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United Slates , pffr
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, ^u nnin
Environmental Protection /'"'' I ECAU-CIN-UU 12
Agency _ . _ August, 1988
' -- ' - 1 I ! KevUed December , |yy|
Research and m
Development
DRINKING WATER CRITERIA DOCUMENT
FOR TRICHLOROBENZENES
Prepared for
OFFICE OF WATER
Prepared by
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Cincinnati, OH 45268
DRAFT: DO NOT CITE OR QUOTE
. NOTICE
This document Is a preliminary draft. It has not been formally released
by the U.S. Environmental Protection Agency and should not at this stage be
construed to represent Agency policy. It 1s being circulated for comments
on Us technical accuracy and policy Implications.
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
-------
'' ?
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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FOREWORD
Section 1412 (b)(3)(A) of the Safe Drinking Mater Act, as amended 1n
1986, requires the Administrator of the Environmental Protection Agency to
publish maximum contaminant level goals (NCLGs) and promulgate National
Primary Drinking Water Regulations" for each contaminant, which, 1n the
judgment of the Administrator, may have an adverse effect on public health
and which Is known or anticipated to occur In public water systems. The
MCLG Is nonenforceable and Is set at a level at which no known or antici-
pated adverse health effects 1n humans occur and which allows for an
adequate margin of safety. Factors considered In setting the MCLG Include
health effects data and sources of exposure other than, drinking water.
«,
This document provides the health effects basis to be considered In
establishing the MCLG. To achieve this objective, data on pharmacoklnetlcs,
human exposure, acute and chronic toxUHy to animals and humans, epidemi-
ology and mechanisms of toxldty are evaluated. Specific emphasis 1s placed
on literature data providing dose-response Information. Thus, while the
literature search and evaluation performed In support of this document has
been comprehensive, only the reports considered most pertinent In the deri-
vation of the MCLG are cited In the document. The comprehensive literature
data base 1n support of this document Includes Information published up to
1985; however, more recent data may have been added during the review
process. Editorial changes were also made 1n 1991 when this document was
finalized.
When adequate health effects data exist, Health Advisory values for less
than lifetime exposures (1-day, 10-day and longer-term, -10% of an
Individual's lifetime) are Included In this document. These values are not
used 1n setting the MCLG, but serve as Informal guidance to municipalities
and other organizations when emergency spills or contamination situations
occur.
Tudor Davis, Director
Office of Science and
Technology
James Elder, Director
Office of Ground Water
and Drinking Water
111
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DOCUMENT DEVELOPMENT
W. Bruce Pelrano, Document Manager and Principal Author
Environmental Criteria and Assessment Office, Cincinnati
U.S. Environmental Protection Agency
John dcmanec, Assistant Document Manager
Environmental Criteria and Assessment Office, Cincinnati
U.S. Environmental Protection Agency
Special Note:
This document was developed from the comprehensive Informa-
tion found In the Health Assessment Document for Chlorinated
Benzenes (EPA 600/8-84-015F).
Internal Scientific Reviewers and Contributors
David J. Relsman
Environmental Criteria and Assessment Office, Cincinnati
U.S. Environmental Protection Agency
Charles H. R1s III
Carcinogen Assessment Group, Washington, DC
U.S. Environmental Protection Agency
Seong T. Hwang
Exposure Assessment Group, Washington, DC
U.S. Environmental Protection Agency
Herbert H. Cornish
YpslUntl. Michigan
Norman M. Trleff
University of Texas Medical Branch
Galveston, Texas
Shane S. Que Hee
Department of Environmental Health
University of Cincinnati
Cincinnati, Ohio
William L. Marcus
Office of Drinking Water, Washington, DC
U.S. Environmental Protection Agency
1v
-------
Editorial Review
Erma R. Ourden
Judith A. Olsen
Environmental Criteria and Assessment Office, Cincinnati
U.S. Environmental Protection Agency
Document Preparation
Technical Support Services Staff, Environmental Criteria and Assessment
Office, Cincinnati
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TABLE OF CONTENTS
Page
I. SUMMARY 1-1
II. PHYSICAL AND CHEMICAL PROPERTIES 11-1
CHEMICAL ANALYSIS II-6
Chemical Analysis In Water II-7
Chemical Analysis In Soil, Sediment and Chemical
Waste Disposal Site Samples . II-7
Chemical Analysis In F1sh and Other Foods II-7
Chemical Analysis 1n A1r . . . . . II-8
SUMMARY 11-9
III. TOXICOKINETICS III-l
ABSORPTION III-l
DISTRIBUTION III-l
METABOLISM III-2
EXCRETION , . . . III-6
SUMMARY 111-9
IV. HUMAN EXPOSURE IV-1
V. HEALTH EFFECTS IN ANIMALS V-l
ACUTE TOXICITY V-l
SUBCHRONIC TOXICITY V-6
CHRONIC TOXICITY. . V-15
MUTAGENICITY V-17
CARCINOGENICITY V-18
REPRODUCTIVE AND TERATOGENIC TOXICITY V-19
SUMMARY V-21
VI. HEALTH EFFECTS IN HUMANS VI-1
SUMMARY VI-1
VII. MECHANISMS OF TOXICITY VII-1
SUMMARY VII-3
v1
-------
TABLE OF CONTENTS (cent.)
Page
VIII. QUANTIFICATION OF TOXICOLOGIC EFFECTS VIII-1
INTRODUCTION "... VIII-1
NONCARCINOGENIC EFFECTS . . VIII-6
QUANTIFICATION OF NONCARCINOGENIC EFFECTS . . . VIII-7
Derivation of 1-Day HA VIII-7
Derivation of 10-Day HA VIII-12
Derivation of Longer-term HA VIII-14
Assessment of Lifetime Exposure and Derivation of
a DUEL . VIII-18
CARCINOGENIC EFFECTS '. VIII-19
EXISTING GUIDELINES, RECOMMENDATIONS AND STANDARDS. ..... VIII-19
Occupational VIII-19
Transportation and Regulations VIII-20
Solid Haste Regulations VIII-20
Water . VIII-21
SUMMARY -. VIII-21
IX. REFERENCES. IX-1
-------
LIST OF TABLES
No. Title
II-l Synonyms, Trade Names and Identification Numbers of
the TMchlorobenzenes II-3
II-2 Physical Properties of the Trlchlorobenzenes. ....... II-4
II-3 Vapor Pressures and Vapor Densities of the
Trlchlorobenzenes . II-5
III-l Distribution of 14C-Labeled 1,2,4-Trlchlorobenzene
1n Rat Tissues After Oral Dosing with 181.5 mg/kg/day
for 7 Days .............. III-3
V-l Summary of Subchronlc and Chronic Toxlclty Studies
on Trlchlorobenzenes V-7
VIII-1 Summary of Subchronlc and Chronic Toxldty Studies
on Trlchlorobenzenes VIII-8
VIII-2 Toxldty Data for Threshold Estimates . . . VIII-10
VIII-3 Summary of the Data for 1,2,4-Trlchlorobenzene Used
to Derive HA and DWEL VIII-22
-------
LIST OF ABBREVIATIONS
BUN
DUEL
EPN
G-6-P
GC
GC/MS
61
LOH
LOAEL
NOAEL
NOEL
RfD
SAP
SGOT
SGPT
wt
Blood urea nitrogen
Drinking water equivalent level
0-ethyl-0-p-n1trophenyl phenylphosphothdonate
Glucose-6-phosphatase
Gas chromatography
Gas chromatography/mass spectrometry
Gastrointestinal
Intraperltoneal
Intravenous
LacUc dehydrogenase
Lowest-observed-adverse-effect level
No-observed-adverse-effect level
No-observed-effect level
Reference dose
Serum alkaline phosphatase
Serum glutamlc oxaloacetlc transamlnase
Serum glutamlc pyruvlc transamlnase
Weight
1x
-------
I. SUMMARY
The trlchlorobenzenes are a group of three chemical isomers In which
three chlorine atoms have been added to a benzene ring. The 1,2,3- and
1,3,5-trlchlorobenzenes are normally solid while 1,2,4-tMchlorobenzene Is
normally a liquid at 25°C. The trlchlorobenzenes are only slightly solu-
ble In water (6.6-34.6 mg/s, at 25°C). The trlchlorobenzenes are produced
In relatively small amounts (1.3-7 minion kg/year) and are used primarily
as chemical Intermediates, solvents, Insecticides, and coolants and Insula-
tors In electrical equipment. Analysis of the trlchlorobenzenes In water
normally Involves a solvent extraction and cleanup method followed by gas
chromatography (GC) or gas chromatography/mass spectrometry (GC/MS)
analysis. The water analysis methods are slightly modified for analysis of
trlchlorobenzenes In soil and food.
The limited comparative pharmacoklnetlc data available on the
trlchlorobenzenes prevent specification of the absorption, distribution,
metabolism and excretion of the Individual Isomers. The trlchlorobenzenes
appear to enter the systemic circulation readily by Inhalation, Ingestlon
and dermal absorption; however, data were not available to quantltate the
rates of these processes nor of any of the pharmacoklnetlc processes.
Initial distribution of the trlchlorobenzenes and metabolites 1s mainly to
the liver, kidneys and adrenals, followed by migration to adipose tissue or
metabolism to polar compounds that are more readily excreted. From the
available data, U seems relatively clear that metabolism In at least three
species has a common first step, the production of an arene oxide Inter-
mediate. Subsequent metabolic steps, however, vary among the species
examined, at least for the most studied Isomer, 1,2,4-trlchlorobenzene.
03720 1-1 04/05/91
-------
In general, the pharmacoklnetlcs of the trlchlorobenzcnes are similar to
those described for the other halogenated aromatlcs. These compounds arf
llpophlllc and their metabolism and excretion depends on their conversion to
polar Intermediates. In addition, their UpophlUc character provides for
ready absorption from the gastrointestinal tract and Initial distribution to
the more highly perfused tissues, particularly the liver, kidneys and
adrenal and thyroid glands, after which they arc either metabolized and
excreted or redistributed to adipose tissue or skin. Additional .experiments
are needed to clarify the relationship of these studies to the metabolism of
trkhlorobenzenes In humans.
The effects In mammals of acute exposure by various routes to trlchloro-
benzenes Include local Irritation, convulsions and death. Livers, kidneys,
adrenals, mucous membranes and brain ganglion cells appear to be target
organs with effects Including edema, necrosis, fatty Infiltration of livers,
Increased organ weights, porphyr'm Induction and mlcrosomal enzyme Induction.
Quantitative data on the toxic effects of trlchlorobenzene following
subchronlc exposure by various routes were obtained in a variety of
species. In general, these studies Indicate that the liver, kidney, adrenal
glands and thyroid glands are target organs. Oral gavage of
1,2,4-tMchlorobenzene at 53.5 mg/kg {10 ppm) for 95 days Induced
vacuollzatlon of the zona fasdculata of the adrenal cortex In several
rats. One study Identified 14.8 mg/kg/day of 1,2,4-tMchlorobenzene as a
no-observed-adverse-effect level (NOAEL) In rats, while another study
reported that some rats exposed by Inhalation to 1,3,5-tHchlorobenzene at
1000 mg/m3 for 13 weeks showed squamous metaplasia and focal hyperplasla
03720 1-2 01/03/92
-------
of the respiratory epithelium, which appeared to be reversible. Subchronlc
oral .-studies have also shown that the trlchlorobenzenes Induce transient
hepatic xenoblotlc metabolism and porphyrla. Subchronlc dermal exposure
resulted In mild to moderate Irritation .
One chronic study, on the effects of tMchlorobenzene painted on the
skin of mice for 2 years, reported Increased mortality 1n females at the low
dose (30)4 solution 1n acetone) and 1n both sexes at the high dose (60% solu-
tion).
Results of two reports on mutagenldty tests with Salmonella typhlmurlum
test strains were negative. However, this test system Is generally Insensi-
tive to chlorinated compounds. One cardnogen1c1ty study, a 2-year skin
painting study In mice, failed to demonstrate a conclusive tumorlgenlc ef-
fect. A multlgeneratlon study of the reproductive effects of oral exposure
of rats to tMchlorobenzene failed to show effects on reproduction. Oral
teratogenldty studies In rats showed mild osteogenlc changes 1n pups and
significantly retarded embryonic development as measured by fetal growth
parameters.
Human exposure to 1,2,4-trlchlorobenzene at 3-5 ppm causes eye and res-
piratory Irritation. The only other data on human exposure are Individual
case reports of aplastk anemia of persons exposed occupatlonally or domes-
tically.
No health advisories (HAs) or lifetime drinking water equivalent levels
(OWEIs) are suggested for the 1,2,3- and 1,3,5-tMchlorobenzene Isomers
because of Insufficient data being available for evaluation.
03720 1-3 12/23/91
-------
The 1-day HA for 1,2,4-tr1chlorobenzene of 1 mg/4 for a 10 kg child Is
based on a study In which female Wlstar rats were given single oral doses of
1,2,4-trlchlorobenzene and were then evaluated 24 hours later. The 10-day
HA for 1,2,4-trlchlorobenzene of 1 mg/i for a 10 kg child Is based on a
study 1n which male CD rats were given 1,2,4-trkhlorobenzene for 14 days
and were then evaluated for effects. The longer-term HAs for
1,2,4-trlchlorobenzene of 1 mg/i for a 10 kg child and 5 mg/8, for a 70
kg adult are based on a study In which CD-I rats were exposed orally to
1,2,4-trlchlorobenzene for 95 days and evaluated for reproductive effects
and organ weight changes. A DUEL for 1,2,4-trlchlorobenzene of 0.4 mg/a,
for a 70 kg adult Is derived from an RfD of 0.01 mg/kg/day (verified
12/12/91) from the same 95-day reproductive study. The data available on
1,2,4-trlchlorobenzene Is Inadequate for making any conclusions about Us
potential carclnogenlclty In humans. The tMchlorobenzenes are classified
as U.S. EPA Group D compounds at this time, that 1s, available data are
Insufficient. This Information was verified by the CRAVE workgroup 1n
October 1988.
