United States
Environmental Protection
1=1 m m Agency
EPA/690/R-13/017F
Final
9-27-2013
Provisional Peer-Reviewed Toxicity Values for
1,2,4,5-Tetrachlorobenzene
(CASRN 95-94-3)
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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AUTHORS, CONTRIBUTORS, AND REVIEWERS
CHEMICAL MANAGERS
Alan J. Weinrich, CIH, CAE
National Center for Environmental Assessment, Cincinnati, OH
Jon Reid, PhD, DABT
National Center for Environmental Assessment, Cincinnati, OH
Harlal Choudhury, DVM, PhD, DABT
National Center for Environmental Assessment, Cincinnati, OH
DRAFT DOCUMENT PREPARED BY
ICF International
9300 Lee Highway
Fairfax, VA 22031
PRIMARY INTERNAL REVIEWERS
Audrey Galizia, DrPH
National Center for Environmental Assessment, Washington, DC
Suryanarayana V. Vulimiri, BVSc, PhD, DABT
National Center for Environmental Assessment, Washington, DC
This document was externally peer reviewed under contract to
Eastern Research Group, Inc.
110 Hartwell Avenue
Lexington, MA 02421-3136
Questions regarding the contents of this document may be directed to the U.S. EPA Office of
Research and Development's National Center for Environmental Assessment, Superfund Health
Risk Technical Support Center (513-569-7300).
l

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TABLE OF CONTENTS
COMMONLY USED ABBREVIATIONS	iii
BACKGROUND	1
DISCLAIMERS	1
QUESTIONS REGARDING PPRTVs	 1
INTRODUCTION	2
REVIEW OF POTENTIALLY RELEVANT DATA (CANCER AND NONCANCER)	4
HUMAN STUDIES	12
Oral Exposures	12
Inhalation Exposures	12
ANIMAL STUDIES	12
Oral Exposures	12
Inhalation Exposures	28
OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)	29
DERIVATION 01 PROVISIONAL VALUES	34
DERIVATION OF ORAL REFERENCE DOSES	35
DERIVATION OF SUBCHRONIC PROVISIONAL RfD (SUBCHRONIC p-RfD)	35
DERIVATION OF CHRONIC PROVISIONAL RfD (CHRONIC p-RfD)	39
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS	39
DERIVATION OF SUBCHRONIC PROVISIONAL RfC (SUBCHRONIC p-RfC)	39
DERIVATION OF CHRONIC PROVISIONAL RfC (CHRONIC p-RfC)	39
CANCER WEIGHT-OF-EVIDENCE (WOE) DESCRIPTOR	39
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES	39
DERIVATION OF PROVISIONAL ORAL SLOPE FACTOR (p-OSF)	39
DERIVATION OF PROVISIONAL INHALATION UNIT RISK (p-IUR)	40
APPENDIX A. PROVISIONAL SCREENING VALUES	41
APPENDIX B. DATA TABLES	42
APPENDIX C. BMD OUTPUTS	58
APPENDIX D. REFERENCES	61
li

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COMMONLY USED ABBREVIATIONS
BMC
benchmark concentration
BMCL
benchmark concentration lower confidence limit
BMD
benchmark dose
BMDL
benchmark dose lower confidence limit
HEC
human equivalent concentration
HED
human equivalent dose
IUR
inhalation unit risk
LOAEL
lowest-observed-adverse-effect level
LOAELadj
LOAEL adjusted to continuous exposure duration
LOAELhec
LOAEL adjusted for dosimetric differences across species to a human
NOAEL
no-ob served-adverse-effect level
NOAELadj
NOAEL adjusted to continuous exposure duration
NOAELhec
NOAEL adjusted for dosimetric differences across species to a human
NOEL
no-ob served-effect level
OSF
oral slope factor
p-IUR
provisional inhalation unit risk
POD
point of departure
p-OSF
provisional oral slope factor
p-RfC
provisional inhalation reference concentration
p-RfD
provisional oral reference dose
RfC
inhalation reference concentration
RfD
oral reference dose
UF
uncertainty factor
UFa
interspecies uncertainty factor
UFC
composite uncertainty factor
UFd
database uncertainty factor
UFh
intraspecies uncertainty factor
UFl
LOAEL-to-NOAEL uncertainty factor
UFS
subchronic-to-chronic uncertainty factor
WOE
weight of evidence
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PEER-REVIEWED PROVISIONAL TOXICITY VALUES FOR
1,2,4,5-TETRACHLOROBENZENE (CASRN 95-94-3)
BACKGROUND
A Provisional Peer-Reviewed Toxicity Value (PPRTV) is defined as a toxicity value
derived for use in the Superfund Program. PPRTVs are derived after a review of the relevant
scientific literature using established Agency guidance on human health toxicity value
derivations. All PPRTV assessments receive internal review by a standing panel of National
Center for Environment Assessment (NCEA) scientists and an independent external peer review
by three scientific experts.
The purpose of this document is to provide support for the hazard and dose-response
assessment pertaining to chronic and subchronic exposures to substances of concern, to present
the major conclusions reached in the hazard identification and derivation of the PPRTVs, and to
characterize the overall confidence in these conclusions and toxicity values. It is not intended to
be a comprehensive treatise on the chemical or toxicological nature of this substance.
The PPRTV review process provides needed toxicity values in a quick turnaround
timeframe while maintaining scientific quality. PPRTV assessments are updated approximately
on a 5-year cycle for new data or methodologies that might impact the toxicity values or
characterization of potential for adverse human health effects and are revised as appropriate. It is
important to utilize the PPRTV database flittp://hhpprtv.ornl.gov) to obtain the current
information available. When a final Integrated Risk Information System (IRIS) assessment is
made publicly available on the Internet (www.epa.gov/iris). the respective PPRTVs are removed
from the database.
DISCLAIMERS
The PPRTV document provides toxicity values and information about the adverse effects
of the chemical and the evidence on which the value is based, including the strengths and
limitations of the data. All users are advised to review the information provided in this
document to ensure that the PPRTV used is appropriate for the types of exposures and
circumstances at the site in question and the risk management decision that would be supported
by the risk assessment.
Other U.S. Environmental Protection Agency (EPA) programs or external parties who
may choose to use PPRTVs are advised that Superfund resources will not generally be used to
respond to challenges, if any, of PPRTVs used in a context outside of the Superfund program.
QUESTIONS REGARDING PPRTVs
Questions regarding the contents and appropriate use of this PPRTV assessment should
be directed to the EPA Office of Research and Development's National Center for
Environmental Assessment, Superfund Health Risk Technical Support Center (513-569-7300).
1
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INTRODUCTION
1,2,4,5-Tetrachlorobenzene (TCB), CASRN 95-94-3, is a chlorobenzene used in the
manufacture of herbicides and defoliants. 1,2,4,5-TCB is also used in insecticides,
moisture-resistant impregnates, electrical insulation, and packing material (WHO, 1991). A
table of physicochemical properties is provided below (see Table 1).
Figure 1. 1,2,4,5-TCB Structure
Table 1. Physicochemical Properties of 1,2,4,5-TCB (CASRN 95-94-3)a
Property (unit)
Value
Boiling point (°C)
244.5
Melting point (°C)
139.5
Density (g/cm3)
1.833
Vapor pressure (mmHg at 25°C)
0.0054
pH (unitless)
No data
Solubility in water (mg/L at 25°C)
0.595
Relative vapor density (air =1)
7.4
Molecular weight (g/mol)
215.89
aNLM (2011).
Table 2 provides a summary of the available toxicity values for 1,2,4,5-TCB from
U.S. EPA and other agencies/organizations.
2
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Table 2. Summary of Available Toxicity Values for 1,2,4,5-TCB (CASRN 95-94-3)a
Source/Parameter"
Value
(Applicability)
Notes
Source
Date
Accessed
Noncancer
ACGIH
NV
NA
ACGIH (2013)
NA
ATSDR
NV
NA
ATSDR (2013)
NA
Cal/EPA
NV
NA
Cal/EPA (2013a,b)b
9-26-2013
NIOSH
NV
NA
NIOSH (2010)
NA
OSHA
NV
NA
OSHA (2006, 2011)
NA
IRIS
RfD: 3 x l(T4
mg/kg-d
This RfD is based on the 90-d feeding
study performed by Chu et al. (1984a)
that identified kidney lesions in male rats
and reported a POD as a NOAEL of
0.34 mg/kg-d and a UFC of 1000
(10 each for intraspecies, interspecies,
and extrapolation from subchronic effect
level). Confidence in the value was
considered to be "low." Note that IRIS
did not apply DAF methodology.
U.S. EPA (1991)
NA
Drinking water
NV
NA
U.S. EPA (2012)
NA
HEAST
NV
NA
U.S. EPA (2011a)
NA
CARA HEEP
NV
NA
U.S. EPA (1994)
NA
WHO
TDI: 1 x l(T4
mg/kg-d
Based on the incidence of kidney lesions
reported in the study by Chu et al.
(1984a), with a NOEL of
0.034 mg/kg-day and a UF of 500.
WHO (1991)
NA
Cancer
IRIS
NV
NA
U.S. EPA (1991)
NA
HEAST
NV
NA
U.S. EPA (2011a)
NA
IARC
NV
NA
IARC (2013)
NA
NTP
NV
NA
NTP (2011)
NA
Cal/EPA
NV
NA
Cal/EPA (2009,
2013b)
NA
aSources: American Conference of Governmental Industrial Hygienists (ACGIH); Agency for Toxic Substances and
Disease Registry (ATSDR); California Environmental Protection Agency (Cal/EPA); National Institute for
Occupational Safety and Health (NIOSH); Occupational Safety and Health Administration (OSHA); Chemical
Assessments and Related Activities (CARA); Health and Environmental Effects Profile (HEEP); World Health
Organization (WHO); Integrated Risk Information System (IRIS); Health Effects Assessment Summary Tables
(HEAST); International Agency for Research on Cancer (IARC); National Toxicology Program (NTP).
bThe Cal/EPA Office of Environmental Health Hazard Assessment (OEHHA) Toxicity Criteria Database
(http://oehha.ca.gov/tcdb/index.asp) was also reviewed and found to contain no information on 1,2,4,5-TCB.
DAF = dosimetric adjustment factor; HED = human equivalent dose; NA = not applicable; NOAEL = no-observed-
adverse-effect level; NOEL = no-observed-effect level; NV = not available; POD = point of departure;
RfD = reference dose (oral); TDI = tolerable daily intake; UF = uncertainty factor; UFC = composite uncertainty
factor.
3
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Literature searches were conducted on sources published from 1900 through
September 2013 for studies relevant to the derivation of provisional toxicity values for
1,2,4,5-TCB, CASRN 95-94-3. Searches were conducted using EPA's Health and
Environmental Research Online (HERO) database of scientific literature. HERO searches the
following databases: AGRICOLA; American Chemical Society; BioOne; Cochrane Library;
DOE: Energy Information Administration, Information Bridge, and Energy Citations Database;
EBSCO: Academic Search Complete; GeoRef Preview; GPO: Government Printing Office;
Informaworld; IngentaConnect; J-STAGE: Japan Science & Technology; JSTOR: Mathematics
& Statistics and Life Sciences; NSCEP/NEPIS (U.S. EPA publications available through the
National Service Center for Environmental Publications [NSCEP] and National Environmental
Publications Internet Site [NEPIS] database); PubMed: MEDLINE and CANCERLIT databases;
SAGE; Science Direct; Scirus; Scitopia; SpringerLink; TOXNET (Toxicology Data Network):
ANEUPL, CCRIS, ChemlDplus, CIS, CRISP, DART, EMIC, EPIDEM, ETICBACK, FEDRIP,
GENE-TOX, HAPAB, HEEP, HMTC, HSDB, IRIS, ITER, LactMed, Multi-Database Search,
NIOSH, NTIS, PESTAB, PPBIB, RISKLINE, TRI; and TSCATS; Virtual Health Library; Web
of Science (searches Current Content database among others); World Health Organization; and
Worldwide Science. The following information sources outside of HERO were searched for
relevant health information: ACGM, AT SDR, Cal/EPA, U.S. EPA IRIS, U.S. EPA HEAST,
U.S. EPA HEEP, U.S. EPA OW, U.S. EPA TSCATS/TSCATS2, NIOSH, NTP, OSHA, and
RTECS.
REVIEW OF POTENTIALLY RELEVANT DATA
(CANCER AND NONCANCER)
Table 3 provides an overview of the relevant database for 1,2,4,5-TCB and includes all
potentially relevant repeated short-term-, subchronic-, and chronic-duration studies. The phrase
"statistical significance" used throughout the document indicates ap-walue of <0.05.
4
1,2,4,5-Tetrachlorobenzene

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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry"
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Human
1. Oral (mg/kg-d)a
Acute0
ND
Short-termd
ND
Long-term6
ND
Chronicf
ND
2. Inhalation (mg/m3)a
Acute0
ND
Short-termd
ND
Long-term0
Workers involved in
production of
1,2,4,5-TCB for at least
6 mo, 8 hr/d
No exposure
information
provided
Increased frequency of
chromosomal aberrations
NDr
NDr
NDr
Kiraly et al.
(1979)
PR
Chronicf
ND
Animal
1. Oral (mg/kg-d)a
Short-term
5/5, F344 Rat, diet, 14 d
0, 3.0, 10.5,
30.6, 109, 287
(males)
0, 3.2, 10.5,
29.6, 102, 271
(females)
(Adjusted)
Decreased final body weight in
males and females
(>10% decrement compared to
control); liver congestion (no
incidence or severity data
provided)
NDr
NDr
NDr
NTP (1991a)
PR
5
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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry3
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Short-term
5/5, B6C3F, Mouse, diet,
14 d
0, 6.2, 20.7,
56.1,213
(males)
0, 8.9, 25.4,
70.8, 273
(females)
Increased absolute and relative
liver weights (no raw
organ-weight data provided)
NDr
NDr
NDr
NTP (1991b)
PR
Subchronic
10/10, S-D Rat, diet,
28 d
0, 0.041, 0.42,
3.4, 32
(males)
0,0.059,0.61,
6.2,56
(females)
(Adjusted)
Increased relative liver weight
and serum cholesterol;
moderate to severe histological
changes in the liver, thyroid,
kidneys, and lungs
NI (males)
NI (females)
0.46 (males;
histological
changes in
liver)
0.041 (males;
lung and
thyroid)
0.059 (males;
thyroid)
Chu et al.
(1983)
PS
PR

15/15, S-D Rat, diet,
90 d
0.034-34
(males)
0.042-41
(females)
(Adjusted)
Increased absolute liver weight;
increased serum cholesterol;
moderate-to-severe lesions in
the liver and kidney in males
and females; increased
incidence and severity of kidney
lesions in male rats at all doses
0.34
DU
3.4
Chu et al.
(1984a)
Study
authors
report
average daily
doses as
ranges only
PS
PR
IRIS
(U.S.
EPA,
1991)
6
1,2,4,5-Tetrachlorobenzene

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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry"
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Subchronic
2/2, Unspecified strain,
Rat, diet, 30 d
0, 24, 7.0,
23.6, 78.2,
270.6 (males)
0,2.5, 8.3,
22.4, 90.3,
264.1
(females)
(Adjusted)
Gross and microscopic changes in
liver (enlarged, light in color,
centrilobular necrosis) and
kidneys (enlarged, light in color,
tubular degeneration, necrosis) in
females; enlargement, tubular
degeneration, and necrosis in
kidneys at all doses in males
NI (males)
8.3 (females)
NDr
2.4 (males)
22.4 (females)
Dow (1984a)
NPR

10/10, Unspecified strain,
Rat, diet, 42 d
26.0, 88.2,
276.0 (males)
30.4, 101.7,
315.3
(females)
(Adjusted)
Increased lung, heart, liver,
kidney, spleen, and testes weight
with increasing dose (no control
group animals sacrificed for
comparison)
NDr
NDr
NDr
Dow (1984a)
NPR

10/10, Unspecified strain,
Rat, diet, 90 d
0,2.5, or 8.2
(males)
0,2.9, or 9.7
(females)
(Adjusted)
Centrilobular necrosis in liver and
degeneration and necrosis of renal
tubular epithelium in males;
increased absolute liver weight,
centrilobular necrosis, and
swelling of hepatocytes in
females
NI (males)
NI (females)
NDr
2.5 (males)
2.9 (females)
Dow (1984a)
NPR

10/10, F344 Rat, diet,
13 wk
0,2.1,7.1,
22.1,71.4, 156
(males)
0,2.1,7.3,
22.4, 79.1, 151
(females)
(Adjusted)
Decreased body weight; increased
absolute and relative kidney and
liver weights in both sexes; renal
lesions in males; thyroid follicular
cell hypertrophy in both sexes;
decreased free and total thyroxin
concentrations in females
NI (females)
(decreased free
thyroxin)
NDr
2.1 (females)
(decreased free
thyroxin)
NTP (1991c)
Supporting
Study for
thyroid
endpoint
PR
7
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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry"
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Subchronic
10/10, B6C3FJ Mouse,
diet, 13 wk
0, 4.5, 14.6,
45.2, 150, 278
(males)
0, 6.0, 19.7,
56.6, 143, 302
(females)
(Adjusted)
Increased absolute and relative
liver weights; increased incidence
of liver lesions; increased serum
sorbitol dehydrogenase (SDH)
and alanine aminotransferase
(ALT) activity; increased platelet
count
4.5 (males)
liver weight
DU
14.6 (males)
increased liver
weight
(>10%
compared to
control)
NTP (199 Id)
PR

2/2, Beagle Dog, diet,
92 d
0.028, 0.29,
2.63 (males)
0.027, 0.27,
2.86 (females)
No evidence of any
compound-related effects
2.63 (males)
2.86 (females)
NDr
None
Dow (1982a)
Poor copy:
difficult to
read
NPR
Chronic
5/5, Unspecified strain,
Rat, diet, 101 d
0,0.01,0.03,
0.08, 0.25,
0.82 (males)
0,0.01,0.03,
0.10,0.29,
0.97 (females)
(Adjusted)
Centrilobular necrosis, swelling
of parenchymal cells of liver, and
degeneration and necrosis of
tubular epithelium of kidneys in
both sexes
0.08 (males)
0.03 (females)
NDr
0.25 (males)
0.10 (females)
Dow (1984b)
NPR

