sorptlon coefficient
Kow Octanol/water partition coefficient
LOAEL Lowest-observed-adverse-effect level
ppm Parts per million
RfD Reference dose
RfDj Inhalation reference dose
RfDo Oral reference dose
RfD$ Subchronlc reference dose
RfD$i Subchronlc Inhalation reference dose
RfD$o Subchronlc oral reference dose
SGOT Serum glutamlc oxaloacetlc transamlnase
SGPT Serum glutamlc pyruvlc transamlnase
STEL Short-term exposure limit
TLV Threshold limit value
TWA Time-weighted average
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1. ENVIRONMENTAL CHEMISTRY AND FATE
The relevant physical and chemical properties and environmental fate of
chloroform (CAS No. 67-66-3) are as follows:
Chemical class:
Molecular weight:
Vapor pressure:
Water solubility:
Kow:
B1oconcentrat1on factor:
{In blueglll, Lepomls macrochlrus)
Half-lives In
air:
water:
halogenated aliphatic hydrocarbon
(purgeable halocarbon)
119.38 (Callahan et al.. 1979)
150.5 mm Hg at 20°C
{Callahan et al., 1979)
8200 mg/l at 20°C
{Callahan et al., 1979)
93 {Callahan et al., 1979)
0-40 (Hutzler et al., 1983)
6 (Barrows et al., 1978)
70-79 days
(Atkinson, 1985; NLM, 1987)
0.3-3 days 1n rivers
3-30 days 1n lakes
(Zoeteman et al., 1980)
Volatilization 1s the primary fate process for chloroform 1n water
because of the relatively high vapor pressure (NLM, 1987). Adsorption to
suspended solids and sediments and bloaccumulatlon In aquatic organisms will
not be significant (NLM, 1987).
The half-life of chloroform 1n soil could not be located In the litera-
ture searched; however, evaporation 1s expected to be the predominant loss
mechanism from the soil surface. The half-life for soil evaporation should
be longer than Its evaporation half-life from water. This compound 1s
highly mobile In most soils, especially those with high organic carbon
content, (Hutzler et al., 1983) and In subsurface soil It 1s expected to
001 OH
-1-
01/15/88
-------
remain stable enough to leach Into groundwater (NLM, 1987). Upon
contamination of groundwater, chloroform 1s likely to persist for long
periods of time (no degradation was observed when Incubated with aquifer
material for 27 weeks) (Wilson et al., 1983).
In the atmosphere, reaction with photochemlcally generated hydroxyl
radicals will be the predominant removal mechanism (NLM, 1987). Based on a
tropospherlc to stratospheric turnover time of 30 years and a half-life of
70-79 days, <1% of the tropospherlc chloroform Is expected to diffuse Into
the stratosphere (Callahan et al., 1979; Atkinson, 1985; NLM, 1987).
Chloroform 1s expected to be transported long distances from Its emission
sources based on the relatively slow rate of degradation 1n air.
0010H -2- 01/20/88
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2. ABSORPTION FACTORS IN HUMANS AND EXPERIMENTAL ANIMALS
2.1. ORAL
Evidence from human assays (Fry et al., 1972), as well as from animal
experiments (Brown et al., 1974; Taylor et al., 1974), Indicates that
Ingested chloroform 1s absorbed nearly completely from the gastrointestinal
tract. Brown et al. (1974) orally administered a 60 mg/kg dose of
14C-chloroform to mice, rats and squirrel monkeys and recovered 93-98% of
the administered dose of radioactivity In the expired air, urine and carcass
48 hours, after treatment. That gastrointestinal absorption was rapid as
well as extensive was further Indicated by the observation that peak blood
levels of radioactivity occurred at 1 hour 1n the mice and monkeys. In man,
peak levels of 18C In the blood occurred 1 hour after an oral 500 mg dose
of 13C-chloroform 1n olive oil by gelatin capsule (Fry et al., 1972).
WHhey et al. (1982) administered a 75 mg/kg dose of chloroform In ~4
ml of water or corn oil to mature fasted rats to Investigate the effect of
vehicle on gastrointestinal absorption. The times to Initial peak blood
concentrations were nearly equivalent at 5.6 minutes for water and 6.0
minutes for corn oil. A second peak 1n blood concentration occurred at 40
minutes for corn oil-treated rats. The postabsorptlon peak blood concen-
tration was 39.3 yg/m!. when administered 1n water and 5.9 yg/mi when
administered 1n corn oil, and the area under the blood concentration curves
was 8.7 times greater for water than for corn oil, which suggests that the
large volume (for a rat) of corn oil substantially slowed gastrointestinal
absorption.
