SEPA
EPA/690/R-19/003 F | September 2019 | FINAL
United States
Environmental Protection
Agency
Provisional Peer-Reviewed Toxicity Values for
2-Nitropropane
(CASRN 79-46-9)
U.S. EPA Office of Research and Development
Center for Public Health and Environmental Assessment

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A	United Statts
^•&KIII,I^U Environmental Protection
X#L-I #HL Agency
EPA/690/R-19/003F
FINAL
September 2019
Provisional Peer-Reviewed Toxicity Values for
2-Nitropropane
(CASRN 79-46-9)
Center for Public Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
ii
2-Nitropropane

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AUTHORS, CONTRIBUTORS, AND REVIEWERS
CHEMICAL MANAGERS
Jon Reid, PhD, DABT
Center for Public Health and Environmental Assessment, Cincinnati, OH
J. Phillip Kaiser, PhD, DABT
Center for Public Health and Environmental Assessment, Cincinnati, OH
CONTRIBUTOR
Scott C. Wesselkamper, PhD
Center for Public Health and Environmental Assessment, Cincinnati, OH
DRAFT DOCUMENT PREPARED BY
SRC, Inc.
7502 Round Pond Road
North Syracuse, NY 13212
PRIMARY INTERNAL REVIEWERS
J. Allen Davis, MSPH
Center for Public Health and Environmental Assessment, Cincinnati, OH
Dan D. Petersen, PhD, DABT
Center for Public Health and Environmental Assessment, Cincinnati, OH
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 Center for Public Health and Environmental Assessment.
To the memory of Dr. Jon BriceReid (1937-2019)
in
2-Nitropropane

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TABLE OF CONTENTS
COMMONLY USED ABBREVIATIONS AND ACRONYMS	v
BACKGROUND	1
DISCLAIMERS	1
QUESTIONS REGARDING PPRTVs	1
INTRODUCTION	2
REVIEW OF POTENTIALLY RELEVANT DATA (NONCANCER AND CANCER)	6
HUMAN STUDIES	14
ANIMAL STUDIES	16
Oral Exposures	16
Inhalation Exposures	19
OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)	29
Genotoxicity Studies	29
Supporting Human Toxicity Studies	48
Supporting Animal Toxicity Studies	49
Absorption, Distribution, Metabolism, and Elimination Studies	60
Mode-of-Action/Mechanistic Studies	61
DERIVATION 01 PROVISIONAL VALUES	63
DERIVATION 01 ORAL REFERENCE DOSES	63
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS	64
Derivation of Subchronic Provisional Reference Concentration	64
Derivation of Chronic Provisional Reference Concentration	68
CANCER WEIGHT-OF-EVIDENCE DESCRIPTOR	68
MODE-OF -ACTION DISCUSSION	69
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES	71
Derivation of Provisional Oral Slope Factor	71
Derivation of Provisional Inhalation Unit Risk	71
APPENDIX A. SCREENING PROVISIONAL VALUES	72
APPENDIX B. DATA TABLES	78
APPENDIX C. BENCHMARK DOSE MODELING RESULTS	117
APPENDIX D. REFERENCES	139
iv
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COMMONLY USED ABBREVIATIONS AND ACRONYMS1
a2u-g
alpha 2u-globulin
MN
micronuclei
ACGM
American Conference of Governmental
MNPCE
micronucleated polychromatic

Industrial Hygienists

erythrocyte
AIC
Akaike's information criterion
MOA
mode of action
ALD
approximate lethal dosage
MTD
maximum tolerated dose
ALT
alanine aminotransferase
NAG
Y-acctyl-(}-D-glucosaminidasc
AR
androgen receptor
NCI
National Cancer Institute
AST
aspartate aminotransferase
NOAEL
no-observed-adverse-effect level
atm
atmosphere
NIP
National Toxicology Program
ATSDR
Agency for Toxic Substances and
NZW
New Zealand White (rabbit breed)

Disease Registry
OCT
ornithine carbamoyl transferase
BMD
benchmark dose
ORD
Office of Research and Development
BMDL
benchmark dose lower confidence limit
PBPK
physiologically based pharmacokinetic
BMDS
Benchmark Dose Software
PCNA
proliferating cell nuclear antigen
BMR
benchmark response
PND
postnatal day
BUN
blood urea nitrogen
POD
point of departure
BW
body weight
PODadj
duration-adjusted POD
CA
chromosomal aberration
QSAR
quantitative structure-activity
CAS
Chemical Abstracts Service

relationship
CASRN
Chemical Abstracts Service registry
RBC
red blood cell

number
RDS
replicative DNA synthesis
CBI
covalent binding index
RfC
inhalation reference concentration
CHO
Chinese hamster ovary (cell line cells)
RID
oral reference dose
CL
confidence limit
RGDR
regional gas dose ratio
CNS
central nervous system
RNA
ribonucleic acid
CPHEA
Center for Public Health and
SAR
structure activity relationship

Environmental Assessment
SCE
sister chromatid exchange
CPN
chronic progressive nephropathy
SD
standard deviation
CYP450
cytochrome P450
SDH
sorbitol dehydrogenase
DAF
dosimetric adjustment factor
SE
standard error
DEN
diethylnitrosamine
SGOT
serum glutamic oxaloacetic
DMSO
dimethylsulfoxide

transaminase, also known as AST
DNA
deoxyribonucleic acid
SGPT
serum glutamic pyruvic transaminase,
EPA
Environmental Protection Agency

also known as ALT
ER
estrogen receptor
SSD
systemic scleroderma
FDA
Food and Drug Administration
TCA
trichloroacetic acid
FEVi
forced expiratory volume of 1 second
TCE
trichloroethylene
GD
gestation day
TWA
time-weighted average
GDH
glutamate dehydrogenase
UF
uncertainty factor
GGT
y-glutamyl transferase
UFa
interspecies uncertainty factor
GSH
glutathione
UFC
composite uncertainty factor
GST
glutathione-S -transferase
UFd
database uncertainty factor
Hb/g-A
animal blood-gas partition coefficient
UFh
intraspecies uncertainty factor
Hb/g-H
human blood-gas partition coefficient
UFl
LOAEL-to-NOAEL uncertainty factor
HEC
human equivalent concentration
UFs
subchronic-to-chronic uncertainty factor
HED
human equivalent dose
U.S.
United States of America
i.p.
intraperitoneal
WBC
white blood cell
IRIS
Integrated Risk Information System


ivf
in vitro fertilization


LC50
median lethal concentration


LD50
median lethal dose


LOAEL
lowest-observed-adverse-effect level


Abbreviations and acronyms not listed on this page are defined upon first use in the PPRTV document.
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PROVISIONAL PEER-REVIEWED TOXICITY VALUES FOR
2-NITROPROPANE (CASRN 79-46-9)
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 at least two Center for Public
Health and Environmental Assessment (CPHEA) scientists and an independent external peer
review by at least 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.
Currently available PPRTV assessments can be accessed on the U.S. EPA's PPRTV
website at https://www.epa.gov/pprtv. PPRTV assessments are eligible to be updated on a
5-year cycle to incorporate new data or methodologies that might impact the toxicity values or
characterization of potential for adverse human-health effects and are revised as appropriate.
Questions regarding nomination of chemicals for update can be sent to the appropriate
U.S. Environmental Protection Agency (EPA) Superfund and Technology Liaison
(https://www.epa.gov/research/fact-sheets-regional-science).
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. 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.
This document has been reviewed in accordance with U.S. EPA policy and approved for
publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
QUESTIONS REGARDING PPRTVS
Questions regarding the content of this PPRTV assessment should be directed to the
U.S. EPA Office of Research and Development's (ORD's) CPHEA.
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INTRODUCTION
2-Nitropropane, C ASRN 79-46-9, belongs to the nitroalkanes class of compounds. It is
used mainly as an industrial solvent in inks, paints, adhesives, varnishes, polymers, and synthetic
material or as a chemical intermediate (O'Neil. 2013; Markofskv. 2012). 2-Nitropropane is listed
on the U.S. Environmental Protection Agency (U.S. EPA) Toxic Substances Control Act (TSCA)
public inventory (U.S. EPA. 2018b). is registered with Europe's Registration, Evaluation,
Authorisation and Restriction of Chemicals (REACH) program (ECHA. 2018). and was assessed
under the U.S. EPA High Production Volume (HPV)/Organisation for Economic Co-operation
and Development (OECD) Screening Information Data Set (SIDS) Programme (OECD. 2010).
Commercial production of 2-nitropropane is achieved by high-temperature vapor-phase
nitration of propane (Markofskv. 2012). The process uses nitric acid as the nitrating agent
through a NO2 radical reaction at 350-450°C and 0.8-1.2 MPa. The reaction product from this
process is a nitroalkane mixture, rich in nitropropanes. It is washed, dried, and purified by
distillation to obtain individual nitroalkanes.
The empirical formula for 2-nitropropane is C3H7NO2, and its structure is shown in
Figure 1. Table 1 summarizes the physicochemical properties of 2-nitropropane.
2-Nitropropane is a colorless, oily liquid at room temperature. Reported vapor pressures for
2-nitropropane indicate that it will exist almost entirely as a vapor at atmospheric temperature
and pressure. The estimated half-life of vapor-phase 2-nitropropane in air by reaction with
photochemically produced hydroxyl radicals is 95 days. The vapor pressure and calculated
Henry's law constant for 2-nitropropane indicate that it may volatilize from either dry or moist
surfaces. The high water solubility and low soil adsorption coefficients for 2-nitropropane
indicate that it may leach to groundwater or undergo runoff after a rain event. Based on
screening tests, 2-nitropropane may undergo limited biodegradation in the environment. Under
aqueous conditions, 2-nitropropane may exist partially in the anion form based on the measured
pKa of 7.68 (HSDB. 2006). The rate of hydrolysis of 2-nitropropane is negligible (U.S. EPA
2011c).
O	N +
W
o
Figure 1. 2-Nitropropane (CASRN 79-46-9) Structure
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Table 1. Physicochemical Properties of 2-Nitropropane (CASRN 79-46-9)
Property (unit)
Value
Physical state
Liquid
Boiling point (°C)
120a
Melting point (°C)
-92. la
Density (g/cm3)
0.9903
Vapor pressure (mm Hg)
17.2a
pH (unitless)
6.2, 0.01 Minwaterat25°C°
pKa (unitless)
7.68b
Solubility in water (mol/L)
0.208a
Octanol-water partition constant (log K,,,.-)
1.14a
Henry's law constant (atm-m3/mol)
4.77 x 10 " (predicted average)
Soil adsorption coefficient KoC (L/kg)
0.11 (Texas sandy silt loam soil)b,
3.8 (Mississippi sandy loam soil)b
Atmospheric OH rate constant (cm3/molecule-sec at 25 °C)
2.60 x 10-13b
Atmospheric half-life (d)
95 (calculated based on its measured OH rate
constant)13
Relative vapor density (air =1)
3.06b
Molecular weight (g/mol)
89.0943
Flash point (°C)
26.0a
aData were extracted from the U.S. EPA CompTox Chemicals Dashboard (2-Nitropropane, CASRN 79-46-9.
https://comptox.epa.gov/dashboard/DTXSID6020981. Accessed 06 May 2019). All values are experimental
averages unless otherwise specified.
bHSD6 (2006) unless otherwise specified; all values are measured unless noted otherwise.
cMarkofskv (2012).
A summary of available toxicity values for 2-nitropropane from U.S. EPA and other
agencies/organizations is provided in Table 2.
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Table 2. Summary of Available Toxicity Values for 2-Nitropropane (CASRN 79-46-9)
Source (parameter)3'b
Value (applicability)
Notes
Reference
Noncancer
IRIS (RfC)
0.02 mg/m3
Based on liver focal vacuolization
and nodules in a chronic-duration
inhalation study in rats.
U.S. EPA (2002a)
HEAST (sRfC)
0.02 mg/m3
The chronic inhalation RfC was
adopted as the subchronic inhalation
RfC. Based on liver lesions in a
chronic-duration, intermittent,
inhalation exposure study in rats.
U.S. EPA (2011a)

DWSHA
NV
NA
U.S. EPA (2012a)
ATSDR
NV
NA
ATSDR (2018)
IPCS
NV
NA
IPCS (2018)
CalEPA
NV
NA
CalEPA (2016);
CalEPA (2018a):
CalEPA (2018b)
ACGIH (TLV-TWA)
10 ppm
Based on liver damage.
ACGIH (2016)
OSHA (PEL-TWA)
25 ppm (91 mg/m3)
8-hr TWA for general industry,
construction, and shipyard
employment.
OSHA (2017a):
OSHA (2017b):
OSHA (2017c)
NIOSH (IDLH)
100 ppm
Based on acute inhalation toxicity
data in animals. This may be a
conservative value due to the lack of
relevant acute toxicity data for
workers exposed to concentrations
>45 ppm
NIOSH (1994)
Cancer
IRIS
NV
NA
U.S. EPA (2018a)
HEAST (IUR)
0.0027 (ng/m3)-1
Based on liver tumors in a
chronic-duration, intermittent,
inhalation exposure study in rats.
U.S. EPA (2011a):
U.S. EPA (1985)
HEAST/HEEP (ISF)
9.4 (mg/kg/d) 1
CAG (WOE)
Group B2: probably
carcinogenic to humans
Based on sufficient evidence from
animal studies and inadequate
evidence from human studies.
U.S. EPA (1988a)
DWSHA
NV
NA
U.S. EPA (2012a)
NTP (WOE)
Reasonably anticipated to
be a human carcinogen
Based on sufficient evidence of
carcinogenicity from studies in
experimental animals.
NTP (2016)
IARC (WOE)
Group 2B: possibly
carcinogenic to humans
Based on inadequate evidence for
carcinogenicity in humans and
sufficient evidence in experimental
animals.
IARC (1999):
IARC (2018)
CalEPA (WOE)
Listed as causing cancer
under Proposition 65
NA
CalEPA (2011):
CalEPA (2018a):
CalEPA (2018b)
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Table 2. Summary of Available Toxicity Values for 2-Nitropropane (CASRN 79-46-9)
Source (parameter)3'b
Value (applicability)
Notes
Reference
ACGIH (WOE)
A3: confirmed animal
carcinogen with
unknown relevance to
humans
NA
ACGIH (2017)
NIOSH (WOE)
Potential occupational
carcinogen
NA
NIOSH (2016)
aSources: ACGIH = American Conference of Governmental Industrial Hygienists; ATSDR = Agency for Toxic
Substances and Disease Registry; CAG = Carcinogen Assessment Group; CalEPA = California Environmental
Protection Agency; DWSHA = Drinking Water Standards and Health Advisories; HEAST = Health Effects
Assessment Summary Tables; HEEP = Health and Environmental Effects Profile; IARC = International Agency
for Research on Cancer; IPCS = International Programme on Chemical Safety; IRIS = Integrated Risk Information
System; NIOSH = National Institute for Occupational Safety and Health; NTP = National Toxicology Program;
OSHA= Occupational Safety and Health Administration.
Parameters: IDLH = immediately dangerous to life or health concentrations; ISF = inhalation slope factor;
IUR = inhalation unit risk; PEL = permissible exposure level; RfC = reference concentration; sRfC = subchronic
reference concentration; TLV = threshold limit value; TWA = time-weighted average; WOE = weight of evidence.
NA = not applicable; NV = not available.
Non-date-limited literature searches were conducted in October 2017 and updated in
September 2018 for studies relevant to the derivation of provisional toxicity values for
2-nitropropane (CASRN 79-46-9). Searches were conducted using U.S. EPA's Health and
Environmental Research Online (HERO) database of scientific literature. HERO searches the
following databases: PubMed, TOXLINE (including TSCATS1), and Web of Science. The
following databases were searched outside of HERO for health-related values: American
Conference of Governmental Industrial Hygienists (ACGIH), Agency for Toxic Substances and
Disease Registry (ATSDR), California Environmental Protection Agency (CalEPA), Defense
Technical Information Center (DTIC), European Centre for Ecotoxicology and Toxicology of
Chemicals (ECETOC), European Chemicals Agency (ECHA), U.S. EPA Chemical Data Access
Tool (CDAT), U.S. EPA ChemView, U.S. EPA Health Effects Assessment Summary Tables
(HEAST), U.S. EPA Integrated Risk Information System (IRIS), U.S. EPA Office of Water
(OW), International Agency for Research on Cancer (IARC), Japan Existing Chemical Data
Base (JECDB), National Institute for Occupational Safety and Health (NIOSH), National
Pesticide Information Retrieval System (NPIRS), National Toxicology Program (NTP), OECD
Existing Chemicals Database, OECD SIDS High Production Volume Chemicals via
International Programme on Chemical Safety (IPCS) INCHEM, Occupational Safety and Health
Administration (OSHA), and World Health Organization (WHO).
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REVIEW OF POTENTIALLY RELEVANT DATA
(NONCANCER AND CANCER)
Tables 3 A and 3B provide overviews of the relevant noncancer and cancer databases,
respectively, for 2-nitropropane, and include all potentially relevant repeat dose short-term-,
subchronic-, and chronic-duration studies, as well as reproductive and developmental toxicity
studies. Principal studies are identified in bold. The phrase "statistical significance," used
throughout the document, indicates ap-value of < 0.05 unless otherwise specified.
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Table 3A. Summary of Potentially Relevant Noncancer Data for 2-Nitropropane (CASRN 79-46-9)
Category"
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Human
In an unpublished retrospective mortality study, no evidence of increased mortality or cancer mortality (when evaluated as observed/expected deaths) was
observed in male or female workers exposed to 2-nitropropane at a plant in Louisiana (Miller and Temple. 1980). These results were further confirmed in a
follow-up mortality study usins the same cohort (Parekh and Wilbur. 1982). In an occupational health survey, no increases in effects in the pulmonary, hepatic,
renal, cardiovascular, hematological, or inteeumentarv systems were observed in workers exposed to 2-nitropropane at an industrial food plant (Crawford et al.
1985; TOMA, 1980). Case reports of acute hepatic failure in workers exposed to hieh concentrations of 2-nitropropane are discussed in the "Other Data"
section below.
Animal
1. Oral (mg/kg-d)
Short-term
5 M, Crl:CD (SD), rat, gavage in
water, 14 or 28 d
Reported doses: 0,5,20, or
40 mg/kg-d
0,5,20,40
Increased relative liver weight and
minimal to mild hepatocyte hypertrophy
at 28 d. At the high dose, these changes
were increased and accompanied by
additional gross and microscopic lesions
and serum chemistry changes indicative
of hepatic effects.
5
20
Kawakami et al.
PR, PS
(2015)
(only clinical signs,
body weight, and
hepatic endpoints
were evaluated)
Short-term
4 M, F344, rat, gavage in corn oil,
1,3,7, 14, or 28 d
Reported doses: 0 or 40 mg/kg-d
0, 40
Increased absolute liver weight and
glycogen accumulation in hepatocytes at
28 d.
NDr
40
Nakavama et al.
(2006)
(only mortality,
body weight, and
hepatic endpoints
were evaluated)
PR
Short-term
5 M, F344, rat, gavage in distilled
water containing 0.1% Tween 20,
2 wk (dosed a total of six times)
Reported doses: 0, 60, or 110
(time-weighted average) mg/kg-d
0, 26, 47.1
Mild hepatic lesions (hepatocyte swelling),
decreased serum triglycerides and liver
glycogen content, increased markers of
oxidative stress, and increased cell
proliferation in liver. At the high dose,
liver effects were increased and included
severe swelling of hepatocytes,
degenerative changes, and single-cell
necrosis.
NDr
26
Sai et al. (1998)
(only hepatic
endpoints were
evaluated)
PR
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Table 3A. Summary of Potentially Relevant Noncancer Data for 2-Nitropropane (CASRN 79-46-9)
Category"
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Short-term
8-13 M, Wistar, rat, oral in canola
oil, 3 d/wk, 2 wk
Reported doses: 0 or 120 mg/kg-d
0, 51.4
Elevated serum ALT, AST, LDH, and urea;
decreased hepatic catalase activity.
NDr
51.4
Wilhelm et al.
(2009)
(only hepatic and
renal endpoints
were evaluated)
PR
Chronic
22-29 M, S-D, rat, gavage in
Emulphor EL-620, 3 d/wk, 16 wk
Reported doses: 0 or 90 mg/kg-d
0, 39
Death of "several" treated rats during the
exposure phase of the study and
"significantly lower" body weights
throughout the study (no further details
reported).
NDr
39 (FEL)
Fialaetal. (1987b)
(data reporting was
limited)
PR
2. Inhalation (mg/m3)
Sub chronic-Duration Studies
Subchronic
10 M/10 F, LE, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 2 mo
Reported nominal concentrations:
0 or 200 ppm
0, 129
Hepatocellular vacuolization in the liver of
male rats.
NDr
129
Coulston et al.
(1978)
NPR
Chronic-Duration Studies with Interim Sacrifices
Short-term
10 M, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 10 d
Reported analytical
concentrations: 0, 27, or 207 ppm
0, 20, 157
Decreased body weight, elevated relative
liver weight, elevated serum ALT, and
increased hepatic pericholangitis.
20
157
Lewis et al. (1979);
Ulrich et al. (1977)
(interim sacrifice)
PR
Subchronic
10 M, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 1 or
3 mo
Reported analytical
concentrations: 0,27, or
207 ppm
0, 20,157
Increased absolute liver weight.
Decreased body weight, as well as
increased relative liver weight, serum
ALT, and non-neoplastic liver lesions
(focal hepatocyte hypertrophy, focal
hepatocyte hyperplasia, and basophilic
foci) were observed at 157 mg/m3.
NDr
20
Lewis et al. (1979);
PR, PS
Ulrich et al. (1977)
(interim sacrifices)
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Table 3A. Summary of Potentially Relevant Noncancer Data for 2-Nitropropane (CASRN 79-46-9)
Category"
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Chronic
10 M, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 6 mo
Reported analytical
concentrations: 0, 27, or 207 ppm
0, 20, 157
Decreased body weight, elevated serum
ALT, and elevated absolute and relative
liver weights. Elevated absolute and
relative lung weights and slight edema
were also reported (HEC =581 mg/m3 for
pulmonary effects).
20
157
Lewis et al. (1979);
Ulrichetal. (1977)
PR
Short-term
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 10 d
Reported analytical
concentrations: 0 or 196 ppm
0, 127
Elevated serum ALT and microscopic liver
changes, including single cell necrosis,
basophilic hepatocytes, mitotic cells, and
bile duct proliferation, in males.
NDr
127
Coulston et al.
(1978)
(interim sacrifice)
NPR
Subchronic
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 1 or
3 mo
Reported analytical
concentrations: 0 or 196 ppm
0, 127
Decreased body weight in males, elevated
relative liver weights in males and females,
increased serum ALT in males, and
microscopic liver changes in males.
NDr
127
Coulston et al.
(1978)
(interim sacrifices)
NPR
Chronic
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 6 mo
Reported analytical
concentrations: 0 or 196 ppm
0, 127
Elevated relative liver weights in males and
females, increased serum ALT and AST in
males, and microscopic liver changes in
males and females.
NDr
127
Coulston et al.
(1978)
NPR
Subchronic
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 1 or 3
mo
Reported analytical
concentrations: 0 or 25.1 ppm
0, 16.2
No adverse effects.
16.2
NDr
Griffin et al. (1981);
Griffin et al. (1980)
(interim sacrifices;
histological data
combined for main
study group plus
interim sacrifices
and recovery
groups)
PR
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Table 3A. Summary of Potentially Relevant Noncancer Data for 2-Nitropropane (CASRN 79-46-9)
Category"
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Chronic
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 6-22 mo
Reported analytical
concentrations: 0 or 25.1 ppm
0, 16.2
Increased absolute and relative liver weight
in males; increased incidences of focal
vacuolization of hepatocytes and
hepatocellular nodules in the liver of male
rats; liver congestion in male and female
rats.
NDr
16.2
Griffin et al. (1981);
Griffin et al. (1980)
(histological data
combined for main
study group plus
interim sacrifices
and recovery
groups)
PR,
IRIS
Subchronic
10 M/10 F, S-D, rat, whole-body
exposure, 7 hr/d, 5 d/wk, 1 or
3 mo
Reported analytical
concentrations: 0 or 100 ppm
0, 65.0
Increased absolute and relative liver
weights at 3 mo in males.
NDr
65.0
Griffin et al. (1979)
(interim sacrifices;
histopathology not
reported)
NPR
Chronic
95-105 M/95-105 F, S-D, rat,
whole-body exposure, 7 hr/d,
5 d/wk, 6-18 mo
Reported analytical
concentrations: 0 or 100 ppm
0, 65.0
Decreased body weights, renal
calcification, elevated ALT, and elevated
liver weights in male rats and hepatic
lesions in male and female rats.
NDr
65.0
Griffin et al. (1979)
NPR
Subchronic
5 M, NZW, rabbit, whole-body
exposure, 7 hr/d, 5 d/wk, 1 or
3 mo
Reported analytical
concentrations: 0, 27, or 207 ppm
0, 20, 157
No adverse effects.
157
NDr
Lewis et al. (1979);
Ulrich et al. (1977)
(interim sacrifices)
PR
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Table 3A. Summary of Potentially Relevant Noncancer Data for 2-Nitropropane (CASRN 79-46-9)
Category"
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Chronic
5 M, NZW, rabbit, whole-body
exposure, 7 hr/d, 5 d/wk, 6 mo
Reported analytical
concentrations: 0, 27, or 207 ppm
0, 20, 157
No adverse effects.
157
NDr
Lewis et al. (1979):
Ulrich et al. (1977)
PR
aDuration categories are defined as follows: Acute = exposure for <24 hours; short term = repeated exposure for 24 hours to <30 days; long term
(subchronic) = repeated exposure for >30 days <10% lifespan for humans (>30 days up to approximately 90 days in typically used laboratory animal species);
and chronic = repeated exposure for >10% lifespan for humans (>~90 days to 2 years in typically used laboratory animal species) (U.S. EPA. 2002b').
bDosimetry: Doses are presented as ADDs (mg/kg-day) for oral noncancer effects and as HECs (in mg/m3) for inhalation noncancer effects. Inhalation
exposures reported in ppm were converted to mg/m3 using the molecular weight of 89.09 mol/g and assuming standard temperature and air pressure for Lewis et
at (1979)/Ulrichet al. (1977). yielding a conversion factor of 1 ppm =3.6 mg/m3. For the other inhalation studies, conversion to mg/m3 was calculated using
the study author's conversions due to lower barometric pressure at the altitude of the testing facility (1,350 m), yielding a conversion factor of
1 ppm= 3.1 mg/m3. Once converted to mg/m3, it is current practice that HECs are calculated differently for systemic (ER) and pulmonary effects.
2-Nitropropane has characteristics of a highly reactive, Category 1 gas that often results in portal-of-entry effects in the PU region as well as less reactive
Category 3 gas for ER effects. As HEC equations for a Category 2 gas are currently unavailable, the HECs are calculated using both Category 1 and Category 3
gas equations. The HEC for ER effects is calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA (1994)
methodology: HECer = exposure level (mg/m3) x (hours/day exposed 24 hours) x (days/week exposed 7 days) x ratio of blood-gas partition coefficient
(animal:human), using a default coefficient of 1 since the rat blood-air partition coefficient of 183 [and rabbit value of 170; AFOSR (1992)1 is greater than the
human blood-air partition coefficient of 154 as indicated by Gargas et al. (1989). The HEC for pulmonary effects is calculated by treating 2-nitropropane as a
Category 1 gas and using the following equation from U.S. EPA (1994) methodology: HECpu = exposure level (mg/m3) x (hours/day
exposed ^ 24 hours) x (days/week exposed ^ 7 days) x RGDRPU, where RGDRPU is calculated as per U.S. EPA (1994) using default human VE and human and
animal respiratory tissue surface area values and animal Ve calculated from study (if available) or reference body weight values.
°Notes: IRIS = used by IRIS U.S. EPA (2002a): NPR = not peer reviewed; PR = peer reviewed; PS = principal study.
ADD = adjusted daily dose; ALT = alanine aminotransferase; AST = aspartate aminotransferase; ER = extrarespiratory; F = female(s); FEL = frank effect level;
HEC = human equivalent concentration; IRIS = Integrated Risk Information System; LDH = lactate dehydrogenase; LE = Long-Evans;
LOAEL = lowest-observed-adverse-effect level; M = male(s); ND = no data; NDr = not determined; NOAEL = no-observed-adverse-effect level; NZW = New
Zealand White; PU = pulmonary; RGDR = regional gas dose ratio; S-D = Sprague-Dawley; Ve = minute volume.
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Table 3B. Summary of Potentially Relevant Cancer Data for 2-Nitropropane (CASRN 79-46-9)
Category
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetry3
Critical Effects
Reference
(comments)
Notesb
Human
Carcinogenicity
(occupational)
1,334 M/147 F, workers employed in a
2-nitropropane production plant in
Louisiana from 1955-1981, average
duration of employment not reported
Generally, <91
No excess of cancer mortality in exposed
workers.
Parekh and Wilbur (1982):
Miller and Temole (1980)
NPR
Animal
1. Oral (mg/kg-d)
Carcinogenicity
22-29 M, S-D, rat, gavage in
Emulphor EL-620, 3 d/wk, 16 wk
Reported doses: 0 or 90 mg/kg-d
0, 9.8
Significant increase in the incidence of
hepatocarcinomas in exposed male rats
(22/22 treated vs. 0/29 control).
Fialaetal. (1987b)
PR
2. Inhalation (mg/m3)
Carcinogenicity
10 M, S-D, rat, 7 hr/d, 5 d/wk, 6 mo
Reported analytical concentrations:
0,27, or 207 ppm
0, 20,157
Significant increases in the incidences of
hepatocellular carcinomas and neoplastic
nodules at 157 mg/m3 (10/10, vs. 0/10 at
20 mg/m3 and 0/10 in controls).
Lewis et al. (1979);
PR, PS
Ulrich et al. (1977)