03720 14 01/03/92
-------
II. PHYSICAL AND CHEMICAL PROPERTIES
The trlchlorobenzenes are a group of three chemical Homers 1n which
three chlorine substHuents have been added to a benzene ring. The
trlchlorobenzenes are only slightly soluble 1n water (6.6-34.6 mg/i at
25°C). The trlchlorobenzenes are produced 1n relatively small amounts
(1.3-7 million kg/year Is. the estimated 1983 production) (U.S. EPA, 1983;
Chlorobenzene Producers Association, 1984) and are used primarily as chemi-
cal Intermediates, solvents, Insecticides, and coolants and Insulators In
electrical equipment (Hawley, 1977; Sllmak et al., 1980). Trlchlorobenzenes
have been detected In all environmental media Including drinking water, and
have been found to bloaccumulate In fish (U.S. EPA, 1985). In addition to
the exposure of humans during the manufacture and use of trlchlorobenzenes,
exposure could result from Inhalation of contaminated air and Ingestlon of
contaminated food and water.
The chemical structures of the trlchlorobenzenes are shown In figure
II-l. Synonyms, trade names and Identification numbers for the trlchloro-
benzenes are found In Table II-l. Some of the physical and chemical proper-
ties of the trlchlorobenzenes are found 1n Tables II-2 and II-3. l,2,3-Tr1-
chlorobenzene Is a white crystalline solid (platelets from alcohol) that 1s
volatile with steam. It 1s slightly soluble (31.5 mg/i) at 25°C 1n water,1
slightly soluble In alcohol, soluble .In benzene and carbon dlsulflde, and
very soluble In ether (NLM, 1981a; Yalkowsky and Valvanl. 1980).
1,2,4-TMchlorobenzene Is a colorless liquid at 25°C but at somewhat
reduced temperatures may also take the form of rhombic crystals because Us
03730 II-l 09/12/88
-------
ci
ct
ci
o
,c\
o
CI
Ci
1,2,3-TRICHLOROBENZENE 1,2,4-TRICHLOROBENZENE 1,3.5-TRICHLOROBENZENE
FIGURE II-l
Chemical Structures of the TMchlorobenzenes
03730
II-2
09/24/85
-------
TABLE II-l
Synonyms, Trade Names and Identification Numbers of the Trlchlorobenzenes*
Chemical
Identification Number
Synonyms and Trade Names
1,2,3-
1,2,4-
1,3,5-
CAS No. 87-61-6
CAS No. 120-82-1
TSL No. DC2100000
CAS No. 108-70-3
ylc-Trlchlorobenzene
1,2,6-Tr1chlorobenzene
y-Tr1chlorobenzene
Benzene, 1,2,4-trlchloro-
asym-Trlchlorobenzene
TCB
Trojchlorobenzen (Polish)
1,2,4-Tr1chlorobenzol
Hostetex L-Pec
s-Trlchlorobenzene
sym-Tr1chlorobenzene
TCB
TCBA
Benzene., 1,3,5-tr1chloro-
*Source: NLM, 1981a,b, Toxicology Data Bank (TDB)
03730
II-3
09/25/85
-------
o
e
*
g' Jit.
* -So"
i- e «
5-
w ,8
£ v< e
r-
if
fO
u
* s
1? S"
in m
in w w
« 01 w i- 0i f
^ J3 "* *" »
"S. ~- o
£
Of
U
I
*rf
k
&
s s s
2%tigiiSe
u a p i. e k
03730
JI-4
09/12/88
-------
TABLE II-3
Vapor Pressures and Vapor Densities of the Trlchlorobenzenes
Chemical Vapor Pressure Specific Vapor Density
(mm Hg) (air . 1)
Trlchlorobenzene
1,2,3-
1,2,4-
1,3,5-
0.07 at 25"Ca
1 at 40°Cb
0.29 at 25°Ca
1 at 38.4°Cb
0.15 at 25°Ca
10 mm at 78°Cb
6.26b
6.26b
6.26b
aNLM, 1981a,b; 1982
bSax. 1979
03730 I1-5 09/24/85
-------
melting point occurs at 16.95°C. It possesses a distinctive odor, similar
to that of 1,4-dlchlorobenzene, and 1s considered volatile with steam (NLH,
1981b). It Is slightly soluble 1n water, 34.6 mg/i at 25°C (Yalkowsky and
Valvanl, 1980); mlsdble with benzene, petroleum ether and carbon dlsulflde;
slightly soluble In ethanol; and very soluble In dlethyl ether (NLM, 1981b).
The summer sunlight photolysis half-life for l,2;4-tr1chlorobenzene In
surface waters at 40° latitude has been calculated to be 450 years (Dulln et
al., 1986). An Information sheet (Dow Chemical Company, 1979-1980) listed a
purity of 100X for Its product. Kao and Poffenberger (1979) reported that
commercial 1,2,4-trlchlorobenzene may contain monochlorobenzene (<0.1 wt
percent) and d1- and tetrachlorobenzenes (<0.5 wt percent and <0.5 wt
percent) with the 1,2,4-trlchlorobenzene content being "
1,3,5-Trlchlorobenzene takes the physical form of white crystals or
needles. It Is very slightly soluble (6.6 mg/l at 25°C) 1n water;
sparingly soluble 1n alcohol; and soluble In ether, benzene, petroleum
ether, carbon dlsulflde and glacial acetic acid (NLM, 1982; Yalkowsky and
Valvanl, 1980).
Chemical Analysis
A solvent extraction and cleanup method followed by GC or GC/HS Is the
most commonly used method to Isolate trlchlorobenzenes from water. Methods
that are slightly modified from the analytical procedures for aquatic
samples are used for the analysis of trlchlorobenzenes 1n soil and food.
The usual sampling and analytical methods for airborne trlchlorobenzenes
Involve the adsorption and concentration of airborne vapors on sorbent-
packed cartridges followed by thermal desorptlon and GC analysis using
03730 II-6 09/12/88
-------
either flame 1on1zat1on detection, electron capture (EC) detection, or
photolonlzatlon detection. The following sections provide examples of these
analytical methods.
Chemical Analysis In Mater. The purge-trap technique does not provide
quantitative recoveries for compounds with low volatilities, such as
trlchlorobenzenes. Therefore, a solvent extraction and cleanup method Is
normally used to produce organic extracts suitable for GC/MS analysis. The
U.S. EPA (1982) (Method 612) has recommended the use of Florlsll column
chromatography as a cleanup step before the quantification of the samples by
GC with EC detector. This recommended method 1s applicable for the
determination of trlchlorobenzenes In drinking water and wastewater.
Chemical Analysis 1n Soil. Sediment and Chemical Waste Disposal Site
Samples. The solvent extraction method was used by Lopez-Avlla et al.
(1983) to determine trlchlorobenzenes 1n sediment samples. In this method,
the solvent extract was subjected to acid-base fractlonatlon. The
base/neutral fraction containing the trlchlorobenzenes was fractionated by
silica gel chromatography. The final separation and quantification was
accomplished by GC/MS. The recovery of 1,2,4-trlchlorobenzene by this
method was 67% at a spike level of 400 ng/g of dry sediment.
1 !
Chemical Analysis in F1sh and Other Foods.
F1sh The determination of trlchlorobenzenes 1n fish samples can
be accomplished by a solvent extraction method. In one method, Kuehl et al.
(1980) subjected the solvent extract to Florlsll and gel permeation on
chromatographlc separation, followed by GC/MS Identification and quantifica-
tion of tMchlorobenzene 1n fish samples.
03730 II-7 09/12/88
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Chemical Analysis In Air. Lewis and MacLeod (1982) have developed and
evaluated a portable low-volume air sampling system for Indoor air monitor-
Ing of serai volatile organic chemicals. Two types of sampling cartridges
were tested to sample for trlchlorobenzenes. The trlchlorobenzenes were
poorly trapped using a polyurethane foam (PUF) plug, with collection
efficiencies of 6.6X. However, using a dual-sorbent trap consisting of a
0.6 g layer of Tenax-GC (35-60 mesh) sandwiched 'between two 3.8 cm PUF
plugs, a collection efficiency of 98% was obtained. Theoretical detection
limits, using GC/EC detection, are expected to be at least one order of
magnitude lower (1n the range of 0.06-0.1 jig/m9). Storage stability of
the PUF cartridges was tested under adverse storage, conditions. The amount
of trlchlorobenzenes recovered from the cartridges after 15 days of storage
at 32°C was 57X. Oehme and Stray (1982), however, reported high recoveries
of 80, 94 and 115X for 1,2,3-, 1,2,4- and 1,3,5-tMchlorobenzenes, respec-
tively, with PUF plugs.
Langhorst and Nestrlck (1979) used an air sampling tube packed with two
sections of Amber 1 He XAD-2 resin separated by a sllanlzed glass wool plug
to collect the trlchlorobenzenes. The adsorbent was desorbed with carbon
tetrachloMde and analyzed by GC using a photolonlzatlon detector. Using
N
the method described, the minimum detection limits for the trlchlorobenzenes
were 30 ppb (v/v). Collection and desorptlon efficiencies for the chloro-
benzenes (air concentrations between 5 ppb and 15 ppm) were -95% with a
precision of +12%.
03730 11-8 09/24/85
-------
Summary
The trlchlorobenzenes are a group of three chemical Isomers In which
three chlorine substUuents have been added to a benzene ring. The 1,2,3-
and 1,3,5-trlchlorobenzenes are normally solid while 1,2,4-trlchlorobenzene
1s normally a liquid at 25°C. The trlchlorobenzenes are only slightly
soluble 1n water (6.6-34.6 mg/l at 25°C). The trlchlorobenzenes are
produced 1n relatively small amounts (1.3-7 million kg/year) and are used
primarily as chemical Intermediates, solvents, Insecticides, and coolants
and Insulators 1n electrical equipment. Analysis of the trlchlorobenzenes
1n water normally Involves a solvent extraction and cleanup method followed
by GC or GC/MS analysis. The water analysis methods are slightly modified
for analysis of trlchlorobenzenes 1n soil and food.
03730 II-9 09/24/85
-------
III. TOXICOKINETICS
Absorption
No quantitative studies on the absorption of the tMchlorobenzenes from
the gastrointestinal tract, skin or lungs were found. Information on
absorption may be obtained from data describing elimination. Hale Charles
River rats (16 In the group) excreted a mean of 84%, and two female rhesus
monkeys excreted a mean of 4054 of the orally (by gavage) administered dose
of 10 mg 14C-l,2,4-tr1chlorobenzene/kg In the 24-hour urine, while fecal
elimination accounted for only 11 and IX, respectively (Llngg et a!., 1982).
The results Indicate that 1n these species, this Isomer Is well absorbed
from the gastrointestinal tract. Two Chinchilla female rabbits given doses
of 500 mg 1,3,5-tMchlorobenzene/kg 1n arachls oil by gavage expired -10% of
the administered dose via the lungs over a period of 9 days (Parke and
Williams, 1960). These Investigators also observed elimination of urinary
and fecal metabolites, but quantities or percentages were not reported.
That the trlchlorobenzenes are absorbed by the respiratory tract and by
the skin can be Inferred from systemic effects observed In toxldty studies
using the Inhalation (Koclba et al., 1981) and dermal (Brown et al., 1969)
routes of exposure,. These studies, however, were not designed to give
Information on rates of absorption.
Distribution
Smith and Carlson (1980) examined the distribution of "C-l,2,4-tr1-
chlorobenzene In groups of four male Sprague-Dawley rats on days 1, 6, 11
and 16 after oral dally dosing with 181.5 mg/kg (1 mmol/kg) 1n corn oil for
03740 III-l 09/26/85
-------
7 days. Their data Indicate that the adrenals Initially had the highest
concentration of radlolabel. This level declined rapidly; however, by day
11 U was less than twice the background of the other tissues. Abdominal
fat had the highest concentration at the end of day 1 (Table III-1) and
maintained detectable concentrations (20% of the day 1 level) for the
duration of the observation period (16 days). The liver also maintained
«
detectable levels throughout the recovery period, retaining -30X of the day
1 level by day 16. These authors also found that starvation for 4 days had
no observed effect on the distribution of l4C-tr1chlorobenzene In fat or
liver.
Parke and Williams (1960) reported the distribution of 1,3,5-trlchloro-
benzene In one rabbit on day 8 following oral administration, of a single
dose of 500 mg/kg as follows: 13% of the administered dose was detected In
the feces, 23X (454 as monochlorobenzene) In the gut, 5% 1n the pelt, 5% In
depot fat (exclusive of pelt) and 22% 1n the carcass.
Metabolism
No metabolic studies following the Inhalation of tMchlorobenzenes were
available for review, but the metabolic fate following oral and/or Intra-
venous (1.v.) or 1ntraper1toneal (1.p.) administration has been charac-
terized 1n rabbits (Jondorf et al., 1955; Parke and Williams, 1960; Kohll et
al.( 1976) and In rats and monkeys (Llngg et al., 1982).
Jondorf et al. (1955), using spectrophotometMc analysis, studied the
metabolism of all three Isomers of tMchloropenzene In groups of 3 or 4
Chinchilla rabbits given a single oral dose of 500 mg/kg 1n arachls oil.