Unspecified number and
strain, Rat, Unspecified
route, 8 mo
0,0.001,
0.005, 0.05
(Adjusted)
Increased hemoglobin and
reticulocytes; disorders of
glycogen-forming function of
liver
NDr
NDr
NDr
Fomenko
(1965)
Article in
Russian, data
obtained from
IPCS (1991)
PR
8
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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry"
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Chronic
2/2 (4/4 control group),
Beagle Dog, diet, 144 d
0, 5, 10, 20
(Adjusted)
Increased liver weight in females
NDr
NDr
NDr
Dow (1982b)
Poor copy:
difficult to
read
NPR

2/2, Beagle Dog, diet,
746 d
5
(Adjusted)
Increased serum alkaline
phosphatase (ALP) activity and
bilirubin at 24 mo (compared to
historical controls); effects not
observed at 18 mo and reversed
within 3 mo of cessation
NDr
NDr
NDr
Braun et al.
(1978a,b)
Same data are
reported in
two different
publications
in the same
year
PR

2/2 Beagle Dog, diet,
144 d
0, 5, 10, 20
Slight necrosis of hepatocytes
5
NDr
10
Dow (1982b)
Poor copy:
difficult to
read
NPR
Developmental
0/10, S-D Rat, gavage,
GDs 6-15
0, 50, 100, 200
Maternal deaths at high dose; no
fetal anomalies observed
Maternal: 100
Developmental:
200
NDr
Maternal: 200
(PEL)
Developmental:
NI
Kacew et al.
(1984)
PR