Carcinogenicity
10-20 M/10 F, S-D, rat, 7 hr/d,
5 d/wk, 6 mo
Reported analytical concentrations: 0
or 196 ppm
0, 127
Hepatic nodules with features indicative of
"malignant transformation" after 6 mo
exposure in males. Hepatic tumors with
metastasis in 9/10 males exposed for 6 mo
and observed for an additional 6 mo.
Coulston et al. (1978)
NPR
Carcinogenicity
125 M/125 F, S-D, rat, 7 hr/d, 5 d/wk,
up to 22 mo
Reported analytical concentrations: 0
or 25.1 ppm
0, 16.2
No evidence of carcinogenicity.
Griffin et al. (1981):
Griffin et al. (1980)
PR
Carcinogenicity
95-105 M/95-105 F, S-D, rat, 7 hr/d,
5 d/wk, 6-18 mo
Reported analytical concentrations: 0
or 100 ppm
0, 65.0
Significant increase in the incidence of
hepatocarcinomas in exposed male rats
sacrificed at 18 mo (7/23 vs. 0/63 controls).
No hepatocellular carcinomas in females.
Griffin et al. (1979)
NPR
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Table 3B. Summary of Potentially Relevant Cancer Data for 2-Nitropropane (CASRN 79-46-9)
Category
Number of Male/Female, Strain,
Species, Study Type, Study
Duration, Reported Doses
Dosimetry3
Critical Effects
Reference
(comments)
Notesb
Carcinogenicity
5	M, NZW, rabbit, 7 hr/d, 5 d/wk,
6	mo
Reported analytical concentrations: 0,
27, or 207 ppm
0, 20, 157
No evidence of carcinogenicity.
Lewis et al. (1979); Ulrich
et al. (1977)
PR
'Dosimetry: Oral exposures arc expressed as HEDs (mg/kg-day); HEDs are calculated using D AFs. as recommended by U.S. EPA (2011b): HED = ADD
(mg/kg-day) x DAF. The DAF is calculated as follows: DAF = (BWa ^ B Wh)1/4, where DAF = dosimetric adjustment factor, BWa = animal body weight, and
B Wh = human body weight, using study (if available) or reference body weight values for B Wa and the reference value of 70 kg for BWh. Inhalation exposure
units are expressed as HECs (mg/m3). Inhalation exposures reported in ppm were converted to mg/m3 using the molecular weight of 89.09 mol/g and assuming
standard temperature and air pressure for Lewis et al. (1979)/Ulrich et at (1977). yielding a conversion factor of 1 ppm =3.6 mg/m3. For the other inhalation
studies, conversion to mg/m3 was calculated using the study author's conversions due to lower barometric pressure at the altitude of the testing facility
(1,350 m), yielding a conversion factor of 1 ppm =3.1 mg/m3. Once converted to mg/m3, the HEC for ER effects was calculated by treating 2-nitropropane as a
Category 3 gas and using the following equation from U.S. EPA (1994) methodology: HECer = exposure level (mg/m3) x (hours/day
exposed 24 hours) x (days/week exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 since the rat
blood-air partition coefficient of 183 [and rabbit value of 170; AFOSR (1992)1 is greater than the human blood-air partition coefficient of 154 as indicated by
Gargas et at (1989).
bNotes: NPR = not peer reviewed; PR = peer reviewed; PS = principal study.
ADD = adjusted daily dose; BW = body weight; DAF = dosimetric adjustment factor; ER = extrarespiratory; F = female(s); HEC = human equivalent
concentration; HED = human equivalent dose; M = male(s); NZW = New Zealand White; S-D = Sprague-Dawley.
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HUMAN STUDIES
Parekh and Wilbur (1982); Miller and Temple (1980)
In an unpublished retrospective mortality study. Miller and Temple (1980) evaluated
mortality patterns in a cohort of 1,334 male workers and 147 female workers employed between
January 1955 and July 1977 at a plant in Louisiana that manufactured 2-nitropropane. Workers
were divided into three 2-nitropropane exposure groups based on job title: direct exposure
(n = 372; laboratory, research, production, warehouse), indirect exposure (// = 366; machine
shop, electric shop, general maintenance, instrument shop, shipping, engineering, technical
service, process development), and no exposure (n = 743; other workers, e.g., office staff).
Standard mortality ratios (SMRs) were calculated based on U.S. mortality rates.
Historical exposure data showed periodic exposure levels over the OSHA standard of
25 ppm (91 mg/m3) between 1962-1977; however, no formalized exposure data were recorded.
Levels from 580-1,640 ppm (2,110-5,980 mg/m3) were reported during the filling phase of the
drumming operation. Personal air sampling between January and June of 1977 found that
141/144 (97.9%) of the time-weighted air samples were 0.2-10 ppm (0.7-36 mg/m3), 1/144 was
10-25 ppm (36-91 mg/m3), and 2/144 were 25-100 ppm (91-364 mg/m3). The two samples in
the highest exposure bin were in proximity of a spill. It was not reported whether personal air
monitoring was conducted in the direct exposure group only or in the direct and indirect
exposure groups.
The study authors indicated that incidents of exposures above the OSHA standard of
91 mg/m3 coincided with drumming operators who reported occasional nausea and headache;
however, incidence data for these complaints were not reported. It is not clear whether these
complaints were ever made at exposures <91 mg/m3. No evidence of increased mortality or
cancer mortality (when evaluated as observed/expected deaths) was associated with exposure to
2-nitropropane (see Table B-l). Overall SMRs for white males, black males, and females for all
causes of mortality were 85, 67, and 279, respectively (no confidence intervals [CIs] were
reported). Similarly, SMRs for all cancer mortalities for white males, black males, and females
were 72, 67, and 500, respectively (no CIs were reported). While the female data suggested a
potential increase in mortality in this cohort, these findings were driven by four cases of cancer
at four different sites (buccal cavity, respiratory, breast, and "residual cancer") in this small
cohort of women. When broken down into exposure groups, three of four female cancer cases
were from the "unexposed" group, indicating that the observed findings are not related to
2-nitropropane exposure (see Table B-l).
Parekh and Wilbur (1982) conducted a follow-up mortality study on this cohort,
including workers employed through the end of 1981. The follow-up cohort comprised
1,390 male workers and 189 female workers, including 400 employees with direct exposure, 206
with indirect exposure, and 773 with no exposure. Findings in the follow-up were
comparable/similar to the initial study. Overall SMRs for white males, black males, and females
for all causes of mortality were 79, 58, and 183, respectively, and SMRs for all cancer mortalities
for white males, black males, and females were 70, 54, and 301, respectively (no CIs were
reported). As with the initial cohort, female findings were driven by the same four cases of
cancer, three of which were in the unexposed group.
Together, these data suggest that occupational exposure below the OSHA standard of
91 mg/m3 is not associated with increased mortality or cancer mortality, compared with the
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general population. However, these results should be interpreted with caution due to study
limitations, including small cohort sizes, inadequate exposure reporting per group, unreported
duration of exposure, and lack of control for confounding factors.
Crawford et al. (1985); TOMA (1980)
In an occupational health survey, employee health examinations were conducted in
18 workers with potential exposure to 2-nitropropane during solvent extraction of triglycerides in
an industrial food plant and 28 coworkers from the same facility that were not expected to have
exposure (primarily operating and maintenance personnel). Initial health exams were conducted
in 1979, with follow-up exams in 1982. Workers were 96% male, aged 45-64 years, and had
been working for the company for 16-35 years. Health examinations included self-reported
personal health, electrocardiogram, chest X-ray, pulmonary function tests, clinical chemistry,
hematology, urinalysis, and a physical exam by an occupational physician.
Air sampling was conducted in March, June, and August of 1981, with measurements at
specific locations (Area 1, Area 2, Area 3) throughout the plant where process operators
routinely monitored the process. Job descriptions for the different areas were not reported. In
addition, 2-5 personal air monitoring samples were measured at each evaluation. The study
authors did not indicate the job titles of individuals who were selected for personal air
monitoring or whether those individuals were in the "potentially exposed" group. During
"routine production," the mean air level of 2-nitropropane was 36 ± 10 ppm (130 ± 36 mg/m3) in
Area 1 (range 23-58 ppm [84-210 mg/m3]), 55 ± 23 ppm (200 ± 84 mg/m3) in Area 2
(range 29-100 ppm [110-364 mg/m3]), 56 ± 15 ppm (200 ± 55 mg/m3) in Area 3
(range 35-75 ppm [130-270 mg/m3]), and 2.3 ±2.1 ppm (8.4 ± 7.7 mg/m3) for personal air
monitoring (range 0-5.4 ppm [0-20 mg/m3]). When the "old way" of production (steam
blow-down) was used in August of 1981, the reported air levels were 130, 120, 120, and 15 ppm
(474, 437, 437, and 55 mg/m3) in Area 1, Area 2, Area 3, and personal monitoring, respectively.
This "old way" is no longer used in production, but the test was conducted to estimate potential
prior exposure levels.
Additional personal air samples were measured on five occasions, beginning in
November of 1981 and ending in May of 1983. Personal air samples were taken over at least
two operating shifts, with 2-4 samples/shift (5-8 samples/date). The study authors did not
indicate the job titles of individuals who were selected for personal air monitoring or whether
those individuals were in the "potentially exposed" group. Overall, the mean personal
monitoring level of 2-nitropropane was 12 ± 15 ppm (44 ± 55 mg/m3), with a range of 0-73 ppm
(0-270 mg/m3). The lowest mean level was reported in May of 1983 (0.9 ± 1.7 ppm
[3.3 ± 6.2 mg/m3]), and the highest mean level was reported in February of 1983 (24 ± 28 ppm
[87 ±102 mg/m3]). There was no discussion regarding the potential reason for the large
fluctuations in observed exposure levels.
When all workers in the cohort were grouped together, no increases in adverse health
effects in the pulmonary, hepatic, renal, cardiovascular, hematological, or integumentary systems
were observed, compared with national population rates. The study authors also reported no
significant differences between the 18 employees with potential exposure and the 28 coworkers
who were not expected to be exposed; however, the authors provided no data for these
comparisons.
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This study has numerous limitations that preclude clear conclusions regarding potential
health effects of occupational exposure to 2-nitropropane. A critical limitation is the inadequate
reporting of separate exposure and outcome data for the "exposed" versus the "unexposed"
group. Additional limitations include small sample size, lack of details on work environment or
personal protective equipment, lack of discussion regarding factors contributing to large
fluctuations in personal exposure levels, and lack of discussion of other potential routes of
exposure (e.g., dermal).
Case reports of acute hepatic failure in workers exposed to high concentrations of
2-nitropropane are discussed in the "Other Data" section below.
ANIMAL STUDIES
Oral Exposures
Short-Term-Duration Studies
Kawakami et al. (2015)
Male Crl:CD (SD) rats were administered 2-nitropropane (98.1% purity) at doses of 0, 5,
20, or 40 mg/kg-day via gavage in water daily for 14 or 28 days (5/group per time point)
(Kawakami et al.. 2015). Mortality, clinical signs, and body weight were monitored. Animals
were sacrificed 24 hours after the final dose. Blood was collected at sacrifice to determine serum
aspartate aminotransferase (AST), alanine transaminase (ALT), cholinesterase (ChE), and
y-glutamyl transferase (GGT). The livers were removed, weighed, and examined for
histopathological changes. Dose-response relationships were analyzed using Dunnett's test.
All animals survived until scheduled sacrifice, and no clinical signs of toxicity were
observed. Body weights were similar between control and exposed animals (see Table B-2).
The relative liver weight was significantly elevated by 14-24% after exposure to doses
>20 mg/kg-day for 28 days; no significant exposure-related (i.e., when compared to control
animals) changes were observed at 14 days of exposure (see Table B-2). Significant changes in
serum chemistry were observed at 40 mg/kg-day, including a 21% increase in AST at 14 days,
83 and 169% increases in ChE at 14 and 28 days, respectively, and 33 and 225% increases in
GGT at 14 and 28 days, respectively (see Table B-3). At necropsy, pale livers were observed at
40 mg/kg-day after 14 days and at >20 mg/kg-day after 28 days (see Table B-4).
Histopathological changes were only observed after exposure for 28 days, including
minimal-to-mild diffuse hepatocyte hypertrophy at >20 mg/kg-day and minimal basophilic foci
and anisokaryosis of hepatocytes at 40 mg/kg-day (see Table B-4).
A no-observed-adverse-effect level (NOAEL) of 5 mg/kg-day and a
lowest-observed-adverse-effect level (LOAEL) of 20 mg/kg-day are identified from this study
based on significantly elevated relative liver weight and hepatocyte hypertrophy after 28 days of
exposure. The liver was the only organ examined for pathology. At the high dose of
40 mg/kg-day, both relative liver weight and hepatocyte hypertrophy were increased and
accompanied by additional gross and microscopic lesions and serum chemistry changes
indicative of hepatic effects.
Nakavamaetal. (2006)
Male F344 rats were administered 2-nitropropane (>97% purity) at doses of 0 or
40 mg/kg-day via gavage in corn oil daily for 1,3,7, 14, or 28 days (4/group per time point).
Mortality and body weight were monitored. Animals were sacrificed 24 hours after the final
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dose. Blood was collected at sacrifice to determine serum AST, ALT, and alkaline phosphatase
(ALP). The livers were removed, weighed, and examined for histopathological changes. Body
weight, liver weight, and serum chemistry data were evaluated statistically using an unreported
method.
Only findings at 28 days were provided by the study authors. No mortalities were
reported. Body weights were comparable at 28 days between the exposed and control groups.
Absolute liver weights were significantly increased by 18% in exposed rats, compared with
control (see Table B-5); relative liver weights were not calculated. Serum liver enzyme levels
were comparable between exposed and control rats (see Table B-5).
The only dose administered (40 mg/kg-day) is identified as a LOAEL for this study based
on elevated absolute liver weight and glycogen accumulation in hepatocytes after 28 days of
exposure. No NOAEL is identified.
Saietal (1998)
Male F344 rats were administered 2-nitropropane (purity not reported) via gavage in
distilled water containing 0.1% Tween 20 over a 2-week period. Exposure groups (5/group)
included a vehicle control, a low-dose group (dosed a total of six times at 60 mg/kg-day), and a
high-dose group (dosed twice at 90 mg/kg-day and four times at 120 mg/kg-day; time-weighted
average [TWA] of 110 mg/kg-day). Adjusted daily doses (ADDs) to account for intermittent
exposure (6/14 days) are calculated to be 26 and 47.1 mg/kg-day for the low- and high-dose
groups, respectively. Additional groups were given green tea infusion for 1 week prior to
2-nitropropane and throughout 2-nitropropane exposure to evaluate potential protective effects of
antioxidants. To evaluate cell proliferation, rats were intraperitoneally injected with 20 mg/kg
5-bromo-2'-deoxyuridine (BrdU) twice daily for 2 days prior to terminal sacrifice and once
2 hours prior to sacrifice. Terminal sacrifice was 4 hours after the final 2-nitropropane
administration. At sacrifice, blood was collected to determine serum AST and triglyceride
levels. The liver was removed and divided into sections for biochemical analysis of
thiobarbituric acid reactive substances (TBARS), 8-hydroxydeoxyguanosine (8-OHdG), and
glycogen content; analysis of cell proliferation (BrdU staining); and histopathology. Statistical
analysis of continuous data sets was conducted using Student's Mest.
Significant changes noted in this study were increases in serum AST in the high-dose
group (1.4-fold), and dose-related decreases in serum triglycerides (-58 and —85%) and liver
glycogen (-45 and -62%) and increases in lipid peroxidation (1.6- and 3.4-fold as TBARS),
deoxyribonucleic acid (DNA) oxidation (1.8- and 2.9-fold as 8-OHdG) and cell proliferation
(2.5- and 5.7-fold as BrdU) in the liver in the low- and high-dose groups, respectively, relative to
controls. Histopathological changes in the livers of exposed animals included slight swelling of
hepatocytes without degeneration in the low-dose group and severe swelling of hepatocytes,
degenerative changes, and single cell necrosis in the high-dose group (incidence data not
reported by study authors). The study authors noted that green tea infusions inhibited
2-nitropropane hepatic toxicity.
A LOAEL of 26 mg/kg-day is identified in this study based on mild histopathological
changes in the liver accompanied by signs of oxidative stress and increased cell proliferation.
Liver effects were also increased at the high dose. No NOAEL is identified.
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Wilhelm et al (2009)
Male Wistar rats (8-13/group) were administered oral doses of 2-nitropropane (purity not
specified) at doses of 0 or 120 mg/kg-day in canola oil three days per week for 2 weeks. The
ADD to account for intermittent exposure (3 days/week) is calculated to be 51.4 mg/kg-day.
This experiment was conducted twice to evaluate whether administrating the antioxidants
diphenyl diselenide ([PhSe]2) or w-trifluoromethyl-diphenyl diselenide ([F3CPhSe]2) was
protective; the antioxidants were administered orally on alternating days with 2-nitropropane in
additional rat groups. The rats were sacrificed 36 hours after the final exposure. Blood was
collected for serum chemistry (AST, ALT, GGT, urea, creatinine). Liver and kidney samples
were homogenized for determining ascorbic acid levels and catalase activity. No additional
endpoints were evaluated. Statistical tests were conducted with a two-way analysis of variance
(ANOVA) followed by Duncan's multiple range test when appropriate.
Plasma ALT, AST, GGT, and urea levels were significantly elevated by up to 2.7-, 1.7-,
5-, and 1.4-fold, respectively, in exposed rats from both experiments, compared with respective
controls (see Table B-6). No exposure-related changes were observed in serum creatinine.
Hepatic catalase activity was significantly decreased by 39-57% in exposed rats from both
experiments, compared with respective controls (see Table B-6). Renal catalase activity and
renal and hepatic ascorbic acid levels was not altered in the liver of dosed rats. Treatment with
(PhSe)2 or (F3CPhSe)2 decreased or ameliorated observed hepatic effects associated with
exposure to 2-nitropropane.
The only administered dose (51.4 mg/kg-day) is identified as a LOAEL based on elevated
serum ALT, AST, GGT, and urea and decreased hepatic catalase activity, and no NOAEL is
identified.
Chronic-Duration/Carcinogenicity Studies
Fiala et al (1987b)
In a short communication, Fiala et al. (1987b) reported carcinogenic effects in male
Sprague-Dawley (S-D) rats administered 2-nitropropane (purity not reported) at doses of 0 or
1 mmol/kg-day (0 or 90 mg/kg-day) via gavage in Emulphor EL-620 vehicle 3 days/week for
16 weeks followed (in controls only) by 1 day/week for an additional 10 weeks. Due to
"several" deaths in the treated group, 2-nitropropane treatment was discontinued after 16 weeks,
and rats were held for 61 weeks without further exposure. The control animals continued
receiving vehicle treatments 1 day per week for 10 weeks (this group was also serving as a
control for additional chemicals) and were held for 51 weeks without vehicle exposure. Survival
and body weight were monitored (no further details provided). All surviving rats were sacrificed
during the 77th week after the first treatment. Gross necropsy was conducted on all terminal
sacrifice animals, as well as animals sacrificed moribund. Histopathology was performed for
neoplastic lesions; details of examination or tissues examined were not reported. The initial
number of rats in each group was not reported; the "effective" numbers of rats for tumor analysis
(not further defined) were 29 in the control group and 22 in the treated group. The study authors
reported statistical analysis of tumor incidence; however, the statistical methods were not
reported.
Reporting of non-neoplastic findings was limited to death in "several" treated rats during
the exposure phase of the study and "significantly lower" body weights throughout the study
(quantitative data for these endpoints were not reported). Based on these reported findings, the
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only administered dose of 90 mg/kg-day is a frank effect level (FEL). Adjusted for intermittent
exposure (3 days/week), the administered dose of 90 mg/kg-day is equivalent to an ADD of
39 mg/kg-day.
With respect to carcinogenicity endpoints observed, all surviving treated rats developed
hepatocarcinomas (22/22), and metastasis to the lung was observed in 4/22 treated rats; these
tumors were not observed in any control rats (0/29). Benign liver tumors were observed in
4/22 treated rats and 1/29 control rats. Observed tumors in other systems in the treated rats were
comparable to control (see Table B-7). Despite study limitations (small animal numbers, limited
reporting), this study shows that 2-nitropropane is a liver carcinogen by oral exposure in rats.
The administered dose of 90 mg/kg-day corresponds to a human equivalent dose (HED) of
9.8 mg/kg-day.2
Inhalation Exposures
Subchronic-Duration Studies
(youlston et a I. (19 78)
In an unpublished report, groups of Long-Evans rats (10/sex/group) were exposed to
2-nitropropane (purity not reported) at nominal concentrations of 0 or 200 ppm for 7 hours/day,
5 days/week for 2 months via whole-body exposure. Analytical concentrations for this study
were not reported. Based on the altitude of the Holloman Air Force Base testing facility
(1,350 m), the study authors indicated that the nominal test concentration of 200 ppm is
equivalent to 620 mg/m3 due to barometric pressure of approximately 650 mm Hg (as opposed to
760 mm Hg at sea level). Food and water were removed from the cages during the exposure
periods to avoid accidental oral exposure due to absorption of the compound into food and/or
water. At sacrifice, the following tissues were examined microscopically (based on reported
results): liver, lung, kidney, thyroid, lymph nodes, spleen, pancreas, and central nervous system
tissues. Statistical analysis was not conducted by the study authors. No other endpoints were
reported.
The only exposure-related lesion observed was hepatocellular vacuolization in exposed
males (10/10) compared with controls (0/10). Vacuolization was not observed in control or
exposed females. Incidences of lesions in other examined organs were comparable between
exposed and control animals.
The only exposure level of 620 mg/m3 is identified as a LOAEL based on hepatocellular
vacuolization in the liver of male rats. The nominal concentration of 620 mg/m3 was converted
into a human equivalent concentration (HEC) value of 129 mg/m3 for extrarespiratory effects.3
2The ADD dose was calculated as follows: 90 mg/kg-day x 3 days ^ 7 days = 39 mg/kg-day. The ADD was
converted into an HED of 9.8 mg/kg-day using a DAF of 0.25 (HED = ADD x DAF). The DAF was calculated as
follows: DAF = (BWa1/4 ^ BWh1'4), where DAF = dosimetric adjustment factor, BWa = animal body weight, and
B Wh = human body weight. Quantitative body weight data were not reported; therefore, reference body weights
recommended by the U.S. EPA (1988b) were used to calculate the D AF: 70 kg for humans and 0.267 kg for male
S-D rats in a subchronic-duration study.
'HEC calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA
(1994) methodology: HECEr = exposure level (mg/m3) x (hours/day exposed ^ 24 hours) x (days/week
exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 because
the rat blood-air partition coefficient of 183 is greater than the human blood-air partition coefficient of 154 as
indicated by Gargas et at (1989).
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Chronic-Duration/Carcinogenicity Studies with Interim Sacrifices
The chronic-duration inhalation studies also conducted interim sacrifices constituting
short-term or subchronic duration exposures. The results from these interim sacrifices are
discussed together in the text under the heading of "Chronic-Duration/Carcinogenic Studies with
Interim Sacrifices" below, and are provided under short-term, subchronic, and chronic headings
in Table 3 A for clarity.
Lewis et al. (1979); Ulrich et al. (1977)
Male S-D rats (50/group) were exposed to 2-nitropropane (94.45% purity) at nominal
concentrations of 0, 25, or 200 ppm for 7 hours/day, 5 days/week for up to 6 months via
whole-body exposure. Interim sacrifices (10 rats/group) were conducted at 2 days, 10 days,
1 month, and 3 months. Results were reported in a published study by Lewis et al. (1979);
additional data are also available in an unpublished study by Ulrich et al. (1977). Reported
analytical concentrations (mean± SD) were 27 ± 3 ppm (98 ±10 mg/m3) and 207 ±15 ppm
(754 ± 55 mg/m3). In the absence of information on altitude of the testing facility for this study,
inhalation exposures reported in ppm were converted to mg/m3 assuming standard temperature
and air pressure, yielding a conversion factor of 1 ppm = 3.6 mg/m3. Mortality and body weight
were monitored. At sacrifice, blood was collected for hematology (hemoglobin, erythrocyte
count, prothrombin time, methemoglobin) and serum chemistry (ALT, ornithine carbamoyl
transferase [OCT], T4), and all animals underwent a complete necropsy. The liver, kidney, lungs
plus trachea, brain, and thyroid were removed and weighed. Brain and lung edema was
evaluated using classical wet and dry weight techniques. The following tissues were examined
microscopically: adrenals, bronchi, cerebellum, cerebral hemispheres, eyes, kidneys, liver, lung,
spleen, thyroid, and trachea. Data were evaluated by parametric methods with Bartlett's test for
homogeneity of variance (rejection level set at p = 0.01) followed by one-way ANOVA with the
rejection level set at/? = 0.10. When significant differences were indicated, data were further
analyzed by Student's Mest with the significance level set at p = 0.05.
No exposure-related changes in survival were reported. Body weights were significantly
decreased by 11-36% in rats exposed to 754 mg/m3 for >2 days, compared with controls; greater
decreases were observed at earlier time points (see Table B-15). Body weights in rats exposed to
98 mg/m3 were comparable to controls. Sporadic changes were observed in some hematological
parameters, but none of the findings showed a clear concentration- or time-related change.
Serum ALT levels were significantly elevated by 22-23% at 10 days to 1 month in rats exposed
to 754 mg/m3; this effect was not observed at 3 months, but serum ALT levels were significantly
elevated again at 6 months by almost fivefold (see Table B-16). Serum OCT levels in exposed
animals were not significantly different from control at any time point (see Table B-16).
Sporadic significant changes in serum T4 levels were reported, including a 21% decrease at
98 mg/m3 at 2 days and an 83% increase at 754 mg/m3 at 3 months; however, these findings do
not represent clear exposure- or time-related findings (see Table B-16).
Relative liver weights were significantly increased by 24-176%) after exposure to
754 mg/m3 for >10 days; absolute liver weights were also significantly increased by 42-144%) at
3 and 6 months (see Table B-15). Absolute and relative lung weights were significantly
increased by 23 and 37%, respectively, after exposure to 754 mg/m3 for 6 months; however,
absolute and/or relative lung weights were significantly decreased by 20—53%> after 2-30 days of
exposure (see Table B-17). Lung weight changes at 754 mg/m3 were accompanied by a small,
but significant, 2—5% increase in water content at 1-6 months, indicating mild lung edema
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(see Table B-17). Relative brain weight was also significantly elevated by 7-25% in rats
exposed to 754 mg/m3 at all time points (see Table B-18); no evidence of brain edema was
reported. Kidney and thyroid weight changes did not show a consistent pattern regarding
direction of change, exposure level, or time (see Tables B-15 andB-18).
Liver weight changes at 754 mg/m3 were accompanied by increased incidence of gross
and microscopic hepatic lesions (see Table B-19). Gross necropsy showed an increased
incidence of pale livers and surface lesions on the liver in rats exposed to 754 mg/m3 for
3 months. At 6 months, livers were enlarged and pale and showed numerous masses and lesions
in rats exposed to 754 mg/m3. Non-neoplastic histopathology findings included significantly
increased incidence of pericholangitis at 10 days and focal hepatocyte hypertrophy and
hyperplasia and basophilic foci at 3 months. Findings at 6 months were limited to neoplastic
lesions (discussed below). No hepatic lesions were significantly increased after exposure to
98 mg/m3. Pulmonary weight changes were associated with increased incidence of gross
pulmonary abnormalities in rats exposed to 754 mg/m3 for 1, 3, or 6 months (quantitative data
not reported by study authors); however, the incidence of microscopic pulmonary lesions was
comparable between control and exposed groups. Changes in brain weight were not
accompanied by evidence of exposure-related brain lesions. Exposure-related lesions were not
identified in other evaluated organs.
ANOAEL of 98 mg/m3 and a LOAEL of 754 mg/m3 are identified following 6-months
of exposure based on decreased body weight, elevated serum ALT, elevated absolute and relative
liver weights, and elevated lung weight and edema. Similarly, a LOAEL of 98 mg/m3 is
identified following 3-months of exposure based on increased absolute liver weight and relative
kidney weight (>10%) and no NOAEL could be identified. A LOAEL of 98 mg/m3 is identified
for increased absolute and relative kidney weights (>10%) following 1 month of exposure. No
1-month NOAEL could be identified. A NOAEL of 98 mg/m3 and a LOAEL of 754 mg/m3 are
identified for the short-term interim sacrifice at 10 days based on decreased body weight,
elevated serum ALT, elevated relative liver weight, and hepatic pericholangitis. The analytical
concentrations of 98 and 754 mg/m3 correspond to HEC values of 20 and 157 mg/m3,
respectively, for extrarespiratory effects.4
With respect to carcinogenicity endpoints observed, neoplastic findings at 6 months
included hepatocellular carcinoma and neoplastic nodules in all 10 rats exposed to 754 mg/m3;
no neoplastic hepatic lesions were observed in controls or rats exposed to 98 mg/m3. No
exposure-related neoplastic lesions were observed in other organs.
Collision et al. (19 78)
In an unpublished report, the study authors indicated that groups of S-D rats
(125/sex/group) were exposed to 2-nitropropane (purity not reported) at nominal concentrations
of 0 or 200 ppm for 7 hours/day, 5 days/week for up to 6 months via whole-body exposure.
Interim sacrifices (10 rats/sex/group) were conducted at 10 days, 1 month, 3 months, and
6 months. Additionally, a recovery group (10 rats/sex) was removed from exposure after
'HEC calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA
(1994) methodology: HECEr = exposure level (mg/m3) x (hours/day exposed ^ 24 hours) x (days/week
exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 since the
rat blood-air partition coefficient of 183 is greater than the human blood-air partition coefficient of 154 as indicated
by Gargas et at (1989).
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3 months and maintained until terminal sacrifice (6 months). All surviving animals not included
in interim sacrifices were sacrificed 6 months after exposure initiation. A separate recovery
group (10 rats/sex) was exposed for 6 months and then sacrificed after a 6-month recovery
period; only neoplastic findings for this group were reported (10 males, 1 female). Based on
reported results, it appears that animal numbers were 40/sex/group in the main study with an
additional 20/sex in the recovery groups. The reported analytical concentration in the exposure
group (mean ± SD) was 196 ± 12 ppm. Based on the altitude of the Holloman Air Force Base
testing facility (1,350 m), the study authors reported that the nominal test concentration of
200 ppm is equivalent to 620 mg/m3 (conversion factor of 1 ppm = 3.1 mg/m3) due to barometric
pressure of approximately 650 mm Hg (instead of the standard conversion factor of
1	ppm = 3.6 mg/m3 at 760 mm Hg). Using the appropriate conversion factor for this testing
facility, the analytical concentration is equal to 608 ± 37 mg/m3.
Food and water were removed from the cages during the exposure periods to avoid
accidental oral exposure due to absorption of the compound into food and/or water. Body
weights were recorded weekly. At sacrifice, blood samples were obtained for clinical chemistry
(ALT [reported as glutamic-pyruvic transaminase], OCT, T4, T3 uptake) and hematology
(erythrocyte count, leukocyte count, pack cell volume, hemoglobin concentration,
methemoglobin concentration, prothrombin time). Blood was also collected under anesthesia
after 2 and 5 months of exposure for examination of these parameters. The brain, liver, kidney,
lung, and thyroid were removed and weighed. A detailed histopathological exam was conducted
on the liver from all animals. The lung, liver, kidney, spleen, thyroid, and central nervous
system tissues were examined microscopically. Statistical analysis was conducted for
continuous data using an unspecified method. Hepatic lesion incidence was statistically
analyzed using methods established by Mainland et al. (1956) as cited by Coulston et al. (1978);
no details on this method were provided.
Body weight was decreased by 4-13% in male rats through Week 27; all decreases >10%
occurred within the first 6 weeks of exposure (see Table B-26); no exposure-related changes
were observed in female rat body weights (see Table B-27). Statistically significant changes in
hematological parameters were observed sporadically; however, no clearly time-related pattern
or direction of change was observed (see Tables B-28 and B-29). Serum ALT levels were
elevated by 20-354%) in all evaluated groups of male rats; these findings were statistically
significant at 10 days, 3 months, and 6 months (see Table B-30); serum ALT was comparable to
control in recovery males exposed for 3 months and maintained unexposed for 3 additional
months. Serum AST was also elevated fivefold in male rats at 6 months (not evaluated at other
time points) (see Table B-30). Slight, but statistically significant, changes were observed in
serum thyroid hormone levels in exposed males, including a 26%> decrease in serum T4 at
2	months and 7-8%> decreases in serum T3 uptake at 3-6 months (see Table B-30). No
exposure-related changes in serum biochemistry were observed in females.
Significant relative organ weight changes are presented in Table B-26 (males) and
Table B-27 (females); the study authors did not report absolute organ weights. Relative liver
weights were significantly elevated by 28-44%> in males at 3 and 6 months and by 25-29% in
females at 1, 3, and 6 months. Relative liver weights were comparable to controls in both sexes
in the group exposed for 3 months and maintained unexposed for 3 additional months. Relative
kidney weights remained within 10%> of control at all time points in both sexes; however, the
9% increase observed in exposed males at 3 months was statistically significant. The only other
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significant change observed in organ weights was a 19% increase in relative brain weight in
males at 10 days; the biological significance of this finding is unclear because it was not
observed at later time points. Only liver weight effects were considered exposure-related by the
study authors.
Non-neoplastic histopathological findings associated with exposure were limited to the
liver and were observed predominately in males at all sacrifices. The study authors concluded
that early microscopic changes were indicative of initial "toxic hepatitis," while findings at later
time points are suggestive of the early stages of proliferative lesion development. The study
authors did not report statistics for lesions incidence; however, a statistical analysis was
conducted for this review (Fisher's exact test). Microscopic indicators of liver pathology that
were significantly increased at 10 days in males included basophilic foci, single liver cell
necrosis, mitotic cells, and bile duct proliferation; however, only the incidence of single liver cell
necrosis was still significantly elevated at 30 days (see Table B-31). Findings at 3 months in
males included significant increases in cytoplasmic vacuolation, nuclear changes in >6 cells, and
broken "cell walls" (see Table B-32). After 6 months of exposure, significant increases were
observed in the incidence of focal accumulation of macrophages, cytoplasmic inclusions, and
hypertrophic and hyperplastic areas and/or nodules (see Table B-32). Significant increases in
hypertrophic and hyperplastic areas and/or nodules were also observed in male rats at 6 months
and in those that were exposed for 3 months and then maintained unexposed for 3 months
(see Table B-32). Significant changes in exposed females were limited to increased glycogen
content at 10 days (see Table B-33) and cytoplasmic vacuolation at 6 months (see Table B-34).
The biological relevance of the glycogen content finding is unclear, as it was not observed at
later time points and was observed at a high incidence in control animals.
The only administered concentration (608 mg/m3) is considered a LOAEL for the
6-month component of the study based on elevated relative liver weights in males and females,
altered liver serum biochemistry in males, and microscopic liver changes in males and females.
Based on interim sacrifices at 1 and 3 months, a subchronic LOAEL of 608 mg/m3 is also
identified for decreased body weight in males, elevated relative liver weights in males and
females, altered liver serum biochemistry in males, and microscopic liver changes in males.
Additionally, based on the interim sacrifice at 10 days, a short-term LOAEL of 608 mg/m3 is
identified for altered liver serum biochemistry and microscopic liver changes in males. The
analytical concentration of 608 mg/m3 corresponds to an HEC value of 127 mg/m3 for
extrarespiratory effects.5
With respect to carcinogenicity endpoints observed, nodules in male rats at 6 months
were considered to have features indicative of "malignant transformation," but they were not
specifically described as tumors. In male rats exposed for 6 months and then maintained
unexposed for 6 months, 9/10 had liver tumors with metastasis. Control data were not reported
in this recovery group, and it appears that only one female was evaluated (showing
multinucleated cell plates, loss of cohesion, and trabecular formation in the liver).
5HEC calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA
(1994) methodology: HECEr = exposure level (mg/m3) x (hours/day exposed ^ 24 hours) x (days/week
exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 because
the rat blood-air partition coefficient of 183 is greater than the human blood-air partition coefficient of 154 indicated
by Gargas et at (1989).
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Griffin et al. (1981); Griffin et al. (1980)
Griffin et al. (1981) and Griffin et al. (1980) exposed groups of S-D rats (125/sex/group)
to 2-nitropropane (95.65% purity) at nominal concentrations of 0 or 25 ppm for 7 hours/day,
5 days/week for up to 22 months via whole-body exposure. Interim sacrifices
(10 rats/sex/group) were conducted at 1, 3, 6, and 12 months. Additionally, recovery groups
(10 rats/sex/group) were removed from exposure after 3 and 12 months and maintained until
terminal sacrifice. All surviving animals were sacrificed 22 months after exposure initiation.
Reported analytical concentration in the exposure group (mean ± standard deviation [SD]) was
25.1 ± 1.4 ppm. Based on the altitude of the Holloman Air Force Base testing facility (1,350 m),
the study authors reported that the nominal test concentration of 25 ppm is equivalent to
78 mg/m3 (conversion factor of 1 ppm = 3.1 mg/m3) due to barometric pressure of approximately
650 mm Hg (instead of the standard conversion factor of 1 ppm = 3.6 mg/m3 at 760 mm Hg).
Using the appropriate conversion factor for this testing facility, the analytical concentration is
equal to 77.8 ± 4.3 mg/m3.
Food and water were removed from the cages during the exposure periods to avoid
accidental oral exposure due to absorption of the compound into food and/or water. Rats were
observed daily for mortality and clinical signs of toxicity. Body weights were recorded weekly.
At sacrifice, blood samples were obtained for clinical chemistry (ALT, ornithine carbamyl
transferase [OCT], thyroxine [T4], triiodothyronine [T3] uptake) and hematology (erythrocyte
count, leukocyte count, packed cell volume, hemoglobin concentration, methemoglobin
concentration, prothrombin time). The brain, liver, and kidney were removed and weighed. A
complete set of 33 tissues, along with all grossly observable lesions, was fixed for histological
examination. For continuous data sets, Student's /-test was used to compare treatment group
means with respective control group means. For noncontinuous data sets, Fisher's exact test
conducted by the U. S. EPA for the purposes of this PPRTV assessment was used to compare
treatment group means with respective control group means.
No exposure-related mortalities or clinical signs were reported. No exposure-related
body weight effects were noted in male rats (see Table B-8). In females, body weights were
significantly increased by 13-17% in the exposure group at 6, 12, and 22 months, compared with
controls (see Table B-9). A significant 8% increase in body weight was also reported at terminal
sacrifice for female rats exposed for 3 months, and then maintained unexposed until 22 months.
Sporadic, but statistically significant, changes in hepatic clinical chemistry parameters were
observed in exposed males; however, changes were 
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relative liver weights were also significantly increased by 17% at 6 months (see Table B-8). In
exposed females, significant 17-23% increases in absolute liver weight were observed at 6, 12,
and 22 months, compared with controls; however, no exposure-related findings were observed
for relative liver weight at any time point (see Table B-9). Absolute kidney weight was
significantly increased by 12% in exposed males at 12 months and exposed females at 1 month,
compared with control; however, no significant changes in absolute kidney weight were
observed at other time points (see Tables B-8 and B-9). Relative kidney weights were not
reported. No exposure-related changes in absolute or relative liver or absolute kidney weight
were observed in recovery males or females. Absolute brain weights were comparable between
exposed and control rats throughout the study; relative brain weights were not reported.
Histopathological lesions, including focal areas of vacuolation in hepatocytes, focal
hepatocellular nodules, and liver congestion, were elevated in exposed males, compared with
controls (see Table B-14). In females, only the incidence of liver congestion was elevated. The
study authors only reported findings for all animals combined (interim sacrifices and all terminal
sacrifices, including recovery groups), so information on the timing of lesion development is
unknown. Exposure-related lesions were not observed in other tissues or organ systems.
The only exposure level (77.8 mg/m3) is identified as a chronic LOAEL based on
increased relative liver weight and focal vacuolization and nodules in the liver of male rats, as
well as liver congestion in male and female rats exposed to 2-nitropropane for interim sacrifices
performed between 6-22 months. The analytical concentration of 77.8 mg/m3 corresponds to an
HEC value of 16.2 mg/m3 for extrarespiratory effects.6 No chronic NOAEL is identified. For
the 1- and 3-month component of the study, however, the only concentration tested of
16.2 mg/m3 is identified as a subchronic NOAEL based on the lack of consistent effects being
observed at later timepoints. Specifically, in female rats, absolute liver and kidney weights were
biologically significantly increased after 1 month of exposure but these effects were not observed
after 3 months of exposure.
No evidence of exposure-related carcinogenic effects was noted in this study. Tumor
incidences in all tissues and organ systems were comparable in control and exposed groups.
Griffin etal. (1979)
In an unpublished report, groups of S-D rats (125/sex/group) were exposed to
2-nitropropane (95.65%) purity) at nominal concentrations of 0 or 100 ppm for 7 hours/day,
5 days/week for up to 18 months via whole-body exposure. Interim sacrifices (10-20/sex/group)
were conducted at 1, 3, 6, 9, and 12 months. Additionally, recovery groups (10/sex/group) were
removed from exposure after 3, 6, or 9 months, and maintained until terminal sacrifice
(18 months). All surviving animals not included in interim sacrifices were sacrificed 18 months
after exposure initiation. Reported analytical concentration in the exposure group (mean ± SD)
was 100 ± 3 ppm. Based on the altitude of the Holloman Air Force Base testing facility
(1,350 m), the study authors reported that the nominal test concentration of 100 ppm is
equivalent to 312 mg/m3 (conversion factor of 1 ppm = 3.1 mg/m3) due to barometric pressure of
' HEC calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA
(1994) methodology: HECEr = exposure level (mg/m3) x (hours/day exposed ^ 24 hours) x (days/week
exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 because
the rat blood-air partition coefficient of 183 is greater than the human blood-air partition coefficient of 154 as
indicated by Carats et at (1989).
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approximately 650 mm Hg (instead of the standard conversion factor of 1 ppm = 3.6 mg/m3 at
760 mm Hg). Using the appropriate conversion factor for this testing facility, the analytical
concentration is equal to 312 ± 9 mg/m3.
Food and water were removed from the cages during the exposure periods to avoid
accidental oral exposure due to absorption of the compound into food and/or water. Rats were
observed daily for mortality and clinical signs of toxicity. Body weights were recorded weekly.
Gross necropsy was conducted on all animals at interim and terminal sacrifice, as well as for any
animal that died or was sacrificed moribund during the study. At interim and terminal sacrifices,
blood samples were obtained for clinical chemistry (ALT [reported as glutamic-pyruvic
transaminase], OCT, T4, T3 uptake) and hematology (erythrocyte count, leukocyte count, packed
cell volume, hemoglobin concentration, methemoglobin concentration, prothrombin time). The
brain, liver, and kidney were removed and weighed. At terminal sacrifice only, the lung, liver,
kidney, lymph node, and any unusual lesions were fixed for histological examination. No
statistical tests were reported.
Body weights were decreased by 22% in male rats exposed for 18 months and by
12-25% in male rats exposed for 6 or 9 months, then sacrificed at 18 months (see Table B-20).
Body weights in other exposed male groups and in all exposed female rats were within 10% of
respective control values throughout exposure (see Tables B-20 and B-21). In male rats, serum
ALT was increased 4.5-fold in the group exposed for 18 months, 2.2-fold in the group exposed
for 6 months and then sacrificed at 18 months, and 23-fold in the group exposed for 9 months
and then sacrificed at 18 months (see Table B-22). While serum ALT values varied greatly
among animals, statistical analysis conducted for this review indicated that these increased
values in exposed males were significantly different from respective controls in the Lewis et al.
(1979) and Ulrich et al. (1977) studies as well (see Table B-16). In females, no exposure-related
serum ALT changes were reported. No exposure-related changes were observed in serum OCT,
T4, T3 activity, or hematology in either sex.
Absolute liver weights were increased by >10% in all groups of exposed male rats, and
relative liver weights were increased by >10% in male rat groups exposed for 3 months or
longer, compared with respective controls (see Table B-20). Increases in liver weight were
greater following longer exposure, with increases in absolute and relative liver weight up to
242 and 375%>, respectively. In females, absolute and relative liver weights were comparable
between exposure and control groups throughout the experiment, with weights generally within
10%) of control values and no clear time-related pattern or direction of change (see Table B-21).
Similarly, absolute kidney weights were generally within 10%> of control at all time points in
both males and females, with no clear time-related pattern or direction of change
(see Table B-23). No exposure-related changes were observed in absolute brain weights.
Relative kidney weights and brain weights were not reported by study authors.
The combined incidence of grossly observed hepatic masses (unspecified) and nodules
was significantly increased in males exposed for 12 or 18 months, all recovery groups, and
animals found dead or sacrificed moribund, compared to respective controls, but not in females
(see Table B-24). Histopathological examination of the livers in animals sacrificed at 18 months
showed significant increases in hepatocellular carcinoma (discussed in more detail below) and
focal necrosis in male rats and vacuolar degeneration and nodular hyperplasia in both male and
female rats, compared with controls (see Table B-25). Increased incidence of renal calcification
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was also observed in exposed rats at 18 months, although this finding was only statistically
significant in males (see Table B-25). No other non-neoplastic lesions were associated with
exposure to 2-nitropropane. Animals that died during the study or were sacrificed at other time
points were not examined for histopathology.
The only exposure level (312 mg/m3) is identified as a chronic LOAEL based on
decreased body weights, renal calcification, elevated ALT, and elevated absolute and relative
liver weights in male rats and degenerative and hyperplastic hepatic lesions in male and female
rats. Based on available interim sacrifice data at 1 and 3 months, 312 mg/m3 is also identified as
a subchronic LOAEL based on elevated absolute and/or relative liver weights in males. The
analytical concentration of 312 mg/m3 corresponds to an HEC value of 65.0 mg/m3 for
extrarespiratory effects.7 No NOAEL is identified.
With respect to carcinogenicity endpoints, hepatocellular carcinoma was observed in
7/23 males examined for histopathology at 18 months, compared with 0/63 control males
(see Table B-25). Based on a Fisher's exact test conducted for this review, this finding is
significant. Grossly observed hepatic masses/nodules (hyperplastic), found in 11 of 16 exposed
males that died or were sacrificed moribund during the study (see Table B-24), potentially
included some carcinomas as well, but no histological examination was performed for these
animals. Hepatocellular carcinoma was not observed in control or exposed females. Other
observed neoplasms in exposed groups were comparable or lower than respective control
incidence.
Lewis et al (1979); Ulrichetal. (1977)
Groups of male New Zealand White rabbits (15/group) were exposed to 2-nitropropane
(94.45% purity) at nominal concentrations of 0, 25, or 200 ppm for 7 hours/day, 5 days/week for
up to 6 months via whole-body exposure. Interim sacrifices (5 rabbits/group) were conducted at
1 and 3 months. Results were reported in a published study by Lewis et al. (1979); additional
data are also available in an unpublished study by Ulrich et al. (1977). Reported analytical
concentrations (mean ± SD) were 27 ± 3 ppm (98 ±10 mg/m3) and 207 ±15 ppm
(754 ± 55 mg/m3). In the absence of information on altitude of the testing facility for this study,
inhalation exposures reported in ppm were converted to mg/m3 assuming standard temperature
and air pressure, yielding a conversion factor of 1 ppm = 3.6 mg/m3. Mortality and body weight
were monitored. At sacrifice, blood was collected for hematology (hemoglobin, erythrocyte
count, prothrombin time, methemoglobin) and serum chemistry (ALT, OCT, T4), and all animals
underwent a complete necropsy. The liver, kidney, lungs plus trachea, brain, and thyroid were
removed and weighed. Brain and lung edema was evaluated using classical wet and dry weight
techniques. The following tissues were examined microscopically: adrenals, bronchi,
cerebellum, cerebral hemispheres, eyes, kidneys, liver, lung spleen, thyroid, and trachea. Data
were analyzed using nonparametric statistical methods. First, a Kruskal-Wallis one-way
ANOVA was conducted. If differences were indicated (p >0,10), the Mann-Whitney U test was
used.
HEC calculated by treating 2-nitropropane as a Category 3 gas and using the following equation from U.S. EPA
(1994) methodology: HECEr = exposure level (mg/m3) x (hours/day exposed ^ 24 hours) x (days/week
exposed 7 days) x ratio of blood-gas partition coefficient (animal:human), using a default coefficient of 1 because
the rat blood-air partition coefficient of 183 is greater than the human blood-air partition coefficient of 154 as
indicated by Gargas et al. (1989).
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No exposure-related changes in survival were reported. Body weights were comparable
between exposed and control rabbits throughout the experiment (see Table B-35). Sporadic
changes were observed in some hematological parameters, but none of the findings showed a
clear concentration- or time-related change. Serum ALT and OCT levels were significantly
elevated by 73 and 330%, respectively, after exposure to 754 mg/m3 for 1 month, compared with
controls; these effects were not observed at 3 or 6 months in rabbits exposed to 754 mg/m3 or at
any time point in rabbits exposed to 98 mg/m3 (see Table B-36). Serum T4 levels were elevated
by 6-81% after exposure to 754 mg/m3 for 1-6 months, but findings were only significantly
different from controls at 6 months (see Table B-36). However, nonsignificant decreases in
serum T4 were observed at all time points after exposure to 98 mg/m3; therefore, the biological
relevance of these findings is unclear. Sporadic, significant changes in organ weight were
observed, but findings did not show a consistent pattern regarding direction of change, exposure
level, or time (see Tables B-35, B-37, and B-38).
Potentially exposure-related lesions were limited to non-neoplastic findings in the lungs
in rabbits exposed to 754 mg/m3 at 1 month, including alveolar necrosis, focal hemorrhage, and
pulmonary edema, each in 3/5 rabbits compared to 0/5 controls (see Table B-39). However,
incidences of pulmonary lesions were similar between exposed and control rabbits at 3 and
6 months (see Table B-39). Additionally, quantitative analysis did not show an exposure-related
increase in lung edema at any time point (see Table B-37). In contrast to similarly exposed rats
(discussed above), no statistically significant increases of microscopic lesions in the liver were
observed compared to controls (see Table B-40). No exposure-related lesions were observed in
other evaluated organs.
The highest exposure level (754 mg/m3) is identified as a NOAEL for a lack of adverse
findings following exposure for 1, 3, and 6 months. The analytical concentrations of 98 and
754 mg/m3 correspond to HEC values of 20 and 157 mg/m3, respectively, for extrarespiratory
effects8 and 16 and 130 mg/m3, respectively, for pulmonary effects.8 No exposure-related
neoplastic lesions were observed in rabbits.
82-Nitropropane has characteristics of a highly reactive, Category 1 gas that often results in portal-of-entry effects in
the PU region as well as less reactive Category 3 gas for ER effects. As HEC equations for a Category 2 gas are
currently unavailable, the HECs are calculated using both Category 1 and Category 3 gas equations. The HEC for
extrarespiratory effects was calculated by treating 2-nitropropane as a Category 3 gas and using the following
equation from U.S. EPA (1994) methodology: HECer = exposure level (mg/m3) x (hours/day
exposed 24 hours) x (days/week exposed 7 days) x ratio of blood-gas partition coefficient (animal:human),
using a default coefficient of 1 since the rabbit blood-air partition coefficient of 170 indicated by AFOSR (1992) is
greater than the human blood-air partition coefficient of 154 as indicated by Gargas et at (1989). AFOSR (1992)
reported their value as body-air partition coefficient, but it is assumed to be essentially equivalent to a blood-air
value, as their body: air value for rats of 180 is almost the same as the Gargas et at (1989) blood-air value of 183 for
that species. HEC values for pulmonary effects were calculated by treating 2-nitropropane as a Category 1 gas and
using the following equation from U.S. EPA (1994) methodology: HECPU = exposure level (mg/m3) x (hours/day
exposed ^ 24 hours) x (days/week exposed ^ 7 days) x RGDRPU, where RGDRPU for the 27- and 207-ppm groups
were calculated to be 0.80 and 0.83, respectively, using Equation 4-28 in U.S. EPA (1994) and minute volume (Ve)
values of 1.23 and 1.26 L/minute, respectively [calculated based on TWA body weight of 3.3 and 3.4 kg,
respectively, calculated from body weight data estimated from graphically presented data in Ulrich et al. (1977)
using Grab It! software], and the following default values from U.S. EPA (1994): VE of 13.8 L/minute for humans,
SApu of 59,000 cm2 for rabbits and 540,000 cm2 for humans, SATb of 300 cm2 for rabbits and 3,200 cm2 for humans,
and SAet of 30 cm2 for rabbits and 200 cm2 for humans.
28
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Reproductive/Developmental Studies
A screening developmental toxicity study by Hardin et al. (1981) reported delayed
cardiac development in the offspring of rat dams exposed to 170 mg/kg-day via intraperitoneal
(i.p.) injection on Gestation Days (GDs) 1-15. No exposure-related changes in fetal body
weight, length, or skeletal or visceral malformations were observed. No maternal toxicity was
observed.
OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)
Genotoxicity Studies
The genotoxicity of 2-nitropropane has been extensively evaluated in vitro and in vivo.
Available studies are summarized below (see Table 4A for more details). Available data indicate
that 2-nitropropane is a genotoxic agent. It is an established mutagen, and there is consistent
evidence for chromosomal effects and DNA damage in hepatic cells and tissues. There is also
some evidence for chromosomal effects and DNA damage in bone marrow cells and
lymphocytes.
29
2-Nitropropane
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Genotoxicity studies—prokaryotic organisms
Mutation
Salmonella typhimurium
TA100, TA102
0-80 (imol/plate
TA100,
TA102
+
TA100,
TA102
Preincubation assay. There was a
significant increase of revertants at
40 (imol/plate with metabolic
activation in TA100 and in TA102 at
80 (imol/plate. There was a
dose-dependent increase in revertants
without metabolic activation, but
results were not significant.
Conawav et al.
(1991a)
Mutation
S. typhimurium
TA98, TA100, TA102
0, 1.7,3.5,6.9, 13.9,
27.7, 55.4 (imol/plate
+
TA100,
TA102
TA98
+
TA100,
TA102
TA98
Preincubation assay.
Neutral 2-nitropropane significantly
induced mutations at 55 (imol/plate
with and without activation.
2-Nitropropane nitronate (anionic
form of 2-nitropropane) also induced
mutations at ~4 (imol/plate. No
mutations were induced in TA98.
Fialaet al. (1987a)
30
2-Nitropropane
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FINAL
September 2019
Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Mutation
S. typhimurium
TA98, TA100, and their NR-deficient
strains TA98NR and TA100NR
0,2.1,4.2, 10.5,21.0,
31.5 mM
+
TA98,
TA100,
TA98NR,
TA100NR
+
TA98,
TA100,
TA98NR,
TA100NR
Preincubation assay.
Cytotoxicity was reported at doses
>21 mM (~5 mg/plate).
An increased number of revertants
occurred at 10.5 mM (2.45 mg/plate)
in the TA100 strain (~10-fold) and in
the TA98 strain (~12-fold) over
control values without metabolic
activation; comparable mutagenicity
was noted with metabolic activation.
Goggelmarm et al.
(1988)