03740 III-2 09/26/85
-------
TABLE III-l
Distribution of 14C-Labe1ed 1,2,4-TMchlorobenzene In Rat Tissues
after Oral Dosing with 181.5 mg/kg/day for 7 Days3
Activity (dom/q t1ssue)b
Tissue
Abdominal fat
Liver
Adrenals0
Muscle
Kidney
Heart
Spleen
Day 1
2033±439
1075±87
754*132
400+30
1471+167
438+14
404+14
Day 6
642+54
442+22
246+22
d/
404+43
d/
d/
. Day 11
342+10
308+21
d/
d/
Day 16
408±39
317+18
aSource: Smith and Carlson, 1980
bEach value 1s the mean + SE for 4 rats, except for abdominal fat on day 1,
which was for three rats.
cTotal for both adrenals; they were not weighed.
dValue less than twice background; further analyses were not performed.
03740
III-3
06/11/85
-------
The results Indicated that the 1,2,3- Isomer was metabolized to 2,3,4-trl-
chlorophenol (TCP), to 3,4,5-TCP to a lesser degree, and to small amounts of
3,4,5-trlchlorocatechol. During the 5 days after administration, 50% of the
dose was excreted 1n the urine as glucuronlc add conjugates, 12% as sul-
furlc add (sulfate) conjugates and 0.3% as 2,3,4-trlchlorophenylmercapturlc
add. The 5-day urinary metabolites of 1,2,4-tr1chlorobenzene were repre-
sented by glucuronlde conjugates (27%), sulfurlc add conjugates (11%) and ,
2,3,5- and 2,4,5- tMchlorophenylmercapturlc add (0.3%). The major phenols
formed were 2,4,5- and 2,3j5-TCP. For the 1,3,5- Isomer, 20% was excreted
as glucuronlde and 3% as sulfudc add conjugates. No mercaptuMc acid was
found, 2,4,6-trUhlorophenol was the only phenol detected In the urine, and
some unchanged 1,3,5-trlchlorobenzene was present In the feces. To further
characterize and clarify the metabolic fate of the 1,3,5- Isomer, Parke and
/
Williams (I960) followed the 9-day urinary excretion In 2 or 3 female Chin-
chilla rabbits treated orally with a single dose of 500 mg of the Iso-
mer/kg. For the first 3 days, the rabbits eliminated 2,4,6-TCP along with
some minor monochlorophenols, while from day 4 to 9, 4-chlorophenol was
detected more prominently along with 2,4,6-TCP and -1% of the dose as
4-chlorocatechol.
Using GC/MS analysis, KohH et al. (1976) examined the metabolism of the
three trlchlorobenzene Isomers following a single l.p. Injection of 60-75^
mg/kg doses 1n vegetable oil to male rabbits {number and strain not
reported). In agreement with the results of Jondorf et al. (1955), the
i
major urinary metabolites of 1,2,4-tdchlorobenzene were 2,4,5- and
2,3,5-TCP. The major metabolite of 1,2,3-trlchlorobenzene was 2,3,4-TCP,
with 2,3,6- and 3,4,5-TCP as minor urinary metabolites. The 1,3,5- Isomer
03740 III-4 09/12/88
-------
was metabolized to 2,3,5- and 2,4,6-TCP and a third, more polar metabolite,
V
was tentatively Identified as a dlchlorobenzene with 2 hydroxyl and 1
methoxyl substHuents.
L1ngg et al. (1982) Investigated the metabolism of 1,2,4-trlchloroben-
zene In groups1 of 16 male Charles River rats and groups of 2 female rhesus
monkeys following a single oral or l.v. administration of 10 mg/kg doses and
found similar phenolic metabolites to those observed In the rabbit. These
f
researchers were also able to characterize some species specific conjugates.
An Isomerlc pair of 3,4,6-tr1chloro-3,5-rcyclohexad1ene-l,2-d1ol glucuronldes
accounted for 48-61% of the 24-hour urinary metabolites In the monkeys.
Also found were glucuronldes of 2,4,5- and 2,3,5-TCP and unconjugated TCP,
which accounted for 14-37 and 1-37% of the urinary metabolites, respec-
tively. In the rat, the 2,4,5- and 2,3,5- Isomers of N-acetyl-S-(tr1chloro-
phenyl)-L-cyste1ne accounted for 60-62% of the urinary metabolites. Minor
urinary metabolites Included 2,4,5- and 2,3,5-trlchlorothlophenol and free
2,3,5- and 2,3,4-TCP, which accounted for 28-33 and 1-10% of the material
excreted, respectively.
On the basis of the studies of Llngg et al. (1982) and KohH et al.
(1976), It 1s apparent that there may be differences among species In the
i
metabolism of 1,2,4-tr1chlorobenzene. It seems likely that these differ-
ences will extend to the other Isomers of trlchlorobenzene as well. Both
reports postulated the same first step 1n metabolism (I.e., Initial forma-
tion -of arene oxide Intermediates), but Indicated differences 1n the subse-
quent metabolic reactions. In the rat, conjugation of the Intermediate with
glutathlone was postulated to account for the sulfur-containing urinary
03740 III-5 06/11/85
-------
metabolites. In the monkey, hydrolysis of the arene oxide to the dlhydro-
dlol and the absence of sulfur-containing metabolites seemed to preclude the
Involvement of glutathlone (L1ngg et al., 1982). As proposed by Kohll et
al. (1976) and Illustrated 1n Figure III-l, formation of the Isomerlc tr1-
chlorophenols from the arene oxide Intermediates can proceed either by
direct opening of the C-0 bond or by the NIH shift of chlorine.
Differences 1n the rate of metabolism of the different Isomers within a
species have been attributed to the positions of the chlorine atoms on the
benzene ring, with the presence of two adjacent unsubstltuted carbon atoms
facilitating the formation of the arene oxide Intermediate. Halogenated
benzenes without adjacent unsubstltuted carbons may still be metabolized via
an arene oxide Intermediate but at a reduced rate, and should show evidence
of a NIH shift (Matthews and Kato, 1979).
Excretion
Ungg et al. (1982) measured the 24-hour excretion of radioactivity In
the urine and feces of 16 male Charles River rats and 2 rhesus monkeys given
a single 10 mg/kg 1.v. or oral dose of 14C-1,2,4-trUhlorobenzene. In the
rat, 84% of the oral dose and 78% of the 1.v. dose were excreted In the
urine by 24 hours; 11 and 7%, respectively, were the amounts Identified In
the feces In the same period. In the monkeys, 40% of the oral dose and 22%
of the Injected dose'appeared 1n the urine and <1% 1n the feces. Smith and
Carlson (1980) orally administered 181.5 mg/kg/day (1 mmol/kg/day) of
l4C-l,2,4-tr1chlorobenzene 1n corn oil to 4 Sprague-Dawley rats for 7 days
and followed the excretion of radioactivity 1n the feces and 1n the urine
during administration and up to 21 days after the first dose. Fecal elimi-
nation rose slightly during the first 3 days of dosing, after which It
03740 111-6 09/26/85
-------
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03740
III-7
06/11/85
-------
declined rapidly and was essentially complete at 15 days of collection,
accounting for ~4% of the total dose. Urinary excretion followed a similar
pattern; however, at 21 days after the first dose, radioactivity was still
detectable. Total urinary excretion to this time accounted for ~72% of the
total administered radioactivity. As noted by L1ngg et al. (1982), the
differences In the excretion rate between the rat and monkey may be
attributable to their different pathways of metabolism, since the monkey
required two steps beyond the arene oxide to produce Us urinary metabolite,
while the rat required only one.
Differences In the rates of excretion between the Isomers of trlchloro-
benzene have also been reported. Jondorf et al. (1955) found that rabbits
given oral doses of 500 mg/kg of 1,2,3-, 1,2,4- or 1,3,5-trlchlorobenzene
excreted 78, 42 or 9X, respectively, of the administered dose as monophenols
In the 5-day urine collection.
U.S. EPA (1980), using data from Williams (1959) and Parke and Williams
(I960), estimated the following half-lives of excretion 1n the rabbit: 2,
5.5 and 8.5 days for 1,2,3-, 1,2,4- and 1,3,5-tr1chlorobenzene, respec-
tively. The rate of metabolism and subsequent excretion Is most likely
related to the position of the chlorine atoms on the benzene ring. Matthews
and Kato (1979) hypothesized that two adjacent unsubstUuted carbon atoms
facilitate the formation of the arene oxide Intermediate and Increase the
i
rate of metabolism and excretion.
03740 II1-8 08/24/88
-------
Summary
The limited comparative pharmacoklnetlc data available on the trlchloro-
benzenes prevent specification of the absorption, distribution, metabolism
and excretion of the Individual Isomers. The tMchlorobenzenes appear to
enter the systemic circulation readily by Inhalation, Ingestlon and dermal
absorption; however, data were not available to >quant1tate the rates of
these processes nor of any of the pharmacoklnetlc processes. Initial dis-
tribution of the trlchlorobenzenes and metabolites 1s mainly to the liver,
kidneys and adrenals, followed by migration to adipose tissue or metabolism
to polar compounds that are more readily excreted. From the available data,
H seems relatively clear that metabolism In at least three species has a
common first step, the production of an arene oxide Intermediate. Subse-
quent metabolic steps, however, vary among the species examined, at least
for the most studied Isomer, 1,2,4-tMchlorobenzene.
In general, the pharmacoklnetlcs of the trlchlorobenzenes are similar,to
those described for the halogenated aromatlcs by Matthews and Kato (1979).
The authors observed that these compounds are llpophlllc and that their
metabolism and excretion depends on their conversion to polar Intermedi-
ates. In addition, their 11poph1l1c character provides for ready absorption
from the gastrointestinal tract and Initial distribution to the more highly
perfused tissues, particularly the liver, after which they are either metab-
olized and excreted or redistributed to adipose tissue or skin. Additional
experiments are needed to clarify the relationship of these studies to the
metabolism of trlchlorobenzenes 1n humans.
03740
III-9
09/26/85
-------
IV. HUNAN EXPOSURE
This chapter will be submitted by the Science and Technology Branch,
Criteria and Standards Division, Office of Drinking Water.
03750 IV-1 06/11/85
-------
V. HEALTH EFFECTS IN ANIHALS
Acute Toxldtv
Studies of the acute toxlclty of the trUhlorobenzenes have been
performed 1n several species using various routes of administration.
Information on the effects of acute Inhalation exposure to tMchloroben-
zenes 1s limited. In an abstract of a study from the Russian literature
(Gurfeln and Pavlova, I960), a single high Inhalation exposure (exposures of
0.005-0.01 mg/i 1n air or 5-10 mg/m3 were used) of an unspecified Isomer
of trlchlorobenzene to rats resulted In Immediate nervousness, and plnkness
of mouth, ears and paws. These effects were followed by convulsions and
death within 30 minutes, with edema of livers and kidneys observed upon
necropsy. Unpublished results of a study performed by Treon (1950) were
reported by Coate et al. (1977) and Indicated that the target organs of non-
lethal acute Inhalation exposure to trlchlorobenzenes (a weight-to-weight
mixture of 8% 1,2,3- and 92X 1,2,4-tMchlorobenzene) 1n cats, dogs, rats,
rabbits and guinea pigs Included the liver, ganglion cells at all levels of
the brain, and mucous membranes. Lethal doses resulted In local Irritation
of the lungs and functional changes 1n respiration In animals dying after
exposure. Levels and duration of exposure were not given.
Brown et al. (1969) reported the single-dose oral L05Q for 1,2,4-tM-
chlorobenzene In CFE rats to be 756 mg/kg (95X confidence limits 556-939
mg/kg). In CF mice, the single-dose oral LD5Q was 766 mg/kg (95X confi-
dence limits 601-979 mg/kg). Death occurred within 5 days In rats and 3
/
days 1n mice.
03760 V-l 09/12/88
-------
R1ra1ngton and Zlegler (1963) studied the porphyrla-lnduclng ability of
1,2,4- and 1,2,3-trlchlorobenzenes administered by gavage to male albino
rats for various time periods (5-15 days). Doses of the 1somers,were gradu-
ally Increased until porphyMn excretion was high but fatalities were few.
PorphyMa was Induced by 1,2,4-tMchlorobenzene when the Isomer was given
for 15 days at 730 mg/kg (3 rats) as evidenced by peak elevations 1n urinary
coproporphyrln, uroporphyMn, porphoblUnogen and 4-am1nolevul1n1c acid.
At a dose of 500 mg/kg for 10 days (1n 5 rats), peak liver levels of copro-
porphyrln, protoporphyMn, uroporphyMn and catalase were reached. For the
l,2,3-1somer, urinary excretion of these Indicators peaked at 785 mg/kg for
7 days (3 rats), but to a lesser extent than for the 1,2,4-1somer. Only the
liver uroporphyrln levels were Increased by administration of 1,2,3-tM-
chlorobenzene at this dose and duration. Glutathlone was found to have a
protective effect on tr1chlorobenzene-1nduced porphyMa.
Brown et al. (1969) determined the single-dose percutaneous ID In
CFE rats (4 of each sex) to be 6139 mg/kg (95X confidence limits 4299-9056
mg/kg) for 1,2,4-tMchlorobenzene administered topically on the shaved
dorsolumbar skin and covered with an Impermeable dressing. All deaths
occurred within 5 days. In skin Irritation studies, 1,2,4-trlchlorobenzene
was applied to the skin of rabbits and guinea pigs. In the first experi-
ment, two 2x2 cm patches of Hnt, each containing ,1 ma, of the compound,
were applied to the shaved backs of rabbits (4 of each sex) for 6 hours/day
for 3 consecutive days and covered with an Impermeable dressing. For
another experiment, rabbits (1 of each sex) and guinea pigs (5 of each sex)
received single uncovered applications of 1,2,4-tMchlorobenzene on the
shaved mlddorsal skin (1 ma for rabbits, 0.5 ms, for guinea pigs) 5
/
03760 V-2 09/25/85
-------
days/week for 3 weeks. The results Indicated that tMchlorobenzene was not
very Irritating, although flssurlng was noted during the 3-week exposure.