0/6-8, S-D Rat, gavage,
GDs 9-13
0, 30, 100,
300, 1,000
Significantly decreased
body-weight gain in dams of
highest dose group; no changes
observed in any embryonic
endpoints examined
Maternal: 300
Developmental:
1,000
NDr
Maternal: 1,000
Developmental:
NI
Kitchin and
Ebron (1983)
NPR
9
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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry3
Critical Effects
NO A EL'
BMDL/
BMCLa
LOAEL'
Reference
(Comments)
Notesb
Developmental
0/25, F344 Rat, gavage,
GDs 6-15
0, 25, 75, 125
Reduced weight gain and food
consumption in dams; urine
stains, audible respiration, nasal
and ocular discharge in dams;
reduced ossification in fetuses
NDr
NDr
NDr
Fisher et al.
(1990a)
Abstract only
NPR
0/15; New Zealand White
Rabbit, gavage,
GDs 6-18
0, 5, 15,25
Mortality, abortions, and reduced
body-weight gain in dams; one
visceral and one cranial variation
observed in two fetuses,
respectively. FEL at lowest dose
tested (maternal mortality and
fetal loss).
NDr
NDr
NDr
Fisher et al.
(1990b)
Abstract only
NPR
Reproductive
F0: 28/28, S-D Rat, diet,
10 wk; Fl: 28/28, S-D
Rat, diet, 11 wk
0,2.2,21.1,
70.3
(F0 males)
0, 2.6, 25.5,
82.5
(F0 females)
0,2.0,21.3
(Fl males)
0,2.5, 25.4
(Fl females)
Histologic changes in kidneys of
F0 andFl males; stillborn
Fl pups and perinatal deaths
Parental: NI
(males)
Developmental:
2.6
NDr
Parental: 2.2
(males)
Developmental:
25.5
Tyl and
Neeper-
Bradley
(1989)
Also cited as
Union
Carbide
Corporation
(1992)
Bushy Run
Research
Center (1988)
NPR
10
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Table 3. Summary of Potentially Relevant Data for 1,2,4,5-TCB (CASRN 95-94-3)
Category
Number of
Male/Female, Strain,
Species, Study Type,
Study Duration
Dosimetry"
Critical Effects
NOAEL3
BMDL/
BMCLa
LOAEL3
Reference
(Comments)
Notesb
Reproductive
20/20 (40 pairs included
in the control group),
Swiss CD-I Mouse, diet,
105 d
0, 42, 109, 246
(F0 males)
0, 43, 108, 253
(F0 females)
0, 108
(F1 males)
0, 127
(F1 females)
Mortality in high-dose F0 females
(19/20); decreased number of
total live pups/litter only in litters
born to F0 but not F1 mice
Parental and
Reproductive:
42	(males)
43	(females)
NDr
Parental and
Reproductive:
109 (males)
108 (females)
NTP (1991e)
Also cited as
Chapin (1997)
PR
Carcinogenicity
ND
2. Inhalation (mg/m3)a
Subchronic
ND
Chronic
ND
Developmental
ND
Reproductive
ND
Carcinogenicity
ND
""Dosimetry: NOAEL, BMDL/BMCL, and LOAEL values are converted to an adjusted daily dose (ADD in mg/kg-d) for oral noncancer effects. All long-term exposure
values (4 wk and longer) are converted from a discontinuous to a continuous (daily) exposure. Values from animal developmental studies are not adjusted to a continuous
exposure.
bNotes: IRIS = Utilized by IRIS, date of last update; PS = principal study, PR = peer reviewed, NPR = not peer reviewed.
0 Acute = Exposure for 24 hr or less (U.S. EPA, 2002).
dShort-term = Repeated exposure for >24 hr <30 d (U.S. EPA, 2002).
"Long-term = Repeated exposure for >30 d <10% lifespan (based on 70-yr typical lifespan) (U.S. EPA, 2002).
fChronic = Repeated exposure for > 10% lifespan (U.S. EPA, 2002).
DU = data unsuitable, FEL = frank effect level, GD = gestation day, NA = not applicable, ND = no data, NDr = not determined, NI = not identified, NP = not provided,
NR = not reported, NR/Dr = not reported but determined from data, NS = not selected, NV = not available, S-D = Sprague-Dawley.
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HUMAN STUDIES
Oral Exposures
No studies were identified.
Inhalation Exposures
The effects of inhalation exposure of humans to 1,2,4,5-TCB have been evaluated in one
long-term-duration study (Kiraly et al., 1979), which was limited to considering chromosomal
aberrations in peripheral blood lymphocytes. No acute-, short-term-, or chronic-duration studies
on inhalation exposure of humans to 1,2,4,5-tetrachlorobenzene were identified in the literature.
Acute Studies
No studies were identified.
Short-Term Studies
No studies were identified.
Long-Term Study
Kiraly et al. (1979)
In a peer-reviewed occupational study, Kiraly et al. (1979) investigated chromosomal
aberrations in peripheral blood lymphocytes of factory workers involved in the production of
insecticides for at least 6 months and for 8 hours per day. The study included a control group, a
factory workers control group, and an exposure group. The normal control group consisted of
43 males and 6 females whose ages ranged from 26-52 years. The factory workers control
group consisted of engineers, technicians, and office staff working with the Budapest Chemical
Works for 10-30 years but never directly exposed to pesticides. This group included 11 males
and 3 females, whose ages ranged from 28-47 years. The exposure group consisted of 24 male
and 1 female workers, whose ages ranged from 31-59 years. Individuals in the exposure group
were involved in the production of 1,2,4,5-TCB for at least 6 months and for 8 hours per day.
The concentration of 1,2,4,5-TCB in the air of workshops was not reported by the study authors.
Blood samples were taken from each group, and lymphocytes were examined for chromosome
aberrations (see Table B. 1). The overall frequency of chromatid aberrations was higher in
workers exposed to 1,2,4,5-TCB than in either of the control groups. However, due to lack of
exposure information, identification of a NOAEL or LOAEL is precluded and the study is
unsuitable for dose-response evaluation.
Chronic Studies
No studies were identified.
ANIMAL STUDIES
Oral Exposures
The effects of oral exposure of animals to 1,2,4,5-TCB have been evaluated in two
short-term-duration studies (NTP, 1991a,b), eight sub chronic-duration studies (Chu et al., 1984a,
1983; Dow, 1984a [3 studies], 1982a; NTP 1991c,d), four chronic-duration studies (Dow, 1984b,
1982b; Braun et al., 1978a,b; Fomenko, 1965), four developmental toxicity studies (Kacew et al.,
1984; Kitchin and Ebron, 1983; Fisher et al., 1990a,b), and two reproductive toxicity studies (Tyl
and Neeper-Bradley, 1989; NTP, 1991e).
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As described in Table 3, the studies by NTP (1991) are identified as NTP (1991a) for the
14-day feeding study in rats, NTP (1991b) for the 14-day feeding study in mice, NTP (1991c) for
the 13-week feeding study in rats, NTP (199Id) for the 13-week feeding study in mice, and NTP
(1991e) for the reproductive toxicity study in mice.
Short-Term Studies
NTP (1991a)
The NTP conducted a dietary feeding study on F344 rats (5/sex/group) where animals
were administered diets containing 1,2,4,5-TCB (>99% pure) at concentrations of 0; 30; 100;
300; 1,000; or 3,000 ppm for 14 days. The control and treatment diets each contained 1% corn
oil. Based on food consumption and body-weight data, the study authors calculated average
daily doses of 0, 3.0, 10.5, 30.6, 109, and 287 mg/kg-day for males and 0, 3.2, 10.5, 29.6, 102,
and 271 mg/kg-day for females. Histopathological examinations of animals in the control group
and in the two highest dose groups (1,000 and 3,000 ppm) were conducted on the following
tissues: adrenal glands, brain, cecum, colon, duodenum, epididymis/seminal
vesicles/prostate/testes or ovaries/uterus, esophagus, eyes (if grossly abnormal), femur including
marrow, gross lesions and tissue masses with regional lymph nodes, heart, ileum, jejunum,
kidneys, liver, lungs and mainstem bronchi, mammary gland, mandibular and mesenteric lymph
nodes, nasal passage and turbinates, pancreas, parathyroid glands, pituitary gland, rectum,
salivary glands, sciatic nerve, skin, spinal cord, spleen, stomach, thymus, thyroid gland, trachea,
and urinary bladder. Livers from male rats at the 300-ppm dose level were also examined
histopathologically.
No mortality was observed in the control or treatment groups. Body weights were
significantly lower in males and females at the high dose compared to concurrent controls
(18% decrement in males, 15% decrement in females). Feed consumption for high-dose animals
was decreased by about 20%. Treatment-related clinical signs included tremors, lethargy, thin
appearance, rough hair coats, ataxia, and chromodacryorrhea (bloody tears) in both sexes of rats
in the high-dose group. Rapid breathing was observed in all females in the high-dose group. At
dietary concentrations >300 ppm (30.6 mg/kg-day in males, 29.6 mg/kg-day in females),
absolute and relative liver and kidney weights were increased; however, the study authors
provide only a qualitative narrative for this 14-day study with no numerical data. Liver
congestion was also observed in males (>109 mg/kg-day) and females (271 mg/kg-day),
although NTP (1991a) did not provide incidence or severity data. NTP (1991a) observed large
hyaline droplets in cortical tubular epithelial cytoplasm in kidneys of all treated male rats but did
not provide severity data. Immunostaining to verify the presence of alpha-2u protein was not
done. Due to deficiencies in reporting of organ weights and histopathology, identification of a
NOAEL or LOAEL is precluded.
NTP (1991b)
NTP also conducted a 14-day feeding study in B6C3Fi mice (5/sex/group) using the
same protocol as described above for F344 rats; in addition, the gallbladders of the mice were
also removed for examination at necropsy. Only qualitative summaries were provided for this
14-day study with no numerical information. The study authors calculated average daily doses
for the 30-; 100-; 300-; or 1,000-ppm groups as 6.2, 20.7, 56.1, and 213 mg/kg-day, respectively,
for males and 8.9, 25.4, 70.8, and 273 mg/kg-day for females. No animals in the high-dose
group (3,000 ppm) survived until the end of study. Because none of the animals in the
3,000-ppm group survived, the study authors were unable to calculate an average daily dose for
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this group. At moribund sacrifice or at premature death, males and females in the highest dose
group were observed to have effects typical of moribund animals including depletion and
necrosis of the lymphoid tissue in the spleen, thymus, and lymph nodes. Tremors, rapid
breathing, lethargy, hunched posture, rough hair coats, dyspnea, and prostration were observed in
males and females in the highest dose group. In the remaining treatment groups at terminal
sacrifice, final body weights in control and treated animals were comparable. Absolute and
relative liver weights were statistically significantly increased in males receiving 213 mg/kg-day
and females receiving 70.8 or 273 mg/kg-day. Due to deficiencies in reporting of organ weight
data, a NOAEL or LOAEL cannot be identified from this study.
Subchronic Studies
Chu et al. (1983)
The peer-reviewed, 28-day dietary feeding study in Sprague-Dawley rats (Chu et al.,
1983) is selected as the principal study for derivation of the subchronic provisional
reference dose (p-RfD). The 28-day study is suitable to consider as subchronic in duration. No
statement on good laboratory practice (GLP) compliance was provided. The study authors
administered diets containing 1,2,4,5-TCB (>99.5% pure) at concentrations of 0, 0.5, 5.0, 50, or
500 ppm to Sprague-Dawley rats (10/sex/dose) for 28 days. The control and treatment diets each
contained 4% corn oil. Based on body weight and food consumption data, the study authors
calculated average daily doses as 0, 0.041, 0.42, 3.4, and 32 mg/kg-day for males and 0, 0.059,
0.61, 6.2, and 56 mg/kg-day for females. Body weight and food consumption were measured
weekly, and clinical observations were made daily. At necropsy, serum biochemical parameters
(sodium, potassium, inorganic phosphate, total bilirubin, alkaline phosphatase [ALP], aspartate
aminotransferase [AST], total protein, calcium, cholesterol, glucose, uric acid, lactic
dehydrogenase [LDH], and sorbitol dehydrogenase [SDH]) were measured. The brain, heart,
liver, spleen, and kidneys were excised and weighed. The brain, pituitary, liver, adrenals,
thyroid, parathyroid, thymus, lungs, trachea, bronchi, thoracic aorta, esophagus, gastric cardia,
fundus and pylorus, duodenum, pancreas, colon, kidneys, spleen, bone marrow, mesenteric and
mediastinal lymph nodes, testes, epididymis, skeletal muscle, and heart were fixed in buffered
formalin and examined microscopically. The study authors also examined hemoglobin
concentration (Hgb), packed cell volume (PCV), red blood cell (RBC) count, total and
differential white blood cell (WBC) count, mean corpuscular volume (MCV), and mean
corpuscular hemoglobin concentration (MCHC). Liver samples were measured for microsomal
aniline hydroxylase (AH), aminopyrine demethylase (APDM), and ethoxyresorufin (ER)
deethylase activities and liver porphyrin concentrations. The study authors performed one-way
statistical analysis of variance (ANOVA), and when significant differences were indicated, the
data were subjected to the Student-Newman-Keuls post hoc multiple comparison test to identify
groups that significantly differed.
Chu et al. (1983) stated that there were no treatment-related effects in weight gain or food
consumption in rats of either sex. Liver porphyrin concentrations were not affected by treatment.
No treatment-related hematological aberrations were observed in rats of either sex at any dose.
Chu et al. (1983) reported a statistically significant increase in relative liver weights in
males and females of the highest dose group compared to controls (see Table B.2). A
statistically significant increase in serum cholesterol in both male and female rats occurred at the
highest dose (500 ppm). However, the study authors did not report data on relative liver weights
or serum cholesterol data for the intermediate dose groups (only control and high-dose animals).
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Treatment-related increases in hepatic mixed-function oxidase activity also were observed (see
Table B.3). Statistically significant increases in aniline hydroxylase (AH) were observed in
males and females in the highest dose group, and statistically significant increases in APDM
were observed in females in the highest dose group and in males at the two highest doses.
Table B.4 indicates histopathological lesions in liver, thyroid, and lung beginning at the low dose
for males, as well as liver, thyroid, and kidney beginning at the low dose for females. The study
authors reported dose-dependent morphological changes in the livers of both male and female
rats that consisted of parenchymal cytoplasmic vacuolation and anisokaryosis, and a reduction in
aggregated basophilia in the perivenous area, beginning at the lowest dose. The histological
changes were considered moderate-to-severe in the high-dose animals; however, the study
authors did not provide mean severity grades. In the thyroid, the study authors observed
increased epithelial height, angular collapse of thyroid follicles, and reduction in colloid density
at all doses. Although the study authors did not provide mean severity grades for each dose
group, changes in the thyroid were reported as mild, even within the highest dose group. In the
kidney, the study authors noted the presence of eosinophilic inclusions in the proximal
convoluted tubule of the renal cortex, which bulged more prominently into the tubular lumina
with increasing dose. The study authors considered the changes in the kidney to be statistically
significant only in males in the highest and second-highest dose groups (3.4 and 32 mg/kg-day).
Immunostaining to verify the presence of alpha-2u protein was not done. The study authors
concluded that 1,2,4,5-TCB caused hepatomegaly, hepatic microsomal enzyme induction, and
serum biochemical changes. The study authors further concluded that 1,2,4,5-TCB is a
P450-type microsomal enzyme inducer. Based on increased incidence of histological changes in
the thyroid in males, a LOAEL of 0.041 mg/kg-day (the lowest dose tested) is identified, with no
corresponding NOAEL.
Chuetal. (1984a)
Chu et al. (1984a) is the principal study identified by IRIS RfD. Chu et al. (1984) fed
groups of weanling Sprague-Dawley rats (15/sex/dose) diets containing 0, 0.5, 5.0, 50, and
500 ppm of 1,2,4,5-TCB for 13 weeks. The corresponding dose range in mg/kg-day was given
as 0.034-34. Dose-related increases in the frequency and severity of kidney lesions for male rats
were observed at 1,2,4,5-TCB doses of 5.0 ppm (0.34 mg/kg-day) and greater. The severity of
effects was considered statistically significant only at the 50- and 500-ppm doses (3.4 and
34 mg/kg-day) because of a high incidence of mild kidney lesions in the controls. Liver lesions
were observed in female rats at 500 ppm.
Dow (1984a)
Dow Chemical Company conducted subchronic and chronic toxicity studies in rats with
varying doses and durations. The subchronic study with 30, 42, and 90-day sacrifices is
designated as Dow (1984a) while the 101-day study is designated as Dow (1984b).
In a proprietary, non-peer-reviewed study, Dow (1984a) fed groups of 12 male and
12 female rats (strain not specified) diets containing 0; 30; 100; 300; 1,000; or 3,000 ppm of
1,2,4,5-TCB (99.5% purity, recrystallized), and sacrifices were conducted at 30, 42, or 90 days.
At 30 days, 2 rats/sex/dose were sacrificed to obtain preliminary histopathological data. At
42 days, all rats in the three-highest dose groups (300; 1,000; and 3,000 ppm) were necropsied;
however, no control animals were sacrificed at this timepoint. The remaining dose groups (0, 30,
and 100 ppm) were maintained on the diet for 90 days and sacrificed. Adjusted daily doses are
calculated using average body weights and average food consumption data provided by the study
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authors whenever possible; if food consumption data were not provided, doses are calculated
using allometric equations for food consumption according to provided body-weight data. For
rats administered 0; 30; 100; 300; 1,000; or 3,000 ppm of 1,2,4,5-TCB in the diet for 30 days, the
adjusted daily doses are calculated as 0, 2.4, 7.0, 23.6, 78.2, and 270.6 mg/kg-day, respectively,
for males and 0, 2.5, 8.3, 22.4, 90.3, and 264.1 mg/kg-day, respectively, for females. For rats
administered 300; 1,000; or 3,000 ppm of 1,2,4,5-TCB in the diet for 42 days, adjusted daily
doses are calculated as 26.0, 88.2, and 276.0 mg/kg-day, respectively, for males and 30.4, 101.7,
and 315.3 mg/kg-day, respectively, for females. For rats administered 0, 30, or 100 ppm of
1,2,4,5-TCB in the diet for 90 days, adjusted daily doses are calculated as 0, 2.5, and
8.2 mg/kg-day, respectively, for males and 0, 2.9, and 9.7 mg/kg-day, respectively, for females.
Animals were weighed twice weekly for the first month and once weekly in the
subsequent weeks. The lungs, heart, liver, spleen, and testes were removed and weighed after
necropsy, and portions of these organs were removed and prepared for histological examination.
Among the 2 rats/sex/dose that were sacrificed after 30 days, males exposed to the
highest dose exhibited a body weight depression and slightly decreased average food
consumption and food utilization. Male rats at the lowest dose level (30 ppm) also exhibited
kidney histopathology. An increase in the average weight of the lungs, liver, and kidneys was
noted at the three highest doses in male rats, and pathological changes in these organs were also
observed in all but the low-dose group. Male rats also had evidence of pneumonia in the lungs
and enlargement and lightening of the kidneys. The study authors also observed tubular
degeneration and necrosis of the kidneys. In female rats, no effects were noted in the two lowest
dose groups as judged by gross appearance and behavior, food consumption, mortality, final
organ and body weights, and gross and microscopic examination of tissues. Females in the
highest dose group displayed a retardation of growth and decreased average food consumption
and food utilization. Increased average weight of lungs, liver, and kidneys were observed in
females of the two highest dose groups. Gross and microscopic changes in lungs, liver, and
kidneys of female rats in the three highest dose groups were similar to those observed in male
rats. Based on kidney effects in the male rat kidney, a LOAEL of 2.4 mg/kg-day (the lowest
dose tested) is identified for the 30-day study, with no corresponding NOAEL.
After the 30-day sacrifice, Dow (1984a) sacrificed all rats remaining in the three highest
dose groups on Day 42. No control rats were sacrificed at this timepoint, and no
histopathological examinations were conducted. The study authors only reported average organ
weights and did not provide analysis of variance for the organ-weight values. The study authors
noted that the average organ weights (lungs, heart, liver, kidneys, spleen, testes) increased with
increasing dose. No additional data from the 42-day sacrifice were reported. Due to lack of
control animals sacrificed at this timepoint, identification of a NOAEL or LOAEL is precluded
for the 42-day segment of this study.
Dow (1984a) sacrificed the remaining animals in the 0-, 30-, and 100-ppm exposure
groups (adjusted daily doses of 0, 2.5, and 8.2 mg/kg-day for males and 0, 2.9, and
9.7 mg/kg-day for females) after 90 days. Male and female rats both showed gross and
microscopic changes in the liver and kidneys at all doses tested (incidence and severity not
reported). In males fed 8.2 mg/kg-day, livers were enlarged and light in color. In all females in
the three lowest dose groups, centrilobular necrosis and slight generalized cloudy swelling of the
remaining parenchymal cells were observed. Statistically significantly increased average relative
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liver weights (g/100 g body weight) of female rats in the highest dose group also were reported
(see Table B.5). Degeneration and necrosis of renal tubular epithelium also were observed in all
treated males and females. Based on gross and microscopic effects seen in liver and kidney of
males, a 90-day LOAEL of 2.5 mg/kg-day (the lowest dose tested) is identified, with no
corresponding NOAEL.
NTP (1991c)
In a peer-reviewed, 13-week oral toxicity study, NTP (1991c) administered diets
containing 1,2,4,5-TCB (98% pure) at concentrations of 0; 30; 100; 300; 1,000; or 2,000 ppm of
to F344/N rats (20/sex/dose). The control and treatment diets each contained 1% corn oil. The
study was performed in compliance with GLP standards. The study authors calculated
corresponding doses of 0, 2.1, 7.1, 22.1, 71.4, and 156 mg/kg-day for males and 0, 2.1, 7.3, 22.4,
79.1, and 151 mg/kg-day for females. Ten rats per sex per dose group were designated for
urinalysis, serum chemistry, hematologic, and thyroid function analysis. The remaining
10 animals per sex per dose group were examined for histopathology, organ-weight
determinations, and sperm morphology or vaginal cytology studies. Rats were observed twice
daily, and body weights were recorded once weekly. Serial blood samples were collected on
Days 3 or 4, 15, or 16, and 43 or 44 and analyzed for SDH, alanine aminotransferase (ALT),
creatinine, creatine phosphokinase (CPK), y-glutamyl transpeptidase (GGT), and albumin.
Platelet counts were also determined. Sixteen-hour urine samples were collected on Days 17 or
18, 45, or 46, and 88 or 89. Appearance, 16-hour volume, specific gravity, glucose and protein
concentrations, ALP and AST activity, and porphyrin concentrations were determined. Animals
were necropsied at study termination. The liver, right kidney, right testis, brain, heart, thymus,
lungs, and seminal vesicles were weighed.
Hematologic analyses included RBC, total and differential WBC counts, Hgb, Hct MCV,
MCH, MCHC, and blood morphology. NTP (1991c) used Jonckheere's test to evaluate the
statistical significance of dose-response trends for organ-weight, hematologic, serum chemical,
and male reproductive system data. If Jonckheere's test showed significance, Shirley's
nonparametric multiple comparison procedure was used to assess the significance of pairwise
comparisons between dosed and control groups. Otherwise, Dunn's test was used for pairwise
comparisons.
All animals survived to the end of the study. The mean body weights of rats of both
sexes in the two highest dose groups were lower than those of controls throughout most of the
study; final mean body weights of male rats dosed with 71.4 and 156 mg/kg-day were 10% and
21% lower, respectively, compared to controls. In females, final mean body weights at the 79.1
and 151 mg/kg-day doses were 8% and 16% lower, respectively, compared to controls (see
Table B.6). Food consumption in all treated groups was similar to controls. NTP (1991c)
reported that compound-related clinical signs included hypoactivity and lethargy. Absolute
kidney weights were increased in both sexes at 300 ppm (22.1 mg/kg-day for males or
22.4 mg/kg-day for females), and absolute liver weights were increased at 300 ppm
(22.1 mg/kg-day) for males and 100 ppm (7.3 mg/kg-day) for females (see Table B.7). Hct,
Hgb, and RBC counts were significantly lower than those of controls for males receiving
>71.4 mg/kg-day, while platelet counts and serum albumin concentration were significantly
increased. Female rats exposed to the two highest doses had significantly lower MCV and
significantly increased serum albumin concentrations. Statistically significantly decreased free
and total thyroxin concentrations were observed at exposures of 300 ppm (22.1 mg/kg-day) in
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males and at 30 ppm (2.1 mg/kg-day) in females (see Table B.8). The study authors reported
that triiodothyronine (T3) concentrations were not affected, and thyrotropin concentrations were
not recorded for each exposed animals. The study authors reported significant changes in urine
parameters for both male and female rats. Statistically significant decreases in right whole and
cauda epididymal weights and sperm motility were reported in males in the 22.1 and
156 mg/kg-day dose groups (the 71.4 mg/kg-day dose group was not examined). Estrous cycle
length was unaffected by treatment. Compound-related lesions were observed in the kidneys of
male and female rats but were more prominent in males. Cortical renal tubular cytoplasmic
alterations occurred in male rats in all dose groups and were characterized histologically as
intracytoplasmic aggregates of large, eosinophilic, angular inclusions that were increased in
number and size compared to controls. Based on the reported histologic findings, the study
authors assigned a NOEL of 30 ppm (2.1 mg/kg-day) for males and females. However, based on
statistically significantly decreased free serum thyroxin in females, this dose (2.1 mg/kg-day) is
considered a 13-week LOAEL.
NTP (199Id)
In addition to the studies in rats, NTP (1991d) also conducted a 13-week, peer-reviewed
study in mice. B6C3Fi mice (10/sex/dose) were provided diets containing 0; 30; 100; 300;
1,000; or 2,000 ppm of 1,2,4,5-TCB (98% pure). The control and treatment diets each contained
1% corn oil. This study was performed in compliance with GLP standards. Based on food
consumption and body-weight data, the study authors calculated corresponding average daily
doses of 0, 4.5, 14.6, 45.2, 150, and 278 mg/kg-day for males and 0, 6.0, 19.7, 56.6, 143, and
302 mg/kg-day for females. Ten mice per sex per dose were designated for serum chemistry,
hematologic, and thyroid function analysis and urinalysis. The remaining 10 animals per sex per
dose group were evaluated for histopathological changes, organ-weight determinations, and
sperm morphology or vaginal cytology studies. Mice were observed twice daily, and body
weights were recorded once weekly. Serial blood samples were collected on Days 3 or 4, 17, or
18, and 45 or 46 and analyzed for SDH, ALT, creatinine, CPK, GGT, and albumin. Sixteen-hour
urine samples were collected on Days 17 or 18, 45 or 46, and 88 or 89. Mouse appearance,
16-hour urine volume, specific gravity, glucose and protein concentrations, ALP, and AST
activity, and porphyrin concentrations were determined. Animals were necropsied at study
termination. The liver, right kidney, right testis, brain, heart, thymus, lungs, and seminal vesicles
were weighed.
Hematologic analyses included RBC, total and differential WBC counts, Hgb, Hct, MCV,
MCH, MCHC, and blood morphology. NTP (1991d) used Jonckheere's test to evaluate the
significance of dose-response trends for organ weight, hematologic, serum chemical, and male
reproductive system data. If this test showed significance, then Shirley's test (nonparametric
multiple comparison procedure) was used to assess the significance of pairwise comparisons
between dosed and control groups. Otherwise, Dunn's test was used for pairwise comparisons.
Two of the 10 female mice in the highest dose group were sacrificed in a moribund
condition before the end of the study. Mice of both sexes in the 1,000 and 2,000 ppm dose
groups lost weight during Week 1 of the study. Mean body weights of males from all dose
groups and females in the highest dose group were notably lower than those of the controls;
however, data tables in the NTP (1991d) report did not list which dose groups were statistically
significantly different from the control group (see Table B.9).
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Mice of both sexes in the two highest dose groups had statistically significantly increased
platelet counts. NTP (199Id) also noted statistically significantly lower values for Hgb, MCH,
Hct, and MCV at the high-dose groups. Male and female mice in the high-dose group also had
significantly higher values for serum ALT activity and serum albumin concentration, with serum
SDH activity for males and females increased at the two highest doses. The length of the estrous
cycle was significantly increased in females from the highest dose group compared to controls;
however, estrous cyclicity was not investigated at other doses. The study authors reported that
no treatment-related effects were seen on male reproductive organ weights or on sperm
evaluations.
Males exposed to 14.6 mg/kg-day exhibited biologically (>10%) and statistically
significant increases in absolute and relative liver weights compared to controls (see Table B. 10).
While females had a statistically significant increase in absolute liver weight at the lowest dose
tested (4.5 mg/kg-day), this increase did not exceed 10% until the 45.2 mg/kg-day dose and there
was no dose-response. Compound-related lesions were present in the liver of exposed animals of
each sex (see Table B.l 1). NTP (1991d) reported compound-related clinical signs that included
tremors in females and prostration, lethargy, hunched position, and rough hair coats in males and
females at the two highest dose. Based on increased relative liver weight in males
(>10%) compared to controls), a NOAEL of 4.5 mg/kg-day and a LOAEL of 14.6 mg/kg-day are
identified.
Dow (1982a)
In a subchronic oral toxicity study, Dow (1982a) administered 1,2,4,5-TCB (>99% pure)
to beagle dogs (2/sex/group) in diet at concentrations of 0, 0.0001, 0.001, or 0.01% for 92 days.
The study authors calculated the following equivalent average daily doses based on body weight
and food consumption: 0.028, 0.29, and 2.63 mg/kg-day for male dogs and 0.027, 0.27, and
2.86 mg/kg-day for females. The available copy of this document is of poor quality and largely
illegible. The study authors examined the general appearance and the behavior of the animals at
unspecified intervals. Animals were weighed weekly, and food consumption was measured
throughout treatment. Hematological parameters (PCV, Hgb, RBC, total and differential WBC)
and clinical chemistry parameters (blood urea nitrogen [BUN], ALP, AST, ALT, and
bromosulfophthalein retention) were measured before study initiation (baseline) and at Days 8,
15, 23, 57, and 77. At necropsy, the following organs were excised, weighed, and processed for
histopathological evaluation: lungs, heart, liver, kidneys, spleen, testes, and brain. In addition,
the following organs were examined histopathologically: thyroid, adrenals, lymph node,
pancreas, aorta, skeletal muscle, prostate, spinal cord, peripheral nerve, pituitary, thymus, gall
bladder, trachea, esophagus, stomach, colon, cecum, small intestine, urinary bladder, uterus, and
ovary.
Dow (1982a) observed no dose-related changes in food consumption, clinical signs, body
weight, hematologic or clinical chemistry parameters, organ weights, or pathological lesions in
either sex. A NOAEL of 2.63 mg/kg-day is identified based on the lack of observed effects in
male dogs, with no corresponding LOAEL.
Dow (1982b)
Dow (1982b) also conducted a 144-day dietary feeding study in beagle dogs. The
available copy of this report is largely illegible, and any illegible information is noted as such.
The study authors administered 1,2,4,5-TCB (99.2% pure) in diet at doses of 0, 5, 10, and
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20 mg/kg-day to male and female beagle dogs (2/sex/dose) for 144 days. The control and
treatment diets each contained 1.0% peanut oil. The study authors stated that the target
concentrations were verified using an unspecified analysis. Male and female dogs were housed
two per cage with animals of the same sex and dose group housed together. Food and water was
provided ad libitum. Dogs were sacrificed at the conclusion of the study.
Dow (1982b) recorded body weight and food consumption weekly. Hematological
parameters (PCV, Hgb, RBC, total and differential WBC) were measured before study initiation
(baseline) and on Days 33, 81, and 137. The total concentration of 1,2,4,5-TCB in the blood was
measured in the high-dose group only. Urinalysis parameters (specific gravity, pH, sugar,
albumin, WBC, RBC, epithelial cells, casts, crystals, bacteria, mucus) were recorded before
study initiation and following the 144-day exposure period. Clinical chemistry parameters were
measured, including BUN, SGOT, SGPT, AP, and BSP retention. Urinary concentrations of
coproporphyria uroporphyrin, and creatinine were measured after 116 days of treatment.
Dow (1982b) reported no statistically significant effects on body-weight gain, food
consumption, hematology, BUN, AST, and bromsulphalein retention. The study authors
reported ALP was elevated (statistical significance not reported) at the high dose and for one dog
of each sex at the mid dose. The study authors also reported elevated ALT in one dog in the
high-dose group. Liver weight was statistically increased in both male and female dogs at the
high-dose group and female dogs at the mid-dose group. An increased number of inflammatory
cells in the hepatic sinusoids and slight necrosis of hepatocytes were observed in females at the
high-dose group. One female in each of the high- and mid-dose group experienced minimal
cytoplasmic swelling of hepatocytes. Data tables of elevated parameters are illegible and are not
reported. Although the small number of animals per group makes identification of a NOAEL or
LOAEL somewhat uncertain, a 144-day NOAEL of 5 mg/kg-day and a LOAEL of 10 mg/kg-day
based on liver effects in female dogs are considered.
Dow (1984b)
In addition to the studies summarized previously in the Subchronic Studies section, Dow
(1984b) also performed another subchronic feeding study in rats. Male and female rats
(5/sex/dose; strain not specified) were administered diets containing 0, 0.1, 0.3, 1, 3, or 10 ppm
of 1,2,4,5-TCB (>99.5% pure) in ground Purina Laboratory Chow for 101 days. The adjusted
daily doses are calculated from study data as 0, 0.01, 0.03, 0.08, 0.25, or 0.82 mg/kg-day for
males and 0, 0.01, 0.03, 0.10, 0.29, or 0.97 mg/kg-day for females. Animals were weighed twice
weekly for the first month and once weekly thereafter. Gross clinical observations for
appearance and behavior were made at unspecified intervals. The lungs, heart, liver, spleen, and
testes were removed and weighed after necropsy, and portions were removed and prepared for
histological examination.
Male rats showed no evidence of treatment-related effects in gross appearance, behavior,
growth, food consumption, mortality, final average organ and body weights, or gross
examination of the tissues at any dose tested. Upon microscopic examination, male rats
exhibited liver central lobular necrosis and renal tubular epithelial degeneration and necrosis at
0.25 mg/kg-day. Beginning at 0.10 mg/kg-day, Dow (1984b) reported centrilobular necrosis and
slight generalized swelling of the hepatocytes and kidneys with degeneration and necrosis of the
renal tubular epithelium among female rats. The study authors did not report severity and
incidence of the liver and kidney lesions, and no further results were reported. Based on the
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observed liver central lobular necrosis and renal tubular epithelial degeneration and necrosis in
female rats, a LOAEL of 0.10 mg/kg-day is identified, with a corresponding NOAEL of
0.03 mg/kg-day.
Chronic Studies
Fomenko (1965)
In an article published in Russian, the study authors administered 1,2,4,5-TCB by gavage
to albino rats at doses of 0, 0.001, 0.005, or 0.05 mg/kg-day for 8 months. Data from the
publication were obtained from a secondary source (IPCS, 1991), and the reported
treatment-related effects included increased content of sulfhydryl groups in serum, increased
hemoglobin and reticulocytes (>0.005 mg/kg-day), and disorders of the glycogen-forming
function of the liver. The study report was also reviewed by IRIS (U.S. EPA, 1991) and judged
unsuitable due to insufficient reporting of data. Thus, identification of a NOAEL or LOAEL is
precluded.
Braun et al. (19 78a, b)
Braun and colleagues (1978a,b) published the same information on the pharmacokinetic
evaluation of 1,2,4,5,-TCB in dogs in two different journal articles in 1978. The study authors
administered 1,2,4,5-TCB in diet to beagle dogs (2/sex) at a dose of 5 mg/kg-day for 2 years
followed by a 20-month observation period. No controls were reported in the study. The study
authors reported slightly increased serum ALP and bilirubin concentrations (compared to
historical controls) at 24 months. No other clinical data were reported. Due to the lack of
concurrent controls, identification of the single 5 mg/kg-day dose as a NOAEL or LOAEL is
precluded.
Developmental Studies
Kacew et al. (1984)
Kacew et al. (1984) conducted a peer-reviewed gavage study to examine the
developmental effects of 1,2,4,5-TCB. Pregnant female Sprague-Dawley rats (10/dose) were
administered 0, 50, 100, or 200 mg/kg-day 1,2,4,5-TCB (99.5% pure, recrystallized from
95% ethanol) in corn oil vehicle via gavage on Gestational Days (GDs) 6-15. Food and water
were provided ad libitum. Animals were weighed and sacrificed on GD 21.
Kacew et al. (1984) removed and weighed all fetuses, then reweighed the whole body,
liver, brain, kidney, perirenal fat, spleen, and heart of the dams. The study authors measured the
following hematological endpoints in dams: Hgb, Hct, RBC, total and differential WBC, MCV,
MCHC, and MCH. The study authors also measured the following clinical chemistry endpoints:
sodium, potassium, inorganic phosphorus, total bilirubin, ALP, AST, total protein, calcium,
cholesterol, glucose, uric acid, and LDH. Aniline hydroxylase (AH) activity was also measured.
Residue analysis for 1,2,4,5-TCB was conducted on the maternal kidney, brain, spleen, heart,
liver, and perirenal fat as well as one fetus from each treatment group and the brain and liver
from another fetus within each treatment group. All fetuses were observed for gross birth
defects, but only live fetuses were counted and examined for skeletal and visceral examination.
The study authors completed histopathology on the heart, brain, pituitary, eye, thyroid,
parathyroid, trachea, bronchi, lung, thymus, stomach, small and large intestine, pancreas, liver,
kidney, spleen, adrenal, skeletal muscle, peripheral nerve, skin, bone marrow, ovary, uterus, and
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bladder in the dams. The study authors determined statistical significance by one-way ANOVA.
Duncan's Multiple Range Test was conducted on all endpoints that showed significant results
from the ANOVA test.
Kacew et al. (1984) reported that 9/10 dams in the high-dose (200 mg/kg) group only
survived for an average of 6.5 days after the start of exposure. The study authors reported the
cause of death to be circulatory collapse, and these animals showed signs of severe alimentary
toxemia with uterine vascular hemorrhages. The study authors reported no statistically
significant effects on the absolute or relative weight of the brain, heart, kidney, liver, or spleen of
the dams from the other dose groups. The hematological parameters tested were deemed to be in
the normal range for pregnant rats. No statistically significant changes in leukocyte differential
counts were observed, but the study authors noted an increase in leukocyte counts with
increasing dose. Serum cholesterol and hepatic supernate were statistically significantly
increased in dams of the mid- and high-dose groups. Hepatic alkaline phosphatase (AP) activity
was statistically significantly increased in the low-dose group but not in the mid- or high-dose
group. The total number of fetuses per dam was significantly decreased in the low-dose group
but not in the mid- or high-dose group (see Table B.12). The study authors could not provide an
explanation for this effect because tissue residue analysis indicated higher levels of test material
in the mid- and high-dose groups compared to the low-dose group. Based on mortality in dams,
a maternal frank effect level (FEL) of 200 mg/kg-day is identified. A maternal NOAEL of
50 mg/kg-day and a LOAEL of 100 mg/kg-day are identified based on increased serum
cholesterol and hepatic AH activity in rats.
Kitchin and Ebron (1983)
Kitchin and Ebron conducted a peer-reviewed gavage study to examine the maternal
reproductive and developmental effects of 1,2,4,5-TCB. 1,2,4,5-TCB (>98% pure) was ground
to a fine power via mortar and pestle, suspended in 1.5% gum tragacanth, and administered via
gavage in a volume of 2 mL/kg. Timed-pregnant female Sprague-Dawley rats were administered
0; 30; 100; 300; or 1,000 mg/kg-day 1,2,4,5-TCB on GDs 9-13, where GD 1 is established by
the day that sperm were detected in the vaginal smear. The number of animals per dose group
was not specifically reported but ranged between 6-8 rats per group. Food and water were
provided ad libitum. All animals were sacrificed on GD 14.
Kitchin and Ebron (1983) weighed the livers of all dams immediately after sacrifice, and
sections were processed for histopathology. In an unreported number of animals, the study
authors removed the uterus and examined the fetuses for "growth and differentiation
parameters"; however, the study authors did not delineate the exact parameters examined. Fetal
abnormalities included differences in the presence of a beating heart, somite number, and fetal
size compared to controls. Tabulated data indicate that fetal death, abnormalities, head length,
crown-rump length, somites, and protein content were examined. The study authors assayed
maternal rat liver for cytochrome P450, NADPH-cytochrome c-reductase, aminopyrine
A'-demethylase, and ethoxyresorufin O-deethylase. The study authors used an ANOVA test to
determine the statistical significance of treatment compared to control. Additional tests
conducted by the study authors included the William's test for dose-related effects, and the
Fisher's Exact test for enumerative data.
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Kitchin and Ebron (1983) reported no statistically significant treatment-related effects on
maternal mortality, absolute or relative liver weight, or hepatic microsomal protein content.
Maternal body-weight gain, reported as the body weight on Day 14 minus the body weight at
Day 8, was statistically significantly decreased in the high-dose group only. The study authors
reported no significant liver histology effects except the incidence of slight centrilobular
hypertrophy in the high-dose group. The study authors reported significantly increased
cytochrome P450 in the high-dose group. The study authors did not observe any differences in
NADPH-cytochrome c-reductase between control and treatment animals but did find
significantly increased O-deethylation of ethoxyresorufin compared to control at all doses and
increased aminopyrine in the two highest dose groups (see Table B. 13). The study authors
reported that 1,2,4,5-TCB exposure did not significantly alter resorptions, fetal deaths,
abnormalities, protein, somite number, crown-to-rump length, or head length compared to
control. A statistically significant decrease in implantations in the high-dose group was observed
(data for all other dose groups were not reported). Based on significantly decreased body-weight
gain, a maternal LOAEL of 1,000 mg/kg-day and a corresponding NOAEL of 300 mg/kg-day are
identified. Based on the lack of any observed developmental effects, a developmental NOAEL
of 1,000 mg/kg-day (the highest dose tested) is identified.
Fisher et al. (1990a)
In a report available only as an abstract, Fisher et al. (1990) investigated the maternal and
developmental effects of 1,2,4,5-TCB administered to rats and rabbits. The results in rats are
denoted as Fisher et al. (1990a), while the results in rabbits are denoted as Fisher et al. (1990b).
Pregnant F344 rats (25/dose) were administered 1,2,4,5-TCB (purity not reported) by gavage at
doses of 0, 25, 75, and 125 mg/kg-day on GDs 6-15, and dams were sacrificed on GD 21. The
study authors reported maternal toxicity at the high dose (125 mg/kg-day) including reduced
body-weight gain, reduced food consumption, and clinical signs of toxicity (urine stains, audible
respiration, and ocular and nasal discharge). In the fetuses, reduced ossification was observed in
all treatment groups, but the study authors noted that ossification was minimal at 25 mg/kg-day.
A maternal LOAEL of 125 mg/kg-day based on reduced body-weight gain, reduced food
consumption, and clinical signs of toxicity and a corresponding NOAEL of 75 mg/kg-day are
identified. A developmental LOAEL of 25 mg/kg-day is identified based on slightly reduced
ossification with no developmental NOAEL.
Fisher et al. (1990b)
Pregnant New Zealand White rabbits (15/dose) were administered 1,2,4,5-TCB (purity
not reported) by gavage at doses of 0, 5, 15, and 25 mg/kg-day on GDs 6-18. Dams were
sacrificed on GD 29. The study authors reported maternal toxicity at all doses including
mortality at 5 and 25 mg/kg-day, fetal loss at 5 mg/kg-day, and transient body-weight gain
reductions at 5 and 15 mg/kg-day. The study authors reported fetotoxicity (increased incidence
of one visceral and one skeletal variation in the cranial region) at the two lowest doses (5 and
15 mg/kg-day) but not at the high dose. Based on the limited reported data, 5 mg/kg-day is
identified as a FEL for maternal mortality and fetal loss.
Reproductive Studies
Tyl and Neeper-Bradley (1989)
In an unpublished, non-peer-reviewed, two-generation reproductive toxicity study, Tyl
and Neeper-Bradley (1989) administered 1,2,4,5-TCB (-97.6% pure) to male and female
F0 Sprague-Dawley rats (28/sex/dose) in diet at concentrations of 0; 30; 300; or 1,000 ppm for a
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10-week period prior to mating. The control and treatment diets each contained 1% corn oil.
Based on food consumption and body-weight data, the study authors calculated corresponding
average daily doses of 2.2, 21.1, and 70.3 mg/kg-day for F0 males and 2.6, 25.5, and 82.5 for
F0 females. Males and females within each dose group were randomly paired 1:1 for 21 days for
mating. A satellite group of 10 females per concentration were also administered control and
treatment diet for 10 weeks. Males that did not successfully mate within the first week of pairing
were mated with satellite females for 1 week. Parental F0 males were necropsied following the
satellite mating period. F0 females were administered the control or 1,2,4,5-TCB diet prior to
mating and throughout mating, gestation, parturition, and lactation. F0 mated females were
weighed on GDs 0, 7, 13, and 20, and females with litters were weighed on PND 0, 4, 7, 14, and
21. F1 weanlings (28/sex/group) were randomly selected to produce the F2 generation, with
intra-litter matings avoided whenever possible. Remaining F1 weanlings were necropsied and
examined grossly. The F1 parental animals (28/sex/dose) were fed the 1,2,4,5-TCB diet (0, 30,
or 300 ppm) for 11 weeks prior to mating. All F1 weanlings from the 1,000-ppm group died;
therefore, no F2 generation was bred for this treatment group. Mating and fertility indices were
calculated for F0 and F1 males and females. For F1 and F2 litters, the following indices were
calculated: gestational index, live birth index, 4-day survival index, 7-day survival index, 14-day
survival index, 21-day survival index, and lactation index.
Tyl and Neeper-Bradley (1989) conducted histopathological analysis of the following
tissues from parental F0 and F1 control and high-dose animals: pituitary, liver, kidneys, vagina,
uterus, ovaries, testes, epididymides, seminal vesicles, prostate, and other tissues with gross
lesions. Kidneys from all F0 and F1 parental males were examined for the presence of hyaline
droplets by staining with Mallory-Heidenhain stain. Immunostaining to verify the presence of
alpha-2u protein was not done. Satellite females were examined for number of uterine
implantation sites but did not undergo further histopathological examination. Statistical analyses
were performed with the litter as the unit of comparison. Continuous variables were compared
among control and treatment groups using Levene's test for equal variance, ANOVA, and Mests.
If variance was homogenous and ANOVA was significant, a pooled Mest was used for pairwise
comparison. If variance was heterogeneous by Levene's test, all groups were compared by
ANOVA for unequal variance followed by a separate variance Mest for pairwise comparison
when necessary. Bonferroni's correction was used to correct for multiple comparisons.
Nonparametric data were evaluated by the Kruskal-Wallis test, followed by the Mann-Whitney
U test. Incidence data were compared with Fisher's exact test.
In the F0 generation, body weights in males and females in the high-dose group were
significantly reduced compared to controls during most of the 10-week period prior to mating.
Food consumption in F0 males and females in the high-dose group was also significantly
reduced for the entire period prior to mating. Tyl and Neeper-Bradley (1989) also observed
transient reductions in body-weight gain and food consumption at various intervals. No clinical
signs of toxicity were observed in F0 males; however, F0 females exhibited hypoactivity, ataxia,
emaciation, dehydration, unkempt appearance, urine stains, and labored breathing during the
period prior to mating.
During the F0 generation mating period, no treatment-related effects on reproductive
parameters (gestational length, percentage of pregnancies, percentage of males-siring litters,
mating index, fertility index) were observed. In the low- and high-dose groups, the total number
of pups born per litter and number of live pups born per litter were statistically significantly
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reduced (see Table B. 14). All pups in the high-dose group died by Postnatal Day (PND) 14.
Litter sizes in the low-dose group were reduced through PND 4, and litter size in the mid-dose
group was reduced on PND 14 and 21. Pup body weights were significantly reduced in the
mid-dose group on PNDs 7, 14, and 21 and in the high-dose group on PND 0 and 4. Tyl and
Neeper-Bradley (1989) observed no treatment-related findings during gross necropsy of F1 pups
not selected as parental or satellite breeding animals for the F2 generation.
Necropsy of the F0 male parental animals revealed increased liver size, increased kidney
size, and color change in the pancreatic lymph nodes at the high dose, and diffuse color change
in kidneys at the mid and high doses. In F0 parental females in the high-dose group, color
change of the jejunum was observed. Treatment-related findings in the liver included
eosinophilic cytoplasmic inclusions (males) and vacuolation (females) in the high-dose groups;
hepatocellular hypertrophy was also observed in the mid- and high-dose groups of both sexes. In
kidneys of F0 males, the study authors observed increased incidences of hyaline droplet
nephrosis (severity scored using the Mallory-Heidenhain stain) in all dose groups, and tubular
proteinosis, granular cast formation in tubules, interstitial nephritis, and interstitial fibrosis at the
mid and high doses. In the kidneys of F0 females, only proteinosis was observed in the
high-dose group. Final body weight of F0 males at the high dose was significantly decreased
(-15% compared to control) while body weights of females remained unaffected by treatment.
Increased absolute organ weights (>10% compared to control values) were observed in male
livers and kidneys at the mid and high dose and in female livers at the high dose (see
Table B. 14). Tyl and Neeper-Bradley (1989) reported that females in the high-dose group
experienced increased absolute brain weight; however, values reported in the study data tables
indicated a decrease at the high-dose. Increased organ weights relative to body weight were also
observed in kidneys of all treated male animals; livers and testes in males at the mid and high
dose; brains in males at the high dose; livers in females at the mid and high dose; and kidneys in
females at the high dose.
Because all pups in the F1 high-dose group died by PND 14, only two groups were bred
to produce the F2 generation. The parents for the F2 generation were treated for up to 11 weeks
during a prebreed period followed by the same treatment protocol for the F1 generation. Based
on body weight and food consumption data, Tyl and Neeper-Bradley (1989) calculated average
daily doses for 0, 30, and 300 ppm as 0, 2.0, and 21.3 for F1 males and 0, 2.5, and 25.4 for
F1 females. No treatment-related clinical signs or effects on reproductive parameters were
observed for the F1 parental generation. Gestational body weights in F1 parental females were
comparable to control values. No reduction in litter size was observed in any F2 litters; however,
F2 pup body weights were reduced on PND 7, 14, and 21 in the 300-ppm (25.5-mg/kg-day)
group. Perinatal deaths (PND 0-4) and deaths at PND 14 were also increased in this dose group.
No treatment-related findings were observed during gross necropsy of F2 pups.
Necropsy of the F1 parental generation demonstrated gross and microscopic changes in
the kidney and liver similar to the F0 parental generation. Increased absolute liver weight and
liver weight relative to body weight was observed in males at the high dose (21.3 mg/kg-day).
Positive staining for alpha-2u protein in kidneys was also observed in males at the high dose
(21.3 mg/kg-day). In females, Tyl and Neeper-Bradley (1989) reported reduced brain weights
and increased relative liver weight at the high dose (25.4 mg/kg-day).
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Based on kidney effects in F1 males, a parental LOAEL of 2.0 mg/kg-day is identified,
with no corresponding NOAEL. A reproductive LOAEL of 25.5 mg/kg-day and NOAEL of
2.6 mg/kg-day are identified based on reduced survival of F1 offspring.
NTP (199le)
NTP (1991e) published a GLP-compliant reproductive toxicity study that exposed male
and female CD-I mice to 1,2,4,5-TCB (>99% pure) in feed (suspended in corn oil). This study
was completed using the tasks described in the Reproductive Assessment by Continuous
Breeding Protocol (RACB) as follows: Task 1: a 14-day dose-setting study with 5 doses and a
control group (8 animals per sex per group); Task 2: a continuous breeding phase with a control
group (40 breeding pairs) and 3 dose groups (20 breeding pairs per dose group); Task 3: a
1-week crossover mating trial using 3 groups of 20 pairs conducted if Task 2 is positive for
reproductive effects and after the Task 2 litter was weaned; and Task 4: an offspring assessment
(conducted if Task 2 is negative for reproductive effects). Under Task 2, the F0 generation of
mice (20 per sex per group) was administered 280; 720; and 1,800 ppm 1,2,4,5-TCB in the diet
(mixed in corn oil). A control group consisting of 40 males and 40 females received feed
containing 1% corn oil. Adjusted daily doses under Task 2, as reported by the study authors,
were 42, 109, and 246 mg/kg-day for the F0 males and 43, 108, and 253 mg/kg-day for the
F0 females. The adjusted daily doses under Task 4, as reported by NTP (1991e), were 0 and
108 mg/kg-day for F1 males and 0 and 127 mg/kg-day for F1 females. Food and water were
provided ad libitum. F0 animals were exposed to 1,2,4,5-TCB for 1 week prior to mating,
14 weeks of cohabitation, and 3 weeks after cohabitation (18 weeks total). The study authors
measured body weight and food consumption weekly. Fertility, litters per breeding pair, number
and proportion of live pups per litter, sex ratio of live pups, and mean male and female pup body
weights per litter were measured throughout the study. The study authors did not report details
on the sacrifice or necropsy of the F0 generation after the delivery of the pups. The study
authors reported that 19 of the 20 high-dose F0 females died or were humanely sacrificed
(18 animals died during parturition). The study authors feared that the high-dose males would
not survive until the scheduled necropsy and sacrificed the males sooner than planned. At
Week 11 of the study, an additional 33 male CD-I mice (140-150 days old) were purchased
from Charles River Laboratories (Portage, MI) and served as a substitute necropsy group to
match the unscheduled dosing group sacrifice. The original control animals were maintained
through the end of the study.
The last litters born from Task 2 were used for Task 4. The animals in Task 4 were dosed
at the same doses as the F0 generation after weaning. At approximately 74 days (±10 days),
animals were housed 2 per cage. Once the mice reached sexual maturity, 20 animals per sex per
group were cohabitated for 7 days. NTP (1991e) checked for a vaginal copulatory plug and all
other endpoints listed in Task 2. At necropsy, the following endpoints were measured: organ
weights, body weights, epididymal sperm motility, sperm count and morphology, and estrual
cyclicity (measured by vaginal lavage for 12 days before sacrifice).
NTP (1991e) used the Cochran-Armitage test on all data presented as a proportion.
Under Task 2, Shirley's Test was used to compare the mean values of dose groups and the
control. In cases where a trend was detected, Jonckheere's test was used. All other data were
analyzed with Dunn's Test. Under Task 4, Wilcox on's test was used to evaluate each dose group
compared to control.
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NTP (1991e) reported that 19/20 F0 females in the high-dose group died before Week 12
of the study period. Under Task 2, the study authors reported a significantly decreased number
of live pups per litter in the 720-ppm group (see Table B. 15). Also in the 720-ppm group, the
number of total live pups was significantly decreased in Litters 1, 2, and 4, the number of live
male pups and proportion of males was significantly decreased in Litters 1 and 2; and the
adjusted weight of total and live and female pups was significantly decreased in Litter 5. In the
280-ppm group, the male-to-female sex ratio was significantly decreased in Litter 1. No other
adverse reproductive endpoints were reported. The body weights of F0 females were within
10% of control values. Food consumption was significantly decreased in Weeks 1 and 2 for both
males and females in the high-dose group. The study authors reported significantly increased
body weight, liver, right cauda, and seminal vesicle weight in the 1,800 ppm group in F0 males
(see Table B. 16). Relative liver weight was two times the control value in 1,800-ppm males.
Abnormal sperm was also significantly higher in males of this high-dose group. During the
holding period between Task 2 and Task 4, live pup weight was significantly decreased in males
and females at PND 21 in the 720-ppm group.
Historically, the Task 4 protocol includes control and high-dose group animals only, yet
due to the high mortality in high-dose females, results considered under Task 4 in NTP (1991e)
were modified to include the control and mid-dose group. Individual male and female food
consumption and body weight were not significantly decreased. However, combined male and
female food consumption was significantly decreased in the mid-dose group compared to
control. NTP (1991e) reported no treatment-related effects on reproductive parameters.
However, body weight and relative liver and kidney/adrenal weight were significantly increased
in males and females in the mid-dose group (see Tables B.17 and B.18). Additionally, relative
right testis weight was significantly increased in males in the mid-dose group. The study authors
reported no significant clinical signs of toxicity. The study authors reported cystic ovaries in five
females, dilation of the uterus in two females, and nodules on the liver in one female in the
mid-dose group. The study authors reported the presence of cytomegaly and karyomegaly of
hepatocytes in males and females in the mid-dose group, with severity ranging from mild to
moderate and slightly more severe effects in females compared to males. The study authors
reported no significant lesions in the testis or epididymis of male mice (see Tables B. 19 and
B.20).
NTP (1991e) concluded that the unexpected mortality in the high dose females under
Task 2 of the study may be due to effects of 1,2,4,5-TCB and the stress of parturition. The study
authors noted the discrepancy between the decreased live pups under Task 2 and the absence of
the same effect under Task 4. Overall, the study authors concluded that 1,2,4,5-TCB caused
mild reproductive toxicity along with parental toxicity evidenced by significantly increased
relative liver and kidney/adrenal weights in both male and female mice at the mid-dose group.
Based on increased organ weights and decreased number of live pups, a LOAEL for parental and
reproductive toxicity, respectively, is identified as 108 mg/kg-day in females with a
corresponding NOAEL of 43 mg/kg-day.
Carcinogenicity Studies
No oral carcinogenicity studies were identified and none of the available short-term-,
subchronic-, or chronic-duration studies reported tumors in the animals tested (see Table 3).
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Other Studies
No studies were identified.
Inhalation Exposures
No studies were identified.
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OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)
Table 4A and Table 4B summarize genotoxicity studies and other studies conducted with 1,2,4,5-TCB.
Table 4A. Summary of 1,2,4,5-TCB Genotoxicity Studies
Endpoint
Test System
Dose Concentration"
Resultsb
Comments
References
Without
Activation
With
Activation
Genotoxicity studies in prokaryotic organisms
Reverse mutation
Salmonella typhimurium strains TA98, TA100,
TA1535, and TA1537 with or without
S9 activation
0; 10; 33; 100; 333;
1,000; or
1,333 ng/plate