2-Nitropropane was less mutagenic in
the NR-deficient strains (4- to 5-fold
increases in revertants).

Mutation
S. typhimurium
TA98, TA100, TA1535, TA1537,
TA1538
0, 1,500, 3,000,4,500,
5,000, 6,000,
7,500 (ig/plate
TA98,
TA100,
TA1535,
TA1537,
TA1538
±
TA1535,
TA98, TA100
TA1537,
TA1538
Plate incorporation assay. Weakly
mutagenic. There was a
dose-dependent increase in the
number of mutations in strains
TA1535, TA98, and TA100 with
metabolic activation.
Mutation frequencies were 2.18-,
1.9-, and 2.0-times higher in strains
TA1535, TA98, and TA100,
respectively, compared to controls.
The only concentration tested without
activation was 5,000 (ig/plate
Russell and Krahn
(1977)
Mutation
S. typhimurium
TA98, TA100, TA1535, TA1537
0, 33.0, 100, 333,
1,000, 1,666, 3,333,
6,666, 10,000 (ig/plate
+
(TA98, A100,
TA1535,
TA1537)
+
(TA98, A100,
TA1535,
TA1537)
Preincubation assay. Increased
number of revertants.
Haworth et al.
(1983)
31
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Mutation
S. typhimurium
TA92, TA98, TA100, TA1537
0,0.0037,0.1,0.03,
0.011 mL per plate
+
TA92, TA98,
TA100,
TA1537
+
TA92, TA98,
TA100,
TA1537
Preincubation assay. Dose-dependent
increase in revertants in all 4 test
strains. Undiluted 2-nitropropane
was inhibitory for strains TA1537,
TA98, and TA100.
Hite and Skeees
(1979)
Mutation
S. typhimurium
TA100, TA102
0, 0.2-16 (imol/plate
+
TA100,
TA102
NDr
Preincubation assay.
Dose-dependent induction of
mutations. 2-Nitropropane induced
mutagenicity was also tested over a
range of pH levels. The rate of
mutagenicity was increased with
increased pH. Cytotoxicity was
present at highest concentrations.
KoMetal. (1994)
Mutation
S. typhimurium
TA98, TA100, TA1535, TA1537,
TA1538
Without metabolic
activation: 0, 0.001,
0.01,0.1, 1.0,
5.0 |iL/platc
With metabolic
activation: 0, 0.001,
0.01,0.1, 1.0, 5, 10,
20 (iL/plate

+
TA98
TA100,
TA1535,
TA1537,
TA1538
Plate incorporation assay. Slight
toxicity was seen in strain TA1537 at
5 (iL/plate. Negative results reported
for all strains without metabolic
activation; negative results for strains
TA100, TA1535, TA1537, TA1538
with activation; 2-nitropropane was
mutagenic in S. typhimurium strain
TA98 with metabolic activation at
>10 (iL/plate.
Litton Bionetics
f1977b). Litton
Bionetics (1977a)
Mutation
S. typhimurium
TA98, TA100, TA1535
Unspecified (notes
highest doses tested
are mostly
20-50 mg/plate)
+
TA98, TA100
±
TA1535
+
TA98, TA100
±
TA1535
Plate incorporation assay.
Increased number of revertants per
mg in TA98 and TA100. Only a
slight increase in number of
revertants per mg in TA1535.
Lofroth et al.
(1986)
32
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Mutation
S. typhimurium
TA98, TA100, and their NR-deficient
strains TA98NR101 and TA100NR3
0,0.1,0.33, 1.0,3.3,
10.0, 20.0 mg/plate
+
TA98,
TA100,
TA98NR101,
TA100NR3
+
TA98,
TA100,
TA98NR101,
TA100NR3
Preincubation assay.
There was a dose-dependent increase
in the number of revertants. There
was an increase in the number of
revertants with metabolic activation,
but mutagenicity is not dependent on
the presence of S9 microsomes.
Also, mutagenic in the NR-deficient
strains.
Soeck et al. (1982)
DNA damage
(SOS
chromotest)
S. typhimurium
NM7000 (parent strain), NM7001,
NM7002, NM7003 (new strains
expressing human SULT 1A1, 1A2,
and 1A3, respectively)
1,000, 2,000, 4,000,
10,000 pM
+
NM7002
NM7000,
NM7001,
NM7003
NDr
Umu assay. DNA damage was
induced in NM7002 strain
(expressing SULT1A2) at
>2,000 (iM. DNA damage was not
induced in other strains.
Odaetal. (2012)
Genotoxicity studies—nonmammalian eukaryotic organisms
Mutation
Saccharomyces cerevisiae
D4
Without metabolic
activation: 0, 0.001,
0.01,0.1, 1.0,
5.0 ng/plate
With metabolic
activation: 0, 0.001,
0.01,0.1, 1.0,2.0, 10,
20 ng/plate


Negative with and without metabolic
activation.
Litton Bionetics
(1977b)
33
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Genotoxicity studies in mammalian cells—in vitro
Mutation
Rat hepatoma H4IIEC3/G cells, hprt
locus
0.3-10 mM
24 hr
+
NDr
Mutagenicity was estimated by
measuring the induction of clones
resistant to TG.
Cells were pretreated with
dexamethasone (an inducer of
liver-specific CYP450 forms; results
were negative without this
pretreatment).
Cytotoxicity was only present when
treated with dexamethasone.
Induced frequency of TG-resistant
cells with dexamethasone treatment,
but not without.
Roscher et al.
(1990)
Mutation
Chinese hamster lung V79 cells, hprt
locus
0, 3 mM
+
NDr
Induced mutations at 3 mM.
V79 cells capable of reducing and
oxidizing 2-nitropropane, but reduced
metabolites (acetone oxime) were
found not responsible for mutations.
Haas-Jobelius et
al. (1991)
Mutation
Gene mutation, Chinese hamster lung
V79 cells, hprt locus
0.3-10 mM
3 hr
+
NDr
Mutagenicity was estimated by
measuring the induction of clones
resistant to TG. Induced frequency of
TG-resistant cells with and without
dexamethasone treatment.
Marginally cytotoxic at all treatment
levels.
Roscher et al.
(1990)
34
2-Nitropropane
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
CA
Primary human lymphocytes from a
healthy female donor
Without S9: 0, 15, 30,
60, 80 mM
With S9: 0, 7.5, 15,
30, 60, 80 mM
+
+
CAs were induced in the presence of
metabolic activation at 60 and
80 mM, and without activation at
80 mM. CAs included open breaks
and gaps in chromatid.
Bauchinger et al.
(1987)
CA
Human lymphocytes
0, 30, 60, 80, 111 mM

+
CAs were increased at >80 mM. CAs
were not significantly induced
without activation.
Highest tolerated dose was 111 mM
for cells to undergo mitosis.
Goggelmann et al.
(1988)
CA
CHO cells
160-5,000 (ig/mL
—
—
2-Nitropropane did not induce CAs
with or without metabolic activation.
Gallowav et al.
(1987)
SCE
Primary human lymphocytes from a
healthy female donor
Without S9: 0, 15, 30,
60, 80 mM
With S9: 0, 7.5, 15,
30, 60, 80 mM
+
+
SCEs were increased at all doses with
metabolic activation and at 80 mM
and without activation.
Bauchineer et al.
(1987)
SCE
Human lymphocytes
0, 30, 60, 80, 111 mM
NDr
±
SCE could not be scored without S9
mix (no M2 metaphases observed).
With S9 mix, weak induction of
SCEs was observed. Highest
tolerated dose was 111 mM for cells
to undergo mitosis.
Goggelmann et al.
(1988)
SCE
CHO cells
160-5,000 (ig/mL
—
—
2-Nitropropane did not induce SCEs
with or without metabolic activation.
Gallowav et al.
(1987)
MN
Wistar rat primary hepatocytes (male)
0-0.0015 mol/L
+
NDr
Significant dose-dependent increase
in micronucleus formation.
Muller-Te gethoff
et al. (1995)
35
2-Nitropropane
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
MN
Rat hepatoma cell lines H4IIEC3/G .
2sFou, and C2Rev7
0.3-10 mM
24 hr

+
Cells were pretreated with
dexamethasone (an inducer of
liver-specific CYP450 forms).
Frequency of MN was not altered
without dexamethasone treatment.
With dexamethasone pretreatment,
there was an increase in frequency of
MN.
Roscher et al.
(1990)
MN
Chinese hamster lung V79 cells
0,2.5, 5 mM

NDr
2-Nitropropane did not affect the
frequencies of MN or abnormal
nuclei at concentrations up to 5 mM
and did not affect the mitotic index
(data not shown).
Haas-Jobelius et
al. (1991)
MN
Chinese hamster lung V79 cells
0.3-10 mM
3 hr
-
NDr
No increase in MN.
Roscher et al.
(1990)
MN
V7 9 -hC YP2E1 -hSULTl A1 cells
(cells express human CYP2E1 and
human SULT1A1)
0, 1, 3, 5mM
+
NDr
MN tests done in the presence of
modulators: pentachlorophenol, a
specific inhibitor of SULT1 Al, or
1-aminobenzotriazole, a specific
inhibitor of CYP2E1.
Increased frequencies of
micronucleated and multinucleated
cells in the presence of
1-aminobenzotriazole but not
pentachlorophenol. Mild
dose-dependent cytotoxicity.
Dene et al. (2011)

UDS
Human primary hepatocytes
(4 M, 2 F)
0,0.01,0.1, l.Ommol
±
NDr
Minimal induction of UDS.
Davies et al.
(1993)
36
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
UDS
Human diploid fibroblasts
0-5,000 ng/mL
3 hr
—
NDr
No increase in UDS.
McGregor (1981)
UDS
Wistar rat primary hepatocytes
0,0.01,0.1, l.Ommol
+
NDr
Marked induction of UDS at
0.1 mmol.
Davies et al.
(1993)
UDS
F344 rat primary hepatocytes (M)
10 to 10 3 M/plate
+
NDr
2-Nitropropane was toxic at 10 3 M.
2-Nitropropane induced UDS at
concentrations of 10 s and 10 4 M.
Fialaet al. (1995)
UDS
Rat primary hepatocytes
0, 0.25, 6.25 mM
+
NDr
2-Nitropropane induced UDS.
Kohl et al. (1994)
UDS
BALB/c mouse primary hepatocytes
0,0.01,0.1, l.Ommol
±
NDr
Minimal induction of UDS.
Davies et al.
(1993)
DNA repair
synthesis
Human cell lines (W138, NCI-H322,
A549, Hep2)
10 mM
—
NDr
No evidence of increased DNA repair
synthesis.
Andrae et al.
(1988)
DNA repair
synthesis
Rat hepatocytes (208F, LLC-WRC
256)
10 mM
+
NDr
Increased DNA repair synthesis.
Andrae et al.
(1988)
DNA repair
synthesis
Rat hepatocytes
0, 1, 3 mM
+
NDr
Increased DNA repair synthesis.
Haas-Jobelius et
al. (1991)
DNA repair
synthesis
Rat hepatocytes
1 x 10-6 M
+
NDr
Increased DNA repair synthesis in
hepatocytes from adult male F344
rats.
Williams et al.
(1982)
37
2-Nitropropane
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
DNA repair
synthesis
Rat hepatoma cell line (2sFou)
5, 10 mM
±
NDr
Cells were treated with either
2-nitropropane or propane 2-nitronate
(anionic form of 2-nitropropane).
2-Nitropropane was shown to release
nitrite into incubation medium at a
lesser rate than propane 2-nitronate.
2-Nitropropane was weakly active for
the induction of DNA repair synthesis
while propane 2-nitronate had a
marked induction of DNA repair
synthesis, suggesting propane
2-nitronate is oxidized by the liver to
produce DNA damage via nitronate
formation.
Dalke and Andrae
(1992)
DNA repair
synthesis
Rat hepatoma cell lines (2sFou,
C2Rev7)
0.3-10 mM
24 hr
±
NDr
Weakly induced DNA repair
synthesis.
Roscher et al.
(1990)
DNA repair
synthesis
Mouse 3T3-NIH cells
10 mM
—
NDr
No evidence of increased DNA repair
synthesis.
Andrae et al.
(1988)
DNA repair
synthesis
Chinese hamster lung V79 cells
0, 1, 3, 10 mM
—
NDr
No evidence of increased DNA repair
synthesis.
Andrae et al.
(1999)
DNA repair
synthesis
Chinese hamster lung V79-rPST-IV
and V79-rSTlCl cells (cells express
rat hepatic SULT1A1 or SULT1C1)
0,0.3, 1,3, 10 mM
+
NDr
2- to 4-fold increase in DNA repair
synthesis with exposure.
Andrae et al.
(1999)
DNA repair
synthesis
Chinese hamster cell lines
(V79, CHO)
10 mM
—
NDr
No evidence of increased DNA repair
synthesis.
Andrae et al.
(1988)
DNA repair
synthesis
Chinese hamster lung V79 cells
0.3-10 mM
24 hr
—
NDr
No evidence of increased DNA repair
synthesis.
Roscher et al.
(1990)
38
2-Nitropropane
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Genotoxicity studies—mammalian species-in vivo
Dominant
lethal
mutations
Male CD rats were exposed to
2-nitropropane via inhalation for 5 d
(7 hr/d) and mated to unexposed
females; endpoints examined
included pregnancy frequency,
number of corpora lutea and
implantation, and frequency of early
and late fetal death
0, 25, 200 ppm
+
NA
75% reduction in pregnancy
frequency at 200 ppm; decreased
frequency of live implantations at
200 ppm
McGregor (1981)
Mutations
(lad assay)
Male C57BL/6 mice were exposed
once to 2-nitropropane via i.p.
injection in olive oil and sacrificed
14 d later; liver tissue was examined
for lad transgene mutations
frequency
0, 100 mg/kg
+
NA
2.6-fold increase in mutation
frequency of the lad transgene.
Cabelof et al.
(2002)
CA (bone
marrow)
Male and female CD rats were
exposed to 2-nitropropane via
inhalation for 1 or 5 d (7 hr/d); bone
marrow was evaluated for CAs
0, 25, 200 ppm