2.2. INHALATION
Without providing documentation, U.S. EPA (1980a) stated that 49-77% of
the chloroform present 1n Inspired air Is absorbed by the respiratory tract,
presumably In humans.
001 OH -3- 01/15/88
-------
U.S. EPA (1985) reviewed pulmonary retention data from humans during the
use of chloroform as an anesthetic (Lehmann and Hasegawa, 1910; Smith et
al., 1973). Pulmonary retention, estimated by measuring the difference
between Inhaled and exhaled concentrations of chloroform and by measuring
respiratory rate, was observed to decrease as duration of exposure
Increased. U.S. EPA (1985) estimated retention at equilibrium at -65-67%.
It was predicted that the percent retained would be Independent of the
Inspired concentration and therefore that estimations based on very high
concentrations used 1n anesthesia (-8000-10,000 ppm) would be equally
applicable to the much lower levels anticipated with environmental
exposure. U.S. EPA (1985) noted that chloroform retention would be expected
to be higher In Individuals with larger than average proportions of body fat
because of the Upophlllc nature of the compound.
001 OH -4- 01/15/88
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3. TOXICITY IN HUMANS AND EXPERIMENTAL ANIHALS
3.1. SUBCHRONIC
Table 3-1 presents a summary of the effects of subchronlc chloroform
exposure.
3.1.1. Oral. DeSalva et al. (1975) reported that chloroform at dose
levels of 1.0 and 2.5 mg/kg/day for 1 year produced no effects on the
functioning of the human liver and kidney.
No effects In rats were reported at dose levels of 15 and 30 mg/kg/day
(Palmer et al., 1979); however, Increased relative liver and kidney weight
was observed at 150 mg/kg/day, and severe toxic effects, such as necrosis of
the liver and dysfunction of the gonads were produced at 410 mg/kg/day
(Palmer et al., 1979).
In an experiment to Investigate the effect of vehicle on the hepato-
toxlclty of chloroform 1n mice, Bull et al. (1986) administered chloroform
1n corn oil or 2X Emulphor to groups of 9-10 male and 9-10 female B6C3F1
mice at 0, 60, 130 or 270 mg/kg/day for 91-94 consecutive days. In male
mice, chloroform Increased liver weights when given 1n corn oil but not when
given In Emulphor. Chloroform In either vehicle Increased the liver weights
of female mice, but the effect was greater with corn oil. Elevated SGOT
occurred 1n a dose-related manner 1n both sexes, but only when the vehicle
was corn oil. Upon hlstopathologlc examination, fatty degeneration was
observed 1n chloroform-treated groups with the corn oil vehicle. At 270
mg/kg/day, the hepatic architecture was disrupted severely and early cirrho-
sis was evident. These lesions were not observed In corn oil controls or In
mice treated with chloroform 1n Emulphor. Minimal to mild focal necrosis
was the only lesion observed 1n mice treated with chloroform 1n Emulphor.
001 OH -5- 01/20/88
-------
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07/17/87
-------
The Investigators concluded that the vehicle strongly Influences the
hepatotoxldty of chloroform 1n mice and that the difference 1n vehicle may
explain the markedly different results observed in cancer studies In mice
when nearly equivalent total doses were given 1n corn oil (NCI, 1976) or
drinking water (Jorgenson et al., 1985) (Chapter 4).
3.1.2. Inhalation. Torkelson et al. (1976) exposed rats, guinea pigs and
rabbits to 25, 50 or 85 ppm (122, 244 or 415 mg/m3, respectively), 7
hours/day, 5 days/week for 6 months (see Table 3-1). Exposure to 25 ppm
chloroform produced hlstopathologlcal changes 1n the livers and kidneys of
male but not female rats. At higher doses, lobular granular degeneration
and focal necrosis were Increased 1n the liver, and cloudy swelling of
epithelial cells was Increased 1n the kidney. These changes were reported
to be reversible after 6 weeks. Hematologlcal, clinical chemistry and
urlnalysls values were "within normal limits." The results obtained from
chloroform exposure In guinea pigs and rabbits are difficult to Interpret
because adverse effects were seen at the low-dose (25 ppm) and high-dose (85
ppm) levels, but no effects were reported, at the Intermediate-dose level
(50 ppm).