NA
Haworth et al.
(1983)
SOS repair induction
ND
Genotoxicity studies in nonmammalian eukaryotic organisms
Mutation
ND
Recombination
induction
ND
Chromosomal
aberration
ND
Chromosomal
malsegregation
ND
Mitotic arrest
ND
Genotoxicity studies in mammalian cells—in vitro
Mutation
ND
Chromosomal
aberrations
Chinese Hamster Ovary cells with or without
S9 metabolic activation
Highest dose tested:
150 ng/mL
-
-
Precipitate observed
at 150 ng/mL
Loveday et al.
(1990)
Sister chromatid
exchange (SCE)
Chinese Hamster Ovary cells with or without
S9 metabolic activation
Highest dose tested:
76.5 ng/mL
-
-
Precipitate observed
at 76 iig/mL
Loveday et al.
(1990)
DNA damage
ND
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Table 4A. Summary of 1,2,4,5-TCB Genotoxicity Studies
Endpoint
Test System
Dose Concentration"
Resultsb
Comments
References
Without
Activation
With
Activation
DNA adducts
ND
Genotoxicity studies in mammals—in vivo
Chromosomal
aberrations and DNA
damage
5/5, SPF Han (Bor:NMRI) mouse, single i.p.
injection, micronuclei of femoral marrow
examined 16, 24, or 48 hr following administration
5,000 mg/kg