NA
No significant induction of CAs at 1
or 5 d.
McGregor (1981)
MN (liver)
Male S-D rats (5-8/group) were
exposed once to 2-nitropropane via
gavage in water; 3 d later, rats were
given single oral dose of
4-acetylaminofluorene; liver tissue
was evaluated for MN 2 d after
4-acetylaminofluorene exposure using
both suspension and coverslip
methods
0, 25, 50, 75,
300 mg/kg
+
NA
Suspension method: 2- to 4-fold
increase in MN at all doses;
significant at all doses except
75 mg/kg.
Coverslip method: 1.6- to 4-fold
increase in MN at all doses;
significant at 50 and 300 mg/kg only.
George et al.
(1989)
39
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
MN (liver)
Male Crl:CD (SD) rats were
administered 2-nitropropane via
gavage in water for 14 or 28 d; rats
were sacrificed 24 hr after final dose;
liver tissue was evaluated for MN
0, 5, 20, 40 mg/kg-d
+
NA
Significant increases in hepatic MN
in both 14- and 28-d treated rats
Kawakami et al.
(2015)
MN (bone
marrow)
Male S-D rats (number/group not
reported) were exposed once to
2-nitropropane via gavage in water;
bone marrow was evaluated for MN
24-48 hr after exposure
0, 50, 100, 300 mg/kg
(oral)

NA
No significant induction of MN at
any dose. Decreased survival
observed at 300 mg/kg (6/11 died
within 24 hr).
George et al.
(1989)
MN (bone
marrow)
Male Crl:CD (SD) rats were
administered 2-nitropropane via
gavage in water for 14 or 28 d; rats
were sacrificed 24 hr after final dose;
bone marrow was evaluated for MN
0, 5, 20, 40 mg/kg-d

NA
No significant induction of MN at
after 14 or 28 d.
Kawakami et al.
(2015)
MN (bone
marrow)
Male and female CD-I mice were
orally administered 2 daily doses and
sacrificed 6 hr after second dose;
bone marrow was evaluated for MN
0,0.1,0.2,
0.3 mL/kg-d (0, 100,
200, 300 mg/kg-d)

NA
No significant induction of MN at
any dose.
Hite and Skeees
(1979)
MN (bone
marrow)
Male and female
(101/E1 x CeH/El)Fl mice were
exposed once to 2-nitropropane via
i.p. injection; mice were sacrificed at
intervals 18-120 hr after exposure;
bone marrow was evaluated for MN
0, 100, 200,
300 mg/kg

NA
No significant induction of MN at
any dose.
Kliesch and Adler
(1987)
DNA damage
(comet assay)
Male Wistar rats were exposed once
to 2-nitropropane via i.p. injection in
olive oil and sacrificed 24 hr later;
bone marrow cells were assessed for
DNA damage
0, 100 mg/kg
+
NA
8-fold increase in average tail length,
indicating DNA damage.
Dene et al. (1997)
40
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
DNA damage
(alkaline
elution assay)
Male S-D rats were exposed once to
2-nitropropane via gavage in distilled
water; DNA fragmentation was
determined in liver, lung, bone
marrow, kidney, and brain at intervals
of 1-36 hr post exposure (4-9 rats
per time point)
0, 0.5, 2, 8 mmol/kg
(0, 40, 200,
700 mg/kg)
+
(liver, bone
marrow)
(kidney, lung,
brain)
NA
Significant increases in DNA
fragmentation in liver (2- to 4-fold)
and bone marrow (1.2- to 1.3-fold).
DNA fragmentation was not induced
in kidney, lung, or brain.
Robbiano et al.
(1991)
DNA damage
(comet assay)
Male wild-type C57BL/6 and fi-pol
C57BL/6 mice were exposed once to
2-nitropropane via i.p. injection in
olive oil and sacrificed 24 hr later;
liver tissue was examined for SSB;
(3-pol (DNA polymerase (3) is
associated with repair synthesis in
short-patch BER
0, 100 mg/kg
+
NA
Number of SSBs increased by 4- to
5-fold; the increase was greater in
P-po^ C57BL/6 mice.
Other indicators of DNA damage
included an increase in p53 protein
levels; the increase was greater in
fi-pol C57BL/6 mice.
Cabelof et al.
(2002)
DNA damage
Young (4-6 mo) and aged
(24-28 mo) mice were exposed to
2-nitropropane via i.p. injection in
olive oil; liver tissue was examined
for 3'OH-containing DNA strand
breaks
0, 100 mg/kg
+
(young)
(aged)
NA
Statistically significant increase
(~2-fold) in 3'OH groups in DNA
from young mice, compared with
control.
Slight (-20%), but significant,
decrease in 3'OH groups in DNA
from aged mice, compared with
control.
Cabelof et al.
(2006)
DNA repair
(BrdU
density-shift)
Male and female Wistar rats were
exposed once to 2-nitropropane via
i.p. injection in olive oil; rats were
sacrificed 4 hr later and liver tissue
was examined for DNA repair (BrdU
incorporation)
0, 20, 40, 60,
80 mg/kg
+
NA
DNA repair increased up to 4-fold in
males and 3-fold in females.
Andrae et al.
(1988)
41
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
DNA repair
(BER)
Male wild-type C57BL/6 and fi-pol
C57BL/6 mice were exposed once to
2-nitropropane via i.p. injection in
olive oil and sacrificed 24 hr later;
liver tissue was examined for BER;
B-pol (DNA polymerase (3) is
associated with repair synthesis in
short-patch BER
0, 100 mg/kg
+
NA
Number of BERs increased 4- to
5-fold; the increase was greater in
fi-pol C57BL/6 mice.
Cabelof et al.
(2002)
UDS
Male S-D rats were exposed once to
2-nitropropane via gavage in water;
UDS was evaluated in bone marrow
14-16 hr after exposure
0, 25, 50, 75,
100 mg/kg
+
NA
2-Nitropropane induced UDS at
>50 mg/kg.
George et al.
(1989)
Oxidative
DNA damage
Male S-D rats were exposed once to
2-nitropropane via i.p. injection in
Emulphor-620:H2O (1:4 v/v); rats
were sacrificed 4 hr later; liver DNA
and RNA was evaluated for 8-OHdG
levels
0, 1.12 mmol/kg
(100 mg/kg)
+
NA
Significant increases in 8-OHdG in
hepatic DNA and RNA. There was
also formation of unknown moieties
of DX1 (DNA), and RX1 and RX2
(RNA).
Conawav et al.
(1991b)
Oxidative
DNA damage
Male F344 rats were exposed once to
2-nitropropane via i.p. injection in
corn oil; rats were sacrificed 6 hr
later; liver DNA was evaluated for
8-OHdG levels
0, 100 mg/kg
+
NA
12-fold increase in 8-OHdG in
hepatic DNA. There was also
formation of unknown moieties in
DNA(DXl).
Dahlhaus and
Anoel (1993)
Oxidative
DNA damage
Male Wistar rats were exposed once
to 2-nitropropane via i.p. injection in
olive oil and sacrificed 24 hr later;
bone marrow cells were assessed for
8-oxodG levels
0, 100 mg/kg
+
NA
5-fold increase in 8-OHdG levels in
bone marrow DNA.
Dene et al. (1997)
42
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Oxidative
DNA damage
Male S-D rats were exposed once to
2-nitropropane via i.p. injection in
Emulphor-620:H2O (1:4 v/v); rats
were sacrificed 6 hr later; liver DNA
and RNA were evaluated for 8-OHdG
levels
0, 100 mg/kg
+
NA
Significant 3.6- and 11-fold increases
in 8-OHdG in hepatic DNA and
RNA, respectively, in treated rats.
There was also formation of unknown
moieties of DX1 (DNA), andRXl
and RX2 (RNA).
Fialaet al. (1989)
Oxidative
DNA damage
Male S-D rats were exposed once to
2-nitropropane via i.p. injection in
Emulphor-620:H2O (1:4 v/v); rats
were sacrificed 6, 18, or 42 hr later;
liver DNA was evaluated for 8-O-dG
and 8-A-dG and RNA was evaluated
for 8-O-GR and 8-A-GR
0, 1.12 mmol/kg (0,
100 mg/kg)
+
NA
Significant increases in 8-O-dG in
liver DNA and 8-O-GR in liver RNA.
There were no significant increases in
8-A-GR in RNA or 8-A-dG in DNA.
There were small increases in
unknown moieties of DX1 (DNA)
and (RNA).
Fialaet al. (1993)
Oxidative
DNA damage
Male and female S-D rats were
exposed once to 2-nitropropane via
i.p. injection in Emulphor-620:H2O
(1:4 v/v); rats were sacrificed 6 or
18 hr later; liver and kidney DNA and
RNA were evaluated for 8-OHdG and
8-OH-GR levels, respectively
0, 1.12 mmol/kg (0,
100 mg/kg)
+
(liver)
(kidney)
NA
Increased 8-OHdG in liver DNA and
8-OH-GR in liver RNA in males 6
and 18 hr after treatment, and in
females 6 hr after treatment. Induced
unknown moieties in liver DNA
(DX1) and RNA (RX1, RX2); the
increases was higher in males than
females.
No evidence of oxidative DNA or
RNA damage in kidneys.
Guo et al. (1990)
Oxidative
DNA damage
Male F344 rats were exposed once to
2-nitropropane via i.p. injection in a
0.9% NaCl solution; animals were
sacrificed 6 or 15 hr after exposure;
liver DNA was evaluated for 8-OHdG
levels
0, 100 mg/kg
+
NA
Significant increase in 8-OHdG in
liver DNA at both time points.
Haseeawa et al.
(1995)
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Oxidative
DNA damage
Male S-D and F344 rats were exposed
once to 2-nitropropane via i.p.
injection in Emulphor-620:H2O
(1:4 v/v); rats were sacrificed 6 hr
later; liver DNA and RNA were
evaluated for 8-OHdG and 8-OH-GR
levels, respectively
0, 1.12 mmol/kg (0,
100 mg/kg)
+
NA
Increased 8-OHdG in liver DNA and
8-OH-GR in liver RNA in both rat
strains. Induced unknown moieties in
liver DNA (DX1) and RNA (RX1,
RX2) in both strains.
Hussain et al.
(1990)
Oxidative
DNA damage
Male F344 rats were exposed to
2-nitropropane via gavage in water
for 2 wk (3 d/wk); rats were
sacrificed 4 hr after final dose; liver
DNA was evaluated for 8-OHdG
levels
0, 60, 90/120 mg/kg-d
(high-dose was a total
of 2 doses of
90 mg/kg-d and
4 doses of
120 mg/kg-d; TWA
of 110 mg/kg-d)
+
NA
1.8- to 2.9-fold increase in 8-OHdG
levels in treated rats.
Pretreatment with antioxidants
partially protected DNA from
oxidative damage.
Sai et al. (1998)
Oxidative
DNA damage
Male F344 rats were exposed once to
2-nitropropane via i.p. injection in
Emulphor-620:H2O (1:4 v/v); rats
were sacrificed 18 hr later; liver DNA
and RNA were evaluated for 8-A-dG
and 8-A-GR levels, respectively
0, 100 mg/kg
+
NA
Increased levels of 8-A-dG in liver
DNA and 8-A-GR in liver RNA.
Sodutn et al.
(1993)
Oxidative
DNA damage
Male F344 rats were exposed once to
2-nitropropane via i.p. injection in a
0.9% NaCl solution containing 0.1%
Tween 20; animals were sacrificed
6 hr after exposure; liver DNA was
evaluated for 8-OHdG levels
0, 100 mg/kg
+
NA
1.7-fold increase in liver DNA
8-OHdG levels. Induced unknown
moieties in liver DNA (DX1).
Pretreatment with antioxidants
partially protected DNA from
oxidative damage.
Takaei et al.
(1995)
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Oxidative
DNA damage
Male wild-type C57BL/6 and fi-pol
C57BL/6 mice were exposed once to
2-nitropropane via i.p. injection in
olive oil and sacrificed 24 hr later;
liver tissue was examined for
8-OHdG levels; DNA polymerase (3 is
associated with repair synthesis in
short-patch BER
0, 100 mg/kg (i.p.)
+
NA
4- to 5-fold increase in 8-OHdG
levels in both wild-type and fi-pol
mice.
Cabelof et al.
(2002)
Oxidative
DNA damage
Male New Zealand White rabbits
were exposed once to 2-nitropropane
via i.p. injection in
Emulphor-620:H2O (1:4 v/v); rabbits
were sacrificed 6, 18, or 42 hr later;
liver DNA was evaluated for 8-O-dG
and 8-A-dG and RNA was evaluated
for 8-O-GR and 8-A-GR
0, 1.12 mmol/kg (0,
100 mg/kg)

NA
No evidence of oxidative DNA or
RNA damage.
Fialaet al. (1993)
45
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Table 4A. Summary of 2-Nitropropane Genotoxicity
Endpoint
Test System
Doses/
Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
References
Genotoxicity studies—invertebrates-in vivo
Sex-linked
recessive lethal
Drosophila melanogaster males were
exposed to 2-nitropropane via
inhalation for 4.5 hr prior to mating
with unexposed females
700 ppm

NA
No increase in frequencies of
sex-linked recessive lethal mutations.
McGregor (1981)
Sex-linked
recessive lethal
Drosophila sp. males were exposed to
2-nitropropane via feeding (72 hr) or
single injection prior to mating with
unexposed females
Feeding: 0,
1,000 ppm; Injection:
0, 5,000 ppm

NA
No increase in frequencies of
sex-linked recessive lethal mutations.
Zimmering et al.
(1985)
Mitotic
recombination
(white/white+
eye mosaic
bioassay)
Drosophila sp. larvae were exposed
to 2-nitropropane via feeding for
15 min
0, 5mM

NA
No evidence of increased mitotic
recombination.
Vogel and Nivard
(1993)
a+ = positive; ± = weakly positive; - = negative.
8-OHdG = 8-hydroxydeoxyguanosine; 8-A-dG = 8-aminodeoxyguanosine; 8-A-GR = 8-aminoguanosine; 8-O-dG = 8-oxydeoxyguanosine; 8-O-GR = 8-oxyguanosine;
8-OH-GR = 8-hydroxyguanosine; 8-oxodG = 8-oxo-7,8-dihydro-2'-deoxyguanosine; BER = base excision repair; BrdU = bromodeoxyuridine; CA = chromosomal
aberration; CHO = Chinese hamster ovary; DNA = deoxyribonucleic acid; F = female(s); i.p. = intraperitoneal; M = male(s); MN = micronuclei; NA = not applicable;
NaCl = sodium chloride; NDr = not determined; NR = nitroreductase; RNA = ribonucleic acid; SCE = sister chromatid exchange; S-D = Sprague-Dawley; SSB = single
stranded break; TG = 6-thioguanine; TWA = time-weighted average; UDS = unscheduled DNA synthesis.
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Mutagenicity
2-Nitropropane is mutagenic in bacterial and mammalian cells in vitro. It is a
well-established mutagen in various Salmonella typhimurium strains both with and without
metabolic activation (Kohl et al.. 1994; Conawav et al.. 1991a; Goggetmann et al.. 1988; Fiala et
al., 1987a; Lofroth et al., 1986; Ha worth et al.. 1983; Speck et al.. 1982; Hite and Skeggs, 1979;
Litton Bionetics, 1977a, b; Russell and Krahn, 1977). 2-Nitropropane is also mutagenic in Chinese
hamster lung V79 cells and rat hepatoma H4IIEC3/G-cells (Haas-Jobelius et al, 1991; Roscher et
al.. 1990). It is often used as a positive control in mutagenicity assays or to test efficacy of potential
antimutagens (Nikolic et al.. 2012; Staikovic et al.. 2007; Deng et al.. 1998; Weisburger et al.. 1996;
Adachi et al.. 1993; Sakai and Uchida. 1992); these positive control studies were not included in
Table 4 A. However, 2-nitropropane was not mutagenic to Saccharomyces cerevisiae D4 strain with
or without metabolic activation (Litton Bionetics. 1977b).
In vivo, 2-nitropropane has been associated with dominant lethal mutation in rats following
inhalation exposure to 200 ppm for 5 days (7 hours/day) (McGregor. 1981) and lacl mutations in
mouse liver tissue following a single i.p. injection exposure (Cabelof et al.. 2002). 2-Nitropropane
was not associated with sex-linked recessive lethal mutations or mitotic recombination in
Drosophila species (Vogel and Nivard. 1993; Zimmcring et al.. 1985; McGregor, 1981).
Clastogenicity
2-Nitropropane is capable of inducing clastogenic effects in vitro in human and rat cells, and
data suggest that reactive metabolite(s) may contribute to these findings. Increased frequency of
chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs) have been reported with
and without metabolic activation in primary human lymphocytes in one study (Bauchinger et al.,
1987), but only with external activation in another (Goggetmann et al., 1988). Micronuclei (MN)
were induced in rat hepatocytes without external metabolic activation and in rat hepatoma cells
pretreated with the cytochrome P450 (CYP450) inducer, dexamethasone (Muller-Tegethoff et al ..
1995; Roscher et al.. 1990). 2-Nitropropane did not cause CAs or SCEs in Chinese hamster ovary
(CHO) cells with or without metabolic activation (Galloway et al.. 1987). Similarly, 2-nitropropane
did not cause MN in Chinese hamster V79 cells without external metabolic activation; these cells
were not tested with metabolic activation because they have the intrinsic capability of reducing and
oxidizing 2-nitropropane (Haas-Jobelius et al., 1991; Roscher et al.. 1990). However, MN were
observed in Chinese hamster V79 cells transfected to express human CYP2E1 and SULT1 Al (Deng
et at.. 2011).
In vivo, 2-nitropropane is clastogenic to liver tissue, inducing hepatic MN in rats following
single oral exposure to doses >25 mg/kg (George et al.. 1989) or repeated oral exposure to doses
>5 mg/kg-day (Kawakami et al.. 2015). However, MN were not induced in bone marrow under the
same conditions in rats (Kawakami et al.. 2015; George et al.. 1989) or in mice at oral or i.p. doses
up to 300 mg/kg-day (Kliesch and Adler. 1987; Hite and Skeggs, 1979). Additionally, CAs were
not induced in rat bone marrow following inhalation exposure for 1 or 5 days to concentrations up
to 200 ppm (7 hours/day) (McGregor, 1981).
DNA Damage and Repair
DNA damage was observed following in vitro exposure to 2-nitropropane in a
S. typhimurium strain transfected with the human sulfotransferase SULT1A2; DNA damage was not
observed in the parent strain (no human SULT) or strains expressing SULT1 Al or 1 A3 (Oda et al..
2012). Unscheduled DNA synthesis (UDS) was weakly induced in human primary hepatocytes
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exposed to 2-nitropropane in vitro without external metabolic activation (Davies et al.. 1993).
However, UDS was not induced in human diploid fibroblasts exposed to 2-nitropropane without
metabolic activation (McGregor. 198 1). and DNA repair synthesis was not induced in several
human cell lines (W138, NCI-H322, A549, Hep2) in the absence of metabolic activation (Andrae et
al., 1988). In rat hepatocytes, UDS and DNA repair synthesis were con si stently observed in rat
hepatocytes exposed to 2-nitropropane in vitro without external metabolic activation (Fiala et al..
1995; Kohl et al.. 1994; Davies et al.. 1993; Haas-Jobelius et al.. 1991; Andrae et al.. 1988;
Williams et al.. 1982); weak induction of DNA repair synthesis was also observed in rat hepatoma
cell lines without metabolic activation (Dalke and Andrae. 1992; Rose her et al.. 1990). In other
species, in vitro studies of 2-nitropropane without metabolic activation induced a weak induction of
UDS in mouse primary hepatocytes (Davies et al.. 1993) but no evidence of increased DNA repair
synthesis in mouse 3T3-NIH cells, CHO cells, or Chinese hamster V79 cells (Roscher et al.. 1990;
Andrae et al.. 1988). However, 2-nitropropane induced DNA repair synthesis in V79 cells that were
transfected to express rat hepatic SULT1 Al or 1C1 (Andrae et al.. 1999).
In vivo studies consistently report evidence of DNA damage and/or repair in hepatic tissue
of rats and mice following single oral doses or i.p. injections of 2-nitropropane, including DNA
fragmentation (Robbiano et al.. 1991). single strand breaks (Cabelof et al.. 2006; Cabelof et al..
2002). DNA repair (Cabelof et al.. 2002; Andrae et al.. 1988). UDS (George et al.. 1989). and
evidence of oxidative DNA damage (Cabelof et al.. 2002; Sai et al.. 1998; Hasegawa et al.. 1995;
Takagi et al.. 1995; Dahlhaus and Appel. 1993; Fiala et al.. 1993; Sodum et al.. 1993; Conaway et
al.. 1991b; Guo et al.. 1990; Hussain et al, 1990; Fiala et al.. 1989). DNA damage has also been
reported in rat bone marrow (Deng et al .. 1997; Robbiano et al.. 1991). but not kidney, lung, or
brain tissue (Robbiano et al.. 1991; Guo et al.. 1990). However, there was no evidence of oxidative
DNA damage in rabbits exposed once to 2-nitropropane via i.p. injection (Fiala et al.. 1993).
Supporting Human Toxicity Studies
Several cases of acute hepatic failure have been reported in workers exposed to high
concentrations of 2-nitropropane (and other chemicals) over 1-3 work days without proper personal
protective equipment (e.g., respirators, gloves) and/or ventilation; most reported cases were lethal
(Harrison et al.. 1987; Harrison et al.. 1985; NIOSH. 1985; Rondia. 1979; Hine et al.. 1978). Signs
and symptoms associated with exposure included nausea, vomiting, diarrhea, anorexia, weakness,
dizziness, dyspnea, ataxia, chest pain, abdominal pain, jaundice, and scleral icterus. Common
laboratory findings included elevated serum enzymes (ALP, ALT, AST, lactate dehydrogenase
[LDH]) and hyperbilirubinemia. Additional findings in one or more lethal cases included
gastrointestinal bleeding, arrhythmia, cardiac arrest, pulmonary edema, renal failure, lesions in the
liver and kidney, and metabolic acidosis (Harrison et al.. 1987; Harrison et al.. 1985; Hine et al..
1978). Actual exposure levels were not available in these cases; however, serum concentrations of
8.5-13 |ig/mL were reported in two workers after exposure to an epoxy resin coating containing
2-nitropropane in an unventilated room over 3 work days (Harrison et al.. 1987; Harrison et al..
1985). The worker with the higher serum level died; the second worker survived. Based on
reported serum concentrations and pharmacokinetic studies in rats, Harrison et al. (1987) estimated
that the workers had exposure levels of >600 ppm.
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Supporting Animal Toxicity Studies
A number of acute and short-term-duration studies, inadequately reported
sub chronic-duration animal toxicity studies, and studies via other routes (e.g., injection) were
identified. Together, these studies support that the liver is the main target of 2-nitropropane toxicity
(see Table 4B for additional details).
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Supporting evidence—noncancer effects in animals following oral exposure
Acute (oral)
The LD5o was determined in groups of rats.
No further details were provided.
2-Nitropropane classified as slightly
toxic (LD50 value of 500-5,000 mg/kg).
Rat LD50 = 500 mg/kg
Kennedy and
Graeoel C199D
Acute (oral)
Groups of male Wistar rats (5/group) were
given oral doses of 0 or 120 mg/kg of
2-nitropropane in canola oil once, with or
without pretreatment with the antioxidant
(NapSe)2 (50 mg/kg). Endpoints evaluated
included serum chemistry (AST, ALT,
creatinine, plasma urea), liver histology, and
markers of oxidative stress in the liver
(TBARS, NPSH, ascorbic acid, catalase,
5-ALA-D activity).
Significant findings in animals exposed
to 2-nitropropane alone included a
2-fold increase in serum AST and ALT,
altered markers of oxidative stress
(increased TBARS and NPSH,
decreased 5-ALA-D activity), and
inflammatory cell infiltration in the
liver.
Pretreatment with (NapSe)2 prevented
changes in serum AST and ALT,
hepatic TBARS and 5-ALA-D, and
liver histology.
The only administered dose of
120 mg/kg is a LOAEL (liver
effects)
Hepatic alterations appear to be
mediated, at least in part, via
oxidative stress
Ibrahim et al.
(2010)
Acute (oral)
Groups of male Wistar rats (number per group
is not specified) were given oral doses of 0 or
120 mg/kg 2-nitropropane in canola oil, with
or without pretreatment with the antioxidant,
BPD (50 mg/kg). Endpoints evaluated
included serum chemistry (AST, ALT, ALP,
LDH), liver histology, and markers of lipid
peroxidation and oxidative stress in the liver
(TBARS, MDA, ascorbic acid, catalase,
5-ALA-D activity, GST, GPx, and GSH
reductase).
Significant findings in animals exposed
to 2-nitropropane alone included a 1.5-
to 2-fold increase in serum ALT, AST,
ALP, and LDH; altered markers of lipid
peroxidation and oxidative stress
(increased TBARS and MDA,
decreased 5-ALA-D, GSH, GPx, GR,
and GST); and inflammatory cell
infiltration in the liver.
Pretreatment with BPD offered partial
protection against all the liver endpoints
tested.
The only administered dose of
120 mg/kg is a LOAEL (liver
effects)
Hepatic alterations appear to be
mediated, at least in part, via
oxidative stress
Wilhelm et al.
(2011)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Acute (oral)
Groups of male Wistar rats (6-8/group) were
given oral doses of 0 or 100 mg/kg
2-nitropropane in canola oil, with or without
pretreatment with the antioxidant 3-ASP
(25 mg/kg). Endpoints evaluated included
serum chemistry (AST, ALT), liver histology,
and markers of lipid peroxidation and
oxidative stress in the liver (TB ARS, MDA,
ascorbic acid, catalase, 5-ALA-D activity).
Significant findings in animals exposed
to 2-nitropropane alone included a
2-3-fold increase in serum AST and
ALT, altered markers of lipid
peroxidation and oxidative stress
(increased TB ARS and MDA,
decreased 5-ALA-D activity), and
histopathological lesions in the liver
(inflammatory cells infiltration in the
liver and loss of cellular architecture).
There was no indication of
2-nitropropane	induced liver damage
when animals were pretreated with
3-ASP.
The only administered dose of
100 mg/kg is a LOAEL (liver
effects)
Hepatic alterations appear to be
mediated, at least in part, via
oxidative stress
Wilhelm et al.
(2010)
Acute (oral)
The LD5o was determined in groups of mice.
No further details were provided.
ND
Mouse LD5o (95% CI) = 0.400
(0.352-0.424) mL/kg = 392
(346-416) mg/kg
Hite and Skeggs
(1979)
Acute (oral)
The LD5o was determined in groups of rabbits
exposed via gavage. Animals were observed
for 2-3 hr following administration.
ND
Rabbit LD50 = 500-750 mg/kg
Machle et al.
(1940)
Supporting evidence—noncancer effects in animals following inhalation exposure
Acute (inhalation)
The ALC, or the concentration at which
mortality was first observed following a 5-hr
exposure, was determined in rats. No further
details were provided.
2-Nitropropane was classified as
slightly toxic (ALC value of
500-5,000 ppm).
Rat ALC (5-hr) = 1,513 ppm
Kennedy and
Graeoel Q99D
Acute (inhalation)
The 6-hr LC5o was determined in groups of
rats. The highest concentration used was
580 ppm No further details were provided.
ND
Rat LC50 (6-hr):
Male: 400 ppm
Female: >580 ppm
Lewis et al.
(1979)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Acute (inhalation)
The 1-, 2.25-, and 4.5-hr ALCs were
determined for cat, rat, rabbit, and guinea pig.
Endpoints included mortality, clinical signs,
body weight, hematology, and gross necropsy.
Clinical signs associated with "high"
exposure concentrations in all species
included dyspnea, cyanosis, prostration,
convulsions, and coma. Cats also
showed lacrimation, salivation, and
gastric regurgitation prior to death.
Slight decreases in weight were
observed, with transitory observations
in animals that survived. Exposure to
>2,353 ppm was associated with
widespread organ damage.
Methemoglobinemia and Heinz bodies
were observed in rabbits and cats.
CatALC:
1-hr: 2,353 ppm
2.25-hr: 1,148 ppm
4.5-hr: 714 ppm
Rat ALC:
1-hr: 3,865 ppm
2.25-hr: 2,633 ppm
4.5-hr: 1,513 ppm
Rabbit ALC:
1-hr: 9,523 ppm
2.25-hr: 4,313 ppm
4.5-hr: 2,381 ppm
Guinea pig ALC:
1-hr: NDr
2.25-hr: 9,607 ppm
4.5-hr: 4,622 ppm
Treon and Dutra
C1952)
Short-term (inhalation)
Lethality was reported in rats exposed to
328 ppm for a total of up to 17 exposures
(7 hr/d, 5 d/wk). The number of cats was not
reported; no controls were reported.
Endpoints included mortality, clinical signs,
body weight, hematology, and gross and
microscopic necropsy.
All cats died after 3-17 exposures.
Dyspnea was observed, and cats did not
gain weight. Heinz bodies and impaired
blood clotting were observed.
Histopathological changes included
parenchymal degeneration and focal
necrosis of the liver, slight to moderate
toxic degeneration of the heart and
kidney, pulmonary edema,
intra-alveolar hemorrhage, and
interstitial pneumonitis.
The only exposure level (328 ppm)
is an apparent FEL; however, the
study has numerous limitations,
including lack of control group and
inadequate study design and data
reporting
Treon and Dutra
C1952)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Short-term (inhalation)
Male S-D rats were exposed to 2-nitropropane
vapor concentrations of 0 or 100 ppm
(364 mg/m3), 7 hr/d for up to 4 d. Three
animals/group were sacrificed on D 1,2, and
4. Endpoints evaluated included serum
chemistry (ALP, AST), hepatic enzyme
activities (GST, GPx, GSH reductase), and
hepatic microsomal protein levels (CYP450,
cytochrome b> UDP-glucuronosyltransferase,
MDA).
Significant findings in exposed animals
included decreased CYP450 (all
collection days), increased
UDP-glucuronosyltransferase and total
GSH (collection Day 4), and increased
GST (all collection days).
Endpoints evaluated were
inadequate to identify a NOAEL or
LOAEL. The study authors
indicated that the effects of
2-nitropropane exposure on
microsomal CYP450 indicate that
reactive intermediates may be
formed
Haas-Jobelius et
al. (1992)
Subchronic (inhalation)
In a lethality study, 2 rats, 2 guinea pigs,
3 rabbits, and 1 monkey were exposed to
328 ppm for a total of up to 130 exposures
(7 hr/exposure) over the course of 199 d and
2 cats, 1 rat, 4 rabbits, 2 guinea pigs, and
1 monkey were exposed to 83 ppm for a total
of 130 exposures (7 hr/exposure) over the
course of 191 d. Endpoints included
mortality, clinical signs, body weight, and
gross and microscopic necropsy. No control
animals were reported.
The only reported deaths were 2 rabbits
that died on D 95 and 97 of infection
unrelated to treatment. The monkey
was only exposed for 100 d (no reason
given). No signs of intoxication or
body weight effects were observed. All
tissues were normal.
The exposure level of 328 ppm is
an apparent NOAEL for all species;
however, the study has numerous
limitations, including small animal
numbers, lack of control group, and
inadequate study design and data
reporting
Treon and Dutra
(1952)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Supporting evidence—noncancer effects in animals following intraperitoneal exposure
Acute (i.p.)
Groups of male albino Wistar rats
(n = 6/group) were exposed to 0 or 100 mg/kg
of 2-nitropropane via i.p injection in corn oil,
with or without administration of the
antioxidant (PhSe)2 (10 |imol/kg) 24 hr later.
Endpoints evaluated included serum chemistry
(plasma urea, creatinine, GGT, AST, ALT),
liver weight and histology, and markers of
lipid peroxidation and oxidative stress in the
liver (superoxide dismutase and catalase
activities, ascorbic acid, and TBARS levels)
and kidney (MDA).
Significant findings in animals exposed
to 2-nitropropane alone included
increased serum urea, ALT, AST, and
GGT; altered markers of lipid
peroxidation and oxidative stress
(increased TBARS in both kidney and
liver and decreased in catalase activity);
and histopathological lesions in the liver
(severe swelling, lymphocytic
infiltration, and confluent necrosis in
the centrilobular zone). Liver weight
was not reported.
Postexposure treatment with (PhSe)2 led
to a decrease in hepatic effects
associated with 2-nitropropane
exposure.
The only administered dose of
100 mg/kg is a LOAEL (liver
effects)
Hepatic alterations appear to be
mediated, at least in part, via
oxidative stress
Borees et al.
(2006)
Acute (i.p.)
Groups of male albino Wistar rats
(n = 6/group) were exposed to 0 or 100 mg/kg
of 2-nitropropane via i.p injection in olive oil,
with or without administration of the
antioxidant (PhSe)2 (10 |imol/kg) 24 hr before
2-nitropropane exposure. Endpoints evaluated
included serum chemistry (plasma urea,
creatinine, GGT, AST, ALT), plasma AFP
(hepatic tumor marker), markers of lipid
peroxidation in the liver (TBARS), and gross
and microscopic liver histology.
Significant findings in animals exposed
to 2-nitropropane alone included
increased serum urea, ALT, GGT, and
AFP, increased TBARS, and hepatic
damage (moderate swelling and
degenerative alterations).
Pre-exposure treatment with (PhSe)2
resulted in a protective effect against
2-nitropropane induced liver toxicity.
The only administered dose of
100 mg/kg is a LOAEL (liver
effects)
Hepatic alterations appear to be
mediated, at least in part, via
oxidative stress
Borees et al.
(2005)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Acute (i.p.)
Groups of male S-D rats (10/group) were
administered 2-nitropropane at doses of 0 or
4 mmol/kg via i.p. injection in olive oil, with
or without administration of the antioxidant
melatonin (10 mg/kg) 30 min later. All rats
were sacrificed at 24 hr; 6/group were used to
evaluate hepatic cell proliferation (received
injection of thymidine 3H at 22 hr) and
4/group were used for examination of liver
and lung histology.
Histopathological changes in treated
rats included hepatic lesions (focal
necrosis, with diffuse vacuolar
degeneration, lymphocytic infiltration,
degenerated hepatic cells [apoptosis],
congestion of blood vessels) and lung
lesions (mucinous degeneration and
proliferation of the bronchial
epithelium, congestion of vessels and
interalveolar capillaries, hemorrhage
and edema of the bronchi). Increased
cell proliferation was observed in
treated rats.
Melatonin treatment reduced cell
proliferative effects of 2-nitropropane
and reversed histopathological changes
in liver and lung.
The only administered dose of
4 mmol/kg (356 mg/kg) is a
LOAEL (liver and lung effects)
Hepatic and pulmonary alterations
appear to be mediated, at least in
part, via oxidative stress
Hl-Sokkarv
(2002)