3.2. CHRONIC
3.2.1. Oral. Several chronic oral studies (NCI, 1976; Palmer et al.,
1979; Roe et al., 1979) were designed to test the cardnogenlclty of chloro-
form (Chapter 4). Depression of body weight was observed at chloroform
doses >60 mg/kg/day 1n rats (NCI, 1976; Palmer et al., 1979) and mice (Roe
et al., 1979). Palmer et al. (1979) exposed Sprague-Dawley rats of both
sexes to 60 mg/kg/day of chloroform 1n a toothpaste base for 80 weeks
followed by 15 weeks of observation. Decreased relative liver weight and
plasma chollnesterase levels were reported In female rats (Palmer et al.,
1979). Rats of both sexes survived better than the controls, though both
001OH -7- 01/15/88
-------
groups had a high Incidence of non-neoplast1c respiratory and renal
disease. There were no treatment-related effects on the Incidence of liver
or kidney tumors following treatment of 60 mg/kg/day for 80 weeks. Although
hlstologlcally - malignant mammary tumors were reported more 1n treated than
1n control female rats, the difference was not statistically significant
(Palmer et al., 1979). Higher chloroform doses (90 and 180 mg/kg/day, 5
days/week for 78 weeks) resulted 1n an Increased Incidence of noncancerous
respiratory diseases 1n rats (NCI, 1976), and a gavage dose of 477 mg/kg/day
for 78 weeks resulted 1n decreased survival 1n female mice (NCI, 1976).
Heywood et al. (1979) administered chloroform In a toothpaste base 1n
gelatin capsules at 15 or 30 mg/kg/day, 6 days/week for 7.5 years to groups
of eight male and eight female beagle dogs. A control group of 16 dogs/sex
was maintained. Fatty cysts developed 1n the livers of some dogs 1n each of
the treated groups, and was considered to be treatment-related. SGPT and
other serum enzyme Indicators of liver damage were elevated 1n a
dose-related fashion.
Chronic exposure of humans to chloroform appears to result 1n adverse
effects on the central nervous system (NIOSH, 1974), although there are no
data on the dose relation of the effects. In addition, chloroform affects
the liver and kidneys 1n humans (NIOSH, 1974). The potential for chronic
human oral exposure to chloroform has Increased because of the widespread
practice of chlorinating drinking water (U.S. EPA, 1980a).
3.2.2. Inhalation. Epldemlologlcal studies of humans exposed to chloro-
form In the workplace at levels ranging from 22-237 ppm have Indicated that
tiredness, depression, gastrointestinal disturbances (e.g., flatulence,
nausea), headache and frequent and scalding urination are the primary
symptoms (Challen et al., 1958; Bomskl et al. 1967). Regarding long-term
effects, Challen et al. (1958) reported that there was no evidence of
001 OH -8- 01/20/88
-------
organic lesions attributable to chloroform, based on physical exams and
liver function tests. Bomskl et al. (1967) reported that chloroform
exposure at levels as low as 2 ppm for 1-4 years may result In an Increased
Incidence of toxic hepatitis, splenomegaly and hepatomegaly, although no
statistical analysis and adequate controls were presented.
3.3. TERATOGENICITY AND OTHER REPRODUCTIVE EFFECTS
3.3.1. Oral. Thompson et al. (1974) performed oral range-finding and
developmental toxlclty studies where Sprague-Dawley rats and Dutch-Belted
rabbits were used. In the range-finding study, groups of six rats were
treated by gavage with 79, 126, 300, 316 or 516 mg/kg/day of chloroform In
corn oil on days 6-15 of gestation. Maternal toxlclty was observed at >126
mg/kg/day and fetotoxlclty was observed at >316 mg/kg/day. In the defini-
tive study, groups of 25 rats were treated with 20, 50 or 126 mg/kg/day.