Some guinea pigs that died during the 3-week regimen had focal necrosis of
the liver.
Hepatotoxlc effects (fatty Infiltration and necrosis) were reported by
Cameron et al. (1937) following s.c. and/or 1.v. Injection of 500 mg (range
of doses was 1-500 mg) trlchlorobenzene In liquid paraffin to rats; the
toxUHy was less than that of mono- and o-d1chlorobenzene. Further details
of strain, number of animals or Isomers were not reported.
Robinson et al. (1981), In an acute toxlclty study to assess the
Increased adrenal weight that was noted 1n a mult1generat1on study, admin-
istered to groups composed of 9-10 preweanlng female Charles River rats 1.p.
Injections of 0, 250 or 500 mg of 1,2,4-tr1chlorobenzene/kg 1n corn oil at
22, 23 and 24 days of age. Significant changes (p<0.05) from control values
were observed upon necropsy at 25 days of age as follows: decreased body
weight and Increased adrenal weight at the high dose; decreased uterus and
Increased liver weights at both doses.
Male Holtzman rats (number not specified) were given single Intraperl-
toneal Injections of 1,2,4- or 1,3,5-trlchlorobenzene at a dose of 37 mg/kg
(5 mmol/kg) as a SOX solution 1n sesame oil 1n a volume of 1 ml/kg (Yang
et al., 1979). Controls received an equal volume of sesame oil. After 24
hours, the femoral veins and the common bile duct were cannulated. Both
Isomers produced significant Increases (p<0.05) 1n bile duct-pancreatic
fluid (BDPF) flow with the 1,2,4- Isomer being 4 times more effective than
03760 V-3 09/25/85
-------
the 1,3,5- Homer. SGPT activity was elevated by treatment with 1,3,5-tM-
chlorobenzene and bile flow was elevated by the 1,2,4- Isomer. Both Isomers
caused a decrease 1n BDPF protein concentration.
Several studies have demonstrated the ability of the trlchlorobenzenes
to enhance xenoblotlc metabolism. Carlson, In a series of reports (Carlson
and Tardlff, 1976; Carlson, 1977a, 1978, 1981; Smith and Carlson, 1980),
examined the ability of 1,2,4-tMchlorobenzene to Induce a variety of mUro-
somal functions and enzymes Including cytochrome c reductase, 0-ethyl
0-p-nltrophenyl phenylphosphothlonate (EPN) detoxification, cytochrome
P-450, glucuronyltransferase, benzopyrene hydroxylase and azoreductase. In
a 14-day study by Carlson and Tardlff (1976), dally doses of 1,2,4-trl-
chlorobenzene 1n corn oil were administered orally to groups of 6 male
albino rats at 10, 20 and 40 mg/kg. All the above functions and enzymes
Increased significantly (p<0.05) except benzopyrene hydroxylase. In a
90-day study by the same Investigators, all the functions and enzyme
activities, Including benzopyrene hydroxylase, : Increased significantly
(p<0.05) at 10-40 mg/kg/day and remained significantly elevated after a
30-day recovery period. In a similar study, Smith and Carlson (1980)
administered 1,2,4-trlchlorobenzene at 181.5 mg/kg/day (1 mmol/kg/day) to
rats for 7 days, and measured recovery at 1, 6, 11 and 16 days. EPN
detoxification was still significantly (p<0.05) elevated at 11 days;
p-n1troan1sole demethylatlon at 16 days; cytochrome c reductase at 6 days;
and cytochrome P-450 at 11 days. In a similar study by Carlson (1977a),
14-day administration of 1,3,5-tMchlorobenzene at 100-200 mg/kg/day signif-
icantly (p<0.05) Increased EPN detoxification, UDP glucuronyltransferase.
and cytochrome c reductase, and significantly decreased hepatic G-6-P;
03760 V-4 08/24/88
-------
benzopyrene hydroxylase, azoreductase and serum 1soc1trate dehydrogenase
were not significantly affected at 200 mg/kg/day., ,In the same study,, \n
vivo hepatotoxldty of carbon tetrachloMde (one dose of 0.5 ml/kg) was
significantly (p<0.05) enhanced by 14-day pretreatment of rats with
1,2,4-tMchlorobenzene. Glucose-6-phosphatase activity_ was. significantly
(p<0.05) decreased by pretreatment with 1,2,4-trlchlorobenzene at 5
mg/kg/day, and Vsodtrate dehydrogenase was decreased by pretreatment at 20
rag/kg/day.
The 1,2,4- Isomer, and to a lesser extent the,1,3,5- Isomer, were also
shown to Induce hepatic esterases (Carlson et a!., 1979; Carlson, 1980). In
studies similar to those previously described, rats receiving dally oral
doses of 18.2 mg Isomer/kg (0.1 mmol/kg) for 14 days were killed 24 hours
later and hepatic mlcrosomes were prepared. The l,2,4-1somer was an
effective Inducer of both acetanlllde esterase and acetanlUde hydroxylase,
while the 1,3,5-lsomer Induced only the esterase .and to a lesser degree than
did 1,2,4-tMchlorobenzene (Carlson et al., 1979). The l,2,4-1somer also
Induced hepatic arylesterase, while 1,3,5-trlchlorobenzene did not (Carlson,
1980}. Pretreatment of rats with 181.5 mg/kg/day (1 mmol/kg/day) of either
Isomer resulted 1n Induction of procalne esterase (Carlson et al., 1979).
i
In a series of experiments, AMyoshl et al. (1975a,b,c) studied the
effects of the trlchlorobenzenes on Induction of hepatic mlcrosomal pro-
teins, phosphollplds and enzymes, especially 1n relation to the activity of
4-am1nolevul1n1c add synthetase, the rate limiting enzyme 1n the bio-
synthesis of heme. The three trlchlorobenzene Isomers were administered
orally to groups of 2-6 female Ulstar rats at a dose of 250 mg/kg/day for 3
days, after which the rats were killed and mlcrosomes were prepared. The
03760 V-5 09/24/85
-------
results Indicated that trlchlorobenzenes Increased the levels of microsomal
proteins, phosphollplds and cytochrome P-450, and enhanced the activities of
aniline hydroxylase, aminopyrlne demethylase and $-aminolevul1nic acid
synthetase, with the l',2,4-1somer being the most effective (Arlyoshl .et al.,
1975a,b).. The dose response of these effects to 1,2,4~tr1chlorobenzene were
determined (Arlyoshl et al., 1975c) for groups of 2-6 female Wlstar rats
treated orally with single doses of 0, 125, 250, 500, 750, 1000 and 1500
fng/kg. The results Indicated that 24 hours after the administration of the
Isomer, mlcrosomal protein was elevated at >750 mg/kg and glycogen content
was decreased at >500 mg/kg. The activities of amlnopyrlne demethylase and
aniline hydroxylase and the content of cytochrome P-450 were Increased at
>250 mg/kg, as was 6-am1nolevul1nic acid synthetase activity.
Subchronlc Toxlclty
The effects of trlchlorobenzene following subchronlc Inhalation, as well
as oral and dermal exposure, have been Investigated In a variety of species.
Toxlclty data for the trlchlorobenzenes can be found In Table V-l.
Kodba et al. (1981) exposed 20 male Sprague-Dawley rats, 4 male New
Zealand rabbits and 2 male beagle dogs by Inhalation to 1,2,4-trichloroben-
zene (99.4X pure) at levels of 0, 223 mg/m3 (30 ppm) or 742 mg/m3 (10
ppm) for 7 hours/day, 5 days/week for a total of 30 exposures In 44 days.
There were no significant effects on body weight, hematologic Indices or
serum biochemistry tests. Upon necropsy, gross and comprehensive hlstologlc
examination revealed no significant treatment-related effects In any of the
species. At the 742 mg/m3 level, increased liver weights were detected In
dogs and rats and Increased kidney weights In rats. Urinary excretion of
03760 V-6 04/05/91
-------
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-------
porphyrln was Increased 1n rats exposed to 1,2,4-tMchlorobenzene at 223 or
742' mg/m3, which the Investigators Interpreted as a compound-specific
physiologic effect rather than a toxic effect. A follow-up study supported
this Interpretation. The same Investigators exposed male and female
Sprague-Dawley rats to 1,2,4-tMchlorobenzene at 0, 22.3 mg/m3 (3 ppm) or
74.2 mg/m3 (10 ppm) for 6 hours/day, 5 days/week for 3 months. The
results, which were reported In an abstract (Watanabe et al., 1978),
Indicated that urinary excretion of porphyrlns was slightly increased In the
74.2 mg/m3 group during exposure, but returned to control range 2-4 months
postexposure. Since this appeared to be the most sensitive Indicator In
rats, and exposure to trlchlorobenzene at 22.3 mg/m3 did not cause
Increased porphyrln excretion, 22.3 mg/m3 was considered a no-observed-
adverse-effect level (NOAEL) for rats by the authors.
Sasmore et al. (1983) exposed male and female outbred albino CO rats
(20/group) to 1,3,5-tMchlorobenzene vapor at 0, 10," 100 or 1000 mg/m3 for
6 hours/day, 5 days/week for up to 13 weeks. No significant effects were
observed -on body weights, food consumption, standard hematologlc and clini-
cal chemistry parameters or on methemoglobln and porphyrln levels. In a
subgroup of five animals/sex/group killed after 4 weeks of exposure, the
only altered experimental parameter was an Increase In the I1ver-to-body
weight ratios In the male 1000 mg/m3 group, but this effect was not
observed at 13 weeks. Since gross and microscopic pathologic examinations
of the liver revealed no treatment-related abnormalities, the authors
concluded that the exposure did not cause hepatotoxUlty. Microscopic
examinations, however, revealed that three high-dose rats had squamous
metaplasia and focal hyperplasla of the respiratory, epithelium, which the
authors believed to be reversible.
03760 V-9 04/05/91
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Coate et al. (1977) exposed groups of 30 male Sprague-Dawley rats, 16
male New Zealand rabbits and 9 male monkeys (Hacaca fasdculaMs) to 99.07%
pure 1,2,4-tMchlorobenzene vapor at levels of 0, 186 mg/m3 (25 ppm), 371
mg/m3 . (50 ppm) or 742 mg/m3 (100 ppm) for 7 hours/day, 5 days/week for
26 weeks. Pulmonary function and operant behavior tests In the monkeys,
ophthalmic examinations In the rabbits and monkeys, and measurements of body
weight, hematologlc Indices and serum biochemistry parameters In all species
were conducted before and during the exposure period. Subgroups of 5 rats
each were killed after 4 and 13 weeks of exposure; all remaining rats were
killed after 26 weeks for hlstologlc examination of selected tissues. No
treatment-related effects at any observation time were seen with respect to
body weight, survival, hematology or serum chemistry for any of the
species. No ophthalmic changes were observed In rabbits or monkeys. Pul-
monary function and operant behavior were unaffected 1n monkeys. Hlstologlc
examination of rat tissues revealed that treated animals had enlarged
hepatocytes that were more prominent at 4 weeks, than at 13 weeks after expo-
sure, and at 371 and 742 mg/m3 than at 186 mg/m3. Other changes In
treated rats that did not appear to be dose-dependent were vacuollzatlon of
.1 ' ;
hepatocytes at 4 and 13 weeks, slightly more severe granuloma of the liver
at 4 weeks and biliary hyperplasla at 4 and 13 weeks. A nondose-related 1n-
i :
crease 1n the severity of kidney hyaline degeneration was observed 1n test
rats at 4 weeks. This lesion was slightly more severe In the high-dose
group at 13 weeks. These effects appeared to be transient; rats necropsled
after 26 weeks of exposure had none of these changes. Likewise, hlstologlc
examination of selected tissues from rabbits and monkeys revealed no
treatment-related changes after 26 weeks of exposure.
03760 V-1Q 04/05/91
-------
Carlson- and Tardlff (1976) assessed the effects of 14- or 90-day oral
administration of 1,2,4-trlchlorobenzene In corn oil compared with corn oil
controls 1n male CO rats. In the 14-day studies, the effects examined were
lethality, hepatotoxlclty and the Influence on hexabarbltal sleeping time
and other parameters of xenoblotlc metabolism. A dose of 600 mg/kg/day, the
highest dose administered, caused no deaths during the 14-day administration
period. Hepatotoxlclty was evaluated by dosing at 0, 150, 300 or 600
mg/kg/day and determining serum IsocHrate dehydrogenase and liver glucose-
6-phosphatase activities. Although no dose-related changes In serum Iso-
cHrate dehydrogenase activity was observed, liver glucose-6-phosphatase
activity was significantly decreased at >300 mg/kg (p<0.05). Hexabarbltal
sleeping time was significantly decreased at 600 mg/kg/day (the only dose
examined); this effect persisted through a 14-day recovery period. In rats
receiving 14 dally doses at 0, 10, 20 or 40 mg/kg, there was a significant
dose-related Increase 1n Hver-to-body weight ratio at >10 mg/kg/day
,{p<0.05). Significant dose-related Increases were also observed In activi-
ties or contents of cytochrome c reductase (at >10 mg/kg), cytochrome P-450
(at >20 mg/kg), glucuronyltransferase (at >20 mg/kg), azoreductase (at >10
mg/kg) and the. rate of detoxlcatlon of EPN (at >10 mg/kg). These results
Indicated that the doses, while causing a slight degree of hepatic Injury,
significantly enhanced xenoblotlc.metabolism.