Acute (i.p.)
Groups of male F344 rats were exposed once
to 2-nitropropane at doses of 0 or 100 mg/kg
via i.p. injection in a 0.9% NaCl solution
containing 0.1% Tween 20, with or without
pretreatment with 2% green tea or with
concentrated tea extract in their drinking
water. Animals were sacrificed 6 or 15 hr
following the 2-nitropropane injection.
Endpoints evaluated included serum
biochemistry (AST, ALT, triglycerides, LDH),
hepatic biochemistry (TBARS, glycogen
content), and liver histology (15 hr only).
Significant findings in rats exposed to
2-nitropropane alone included increased
serum ALT and LDH and decreased
triglycerides at 6 hr after dosing. At
15 hr, animals treated with
2-nitropropane alone had decreased
TBARS and histopathological changes
in the liver (swelling and severe
degeneration of hepatocytes).
Green tea and concentrated tea extracts
had minimal impacts on
2-nitropropane-induced changes.
The only administered dose of
100 mg/kg is a LOAEL (liver
effects)
Hasegawa et al.
(1995)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Acute (i.p.)
Groups of male F344 rats (5-7/group) were
exposed once to 2-nitropropane at doses of 0
or 100 mg/kg via i.p. injection in 0.9% NaCl
solution containing 0.1% Tween 20, with or
without pretreatment with an antioxidant
(P-carotene, vitamin E, or ellagic acid). Liver
serum biochemistry (ALT, AST) was
evaluated.
Significant findings in rats exposed to
2-nitropropane alone included increased
serum ALT and AST.
Pretreatment with antioxidants did not
alter serum ALT and AST findings.
The only administered dose of
100 mg/kg is a LOAEL (liver
effects)
Takairi et al.
(1995)
Acute (i.p.)
Groups of male Wistar rats (n = 4-5/group)
were exposed once to 2-nitropropane at doses
of 0 or 50 mg/kg via i.p. injection in olive oil.
Groups of animals were sacrificed at 1, 4, and
24 hr after exposure. Endpoints evaluated
included serum biochemistry (ALT), liver
histology via electron microscopy, hepatic
biochemistry (GSH, GST, GPx, and
xenobiotic metabolic products), and brain
biochemistry (acid proteinase activity in the
cerebral homogenate, activities of
acetylcholine esterase and 2',3'-cyclic
nucleotide 3'-phosphohydrolase, and RNA and
protein content).
Significant hepatic findings in exposed
rats included increased serum ALT,
histopathological changes (lipid
accumulation, centrilobular necrosis,
degranulation of RER, proliferation of
SER), altered hepatic biochemistry
(elevated GSH and GPx, decreased
GST), and altered xenobiotic enzymes
(decreased CYP450, 7-ethoxycoumarin
O-deethylase, 7-ethoxyresorufin
O-deethylase; increased
NADPH-cytochrome c reductase,
UDP-glucuronosyltransferase, epoxide
hydratase).
Significant brain findings in exposed
rats included increased acetylcholine
esterase, decreased 2',3'-cyclic
nucleotide 3'-phosphohydrolase, and
decreased acid proteinase.
The only administered dose of
50 mg/kg is a LOAEL (liver
effects)
Observed findings are indicative of
lipid peroxidation
Zitting et al.
(1981)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Acute (i.p.)
Groups of male and female B ALB/c mice
(n = 5-12/sex/group per time point) were
exposed once to 2-nitropropane at doses of 0,
4.5, 6.7, or 9 mmol/kg via i.p. injection in
saline. Mice were sacrificed 24, 48, 72, or
96 hr after dosing. Endpoints included serum
biochemistry (SDH, ALT, AST) and liver
histology.
Significant serum biochemistry findings
in exposed animals included a mild
increase in SDH in females at
>4.5 mmol/kg, increased ALT and AST
in females at >6.7 mmol/kg, and
increased SDH, ALT, and AST in males
at 9 mmol/kg.
Significant histopathological findings in
females were observed at 9 mmol/kg
(severe periportal degeneration,
apoptosis, necrosis, hemorrhage, mild
proliferation of ductal type cells in
periportal region). Hepatic lesion
incidence in males was comparable to
controls.
A NOAEL of 4.5 mmol/kg
(400 mg/kg) and a LOAEL of
6.7 mmol/kg (600 mg/kg) are
identified (liver effects)
Daval et al.
(1989)
Reproductive/
Developmental (i.p.)
Groups of inseminated female S-D rats
(10-15/group) were administered
2-nitropropane at 0 or 170 mg/kg-d in corn oil
via i.p. injection on GDs 1-15. Dams were
sacrificed on GD 21. Endpoints evaluated
included maternal body weight, gross
examination of uterine contents and organs,
maternal organ weight and histology (brain,
heart, lungs, liver, spleen, kidneys, adrenals,
ovaries), and fetal endpoints (weight,
crown-to-rump length, sex, visceral and
skeletal examinations).
A significant increase in delayed fetal
development was observed (1- to 2-d
delay in heart development; no further
information provided). No other fetal
endpoints were altered with exposure.
No maternal toxicity was observed.
The only administered dose of
170 mg/kg-d is a LOAEL
(developmental effects)
Hardin et al.
(1981)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Supporting evidence—cancer effects in animals following exposure via any route
Subchronic (oral)
In an initiation-promotion study, 60 male
F344/DuCij rats were given a single i.p.
injection for the tumor initiator, DEN
(200 mg/kg). 2 wk after initiation, groups of
rats (15/group) were orally administered
2-nitropropane in corn oil at doses of 0,0.8, 4,
or 20 mg/kg-d for 6 wk (6 d/wk). Uninitiated
rats (6/group) were administered 0 or
20 mg/kg-d for 6 wk (6 d/wk). At the end of
the 3rd wk of 2-nitropropane exposure,
animals were subject to a partial hepatectomy.
Endpoints evaluated included clinical signs,
body weights, food consumption, liver
weights, and GST-P positive preneoplastic
foci.
A significant increase in GST-P positive
foci >0.2 mm was observed in rats
initiated with DEN and then treated
with 20 mg/kg-d of 2-nitropropane,
compared to rats initiated with DEN
only.
In rats exposed only to 2-nitropropane,
significant findings include a
19% increase in absolute liver weight, a
13% increase in relative liver weight,
and increased incidence of GST-P
positive foci <0.2 mm (no foci >0.2 mm
were observed).
The only administered dose of
20 mg/kg is a LOAEL (liver
effects)
2-Nitropropane is a tumor pro motor
under the conditions of this assay
Doi et al. (2011)
Short-term (inhalation)
In an initiation-promotion study, groups of
weanling S-D rats (6-12/sex/group) were
exposed to 2-nitropropane (initiation) at doses
of 0, 24, 40, 50, 80, 123, or 200 ppmfor 3 wk
(6 hr/d, 5 d/wk). 1 wk later, all animals were
given oral doses of the promoting agent,
Clphen A50, at doses of 10 mg/kg-d for 8 wk
(2 d/wk). 1 wk after final exposure, the rats
were sacrificed, and livers were removed and
evaluated for preneoplastic foci.
The 200-ppm exposure group was
discontinued due to high mortality
within a few days. No mortality or
signs of toxicity at lower
concentrations.
A dose-related increase in the number
of hepatic preneoplastic foci was
observed in both male and female rats.
The highest concentration tested
(200 ppm) is a FEL
2-Nitropropane was a tumor
initiator under the conditions of this
study
Denk et al.
(1990)
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Table 4B. Other Studies
Test3
Materials and Methods
Results
Conclusions
References
Short-term (i.p.)
In an initiation-promotion study, groups of
male weanling Wistar rats (8/group) were
given a total of 6 i.p. injections of
2-nitropropane at doses of 0, 25, 50, or
100 mg/kg-d in 2% Tween 20. Injections
were onD 14, 16, 18, 21, 23, and 25 of the
experiment. From the 42nd-56th d of the
experiment, all rats were exposed the
promotor 2-AAF at dietary concentrations of
50 ppm All rats were exposed to
phenobarbital (sodium salt) for an additional
2 wk following 2-AAF exposure. On D 49, all
rats were anaesthetized for a 2/3 partial
hepatectomy. All rats were sacrificed on D 70
of the experiment and liver tissue was
evaluated for GGT- and GST-positive
preneoplastic foci.
A dose-related increase in the number
of hepatic preneoplastic foci was
observed in exposed rats.
2-Nitropropane was a tumor
initiator under the conditions of this
study
Astorg et al.
Q994-)
"Acute = exposure for <24 hours (U.S. EPA, 2002b'): short term = repeated exposure for >24 hours <30 days (U.S. EPA, 2002b'): subchronic = repeated exposure for
>30 days <10% lifespan (>30 days up to approximately 90 days in typically used laboratory animal species) (U.S. EPA. 2002b') chronic = repeated exposure for
>10% lifespan for humans (more than approximately 90 days to 2 years in typically used laboratory animal species) (U.S. EPA. 2002b').
2-AAF = 2-acetylaminofluorene; 3-ASP = 3-alkynyl selenophene; 5-ALA-D = delta-aminolevulinic acid dehydratase; ALC = approximate lethal concentration;
AFP = alpha-fetoprotein; ALP = alkaline phosphatase; ALT = alanine aminotransferase; AST = aspartate aminotransferase;
BPD = (E)-2-benzylidene-4-phenyl-l,3-diselenole; CI = confidence interval; CYP450 = cytochrome P450; DEN = diethylnitrosamine; FEL = frank effect level;
GD = gestation day; GGT = y-glutamyl transferase; GPx = glutathione peroxidase; GR = glutathione reductase; GSH = glutathione; GST = glutathione-S-transferase;
i.p. = intraperitoneal; LC50 = median lethal concentration; LD50 = median lethal dose; LDH = lactate dehydrogenase; LOAEL = lowest-observed-adverse-effect level;
MDA = malondialdehyde; NaCl = sodium chloride; NADPH = reduced form of nicotinamide adenine dinucleotide phosphate; (NapSe)2 = binaphthyl diselenide;
ND = no data; NDr = not determined; NOAEL = no-observed-adverse-effect level; NPSH = nonprotein thiols; (PhSe)2 = diphenyl diselenide; RER = rough endoplasmic
reticulum; RNA = ribonucleic acid; S-D = Sprague-Dawley; SDH = sorbitol dehydrogenase; SER = smooth endoplasmic reticulum; TB ARS = thiobarbituric acid
reactive substances; UDP-glucuronosyltransferase = uridine 5'-diphospho-glucuronosyltransferase.
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Supporting Studies for Noncarcinogenic Effects in Animals
Most supporting animal studies have evaluated hepatic effects in rats after oral or i.p.
exposure. Collectively, these studies report elevated serum enzymes (e.g., AST, ALT), altered
liver biochemistry indicative of lipid peroxidation and oxidative stress, and hepatic lesions in rats
at acute oral doses >100 mg/kg (Wiiheim et al.. 2011; Ibrahim et al.. 2010; Wilhelm et al.. 2010)
and acute i.p. doses >50 mg/kg (Borges et al., 2006; Borges et al., 2005; El-Sokkary, 2002;
Hasegawa et at., 1995; Zitting et al., 1981). Most of these studies reported partial or complete
amelioration of effects with exposure to antioxidants before, during, or shortly after exposure. In
mice, hepatic effects (altered serum chemistry, liver lesions) were only observed after single i.p.
doses >6.7 mmol/kg (600 mg/kg); adverse effects were not observed at 4.5 mmol/kg [400 mg/kg;
Daval et al. (1989)1. Following inhalation exposure to 364 mg/m3 for 4 days (7 hours/day), no
changes in serum AST or ALT were observed in rats, but altered microsomal enzymes and
increased hepatic glutathione (GSH) and glutathione-S-transferase (GST) were observed (Haas-
Job cli us et al.. 1992).
Acute oral lethality studies with 2-nitropropane reported median lethal dose (LD50)
values of 500 mg/kg in rats (Kennedy and Graepei 1991), 392 mg/kg in mice (Hite and Skeggs,
1979), and 500-750 mg/kg in rabbits (Machle et al.. 1940). Acute inhalation studies with
2-nitropropane reported median lethal concentration (LC50) values of 400 ppm in male rats and
>580 ppm in female rats (Lewis et al.. 1979). Additional studies report the lowest concentration
at which mortality was first observed (approximate lethal concentration [ALC]) following
inhalation exposure to 2-nitropropane for 1-5 hours; values were 714-2,353 ppm for cats,
1,513-3,865 ppm for rats, 2,381-9,523 ppm for rabbits, and 4,622-9,607 ppm for guinea pigs
(Kennedy and Graepei. 1991; Treon and Dutra. 1952). Treon and Dutra (1952) also reported
mortality in 100% of cats exposed to 328 ppm for 3-17 exposures (7 hours/day, 5 days/week);
similarly exposed rats, guinea pigs, rabbits, and monkeys did not die after a total of
130 exposures. All species survived a total of 130 exposures to 83 ppm (Treon and Dutra. 1952).
Supporting Studies for Carcinogenic Effects in Rats
Initiation-promotion studies in the liver of rats indicated that 2-nitropropane can act as a
tumor promotor following oral exposure (Doi et al.. 2011) and a tumor initiator in the liver
following inhalation or i.p. exposure (Astorg et al.. 1994; Denk et al.. 1990).
Absorption, Distribution, Metabolism, and Elimination Studies
In the study by Nolan et al. (1982), rats were exposed by inhalation for 6 hours to
20-154 ppm of [14C]-2-nitropropane and the disposition of radioactivity in these animals was
followed for 48 hours. These data indicate that at least 40% of the inhaled compound was
absorbed. Dermal absorption was very low (<1%) in Rhesus monkeys following exposure for
12 hours in occluded conditions (Norman, 1990). Using human cadaver skin samples, the skin
permeability coefficient of 2-nitropropane was estimated to be 1.19 10 4 cm/hour (Tedesco,
2005). The 10- and 60-minute penetration rates were calculated to be 285.9 and
66.8 |ig/cm2-hour, respectively.
Distribution is rapid following inhalation exposure, with a blood distribution half-life of
~1 hour. Forty-eight hours after inhalation exposure to radiolabeled 2-nitropropane, the highest
concentrations were in organs involved with metabolism and elimination, including the lungs,
liver, and kidneys (Mueller et al, 1983; Nolan et al.. 1982). 2-Nitropropane is initially
distributed to the fat, but then is rapidly redistributed to other tissues (Mueller et al.. 1983).
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Elevated levels of radiolabel have also been identified in adrenal gland, bone marrow, and
spleen: the study authors attributed this to incorporation of radiolabeled carbon dioxide in heme
and steroid biosynthesis due to the expected metabolism of CI or C2 fragments or by
incorporation of radiolabeled carbon dioxide (14CC>2) during the production of oxaloacetate,
which introduces it into the Krebs cycle and consequently into heme biosynthesis, or during
generation of mevalonate, which is utilized in the biosynthesis of steroids (Mueller et al.. 1983).
The main metabolites of 2-nitropropane are carbon dioxide, nitrite/nitrate, acetone, and
isopropanol (Sohn and Fiala. 2000; Kohl and Gcscher. 1997; Mueller et al.. 1983; Ulrich et al..
1977). 2-Nitropropane first undergoes denitrification to form nitrite/nitrate plus acetone and
isopropanol, which can be oxidized into CO2. Nitrogen dioxide and potentially NO-species are
released in this process (Smith and Anderson. 2013; Kohl et al.. 1995; Bors et al.. 1993). Studies
have shown that oxidative denitrifi cation of 2-nitropropane into acetone is mediated via CYP450
enzymes, a process that can form reactive intermediates, including 2-hydroxy-2-nitropropane
(Smith and Anderson, 2013; Sohn and Fiala, 2000; Ulrich et al, 1977). Isomeric conversion of
2-nitropropane to its aci-tautomer, propane 2-nitronate, increases the rate of denitrifi cation (Kohl
and Gcscher. 1997). It has also been proposed that 2-nitropropane could undergo reductive
metabolism to reactive intermediates, such as 2-nitrosopropane, acetone oxime, isopropyl
hydroxylamine, or 2-aminopropane; however, these have only been identified in vitro (Smith and
Anderson, 2013; Andrae et al.. 1999; Haas-Jobelius et al.. 1991; Marker and Kulkarni, 1986). In
vitro studies have also shown that sulfotransferases can activate acetone oxime and propane
2-nitronate, leading to generation of NH2 (Kreis et al.. 2000; Andrae et al.. 1999; Sodum et al.,
1994). Following inhalation exposure, the metabolic rate was significantly higher in female rats
compared with male rats; metabolic rates in male and female rabbits were similar to those of
female rats ( AFC)SR. 1992).
Elimination in rats following inhalation or i.p. exposure to radiolabeled 2-nitropropane is
primarily via exhaled breath as parent compound (4.5%), acetone (10.4%), and CO2 (38.1%),
with the majority being exhaled within the initial 12 hours; minor amounts of radioactivity are
eliminated via urine (-6%) and feces (<1%) (Mueller et al.. 1983; Nolan et al.. 1982). Mueller et
al. (1983) identified the following urinary metabolites 6 hours after inhalation exposure:
unidentified polar metabolite (60%), isopropanol (18%), and acetone (10%). Twelve percent
remained in the urine as unmetabolized 2-nitropropane. At 24 hours, urinary metabolite
distribution is 80% unidentified polar metabolite, 8% isopropanol, and 12% acetone (Mueller et
al.. 1983). Nitrate and nitrite have also been identified in rat urine following i.p. injection (Sohn
and Fiala. 2000). Elimination kinetics in rats are dose-dependent, with elimination half-lives of
16 hours at low concentrations and 13.2 hours at high concentrations (Nolan et al.. 1982).
Similar elimination patterns were observed in chimpanzees following intravenous exposure
(Mueller et al.. 1983). Following dermal exposure in Rhesus monkeys, 93.4% of the (minimally)
absorbed dose was excreted in the urine (Norman, 1990).
Mode-of-Action/Mechanistic Studies
The mechanisms underlying 2-nitropropane liver toxicity and carcinogenicity are unclear;
however, researchers have proposed that these effects are secondary to oxidative stress attributed
to the generation of reactive intermediates like A'-nitro compounds and oxygen radicals during
the denitrifi cation of 2-nitropropane (Smith and Anderson, 2013; ACGIH. 2001). As discussed
in acute and short-term-duration oral studies in Tables 3 A and 4B, pre- or cotreatment of rats
with antioxidant compounds decreases or prevents hepatic toxicity associated with
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2-nitropropane exposure (Willielm et al.. 2011; Ibrahim et al.. 2010; Wilhelm et al.. 2010;
Wilhelm et al.. 2009; Sai et al.. 1998). Similar findings have been reported in acute i.p. studies
in Table 4B (Borges et al.. 2006; Borges et al.. 2005; El-Sokkarv. 2002; Takagi et al.. 1995).
Consistent with the proposed mechanism for non-neoplastic effects, there is strong evidence for
oxidative DNA damage in the liver (see Table 4A), which has also been shown to be mitigated
with pretreatment with antioxidant compounds (Sai et al.. 1998; Takagi et al .. 1995). These
findings support the hypothesis that hepatic toxicity and carcinogenicity is mediated, at least in
part, by oxidative stress. However, most of the proposed reactive metabolites are hypothetical
and have not been observed in vivo (see "Absorption, Distribution, Metabolism, and Elimination
Studies" section above).
Proposed carcinogenic progression following inhalation exposure to 2-nitropropane
includes severe cellular damage followed by regenerative hyper-proliferation, which can become
autonomous and malignant (Griffin et al. 1980; Griffin et al .. 1979; Coulston et al .. 1978).
Strong evidence for mutagenicity and DNA damage (see Table 4A) could contribute to
neoplastic transformation during this regenerative response. The apparent sensitivity of male
rats to this process may be due to observed sex and species differences in metabolic rates,
namely the fact that female rats and male and female rabbits show more rapid kinetics than male
rats (AFC)SR. 1992) (see "Absorption, Distribution, Metabolism, and Elimination
Studies" section above).
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DERIVATION OF PROVISIONAL VALUES
Tables 5 and 6 present summaries of noncancer and cancer references values,
respectively, for 2-nitropropane.
Table 5. Summary of Noncancer Reference Values for 2-Nitropropane (CASRN 79-46-9)
Toxicity Type
(units)
Species/
Sex
Critical Effect
p-Reference
Value
POD
Method
POD
(HED/HEC)
UFc
Principal
Study
Screening
subchronic p-RfD
(mg/kg-d)
Rat/M
Hepatocyte
hypertrophy
1 x 1(T3
BMDLio
0.34
300
Kawakami et
al. (2015)
Chronic p-RfD
(mg/kg-d)
NDr
Subchronic
p-RfC (mg/m3)
Rat/M
Liver effects (focal
hepatocyte
hypertrophy,
hepatocyte hyperplasia,
and hepatocyte
basophilic foci)
7 x 10-2
NOAEL
20
300
Lewis et al.
(1979); Ulrich
et al. (1977)
Chronic p-RfC
(mg/m3)
Inhalation RfC value of 0.02 me/m3 is available on IRIS (U.S. EPA. 20023).
BMDL = benchmark dose lower confidence; HEC = human equivalent concentration; HED = human equivalent
dose; IRIS = Integrated Risk Information System; M = male(s); NDr = not determined;
NOAEL = no-observed-adverse-effect level; POD = point of departure; p-RfC = provisional reference
concentration; p-RfD = provisional reference dose; RfC = reference concentration; UFc = composite uncertainty
factor.
Table 6. Summary of Cancer Reference Values for 2-Nitropropane (CASRN 79-46-9)
Toxicity Type (units)
Species/Sex
Tumor Type
Cancer Value
Principal Study
p-OSF (mg/kg-d) 1
NDr
Screening p-IUR
(mg/m3)-1 (adjusted)
Rat/M
Hepatocellular carcinoma
5.8 x KT1
Lewis et al. (1979);
Ulrich et al. (1977)
M = male(s); NDr = not determined; p-IUR = provisional inhalation unit risk; p-OSF = provisional oral slope
factor.
DERIVATION OF ORAL REFERENCE DOSES
Animal data for 2-nitropropane relevant to provisional reference dose (p-RfD) derivation
include a 16-week cancer study in rats with limited reporting on non-neoplastic endpoints (Fiala
et al.. 1987b). two 14- to 28-day studies in rats that only evaluated clinical signs, body weight,
and liver endpoints (Kawakami et al.. 2015; Nakavama et al.. 20061 two 2-week studies in rats
that only evaluated renal and/or liver endpoints (Willielm et al.. 2009; Sai et al.. 1998). three
single-exposure-1 evel studies that only evaluated renal and/or liver endpoints (Willielm et al..
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2011; Ibrahim et al.. 2010; Wilhelm et al.. 2010), and acute lethality studies in rats, mice, and
rabbits (Kennedy and Graepei. 1991; Hite and Skeggs. 1979; Machlc et al.. 1940). Although
these studies are deemed too limited in scope and/or duration to support derivation of p-RfDs,
the 28-day study by Kawakami et al. (2015) provided sufficient data to develop a screening
subchronic p-RfD value (see Appendix A).
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS
Derivation of Subchronic Provisional Reference Concentration
The database of potentially relevant studies for deriving a subchronic provisional
reference concentration (p-RfC) for 2-nitropropane includes a brief report of a 2-month study in
rats (Coulston et al.. 1978) and interim sacrifice data from several chronic-duration inhalation
studies in rats (Griffin et al.. 1979; Lewis et al.. 1979; Coulston et al.. 1978; Ulrich et al.. 1977)
and one study in rabbits (Lewis et al.. 1979; Ulrich et al.. 1977). Collectively, these studies
indicate that the liver in the male rat is the most sensitive target of toxicity following subchronic
inhalation exposure (7 hours/day, 5 days/week for 1-3 months). Hepatic findings include
elevated liver weight in male rats at >312 mg/m3 (HEC = 65.0 mg/m3) and female rats at
>608 mg/m3 (HEC = 127 mg/m3), and elevated serum enzyme levels and non-neoplastic lesions
in male rats at >608 mg/m3 (HEC = 127 mg/m3). No adverse effects were observed in rabbits
following exposure for up to 6 months to concentrations up to 754 mg/m3 (HEC =157 mg/m3).
The liver is also the primary toxicity target following acute, short-term, and chronic
inhalation exposure in rats (Griffin et al.. 198 1; Griffin et al.. 1980; Lewis et al.. 1979; Coulston
et al.. 1978; Ulrich et al.. 1977) and cats (Treon and Dutra, 1952), and hepatic effects are the
basis of the chronic inhalation reference concentration (RfC) in U.S. EPA's IRIS database (U.S.
EPA, 2002a). Acute and short-term-duration oral and i.p. injection studies also report hepatic
effects in rats (Wilhelm et al.. 2011; Ibrahim et al.. 2010; Wilhelm et al.. 2010; Wilhelm et al..
2009; Borges et al.. 2006; Nakavama et al.. 2006; Borges et al.. 2005; El-Sokkarv. 2002; Sai et
al- 1998; Hasegawa et al.. 1995; Takagi et al.. 1995; Zitting et al.. 1981) and (at higher doses)
mice (Da vat et al.. 1989). Case reports of acute hepatic failure in workers exposed to high
concentrations of 2-nitropropane support the liver as the primary target of 2-nitropropane toxicity
in humans (Harrison et al.. 1987; Harrison et al.. 1985; NIOSH. 1985; Rondia, 1979; Hine et al..
1978). Altogether, these data indicate that the liver is a primary target organ of toxicity
following exposure to 2-nitropropane.
Most of the studies with subchronic data provided no dose-response information because
they included only one exposed group plus a control group. These studies identified only
LOAELs (HECs) of 65.0 mg/m3 or more, and no NOAELs were identified. The exception is the
published study by Lewis et al. (1979) [and accompanying unpublished report by Ulrich et al.
(1977)1, which included two dose groups plus a control group. A NOAEL and LOAEL (HEC)
of 20 and 157 mg/m3, respectively, were identified for subchronic effects in this study based on
increases in absolute and relative liver weight and increased hepatic lesions (focal hepatocyte
hypertrophy, focal hepatocyte hyperplasia, and basophilic foci) in male rats at 3 months. To
provide a common basis for comparing potential points of departure (PODs) and critical effects
for deriving a subchronic p-RfC for 2-nitropropane, data sets representing the most sensitive
liver endpoints from Lewis et al. (1979) and Ulrich et al. (1977) were considered for benchmark
dose (BMD) analysis. The data for increased absolute and relative liver weight shown in Table 7
were modeled using all available continuous models in the Benchmark Dose Software (BMDS,
Version 2.6), as appropriate. HECs were used as the dose metric, and a benchmark response
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(BMR) of 10% relative deviation (RD) from the control mean was run because a 10% change in
liver weight is considered biologically significant. On the other hand, the benchmark
concentration lower confidence limits (BMCLs) for hepatocyte hypertrophy, hepatocyte
hyperplasia, and hepatocyte basophilic foci in male S-D rats exposed to 2-nitropropane for
3 months (Lewis et al.. 1979; Ulrich et al.. 1977) would be considered unreliable based on the
U.S. EPA's Benchmark Dose Technical Guidance, which states, "a data set with only the highest
dose showing a response would bracket the BMD at the low end but may provide limited
information about the shape of the dose-response relationship. In such cases, dose spacing and
the proximity of the BMR to the observed response level will influence the uncertainty in the
BMD estimate" (U.S. EPA, 2012b). Therefore, the data for hepatic lesions (e.g., hepatocyte
hyperplasia) in Table 7 were not BMD modeled.
Table 7. Data for Absolute and Relative Liver Weight and Incidence of Liver Lesions in
Male S-D Rats Exposed to 2-Nitropropane via Inhalation for 3 Months3
Endpoint
Concentration (HEC in mg/m3)
0
20
157
Absolute liver weight (g)b
11.8± 1.3 (10)
13.0 ± 1.5 (10)
16.7 ±2.6 (9)
Relative liver weight (% BW)b
2.6 ±0.11 (8)
2.7 ±0.16 (10)
4.1 ±0.57 (9)
Focal hepatocyte hypertrophy0
0/10
0/10
9/9
Focal hepatocyte hyperplasia0
0/10
0/10
4/9
Hepatocyte basophilic foci0
0/10
0/10
4/9
aLewis et al. (1979); Ulrich et al. (1977).
bData reported as mean ± SD («); SD values were calculated from reported SEM values (SD = SEM x "hi).
°Values denote number of animals showing changes/total number of animals examined.
BW = body weight; HEC = human equivalent concentration; S-D = Sprague-Dawley; SD = standard deviation;
SEM = standard error of the mean.
Table 8 summarizes the benchmark dose (BMD) modeling results and provides candidate
points of departure (PODs) for the modeled endpoints. Details of model fit for each data set are
presented in Appendix C.
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Table 8. Potential PODs in Male S-D Rats Exposed to 2-Nitropropane via Inhalation for
3 Months3
Endpoint
NOAEL (HEC)
(mg/m3)
LOAEL (HEC)
(mg/m3)
BMCL (HEC)b
(mg/m3)
POD (HEC)
(mg/m3)
Absolute liver weight
NDr
20
29
29 (BMCLio)
Relative liver weight
20
157
28
28 (BMCLio)
Focal hepatocyte hypertrophy
20
157
NDr
20 (NOAEL)
Focal hepatocyte hyperplasia
20
157
NDr
20 (NOAEL)
Hepatocyte basophilic foci
20
157
NDr
20 (NOAEL)
aLewis et at (1979): Ulrich et at (1977).
bModeling results are described in more detail in Appendix C.
BMCL = benchmark concentration lower confidence limit; HEC = human equivalent concentration;
LOAEL = lowest-observed-adverse-effect level; NDr = not determined; NOAEL = no-observed-adverse-effect
level; POD = point of departure; S-D = Sprague-Dawley.
A NOAEL (HEC) of 20 mg/m3 is identified as the POD for the hepatic lesions (focal
hepatocyte hypertrophy, focal hepatocyte hyperplasia, and basophilic foci) from Lewis et al.
(1979) and Ulrich et al. (1977), and is the most health protective subchronic POD identified.
Thus, the NOAEL (HEC) of 20 mg/m3 is chosen as the POD for deriving the subchronic p-RfC.
The subchronic p-RfC is derived by applying a composite uncertainty factor (UFc) of 300
(reflecting an interspecies uncertainty factor [UFa] of 3, an intraspecies uncertainty factor [UFh]
of 10, and a database uncertainty factor [UFd] of 10) to the selected POD of 20 mg/m3.
Subchronic p-RfC = POD (NOAEL) - UFC
= 20 mg/m3 -^300
= 7 x lO-2 mg/m3
Table 9 summarizes the uncertainty factors for the subchronic p-RfC for 2-nitropropane.
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Table 9. Uncertainty Factors for the Subchronic p-RfC for 2-Nitropropane
UF
Value
Justification
UFa
3
A UFa of 3 (10°5) is applied to account for uncertainty associated with extrapolating from animals to
humans using toxicokinetic cross-species dosimetric adjustment for extrarespiratory effects from a
Category 3 gas, as specified in U.S. EPA (1994) guidelines for deriving RfCs.
UFd
10
A UFd of 10 is applied to account for deficiencies and uncertainties in the database. The inhalation
database for 2-nitropropane includes several subchronic/chronic-duration studies in rats (Griffin et al.
1981; Griffin et al.. 1980; Griffin et al.. 1979; Lewis et al.. 1979; Coulston et al.. 1978; Ulrich et al..
1977) and one in rabbits (Lewis et al.. 1979; Ulrich et al.. 1977) that investigated a wide variety of
endpoints and included interim short-term and/or subchronic sacrifices. With the exception of Lewis
et al. (1979). however, the studies were unpublished and not peer reviewed, and each included onlv a
single exposure level. Inhalation data in other species are limited to a poorlv reported studv bv Treoti
and Dutra (1952) with limited endpoint evaluation. There are no reproductive or developmental
toxicity studies available by inhalation or oral exposure.
UFh
10
A UFh of 10 is applied to account for human variability in susceptibility, in the absence of
information to assess toxicokinetic and toxicodynamic variability of 2-nitropropane in humans.
UFl
1
A UFl of 1 is applied because the POD is a NOAEL (HEC).
UFs
1
A UFs of 1 is applied because the POD was derived from subchronic data.
UFC
300
Composite UF = UFA x UFD x UFH x UFL x UFS.
HEC = human equivalent concentration; LOAEL = lowest-observed-adverse-effect level;
NOAEL = no-observed-adverse-effect level; POD = point of departure; p-RfC = provisional reference
concentration; 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.
Confidence in the subchronic p-RfC for 2-nitropropane is low as described in Table 10.
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Table 10. Confidence Descriptors for the Subchronic p-RfC for 2-Nitropropane
Confidence Categories
Designation
Discussion
Confidence in study
L
Confidence in the principal studv (Lewis et al.. 1979; Ulrich et
al.. 1911) is low. The studv examined a wide varietv of endpoints
and performed interim sacrifices at several time points in rats and
rabbits, but only two exposure levels were tested, only males
were included for both rats and rabbits, and group sizes were
small given that only one sex was tested (10 animals per time
point for rats and 5 for rabbits). The published paper included
only limited description of study methods and results; much of
the data was available onlv from the unpublished version (TJlrich
et al.. 1977). which was not peer reviewed.
Confidence in database
L
Confidence in the database is low. The inhalation database for
2-nitropropane includes several subchronic/chronic-duration
studies in rats (Griffin et al.. 1981; Griffin et al.. 1980; Griffin et
al.. 1979; Lewis et al.. 1979; Coulston et al.. 1978; Ulrich et al..
1977) and one in rabbits (Lewis et al.. 1979; Ulrich et al.. 1977)
that investigated a wide variety of endpoints and included interim
short-term and/or subchronic sacrifices. With the exception of
Lewis et al. (1979). however, the studies were unpublished and
not peer-reviewed and each included only a single exposure level.
Inhalation data in other species are limited to a poorly reported
studv bv Treon and Dutra (1952) with limited endpoint evaluation
(cats, rats, rabbits, guinea pigs). No reproductive or
developmental toxicity studies are available for inhalation or oral
exposure.
Confidence in subchronic p-RfCa
L
Overall confidence in the subchronic p-RfC is low.
aThe overall confidence cannot be greater than the lowest entry in the table (low).
L = low; p-RfC = provisional reference concentration.
Derivation of Chronic Provisional Reference Concentration
A chronic p-RfC value was not derived because an RfC value is available on U.S. EPA's
IRIS database (U.S. EPA 2002a).
CANCER WEIGHT-OF-EVTDENCE DESCRIPTOR
Following Guidelines for Carcinogen Risk Assessment (US. EPA. 2005a),
2-nitropropane is "Likely to be Carcinogenic to Humans" by oral or inhalation exposure
(see Table 11). Available epidemiological studies are not adequate to assess the carcinogenic
potential of 2-nitropropane in humans. In animals, 2-nitropropane produced 100% incidence
(22/22) of hepatocellular carcinoma in male rats treated by gavage at the only dose tested
(90 mg/kg-day) after oral treatment for only 16 weeks (Fiala et al.. 1987b). Similarly, in an
inhalation study that included multiple concentrations, 2-nitropropane produced hepatocellular
carcinoma in all 10 male rats exposed for 6 months at the high concentration of 754 mg/m3,
although no tumors were reported in rats exposed to 98 mg/m3 (Lewis et al.. 1979; Ulrich et al.,
1977). Other unpublished inhalation studies reported the development of liver tumors in male
rats exposed to 2-nitropropane for >6 months at 312-608 mg/m3 (Griffin et al .. 1979; Coulston et
al.. 1978). These studies also included female rats, which did not develop tumors. Another
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study conducted at a concentration of 77.8 mg/m3 for 22 months found no increase in tumors in
male or female rats (Griffin et al.. 1981; Griffin et al.. 1980). A study in rabbits found no
increase in tumors after 6 months at 754 mg/m3, but small sample sizes limited reliability and
interpretability of the study (Lewis et al.. 1979; Ulrich et al.. 1977). The very high incidence of
malignant tumors following oral and inhalation exposure to 2-nitropropane in male rats evident
in these studies despite relatively short exposure durations and small group sizes support the
conclusion of "Likely to be Carcinogenic to Humans, " although tumors have not been found in
female rats and adequate studies are not available in other species. This conclusion is also
supported by additional evidence demonstrating that 2-nitropropane is genotoxic by exhibiting
mutagenicity and producing chromosomal and DNA damage in the liver, which is the site of
tumor development (see Table 4A for the list of relevant studies).
Table 11. Cancer WOE Descriptor for 2-Nitropropane
Possible WOE Descriptor
Designation
Route of Entry (oral,
inhalation, or both)
Comments
"Carcinogenic to Humans"
NS
NA
No adequate human data are available.
"Likely to Be Carcinogenic
to Humans"
Selected
Both
2-Nitropropane has been shown to produce
very high incidence of malignant liver
tumors by oral (90 mg/kg-d) or inhalation
(>312 mg/m3) exposure in male rats despite
relatively short exposure durations and
small group sizes in the available studies.
Studies performed at concentrations lower
than 100 mg/m3 did not find tumors in male
rats and no study found tumors in female
rats. No adequate studies in other species
were located. The available evidence
demonstrates that 2-nitropropane is a
mutagen, and produces chromosomal and
DNA damage in the liver, which is the site
of tumor development.
"Suggestive Evidence of
Carcinogenic Potential"
NS
NA
Evidence of the carcinogenic potential of
2-nitropropane supports a stronger descriptor.
"Inadequate Information to
Assess Carcinogenic
Potential"
NS
NA
Adequate information is available to assess the
carcinogenic potential of 2-nitropropane.
"Not Likely to Be
Carcinogenic to Humans "
NS
NA
The available data do not support this
descriptor.
DNA = deoxyribonucleic acid; NA = not applicable; NS = not selected; WOE = weight of evidence.
MODE-OF-ACTION DISCUSSION
The Guidelines for Carcinogenic Risk Assessment (U.S. EPA. 2005a) define mode of
action (MO A) ".. .as a sequence of key events and processes, starting with interaction of an agent
with a cell, proceeding through operational and anatomical changes, and resulting in cancer
formation." Examples of possible modes of carcinogenic action for any given chemical include
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"mutagenicity, mitogenesis, programmed cell death, cytotoxicity with reparative cell
proliferation, and immune suppression."
The available evidence demonstrates that 2-nitropropane is a mutagen, and produces
chromosomal and DNA damage in the liver, which is the site of tumor development (see the
"Genotoxicity Studies" section for more details). Additionally, it has also been proposed that
severe hepatocellular damage by reactive metabolites followed by regenerative
hyper-proliferation underlies hepatic tumor development induced by 2-nitropropane (see the
"Mode-of-Action/Mechanistic Studies" section above for more details). Therefore, a mixed
MOA for 2-nitropropane carcinogenicity is expected; however, available data are inadequate to
evaluate which proposed MOA is more plausible. The approach using the Bradford-Hill criteria
follows:
Key Events—Available data indicate that 2-nitropropane is a mutagen, both with and
without metabolic activation, suggesting a proposed MOA where mutation of critical genes, such
as oncogenes, followed by proliferation of initiated cells may occur.
Strength, Consistency, Specificity of Association—The apparent strength and
consistency of the available genotoxicity data in bacterial and mammalian cells in vitro with and
without metabolic activation demonstrates that 2-nitropropane is mutagenetic (Nikolic et al..
2012; Stajkovic et al.. 2007; Cabelof et al., 2002; Deng et al., 1998; Weisburger et al., 1996;
Kohl et al., 1994; Adachi et al., 1993; Sakai and Uchida, 1992; Conaway et al., 1991a; Haas-
Jobelius et al.. 1991; Roscher et al .. 1990; Goggeimann et al .. 1988; Fiala et al.. 1987a; Lofroth
et al .. 1986; Haworth et al.. 1983; Speck et al.. 1982; Hite and Skeggs. 1979; Litton Bionetics.
1977a, b), and induced dominant lethal mutations in female rats (McGregor, 1981) and lacl
mutations in male mouse liver tissue (Cabelof et al.. 2002) following in vivo exposure.
Temporal and Dose-Response Concordance—No studies have been located that
specifically evaluate both mutagenic events and tumor development. Most available cancer data
for 2-nitropropane are reported in animal inhalation studies, which report hepatic tumors in rats
following chronic exposure to 364-754 mg/m3 (Griffin et al.. 1979; Lewis et al.. 1979; Coulston
et al.. 1978; Ulrich et al.. 1977). In the only inhalation study evaluating mutagenicity, dominant
lethal mutations were observed after exposure to 729 mg/m3. Hepatic tumors have been
observed also following oral exposure to 90 mg/kg-day for 16 weeks (only dose tested) (Fiala et
al.. 1987b). No oral studies evaluated mutagenicity. Based on these findings, mutations may
occur at relevant inhalation exposure levels; however, the lack of mutation data in the liver
following inhalation exposure precludes adequate evaluation of temporal or dose-response
concordance.
Biological Plausibility and Coherence—Supporting evidence for the association
between mutagenicity and tumor formation comes from the observation that 2-nitropropane
exposure is capable of causing mutations in the liver, which is the site of tumor development
(Fiala et al.. 1987b; Griffin et al.. 1979; Lewis et al .. 1979; Coulston et al. 1978; Ulrich et al ..
1977). Additionally, it is hypothesized that these carcinogenic effects are secondary to oxidative
stress attributed to the generation of reactive intermediates like A'-nitro and oxygen radicals
during the denitrification of 2-nitropropane (Smith and Anderson, 2013; ACGIH, 2001).
Evidence from in vitro studies indicates that 2-nitropropane is mutagenic. Furthermore, there is
coherence across the evidence from in vivo genotoxicity studies indicating that 2-nitropropane is
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mutagenic across species and sexes (e.g., in both sexes of rats and in male mice) (Cabetof et al.,
2006; Cabelof et al., 2002; Guo et al.. 1990; Hussain et al.. 1990).
Because mutagenicity is involved in a plausible mixed MO A, a linear approach is
appropriate to extrapolate from the POD in deriving a screening provisional inhalation unit risk
(p-IUR) (U.S. EPA, 2005a).
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES
Derivation of Provisional Oral Slope Factor
Fiala et al. (1987b) observed a highly significant increase in the incidence of
hepatocellular carcinoma in male rats treated with 90 mg/kg-day of 2-nitropropane by gavage
3 times/week for 16 weeks. Study limitations, most notably treatment of a single dose group,
precluded developing a provisional oral slope factor (p-OSF) because the data were not
amenable to modeling using the Multistage cancer model.
Derivation of Provisional Inhalation Unit Risk
One study in the inhalation database provided dose-response information for tumors
induced by 2-nitropropane (Lewis et al.. 1979; Ulrich et al.. 1977). This study found liver
carcinomas in 10/10 high-dose male rats but not in the control or low-dose rats following
6 months of inhalation exposure. Per the U.S. EP A's Benchmark Dose Technical Guidance, "a
data set with only the highest dose showing a response would bracket the BMD at the low end
but may provide limited information about the shape of the dose-response relationship. In such
cases, dose spacing and the proximity of the BMR to the observed response level will influence
the uncertainty in the BMD estimate" (U.S. EPA. 2012b). Thus, given the uncertainty
surrounding BMD modeling of the liver tumor data from the lone inhalation carcinogenicity
study, derivation of a p-IUR is precluded, but a screening p-IUR based on the BMCLio for liver
tumors is presented in Appendix A.
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APPENDIX A. SCREENING PROVISIONAL VALUES
For reasons noted in the main Provisional Peer-Reviewed Toxicity Value (PPRTV)
document, it is inappropriate to derive provisional reference doses (p-RfDs) for 2-nitropropane.
However, information is available for this chemical, which although insufficient to support
derivation of a provisional toxicity value under current guidelines, may be of limited use to risk
assessors. In such cases, the Center for Public Health and Environmental Assessment (CPHEA)
summarizes available information in an appendix and develops a "screening value." Appendices
receive the same level of internal and external scientific peer review as the main documents to
ensure their appropriateness within the limitations detailed in the document. Users of screening
toxicity values in an appendix to a PPRTV assessment should understand that there is
considerably more uncertainty associated with the derivation of an appendix screening toxicity
value than for a value presented in the body of the assessment. Questions or concerns about the
appropriate use of screening values should be directed to the CPHEA.
DERIVATION OF SCREENING PRO VISIONAL REFERENCE DOSES
As discussed in the main body of the report, available oral studies are too limited in scope
and/or duration to support derivation of p-RfDs. A screening-level subchronic value can,
however, be derived from the 28-day oral study in rats (Kawakami et al.. 2015). This study
provided dose-response information for several liver endpoints. A no-observed-adverse-effect
level (NOAEL) of 5 mg/kg-day and a lowest-observed-adverse-effect level (LOAEL) of
20 mg/kg-day were identified based on increased relative liver weight and increased incidence of
hepatocyte hypertrophy. While this is not a comprehensive study, the inhalation database and
available acute and short-term-duration oral and intraperitoneal (i.p.) injection studies all identify
the liver as the most sensitive target of 2-nitropropane toxicity (see Tables 3 A and 4B). To
account for the uncertainty associated with basing a reference dose on a 28-day study of limited
endpoints, the assessment is considered a screening-level assessment.
Data for the most sensitive endpoints in the 28-day oral study (increased relative liver
weight and increased incidence of hepatocyte hypertrophy) were modeled using all available
continuous or dichotomous models, as appropriate, in the Benchmark Dose Software (BMDS,
Version 2.6). The modeled data are shown in Table A-l. Human equivalent doses (HEDs) in
mg/kg-day were used as the dose metric. The administered doses of 0, 5, 20, and 40 mg/kg-day
were converted into HEDs of 0, 1, 5.0, and 9.9 mg/kg-day (see Footnote B in Table A-l). For
increased relative liver weight, a benchmark response (BMR) of 10% relative deviation (RD)
from the control mean was run because a 10% change in liver weight is considered biologically
significant. For hepatocellular hypertrophy, a standard BMR for dichotomous data of 10% extra
risk was run.
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Table A-l. Data for Relative Liver Weight and Hepatocyte Hypertrophy in Male Crl:CD
(SD) Rats Administered 2-Nitropropane via Gavage for 28 Days3
Parameter
ADD (HED)b mg/kg-d
0(0)
5(1)
20 (5.0)
40 (9.9)
Relative liver weight
(10% BW)°
2.91 ±0.09 (5)
2.98 ±0.23 (5)
3.32 ±0.2 (5)
3.60 ±0.19 (5)
Hepatocyte hypertrophyd
0/5
0/5
2/5
5/5
aKawakami et at (2015).
' HEDs were calculated using DAFs. as recommended by U.S. EPA (2011b). The DAF is calculated as follows:
DAF = (BWa1/4 ^ BWh1/4), where DAF = dosimetric adjustment factor, BWa = animal body weight, and
B Wh = human body weight. In the absence of sufficient data to calculate TWA body weights from the rat study,
reference body weights recommended by U.S. EPA (1988b) were used to calculate the D AFs: 70 kg for humans
and 0.267 kg for male S-D rats in a subchronic-duration study. HED = ADD x DAF.
Data reported as mean ± SD («).
dValues denote number of animals showing changes/total number of animals examined
ADD = adjusted daily dose; BW = body weight; DAF = dosimetric adjustment factor; HED = human equivalent
dose; SD = standard deviation; S-D = Sprague-Dawley; TWA = time-weighted average.
Table A-2 summarizes the benchmark dose (BMD) modeling results and provides
candidate points of departure (PODs) for the modeled endpoints. Details of model fit for each
data set are presented in Appendix C.
Table A-2. BMD and BMDL Values from Best Fitting Models for Relative Liver Weight
and Hepatocyte Hypertrophy in Male Crl:CD (SD) Rats Administered 2-Nitropropane via
Gavage for 28 Days3
Endpoint
Best-Fitting Model
BMR
BMD (HED)
(mg/kg-d)
BMDL (HED)
(mg/kg-d)
Increased relative liver
weight
Linear
10% RD from control
BMDio = 4.1
BMDLio = 3.3
Hepatocyte hypertrophy
Multistage 1-degree
10% extra risk
BMDio = 0.64
BMDLio = 0.34
aKawakami et at (2015).
BMD = benchmark dose; BMDL = benchmark dose lower confidence limit (subscripts denote benchmark
response: i.e., 10 = dose associated with 10% extra risk); BMR = benchmark response; HED = human equivalent
dose; RD = relative deviation; SD = standard deviation.
Derivation of Screening Subchronic Provisional Reference Dose
The 10% benchmark dose lower confidence limit (BMDLio) (HED) of 0.34 mg/kg-day
for increased incidence of hepatocellular hypertrophy in male rats in the 28-day oral study
(Kawakami et al.. 2015) is the most health protective POD identified and is selected as the POD
for deriving the screening subchronic p-RfD.
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The screening subchronic p-RfD is derived by applying a composite uncertainty factor
(UFc) of 300 (reflecting an interspecies uncertainty factor [UFa] of 3, an intraspecies uncertainty
factor [UFh] of 10, and a database uncertainty factor [UFd] of 10) to the selected POD of
0.34 mg/kg-day.
Screening Subchronic p-RfD = POD (HED) UFc
= 0.34 mg/kg-day ^ 300
= 1 x 10"3 mg/kg-day
Table A-3 summarizes the uncertainty factors for the screening subchronic p-RfD for
2-nitropropane.
Table A-3. Uncertainty Factors for the Screening Subchronic p-RfD for 2-Nitropropane
UF
Value
Justification
UFa
3
A UFa of 3 (10°5) is applied to account for uncertainty in characterizing the toxicokinetic or
toxicodynamic differences between rats and humans following 2-nitropropane exposure. The
toxicokinetic uncertainty has been accounted for by calculating an HED through application of a D AF
as outlined in the U.S. EPA's Recommended Use of Body Weight4 as the Default Method in
Derivation of the Oral Reference Dose (U.S. EPA, 1988b).
UFd
10
A UFd of 10 is applied to account for deficiencies and uncertainties in the database. The oral
database for 2-nitropropane is limited to short-term-duration and acute studies of limited scope and a
cancer bioassay that contains limited information on noncancer endpoints. Although comprehensive
oral studies were not identified, inhalation and injection studies provide support for the liver as the
critical target for this chemical. No reproductive or developmental toxicity studies are available for
oral or inhalation exposure.
UFh
10
A UFh of 10 is applied to account for human variability in susceptibility, in the absence of
information to assess toxicokinetic and toxicodynamic variability of 2-nitropropane in humans.
UFl
1
A UFl of 1 is applied because the POD is a BMDL.
UFS
1
A UFS of 1 is applied because the POD was derived from a 28-d study.
UFc
300
Composite UF = UFA x UFD x UFH x UFL x UFS.
BMDL = benchmark dose with lower confidence limit; HED = human equivalent dose;
LOAEL = lowest-observed-adverse-effect level; NOAEL = no-observed-adverse-effect level; POD = point of
departure; p-RfD = provisional 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.
Derivation of Screening Chronic Provisional Reference Dose
There are no chronic-duration oral studies on 2-nitropropane. The 28-day study used to
derive the screening subchronic p-RfD (Kawakami et al.. 2015) is too limited in duration to
support derivation of a screening chronic p-RfD. Use of a less-than-subchronic-duration study is
inappropriate for deriving chronic toxicity values unless chronic toxicity data are available to
indicate that the critical effect observed in the short-term-duration study will not increase in
severity or become more sensitive based on dose-response analysis following longer treatment
duration. While no longer duration oral data are available, limited inhalation data suggest that
sensitivity to hepatic toxicity may increase with exposure durations >6 months. In 6-month
studies with interim sacrifices, data show that comparable hepatic effects occur at similar doses
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across time points up to 6 months; for example, the hepatic NOAEL (HEC) and LOAEL (HEC)
are 20 and 157 mg/m3, respectively, after 10 days, 1 month, 3 months, or 6 months of exposure
in the study by Lewis et al. (1979) and Ulrich et al. (1977). In a longer duration study, Griffin et
al. (1981) and Griffin et al. (1980) reported a lower LOAEL (HEC) of 16.2 mg/m3 for hepatic
effects following exposure for up to 22 months, suggesting increased sensitivity to liver effects
following 22-month versus 10-day to 6-month exposures. For this reason, no screening chronic
p-RfD was derived.
Derivation of Screening Provisional Inhalation Unit Risk
As discussed in the main body of the assessment, only one study in the inhalation
database provided dose-response information for tumors induced by 2-nitropropane (Lewis et al.
1979; Ulrich et al.. 1977). and based on the dose-spacing of the liver tumor data and tumors in all
high-dose treated animals, there is uncertainty in the BMD estimate. Thus, to account for this
increased uncertainty, a screening p-IUR is derived. The data for hepatocellular carcinoma are
shown in Table A-4.
Table A-4. Data for Hepatocellular Carcinoma in Male S-D Rats Exposed to
2-Nitropropane via Inhalation for 6 Months3