Maternal toxlclty was observed at >50 mg/kg/day, but no adverse develop-
mental effects were reported at any level. The range-finding study used
groups of five rabbits and doses of 25, 63, 100, 159, 251 or 398 mg/kg/day
on days 6-18 of gestation; maternal toxlclty was observed at all dosage
levels. In the two dams that survived at 100 mg/kg/day one had four
resorptlons and the other was not pregnant. The definitive rabbit study was
performed with groups of 15 rabbits treated with at 20, 35 and 50
mg/kg/day. Reduced maternal body weight was observed at 35 but not at 50
mg/kg/day and reduced fetal body weight was observed at 35 but not at 20 or
50 mg/kg/day.
Ruddlck et al. (1983) administered chloroform at 100, 200 or 400 mg/kg/
day to groups of 15 mated Sprague-Dawley rats on days 6-15 of gestation. A
dose-related decrease In maternal body weight gain was observed at all
dosage levels, while fetal body weight was decreased only at 400 mg/kg/day.
001 OH -9- 01/20/88
-------
This group also had a higher Incidence of sternebral anomalies and fetal
runts.
Palmer et al (1979) performed a study 1n which Sprague-Dawley rats were
given dally gavage doses of 0, 15, 30, 150 and 410 mg/kg/day of chloroform
In toothpaste (10 of each sex per dose level) for 13 weeks and observed
gonadal atrophy In both sexes treated with 410 mg/kg/day.
Burkhalter and Balster (1979) Investigated the effects of chloroform at
31.1 mg/kg/day on behavior 1n developing ICR mice. Mice were treated from
21 days before mating until 21 days after birth. The offspring were treated
on days 7-2"! of age. Treatment had no effect on Utter size, but offspring
body weights were reduced. There was no definite effect of treatment on the
behavior of the offspring.
3.3.2. Inhalation. Schwetz et al. (1974) exposed groups of 20 female
Sprague-Dawley rats to chloroform at 30, 100 or 300 ppm (146, 488 or 1465
mg/ma), 7 hours/day on gestation days 6-15. Maternal toxldty, manifested
as decreased maternal weight gain, occurred In all exposed groups. Reduced
fetal crown-rump length was observed at 30 and 300 ppm but not at 100 ppm.
Severe teratogenlc effects were observed at >100 ppm. Fetal resorptlon was
greatly Increased at 300 ppm. Murray et al. (1979) exposed groups of mated
CF-1 mice to chloroform at 100 ppm, 7 hours/day on days 6-15 of gestation.
Other groups of mice were exposed to 100 ppm, 7 hours/day on days 1-7 or
8-15 of gestation. Effects reported during one or more of the three periods
of exposure Include Increased resorpt1ons/!1tter, decreased fetal body
weight and crown-rump length, delayed skeletal ossification, Increased Inci-
dence of cleft palate and maternal toxldty manifested as reduced rate of
body weight gain and Increased liver weight.
0010H -10- 01/15/88
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3.4. TOXICANT INTERACTIONS
The toxlclty of chloroform 1s greatly Influenced by anything that alters
mlcrosomal enzyme activity or hepatic GSH levels (U.S. EPA, 1985). The
substances that potentiate the toxic effects of chloroform are methyl
n-butyl ketone (Branchflower and Pohl, 1981), alcohol (Kutob and Plaa,
1961), carbon tetrachlorlde (Harris et al., 1982), chlordecone (I1j1ma et
a!., 1983), DDT and phenobarbltal (McLean, 1970). Methyl n-butyl ketone
Increases the toxldty of chloroform by lowering glutathlone levels and by
Increasing the levels of hepatic cytochrome P-450 (which. In turn. Increases
the metabolism of chloroform to phosgene) and by decreasing GSH levels
(Branchflower and Pohl, 1981). Harris et al. (1982) reported that carbon
tetrachlorlde potentiated the toxic effects of chloroform because of
Increased phosgene formation and the Initiation of I1p1d peroxldatlon. The
mechanism of Interaction for alcohol, chlordecone, DDT and phenobarbltal was
not discussed, von Oettlngen (1964) reported that high-fat/low-protein
diets potentiated the hepatotoxlc effects of chloroform 1n animals.
001 OH -11- 01/20/88
-------
4. CARCINOGENICITY
4.1. HUMAN DATA
4.1.1. Oral. Although chloroform has not unequivocally been shown to
cause human cancer, ecological and case control studies (Alavanja et a!.,
1978; Cantor et al., 1978; Brennlman et al., 1978; Hogan et al., 1979;
Struba, 1979; Gottlieb et al., 1981; Young et al., 1981) have consistently
supported the association of Increased risk of bladder, colon and rectal
cancer with oral exposure to chlorinated drinking water (U.S. EPA, 1983) In
which trlhalomethanes and chloroform are the contaminants present In
greatest quantities. A detailed description of these studies and their
strengths and weaknesses Is available 1n U.S. EPA (1985).