NA
No indications of a
clastogenic effect
were observed
Bayer (1993)
8/0, B6C3Fi mouse, single i.p. injection, bone
marrow cells harvested at 17 or 36 hr following
administration and examined for chromosomal
aberrations
NV

NA
NA
Shelby and
Witt (1995)
Sister chromatid
exchange (SCE)
ND
DNA damage
ND
DNA adducts
ND
Mouse biochemical or
visible specific locus
test
ND
Dominant lethal
ND
Genotoxicity studies in subcellular systems
DNA binding
ND
aLowest effective dose for positive results, highest dose tested for negative results.
b+ = positive, ± = equivocal or weakly positive, - = negative, NA = not applicable, NV = not available, ND = no data.
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Table 4B. Other Studies
Test
Materials and Methods
Results
Conclusions
References
Metabolism/
toxicokinetic
S-D rat (5 males); single gavage;
[14C]-labeled 1,2,4,5-TCB (0.4 jiCi/mg)
Radioactivity detected in urine and feces
with most detected in urine; 8% of dose
excreted in 48 hr and continued at steady
rate until 7 d when 21% of dose
excreted; identified
2,3,5,6-tetrachlorophenol as main
metabolite.
1,2,4,5-TCB is minimally
metabolized (21% detected
in excreta after 7 d), with
most excretion occurring
in urine.
Chuetal. (1984b)
Metabolism/
toxicokinetic
Beagle dog (2/sex); diet; 5 mg/kg-d for 2 yr
followed by 20-mo recovery phase
Increased serum ALP and bilirubin
(compared to historical control data) at
end of 2-yr treatment; test material had
more affinity to fat than plasma.
Study authors concluded
that changes in clinical
chemistry were reversible,
and compound
administration resulted in
slight impairment of liver
function. The fat-to-
plasma ratio of test
material increased rapidly
after cessation of
treatment.
Braunetal. (1978a,b)
Metabolism/
toxicokinetic
Squirrel monkey (4 males); single gavage
twice/wkfor 3 wk; [14C]-labeled
1,2,4,5-TCB, 50 mg/kg (0.027 nCi/mg)
No metabolites identified and
>99% radioactivity detected was
unchanged parent compound; main route
of excretion through feces where 18% of
administered dose excreted at 48 hr
postdose; <0.1% excreted in urine at
48 hr.
Study authors concluded
that the major route of
excretion in monkeys is
through feces, and only
18% of the administered
dose was detected at 48 hr
postdosing.
Schwartz et al. (1987)
Mode of action/
mechanistic
F344 rat (18 males/treated group, 12 males in
control group); medium-term liver focus
bioassay initiated with single i.p. injection of
200 mg/kg diethylnitrosamine (DEN)
followed by daily gavage of 0.1 or
0.4 mmol/kg-d for 6 wk; partial hepatectomy
3 wk after initiation with DEN; measured
induction of glutathione-S-transferase
Significant increase in number and area
of GST-P positive foci in liver following
DEN initiation plus administration of
test material by gavage.
1,2,4,5-TCB promoted
preneoplastic foci in liver
of rats initiated with DEN.
Gustafson et al. (1998)
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Table 4B. Other Studies
Test
Materials and Methods
Results
Conclusions
References