Concentration (HEC in mg/m3)
Endpoint
0
20
157
Hepatocellular carcinomab
0/10
0/10
10/10
aLewis et al. (1979); Ulrich et al. (1977).
bValues denote number of animals showing changes/total number of animals examined.
HEC = human equivalent concentration; S-D = Sprague-Dawley.
BMD modeling was performed for this data set using the Multistage cancer model in the
U.S. EPA BMDS (Version 2.6). The BMR used was 10% extra risk. The HEC in mg/m3 was
used as the dose metric. Modeling results are summarized in Table A-5 (see additional BMD
details in Appendix C).
Table A-5. BMD Model Results Based on the Incidence of Hepatocellular Carcinoma in
Male S-D Rats Exposed to 2-Nitropropane via Inhalation for 6 Months3
Tumor Endpoint
Selected Model
BMCio
(HEC, mg/m3)
BMCLio
(HEC, mg/m3)
Hepatocellular carcinoma
Multistage (2-degree)
25
11
aLewis et al. (1979); Ulrich et al. (1977).
BMC = benchmark concentration; BMCL = 95% lower confidence limit on the benchmark concentration
(subscripts denote benchmark response: i.e., 10 = concentration associated with 10% extra risk);
BMD = benchmark dose; HEC = human equivalent concentration; p-IUR = provisional inhalation unit risk;
S-D = Sprague-Dawley.
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The Multistage cancer model provided adequate fit to the data set for hepatocellular
carcinoma from Lewis et al. (1979) and UI rich et al. (1977). BMCio and BMCLio values for the
best fitting (2-degree) model were 25 and 11 mg/m3 (HEC), respectively. The BMCLio value of
11 mg/m3 (HEC) based on hepatocellular carcinoma risk was used as the POD for deriving the
screening p-IUR.
The mode of action (MOA) by which 2-nitropropane induces liver tumors is expected to
be mixed and includes a mutagenic component. A linear approach is used to calculate the
screening p-IUR from the BMCLio (HEC) of 11 mg/m3 for liver tumors in male rats exposed to
2-nitropropane for 6 months.
Screening p-IUR (unadjusted) = BMR ^ BMCLio (HEC)
= 0.1 ^ 11 mg/m3
= 9.1 x 10"3 (mg/m3)"1
An adjustment was applied to account for the less-than-lifetime observation period (U.S.
EPA. 1980). The Lewis et al. (1979) and Ulrich et al. (1977) bioassay was designed to expose
rats to 2-nitropropane for only 6 months. Thus, due to the short duration of the study, it cannot be
known how an increased duration (i.e., the full 2-year lifetime exposure) might have influenced
the tumor incidence in the low-dose treated rats. Therefore, an adjustment factor of (L Le)3
was applied to the unadjusted screening p-IUR, where L = the lifetime of the animal and Le = the
duration of experimental dosing (U.S. EPA, 1980). Using this adjustment, an adjusted screening
p-IUR is derived as follows:
Screening p-IUR (adjusted) = p-IUR (unadjusted) x (L Le)3
= 9.1 x io-3 (mg/m3)-1 x (24 months 6 months)3
= 5.8 x 10"1 (mg/m3)"1
It is important to note that the Lewis et al. (1979) and Ulrich et al. (1977) bioassay raises
concern for lower exposures and longer durations, but the degree of adjustment is too uncertain
for lifetime exposure in this case and is therefore questionable. However, this estimate is more
health protective than the estimate without the (L Le)3 adjustment, which is likely to be
underestimated. Furthermore, because 2-nitropropane is "Likely to be Carcinogenic to Humans"
by inhalation exposure (see Table 11), derivation of a screening p-IUR for this chemical is
warranted despite the aforementioned uncertainty due to the application of the less-than-lifetime
adjustment factor.
A weight-of-evidence (WOE) evaluation has concluded that 2-nitropropane is
characterized by a mixed MO A, which includes a mutagenic component. According to the
Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens
(U.S. EPA. 2005b), those exposed to carcinogens with a mutagenic MO A are assumed to have
increased early-life susceptibility. Data on 2-nitropropane are not sufficient to develop separate
risk estimates for childhood exposure. The screening p-IUR of 5.8 x 10 1 (mg/m3)-1 calculated
from data from adult exposure does not reflect presumed early-life susceptibility for this
chemical, and age-dependent adjustment factors (ADAFs) should be applied to this parameter
when assessing cancer risks. The current ADAFs and their age groupings are 10 for <2 years,
3 for 2 to < 16 years, and 1 for 16 years and above (U.S. HP A, 2005b). The adjusted screening
p-IURs associated with these ADAFs are 5.8 x 10° (mg/m3)-1 for <2 years, 1.7 x 10° (mg/m3)-1
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for 2 to <16 years, and 5.8 x 1CT1 (mg/m3)-1 for 16 years and above. These screening p-IURs are
to be combined with age-specific exposure estimates when estimating cancer risks from early life
(<16 years of age) exposure to 2-nitropropane. Cancer risks are derived for each age group and
summed across age groups to obtain the total risk for the exposure period of interest.
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APPENDIX B. DATA TABLES
Table B-l. Observed/Expected Deaths among Workers Employed at a 2-Nitropropane
Facility between l/l/1955-7/l/1977a


Exposure Group Category0
Parameterb
Direct + Indirect
Indirect Only
No Exposure
White male workers
n = 325
n = 331
n = 410
All causes of death
11/17.4
29/37.3
54/55.6
All cancer
3/3.2
4/7.3
8/10.2
Lymphatic cancer
0/0.1
0/0.3
2/0.4
Circulatory cancer
5/7.0
15/17.9
26/25.7
External cancer
3/4.0
7/5.3
12/9.4
Residual cancer
0/3.2
3/6.8
8/10.3
Black male workers
n = 33
« = 28
n = 207
All causes of death
0/1.3
0/3.7
27/35.6
All cancer
0/0.2
0/0.7
4/5.1
Lymphatic cancer
0/0.0
0/0.0
2/0.5
Circulatory cancer
0/0.5
0/1.6
12/12.9
External cancer
0/0.2
0/0.6
9/8.4
Residual cancer
0/0.4
0/0.8
2/9.2
Female workers
n = 14
n = l
n= 126
All causes of death
2/0.4
0/0.1
6/2.4
All cancer
1/0.1
0/0.0
3/0.7
Lymphatic cancer
0/0.0
0/0.0
0/0.1
Circulatory cancer
0/0.1
0/0.0
1/0.5
External cancer
1/0.1
0/0.0
1/0.6
Residual cancer
0/0.1
0/0.1
1/0.6
aMiller and Temple (1980).
bData are observed/expected (based on U.S. general population).
°Job titles were used to place workers in exposure categories; exposure levels by categories were not reported.
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Table B-2. Body and Liver Weight in Male Crl:CD (SD) Rats Administered
2-Nitropropane via Gavage for 14 or 28 Days3
Parameterb'c
Dose Group, mg/kg-d (ADD)
0
5(5)
20 (20)
40 (40)
Body weight (g)
14 d
28 d
283.5 ±7.5
331.8 ±20.8
295.8 ± 20.2 (+4%)
332.7 ± 24.6 (+0.3%)
280.8	± 18.4 (-1%)
307.9	± 25.2 (-7%)
261.6 ±20.4 (-8%)
305.5 ± 34.0 (-8%)
Relative liver weight (% BW)
14 d
28 d
3.19 ± 0.21
2.91 ±0.09
3.17 ±0.37 (-0.6%)
2.98 ± 0.23 (+2%)
3.29 ±0.28 (+3%)
3.32 ±0.20* (+14%)
3.54 ±0.24 (+11%)
3.60 ±0.19* (+24%)
aKawakami et al. (2015).
bData are mean ± SD for five rats/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Dunnett's test (p < 0.05), as reported by the study authors.
ADD = adjusted daily dose; BW = body weight; SD = standard deviation.
Table B-3. Serum Chemistry in Male Crl:CD (SD) Rats Administered 2-Nitropropane via
Gavage for 14 or 28 Days3
Parameterb'c
Dose Group, mg/kg-d (ADD)
0
5(5)
20 (20)
40 (40)
ALT (IU/L)
14 d
28 d
30.4 ±3.7
27.9 ± 1.9
29.1 ± 1.2 (-4%)
30.1 ±3.0 (+8%)
25.7 ±3.3 (-16%)
25.1 ±2.2 (-10%)
31.7 ±4.5 (+4%)
28.4 ± 5.4 (+2%)
AST (IU/L)
14 d
28 d
76.3 ±4.6
79.5 ±9.9
79.5 ± 9.1 (+4%)
82.3 ± 2.9 (+4%)
73.5	±5.5 (-4%)
82.6	±3.5 (+4%)
92.3 ± 12.9* (+21%)
93.0 ± 12.3 (+17%)
ChE (IU/L)
14 d
28 d
58 ± 12
51 ± 11
55 ± 12 (-5%)
52 ± 14 (+2%)
70 ± 16 (+21%)
76 ±31 (+49%)
106 ± 24* (+83%)
137 ± 27* (+169%)
GGT (IU/L)
14 d
28 d
0.9 ±0.2
0.4 ±0.2
0.8 ±0.1 (-11%)
0.4 ± 0.2 (0%)
0.9 ± 0.2 (0%)
0.7 ± 0.2 (+75%)
1.2	±0.2* (+33%)
1.3	±0.7* (+225%)
aKawakami et al. (2015).
bData are mean ± SD for five rats/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Dunnett's test (p < 0.05), as reported by the study authors.
ADD = adjusted daily dose; ALT = alanine transaminase; AST = aspartate aminotransferase; ChE = cholinesterase;
GGT = y-glutamyl transferase; SD = standard deviation.
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Table B-4. Gross and Microscopic Liver Findings in Male Crl:CD (SD) Rats Administered
2-Nitropropane via Gavage for 14 or 28 Days3
Parameterb
Dose Group, mg/kg-d (ADD)
0
5(5)
20 (20)
40 (40)
Pale livers
14 d
28 d
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
1/5 (20%)
5/5 (100%)
5/5 (100%)
Hypertrophy of hepatocytes, diffuse
14 d
28 d
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
2/5 (40%)+
0/5 (0%)
5/5 (100%)++
Focus of altered hepatocyte, basophilic
14 d
28 d
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
4/5 (80%)+
Anisokaryosis of hepatocyte
14 d
28 d
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
0/5 (0%)
2/5 (40%)+
aKawakami et at (2015).
bValues denote number of animals showing changes + total number of animals examined (% incidence); severity of
lesions indicated by + (minimal) and ++ (mild).
ADD = adjusted daily dose.
Table B-5. Body and Liver Weight and Serum Chemistry in Male F344 Orally
Administered 2-Nitropropane for 28 Days3
Parameterb'c
Dose Group, mg/kg-d (ADD)
0
40 (40)
Body weight (g)
201.8 + 4.9
202.5+ 11.8 (+0.3%)
Absolute liver weight (g)
8.3 + 0.2
9.8 + 0.7* (+18%)
AST (units not reported)
63 + 5.4
64.8 + 4.8 (+3%)
ALT (units not reported)
48 + 3.8
43.5+ 2.9 (-9%)
ALP (units not reported)
1,909 + 124.2
1,870.3 + 77.2 (-2%)
aNakavama et al. (2006).
bData are mean ± measure of variance (not defined); n = 4/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control (p < 0.05), as reported by the study authors (method not reported).
ADD = adjusted daily dose; ALP = alkaline phosphatase; ALT = alanine aminotransferase; AST = aspartate
aminotransferase.
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Table B-6. Select Serum Chemistry and Hepatic Enzyme Activity in Male Wistar Rats
Orally Administered 2-Nitropropane for 2 Weeks3
Parameterb'c
Dose Group, mg/kg-d (ADD)
0
120 (51.4)
Experiment 1
Plasma ALT (U/L)
63.4 ±6.0
169.5 ± 17.0* (+167%)
Plasma AST (U/L)
148.3 ±24.3
188.2 ± 64.8* (+27%)
Plasma GGT (U/L)
4.8 ±0.9
24.5 ±4.2* (+410%)
Plasma urea (mg/dL)
48.5 ± 12.2
60.8 ± 14.0* (+25%)
Hepatic catalase activity (U/mg of protein)
24.3 ±2.71
10.5 ± 2.62* (-57%)
Experiment 2
Plasma ALT (U/L)
62.6 ± 8.0
142.5 ± 5.87* (+128%)
Plasma AST (U/L)
151.2 ± 14.3
252.2 ± 34.8* (+67%)
Plasma GGT (U/L)
5.75 ±0.85
22.6 ± 1.4* (+293%)
Plasma urea (mg/dL)
50.5 ± 1.84
71.2 ±7.26* (+41%)
Hepatic catalase activity (U/mg of protein)
23.1 ±3.43
14.0 ±2.51 (-39%)
aWilhelmet al. (2009).
bData are mean± SD; n = 8-14/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by two-way ANOVA with Duncan's post hoc multiple range test (p < 0.05),
as reported by the study authors.
ADD = adjusted daily dose; ALT = alanine aminotransferase; ANOVA = analysis of variance; AST = aspartate
aminotransferase; GGT = y glutamyl transferase; SD = standard deviation.
Table B-7. Incidence of Tumors in Male S-D Rats Administered 2-Nitropropane
via Gavage for 16 Weeks3