4.1.2. Inhalation. Pertinent data regarding an association between
chloroform Inhalation and an Increased Incidence or risk of cancer were not
located 1n the available literature.
4.2. BIOASSAYS
4.2.1. Oral. Table 4-1 summarizes the available data from several early
gavage bloassays of chloroform cardnogenldty. Eschenbrenner and Miller
(1945) reported that a dose level of chloroform that caused hepatic necrosis
when given once would cause hepatic carcinoma when given repeatedly. The
NCI (1976) found a dose-related Increase 1n hepatomas 1n both sexes when
mice received chloroform 1n corn oil by gavage, and an Increase In renal
epithelial tumors 1n male rats receiving chloroform In corn oil by gavage
(see Table 4-1). The Increased Incidence of hepatic and renal tumors was
statistically significant (p<0.05). Palmer et al. (1979) criticized the NCI
(1976) study because rats being treated with other volatile carcinogenic
substances were housed In the same room as the chloroform-treated rats.
0010H -12- 04/12/88
-------
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Because chloroform has been a contaminant 1n toothpaste, rats (Palmer et
al., 1979), mice (Roe et al., 1979) and dogs (Heywood et al, 1979) were
treated with chloroform 1n a toothpaste base Including essential oils as
flavor components. Range-finding studies were performed 1n all experiments.
No effects at dose levels of 15, 75 and 165 mg/kg/day for 52 weeks were
reported In rats. When female rats were treated with 60 mg/kg/day for 96
weeks, however, there was an Increase (p=0.056) 1n malignant mammary gland
tumors 1n the chloroform-treated group, although the untreated group
developed benign mammary tumors (Palmer et al., 1979). There was an
Increased Incidence of kidney tumors In the high-dose (60 mg/kg/day) level
1n male mice (Roe et al., 1979). The females had no Increased Incidence of
cancer, but there appeared to be some confounding Influence because of the
vehicle. The authors addressed, but did not resolve, the problem of the
effect produced by different vehicles (Roe et al., 1979).
Recent studies Indicate that chloroform 1s carcinogenic to rats and mice
when administered 1n drinking water. Tumasonls et al. (1985) provided
groups of 32 male and 45 female Wlstar rats with drinking water containing
chloroform for lifetime. The Initial concentration, 2.9 g/l (2900 ppm),
was reduced by one-half after 72 weeks to maintain a fairly constant Intake
of chloroform because water consumption had Increased. The dosage of
chloroform 1s estimated at ~200 mg/kg/day for both sexes, based on graphic
data provided by the Investigators. Controls consisted of 28 male and 22
female rats provided with tap water. Treated rats weighed substantially
less than their sex-matched controls throughout the experiment. Survival
appeared not to be affected by treatment. The most noteworthy observation
was a significantly Increased Incidence of neoplastlc nodules 1n the liver
of female rats, 10/40 compared with 0/18 In controls (p<0.03).
001 OH -15- 04/12/88
-------
Jorgenson et al. (1985) provided drinking water containing chloroform at
0, 200, 400, 900 or 1800 mg/fc (ppm) to groups of male Osborne-Mendel rats
and female B6C3F1 mice for 104 weeks. Because water consumption Is reduced
with high concentrations of chloroform, a matched control group was provided
water 1n amount to match the consumption of the high-dose groups. For rats,
group sizes were 330 for controls and 200 ppm, 150 at 400 ppm and 50 for
matched controls, 900 and 1800 ppm. Group sizes for mice were Identical to
rats, except that the control and 200 ppm groups contained 430 mice.
Survival of mice appeared to be unaffected by treatment. Treated rats
survived longer than controls, attributed by the Investigators to the fact
that treated animals were leaner because of decreased water and food
Intake. Several tumor types occurred 1n rats at a significantly Increased
Incidence, but only kidney tumors, which occurred 1n a dose-related manner,
were attributed to treatment with chloroform. The Incidence of kidney
tumors In the rats 1s presented 1n Table 4-2. No tumor type occurred In
female mice at a significantly greater Incidence In treated groups than 1n
controls.