placental form (GST-P) foci



Mode of action/
mechanistic
F344 rat (18 males/treated group, 12 males in
control group); medium-term liver focus
bioassay initiated with single i.p. injection of
200 mg/kg diethylnitrosamine (DEN)
followed by daily gavage of 0.1 or
0.4 mmol/kg-d for 6 wk; partial hepatectomy
3 wk after initiation with DEN; evaluated
liver weights, histopathology, reduced and
oxidized glutathione levels (GSH, GSSG),
CYP450 induction, and nonfocal GSTP1-1
and c-fos induction
Increased final liver weights,
hepatocellular centrilobular hypertrophy,
karyomegaly, anisocytosis;
50% decrease in GSSG, no change in
GSH compared to control; induced
CYP1A2, CYP2B1/2, and CYP2E1; no
induction of nonfocal GSTP1-1;
induction of c-fos.
The study provides data on
the molecular and cellular
changes that inform
mechanisms of
hepatocarcinogenic
potential of 1,2,4,5-TCB
following an initiating
dose of DEN and partial
hepatectomy.
Gustafson et al. (2000)
Mode of action/
mechanistic
Male F344 rats; initiation with DEN
(200 mg/kg i.p.); daily gavage beginning
2 wk following initiation of 0.1 mol/kg
1,2,4,5-TCB for 6 wk; partial hepatectomy;
evaluated liver weight, normal hepatocyte
division rates, and the number and volume of
GST-P positive foci at 23, 26, 28, 47, and
56 d after initiation with DEN (200 mg/kg
i-P)
Induction of GST-P foci; no increase in
hepatocyte division rates.
The study provides data on
the molecular and cellular
changes that inform
mechanisms of
hepatocarcinogenic
potential of 1,2,4,5-TCB
following an initiating
dose of DEN and partial
hepatectomy.
Ou et al. (2003)
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Metabolism/Toxicokinetic Studies
Metabolism studies in Sprague-Dawley rats, beagle dogs, and squirrel monkeys indicate
that 1,2,4,5-TCB is not extensively metabolized (Chu et al., 1984b, Braun et al., 1978a,b;
Schwartz et al., 1987), with no more than 21% of the administered dose was subsequently
recovered in excreta up to 7 days postdosing in rats. In squirrel monkeys, >99% of the parent
compound was excreted, and no metabolites were detected (Schwartz et al., 1987). Chu et al.
(1984b) identified 2,3,5,6-tetrachlorophenol as a main metabolite excreted in urine of rats.
Further study details are presented in Table 4B.
Mode-of-Action/Mechanistic Studies
Several medium-term bioassays focused on the liver have been conducted with
1,2,4,5-TCB in rats administered an initiating dose of diethylnitrosamine (200 mg/kg i.p.) and
evaluated for the presence of GST-P foci in liver after partial hepatectomy. Results indicate that
1,2,4,5-TCB induced GST-P positive foci in rat liver. However, the available data do not
provide a definitive conclusion on a mode-of-action for 1,2,4,5-TCB. Study-specific data are
provided in Table 4B.
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DERIVATION OF PROVISIONAL VALUES
Tables 5 and 6 present a summary of noncancer and cancer reference values, respectively. IRIS data also are indicated in the table.
Table 5. Summary of Noncancer Reference Values for 1,2,4,5-TCB (CASRN 95-94-3)
Toxicity Type (units)
Species/Sex
Critical Effect
p-Reference
Value
POD
Method
POD
UFC
Principal Study
Subchronic p-RfD (mg/kg-d)
Rat/M and F
Thyroid histopathology
3 x 1(T5
LO AEL| Hi,
0.0098
300
Chuetal. (1983)
Chronic RfD (mg/kg-d)
IRIS (U.S. EPA, 1991)
Rat/M
Kidney lesions
3 x 1(T4
NOAEL
0.34
(Note: IRIS did not
apply DAF
methodology)
1,000
Chu et al. (1984a)
Subchronic p-RfC (mg/m3)
NDr
Chronic p-RfC (mg/m3)
NDr
NDr = not determined.
Table 6. Summary of Cancer Values for 1,2,4,5-TCB (CASRN 95-94-3)
Toxicity Type
Species/Sex
Tumor Type
Cancer Value
Principal Study
p-OSF
NDr
p-IUR
NDr
NDr = not determined.
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DERIVATION OF ORAL REFERENCE DOSES
Derivation of Subchronic Provisional RfD (Subchronic p-RfD)
The toxicity database for effects induced by 1,2,4,5-TCB following oral exposure is
robust and includes effects observed in rats, mice, dogs, and rabbits (tabulated in Table 7 and
provided graphically in Figure 2). Potential targets of 1,2,4,5-TCB oral toxicity include the
thyroid, liver, and kidney. Body weight depression, mortality, and developmental and
reproductive effects were also observed.
Table 7. Response Array Information
Citation
Species
Study Type
Sex
Critical Effect
Dow (1982a)
Dog
Subchronic
Male and Female
No observed effects
Fisher etal. (1990a)
Rat
Developmental
Male and Female
Delayed ossification
Chu et al. (1984a) (IRIS
principal study)
Rat
Subchronic
Male
Kidney pathology
Dow (1984a)
Rat
Subchronic (30 d)
Male
Kidney pathology
Dow (1984b)
Rat
Subchronic
Female
Kidney pathology
Tyl and Neeper-Bradley
(1989)
Rat
Reproductive
Male
Kidney pathology
Dow (1982b)
Dog
Subchronic
Female
Liver pathology
NTP (199 Id)
Mouse
Subchronic
Male
Increased liver weight
Kacew et al. (1984)
Rat
Developmental
Female (dams)
Increased serum
cholesterol, hepatic
aniline hydroxylase
(AH)
Chu etal. (1983)
Rat
Subchronic
Male
Liver pathology
Kitchin and Ebron (1983)
Rat
Reproductive
Female (dams)
Decreased body weight
NTP (1991e)
Mouse
Reproductive
Female
Reduced live pups
Chu et al. (1983)
(principal study for
subchronic p-RfD)
Rat
Subchronic
Male
Thyroid pathology
NTP (1991c)
Rat
Subchronic
Female
Decreased free serum
thyroxin
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1,000
100
10
fr
73
6) .
=£ 1
c>
£
0.1
0.01
• Test Doses
ANOAEL
~ BMDL
~LOAEL
-C
O !±.
Devel.
Kidney
Liver
Repro.
Thyroid
Figure 2. 1,2,4,5-TCB Exposure-Response Array
Several oral studies are candidates for derivation of the subchronic p-RfD. The
Chu et al. (1983) study is selected as the principal study for the derivation of the subchronic
p-RfD The most sensitive effect following 1,2,4,5-TCB exposure evident in the database was
thyroid toxicity in male rats (Chu et al. 1983), with a LOAEL at the lowest tested dose of
0.041 mg/kg-day, and it is selected as the critical effect. This observed thyroid toxicity consisted
of histopathological changes noted as moderate-to-severe at the high dose, and increased
epithelial height, angular collapse of thyroid follicles, and reduction in colloid density at all
doses. Female rats also exhibited thyroid histopathology at 0.59 mg/kg-day. The NTP (1991c)
study observed a statistically significant decrease in free serum thyroxin in female rats at the
lowest dose tested (2.1 mg/kg-day) supporting that thyroid toxicity could be occurring at lower
doses in that study (see Table B.8). Although other studies at higher doses and longer durations
(chronic) did not report information on thyroid histopathology or biochemistry, there was no
information to the contrary.
Kidney toxicity was also observed in several studies at doses as low as 0.1 mg/kg-day
(DOW, 1984a). Kidney histopathology was also observed in male rats in the principal study
(Chu et al., 1983) at doses >3.4 mg/kg-day. The study authors suggested that the kidney
histopathology could be related to alpha-2u nephropathy, but immunostaining to verify the
presence of alpha-2u protein was not done. A very thorough reproductive study (Tyl and
Neeper-Bradley, 1989) identified kidney effects in rats but at a dose (2 mg/kg-day) considerably
higher than the observed thyroid effects. The IRIS chronic RfD was based on kidney lesions at
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0.34 mg/kg-day in the male rat (Chu et al., 1984a). However, all the kidney effects were
observed at doses greater than the selected critical effect (thyroid histopathology). Additionally,
Chu et al. (1983) qualitatively observed lung lesions occurring at 0.041 mg/kg-day in male rats
but did not elaborate on this finding. No other studies in the database reported lung lesions, so
this effect was not considered significant in context.
The dose-response data on thyroid histopathology for male rats in the Chu et al. (1983)
study could not be successfully modeled by BMDS, thus, a NOAEL/LOAEL approach was
employed to identify a potential point of departure (POD). Histopathological changes in the
liver (males) observed in the Chu et al. (1983) study were also modeled with BMDS
(Appendix C) but provided a BMDL (0.456 mg/kg-day) over 10-fold higher than the LOAEL for
thyroid effects. Therefore, the LOAEL of 0.041 mg/kg-day based on thyroid histopathology in
male rats (Chu et al., 1983) is chosen as the POD to derive a subchronic p-RfD for 1,2,4,5-TCB.
EPA endorses body-weight scaling to the % power (BW/4) to extrapolate toxicologically
equivalent doses of orally administered agents from all laboratory animals to humans for the
purpose of deriving an RfD under certain exposure conditions. The use of BW/4 scaling for
deriving an RfD is recommended when the observed effects are associated with the parent
compound or a stable metabolite but not for portal-of-entry or developmental endpoints.
Following U.S. EPA (201 lb) guidance, the POD for thyroid histopathology in adult rats
is converted to an HED through application of a DAF as follows:
DAF	=	(BWa' '- BWh'1)
Where:
DAF	=	dosimetric adjustment factor
BWa	=	animals body weight
BWh	=	human body weight
Using a BWa of 0.25 kg for rats and a BWh of 70 kg for humans (U.S. EPA, 1988)
identified for the critical effect yields a PODhed as follows:
PODhed = POD (mg/kg-day) x DAF
= 0.041 mg/kg-day x 0.24
= 0.0098 mg/kg-day
Subchronic p-RfD = LOAELhed UFC
= 0.0098 mg/kg-day 300
= 3 x 10~5 mg/kg-day
The composite uncertainty factor (UFc) of 300 is described in Table 8.
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Table 8. Uncertainty Factors for Subchronic p-RfD of 1,2,4,5-TCB
UF
Value
Justification
ufa
3
A UFa of 3 (10°5) has been applied to account for uncertainty in characterizing the
toxicodynamic differences between rats and humans following oral 1,2,4,5-TCB exposure.
The toxicokinetic uncertainty has been accounted for by calculation of a human equivalent
dose (HED) through application of a dosimetric adjustment factor (D AF) as outlined in the
EPA's Recommended Use of Body Weight3/4 as the Default Method in Derivation of the Oral
Reference Dose (U.S. EPA, 2011b).
ufd
1
A UFd of 1 has been applied because the database includes one acceptable two-generation
reproductive toxicity study rats (Tyl and Neeper-Bradley, 1989) and two acceptable
developmental toxicity studies in rats (Kitchin and Ebron, 1983; Kacew et al., 1984) via the
oral route.
UFh
10
A UFh of 10 has been applied for inter-individual variability to account for human-to-human
variability in susceptibility in the absence of quantitative information to assess the
toxicokinetics and toxicodynamics of 1,2,4,5-TCB in humans.
ufl
10
A UFl of 10 has been applied for LOAEL-to-NOAEL extrapolation because the POD is a
LOAEL.
UFS
1
A UFS of 1 has been applied because a subchronic-duration study was selected as the
principal study.
UFC
300
Composite uncertainty factor.
NA = not applicable.
The confidence of the subchronic p-RfD for 1,2,4,5-TCB is low as explained in Table 9
below.
Table 9. Confidence Descriptors for Subchronic p-RfD for 1,2,4,5-TCB
Confidence Categories
Designation"
Discussion
Confidence in principal
study
M
Although compliance with GLP standards was not stated by study
authors, the study is presented in a peer-reviewed journal and
otherwise meets the standards of study design and performance,
with numbers of animals, examination of potential toxicity
endpoints and presentation of information.
Confidence in database
M
The database includes acceptable reproductive and developmental
toxicity studies and chronic-duration studies. However, the
chronic-duration studies in rodents and dogs are not comprehensive
and of high quality. The database also encompasses other studies
which did not report thyroid effects, indicating some inconsistency
in the overall toxicity profile.
Confidence in subchronic
p-RfDb
M
The overall confidence in the subchronic p-RfD is medium
aL = low, M = medium, H = high.
bThe overall confidence cannot be greater than lowest entry in table.
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Derivation of Chronic Provisional RfD (Chronic p-RfD)
A chronic RfD of 3 x 10 4 mg/kg-day is available on IRIS based on the subchronic,
90-day feeding study by Chu et al. (1984a) that identified an increased incidence of kidney
lesions in male rats. At the time of the IRIS assessment, a DAF was not applied to the POD used
for derivation of the RfD. Additionally, subsequent to the IRIS file, additional studies have
become available, and these studies have been summarized herein. The IRIS database should be
checked to determine when changes are made. No chronic p-RfD is developed in this document.
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS
Derivation of Subchronic Provisional RfC (Subchronic p-RfC)
No adequate inhalation studies in humans or animals are identified for the derivation of a
provisional reference concentration. Therefore, derivation of a subchronic p-RfC is precluded.
Derivation of Chronic Provisional RfC (Chronic p-RfC)
No adequate inhalation studies in humans or animals are identified for the derivation of a
provisional reference concentration. Therefore, derivation of a chronic p-RfC is precluded.
CANCER WEIGHT-OF-EVIDENCE (WOE) DESCRIPTOR
Table 10 identifies the cancer WOE descriptor for 1,2,4,5-TCB.
Table 10. Cancer WOE Descriptor for 1,2,4,5-TCB
Possible WOE Descriptor
Designation
Route of entry
(oral, inhalation,
or both)
Comments
"Carcinogenic to Humans "
NS
NA
NA
"Likely to Be Carcinogenic
to Humans "
NS
NA
NA
"Suggestive Evidence of
Carcinogenic Potential"
NS
NA
NA
"Inadequate Information
to Assess Carcinogenic
Potential"
Selected
Both
No studies on the carcinogenic potential of
1,2,4,5-TCB in animals or humans via the oral
or inhalation route are available in the
literature.
"Not Likely to Be
Carcinogenic to Humans"
NS
NA
NA
NS = not selected, NA = not applicable.
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES
Derivation of Provisional Oral Slope Factor (p-OSF)
There are insufficient data to assess the carcinogenic potential of 1,2,4,5-TCB via the oral
route; therefore, derivation of a p-OSF is precluded.
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Derivation of Provisional Inhalation Unit Risk (p-IUR)
There are insufficient data to assess the carcinogenic potential of 1,2,4,5-TCB via the
inhalation route; therefore, derivation of a p-IUR is precluded.
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APPENDIX A. PROVISIONAL SCREENING VALUES
No provisional screening values are provided for 1,2,4,5-TCB.
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APPENDIX B. DATA TABLES
Table B.l. Chromosome Aberrations in Peripheral Blood Lymphocytes of Workers
Exposed to l,2,4,5-TCBa
Groups
Normal Control
Factory Employees
Control
1,2,4,5-TCB
No.
%
No.
%
No.
%
Frequency of Chromatid-Type Chromosome Aberrations
Mitoses examined
2,523
838
1,360
Gap
73
2.89
46
5.48
81
5.95
Isogap
19
0.75
2
0.23
30
2.20
Break
40
1.59
26
3.10
55
4.04
Isobreak
17
0.67
18
2.14
32
2.35
Exchange
-
-
-
-
2
0.15
Total
149
5.90
92
10.97
198
14.70
Frequency of Labile Chromosome-Type Aberrations
Mitoses examined
2,523
838
1,360
Acentric fragment
9
0.35
8
0.95
19
1.40
Ring chromosome
-
-
-
-
2
0.15
Dicentric chromosome
-
-
-
-
2
0.15
Total
9
0.35
8
0.95
23
1.69
Frequency of Stable Chromosome-Type Aberrations
Karyotypes examined
460
144
237
Deletion
19
4.13
10
6.94
27
11.39
Inversion
4
0.87
1
0.69
4
1.68
Translocation
3
0.65
2
1.38
5
2.10
Total
26
5.65
13
9.02
36
15.18
aKiraly et al. (1979).
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Table B.2. Relative Liver Weight and Serum Cholesterol of Sprague-Dawley Rats
Administered 1,2,4,5-TCB in Diet for 28 Daysa'b
Male
Control
500 ppm (32 mg/kg-d)
Relative liver weight (% of body weight)
4.5 ±0.54
5.9 ±0.42* (131)
Serum cholesterol (mg/100 mL)
86 ±9.5
112 ±9.8* (130)
Female
Control
500 ppm (56 mg/kg-d)
Relative liver weight (% of body weight)
4.4 ±0.30
5.3 ±0.51* (120)
Serum cholesterol (mg/100 mL)
86 ± 13
110 ±7* (128)
aChu et al. (1983).
bValues represent mean ± SD (% of control); % of control is calculated; n = 9-10 per group.
* Significantly different from control, p < 0.05. Study authors reported liver weights and serum cholesterol only for
the control and highest dose group (500 ppm) and no intermediate dose groups.
Table B.3. Hepatic Mixed-Function Oxidase Activities of Rats Administered 1,2,4,5-TCB
in Diet for 28 Daysa'b
Parameter0
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
Male
0.0 (Control)
0.5 (0.041)
5.0 (0.42)
50 (3.4)
500 (32)
AH (nmol PAP/h x mg protein)
12 ±5.1
15 ± 1.9
(125)
14 ±3.6
(117)
19 ±4.0
(158)
33 ±6.5*
(275)
ER (nmol/min x mg protein)
0.02 ±0.02
0.10 ±0.07
(500)
0.14 ±0.16
(700)
0.22 ± 0.27
(1,100)
0.23 ±0.25*
(1,150)
APDM (nmol HCHO/h x mg protein)
20 ±7.1
26 ±6.8
(130)
26 ±6.9
(130)
35 ±7.6*
(175)
64 ± 18*
(320)
Females
0.0 (Control)
0.5 (0.059)
5.0 (0.61)
50 (6.2)
500 (56)
AH (nmol PAP/h x mg protein)
20 ±6.9
22 ±7.9
(110)
22 ± 7.6
(110)
23 ±7.2
(115)
34 ± 1.5
(170)
EROD (nmol/min x mg protein)
0.09 ±0.08
0.12 ±0.06
(133)
0.13 ±0.08
(144)
0.14 ±0.06
(156)
0.18 ±0.04
(200)
APDM (nmol HCHO/h x mg protein)
16 ±3.0
16 ±4.2
(100)
16 ±2.0
(100)
17 ±2.7
(106)
36 ±8.8*
(225)
aChu et al. (1983).
bValues represent mean ± SD (% of control); % of control is calculated; n = 8-10 per group.
°AH = aniline hydroxylase; APDM = aminopyrine demethylase; ERD = ethoxyresorufin O-deethylase
* Significantly different from control (p < 0.05).
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Table B.4. Incidence of Selected Histopathological Lesions in Sprague-Dawley Rats
Administered 1,2,4,5-TCB in Diet for 28 Daysa'b
Parameter
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
Male
0.0
(Control)
0.5
(0.041)
5.0 (0.42)
50 (3.4)
500 (32)
Liver
0/10
2/10
0/10
4/10
10/10
Thyroid
0/10
5/10
3/10
4/10
9/10
Kidney
1/10
0/10
0/10
5/10
8/10
Lung
0/10
4/10
5/10
2/10
6/10
Female
0.0
(Control)
0.5
(0.059)
5.0 (0.61)
50 (6.2)
500 (56)
Liver
0/10
1/10
1/10
3/10
10/10
Thyroid
0/10
2/10
3/10
4/10
6/10
Kidney
4/10
1/10
2/10
3/10
3/10
Lung
3/10
NE
NE
NE
2/10
aChu et al. (1983).
bValues expressed as animals showing lesions/animals examined.
NE = not examined.
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Table B.5. Average Body Weights and Relative Organ Weights of Male and Female
Rats Administered 1,2,4,5-TCB (Recrystallized) in Diet for 90 Days"
Males
Exposure Group, % in Diet (Average Daily Dose, mg/kg-d)
0(0)
30 (2.7)
100 (9.0)
Number of animals
10
9
9
Average body weight (g)
325
325 (100)
329 (101)
Average relative organ weights (g/100 g body weight)
Lung
0.63
0.61 (97)
0.55 (87)
Heart
0.33
0.32 (97)
0.32 (97)
Liver
2.76
2.70 (98)
2.84 (103)
Kidney
0.75
0.76(101)
0.80 (107)
Spleen
0.30
0.29 (97)
0.26 (87)
Testes
0.91
0.91 (100)
0.93 (102)
Females
0(0)
30 (3.0)
100 (10.1)
Number of animals
10
9
10
Average body weight (g)
193
201 (104)
199 (103)
Average relative organ weights (g/100 g body weight)
Lung
0.71
0.68 (96)
0.69 (97)
Heart
0.38
0.37 (97)
0.36 (95)
Liver
2.88
2.93 (102)
3.11* (108)
Kidney
0.78
0.80 (103)
0.80 (103)
Spleen
0.35
0.33 (94)
0.34 (97)
aDow Chemical Co. (1984b).
bStudy authors provided only mean values and no variance data; (% of control in parentheses is calculated).
* Significantly different from control (p < 0.01).
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Table B.6. Survival, Mean Body Weights, and Food Consumption of Rats Administered
1,2,4,5-TCB in Diet for 13 Weeks"

Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
Male
0 (0.0)
30 (2.1)
100 (7.1)
300 (22.1)
1000 (71.4)
2000 (156)
Survival13
10/10
10/10
10/10
10/10
10/10
10/10
Mean body weight (g)°
Initial
116 ± 5
122 ±5
117± 5
119 ± 4
121 ±4
119 ± 4
Final
334 ± 10
331 ±4
336 ±4
316 ± 6
299 ±6
265 ±4
Change
218 ± 7
210 ±7
219 ± 4
197 ±7
178 ±3
146 ±3
Final weight relative to controls (%)
-
99
101
95
90
79
Food consumption (g/animal/d)
16
16
16
16
15
15
Female
0 (0.0)
30 (2.1)
100 (7.3)
300 (22.4)
1000 (79.1)
2000 (151)
Survival13
10/10
10/10
10/10
10/10
10/10
10/10
Mean body weight (g)
Initial
101 ±3
99 ±3
100 ±3
98 ±3
95 ±3
97 ±3
Final
200 ±3
193 ±4
203 ±3
197 ±3
183 ±3
168 ±3
Change
100 ±4
93 ±2
103 ±2
99 ±2
88 ±3
71 ± 2
Final weight relative to controls (%)
-
97
102
99
92
84
Food consumption (g/animal/d)
22
20
11
11
11
10
aNTP (1991c).
bExpressed as number of animals surviving/number of animals in group.
°Values represent mean ± SE.
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Table B.7. Liver and Kidney Weights of F344 Rats Administered 1,2,4,5-TCB in Diet for
13 Weeksa b
Male
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
0 (0.0)
30 (2.1)
100 (7.1)
300 (22.1)
1,000 (71.4)
2,000 (156)
Body weight (g)
347 ±8.3
340 ±4.2
(98)
296 ± 16.2*
(85)
333 ±5.8
(96)
299 ±6.5**
(86)
283 ±4.9**
(82)
Right kidney
Absolute
1,312 ±39
1,268 ± 18
(97)
1,263 ± 27
(96)
1,608 ± 39**
(123)
1,970± 68**
(150)
1,849 ± 74**
(141)
Relative
3.8 ±0.07
3.7 ±0.04
(97)
4.3 ±0.15**
(113)
4.8 ±0.07**
(126)
6.6 ±0.15**
(174)
6.5 ±0.16**
(171)
Liver
Absolute
12,660 ± 380
12,670 ± 180
(100)
10,590 ± 1,060
(84)
14,270 ± 370*
(113)
17,230 ± 530**
(136)
19,170 ±520**
(151)
Relative
36.4 ±0.52
37.2 ±0.27
(102)
35.0 ± 1.75
(96)
42.9 ±0.68**
(118)
57.6 ± 1.20**
(158)
67.6 ± 1.17**
(186)
Female
0 (0.0)
30 (2.1)
100 (7.3)
300 (22.4)
1,000 (79.1)
2,000 (151)
Body weight (g)
201 ±2.9
191 ±4.4
(95)
207 ±2.9
(103)
199 ±3.3
(99)
188 ±3.0*
(94)
173 ±2.7**
(86)
Right kidney
Absolute
776 ± 18
734 ± 20
(95)
821 ± 16
(106)
844±15*
(109)
838 ±24*
(108)
871 ±25*
(112)
Relative
3.9 ±0.07
3.8 ±0.06
(97)
4.0 ±0.08
(103)
4.2 ±0.06**
(108)
4.5 ±0.08**
(115)
5.0 ±0.12**
(128)
Liver
Absolute
6,445 ± 137
6,610 ±239
(103)
7,304 ± 151**
(113)
7,515 ± 164**
(117)
9,512 ±215**
(148)
11,908 ±312
(185)
Relative
32.1 ±0.43
34.5 ±0.84*
(107)
35.3 ±0.63**
(110)
37.7 ±0.50**
(117)
50.6 ±0.83**
(158)
68.9 ± 1.55**
(215)
aNTP (1991c).
bValues represent mean ± SE (absolute organ weight in mg, relative in mg/g) for groups of 10 animals (% of
control); % of control is calculated.
*p < 0.05, Dunn's test or Shirley's test.
**p < 0.01, Dunn's test or Shirley's test.
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Table B.8. Serum Thyroid Hormone Concentrations in F344 Rats Administered
1,2,4,5-TCB in Diet for 13 Weeks"
Endpoint
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
Male
0 (0.0)
30 (2.1)
100 (7.1)
300 (22.1)
1,000 (71.4)
2,000 (156)
Free thyroxin (ng/dL)
Day 3/4
2.1 ±0.11
2.0 ±0.16
(95)
1.9 ±0.09
(90)
1.3 ±0.15° **
(62)
0.4 ±0.04**
(19)
0.3 ±0.02**
(14)
Day 45/46
2.0 ±0.19
1.8 ± 0.15
(90)
2.2 ±0.20
(110)
1.3 ±0.13**
(65)
0.6 ±0.07**
(30)
0.2 ±0.02**
(10)
Day 88/89
1.7 ±0.13
1.5 ± 0.11
(88)
1.5 ± 0.14
(88)
1.0 ±0.12**
(59)
0.5 ±0.04**
(29)
0.2 ±0.03**
(12)
Total thyroxin (|ig/dL)
Day 17/18
5.1 ±0.42
5.1 ±0.49
(100)
4.9 ±0.38
(96)
3.0 ±0.16**
(59)
1.6 ± 0.13**
(31)
1.2 ± 0.11**
(24)
Day 45/46
5.1 ±0.29
4.6 ±0.33
(90)
5.1 ±0.25
(100)
3.4 ±0.19**
(67)
2.0 ±0.15**
(39)
1.3 ±0.08**
(25)
Day 88/89
4.2 ±0.16
4.1 ±0.39
(98)
4.1 ±0.37
(98)
3.3 ±0.32
(79)
1.9 ±0.14**
(45)
1.3 ±0.05**
(31)
Female
0 (0.0)
30 (2.1)
100 (7.3)
300 (22.4)
1,000 (79.1)
2,000 (151)
Free thyroxin (ng/dL)
Day 3/4
2.0 ±0.10
1.7 ±0.09*
(85)
1.6 ±0.09*
(80)
1.1 ±0.08**
(55)
0.4 ±0.03**
(20)
0.2 ±0.02**
(10)
Day 45/46
1.6 ±0.14
0.9 ±0.10**
(56)
1.3 ±0.18*
(81)
1.0 ±0.07**
(63)
0.4 ±0.04**
(25)
0.2 ± 0.03°'**
(13)
Day 88/89
1.0 ±0.08
1.0 ± 0.11
(100)
0.8 ±0.09
(80)
0.6 ±0.10**
(60)
0.3 ±0.03**
(30)
0.2 ±0.03**
(20)
Total thyroxin (|ig/dL)
Day 17/18
4.7 ±0.32
3.8 ±0.25
(81)
3.8 ± 0.31
(81)
2.5 ±0.22**
(53)
1.4 ±0.08**
(30)
1.2 ±0.08**
(26)
Day 45/46
4.6 ± 0.24
2.8 ±0.21**
(61)
3.8 ±0.32**
(83)
3.2 ±0.17**
(70)
1.6 ±0.06**
(35)
1.2 ±0.06**
(26)
Day 88/89
2.8 ±0.21
2.6 ±0.24
(93)
2.6 ± 0.11
(93)
1.8 ±0.19**
(64)
1.4 ±0.06**
(50)
1.2 ±0.08**
(43)
aNTP (1991c).
bData for animals bled sequentially on Days 3 or 4, 17 or 18, 45 or 46, and 88 or 89; values represent mean ± SE for
groups of 10 animals unless otherwise specified (% of control); % of control is calculated.
°Nine animals were examined.
*p < 0.05, Dunn's test or Shirley's test.
**p < 0.01, Dunn's test or Shirley's test.
IU = international units.
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Table B.9. Survival, Mean Body Weights, and Feed Consumption of B6C3Fi Mice
Administered 1,2,4,5-TCB in Diet for 13 Weeks"
Male
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
0 (0.0)
30 (4.5)
100 (14.6)
300 (45.2)
1,000 (150)
2,000 (278)
Survival13
10/10
10/10
10/10
10/10
10/10
10/10
Mean body weight (g)°
Initial
21.4 ±0.5
20.8 ±0.7
21.5 ±0.4
20.7 ±0.3
20.5 ±0.4
20.8 ±0.6
Final
32.1 ±0.7
29.7 ±0.7
31.9 ± 0.8
29.7 ±0.7
30.0 ±0.7
29.6 ±0.8
Change
10.7 ±0.6
8.8 ±0.2
10.3 ±0.6
9.0 ±0.4
9.5 ±0.4
8.8 ±0.6
Final weight relative to controls (%)
-
92.5
99.4
92.5
93.5
92.2
Food consumption (g/animal/d)
3.9
3.8
3.9
3.8
3.8
3.5
Female
0 (0.0)
30 (6.0)
100 (19.7)
300 (56.6)
1,000 (143)
2,000 (302)
Survival13
10/10
10/10
10/10
10/10
10/10
9/10d
Mean body weight (g)°
Initial
16.8 ±0.3
16.7 ±0.4
17.2 ±0.4
16.9 ±0.5
16.8 ±0.3
16.5 ±0.3
Final
25.4 ±0.5
25.1 ±0.5
25.5 ±0.7
25.5 ±0.7
25.3 ±0.6
24.6 ±0.5
Change
8.6 ±0.3
8.4 ±0.3
8.3 ±0.4
8.6 ±0.5
8.5 ±0.4
8.3 ±0.5
Final weight relative to controls (%)
-
98.8
100.4
100.4
99.6
96.9
Food consumption (g/animal/d)
4.1
4.2
4.2
4.0
3.0
3.1
aNTP (1991d).
bExpressed as number of animals surviving/number of animals in dose group.
°Values represent mean ± SE.
dWeek of death: 2; an additional animal died during Week 13, after the end of dosing.
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Table B.10. Liver and Kidney Weights of B6C3Fi Mice Administered 1,2,4,5-TCB in Diet
for 13 Weeks"
Male
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
0 (0.0)
30 (4.5)
100 (14.6)
300 (45.2)
1,000 (150)
2,000 (278)
Number of animals
10
10
10
10
10
10
Body weight (g)
32.6 ±0.96
30.8 ±0.59
(94)
33.1 ± 0.71
(102)
31.2 ±0.66
(96)
31.9 ±0.76
(98)
31.3 ±0.74
(96)
Liver
Absolute
1,373 ±58
1,367 ± 44
(100)
1,546 ± 42*
(113)
1,458 ± 60
(106)
2,022 ± 67**
(147)
3,700 ± 80**
(269)
Relative
42.1 ± 1.31
44.4 ± 1.03
(105)
46.8 ± 1.19*
(HI)
46.6 ± 1.04*
(HI)
63.3 ± 1.35**
(150)
118.4 ±2.86**
(281)
Female
0 (0.0)
30 (6.0)
100 (19.7)
300 (56.6)
1,000 (143)
2,000 (302)
Number of animals
10
10
10
10
10
10
Body weight (g)
25.6 ±0.53
26.4 ±0.55
(103)
26.3 ±0.78
(103)
26.7 ± 0.67
(104)
27.7 ±0.69*
(108)
26.5 ± 0.29
(104)
Right kidney
Absolute
190 ±4
199 ±3
(105)
206 ± 7*
(108)
196 ±7
(103)
208 ± 5*
(109)
214 ±9*
(113)
Relative
7.4 ±0.16
7.5 ±0.12
(101)
7.8 ±0.17
(105)
7.4 ±0.21
(100)
7.5 ±0.13
(101)
8.1 ±0.31
(109)
Liver
Absolute
1,183 ±38
1,306 ±36*
(110)
1,273 ± 52
(108)
1,312 ±63
(HI)
2,086 ±73**
(176)
4,171 ±234**
(353)
Relative
46.3 ± 1.41
49.4 ±0.81
(107)
48.4 ± 1.43
(105)
49.1 ± 1.58
(106)
75.4 ± 1.64**
(163)
156.9 ±7.56**
(339)
aNTP (1991d).
bValues represent mean ± SE (absolute weights in mg, relative weights in mg/g body weight) for groups of
10 animals (% of control); % of control is calculated.
*p < 0.05, Dunn's or Shirley's test.
**p < 0.01, Dunn's or Shirley's test.
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Table B.ll. Incidence of Selected Histopathological Lesions in B6C3Fi Mice Administered