Dose Group, mg/kg-d (ADD) [HED]
Parameterb
0
90 (39) [9.8]
Liver tumors
Benign tumors
Malignant hepatocarcinomas
1/29 (3%)
0/29 (0%)
4/22 (18%)
22/22** (100%)
Lung tumors (metastases from liver tumors)
0/29 (0%)
4/22 (18%)
Gastrointestinal system
Stomach papilloma
Colon adenocarcinoma
0/29 (0%)
0/29 (0%)
1/22 (5%)
1/22 (5%)
Skin tumors
1/29 (3%)
0/22 (5%)
aFiala et al. (1987b).
bValues denote number of animals showing changes + total number of animals examined (% incidence).
**Significantly different from control (p < 0.001), as reported by the study authors (statistical method not
specified).
ADD = adjusted daily dose; HED = human equivalent dose; S-D = Sprague-Dawley.
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Table B-8. Body Weight and Select Organ Weight Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 22 Months (7 Hours/Day, 5 Days/Week)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Body weight (g)


1 mo
359 ±30
341 ±41 (-5%)
3 mo
508 ± 48
488 ± 65 (-4%)
6 mo
593 ±65
594 ± 69 (+0.2%)
12 mo
618 ±97
672 ± 60 (+9%)
22 mo
696±121
652 ± 102 (-6%)
Absolute liver weight (g)


1 mo
14.19 ±2.01
13.99 ±2.52 (-1%)
3 mo
18.65 ±2.55
19.04 ± 2.63 (+2%)
6 mo
19.03 ±3.98
21.54 ±3.65 (+13%)
12 mo
16.75 ±6.64
18.59 ±2.92 (+11%)
22 mo
17.10 ±3.05
19.07 ±3.76** (+12%)
Relative liver weight (% BW)


1 mo
3.95 ±0.39
4.08 ± 0.45 (+3%)
3 mo
3.67 ±0.43
3.93 ± 0.46 (+7%)
6 mo
3.19 ± 0.50
3.73 ±0.49* (+17%)
12 mo
2.70 ±0.39
2.78 ± 0.46 (+3%)
22 mo
2.49 ±0.50
2.98 ± 0.78** (+20%)
Absolute kidney weight (g)


1 mo
2.59 ±0.33
2.49 ± 0.37 (-4%)
3 mo
3.23 ±0.33
3.20 ±0.39 (-1%)
6 mo
3.35 ±0.28
3.38 ±0.40 (+0.9%)
12 mo
3.45 ±0.40
3.87 ±0.45* (+12%)
22 mo
4.47 ± 1.13
4.75 ± 1.69 (+6%)
aGriffm et at (1980).
bData are mean ± SD; n = 9-10/group at 1-12 months, and 62-63 for control and 27 for exposed at 22 months.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; SD = standard deviation;
S-D = Sprague-Dawley.
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Table B-9. Body Weight and Select Organ Weight Data for Female S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 22 Months (7 Hours/Day, 5 Days/Week)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Body weight (g)


1 mo
199 ±21
211 ±20 (+6%)
3 mo
283 ± 22
278 ± 24 (-2%)
6 mo
281 ± 15
327 ± 54** (+16%)
12 mo
323 ±43
377 ±63** (+17%)
22 mo
408 ± 83
460 ± 104** (+13%)
Absolute liver weight (g)


1 mo
8.22 ± 1.39
9.09±1.61 (+11%)
3 mo
10.15 ± 1.39
10.12+1.12 (-0.3%)
6 mo
8.92 ±0.88
10.64+ 1.65** (+19%)
12 mo
7.93 ± 1.03
9.74+ 1.44** (+23%)
22 mo
10.73 ± 1.93
12.59 + 2.70** (+17%)
Relative liver weight (% BW)


1 mo
4.11 ±0.39
4.29 + 0.50 (+4%)
3 mo
3.56 ±0.41
3.64 + 0.24 (+2%)
6 mo
3.17 ±0.21
3.27 + 0.27 (+3%)
12 mo
2.47 ±0.23
2.58 + 0.33 (+5%)
22 mo
2.63 ±0.40
2.78 + 0.48 (+6%)
Absolute kidney weight (g)


1 mo
1.47 ±0.12
1.65 + 0.19* (+12%)
3 mo
1.83 ±0.13
1.84+ 0.17 (+0.5%)
6 mo
1.69 ±0.15
1.80 + 0.21 (+7%)
12 mo
2.17 ±0.35
2.56 + 0.56 (+18%)
22 mo
2.71 ±0.53
2.85 + 0.48 (+5%)
aGriffm et at (1980).
bData are mean ± SD; n = 9-10/group at 1-12 months, and 44-48 for control and 29 for exposed at 22 months.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; SD = standard deviation;
S-D = Sprague-Dawley.
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Table B-10. Select Hepatic Clinical Chemistry Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 22 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Serum ALT (U/L)
1 mo
3 mo
6 mo
12 mo
22 mo
17 ±3
28 ±8
38 ± 15
15 ± 12
19 ± 13
21 ± 3 (+24%)
24 ± 4 (-14%)
23 ± 10* (-40%)
17 ± 10 (+13%)
20 ± 9 (+5%)
Serum OCT (activity/mL)
1 mo
3 mo
6 mo
12 mo
22 mo
0.391 ±0.020
0.257 ±0.090
0.376 ±0.084
0.280 ±0.090
0.281 ±0.114
0.353 ± 0.090 (-10%)
0.137 ±0.041** (-47%)
0.276 ±0.091* (-27%)
0.400 ±0.120* (+43%)
0.291 ±0.104 (+4%)
aGriffm et at (1980).
bData are mean ± SD; n = 7-10/group at 1-12 months, and 58-61 for control and 26-27 for exposed at 22 months.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
ALT = alanine aminotransferase (glutamic-pyruvic transaminase), ER = extrarespiratory; HEC = human equivalent
concentration; OCT = ornithine carbamyl transferase; SD = standard deviation; S-D = Sprague-Dawley.
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Table B-ll. Select Serum T4 Data for S-D Rats Exposed to 2-Nitropropane via Inhalation
for up to 22 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Males
Serum T4 (ng/100 mL)


1 mo
5.7 ± 1.1
4.6 ± 0.8* (-19%)
3 mo
9.7 ±2.1
8.2 ± 1.5 (-15%)
6 mo
7.6 ± 1.2
7.0 ± 0.6 (-8%)
12 mo
4.8 ± 1.5
4.4 ± 0.8 (-8%)
22 mo
3.4 ±3.0
3.5 ±3.7 (+3%)
3-mo exposure; 18-mo recovery"1
NA
5.2 ± 2.5 (+53%)
12-mo exposure; 10-mo recovery"1
NA
3.6 ±3.1 (+6%)
Females
Serum T4 (ng/100 mL)


1 mo
4.3 ± 1.2
4.0 ± 1.1 (-7%)
3 mo
7.2 ± 1.6
7.0 ± 2.6 (-3%)
6 mo
6.8 ±0.7
7.1 ± 0.6 (+4%)
12 mo
3.6 ±0.6
2.0 ± 0.8** (-44%)
22 mo
1.7 ± 1.8
1.7 ± 2.7 (0%)
3-mo exposure; 18-mo recovery"1
NA
5.1 ±2.8** (+200%)
12-mo exposure; 10-mo recovery"1
NA
4.6 ±2.0** (+171%)
aGriffm et at (1980).
bData are mean ± SD; n = 7-10/sex/group at 1-12 months; n = 63 for control males, 48 for control females, and
27-28 for exposed at 22 months; n = 9/group in recovery groups.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 22 months.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
HEC = human equivalent concentration; ER = extrarespiratory; NA = not applicable; SD = standard deviation;
S-D = Sprague-Dawley; T4 = thyroxine.
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Table B-12. Select Hematological Data for Male S-D Rats Exposed to 2-Nitropropane via
Inhalation for up to 22 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Methemoglobulin (mg/dL)d
6 mo
12 mo
22 mo
38 ± 18
26 ± 11
19 ± 13
20 ± 13** (-47%)
23 ± 11 (-12%)
18 ± 15 (-5%)
Hb (g/100 mL)
6 mo
12 mo
22 mo
3-mo exposure; 19-mo recovery6
12-mo exposure; 10-mo recovery6
15.5 ±0.9
15.7 ±0.7
14.9 ±2.5
NA
NA
16.3	± 1.2 (+5%)
16.6 ± 0.7** (+6%)
15.0 ± 2.8 (+0.7%)
15.4	± 1.5 (+3%)
13.8 ±2.5 (-7%)
Hct (%)
6 mo
12 mo
22 mo
3-mo exposure; 19-mo recovery6
12-mo exposure; 10-mo recovery6
44.6 ±3.2
45.5 ± 1.4
41.0 ±6.8
NA
NA
44.6 ± 1.8(0%)
47.6 ± 2.5* (+5%)
41.1 ±7.3 (+0.2%)
43.2 ±3.1 (+5%)
39.1 ±5.4 (-5%)
Erythrocyte count (106 cells/mm3)
6 mo
12 mo
22 mo
3-mo exposure; 19-mo recovery6
12-mo exposure; 10-mo recovery6
5.4 ±0.8
7.8 ±0.6
5.2 ± 1.5
NA
NA
6.8 ± 1.0** (+26%)
8.1±0.5 (+4%)
4.7+ 1.2 (-10%)
7.3 + 1.0** (+40%)
6.4+1.3 (+23%)
Leukocyte count (103 cells/mm3)
6 mo
12 mo
22 mo
3-mo exposure; 19-mo recovery6
12-mo exposure; 10-mo recovery6
4.4	±0.7
4.9 ± 1.9
5.5	±2.6
NA
NA
5.7 + 0.9** (+30%)
5.7+ 1.4 (+16%)
6.3 + 4.0 (+15%)
4.3 + 0.4 (-22%)
4.7 + 2.3 (-15%)
aGriffin et at (1980).
bData are mean ± SD; n = 9-10/group at 6 or 12 months; n = 53-54 for controls and 26-27 for exposed at
22 months; n = 6/group in recovery groups. No significant findings were found in any parameter at 1- or 3-month
sacrifice (data not shown above).
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dRecovery group data for methemoglobin not reported for males.
eData for recovery groups compared with control group data at 22 months.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
Hb = hemoglobin; Hct = hematocrit; HEC = human equivalent concentration; ER = extrarespiratory; NA = not
applicable; SD = standard deviation; S-D = Sprague-Dawley.
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September 2019
Table B-13. Select Hematological Data for Female S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 22 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
77.8 (16.2)
Methemoglobulin (mg/dL)


6 mo
52 ±24
38 ± 11 (-27%)
12 mo
26 ± 17
27 ± 21 (+4%)
22 mo
15 ± 13
13 ± 10 (-13%)
3-mo exposure; 19-mo recoveryd
NA
24 ± 14 (+60%)
12-mo exposure; 10-mo recovery"1
NA
33 ± 20** (+120%)
Hct (%)


6 mo
43.2 ± 1.6
45.4 ± 1.8* (+5%)
12 mo
43.9 ± 1.5
45.8±1.2** (+4%)
22 mo
44.7 ±3.6
45.5 + 5.3 (+2%)
3-mo exposure; 19-mo recovery"1
NA
44.0 + 3.3 (-2%)
12-mo exposure; 10-mo recovery"1
NA
41.8+ 9.2 (-7%)
Erythrocyte count (106 cells/mm3)


6 mo
4.5 ±0.5
4.9 + 0.7 (+9%)
12 mo
6.3 ±0.5
7.3 + 1.0* (+16%)
22 mo
5.9 ± 1.4
6.2 + 1.2 (+5%)
3 mo-exposure; 19-mo recovery"1
NA
6.7+ 1.8 (+14%)
12-mo exposure; 10-mo recovery"1
NA
6.5+ 1.9 (+10%)
Leukocyte count (103 cells/mm3)


6 mo
3.2 ± 1.0
4.1 + 1.2 (+28%)
12 mo
2.8 ±0.8
3.4+1.3 (+21%)
22 mo
3.7 ± 1.6
4.6 + 2.5 (+24%)
3-mo exposure; 19-mo recovery"1
NA
5.3 + 2.6* (+43%)
12-mo exposure; 10-mo recovery"1
NA
5.1+2.3* (+38%)
aGriffm et at (1980).
bData are mean ± SD; n = 9-10/group at 6 or 12 months; n = 43-44 for controls and 27-28 for exposed at
22 months; n = 9/group in recovery groups. No significant findings were found in any parameter at 1- or 3-month
sacrifice (data not shown above).
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 22 months.
* Significantly different from control by Student's /-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
Hct = hematocrit; HEC = human equivalent concentration; ER = extrarespiratory; NA = not applicable;
SD = standard deviation; S-D = Sprague-Dawley.
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Table B-14. Incidence of Hepatic Lesions in S-D Rats Exposed to 2-Nitropropane via
Inhalation for up to 22 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HEC in mg/m3)
Parameterb
0
77.8 (16.2)
Male
Focal vacuolization of hepatocytes
Focal areas of hepatocellular nodules
Liver congestion
22/125 (18%)
2/125 (2%)
1/125 (0.8%)
58/125* (46%)
10/125* (8%)
8/125* (6%)
Female
Focal vacuolization of hepatocytes
Focal areas of hepatocellular nodules
Liver congestion
18/125 (14%)
1/125 (0.8%)
0/125 (0%)
19/124 (15%)
3/124 (2%)
7/124* (6%)
aGriffm et at (1980).
bValues denote number of animals showing changes total number of animals examined (% incidence); all animals
from the study were combined for reporting of lesions by study authors; timing of the lesions (interim, terminal, or
recovery sacrifice) was not reported.
* Significantly different from control by Fisher's exact test (p < 0.05), conducted for this review.
HEC = human equivalent concentration; S-D = Sprague-Dawley.
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September 2019
Table B-15. Body, Liver, and Kidney Weight Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Body weight (g)
2d
10 d
1 mo
3 mo
6 mo
151 ±5.2
209 ± 11.5
313 ± 10.6
455 ± 14.7
579 ± 16.1
153 ± 4.0 (+1%)
223 ± 6.0 (+7%)
330 ± 5.0 (+5%)
486 ± 15.4 (+7%)
579 ± 22.6 (0%)
97 ± 1.7*** (-36%)
137 ±8.3*** (-34%)
221 ±6.9*** (-29%)
405 ± 16.5* (-11%)
513 ±17.0* (-11%)
Absolute liver weight (g)
2d
10 d
1 mo
3 mo
6 mo
5.9 ±0.12
7.6 ±0.16
9.5 ±0.35
11.8 ±0.40
15.02 ±0.865
5.5 ±0.13 (-7%)
7.3 ± 0.28 (-4%)
10.3 ± 0.35 (+8%)
13.0 ±0.48 (+10%)
14.42 ± 0.824 (-4%)
3.8 ±0.11*** (-36%)
6.3 ± 0.29*** (-17%)
10.0 ± 0.37 (+5%)
16.7 ± 0.85*** (+42%)
36.63 ± 5.787*** (+144%)
Relative liver weight (% BW)
2d
10 d
1 mo
3 mo
6 mo
4.0 ±0.13
3.8 ±0.32
3.0 ±0.05
2.6 ±0.04
2.6 ±0.156
3.7 ±0.12 (-8%)
3.3 ±0.06 (-13%)
3.1 ±0.08 (+3%)
2.7 ± 0.05 (+4%)
2.48 ± 0.056 (-5%)
4.0 ± 0.06 (0%)
4.7 ±0.13* (24%)
4.5 ±0.11*** (+50%)
4.1 ±0.19*** (+58%)
7.18 ± 1.132*** (+176%)
Absolute kidney weight (g)
2d
10 d
1 mo
3 mo
6 mo
2.1 ±0.13
2.3	±0.12
2.5 ±0.10
3.4	±0.16
3.85 ±0.187
1.8	±0.09 (-14%)
1.9	±0.13* (-17%)
2.8 ± 0.08* (+12%)
3.7 ±0.15 (+9%)
3.67 ±0.149 (-5%)
1.0 ±0.02*** (-52%)
1.3 ±0.06*** (-44%)
2.0 ± 0.09*** (-20%)
3.1 ±0.10 (-9%)
3.7 ±0.117 (-4%)
Relative kidney weight (% BW)
2d
10 d
1 mo
3 mo
6 mo
1.4 ±0.08
1.2 ±0.12
0.8 ±0.01
0.7 ±0.03
0.67 ±0.036
1.2 ±0.09 (-14%)
0.8 ± 0.06* (-33%)
0.9 ± 0.02* (+13%)
0.8 ± 0.02 (+14%)
0.64 ±0.014 (-5%)
1.1 ±0.02*** (-21%)
1.0 ±0.04 (-17%)
0.9 ±0.03** (+13%)
0.8 ± 0.02 (+14%)
0.72 ± 0.02 (+8%)
aLewis et at (1979): Ulrich et at (1977).
bData are mean± SEM; n = 8-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's t-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
***Significantly different from control by Student's /-test (p < 0.005), as reported by the study authors.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; S-D = Sprague-Dawley;
SEM = standard error of the mean.
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Table B-16. Clinical Chemistry Data for Male S-D Rats Exposed to 2-Nitropropane via
Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Serum ALT (U/L)
2d
10 d
1 mo
3 mo
6 mo
27 ± 1.6
22 ±0.6
18 ± 1.7
46 ± 10.7
30 ±2.7
42 ± 12 (+56%)
22 ± 0.7 (0%)
18 ± 1.1 (0%)
24 ± 4.7 (-48%)
30 ± 3.2 (0%)
QNS
27 ± 1.7** (+23%)
22 ± 1.1* (+22%)
26 ± 4.7 (-44%)
143 ±46.3* (+377%)
Serum OCT (activity/mL)
2d
10 d
1 mo
3 mo
6 mo
QNS
469 ±93.0
600± 111.8
919 ±245.5
1,050 ±205.1
QNS
502 ± 45.6 (+7%)
678 ± 157.3 (+13%)
835 ± 141.2 (-9%)
800 ± 135.1 (-24%)
QNS
QNS
398 ±41.3 (-34%)
1,117 ±203.8 (+22%)
3,839 ± 1,755.6 (+266%)
Serum T4 (|ig/dL)
2d
10 d
1 mo
3 mo
6 mo
4.4	±0.25
3.5	±0.33
3.8 ±0.23
1.8 ±0.12
2.7 ±0.26
3.5 ±0.33 (-21%)*
3.1	±0.29 (-11%)
4.2	±0.42 (+11%)
2.2	± 0.2 (+22%)
2.3	±0.15 (-15%)
QNS
3.3	± 0.25 (-6%)
3.4	±0.17 (-11%)
3.3 ±0.15* (+83%)
3.6 ±0.38 (+33%)
aLewis et at (1979): Ulrich et at (1977).
bData are mean± SEM; n = 5-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's t-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
ALT = alanine aminotransferase (glutamic-pyruvic transaminase); ER = extrarespiratory; HEC = human equivalent
concentration; OCT = ornithine carbamyl transferase; QNS = quantity of available material not sufficient for
analysis; S-D = Sprague-Dawley; SEM = standard error of the mean; T4 = thyroxine.
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September 2019
Table B-17. Lung Weight and Edema Data for Male S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECpu in mg/m3)d
0
98 (70)
754 (581)
Absolute lung weight (g)
2d
10 d
1 mo
3 mo
6 mo
1.9 ± 0.15
2.1	±0.07
2.2	±0.15
3.2 ±0.45
2.92 ±0.115
1.6	±0.07 (-16%)
1.7	±0.15* (-19%)
2.3 ±0.1 (+5%)
2.9 ±0.13 (-9%)
2.85 ±0.14 (-2%)
0.9 ± 0.02*** (-53%)
1.2 ±0.06*** (-43%)
1.6 ±0.08*** (-27%)
2.5 ± 0.07 (-22%)
3.6 ±0.288* (+23%)
Relative lung weight (% BW)
2d
10 d
1 mo
3 mo
6 mo
1.2 ±0.09
1.0 ±0.10
0.7 ±0.02
0.7 ±0.12
0.51 ±0.019
1.0 ±0.07 (-17%)
0.8 ± 0.06 (-20%)
0.7 ± 0.03 (0%)
0.6 ± 0.03 (-14%)
0.5 ± 0.025 (-2%)
0.9 ± 0.02*** (-25%)
0.8 ± 0.04* (-20%)
0.7 ± 0.02 (0%)
0.6 ± 0.02 (-14%)
0.7 ± 0.052*** (+37%)
Lung edema (% water)
2d
10 d
1 mo
3 mo
6 mo
79.3 ±0.31
80.2	±0.31
79.3	±0.38
78.7 ±0.21
79 ±0.3
77.3 ± 1.42 (-3%)
80.7 ± 0.27 (+0.6%)
79.7 ± 0.27 (+0.5%)
79.8 ± 0.3 (+1%)
80.6 ± 1.19 (+2%)
78.3 ± 0.36 (-1%)
78.9 ± 0.29*** (-2%)
81.1 ±0.27*** (+2%)
81.1 ±0.39*** (+3%)
82.9 ± 1.61* (+5%)
aLewis et at (1979): Ulrich et at (1977).
bData are mean ± SEM; n = 10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dHECpu values calculated using 6-month TWA body weight values based on graphically reported body weight data
extracted using Grab It! software.
* Significantly different from control by Student's t-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
***Significantly different from control by Student's /-test (p < 0.005), as reported by the study authors.
BW = body weight; HEC = human equivalent concentration; PU = pulmonary; S-D = Sprague-Dawley;
SEM = standard error of the mean; TWA = time-weighted average.
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September 2019
Table B-18. Thyroid and Brain Weight Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Absolute thyroid weight (g)
2d
10 d
1 mo
3 mo
6 mo
0.0153 ±0.00212
0.0206 ±0.00186
0.0232 ±0.00156
0.028 ±0.00219
0.0225 ±0.00127
0.0175 ±0.0019 (+14%)
0.0166 ±0.0015 (-19%)
0.0216 ±0.00137 (-7%)
0.0306 ± 0.00225 (+9%)
0.0232 ±0.00291 (+3%)
0.0245 ±0.00251* (+60%)
0.0231 +0.00281 (+12%)
0.0262+ 0.0017 (+13%)
0.0233 +0.00261 (-17%)
0.0253 +0.00118 (+12%)
Relative thyroid weight (% BW)
2d
10 d
1 mo
3 mo
6 mo
0.0104 ±0.00166
0.0106 ±0.00162
0.0075 ± 0.00066
0.0062 ± 0.00058
0.0039 ±0.00025
0.0117 ±0.00141 (+13%)
0.0075 ± 0.00061 (-29%)
0.0066 ± 0.00042 (-12%)
0.0063 ± 0.00047 (+2%)
0.0042 ± 0.00057 (+8%)
0.0254 + 0.00272*** (+144%)
0.0181+ 0.00277* (+71%)
0.0118 + 0.00065*** (+57%)
0.0057 + 0.00053 (-8%)
0.0049 + 0.00019 (+26%)
Absolute brain weight (g)
2d
10 d
1 mo
3 mo
6 mo
2.1	± 0.10
2.0 ±0.08
1.7 ±0.06
2.2	±0.03
2.2 ±0.08
1.5 ±0.06*** (-29%)
1.5 ±0.13*** (-25%)
1.8 ± 0.07 (+6%)
2.2 ± 0.05 (0%)
2.2 ± 0.05 (0%)
1.5 + 0.04*** (-28%)
1.5 + 0.06*** (-25%)
1.6 + 0.06 (-6%)
2.3	+ 0.09 (+5%)
2.4	+ 0.05 (+9%)
Relative brain weight (% BW)
2d
10 d
1 mo
3 mo
6 mo
1.4 ±0.09
0.9 ±0.05
0.6 ±0.02
0.5 ±0.02
0.4 ±0.01
1.0 ± 0.05 (-29%)
0.7 ± 0.06* (-22%)
0.5 ± 0.02 (-17%)
0.4 ± 0.01 (-20%)
0.4 ±0.01 (0%)
1.5 + 0.06*** (+7%)
1.1+ 0.08* (+22%)
0.7 + 0.04*** (+17%)
0.6 + 0.03* (+20%)
0.5 + 0.01*** (+25%)
aLewis et at (1979): Ulrich et at (1977).
bData are mean ± SEM; n = 10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Student's t-test (p < 0.05), as reported by the study authors.
**Significantly different from control by Student's /-test (p < 0.01), as reported by the study authors.
***Significantly different from control by Student's /-test (p < 0.005), as reported by the study authors.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; SEM = standard error of the
mean; S-D = Sprague-Dawley.
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September 2019
Table B-19. Hepatic Lesions in Male S-D Rats Exposed to 2-Nitropropane via Inhalation
for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Pericholangitis
2d
10 d
1 mo
3 mo
6 mo
2/10 (20%)
1/10 (10%)
2/10 (20%)
1/10 (10%)
0/10 (0%)
2/10 (20%)
4/10 (40%)
3/10 (30%)
1/10 (10%)
0/10 (0%)
1/10 (10%)
8/10* (80%)
1/10 (10%)
0/9 (0%)
0/10 (0%)
Focal necrosis
2d
10 d
1 mo
3 mo
6 mo
0/10 (0%)
0/10 (0%)
0/10 (0%)
0/10 (0%)
0/10 (0%)
3/10 (30%)
0/10 (0%)
0/10 (0%)
0/10 (0%)
1/10 (10%)
0/10 (0%)
0/10 (0%)
0/10 (0%)
0/9 (0%)
2/10 (20%)
Focal hepatocyte hypertrophy
3 mo
0/10 (0%)
0/10 (0%)
9/9* (100%)
Basophilic foci
3 mo
0/10 (0%)
0/10 (0%)
4/9* (44%)
Focal hepatocyte hyperplasia
3 mo
0/10 (0%)
0/10 (0%)
4/9* (44%)
Clear cell focus
3 mo
0/10 (0%)
0/10 (0%)
1/9(11%)
Hepatocellular necrosis
3 mo
0/10 (0%)
0/10 (0%)
1/9(11%)
Hepatocellular carcinoma
6 mo
0/10 (0%)
0/10 (0%)
10/10* (100%)
Neoplastic nodule
6 mo
0/10 (0%)
0/10 (0%)
10/10* (100%)
aLewis et at (1979): Ulrich et at (1977).
bValues denote number of animals showing changes/total number of animals examined (% incidence).
* Significantly different from control by Fisher's exact test (p < 0.05), as calculated for this review.
ER = extrarespiratory; HEC = human equivalent concentration; S-D = Sprague-Dawley.
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September 2019
Table B-20. Body and Liver Weight Data for Male S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 18 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
312 (65.0)
Body weight (g)


1 mo
326 ± 40
343 ±31 (+5%)
3 mo
511 ± 53
521 ± 54 (+2%)
6 mo
585 ± 47
605 ± 62 (+3%)
9 mo
650 ± 40
673 ± 111 (+4%)
12 mo
651 ±63
672 ± 145 (+3%)
18 mo
710 ±82
553 ±101* (-22%)
3-mo exposure; 15-mo recoveryd
NA
721 ± 99 (+2%)
6-mo exposure; 12-mo recoveryd
NA
626 ± 90* (-12%)
9-mo exposure; 9-mo recovery"1
NA
534 ± 153* (-25%)
Absolute liver weight (g)


1 mo
13.61 ± 1.35
15.36 ± 2.27 (+13%)
3 mo
17.73 ±0.25
21.73 ±4.14* (+23%)
6 mo
19.38 ±3.30
23.92 ±4.22* (+23%)
9 mo
18.92 ±2.20
28.95 ±7.93* (+53%)
12 mo
21.35 ±4.83
41.16 ±22.52* (+93%)
18 mo
16.89 ±2.44
52.19 ±29.05* (+209%)
3-mo exposure; 15-mo recovery"1
NA
25.37 ± 8.29* (+50%)
6-mo exposure; 12-mo recovery"1
NA
32.46 ± 16.50* (+92%)
9-mo exposure; 9-mo recovery"1
NA
57.77 ±31.81* (+242%)
Relative liver weight (% BW)


1 mo
4.21 ±0.55
4.46 ± 0.39 (+6%)
3 mo
3.46 ±0.25
4.15 ±0.58* (+20%)
6 mo
3.30 ±0.35
3.94 ±0.44* (+19%)
9 mo
2.91 ±0.25
4.28 ± 0.92* (+47%)
12 mo
3.26 ±0.53
6.45 ± 4.30* (+98%)
18 mo
2.39 ±0.34
10.22 ±6.63* (+328%)
3-mo exposure; 15-mo recovery"1
NA
3.65 ± 1.51* (+53%)
6-mo exposure; 12-mo recovery"1
NA
5.26 ± 2.76* (+120%)
9-mo exposure; 9-mo recovery"1
NA
11.36 ±6.20* (+375%)
aGriffm et at (1979).
bData are mean ± SD; n = 10/group at 1-12 months, 62 for control and 23 for exposed at 18 months, and 7-8/group
in recovery groups.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 18 months.
* Significantly different from control by two-tailed Student's /-test (p < 0.05), conducted for this review.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable;
SD = standard deviation; S-D = Sprague-Dawley.
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September 2019
Table B-21. Body and Liver Weight Data for Female S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 18 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
312 (65.0)
Body weight (g)


1 mo
224 ± 20
214 ±21 (-5%)
3 mo
292 ± 27
281 ± 22 (-4%)
6 mo
317 ±49
318 ± 15 (+0.3%)
9 mo
344 ±35
340 ± 44 (-1%)
12 mo
365 ±53
379 ± 90 (+4%)
18 mo
435 ± 92
421 ± 77 (-3%)
3-mo exposure; 15-mo recoveryd
NA
419 ±61 (-4%)
6-mo exposure; 12-mo recoveryd
NA
422 ± 111 (-3%)
9-mo exposure; 9-mo recovery"1
NA
427 ± 58 (-2%)
Absolute liver weight (g)