In the 90-day studies by Carlson and Tardlff (1976), the effects of oral
dosing of male CO rats (6 animals/group) at 0, 10, 20 or 40 mg/kg/day with
1,2,4-trlchlorobenzene 1n corn oil on weight gain, liver weight, hemoglobin
content, packed cell volume and the Indicators of xenoblotlc metabolism were
evaluated. No effects on weight gain and no consistent alteration 1n hemo-
globin content or packed cell volume were observed. At 40 mg/kg, there was
03760 V-ll 09/24/85
-------
a statistically significant Increase (p<0.05) In llver-to-body weight ratios
that persisted throughout a 30-day recovery period. Following 90-day admin-
istration, cytochrome c reductase activity was Increased at >10 mg/kg, with
recovery after 30 days; cytochrome P-450 levels Increased at >20 mg/kg, fol-
lowed by recovery; glucuronyltransferase activity decreased at >10 mg/kg;
EPN detoxlcatlon Increased at >20 mg/kg; benzopyrene hydroxylase activity
Increased 2-fold at 40 mg/kg; and azoreductase activity Increased at >10
mg/kg. ' I
Groups of 5 female rats (strain .not reported) received dally oral doses
of 0, 50, 100 or 200 mg 1,2,4-trlchlorobenzene/kg/day In corn oil for 30,
60, 90 or 120 days (Carlson, 1977b). Significant Increases were observed 1n
liver porphyrlns at >100 mg/kg after 30 days exposure and In urinary
porphyrlns at 200 mg/kg after 30 days. For the 30-day study, slight but
significant Increases were also observed 1n liver weights at 200 mg/kg.
When the compound was administered for 60 days, only the liver weights were
Increased. The administration of 1,2,4-tMchlorobenzene for 90 days
resulted In slight but significant Increases In liver weights at >50 mg/kg,
1n liver porphyrlns at >100 mg/kg and 1n urine porphyrlns at 200 mg/kg. A
significant Increase was observed for liver porphyrlns when the compound was
given at >50 mg/kg for 120 days. The excretion of 6-am1nolevullrilc add
and porphobHlnogen 1n the urine was not Increased at any dose given for any
duration. When the author compared the 1,2,4-tMchlorobenzene results with
the results for hexachlorobenzene, he concluded that the tMchlorobenzene
Induced porphyMa was very small compared with the hexachlorobenzene Induced
porphyrla (Carlson, 1977b).
03760 V-12 09/24/85
-------
A 90-day oral study by Smith et al. (1978), reported 1n an abstract, was
reviewed by U.S. EPA (1980), who gave further details of the study after
i
communication with the authors. Rhesus monkeys (4/group) were given 1,2,4-
trlchlorobenzene 1n dally oral doses of 1, 5, 25, 90, 125 or 173.6 mg/kg.
No toxic effects were observed at <25 mg/kg, while doses, of >90 mg/kg were
observed to be toxic, and the 173.6 mg/kg dose was lethal within 20-30 days.
There were no deaths observed 1n the 1, 5 and 25 mg/kg groups; one death
occurred In each of the 90 mg/kg and 125 mg/kg, groups and two deaths
occurred In the 173.6 mg/kg group. Animals on the highest dose exhibited
severe weight loss and predeath fine tremors. All of the animals In the
highest dose group had elevated BUN, Naf, K+, CPK. SGOT, SGPT, LOH and
alkaline phosphatase as well as hypercalcemla and hyperphosphatemla from 30
days on. Smith et al. (1978) have been using the urinary pattern of chlor-
guanlde metabolites as an Indication of cytochrome P-450 dependent drug
metabolism. At the high doses, monkeys showed evidence of the hepatic
Induction as well as Increased clearance of l.v. doses of labeled 1,2,4-tM-
chlorobenzene. Further Information on the study (U.S. EPA, 1980} gave
evidence of liver enzyme Induction In the 90, 125 and 173.6 mg/kg animals.
There were some pathologic changes noted In the livers of the high-dose
t
groups, primarily a fatty Infiltration. The point at which there was no
effect related to the compound was at the 5 mg/kg level. Since only an
abstract of this study was available and since the Interpretation of this
study was complicated by the use of other drugs and weight losses In the
control animals, a valid no-observed-effect level (NOEL) cannot be derived
from these data.
03760 V-13 04/05/91
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Two subchronlc studies have assessed the dermal toxlclty of the trlchlo-
robenzenes. Powers et al. (1975) applied technical grade 1,2,4-tMchloro-
benzene at concentrations of 5 or 25% 1n petroleum ether, or 100% l,2,4-tr1-
chlorobenzene topically 1n 0.2 ml volumes to the ventral surface of the
ears of New Zealand rabbits (groups of 12 each), 3 times weekly for 13
weeks; a control group received petroleum ether only. Rabbits exposed to 5%
trlchlorobenzene and controls had slight redness and scaling. Dermal
responses at 25 and 100% of the compound Included slight to severe erythema,
severe scaling, desquamatlon, encrustation, and some hair loss and scarring.
The responses were characterized by acanthosls and keratosls, typical of
moderate to severe Irritation and probably attributable to degreaslng
(defattlng) action. No overt signs of systemic toxldty were noted, body
weight gain was comparable 1n all groups, and none of the animals showed
meaningful changes In gross pathology. The Investigators noted that this
contrasted with the findings of Brown et al. (1969), who reported that some
guinea pigs, exposed topically to 1,2,4-tr1chlorobenzene at 0.5 ml/day, 5
days/ week for 3 weeks, died following extensor convulsions and their livers
showed necrotlc fod. Th.ls difference 1n results may be attributed to the
site of application (Brown et al., 1969, used the dorsal mldHne for appli-
cation, a more extensive exposure site), the volume applied (0.5 mi vs.
0.2 ma), the species used, and the more frequent (5 times/week vs. 3
times/ week) application, although the total number of exposures was less
(5x3 weeks vs. 3x13 weeks).
Rao et al. (1982) applied technical grade trlchlorobenzene [1.2,4- (70%)
and 1,2,3-trUhlorobenzene (30%)] 5 days/week for 4 weeks, at doses of 0,
30, 150 or 450 mg/kg/day, to the dorsal skin (4x4 Inch area) of groups (5 of
each sex) of New Zealand rabbits weighing ~3 kg. One rabbit died after 18
03760 V-14 09/24/85
-------
applications, but the Investigators were unable to1 determine the cause of
death by either gross or hlstologU examination. Gross and histologic
examination of the skin showed evidence of moderate Irritation at the high-
est dose and less Irritation at the lower doses. This Irritation evidence
consisted of epidermal scaling, thickening, fissures,, ulcers and erythema.
No treatment-related change was observed 1n clinical chemistry (BUN, glu-
cose, SGPT, SAP) or hematology. A slight but significant Increase In
urinary coproporphyrln was observed 1n high-dose males (450 mg/kg/day) at
day 24; none was seen 1n femalesl This slight porphyrla and a slight gen-
eralized pallor of the liver (3/5 males, 4/4 females) were the only signs of
systemic toxlclty. Extensive histologic examination of numerous tissues
failed to show any treatment-related abnormalities. The volume of trl-
chlorobenzene applied at the dose levels 1n this study can be calculated as
-0.06 mfc (30 mg/kg), 0.31 ml (150 mg/kg) and 0.93 mi (450 mg/kg) by
multiplying the dose 1n g/kg by the weight of the rabbits (3 kg) and divid-
ing by the density of trlchlorobenzene (1.45 g/ml).
Chronic Toxlclty
No studies on the effects of the tMchlorobenzenes following chronic
oral or Inhalation exposure were available for review; however, a chronic
skin painting study was.encountered. Goto et al. (1972) conducted a 6-month
feeding study 1n mice using hexachlorbcyclohexane Isomers and their metabo-
lites, Including 1,2,4-tr1chlorobenzene. Male mice (20/group) of the
ICR-JCL strain (age at Initiation 5 weeks, average weight 26.5 g) received a
H '
diet containing 600 ppm of trlchlorobenzene (78 yg of compound/kg body
weight, assuming mice consume 13% of their body weight 1n food per day).
03760 V-15 08/24/88
-------
The weight gain of treated mice did not differ from controls during the
6-month exposure. At 26 weeks, 10 mice were killed and liver, heart and
kidneys were weighed; no abnormal weight changes were observed. Macroscopic-
and 'hlstologlc examination of the liver revealed no hepatic tumors or any
other lesions.
Yamamoto et al. (1982) studied the toxlclty of 1,2,4-trlchlorobenzene
when painted on the skin of Slciddy.mlce 2 times/week for 2 years. Groups
consisted of 75 mice/sex receiving 0.03 ml applications of the compound as
30 or 6054 solutions In acetone. Controls consisted of 50 mice/sex and
received only acetone. The skin painting produced general symptoms of
excitability and panting, local skin thickening, keratlnlzatlon and Inflam-
mation of the epidermis. These effects were not observed In controls. For
the 30% tMchlorobenzene groups, mortality was Increased 1n females (5/75
survived for 83 weeks compared with 11/50 controls). The mean survival days
were 357*125.4 for treated females compared with 423.8^145.0 for controls
(p<0.01). The survival of males at this exposure level was not signifi-
cantly different from that of controls. Spleen weights were significantly
Increased (p<0.05) and left adrenal weights were significantly decreased
(p<0.01) for treated males when compared with controls. Hematologlc and
blood chemistry Indices were essentially unchanged with the exception of
decreased red blood cell counts 1n the 3054 treated males (p<0.05) and
decreased Cl~ concentration (p<0.01). For the 60% solution, 6/75 treated
females survived for 83 weeks. Mean survival days were 320.2*147.7 for
treated females compared with 423.8*145.0 for controls (p<0.001). Eight of
75 treated males survived for 83 weeks compared with 9/50 control males.
03760 . V-16 09/25/85
-------
Hean survival days were 288.0±173.7 for treated males and 363.9+173.9 for
controls (p<0.05). Significant differences 1n organ weights from control
values were seen 1n the spleens of males (p<0.01) and the adrenals of
females (p<0.05). Hematologlc and blood biochemistry changes were seen 1n
Increased lymphocyte counts 1n treated females (p<0.05), and In Increased
SGOT (p<0.05), SGPT (p<0.001) and BUN (p<0.01) for treated males.
HutagenlcUy
Schoeny et.al. (1979) and Lawlor et al. (1979) examined the mutagenlc
potential of 1,2,4-trlchlorobenzene 1n Salmonella typh1mur1um tester strains
TA98, TA100, TA1535 and TA1537, using the plate Incorporation technique.
Schoeny et al. (1979) used 8 concentrations of trlchlorobenzene ranging from
102 tig/plate to 1.4x10* ^g/plate. The toxic dose was determined as
1599 yg/plate (killing of one or more strain on mutagenesls plates).
Trlchlorobenzene was negative for mutagenlclty In the absence and presence
of S-9 mlcrosomal fractions from unlnduced rats, from rats Induced by the
polychlorlnated blphenyl, Aroclor 1254, and from rats homologously Induced
with trlchlorobenzene.
The study of Lawlor et al. (1979), reported 1n an abstract, used the
TA1538 strain of S. typhlmurlum 1n addition to the strains previously men-
tioned. Negative results were obtained for five unspecified concentrations
tested 1n the presence and absence of rat liver mlcrosomes Induced by
Aroclor 1254. Because these results were reported 1n an abstract without
the details of the experimental procedures used, the results cannot be crit-
ically evaluated.
03760 V-17 09/25/85
-------
The negative results 1n the Salmonella hlstldlne reversion assay are not
unexpected because this test system 1s generally Insensitive to highly
chlorinated compounds (Rlnkus and Legator, 1980),
Carclnoqenldty
Yamamoto et al. (1982) applied 1,2,4-trlchlorobenzene 1n acetone to the
skin of Slc.ddy mice twice weekly for 2 years. The solution of 1,2,4-trl-
chlorobenzene was 60% for the high dose and 30% for the low dose and the
volume applied was 0.03 mi/application. Each treated group contained 75
animals and there were 50 control animals for each sex. Growth rates In
treated and control mice were comparable through 83 weeks. Mean survival
days were significantly reduced In the 60% 1,2,4-trlchlorobenzene groups of
males and females and also 1n the 30% treatment group of females.
Hlstopathology showed some organ sites had Increased non-neoplastlc
lesions. Assuming that all 75 animals 1n the treated groups were examined
and all 50 In the control groups were examined, there would be Increases 1n
lesions In the males 1n lung, liver, kidney, adrenal, spleen and lymph node
at the high dose, and 1n| all of these organs except lymph node 1n the
females at the high dose. Unfortunately, the English translation of
Japanese text 1s not very specific 1n describing the nature of the lesion
' i
making H difficult to use this Information 1n the Interpretation of the
tumor findings.
No single tumor type was Increased significantly over the control Inci-
dence but among males nine different tumors were found 1n the high-dose
group as compared with two 1n the low-dose and two In the control group.
03760 V-18 09/25/85
-------
In females there were 11 different tumors In the high-dose group as compared
with, 3 In the low-dose and 8 In the control group. The authors do not state
whether these tumors were all found In different Individual animals or
whether these were multiple tumors 1n the same animal. Therefore, the
actual Incidence 1n terms of the number of tumor bearing animals 1s not
known.
Further Information from this study 1s necessary for full Interpreta-
tion. This single study 1s clearly Inadequate for making any conclusions
about cardnogenlclty In humans.