1,2,4,5-TCB in Diet for 13 Weeks3'"



Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
Male
0 (0.0)
30 (4.5)
100 (14.6)
300 (45.2)
1,000 (150)
2,000 (278)
Liver
Necrosis
0
0
0
0
0
4 (1.7)
Centrilobular hypertrophy
0
0
0
0
7 (1.0)
10(1.4)
Degeneration
0
0
0
0
0
9 (1.4)
Heart
Mineralization
0
0
0
2(1.5)
0
3 (2.3)
Female
0 (0.0)
30 (6.0)
100 (19.7)
300 (56.6)
1,000 (143)
2,000 (302)
Liver
Necrosis
0
1 (1.0)
0
0
i (i.o)
i (i.o)
Centrilobular hypertrophy
0
0
0
0
7 (1.0)
9 (1.8)
Degeneration
0
0
0
0
0
5 (1.2)
aNTP (1991d).
bTen animals were examined in each group. Number in parentheses denotes mean grade of severity: 1 = minimal;
2 = mild; 3 = moderate.
Table B.12. Effects of 1,2,4,5-TCB Exposure to Pregnant Sprague-Dawley Rats from
GDs 6-15a
Parametersb
Exposure Group (mg/kg-d)
0
50
100
200
Platelets (x 106/mm3)
13.5 ± 1.6
(» = 8)
10.8 ± 1.1 (« = 8) (80)
11.7 ±2.1 (n = 7) (87)
10.8 («= 1)
(80)
Serum cholesterol (mg/100 mL)
82 ± 9 (n = 3)
105 ± 19 (n = 7) (128)*
103 ± 20 (n = 7) (126)*
ND
Liver AH (|imol/hr/mg protein)
11.9 ± 3.8
(« = 3)
19.9 ±6.4 (n = 7)
(167)*
19.9 ±6.0 (n = 7)
(167)*
32.6 (n = 1)
(274)
Liver AP (|imol/hr/mg protein)
16.2 ±2.9
(« = 3)
26.5 ± 7.7(164)* (n = 7)
24.7 ±9.3 (n = 7) (152)
47.3 (n = 1)
(292)
Number of fetuses per dam
14.0 ±4.2
(» = 8)
8.3 ±5.5 (59)*
(» = 8)
13.5 ±2.1 (96)
(n = 7)
12 (n = 1)
aKacew et al. (1984).
bValues represent mean ± SD (% of control); % of control is calculated.
* Statistically significant at p< 0.05; Duncan's Multiple Range Test.
ND = not determined. AH = aniline hydroxylase, AP = alkaline phosphatase.
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Table B.13. Effects of Exposure to 1,2,4,5-TCB on Female Sprague-Dawley Rats during
Gestation Days 9-14a
Parameterb'c
Exposure Group (mg/kg-d)
0
30
100
300
1,000
Body-weight gaind
34.33 ±
2.50
39.46 ±4.76
(115)
26.65 ± 4.03 (78)
29.08 ±5.40
(85)
15.15 ±4.11
(44)
Liver weight
11.22 ±
0.44
11.77 ±0.46
(105)
11.57 ±0.30
(103)
11.68 ±0.25
(104)
10.39 ±0.46
(93)
Cytochrome P450
0.52 ±0.03
0.52 ±0.05 (100)
0.52 ±0.02 (100)
0.57 ±0.05
(110)
0.85 ±0.19
(163)
NADPH cytochrome c
reductase
127.38 ±
9.26
154.14 ± 16.85
(121)
145.11 ± 11.37
(114)
141.97 ±6.32
(HI)
134.21 ±8.00
(105)
Ethoxyresorufin
O-deethylase
14.10 ±
1.68
29.95 ±3.29
(212)
40.03 ±2.65
(284)
49.71 ±5.86
(353)
48.96 ±6.66
(347)
Aminopyrine
.Y-dcmcthvlase
2.26 ±0.19
2.47 ±0.24 (109)
2.51 ± 0.19 (111)
3.41 ±0.43
(151)
3.47 ±0.56
(154)
aKitchin and Ebron (1983).
bValues represent mean ± SE (% of control); % of control is calculated.
Data are digitized by the GetData Digitizer.
dNumber of animals ranged from 6-8 (specific numbers per dose group not reported).
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Table B.14. Organ Weights and Reproductive Data of Sprague-Dawley (CD) Rats
Administered 1,2,4,5-TCB in the Diet during a Two-Generation Reproduction Studya'b
F0 Adult Males0
Exposure Group, ppm (Adjusted Daily Dose, mg/kg-d)
0 (0.0)
30.0 (2.2)
300.0 (21.1)
1,000.0 (70.3)
Final body weight (g)
583.6 ±60.19
561.5 ± 51.33 (96)
562.4 ±57.59 (96)
495.8 ± 39.64** (85)
Liver (g)
20.846 ±3.01
20.208 ± 2.77 (97)
23.587 ±3.21** (113)
30.640 ±2.73**
(147)
Kidney (g)
3.729 ±0.27
3.852 ±0.38 (103)
5.288 ±0.93** (142)
6.101 ±0.92** (164)
Brain (g)
2.107 ±0.09
2.108 ±0.08 (100)
2.118 ±0.08 (101)
2.091 ±0.10 (96)
Testes (g)
3.524 ±0.24
3.491 ±0.31 (99)
3.687 ±0.28 (105)
3.751 ±0.33* (106)
F0 Adult Females'1
0 (0.0)
30.0 (2.6)
300.0 (25.5)
1,000.0 (82.5)
Final body weight (g)
307.9 ± 18.54
308.5 ± 16.84 (100)
306.0 ±21.47 (99)
294.8 ± 25.79 (96)
Liver (g)
12.570 ± 1.68
13.023 ± 1.36 (104)
13.336 ± 1.13 (106)
15.650 ± 1.04**
(125)
Kidney (g)
2.402 ±0.21
2.380 ±0.21 (99)
2.467 ±0.19 (103)
2.458 ±0.21 (102)
Brain (g)
1.996 ±0.09
2.003 ±0.08 (100)
1.947 ±0.09 (98)
1.933 ±0.06* (97)
F1 pup parameters
0
30.0
300.0
1,000.0
Live birth index
98.8 ±3.38 (n = 24)
98.7 ±3.83 (n = 25)
98.9 ± 3.38 (« = 26)
78.9 ±20.1**
(n = 24)
7-Day survival index
100 ± 0.0 (n = 24)
96 ± 20.0 (n = 24)
100 ± 0.0 (n = 26)
1.3 ± 4.62** («= 13)
Lactation index
100 ± 0.0 (n = 24)
96 ± 10.0 (n = 25)
88.5 ±22.89**
(n = 26)
0.0 ± 0.0** (n = 13)
F2 pup parameters
0
30.0
300.0
1,000.0
Live birth index
94.3 ±21.21
(« = 22)
97.0 ± 5.43 (n = 19)
93.8 ± 14.55 (« = 22)
-
7-Day survival index
100.0 ±0.0 (« = 21)
100.0 ± 0.0 (n = 19)
98.2 ± 8.18 (« = 21)
-
Lactation index
100.0 ±0.0 (« = 21)
100.0 ± 0.0 (n = 19)
84.9 ±27.37**
(« = 21)
-
aTyl and Neeper-Bradley (1989).
bValues represent mean ± SD for groups of 28 animals (% of control); % of control is calculated.
Sacrificed at Week 15.
Sacrificed at Week 17.
* Significantly different from control, p < 0.05.
**Significantly different from control, p < 0,01,
indicates that no F2 pups were bred for this dose group due to entire litter loss at the high dose.
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Table B.15. Reproductive Parameters of F0 Generation CD-I Mice Administered
1,2,4,5-TCB in Diet for 18 Weeks"
Parameterb
Exposure Group, % in Diet0
0
0.028
(42 or 43 mg/kg-d)
0.072
(109 or 108 mg/kg-d)
Average no. of litters per pair
4.9 ±0.0
5.0 ±0.0 (102)
5.0 ±0.0 (102)
Live pups per litter
Male
6.0 ±0.2
5.6 ±0.3 (93)
5.5 ±0.2 (92)
Female
6.2 ±0.3
6.2 ±0.4 (100)
5.9 ±0.3 (95)
Combined
12.2 ±0.4
11.8 ±0.5 (97)
11.4 ±0.3* (93)
Proportion of F1 pups born alive
0.96 ±0.02
0.95 ±0.03 (99)
1.00 ±0.00 (104)
Sex of F1 pups born alive (male/total)
0.50 ±0.01
0.48 ±0.01* (96)
0.49 ± 0.02 (98)
Live pup weight (g)
Male
1.55 ±0.02
1.57 ±0.02 (101)
1.57 ±0.02 (101)
Female
1.51 ±0.02
1.51 ±0.02 (100)
1.50 ±0.01 (99)
Combined
1.53 ±0.02
1.54 ±0.02 (101)
1.53 ±0.02 (100)
Adjusted live pup weight (g)
Male
1.55 ±0.02
1.57 ±0.02 (101)
1.57 ±0.02 (101)
Female
1.52 ±0.01
1.51 ±0.02 (99)
1.48 ±0.02 (97)
Combined
1.53 ±0.01
1.54 ±0.02 (101)
1.53 ±0.02 (100)
aNTP (1991e).
bValues represent mean ± SE (% of control); % of control is calculated.
°Results for the high-dose group (0.18% in diet) are not reported due to high mortality preceding termination of the
study.
* Statistically significant at p< 0.05; Dunnett's test conducted by study authors.
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Table B.16. Relative Organ Weights of F0 Generation Following 18 Weeks Exposure to
1,2,4,5-TCB in Male CD-I Mice"
Parameterb
Exposure Group, % in Diet
0
0.18
(246 or 253 mg/kg-d)
Number of animals
20
20
Liver
51.2± 1.1
99.8 ±2.5 (195)*
Right cauda epididymis
0.43 ±0.01
0.46 ±0.01 (107)*
Right epididymis
1.4 ±0.06
1.3 ±0.03 (93)*
Kidney/adrenal
20.3 ± 0.60
20.6 ±0.33 (101)
Prostate
0.61 ±0.03
0.57 ±0.03 (93)
Seminal vesicles
11.8 ± 0.39
12.3 ±0.30 (104)
Right testis
3.5 ±0.08
3.3 ±0.16 (94)
aNTP (1991e).
bValues represent mean ± SE (% of control); % of control is calculated.
* Statistically significant at p< 0.05; Wilcoxon test conducted by study authors.
Table B.17. Relative Organ Weights of F1 Generation Following 18 Weeks Exposure to
1,2,4,5-TCB in Male CD-I Mice"
Parameterb
Exposure Group, % in Diet
0
0.072
(108 mg/kg-d)
Number of animals
20
20
Liver
50.7 ±0.85
98.2 ± 1.3 (194)*
Right cauda epididymis
0.46 ±0.01
0.45 ±0.81(98)
Right epididymis
1.4 ±0.03
1.4 ±0.03 (100)
Kidney/adrenal
20.7 ±0.86
24.6 ±0.68 (119)*
Prostate
0.66 ±0.03
0.61 ±0.03(92)
Seminal vesicles
11.1 ± 0.25
10.8 ±0.23(97)
Right testis
3.4 ± 0.11
3.9 ±0.15(115)*
aNTP (1991e).
bData reported as mean (mg/g body weight) ± SE (% of control); % of control is calculated.
* Statistically significant at p< 0.05; Wilcoxon test conducted by study authors.
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Table B.18. Relative Organ Weights of F1 Generation Following 18 Weeks Exposure to
1,2,4,5-TCB in Female CD-I Mice"
Parameterb
Exposure Groups, % in Diet
0
0.072
(127 mg/kg-d)
Number of animals
20
20
Liver
55.7± 1.1
76.9 ± 1.5 (138)*
Kidney/adrenal
15.7 ±0.32
16.8 ±0.21 (107)*
Right ovary
0.28 ±0.02
0.24 ±0.01 (86)
aNTP (1991e).
bData reported as mean (mg/g body weight) ± SE (% of control); % of control is calculated.
* Statistically significant at p < 0.05; Wilcoxon test conducted by study authors.
Table B.19. Incidence of Histopathologic Lesions of F1 Generation Following 18 Weeks
Exposure to 1,2,4,5-TCB in Male CD-I Micea'b


Exposure group, % in Diet
Organ
Parameter
0
0.072
(108 mg/kg-d)
Number examined
10
10
Severity
Mild
Mod.
Sev.
Mild
Mod.
Sev.
Liver
Hepatocellular degeneration
1
0
0
0
0
0