4.2.2. Inhalation. Pertinent data regarding the cardnogenlcHy of
Inhaled chloroform were not located 1n the available literature.
4.3. OTHER RELEVANT DATA
Chloroform was not mutagenlc In Escher1ch1a coll strains K12, WP2p and
WP2uvrA"p or 1n Salmonella typhlmuMum strains TA98, TA100, TA1535, TA1537
and TA1538 (Klrkland et al., 1981) with or without S-9 metabolic activation.
Chloroform was not mutagenlc In cultured Chinese hamster lung flbroblasts at
the 8-azaguanlne locus (Sturrock, 1977), nor did chloroform Increase sister
chromatld exchanges 1n cultured Chinese hamster ovary cells or human lympho-
cytes (White et al., 1979; Uehleke et al., 1977). In a recent experiment 1n
001 OH -16- 04/12/88
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which chloroform was used at a higher concentration, chloroform Induced
sister chromatld exchange 1n cultivated human lymphocytes (Morlmoto and
Koizumi, 1983). Chloroform was reported to be weakly positive or "sugges-
tive" In mutagenlclty assays 1n Saccharomyces cerevlslae D7 1n the presence
of S-9 metabolic activation, and In the Induction of muMne sperm head
abnormalities (Agustln and L1m-Syl1anco, 1978; Callen et al., 1980; Land et
al., 1981; Topham, 1980; Gocke et al., 1981).
Several authors have Investigated the mechanism for chloroform-Induced
carc1nogen1c1ty In laboratory animals. Reltz et al. (1982) measured DNA
alkylatlon and repair and cellular regeneration In male B6C3F1 mice given
single 15, 60 or 240 mg/kg oral doses of chloroform. DNA alkylatlon,
estimated as ymol of bound chloroform/mo 1 of DNA, was 1.5, compared with
6000-7430 ymol/mol for dlmethylnltrosamlne, a known genotoxlc carcinogen.
Using a technique Involving Incorporation of 3H-thym1d1ne Into DNA
following treatment with hydroxyurea sufficient to depress normal DNA
synthesis, these Investigators determined that chloroform did not Induce DNA
repair 1n the livers of treated mice. Cellular regeneration, estimated by
8H-thym1d1ne Incorporation Into DNA In nonhydroxyurea-treated mice, was
Increased 14-fold In the liver and 25-fold In the kidneys of
chloroform-treated mice. The authors concluded that cardnogenlclty
associated with chloroform was due to cellular necrosis rather than to DNA
damage.
In Initiation-promotion experiments with male Sprague-Dawley rats,
Perelra et al. (1982) determined that chloroform did not Initiate the
development of GGTase-pos1t1ve fod 1n the livers of rats promoted with
phenobarbltal, and the results concerning the promoting activity 1n rats
pretreated with d1ethyln1trosam1ne (DENA), was not conclusive. Demi and
OQ10H -18- 04/12/88
-------
Oesterle (1985), however, reported that chloroform promoted the development
of DENA-lnduced ATPase deficient fod and GGTase-pos1t1ve foci In the livers
of female Sprague-Dawley rats.
Klaunlg et al. (1986) provided chloroform 1n drinking water for 52 weeks
to male B6C3F1 mice that were treated with DENA In drinking water for 4
weeks to Initiate tumor formation. Neither DENA nor chloroform alone
Increased the Incidence of tumors, but chloroform Inhibited Hver and lung
tumor 1 genes Is 1n the DENA-1n1t1ated mice.
4.4. WEIGHT OF EVIDENCE
Oral exposure to chloroform has caused hepatic carcinomas 1n male and
female B6C3F1 mice (NCI, 1976), renal carcinomas and adenomas 1n male
Osborne-Mendel rats (NCI, 1976; Jorgenson et al., 1985) and In male ICI mice
(Roe et al., 1979), thyroid tumors 1n female Osborne-Mendel rats (NCI, 1976)
and an slightly Increased Incidence of malignant mammary gland tumors after
chronic exposure 1n Sprague-Dawley rats (Palmer et al., 1979). Evidence 1s
sufficient to classify chloroform as an animal carcinogen. Although some
association between oral exposure to chlorinated drinking water (1n which
tMhalomethanes and chloroform usually predominates) and human bladder,
Intestinal and rectal cancer has been reported (see Section 4.1.1.), the
evidence for human carclnogenldty of chloroform Itself 1s Inadequate.