Reproduc11ve and Teratogen1c Tox1cVty
Studies on the reproductive or teratogenlc effects of trlchlorobenzenes
following Inhalation exposure were not found 1n the available literature.
Robinson et al. (1981} reported a multlgeneratlon study of the reproductive
effects of 1,2,4-tMchlorobenzene following oral administration. Charles
River rats were continuously exposed to the compound at 0, 25, 100 or 400
ppm 1n drinking water. The authors calculated the dosages for the FQ
generation based on water consumption data to be: for females at 29 days of
age, 8.3*.0.8, 28.0*1.2, 133.2*_13.4 mg/kg/day, respectively; for males at 29
days of age, 8.5*.0.6, 27.6+.1.6, 133.6*15.6 mg/kg/day, respectively; for
v.
females at 83 days of age, 3.7^0.1, 14.8*.!.0, 53.6*3.9 mg/kg/day, respec-
tively; for males at 83 days of age, 2.5*0.1, 8.9*0.3, 33.0+J.4 mg/kg/day,
respectively. The exposure period began with the birth of the FQ genera-
tion and continued through 32 days of age for the F? generation. Each
treatment group consisted of 17-23 Utters. No treatment-related effects
were noted with respect to fertility, neonatal weights, maternal weights,
Utter sizes, preweanlng viability or postweanlng growth 1n any generation.
03760 V-19 09/25/85
-------
Treatment-related differences were seen with respect to food Intake and
water consumption In FQ males and females, but they were Inconsistent and
did not occur In other generations. Blood chemistry analyses and locomotor
activity measurements revealed no overt hematologlc or neurologic effects,
and hlstologlc examination of the livers and kidneys of the FI genera-
tion rats revealed no damage. At the 400 ppm dose level, significantly
enlarged adrenals In both sexes of the FQ and F, rats were observed at
95 days of age (p<0.006). A follow-up acute toxlclty study showed that this
effect could result from three dally l.p. Injections of 500 mg l,2,4-tr1-
chlorobenzene/kg.
Black et al. (1983) reported In an abstract a teratogenlclty study In
pregnant Wlstar rats using 1,2,4-, 1,2,3- or 1,3,5-trlchlorobenzene adminis-
tered by gavage In doses of 75-600 mg/kg on days 6-15 of gestation (gesta-
tlonal day 0 or 1 not defined). Upon necropsy (gestatlonal day not speci-
fied), thyroid and liver lesions and reduced hemoglobin and hematocrlt
values were observed 1n treated dams (doses not specified). No teratogenlc
effects were observed In the pups; however, pups exposed to the 1,2,4- and
1,3,5- isomers (doses not specified) had mild osteogenlc changes.
KHchln and Ebron (1983) conducted a maternal hepatic toxlclty and
embryotoxiclty study where they administered 1,2,4-trlchlorobenzene (>99%
pure) dissolved 1n corn oil (2 ml/kg) orally to pregnant Sprague-Dawley
(CD strain) rats (6 or more/group) on days 9-13 of gestation and the dams
were then sacrificed on day 14 of gestation. The dosing groups were 0 (corn
*
oil only), 36, 120, 360 and 1200 mg/kg/day 1,2,4-trlchlorobenzene. All the
dams Vn the 1200 mg/kg/day group died by the third day of dosing. The 360
03760 V-20 04/05/91
-------
mg/kg/day group were observed with a maternal mortality rate of 22% and
greatly reduced body weight gains. Maternal liver weights, I1ver-to-body
weight ratios and hepatic mlcrosomal protein content were not affected by
1,2,4-trlchlorobenzene administration. 1,2,4-TMchlorobenzene was observed
to be a strong Inducer of hepatic enzymes at the 120 and 360 mg/kg/day dose
levels. Liver histology 1n the pregnant dams was unremarkable In the 36
mg/kg/day group, showed a slight degree of hepatocellular hypertrophy In 1
of 9 rats 1n the 120 mg/kg/day group and showed a moderate hepatocellular
hypertrophy 1n 7 of 8 rats 1n the 360 mg/kg/day group. The uteri from only
the 0 and 360 mg/kg/day groups were examined for 1,2,4-tr1chlorobenzene-
Induced embryonic effects. No statistically significant differences In
resorptlon, embryolethallty or abnormalities were reported, although 3/12
treated Utters showed embryolethallty as compared with 0/12 In the control
litters. Several embryonic parameters were significantly decreased by
1,2,4-trlchlorobenzene treatment. These parameters were embryonic head
length, crown-rump length, somite number and total embryo protein content
(reduced 23%).
Summary
The effects 1n mammals of acute exposure by various routes to trlchloro-
benzenes Include local Irritation, convulsions and death. Livers, kidneys,
adrenals, mucous membranes and brain ganglion cells appear to be target
organs with effects Including edema, necrosis, fatty Infiltration of livers,
Increased organ weights, porphyrln Induction and mlcrosomal enzyme Induction.
03760 V-21 09/25/85
-------
Quantitative data on the toxic effects of trlchlorobenzene following
subchronlc exposure by various routes were obtained 1n a variety of species.
In general, these studies Indicate that the liver and kidney are target
organs. Inhalation of 1,2,4-trlchlorobenzene at >74.2 mg/m3 (10 ppm) for
6 hours/day, 5 days/week for up to 26 weeks Induced hepatocytomegaly and
hyaline degeneration 1n several species (Kodba et al.,.1981; Watanabe et
al., 1978; Coate et al.t 1977), although these effects may be to some extent
reversible. One study (Watanabe et al., 1978) Identified 22.3 mg/m3 (3
ppm) as a NOAEL 1n rats. Sasmore et al. (1983) reported that some rats
exposed by Inhalation to 1,3,5-tr1chlorobenzene at 1000 mg/m3 for 13 weeks
showed squamous metaplasia and focal hyperplasla of the respiratory epithe-
lium, which appeared to be reversible. Subchronlc oral studies have also
found that the trlchlorobenzenes Induce hepatic xenoblotlc metabolism
(Carlson and Tardlff, 1976; Smith et al., 1978) and porphyrla (Carlson,
1977b). Subchronlc dermal exposure resulted In mild to moderate Irritation
i
(Powers et al., 1975; Rao et al., 1982).
One chronic study, on the effects of trlchlorobenzene painted on the
skin of mice for 2 years, reported Increased mortality 1n females at the low
i
dose (30% solution 1n acetone) and 1n both sexes at the high dose (60% solu-
i
tlon) (Yamamoto et al., 1982). While numbers of all tumor types appeared to
be Increased, no significant change was detected for any Individual tumor
type. . Thus, the carcinogenic results from the only relevant study are
considered Inconclusive.
Results of two reports on mutagenlclty tests with Salmonella typhlmurlum
test strains were negative ; (Schoeny et al., 1979; Lawlor et al., 1979).
However, this test system 1s generally Insensitive to chlorinated compounds.
03760 V-22 08/18/87
-------
A multlgeneratlon study of -ihe reproductive effects of oral exposure to tr1-
chlorobenzene (Robinson et al., 1981) failed to show effects on reproduc-
tion. Teratogenlclty studies after administration by the oral route In rats
(Black et al., 1983; KUchln and Ebron, 1963) showed mild osteogenlc changes
1n pups and significantly retarded embryonic development as measured by
growth parameters. ' !
03760 V-23 09/25/85
-------
VI. . HEALTH EFFECTS IN HUMANS
Information on the health effects of tMchlorobenzenes In humans 1s
limited to case reports. Rowe (1975) found that an Individual exposed to
1,2,4-trlchlorobenzene at 3-5 ppm had eye and respiratory Irritation.
Glrard et al. (1969) reported two cases, one 1n which a 68-year-old woman,
who often soaked her husband's work clothes 1n trlchlorobenzene, developed
aplastlc anemia, and the other In which a 60-year-old man, who had been
occupatlonally exposed to DDT as well as to mono-, dl- and trlchlorobenzenes
for over 30 years, developed anemia.
Summary
Limited data are available on human exposure to trlchlorobenzenes. No
conclusions can be drawn from this data.
03770 VI-1 09/12/88
-------
VII. MECHANISMS OF TOXICITY
- Several studies discussed 1n Chapter V on acute toxUUy have demon-
strated that the Isomers of trlchlorobenzene are capable of affecting xeno-
blotlc metabolism by Inducing a variety of the hepatic drug-metabolizing
enzymes 1n rats. These Include cytochrome c reductase, cytochrome P-450,
glucuronyltransferase, benzopyrene hydroxylase, azoreductase (Carlson and
Tardlff, 1976; Carlson, 1977a, 1978, 1981; Smith and Carlson, 1980; Denomme
et al., 1983), acetanHlde esterase and acetanlllde hydroxylase, procalne
esterase (Carlson et al., 1979), arylesterase (Carlson, 1980), mlcrosomal
proteins, phosphollplds and amlnopyrene hydroxylase (Arlyoshl et al.,
1975a,b,c). That trlchlorobenzenes enhance xenoblotlc metabolism has been
demonstrated by Smith and Carlson (1980) and Carlson (1977a), who showed
that administration of 1,2,4- or 1,3,5-trlchlorobenzene to groups of 4 male
Sprague-Dawley rats for 7 days Increased EPN detoxlcatlon. The administra-
tion of 1,2,4-trlchlorobenzene to pregnant rats was also reported to Induce
hepatic levels of cytochrome P-450, cytochrome c reductase, UDP glucuronyl-
transferase and glutathlone S-transferase (Kltchln and Ebron, 1983).
Townsend and Carlson (1981) demonstrated that 1,2,4-trlchlorobenzene,
administered by gavage In corn oil to groups of five male Swiss mice at
181.5 mg/kg (1 mmol/kg) for 7 days. Increased the L05Q and protected the
mice against the toxic effects of malathlon, malaoxon, parathlon and para-
oxon when graded doses of these Insecticides were administered on the day
following the last dose of trlchlorobenzene.
03780 VII-1 09/24/85
-------
Experiments comparing the effects of trlchlorobenzenes with the effects
of phenobarbHal and 3-methylcholanthrene Indicated that the Inductions of
mlcrosomal enzymes by trlchlorobenzenes are of the phenobarbHal type
(Carlson, 1978).
These data suggest that the trlchlorobenzenes stimulate the drug metabo-
lizing enzyme system In animals. Thus, these compounds would be expected to
Increase the rate of their own metabolism, particularly with multiple expo-
sures, resulting In Increased production of reactive Intermediates and
potentially a greater toxic response.
The series of studies by Ar1yosh1 (1975a,b,c) demonstrated that trl-
chlorobenzenes stimulated the activity of &-am1nolevul1n1c acid synthe-
tase. Since this enzyme 1s the rate-limiting step 1n heme synthesis Us
elevated activity would be expected to result In the production of elevated
levels of heme precursors. This may well account for at least part of the
Increased urinary excretion of coproporphyrln, porphoblllnogen and uropor-
phyrln 1n rats treated with trlchlorobenzenes as reported by Rlmlngton and
Zlegler (1963). These authors also reported elevated levels of these heme
precursors 1n the livers of treated rats.
There are some Indications In the report of Powers et al. (1975) that
the Irritant effects noted 1n skin may be, at least partially, related to
the defattlng action of the trlchlorobenzenes.
03780 VII-2 04/12/91
-------
Summary
The mechanism of toxldty for tMchlorobenzene Is/ not completely known.
The clinical effects of porphyrla are sometimes observed In animals and
humans exposed to trlchlorobenzene, but to a lesser extent than for
hexachlorobenzene. The capacity of trlchlorobenzene to stimulate .the
activity of 4-am1nolevul1n1c add synthetase 1s well documented. Since
this enzyme 1s the rate-limiting step In heme synthesis, there Is a direct
link to excess porphyrln production. .
03780 VII-3 04/30/91
-------
VIII. QUANTIFICATION OF TOXICOLOGIC EFFECTS
Introduction
The quantification of toxlcologlc effects of a chemical consists of
separate assessments of noncardnogenlc and carcinogenic health effects.
Chemicals that do not produce carcinogenic effects are believed to have a
threshold dose below which no adverse, noncardnogenlc health effects occur,
while carcinogens are assumed to act without a threshold.
In the quantification of noncardnogenlc effects, a Reference Dose
(RfD), [formerly termed the Acceptable Dally Intake (ADI)] 1s calculated.
" i
The RfD Is an estimate (with uncertainty spanning perhaps an order magni-
tude) of a dally exposure to the human population (Including sensitive
subgroups) that 1s likely to be without an appreciable risk of deleterious
health effects during a lifetime. The RfD Is derived from a no-observed-
adverse-effect level (NOAEL), or lowest-observed-adverse-effect level
(LOAEL), Identified from a subchronlc or chronic study, and divided by an
uncertainty factor(s) times a modifying factor. The RfD 1s calculated as
follows:
RfD . or mg/kg bw/day
[Uncertainty Factor(s) x Modifying Factor] a * 3
Selection of the uncertainty factor to be employed In the calculation of
the RfD Is based upon professional judgment, while considering the entire
data base of toxlcologlc effects for the chemical. In order to ensure that
uncertainty factors are selected and applied 1n a consistent manner, the
03790 VIII-1 04/05/91
-------
U.S. EPA (1991) employs a modification to the guidelines proposed by the
National Academy of Sciences (NAS, 1977, 1980} as follows:
Standard Uncertainty Factors (UFs)
Use a 10-fold factor when extrapolating from valid experimental
results from studies using prolonged exposure to average healthy
humans. This factor Is Intended to account for the variation
In sensitivity among the members of the human population. [10H]
Use an additional 10-fold factor when extrapolating from valid
results of long-term studies on experimental animals when
results of studies of human exposure are not available or are
Inadequate. This factor Is Intended to account for the uncer-
tainty In extrapolating animal data to the case of humans.