Focal hepatitis
1
0
0
3
0
0

Cytomegaly and karyomegaly
0
0
0
4
6
0
Testis
Degeneration of seminiferous tubules
2
0
0
0
0
0
Epididymis
Degeneration of epithelial cell
1
0
0
0
0
0
Kidney
Dilation of tubules
0
0
0
4
2
0

Interstitial nephritis
2
0
0
1
0
0

Regeneration of tubules
3
0
0
7
0
0
aNTP (1991e).
bData reported as number of animals showing effect.
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Table B.20. Incidence of Histopathologic Lesions of F1 Generation Following 18 Weeks
Exposure to 1,2,4,5-TCB in Female CD-I Micea'b


Exposure group, % in Diet
Organ
Parameter
0
0.072
(127 mg/kg-d)
Number examined
10
10
Severity
Mild
Mod.
Sev.
Mild
Mod.
Sev.
Liver
Hepatitis
3
0
0
5
0
0

Cytomegaly and karyomegaly
0
0
0
0
7
2
Kidney
Tubular dilation
1
0
0
0
0
0

Tubular degeneration
0
0
0
2
0
0

Interstitial nephritis
1
0
0
2
0
0

Tubular regeneration
2
0
0
5
2
0
aNTP (1991e).
bData reported as number of animals showing effect.
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APPENDIX C. BMD OUTPUTS
Multistage Model with 0.95 Confidence Level
dose
13:32 04/08 2011
Figure C.l. Multistage (degree = 3) BMD Model for Liver Lesions in Male Rat Data
(Chu et al., 1983)
Text Output for Multistage (degree = 3) BMD Model for Liver Lesions in Male Rat Data
(Chu et al., 1983)
Multistage Model. (Version: 3.2; Date: 05/26/2010)
Input Data File: C:/89/Chu_et_al_1983_liver_lesions_m_Multi3_l.(d)
Gnuplot Plotting File: C:/89/Chu_et_al_1983_liver_lesions_m_Multi3_l.pit
Fri Apr 08 13:32:27 2011
Histopath_liver_lesions_in_male_rats
The form of the probability function is:
P[response] = background + (1-background)*[1-EXP(
-betal*dose/sl-beta2*dose/s2-beta3* dose^)]
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The parameter betas are restricted to be positive
Dependent variable = DiffEff
Independent variable = Dose
Total number of observations = 5
Total number of records with missing values = 0
Total number of parameters in model = 4
Total number of specified parameters = 0
Degree of polynomial = 3
Maximum number of iterations = 250
Relative Function Convergence has been set to: le-008
Parameter Convergence has been set to: le-008
Default Initial Parameter Values
Background =	0
Beta(l) =	0
Beta(2) =	0
Beta(3) = 3.05267e+015
Asymptotic Correlation Matrix of Parameter Estimates
( *** The model parameter(s) -Beta(l) -Beta(2)
have been estimated at a boundary point, or have been specified by
the user,
and do not appear in the correlation matrix )
Background	Beta(3)
Background	1	-0.42
Beta (3)	-0.42	1
Parameter Estimates
Interval
Variable
Limit
Background
Beta(1)
Beta(2)
Beta(3)
Estimate
0.0667078
0
0
0. 0112085
Std. Err.
95.0% Wald Confidence
Lower Conf. Limit Upper Conf.
Indicates that this value is not calculated.
Analysis of Deviance Table
Model
Full model
Fitted model
Reduced model
Log(likelihood)
-11.7341
-14.0863
-31.3435
# Param's
5
2
1
Deviance Test d.f.
4 .70435
39.2187
P-value
0.194E
<.0001
AIC:
32.1726
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Goodness of Fit
Scaled
Dose	Est._Prob. Expected Observed	Size	Residual
0.0000
0.0667
0.667
0.000
10
-0.845
0.0410
0.0667
0.667
2.000
10
1. 689
0.4200
0.0675
0.675
0.000
10
-0.851
3.4000
0.3992
3.992
4.000
10
0. 005
32.0000
1.0000
10.000
10.000
10
0. 000
Chi^2 = 4.29	d.f. = 3	P-value = 0.2316
Benchmark Dose Computation
Specified effect =	0.1
Risk Type =	Extra risk
Confidence level =	0.95
BMD =	2.11046
BMDL =	0.45 6132
BMDU =	3.37 67
Taken together, (0.45 6132, 3.37 67 ) is a 90	% two-sided confidence
interval for the BMD
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APPENDIX D. REFERENCES
ACGIH (American Conference of Governmental Industrial Hygienists). (2013) 2013 TLVs and
BEIs. Based on the documentation of the threshold limit values for chemical substances and
physical agents & biological exposure indices. ACGIH, Cincinnati, OH. 1798797
ATSDR (Agency for Toxic Substances and Disease Registry). (2013) Minimal risk levels
(MRLs) for hazardous substances. ATSDR, Atlanta, GA. Available online at
http://www.atsdr.cdc.gov/mrls/pdfs/atsdr rnris iuly 2013.pdf. 1798743
Bayer, AG. (1993) Micronucleus test on the mouse with 1,2,4,5-tetrachlorobenzene with cover
letter dated 070993. Miles Inc., Pittsburgh, PA; 930000327, NTIS No. OTS0537763. 677328.
Braun, WH; Sung, LY; Keyer, DG; Kociba, RJ. (1978a) Pharmacokinetic and toxicological
evaluation of dogs fed 1,2,4,5-tetrachlorobenzene in the diet for two years. J Environ Pathol
Toxicol 2(2):225-234. 677336.
Braun, WH; Sung, LY; Keyes, DG; Kociba, RJ. (1978b) Pharmacokinetic and toxicological
evaluation of dogs fed 1,2,4,5-tetrachlorobenzene in the diet for two years. J Toxicol Environ
Health 4(5-6):727-734. 677337.
Bushy Run Research Center. (1988) Reproduction and fertility study on
1,2,3,4-tetrachlorobenzene with two cover letters dated 012688 and 012088 (draft). Standard
Chlorine Chemical Co., Export, PA; NTIS No. OTS0000594. 677329.
Cal/EPA (California Environmental Protection Agency). OEHHA toxicity criteria database.
Office of Environmental Health Hazard Assessment, Sacramento, CA. Available online at
http://www.oehha.ca.gov/risk/ChemicalDB/index.asp. Accessed on 9-26-2013.
Cal/EPA (California Environmental Protection Agency). (2013 a) All OEHHA Acute, 8-hour
and Chronic Reference Exposure Levels (chRELs) as of August 2013. Office of Environmental
Health Hazard Assessment, Sacramento, CA. Available online at
http://www.oehha.ca.gov/air/allrels.html. 1935906
Cal/EPA (Environmental Protection Agency). (2013b) Current proposition 65 list [09/13/13],
Office of Environmental Health Hazard Assessment, Sacramento, CA. Available online at
http://oehha.ca.gov/prop65/prop65 list/Newlist.html. 1936438
Cal/EPA (California Environmental Protection Agency). (2009) Hot spots unit risk and cancer
potency values. Appendix A. Office of Environmental Health Hazard Assessment, Sacramento,
CA. Available online at http://www.oehha.ca.gov/air/hot spots/pdf/CPFs042909.pdf. Accessed
on February 14, 2011. 684164.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470297/pdf/envhper00326-0344.pdf. 710666.
61	1,2,4,5-Tetrachlorobenzene

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9-27-2013
Chu, I; Villeneuve, D; Secours, V; Valli, VE. (1983) Comparative toxicity of 1,2,3,4-, 1,2,4,5-,
and 1,2,3,5-tetrachlorobenzene in the rat: results of acute and subacute studies. J Toxicol
Environ Health ll(4-6):663-677. 677338.
Chu, I; Villeneuve, DC; Valli, VE; Secours, VE. (1984a) Toxicity of 1,2,3,4-, 1,2,3,5- and
1,2,4,5-tetrachlorobenzene in the rat: results of a 90-day feeding study. Drug Chem Toxicol
7(2): 113—127. Available online at http://dx.doi.ore/10.3109/01480548408998410. 677339.
Chu, I; Villeneuve, DC; Viau, A; et al. (1984b) Metabolism of 1,2,3,4-, 1,2,3,5-, and
1,2,4,5-tetrachlorobenzene in the rat. J Toxicol Environ Health 13(4-6):777-786. 677340.
Dow. (1982a) Results of 92-day dietary feeding studies on 1,2,4,5- tetrachlorobenzene in beagle
dogs. Dow Chemical Company, Midland, MI; 878211212, NTIS No. OTS0206149. Submitted
under TSCA Section 017945. 677331.
Dow. (1982b) Results of 144 day dietary feeding studies on 1,2,3,4- and
1,2,4,5-tetrachlorobenzene in beagle dogs. Dow Chemical Corp, Midland, MI; 878211086,
NTIS No. OTS84003A. 677332.
Dow. (1984a,b) Results of dietary feeding of 1,2,4,5-tetrachlorobenze to rats. Dow Chemical
Company, Midland, MI. 677334.
Fisher, LC; Tyl, RW; Butler, BL; et al. (1990a,b) Developmental toxicity evaluation of
1,2,4,5-tetrachlorobenzene (TCB) administered by gavage to Fischer 344 (F-344) rats and New
Zealand White (NZW) rabbits [Abstract], Teratology 41(5):556. 659971.
Fomenko, VN. (1965) Determination of the maximum permissible concentration of
tetrachlorobenzene in water basins. Gig Sanit 30:8-15. 711605.
Gustafson, DL; Coulson, AL; Feng, L; et al. (1998) Use of a medium-term liver focus bioassay
to assess the hepatocarcinogenicity of 1,2,4,5-tetrachlorobenzene and 1,4-dichlorobenzene.
Cancer Lett 129(1)39-44. 677348.
Gustafson, DL; Long, ME; Thomas, RS; et al. (2000) Comparative hepatocarcinogenicity of
hexachlorobenzene, pentachlorobenzene, 1,2,4,5-tetrachlorobenzene, and 1,4-dichlorobenzene:
application of a medium-term liver focus bioassay and molecular and cellular indices. Toxicol
Sci 53(2):245-252. 652769.
Haworth, S.; Lawlor, T.; Mortelmans, K.; Speck, W.; Zeiger, E. (1983) Salmonella
mutagenicity test results for 250 chemicals. Environ Mutagen 5:3-142. Available online at
http://dx.doi.ore/10.1002/em.2860050703. 028947.
IARC (International Agency for Research on Cancer). (2013) Monographs on the evaluation of
carcinogenic risks to humans. Lyon, France: IARC. Available online at
http://monoeraphs.iarc.fr/ENG/Monoeraphs/voH03/monol03-B02-B03.pdf. 1770074
62
1,2,4,5-Tetrachlorobenzene

-------
FINAL
9-27-2013
IPCS (International Programme on Chemical Safety). (1991) Chlorobenzenes other than
hexachlorobenzene (Report No. Environmental Health Criteria 128). World Health
Organization, Geneva, Switzerland. Available online at
http://www.inchem.ore/documents/ehc/ehc/ehcl28.htm. 081628.
Kacew, S; Ruddick, JA; Parulekar, M; et al. (1984) A teratological evaluation and analysis of
fetal tissue levels following administration of tetrachlorobenzene isomers to the rat. Teratology
29( 1 ):21-27. Available online at http://dx.doi.ore/10.1002/tera.1420290104. 677354.
Kiraly, J; Szentesi, I; Ruzicska, M; Czeize, A. (1979) Chromosome studies in workers
producing organophosphate insecticides. Arch Environ Contam Toxicol 8(3): 309-319.
Available online at http://dx.doi.ore/10.1007/BF01056247. 065914.
Kitchin, KT; Ebron, MT. (1983) Maternal hepatic effects of 1,2,4,5-tetrachlorobenzene in the
rat. Environ Res 32:134-144. Available online at http://dx.doi.ore/10.1016/0013-
9351(83)90200-1. 677357.
Loveday, KS; Anderson, BE; Resnick, MA; et al. (1990) Chromosome aberration and sister
chromatid exchange tests in Chinese hamster ovary cells in vitro. V: Results with 46 chemicals.
EnvironMolMutagen 16(4):272-303. Available online at
http://dx.doi.ore/10.1002/em.2850160409. 106324.
NIOSH (National Institute for Occupational Safety and Health). (2010) NIOSH pocket guide to
chemical hazards. Index of chemical abstracts service registry numbers (CAS No.). Center for
Disease Control and Prevention, U.S. Department of Health, Education and Welfare,
Atlanta, GA. Available online at http://www.cdc.eov/niosh/npe/npedcas.html. 1788713
NLM (National Library of Medicine). (2011) Hazardous Substances Data Bank (HSDB).
National Institutes of Health, Bethesda, MD. Available online at http://toxnet.nlm.nih.eov.
Accessed on February 14, 2011. 783990.
NTP (National Toxicology Program). (1991a,b,c,d) Toxicity studies of
1,2,4,5-tetrachlorobenzene in F344 rats and B6C3F1 mice (feed studies). U.S. Department of
Health and Human Services, Publich Health Service, Research Triangle Park, NC; NIH 91-3126.
Available online at http://ntp.niehs.nih.eov/ntp/htdocs/ST rpts/tox007.pdf. 677360.
NTP (National Toxicology Program). (1991e) Final report on the reproductive toxicity of
1,2,4,5-tetrachlorobenzene (CAS no. 95-94-3) in CD-I Swiss mice. Environmental Health
Research and Testing, National Toxicology Program, Lexington, KY. Available online at
http://www.ntis.gov/search/product.aspx?ABBR=PB92128388. 666710.
NTP (National Toxicology Program). (2011) Report on carcinogens, 12th edition.
U.S. Department of Health and Human Services, Public Health Service, National Institutes of
Health, Research Triangle Park, NC. Available online at
http://ntp.niehs.nih.eov/ntp/roc/twelfth/rocl2.pdf. 737606
63
1,2,4,5-Tetrachlorobenzene

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FINAL
9-27-2013
OSHA (Occupational Safety and Health Administration). (2006) Table Z-l limits for air
contaminants: occupational safety and health standards, subpart Z, toxic and hazardous
substances. U.S. Department of Labor, Washington, DC; OSHA Standard 1910.1000. Available
online at
http://www.osha.gov/pls/oshaweb/owadisp.show document?!) table=STANDARDS&p id=999
2. 670067
OSHA (Occupational Safety and Health Administration). (2011) Air contaminants:
occupational safety and health standards for shipyard employment, subpart Z, toxic and
hazardous substances. U.S. Department of Labor, Washington, DC; OSHA Standard 1915.1000.
Available online at
http://www.osha.gov/pls/oshaweb/owadisp.show document?p table=STANDARDS&p id=102
86.
Ou, YC; Conolly, RB; Thomas, RS; et al. (2003) Stochastic simulation of hepatic preneoplastic
foci development for four chlorobenzene congeners in a medium-term bioassay. Toxicol Sci
73:301-314. Available online at http://dx.doi.org/10.1093/toxsci/kfg078. 660380.
Schwartz, H; Chu, I; Villeneuve, DC; Benoit, FM. (1987) Metabolism of 1, 2, 3, 4-, 1, 2, 3, 5-,
and 1, 2, 4, 5-tetrachlorobenzene in the squirrel monkey. J Toxicol Environ Health
22(3):341-350. 677364.
Shelby, MD; Witt, KL. (1995) Comparison of results from mouse bone marrow chromosome
aberration and micronucleus tests. EnvironMolMutagen 25(4):302-313. Available online at
http://dx.doi.org/10.1002/em.28502504Q7. 624921.
Tyl, RW; Neeper-Bradley, TL. (1989) Two-generation reproduction study of
1,2,4,5-tetrachlorobenzene administered in the diet to Sprague-Dawley rats with letter dated
4/21/89 from Chemical Manufacturers Association. Bushy Run Research Center, Export, PA;
NTIS No. OTS0523029. Submitted under TSCA Section 407029. 677368.
U.S. EPA (Environmental Protection Agency). (1988) Recommendations for and
documentation of biological values for use in risk assessment. Environmental Criteria and
Assessment Office, Cincinnati, OH; EPA/600/6-87/008. Available online at
http://cfpub.epa.gov/ncea/cfm/recordisplav.cfm?deid=34855#Download. 064560
U.S. EPA (Environmental Protection Agency). (1991) Integrated Risk Information System
(IRIS) 1,2,4,5-Tetrachlorobenzene. Office of Research and Development, National Center for
Environmental Assessment, Washington, DC. Available online at
http://www.epa.gov/iris/subst/0107.htm.
U.S. EPA (Environmental Protection Agency). (1994) Chemical assessments and related
activities (CARA). Office of Health and Environmental Assessment, Washington, DC;
EPA/600/R-94/904. Available online at
http://nepis.epa. gov/Exe/ZyPURL.cgi?Dockev=6000 lG8L.txt. 596444.
64
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FINAL
9-27-2013
U.S. EPA (Environmental Protection Agency). (2002) A review of the reference dose and
reference concentration processes. Final report. Risk Assessment Forum, Washington, DC;
EPA/630/P-02/002F. Available online at http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf.
088824.
U.S. EPA (Environmental Protection Agency). (2011) Health effects assessment summary
tables (HEAST). Prepared by the Office of Research and Development, National Center for
Environmental Assessment, Cincinnati OH for the Office of Emergency and Remedial Response,
Washington, DC. Available online at http://epa-heast.ornl.gov/. 1577552
U.S. EPA (Environmental Protection Agency). (2011) Recommended use of body weight3 4 as
the default method in derivation of the oral reference dose. Office of the Science Advisor, Risk
Assessment Forum, Washington, DC; EPA/1000/R-11/0001. Available online at
http://www.epa.gov/raf/publications/pdfs/recommended-use-of-bw34.pdf. 752972.
U.S. EPA (Environmental Protection Agency). (2012) 2012 Edition of the drinking water
standards and health advisories. Office of Water, Washington, DC; EPA 822-S-12-001.
Available online at http://water.epa.gov/action/advisories/drinking/upload/dwstandards2012.pdf.
1936016.
Union Carbide Corporation. (1992) Initial submission: 2-generation reproduction study of
1,2,4,5-tetrachlorobenzene administered in the diet to Sprague-Dawley rats with cover letter
dated 082792. Bushy Run Research Center, Export, PA; 920009343. Available online at
http://www.ntis.gov/search/product.aspx?ABBR=OTSQ571095. 677325.
WHO (World Health Organization). (1991) Chlorobenzenes other than hexachlorobenzene.
Environmental health criteria 128. Available online at
http://www.inchem.org/documents/ehc/ehc/ehcl28.htm. Accessed on February 14, 2011.
081628.
65
1,2,4,5-Tetrachlorobenzene

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