Applying the criteria for evaluating the overall weight of evidence of
carclnogenldty to humans adopted by the Carcinogen Assessment Group of the
U.S. EPA (1986), chloroform 1s classified In Group B2, a probable human
carcinogen. This classification 1s consistent with the analysis by U.S. EPA
(1985).
001 OH -19- 04/12/88
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5. REGULATORY STANDARDS AND CRITERIA
The ACGIH (1986a,b) recommends a tWA-TLV of 10 ppm {50 mg/m3) for
occupational exposure to chloroform and also notes that chloroform has
Induced cancer 1n animals by the oral route at high and Intermediate dose
levels and 1s a suspected carcinogen for humans. OSHA (1985) has set a
celling limit for chloroform of 50 ppm (240 mg/m3} 1n the workroom
atmosphere.
U.S. EPA (1987a) reports an RfD for oral exposure to chloroform of
IxlO"2 mg/kg/day or 1 mg/day for a 70 kg human, based on the development
of fatty cysts 1n the livers of dogs treated with 15 mg/kg/day, 6 days/week
for 7.5 years (Heywood et al., 1979).
The Carcinogen Assessment Group (U.S. EPA, 1985) analyzed the following
data: liver tumors 1n female mice (NCI, 1976); liver tumors 1n male mice
(NCI, 1976); kidney tumors 1n male rats (NCI, 1976; Gorgenson et al., 1985);
and kidney tumors 1n male mice (Roe et al., 1979). The largest estimates of
carcinogenic potency were derived from the liver tumor data In male and
female mice 1n the NCI (1976) gavage study. A q^ of 8.1xlO~2
(mg/kg/day)"1 was derived as the geometric mean of the q *s derived
separately for male and female mice. A complete discussion of this deriva-
tion 1s presented In U.S. EPA (1985). More recently, the CRAVE work group
(U.S. EPA, 1987b) recommended that the q^ for oral exposure via drinking
water be based upon the drinking water study by Jorgenson et al. (1985).
The Jorgenson study was Included 1n the Health Assessment Document for
Chloroform (U.S. EPAS, 1985) but was not selected as the primary basis for
drinking water risk estimation. Given the CRAVE action (U.S. EPA, 1987b),
the Agency now uses the q-j* value of 6.1xlO~3 (mg/kg/day)'1 based on
0010H -20- 04/12/88
-------
the Incidence of kidney tumors In male rats In the study by Jorgenson et al.
(1985). The upper bound estimate of cancer risk for exposure to 1 yg/L of
chloroform In water Is 1.7xlO"7.
Using q-j* of S.lxlO"2 (mg/kg/dayT1, EPA (1985) calculated
upper-bound estimates of cancer risk for exposure to 1 yg/m3 In air to
be 2.3xl(T5. This q,* for Inhalation exposure to chloroform was
validated by the CRAVE work group on August 26, 1987 (EPA, 1987).
001 OH -21- 04/12/88
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6. RISK ASSESSMENT
6.1. SUBCHRONIC REFERENCE DOSE (RfD$)
Chloroform 1s known to be carcinogenic to animals and 1s suspected of
being carcinogenic to humans. Data are sufficient for derivation of a
q,*; therefore, It 1s Inappropriate to derive an RfD_ for this chemical.
6.2. REFERENCE DOSE (RfD)
Chloroform Is known to be carcinogenic to animals and 1s suspected of
being carcinogenic to humans. Data are sufficient for derivation of a
q,*; therefore, 1t Is Inappropriate to derive an RfD for this chemical.
6.3. CARCINOGENIC POTENCY (q.,*)
6.3.1. Oral. The CRAVE work group (EPA, 1987) validated a q^ of
6.1xlO~a (mg/kg/day)"1 based on the Incidence of kidney tumors 1n male
rats exposed 1n drinking water 1n the study by Jorgenson et al. (1985). The
upper bound estimate of cancer risk for exposure to 1 yg/L of chloroform
1n water Is 1.7xlO~7.
In this revaluation, 1t was concluded that oral exposure In the drink-
Ing water approximated potential human exposure more appropriately than did
gavage exposure using an oil vehicle. For this reason, the Jorgenson et al.