[10A]
* Use an additional 10-fold factor when extrapolating from less
than chronic results on experimental animals when there Is no
useful long-term human data. This factor 1s Intended to
account for the uncertainty In extrapolating from less than
chronic NOAELs to chronic NOAELs. [10S]
Use an additional 10-fold factor when deriving an RfD from a
LOAEL Instead of a NOAEL. This factor Is Intended to account
for the uncertainty In extrapolating from LOAELs to NOAELs.
[10L]
Modifying Factor (MF)
Use professional judgment to determine another uncertainty
factor (MF) that 1s greater than zero and less than or equal to
10. The magnitude of the MF depends upon the professional
assessment of scientific uncertainties of the study and data
base not explicitly treated above, e.g., the completeness of
the overall data base and the number of species tested. The
default value for the MF Is 1.
The uncertainty factor used for a specific risk assessment Is based
principally upon scientific Judgment rather than scientific fact and
accounts for possible 1ntra- and Interspedes differences. Additional
considerations not Incorporated In the NAS/ODU guidelines for selection of
an uncertainty factor Include the use of a less than lifetime study for
deriving an RfD, the significance of the adverse health effects and the
counterbalancing of beneficial effects.
03790 VI11-2 04/05/91
-------
From the RfD, a Drinking Water Equivalent Level (DUEL) can be calcu-
lated. The DUEL represents a medium specific (I.e., drinking water)
lifetime exposure at which adverse, noncarclnogenlc health effects are not
anticipated to occur. The DUEL assumes 10OX exposure from drinking water.
The DUEL provides the noncarclnogenlc health effects basis for establishing
a drinking water standard. For Ingestlon data, the DUEL Is derived as
follows:
(RfD) x (Body weight In kg) =
Drinking Mater Volume In 4/day
where:
Body weight = assumed to be 70 kg for an adult
Drinking water volume = assumed to be 2 l/day for an adult
i ' .
In addition to the RfD and the OHEL, Health Advisories (HAs) for expo-
sures of shorter duration (1-day, 10-day and longer-term) are determined.
The HA values are used as Informal guidance to municipalities and other
organizations when emergency spills or contamination situations occur. The
HAs are calculated using an equation similar to the RfD and DUEL; however,
the NOAELs or LOAELs are Identified from acute or subchronlc studies. The
HAs are derived as follows:
(NOAEL or LOAEL) x (bw)
(UF»x (_ l/day)
Using the above equation, the following drinking water HAs are developed
for noncarclnogenlc effects:
1. 1-day HA for a 10 kg child Ingesting 1 4 water per day.
2. 10-day HA for a 10 kg child Ingesting 1 4. water per day.
3. Longer-term HA for a 10 kg child Ingesting 1 a. water per day.
4. Longer-term HA for a 70 kg adult Ingesting 2 i water per day.
03790 VIII-3 08/21/87
-------
The ' 1-day HA calculated for a 10 kg child assumes a single acute
exposure to the chemical and 1s generally derived from a study of <7 days
duration. The 10-day HA assumes a limited exposure period of 1-2 weeks and
1s generally derived from a study of <30 days duration. The longer-term HA
Is derived for both the 10 kg child and a 70 kg> adult and assumes an
exposure period of ~7 years (or 10X of an Individual's lifetime). The
longer-term HA Is generally derived from a study of subchronlc duration
(exposure for 10% of animal's lifetime). .
The U.S. EPA categorizes the carcinogenic potential of a chemical, based
on the overall we1ght-of-evidence, according to the following scheme:
Group A: Human Carcinogen. Sufficient evidence exists from
epidemiology studies to support a causal association between
exposure to the chemical and human cancer.
Group B: Probable Human Carcinogen. Sufficient evidence of
carclnogenlclty 1n animals with limited (Group 81) or Inade-
quate (Group 82} evidence 1n humans.
Group C: Possible Human Carcinogen. Limited evidence of
carc1nogen1c1ty 1n animals 1n the absence of human data.
Group 0: Not Classified as to Human CardnbgenlcUy. Inade-
quate human and animal evidence of carclnogenlclty or for which
no data are available.
Group E: Evidence of Noncarclnogenldty for Humans. No
evidence of carclnogenlclty 1n at least two adequate animal
tests 1n different species or In both adequate epidemlologic
and animal studies. 7
If toxlcologlc evidence leads to the classification of the contaminant
as a known, probable or possible human carcinogen, mathematical models are
used to calculate the estimated excess cancer risk associated with the
1ngest1on of the contaminant 1n drinking water. The data used 1n these
03790 VII1-4 04/05/91
-------
estimates usually come from lifetime exposure studies using animals. In
order to predict the risk for humans from animal data, animal doses must be
converted to equivalent human doses. This conversion Includes correction
for noncontlnuous exposure, less than lifetime studies and for differences
1n size. The factor that compensates for the size difference 1s the cube
root of the ratio of the animal and human body weights. It Is assumed that
the average adult human body weight Is 70 kg and that the average water
consumption of an adult human Is 2 a of water per day.
For contaminants with a carcinogenic potential, chemical levels are
correlated with a carcinogenic risk estimate by employing a cancer potency
(unit risk) value together with the assumption for lifetime exposure from
Ingestlon of water. The cancer unit risk 1s usually derived from a linear-
ized multistage model with a 95% upper confidence limit providing a low dose
estimate; that 1s, the true risk to humans, while not Identifiable, 1s not
likely to exceed the upper limit estimate and, 1n fact, may be lower.
Excess cancer risk estimates may also be calculated using other models such
as the one-hit, Welbull, loglt and probH. There Is Uttle basis In the
current understanding of the biologic mechanisms Involved 1n cancer to
suggest that any one of these models Is able to predict risk more accurately
than any other. Because each model 1s based upon differing assumptions, the
estimates derived for each model can differ by several orders of magnitude.
The scientific data base used to calculate and support the setting of
cancer risk rate levels has an Inherent uncertainty that 1s due to the
systematic and random errors 1n scientific measurement. In most cases, only
studies using experimental animals have been performed. Thus, there 1s
03790 , VIII-5 04/05/91
-------
uncertainty when the data are extrapolated to humans. When developing
cancer risk rate levels, several other areas of uncertainty exist, such as
the Incomplete knowledge concerning the health effects of contaminants 1n
drinking water, the Impact of the experimental animal's age, sex and
species, the nature of the target organ system(s) examined and the actual
rate of exposure of the -Internal targets In experimental animals or humans.
Dose-response data usually are available only for high levels of exposure
and not for the lower levels of exposure closer to where a standard may be
set. When there Is exposure to more than one contaminant, additional
uncertainty results from a lack of Information about .possible synerglstlc or
antagonistic effects.
Noncardnoqenlc Effects
A number of biologic endpolnts have been Identified 1n short-term
studies with 1,2,4-TCB Including transient porphyMa, transient hepatic
cellular changes, and Increase 1n adrenal gland Weight and reproductive
effects (Coate et al., 1977; Koclba, 1981; KHchln and Ebron, 1983; Robinson
et al., 1981). In a reproductive study 1n rats, 25, 100 or 400 ppm of
1,2,4-tMchlorobenzene, administered to the parental animals In their
drinking water, produced no reproductive, hematologlc or neurologic effects
{Robinson et al., 1981). Increased adrenal gland weight occurred In both
the parents and offspring at the highest dose level. This change was found
to be associated with vacuollzatlon of the zona fasclculata of the adrenal
cortex and decreased serum cortlcosterone levels (dcmanec, 1991). Retarded
embryonic development was observed 1n pregnant rats receiving
1,2,4-tMchlorobenzene 360 mg/kg/day on days 9-13 of gestation (KHchln and
Ebron. 1983).
03790 VIII-6 01/03/92
-------
Hepatic porphyrla, porphyrlnurla and hepatic cellular changes have been
observed following the administration of 1,2,4-tMchlorobenzene but these
changes either occurred at very high doses or were transient. Coate et al.
{1977} reported a study 1n rats, rabbits and cynomolgus monkeys (Mactea
fasdcularls) that Involved Inhalation exposure for 26 weeks. In rats
hepatocytomegaly, hepatic vacuollzatlon and biliary hyperplasla were seen at
4 weeks and 13 weeks but not at the completion of the study. No significant
changes were seen In the rabbits.or monkeys. Carlson (1977) reported a
study 1n, rats that Investigated the potential Induction of porphyla by
hexachlorobenzene, trlchlorobenzene and dlchlorqbenzene when given by oral
gavage at 0, 50, 100 and 200 mg/kg/day. Only hexachlorobenzene showed a
marked ability to Induce porphyrla and the author determined that d1- and
trlchlorobenzene did not share this property. In the study" reported by
Carlson and Tardlff (1976}, male CD rats received 0, 10, 20 and 40 mg/kg/day
and xenoblotlc metabolism was measured as well as body weight and
hematologlc parameters. There was a dose-response related change for all
xenoblotlc enzymes but llver-to-body weight ratio was only affected at 40
mg/kg/day.
Koclba et al. (1981) reported a study In which male rats, rabbits and
dogs were exposed to 0, 30 or 100 ppm (0, 223 or 742 mg/m3) of
1,2,4-tMchlorobenzene for 44 days. No significant effects were observed
for body weight gain, hematologlc parameters, serum biochemical tests or
microscopic appearance of tissues. A reversible Increase In urinary
porphyrlns was noted but the authors Interpreted this change as being a
compound-specific physiologic effect rather than a sign of toxIcHy. In a
2-year mouse skin painting study (Yamamoto et al,, 1982} a slight Increase
03790 VII1-7 01/03/92
-------
1n tumors of all sites was reported, but no conclusions can be drawn about
cardnogenUHy because of the lack of details 1n the'English translation of
the text,
Quantification of Noncardnoqenlc Effects
Table VIII-1 presents a summary of the subchronlc and chronic toxlclty
studies on the trlchlorobenzenes that were considered for calculation of a
DWEL for each tMchlorobenzene. Table VIII-2 presents the toxlclty thresh-
old estimates that were determined from the studies discussed In Chapter V.
As Indicated by these tables and Chapter V, very little toxlclty data are
available to derive credible HAs or DHELs for the 1,2,3- and 1,3,5-trl-
chlorobenzenes Isomers. Therefore, no. HAs or DWELs are recommended for
these two tMchlorobenzene Isomers.
Derivation of 1-Day HA. The acute studies by Arlyoshl et al.
(1975a,b,c) were selected for derivation of the 1-day HA for 1,2,4-tM-
chlorobenzene.
In a series of experiments, Arlyoshl et al. (1975a,b,c) studied the
effects of the trlchlorobenzenes on Induction of hepatic mlcrosomal pro-
teins, phosphollplds and enzymes, especially In relation to the activity of
6-am1nolevul1n1c acid synthetase, the rate limiting enzyme In the blosyn-
^
thesis of heme. The three trlchlorobenzene Isomers were administered orally
to groups of 2-6 female Ulstar rats at a dose of 2SO mg/kg/day for 3 days,
after which the rats were killed and mlcrosomes were prepared. The results
Indicated that trlchlorobenzenes Increased the levels of mlcrosomal
proteins, phosphollplds and cytochrome P-450, and enhanced the activities of
03790 VII1-8 01/03/92
-------
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aniline hydroxylase, aralnopyrlne demethylase and S-am1no1evu!1n1c acid
synthetase, with the 1,2,4-lsomer being the most effective (Arlyoshl et al.,
1975a,b). The dose-response of these effects to 1,2,4-trlchlorobenzene were
determined (Arlyoshl et al., 1975c) for groups of 2-6 female Wlstar rats
treated orally with single doses of 0, 125, 250, 500. 750, 1000 and 1500
mg/kg. The results Indicated that 24 hours after the administration of the
Isomer, mlcrosomal protein was elevated at >750 mg/kg and glycogen content
was decreased at >500 mg/kg. The activities of amlnopyrlne demethylase and
aniline hydroxylase and the content of cytochrome P-450 were Increased at
>250 mg/kg, as was 5-am1nolevul1n1c add synthetase activity. A slight
significant Increase In 5-am1nolevul1n1c acid synthetase activity was
observed 1n the 125 mg/kg group with a dose-related Increase 1n activity In
the higher dose levels. The 125 mg/kg dose can be utilized as a NOAEL for
the 1-day HA calculations.
.'
The 1-day HA for a 10 kg child Is calculated using the 24 hour oral
NOAEL of 125 mg/kg reported by Arlyoshl et al. (1975c) as follows.
For a 10 kg child: : '
i A* UA (125 mq/kg/dav x 10 kal . __ . . . . . ,
1-day HA = looo x U/day mg
-------
Derivation of 10-Day HA. The Carlson and Tardlff (1976} study was
chosen for derivation of the 10-day HA for 1,2,4-trlchlorobenzene.
Carlson and Tardlff (1976) assessed the effects of a 14-day oral admin-
istration of 1,2,4-trlchlorobenzene 1n corn oil compared with corn oil
controls In male CD rats. In the 14-day studies, the effects examined were
lethality, hepatotoxldty, and the Influence on hexabarbHal sleeping time
and other parameters of xenoblotlc metabolism.* A dose of 600 mg/kg/day,
the highest dose administered, caused no deaths during the 14-day
administration period. Hepatotoxldty was evaluated by dosing at 0, 150,
300 or 600 mg/kg/day and determining serum Isocltrate dehydrogenase and
liver glucose-6-phosphatase activities. Although no dose-related changes In
serum . Isocltrate dehydrogenase activity was observed, liver
glucose-6-phosphatase activity was significantly decreased at >300 mg/kg
(p<0.05). HexabarbHal sleeping time was significantly decreased at 600
mg/kg/day (the only dose examined); this effect persisted through a 14-day
recovery period. In rats receiving 14 dally doses at 0, 10, 20 or 40 mg/kg,
there was a significant dose-related Increase 1n Hver-to-body weight ratio
*The stimulation of the xenoblotlc metabolizing system may be considered
primarily a physiologic response, although In the case of the
trlchlorobenzenes Increased metabolism of subsequent doses and the
production of reactive Intermediates and phenolic metabolites would be
expected to enhance toxldty. In addition, the elevated activity of
*-am1nolevul1n1c add synthetase, the rate limiting step In heme
synthesis, at 250 and 125 mg/kg dose levels suggests Increased porphyrln
synthesis. This Is verified at higher dose levels 1n other studies where
Increased porphyrln excretion 1n the urine has been documented.
Stimulation of porphyrln synthesis may be seriously detrimental to some
portions of the population. The use of drugs, such as barbiturates, that
enhance porphyrln synthesis are contralndlcated In patients with
Intermittent porphyrla or porphyrla varlegata (Goodman and Gllman, 1985).
Thus, 1n addition to the sparse data, the potential effects of the
stimulation of heme synthesis 1n man warrants an additional safety factor
of 10 In this calculation.
03790 VIII-13 01/03/92
-------
at >10 mg/kg/day (p<0.05). Significant dose-related Increases were also
observed 1n activities or contents of cytochrome c reductase (at >10 mg/kg),
cytochrome P-450 (at >20 mg/kg), glucuronyltransferase (at >20 mg/kg),
azoreductase (at >10 mg/kg) and the rate of detoxlcatlon of EPN (at >10
mg/kg). These results Indicated that the doses, while causing a slight
degree of hepatic .Injury, significantly enhanced xenoblotlc metabolism. The
dose of 10 mg/kg/day can be considered a NOAEL. since none of the effects
obs.erved at this dose can be directly considered adverse but rather adaptive
responses.
The 10-day HA for a 10 kg child Is calculated using the 14-day oral
NOAEL of 10 mg/kg/day reported by Carlson and Tardlff (1976) as follows.
For a 10 kg child:
10_day HA . (10 mq/kq/day x lOkq) = ]
100 x 1i/day
where:
10 mg/kg/day = NOAEL, based on the absence of adverse effects
1n rats (Carlson and Tardlff, 1976)
10 kg = assumed body weight of a child
1 a/day = assumed water consumption by a child
100 = uncertainty factor, In accordance with NAS/ODW
and Agency guidelines for use with a NOAEL from
an animal study.
This HA Is equivalent to 1 mg/day or 0.1 mg/kg/day. »
Derivation of Longer-term HA. Three studies were evaluated as the
possible basis for the derivation of longer-term HAs for a 10 kg child or a
70 kg adult. Two of the studies were oral studies (Carlson and Tardlff,
1976; Robinson et a!., 1981) and one was an Inhalation study (Kodba et al.,
1981).
03790 VIII-14 12/17/91
-------
In the 90-day study by Carlson and Tardlff (1976), the effects of oral
dosing of male CO rats (6 animals/group) at 0, 10, 20 or 40 mg/kg/day with
1,2,4-tMchlorobenzene In corn oil on weight gain, liver weight, hemoglobin
i
content, packed cell volume and the Indicators of xenoblotlc metabolism were..
evaluated. No effects on weight gain and no consistent alteration 1n hemo-
globin content or packed cell volume were observed. At 40 mg/kg, there was
a statistically significant Increase (p<0.05) In liver-to-body weight ratios
that persisted throughout a 30-day recovery period. Following 90-day admin-
istration, cytochrome c reductase activity was Increased at >10 mg/kg, with
recovery after 30 days; cytochrome P-450 levels Increased at >20 mg/kg,
followed by recovery; glucuronyltransferase activity decreased at >10 mg/kg;
EPN detoxlcatlon Increased at >20 mg/kg; benzopyrene hydroxylase activity
Increased 2-fold at 40 mg/kg; and azoreductase activity Increased at >10
mg/kg.
The Robinson study (1981} was a mult1generat1on reproductive study In
which dams received 0, 25, 100 or 400 ppm of 1,2,4-tMchlorobenzene (TC8) 1n
the drinking water. Following birth of the FQ generation. Utters of the
F- and F, generations were dosed with 0, 25, 100 or 400 ppm (0, 3.7,
14.8 or 53.6 mg/kg/day) of 1,2,4-tr1chlorobenzene for 95 days. Subsequently
these rats were bred and the f, generation received similar dosing.
»
Seventeen to 23 litters/dose group were used for the study. During the
study maternal weights, Utter size, neonatal sex, and weights were
recorded, as well as food and water Intake. Serum chemistry determinations
for glucose, BUN, creatlnlne, Na, K, Cl, uric acid, CaP, cholesterol,
trlglycerlde, blllrubln, alkaline phosphatase, ALT, AST, LDH, CPK, protein.
globulin and albumin were made. When the rats were killed, organ weights
for liver, kidney, uterus, adrenal glands, lung, heart and gonads were
\
03790 VIII-15 01/03/92
-------
recorded. The study ended when the F^ generation was 32 days old. A
significant Increase In adrenal gland weight (11% for males and 13% for
females) was noted In the FQ and F, groups. Further Investigation of
this effect found the adrenal gland Increase to be associated with moderate
vacuollzatlon of the zona fasclculata of the cortex and decreased levels of
cortlcosterone In the 53.6 mg/kg/day level of exposure In male rats
(dcmanec, 1991).
Kodba et al. (1981) reported a study 1n which male rats, rabbits and
dogs were exposed to 0, 30 or 100 ppm (0, 223 or 742 mg/m3) of
1,2,4-trlchlorobenzene for 44 days. No significant effects were observed
for body weight gain, hematologlc parameters, serum biochemical tests or
microscopic appearance of tissues. A reversible Increase 1n urinary
porphyrlns was noted but the authors Interpreted this change as being a
compound-specific physiologic effect rather than a sign of toxlclty.
The study by Carlson and Tardlff (1976) used the oral route of exposure,
which Is preferred for deriving drinking water HAs, but this study was
primarily a study of 1,2,4-trlchlorobenzene's ability to Induce xenoblotlc
metabolizing enzymes and to alter related parameters such as liver weights.
The critical adverse effect Induced by 1,2,4-trlchlorobenzene of porphyrla
related effects was not evaluated 1n this study and therefore, makes this
study Inappropriate for deriving HAs.
The longer-term HAs for a 10 kg child and a 70 kg adult are calculated
on the basis of a NOAEL of 14.8 mg/kg/day as established 1n the Robinson
study.
03790 VIII-16 12/17/91
-------
The longer-term HA for a 10 kg child 1s calculated as follows:
Longer-term HA . . x 10 kq . , 48 A
1 i/day x 100
(rounded to 1 mg/l)
where:
14.8 mg/kg/day = NOAEL, based on the absence of adverse effects
1n rats (Robinson et al., 1981}
10 kg - assumed body weight of a child
{
1 l/day = assumed water consumption by a child
100 = uncertainty factor, In accordance with NAS/ODW
and Agency guidelines for use with a NOAEL from
an animal study.
The longer-term HA for a 70 kg adult 1s calculated! as follows:
(14.8 mg/kg/davl x 70 kg
Longer-term HA = =5.18 mg/B.
2 I/day x 100 y
(rounded to 5 mg/8.)
where:
14.8 mg/kg/day = NOAEL, based on the absence of adverse effects
1n rats (Robinson et al.f 1981)
70 kg = assumed body weight of an adult
2 it/day = assumed water consumption by an adult
100 = uncertainty factor, 1n accordance with NAS/ODW
and Agency guidelines for use with a NOAEL
from an animal study.
Assessment of Lifetime Exposure and Derivation of a DWEL. As dis-
cussed In the longer-term HA section the Robinson et al. (1981) study 1s the
most appropriate to derive a lifetime DWEL. The lifetime DUEL for a 70 kg
adult 1s calculated as follows.
Step 1 - RfD Derivation
RfD ,1^.8 mq/kq/day m Oi0148 mg/kg/day (rounded to 0.01 mg/kg/day)
03790 VIII-17 01/03/92
-------
where:
14.8 mg/kg/ijay = NOAEL, based on the absence of adverse effects
_1n rats (Robinson et al., 1981)
1000 = uncertainty factor, 1n accordance with NAS/OOW
and Agency guidelines for use with a NOAEL from
a subchronlc animal study.
Step 2 - mil Derivation
0.01 mg/kg/day x 70 kg
DHEL = = 0.35 mg/l
2 l/day
(rounded to 0.4 mg/fc)
where:
0.01 rag/kg/day = RfD
70 kg = assumed body weight of an adult
2 a/day = assumed water consumption by an adult
Carcinogenic Effects ,
One study reported by Yamamato et al. (1982). where 30% or 60% solutions
of 1,2,4-trlchlorobenzene In acetone were applied to the skin of Slc.ddy
mice twice weekly for 2 years, was evaluated by the Human Health Assessment
Group (HHAG) of the U.S. EPA. The HHAG evaluation of this study determined
that Insufficient Information was presented 1n this study to allow an
i
acceptable Interpretation of the data to b'e made. Also, this single study
was found to be clearly .Inadequate for making any conclusions about
! '
cardnogenldty In humans. Therefore, the trlchlorobenzenes are classified
as U.S. EPA Group D compounds (U.S. EPA, 1991).
Existing Guidelines. Recommendations and Standards
Occupational. There are no U.S. workplace standards for the
trlchlorobenzenes.
03790 V1II-18 01/03/92
-------
The AC6IH has recommended a celling of 5 ppm (40 mg/m3) for
1,2,4-trlchlorobenzene (ACGIH, 1982), and NIOSH classified 1t as a Group Hi
pesticide. Group III pesticides are less toxic than Group II pesticides and
the recommended criteria for workplace standards are less stringent than
those recommended for Group II pesticides (NIOSH, 1978). The British
Journal of Industrial Medicine reported a provisional operational limit of
25 ppm .for 1,2,4-trlchlorobenzene (Verschueren, 1977). The 1971 TLV for
1,2,3-trlchlorobenzene 1s 1.3 ppm [10 mg/m3 (n.s.1.)] for the USSR
(Verschueren, 1977).
Trlchlorobenzenes have been designated by the ITC as TSCA Section 4(e)
priority chemicals (44 FR 70666). Preliminary Assessment Information Manu-
facturers Reports were to be submitted to the U.S. EPA Office of Toxic
Substances by November 19, 1982, for each of the trlchlorobenzenes (40 CFR
712).
The U.S. EPA determined that, on the basis of present Information, TC8
Is not classifiable as a human carcinogen; It therefore 1s placed In Class
D. This decision was verified by CRAVE 1n October 1988 (U.S. EPA, 1991).
Transportation and Regulations. The export of 1,2,3- and 1,2,4-trl-
chlorobenzene 1s regulated by DOT through the use of the Commodity Control
List (15 CFR 399).
Solid Haste Regulations. The trlchlorobenzenes are designated as
hazardous constituents of hazardous-wastes from specific sources subject to
RCRA disposal regulations (40 CFR 261.32). The hazardous waste 1n which the
03790 VIII-19 12/17/91
-------
trlchlorobenzenes are controlled as part of the hazardous constituents 1s
from the distillation or fractlonatlon column bottoms from the production of
chlorobenzene and 1s designated as EPA Hazardous Waste No. K085.
Mater. The U.S. EPA (1980), In an Ambient Water Quality Criteria
Document for Chlorinated Benzenes, determined that "Reliable toxlcologlcal
data on which to base a defensible water quality criterion do not exist for
the trlchlorobenzenes." As a result of this determination no criterion was
*' '
recommended for any trlchlorobenzene Isomer.
Special Groups at Risk
Only anecdotal Information regarding human exposure to trlchlorobenzene
1s available. These data do not Indicate special groups that might be at
risk.
Summary
Health' advisories and a DUEL for 1,2,4-trlchlorobenzene In drinking
water, based on noncarclnogenlc toxldty data, are given 1n Table VIII-3.
No HAs or DWELs are suggested for the 1,2,3- and 1,3,5-tr1chlorobenzene
Isomers because of Insufficient data being available for evaluation. The
1-day HA for 1,2,4-tMchlorobenzene of 1 mg/l for a 10 kg child 1s based
on a study by Ar1yosh1 et al. (1975c) In which female Wlstar rats were given
single oral doses of 1,2,4-tMchlorobenzene and were then evaluated. The
10-day HA for 1,2,4-trlchlorobenzene of 1 mg/l for a 10 kg child 1s based
on a study by Carlson and Tardlff {1976} 1n which male CD rats were given
1,2,4-trlchlorobenzene for 14 days and were then evaluated. The longer-term
03790 VIII-20 01/03/92
-------
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HAs for 1,2,4-trlchlorobenzene of 1 mg/s. for a 10 kg child and 5 mg/a
for a 70 kg adult are based on a study by Robinson et al. (1981) 1n which
CD-I rats were exposed by gavage to 1,2,4-trlchlorobenzene for 95
days/generation for 2 generations and evaluated for reproductive effects and
adrenal gland changes. An oral RfD of 1E-2 mg/kg/day was derived from the
Robinson study. A DWEL for 1,2,4-tr1chlorobenzene of 0.4 mg/t, for a 70 kg
adult was calculated from the same Robinson et al. (1981} study. The data
i
available on 1,2,4-trlchlorobenzene are Inadequate for making any
conclusions about Its potential cardnogenlcUy 1n humans.
03790 . VIII-22 01/03/92
-------
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03800 IX-11 01/03/92
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