(1985) study was selected as the basis for potency estimation as compared to
a previous estimate which utilized data from NCI (1976) as the basis.
6.3.2. Inhalation. Data regarding the cardnogenlclty of Inhaled
chloroform 1n humans and animals were not available. Studies 1n animals
Indicate that chloroform 1s carcinogenic by the oral route. NCI (1976)
found dose-related Increased Incidences of hepatocellular carcinoma 1n male
and female mice treated by gavage at time-weighted average (TWA) doses of
>138 mg/kg/day 5 days/week for 78 weeks, and a dose-related Increased
Incidence of kidney epithelial tumors 1n male rats similarly treated by
001 OH -22- 04/12/88
-------
gavage at 90 and 180 mg/kg/day. Roe et al. (1979) found an Increased
Incidence of kidney epithelial tumors In male mice given 60 mg/kg/day 6
days/week for 78 weeks. Dose-related Increased Incidences of renal tubular
cell adenomas and/or carcinomas were found 1n male rats treated with chloro-
form In the drinking water at levels equivalent to dosages >38 mg/kg/day for
104 weeks (Jorgenson et al., 1985).
The U.S. EPA (1985a) considered these five data sets 1n determining the
q,* for chloroform. The five data sets were as follows: 1) liver tumors
1n female mice (NCI, 1976), 2) liver tumors 1n male mice {NCI, 1976), 3)
kidney tumors In male rats (NCI, 1976), 4) kidney tumors 1n male mice (Roe
et al., 1979), and 5) kidney tumors 1n male rats (Jorgenson et al., 1985).
U.S. EPA (1985a) used available pharmacoklnetlc data to calculate an
effective close for these studies, assuming that the amount metabolized to
reactive metabolites Is the gavage dose minus the amount excreted
unchanged. For mice given 60 mg/kg, as 1n the Roe et al. (1979) study, the
correction was 6%. For rats at the same dosage, It was 20%. In the NCI
(1976) study 1n which rats and mice received doses of ~200-500 mg/kg/day, a
20% correction was considered conservative and would probably overestimate
the amount metabolized from these doses. U.S. EPA (1985a) used these
correction factors to reduce the administered dose by the unmetabollzed
portion (6% 1n mice and 20% In rats when given as a bolus by gavage 1n corn
oil, 0% when administered 1n drinking water). Doses were also corrected for
differences between animal and human pharmacoklnetlcs by using a surface
area correction. Using these corrected doses, maximum likelihood estimates
of the parameters of the multistage model were calculated for each of the
five data sets. U.S. EPA (1985a) chose the mouse liver tumor data from the
NCI (1976) study as the basis of the potency factor for Inhalation exposure
001 OH -23- 04/12/88
-------
to chloroform. The NCI (1976) study Is considered to be appropriate for use
1n the Inhalation risk estimate because there were no Inhalation cancer
bloassays and no pharmacoklnetlc data to contralndlcate the use of gavage
data (U.S. EPA, 1987b). The geometric mean of the estimates for male and
female mice In the NCI (1976) study, 8.1xlO~2 (mg/kg/day)'1, was
recommended as the Inhalation q * for chloroform. U.S. EPA (1985a)
combined the estimates for both data sets because the data for males
Included observations at a lower dose, which appeared to be consistent with
the female data. U.S. EPA (1985a) noted that the recommended q,* was
similar to the geometric mean calculated from all five estimates and was
also similar to the estimate calculated 1f data for both sexes of B6C3F1
mice 1n the NCI (1976) study were pooled. Using q^ of 8.1xlO"2
(mg/kg/day)"1, U.S. EPA (1985) calculated upper-bound estimates of cancer
risk for exposure to 1 vg/m3 1n air to be 2.3xlO~5. This q^ for
Inhalation exposure to chloroform was validated by the CRAVE work group on
August 26, 1987 (U.S. EPA, 1987b).
001 OH -24- 04/12/88
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7. REFERENCES
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0010H -29- 01/20/88
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0010H -30- 01/20/88
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001 OH -31- 01/20/88
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Struba, R.J. 1979. Cancer and drinking water quality. Ph.D. Thesis,
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001 OH -33- 01/20/88
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001 OH -34- 04/13/88
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drinking water chlorlnatlon and Wisconsin female cancer mortality. J. Natl.
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1980. Persistent organic pollutants In river water and ground water of the
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0010H -35- 01/20/88
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