1 mo
9 ±0.91
8.42 ± 1.27 (-6%)
3 mo
8.56 ±2.91
9.87 ± 0.97 (+15%)
6 mo
10.63 ± 1.3
11.32 ± 1.10 (+7%)
9 mo
11.39 ± 1.46
10.64 ± 1.58 (-7%)
12 mo
11.82 ± 2.15
14.22 ±2.11 (+20%)
18 mo
10.50 ±2.18
11.43±1.95 (+9%)
3-mo exposure; 15-mo recovery"1
NA
10.36+ 1.52 (-1%)
6-mo exposure; 12-mo recovery"1
NA
10.77 + 2.92 (+3%)
9-mo exposure; 9-mo recovery"1
NA
11.75 + 3.35 (+12%)
Relative liver weight (% BW)


1 mo
4.02 ±0.20
3.93 +0.28 (-2%)
3 mo
3.26 ±0.30
3.51+0.20 (+8%)
6 mo
3.39 ±0.52
3.55 + 0.28 (+5%)
9 mo
3.31 ± 0.35
3.13+0.16 (-5%)
12 mo
3.26 ±0.47
3.50 + 0.25 (+7%)
18 mo
2.42 ±0.30
2.73 + 0.31 (+13%)
3-mo exposure; 15-mo recovery"1
NA
2.48 + 0.23 (+3%)
6-mo exposure; 12-mo recovery"1
NA
2.60 + 0.54 (+7%)
9-mo exposure; 9-mo recovery"1
NA
2.73 + 0.51 (+13%)
aGriffm et at (1979).
bData are mean ± SD; n = 8-10/group at 1-12 months, 67 for control and 30 for exposed at 18 months, and
10/group in recovery groups.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 18 months.
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable;
SD = standard deviation; S-D = Sprague-Dawley.
95
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September 2019
Table B-22. Select Hepatic Clinical Chemistry Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 18 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
312 (65.0)
Serum ALT (U/L)


1 mo
16 ±2
14 ± 2* (-13%)
3 mo
23 ± 11
17 ± 8 (-26%)
6 mo
30 ± 16
18 ± 7* (-40%)
9 mo
29 ±7
23 ± 7 (-21%)
12 mo
22 ±7
25 ± 19 (+14%)
18 mo
17 ± 13
78 ± 97* (+359%)
3-mo exposure; 15-mo recoveryd
NA
17+11 (0%)
6-mo exposure; 12-mo recoveryd
NA
38 + 31* (+124%)
9-mo exposure; 9-mo recovery"1
NA
397 + 627* (+2,235%)
aGriffm et at (1979).
bData are mean ± SD; n = 7-10/group at 1-12 months, 62 for control and 23 for exposed at 18 months, and
7-8/group in recovery groups.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 18 months.
* Significantly different from control by Student's /-test (p < 0.05), as conducted for this review.
ALT = alanine aminotransferase (glutamic-pyruvic transaminase), ER = extrarespiratory; HEC = human equivalent
concentration; NA = not applicable; SD = standard deviation; S-D = Sprague-Dawley.
96
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September 2019
Table B-23. Kidney Weight Data for S-D Rats Exposed to 2-Nitropropane via Inhalation
for up to 18 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
312 (65.0)
Absolute kidney weight (g) in males


1 mo
1.25 ±0.16
1.29 ±0.17 (+3%)
3 mo
3.08 ±0.22
3.22 ±0.31 (+5%)
6 mo
3.39 ±0.45
3.98 ±0.57 (+17%)
9 mo
3.68 ±0.37
4.19 ±0.65 (+14%)
12 mo
4.22 ± 1.04
4.02 ± 0.54 (-5%)
18 mo
4.14 ±0.72
4.43 ± 0.97 (+7%)
3-mo exposure; 15-mo recoveryd
NA
4.55 ±0.81 (+10%)
6-mo exposure; 12-mo recoveryd
NA
4.40 ± 0.78 (+6%)
9-mo exposure; 9-mo recovery"1
NA
4.48 ± 1.42 (+8%)
Absolute kidney weight (g) in females


1 mo
0.85 ±0.08
0.81 ±0.04 (-5%)
3 mo
1.70 ±0.15
1.85 ±0.16 (+9%)
6 mo
2.00 ±0.16
2.19±0.21 (+10%)
9 mo
2.31 ±0.28
2.03 + 0.24 (-12%)
12 mo
2.39 ±0.29
2.52 + 0.45 (+5%)
18 mo
2.46 ±0.73
2.66 + 0.37 (+8%)
3-mo exposure; 15-mo recovery"1
NA
2.5 + 0.33 (+2%)
6-mo exposure; 12-mo recovery"1
NA
2.58 + 0.47 (+5%)
9-mo exposure; 9-mo recovery"1
NA
2.87 + 0.5 (+17%)
aGriffm et at (1979).
bData are mean ± SD; n = 10/group at 1-12 months, 62 for control and 23 for exposed at 18 months, and 7-8/group
in recovery groups; relative kidney weights not reported by study authors.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData for recovery groups compared with control group data at 18 months.
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; SD = standard deviation;
S-D = Sprague-Dawley.
97
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September 2019
Table B-24. Time-Course Data for Incidence of Grossly Observed Hepatic Masses and
Nodules (Combined) in S-D Rats Exposed to 2-Nitropropane via Inhalation for up to
18 Months (7 Hours/Day, 5 Days/Week^
a

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb
0
312 (65.0)
Male
1 mo
0/10 (0%)
0/10 (0%)
3 mo
0/10 (0%)
0/10 (0%)
6 mo
0/10 (0%)
0/10 (0%)
9 mo
0/10 (0%)
6/16 (28%)
12 mo
0/10 (0%)
5/10* (50%)
18 mo
0/62 (0%)
22/23* (96%)
3-mo exposure; 15-mo recovery0
NA
6/10* (60%)
6-mo exposure; 12-mo recovery0
NA
7/10* (70%)
9-mo exposure; 9-mo recovery0
NA
7/10* (70%)
Found dead or sacrificed moribund
0/13 (0%)
11/16* (69%)
Femaled
1 mo
0/10 (0%)
0/10 (0%)
3 mo
0/10 (0%)
0/10 (0%)
6 mo
0/10 (0%)
0/10 (0%)
9 mo
0/10 (0%)
1/10 (10%)
12 mo
0/10 (0%)
0/10 (0%)
18 mo
0/68 (0%)
2/30 (7%)
3-mo exposure; 15-mo recovery0
NA
0/10 (0%)
6-mo exposure; 12-mo recovery0
NA
0/10 (0%)
9-mo exposure; 9-mo recovery0
NA
2/10 (20%)
Found dead or sacrificed moribund
0/7 (0%)
0/5 (0%)
aGriffm et at (1979).
bValues denote number of animals showing changes total number of animals examined (% incidence); all hepatic
lesions were combined by study authors.
°Exposed incidence in recovery group compared with control group at 18 months.
dIncidences as reported by the study authors in Table 16 of the Final Report; some incidence data appear to conflict
with the incidence data at 18 months found in the Pathology Report (see Table B-16 of the Pathology Report).
* Significantly different from control by Fisher's exact test (p < 0.05), conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; S-D = Sprague-Dawley.
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September 2019
Table B-25. Incidence of Hepatic and Renal Lesions Identified by Histopathological
Examination in S-D Rats Exposed to 2-Nitropropane via Inhalation for 18 Months
(7 Hours/Day, 5 Days/Week)'1

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb
0
312 (65.0)
Male
Hepatic lesions at 18 mo
Focal necrosis
Nodular hyperplasia
Vacuolar degeneration
Hepatocellular carcinoma
2/63 (3%)
0/63 (0%)
7/63 (11%)
0/63 (0%)
10/23* (43%)
22/23* (96%)
15/23* (65%)
7/23* (30%)
Renal lesions at 18 mo
Renal calcification
16/63 (25%)
23/23* (100%)
Female
Hepatic lesions at 18 mo
Focal necrosis
Nodular hyperplasia
Vacuolar degeneration
Hepatocellular carcinoma
0/67 (0%)
1/67 (1%)
2/67 (3%)
0/67 (0%)
0/30 (0%)
6/30* (20%)
11/30* (37%)
0/30 (0%)
Renal lesions at 18 mo
Renal calcification
34/67 (51%)
21/30 (70%)
aGriffm et at (1979).
bValues denote number of animals showing changes total number of animals examined (% incidence).
* Significantly different from control by Fisher's exact test (p < 0.05), conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; S-D = Sprague-Dawley.
99
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September 2019
Table B-26. Body Weight and Select Organ Weight Data for Male S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 Days/Week)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Body weight (g)


0 wk
138 ± 13
131 ± 14 (-5%)
2 wk
256 ± 25
224 ± 25* (-13%)
4 wk
326 ±31
303 ± 25 (-7%)
6 wk
395 ±35
351 ±27* (-11%)
13 wk
522 ± 44
476 ± 49* (-9%)
27 wk
616 ±69
590 ± 62 (-4%)
Relative liver weight (% BW)


10 d
3.93 ±0.59
4.45 ± 0.52 (+13%)
1 mo
4.12 ±0.34
4.57 ±0.34 (+11%)
3 mo
3.41 ±0.32
4.37 ± 0.26** (+28%)
6 mo
3.45 ±0.30
4.95± 1.48** (+44%)
3 mo + 3-mo recovery"1
NA
4.45+ 1.16 (+29%)
Relative kidney weight (% BW)


10 d
0.407 ± 0.024
0.429 + 0.032 (+5%)
1 mo
0.371 ±0.019
0.375 +0.016 (+1%)
3 mo
0.310 ± 0.011
0.337 + 0.024** (+9%)
6 mo
0.305 ±0.027
0.302 + 0.023 (-1%)
3 mo + 3-mo recovery"1
NA
0.292 + 0.014 (-4%)
Relative brain weight (% BW)


10 d
0.676 ±0.091
0.807 + 0.068** (+19%)
1 mo
0.552 ±0.036
0.571 +0.053 (+3%)
3 mo
0.397 ±0.028
0.411 +0.034 (+4%)
6 mo
0.386 ±0.087
0.395 + 0.066 (+2%)
3 mo + 3-mo recovery"1
NA
0.363 + 0.027 (-6%)
aCoulston et al. (1978).
bData are mean± SD; n = 9-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData in recovery group compared with control group at 6 months.
* Significantly different from control by Student's t-test (p < 0.02), conducted for this review.
**Significantly different from control (p < 0.01), as reported by the study authors (unspecified method).
BW = body weight; ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable;
SD = standard deviation; S-D = Sprague-Dawley.
100
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September 2019
Table B-27. Body Weight and Select Organ Weight Data for Female S-D Rats Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 Days/Week)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Body weight (g)


0 wk
105 ± 11
102 ± NLd (-3%)
2 wk
156 ± 16
150 ± NL (-4%)
4 wk
193 ± 19
190 ± NL (-2%)
13 wk
257 ± 26
250 ± NL (-3%)
27 wk
286 ± 32
287 ± NL (+0.3%)
Relative liver weight (% BW)


10 d
4.30 ±0.26
4.34 ± 0.35 (+0.9%)
1 mo
3.93 ±0.29
4.91 ±0.52** (+25%)
3 mo
3.38 ±0.28
4.23 ±0.73** (+25%)
6 mo
3.18 ± 0.32
4.09 ± 0.45** (+29%)
3 mo + 3-mo recovery6
NA
3.37 ±0.25 (+6%)
Relative kidney weight (% BW)


10 d
0.398 ±0.026
0.425 ± 0.046 (+7%)
1 mo
0.373 ±0.029
0.387 ± 0.067 (+4%)
3 mo
0.311 ±0.035
0.340 ± 0.028 (+9%)
6 mo
0.315 ±0.023
0.345 ±0.018 (+10%)
3 mo + 3-mo recovery6
NA
0.328 ± 0.028 (+4)
Relative brain weight (% BW)


10 d
0.989 ±0.065
1.059 ±0.09 (+7%)
1 mo
0.872 ±0.043
0.831 ±0.04 (-5%)
3 mo
0.719 ±0.082
0.772 ± 0.07 (+7%)
6 mo
0.678 ±0.084
0.708 ± 0.08 (+4%)
3 mo + 3-mo recovery6
NA
0.644 ± 0.05 (-5%)
aCoulston et al. (1978).
bData are mean± SD; n = 9-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dSD values for body weight in exposed females was not legible in the available copy of the study report.
eData in recovery group compared with control group at 6 months.
**Significantly different from control (p < 0.01), as reported by the study authors (unspecified method).
BW = body weight; HEC = human equivalent concentration; NA = not applicable; NL = not legible; SD = standard
deviation; S-D = Sprague-Dawley.
101
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September 2019
Table B-28. Select Hematological Data for Male S-D Rats Exposed to 2-Nitropropane via
Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
608 (127)
Leukocyte count (103 cells/mm3)


10 d
7.9 ± 1.1
8.3 ± 1.0 (+5%)
1 mo
7.0 ±2.1
8.6 ± 1.7 (+23%)
2 mo
12.4 ±2.5
13.7 ± 1.5 (+11%)
3 mo
6.5 ± 1.4
7.0 ± 1.8 (+8%)
5 mo
10.0 ± 1.3
12.0±1.5** (+20%)
6 mo
9.4 ±3.4
11.5 + 6.1 (+22%)
3 mo + 3-mo recoveryd
NA
7.5 + 2.9 (-20%)
Packed cell volume (%)


10 d
42 ±3
44 + 2 (+5%)
1 mo
46 ±3
46 + 2 (0%)
2 mo
48 ± 1
47 + 2 (-2%)
3 mo
47 ± 1
45 + 2** (-4%)
5 mo
46 ± 1
46 + 1 (0%)
6 mo
43 ±5
42 + 6 (-2%)
3 mo + 3-mo recovery"1
NA
44 + 2 (+2%)
Prothrombin time (s)


10 d
10.1 ±0.4
11.3+0.6** (+12%)
1 mo
12.4 ±2.1
12.2 + 1.6 (-2%)
2 mo
15.4 ± 1.7
13.7 + 2.4 (-11%)
3 mo
12.9 ±2.7
13.3+2.4 (+3%)
5 mo
21.6 ±8.0
17.1 + 3.3 (-21%)
6 mo
24.5 ±6.8
28.4 + 9.3 (+16%)
3 mo + 3-mo recovery"1
NA
35 + 11.8 (+43%)
aCoulston et al. (1978).
bData are mean ± SD; n = 6-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData in recovery group compared with control group at 6 months.
**Significantly different from control (p < 0.01), as reported by the study authors (unspecified method).
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; SD = standard deviation;
S-D = Sprague-Dawley.
102
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FINAL
September 2019
Table B-29. Select Hematological Data for Female S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
608 (127)
Leukocyte count (103 cells/mm3)


10 d
8.3 ± 1.4
7.3 ± 2.0 (-12%)
1 mo
6.5 ±2.0
7.3 ± 1.9 (+12%)
2 mo
7.9 ±2.8
9.8 ± 2.3 (+24%)
3 mo
5.0 ± 1.8
4.4 ± 1.3 (-12%)
5 mo
7.8 ±2.2
7.7 ± 1.6 (-1%)
6 mo
6.6 ±6.5
4.5 ± 1.4 (-32%)
3 mo + 3-mo recoveryd
NA
4.4 ± 2.2 (-33%)
Packed cell volume (%)


10 d
45 ± 1
44 ± 3 (-2%)
1 mo
46 ±2
45 ± 2 (-2%)
2 mo
45 ±2
47 ± 2 (+4%)
3 mo
45 ±2
44 ± 2 (-2%)
5 mo
45 ±2
45 ± 2 (0%)
6 mo
45 ±3
44 ± 3 (-2%)
3 mo + 3-mo recovery"1
NA
46 ± 2 (+2%)
Prothrombin time (s)


10 d
12.3 ±3.8
11.6 ± NAe (-6%)
1 mo
11.4 ± 1.8
12.0 ± 0.9 (+5%)
2 mo
13.9 ± 1.8
10.9 ± 1.0** (-22%)
3 mo
15.6 ±4.1
16.1 ±7.0 (+3%)
5 mo
37.9 ±33.6
18.0 ± 5.8 (-53%)
6 mo
21.7 ±2.5
19.7 ± 4.8 (-10%)
3 mo + 3-mo recovery"1
NA
23.8 ±8.0 (+10%)
aCoulston et al. (1978).
bData are mean± SD; n = 4-10/group, unless otherwise noted.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dData in recovery group compared with control group at 6 months.
eData reported only for one rat; inadequate for statistical analysis.
**Significantly different from control (p < 0.01), as reported by the study authors (unspecified method).
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; SD = standard deviation;
S-D = Sprague-Dawley.
103
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September 2019
Table B-30. Select Serum Chemistry Data for Male S-D Rats Exposed to 2-Nitropropane
via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
ALT (U/L)


10 d
20 ±5
31 ±4** (+55%)
1 mo
20 ±4
24 ± 5 (+20%)
2 mo
20 ±2
25 ± 5 (+25%)
3 mo
20 ±5
29 ± 5** (+45%)
5 mo
26 ±8
28 ± 7 (+8%)
6 mo
50 ±41
227 ± 560 (+354%)
6 mo (redrawd)
33 ± 13
102 ± 69**(+209%)
3 mo + 3-mo recovery6
NA
41 ±27 (-18%)
AST (U/L)


6 mo
100 ± 28
507 ± 520**(+407%)**
T4 (ng/100 mL)


10 d
8.0 ± 1.9
6.2 ± 1.7 (-23%)
1 mo
5.8 ±0.6
4.6 ± 1.2 (-21%)
2 mo
7.6 ± 1.4
5.6 ± 1.8** (-26%)
3 mo
4.3 ±0.8
2.9 ± 1.0 (-33%)
5 mo
10.9 ±3.7
9.8 ± 0.8 (-10%)
6 mo
2.4 ± 1.6
1.4 ± 0.8 (-42%)
3 mo + 3-mo recovery6
NA
2.4 ± 0.7 (0%)
T3 uptake (%)


10 d
63.4 ± 1.2
65 ± 2.6 (+3%)
1 mo
57.3 ± 1.2
56.9 ± 1.6 (-0.7%)
2 mo
61.3 ± 1.2
61.9 ± 1.2 (+1%)
3 mo
62.3 ±3.4
58.2 ± 1.2** (-7%)
5 mo
62.2 ±3.6
57.8 ± 1.4** (-7%)
6 mo
63.7 ±3.5
58.4 ±3.2** (-8%)
3 mo + 3-mo recovery6
NA
61 ± 1.4 (-4%)
aCoulston et al. (1978).
bData are mean± SD; n = 5-10/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dRepeat blood drawing from additional 10 control and 10 exposed males.
eData in recovery group compared with control group at 6 months.
**Significantly different from control (p < 0.01), as reported by the study authors (unspecified method).
ALT = alanine aminotransferase; AST = aspartate aminotransferase; ER = extrarespiratory; HEC = human
equivalent concentration; NA = not applicable; SD = standard deviation; S-D = Sprague-Dawley;
T3 = triiodothyronine; T4 = thyroxine.
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Table B-31. Non-neoplastic Microscopic Changes in Livers of Male S-D Rats Exposed to
2-Nitropropane via Inhalation for 10 or 30 Days (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Loss of glycogen


10 d
6/10
7/10
30 d
6/10
7/10
Vacuolation


10 d
3/10
8/10
30 d
7/10
8/10
Basophilic hepatocytes present


10 d
0/10
7/10*
30 d
0/10
0/10
Single liver cell necrosis


10 d
0/10
10/10*
30 d
2/10
9/10*
Mitosis


10 d
1/10
6/9*
30 d
1/10
6/10
Bile ductile proliferation


10 d
0/10
6/10*
30 d
0/10
2/10
Focal macrophages


10 d
1/10
0/10
30 d
0/10
0/10
Broken cell walls


10 d
0/10
0/10
30 d
2/10
6/10
aCoulston et al. (1978).
bValues denote number of animals showing changes/total number of animals examined.
'Findings reported as absent (0) or doubtful (±) by the study authors were counted as negative findings; findings
reported as slight (+), moderate (++), or marked (+++) were counted as positive findings.
* Significantly different from control by 2-tailed Fisher's exact test (p < 0.05) conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; S-D = Sprague-Dawley.
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Table B-32. Microscopic Changes in Livers of Male S-D Rats Exposed to 2-Nitropropane
via Inhalation for 3 or 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Bile duct proliferation


3 mo
0/10
1/10
6 mo
0/10
4/10
3 mo + 3-mo recovery"1
NA
2/10
Focal accumulation of macrophages


3 mo
1/10
1/10
6 mo
0/10
5/10*
3 mo + 3-mo recovery"1
NA
2/10
2+ necrotic hepatocytes


3 mo
0/10
0/10
6 mo
0/10
2/10
3 mo + 3-mo recovery"1
NA
0/10
Basophilic hepatocytes present


3 mo
1/10
2/10
6 mo
0/10
2/10
3 mo + 3-mo recovery"1
NA
1/10
Loss of glycogen


3 mo
7/10
7/10
6 mo
8/10
10/10
3 mo + 3-mo recovery"1
NA
10/10
Cytoplasmic vacuolation


3 mo
2/10
10/10*
6 mo
7/10
9/10
3 mo + 3-mo recovery"1
NA
10/10
6+ nuclear changes


3 mo
1/10
10/10*
6 mo
0/10
4/10
3 mo + 3-mo recovery"1
NA
1/10
Cytoplasmic inclusions


3 mo
0/10
4/10
6 mo
0/10
5/10*
3 mo + 3-mo recovery"1
NA
2/10
Nuclear inclusions


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Clustered cell necrosis


3 mo
0/10
2/10
6 mo
0/10
4/10
3 mo + 3-mo recovery"1
NA
1/10
Broken cell walls


3 mo
0/10
6/10*
6 mo
0/10
1/10
3 mo + 3-mo recovery"1
NA
1/10
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Table B-32. Microscopic Changes in Livers of Male S-D Rats Exposed to 2-Nitropropane
via Inhalation for 3 or 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb'c
0
608 (127)
Hypertrophic areas and/or nodules
3 mo
6 mo
3 mo + 3-mo recovery"1
NR
0/10
NA
NR
10/10*
6/10*
Hyperplastic areas and/or nodules
3 mo
6 mo
3 mo + 3-mo recovery"1
NR
0/10
NA
NR
5/10*
6/10*
aCoulston et al. (1978).
bValues denote number of animals showing changes/total number of animals examined.
'Findings reported as absent (0) or doubtful (±) by the study authors were counted as negative findings; findings
reported as slight (+), moderate (++), or marked (+++) were counted as positive findings.
dIncidence in recovery group compared with incidence in 6-month control animals for statistical analysis
(conducted for this review).
* Significantly increased from control by 2-tailed Fisher's exact test (p < 0.05) conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; NR = not reported;
S-D = Sprague-Dawley.
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Table B-33. Non-neoplastic Microscopic Changes in Livers of Female S-D Rats Exposed to
2-Nitropropane via Inhalation for 10 or 30 Days (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Loss of glycogen


10 d
4/10
10/10*
30 d
0/10
0/10
Vacuolation


10 d
2/10
1/10
30 d
0/10
0/10
Basophilic hepatocytes present


10 d
0/10
0/10
30 d
0/10
0/10
Single liver cell necrosis


10 d
0/10
0/10
30 d
0/10
0/10
Mitosis


10 d
0/10
0/10
30 d
0/10
0/10
Bile ductile proliferation


10 d
0/10
0/10
30 d
0/10
0/10
Focal macrophages


10 d
1/10
1/10
30 d
0/10
0/10
Broken cell walls


10 d
0/10
0/10
30 d
0/10
0/10
aCoulston et al. (1978).
bValues denote number of animals showing changes/total number of animals examined.
'Findings reported as absent (0) or doubtful (±) by the study authors were counted as negative findings; findings
reported as slight (+), moderate (++), or marked (+++) were counted as positive findings.
* Significantly increased from control by 2-tailed Fisher's exact test (p < 0.05) conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; S-D = Sprague-Dawley.
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Table B-34. Microscopic Changes in Livers of Female S-D Rats Exposed to
2-Nitropropane via Inhalation for 3 or 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3

(HECer in mg/m3)
Parameterb'c
0
608 (127)
Bile duct proliferation


3 mo
0/10
1/10
6 mo
0/10
1/10
3 mo + 3-mo recovery"1
NA
0/10
Focal accumulation of macrophages


3 mo
2/10
1/10
6 mo
1/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
2+ necrotic hepatocytes


3 mo
0/10
0/10
6 mo
1/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Basophilic hepatocytes present


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Loss of glycogen


3 mo
6/10
7/10
6 mo
10/10
3/10
3 mo + 3-mo recovery"1
NA
4/10
Cytoplasmic vacuolation


3 mo
0/10
2/10
6 mo
0/10
5/10*
3 mo + 3-mo recovery"1
NA
1/10
6+ nuclear changes


3 mo
0/10
2/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Cytoplasmic inclusions


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Nuclear inclusions


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Clustered cell necrosis


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
Broken cell walls


3 mo
0/10
0/10
6 mo
0/10
0/10
3 mo + 3-mo recovery"1
NA
0/10
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Table B-34. Microscopic Changes in Livers of Female S-D Rats Exposed to
2-Nitropropane via Inhalation for 3 or 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb'c
0
608 (127)
Hypertrophic areas and/or nodules
3 mo
6 mo
3 mo + 3-mo recovery"1
NR
0/10
NA
NR
0/10
0/10
Hyperplastic areas and/or nodules
3 mo
6 mo
3 mo + 3-mo recovery"1
NR
0/10
NA
NR
0/10
0/10
aCoulston et al. (1978).
bValues denote number of animals showing changes/total number of animals examined.
'Findings reported as absent (0) or doubtful (±) by the study authors were counted as negative findings; findings
reported as slight (+), moderate (++), or marked (+++) were counted as positive findings.
dIncidence in recovery group compared with incidence in 6-month control animals for statistical analysis
(conducted for this review).
* Significantly increased from control by two-tailed Fisher's exact test (p < 0.05) conducted for this review.
ER = extrarespiratory; HEC = human equivalent concentration; NA = not applicable; NR = not reported;
S-D = Sprague-Dawley.
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Table B-35. Body, Liver, and Kidney Weight Data for NZW Male Rabbits Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 Days/Week)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Body weight (g)
1 mo
3 mo
6 mo
2,846 ± 60.9
3,634 ± 197.9
4,142 ± 183.0
2,712 ±72.1 (-5%)
3,537 ± 335.4 (-3%)
3,218 ±758.8 (-22%)
2,738 ± 122 (-4%)
3,560 ±55.1 (-2%)
4,012 ± 158.2 (-3%)
Absolute liver weight (g)
1 mo
3 mo
6 mo
80.4 ±4.59
89.9 ±7.99
81.9 ±7.044
65.3 ±3.49 (-18%)
95.1 ± 8.03 (+6%)
82.26 ± 2.857 (+0.4%)
73 ± 6.65 (-9%)
94.5 ± 5.02 (+5%)
82.13±5.71 (+0.3%)
Relative liver weight (g)
1 mo
3 mo
6 mo
2.8 ±0.14
2.5 ± 0.11
NR
2.4 ±0.1 (-14%)
2.6 ± 0.26 (+4%)
NR
2.7 + 0.14 (-4%)
2.7 + 0.16 (+8%)
NR
Absolute kidney weight (g)
1 mo
3 mo
6 mo
17.8 ±0.9
21 ± 1.1
26.77 ±3.067
18.4 ± 1.01 (+3%)
22 ± 1.0 (+5%)
22.48 ± 1.454 (-16%)
18.2+1.39 (+2%)
21 + 1.5 (0%)
21.68 + 0.995 (-19%)
Relative kidney weight (g)
1 mo
3 mo
6 mo
0.6 ±0.03
1±0
NR
0.7 ± 0.04 (+17%)
1 ± 0.1 (0%)
NR
0.7 + 0.04 (+17%)
1 + 0 (0%)
NR
aUlrich et at (1977).
bData are mean ± SEM; n = 5/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Mann-Whitney U test (U < 2; p < 0.05), as reported by the study authors.
ER = extrarespiratory; HEC = human equivalent concentration; NR = not reported; NZW = New Zealand White;
SEM = standard error of the mean.
Ill
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Table B-36. Clinical Chemistry Data for Male NZW Rabbits Exposed to 2-Nitropropane
via Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb'c
0
98 (20)
754 (157)
Serum ALT (U/L)
1 mo
3 mo
6 mo
30 ±4
42 ±3.7
35 ±5.3
24 ± 3.4 (-20%)
43 ± 3.3 (+2%)
27 ± 3.2 (-23%)
52 ± 2.2* (+73%)
39 ± 4.5 (-7%)
31 ±6.7 (-11%)
Serum OCT (activity/mL)
1 mo
3 mo
6 mo
470 ± 114.7
840 ± 277.2
2,940 ± 1,591.5
470 ± 139.3 (0%)
2,400 ± 769.7 (+186%)
1,250 ± 148.3 (-58%)
2,020 ± 260.6* (+330%)
2,230 ± 462.0 (+166%)
2,110 ±585.7 (-28%)
Serum T4 (|ig/dL)
1 mo
3 mo
6 mo
3.4 ±0.45
2.2 ±0.38
2.1 ±0.28
3.3 ±0.23 (-3%)
1.3 ±0.38 (-41%)
1.7 ±0.36 (-19%)
3.6 ±0.17 (+6%)
2.9 ± 0.2 (+32%)
3.8 ±0.08* (+81%)
aUlrich et at (1977).
bData are mean ± SEM; n = 5/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Mann-Whitney U test (U < 2;p< 0.05), as reported by the study authors.
ALT = alanine aminotransferase (glutamic-pyruvic transaminase); ER = extrarespiratory; HEC = human equivalent
concentration; NZW = New Zealand White; OCT = ornithine carbamyl transferase; SEM = standard error of the
mean; T4 = thyroxine.
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Table B-37. Lung Weight and Edema Data for Male NZW Rabbits Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 Days/Week)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECpu in mg/m3)d
0
98 (16)
754 (130)
Absolute lung weight (g)
1 mo
3 mo
6 mo
20.1 ± 1.26
25.1 ±3.08
31.91 ±3.506
16.5 ± 0.90 (-18%)
23.9 ± 1.82 (-5%)
20.91 ± 1.270* (-35%)
23.2 ±2.26 (+15%)
23.0 ±0.69 (-8%)
27.18 ±3.278 (-15%)
Relative lung weight (g)
1 mo
3 mo
6 mo
0.7 ±0.05
0.7 ±0.07
NR
0.6 ± 0.03 (-14%)
0.7 ±0.12 (0%)
NR
0.8 ± 0.05 (+14%)
0.6 ± 0.02 (-14%)
NR
Lung edema (% water)
1 mo
3 mo
6 mo
80.1 ±0.22
83.6 ±2.40
80.1 ±0.09
79.4 ± 0.77 (-0.9%)
79.5 ± 2.99 (-5%)
79.8 ± 0.25 (-0.4%)
81.0 ± 1.24 (+1%)
79.9 ± 0.33 (-4%)
80.5 ± 0.68 (+0.5%)
aUlrich et at (1977).
bData are mean ± SEM; n = 5/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
dHECpu values calculated using 6-month TWA body weight values based on graphically reported body weight data
extracted using Grab It! software.
* Significantly different from control by Mann-Whitney U test (U < 2; p < 0.05), as reported by the study authors.
HEC = human equivalent concentration; NR = not reported; NZW = New Zealand White; PU = pulmonary;
SEM = standard error of the mean; TWA = time-weighted average.
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Table B-38. Thyroid and Brain Weight Data for Male NZW Rabbits Exposed to
2-Nitropropane via Inhalation for up to 6 Months (7 Hours/Day, 5 Days/Week)3
Parameterb'c
Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
0
98 (20)
754 (157)
Absolute thyroid weight (g)
1 mo
3 mo
6 mo
0.217 ±0.0729
0.501 ±0.0556
0.235 ±0.033
0.117 ±0.0253 (-46%)
0.591 ±0.0351 (+18%)
0.316 ±0.0188 (+35%)
0.249 ± 0.0508 (+15%)
0.404 ±0.0219 (-19%)
0.3 ± 0.0337 (+28%)
Relative thyroid weight (g)
1 mo
3 mo
6 mo
0.008 ± 0.0027
0.014 ±0.0014
NR
0.004 ±0.001 (-50%)
0.017 ±0.017 (+21%)
NR
0.010 ±0.0021(+25%)
0.011 ±0.0005 (-21%)
NR
Absolute brain weight (g)
1 mo
3 mo
6 mo
8.3 ±0.34
10.4 ±0.25
9.6 ±0.22
10.1 ±0.22* (+22%)
8.7 ± 0.59 (-16%)
9.87 ± 0.678 (+3%)
9.1 ±0.33 (+10%)
10.2 ±0.19 (-2%)
10.04 ±0.415 (+5%)
Relative brain weight (g)
1 mo
3 mo
6 mo
0.3 ±0.01
0.3 ±0.02
NR
0.4 ±0.01* (+33%)
0.2 ± 0.03 (-33%)
NR
0.3 ± 0.02 (0%)
0.3 ±0.01 (0%)
NR
aUlrich et at (1977).
bData are mean ± SEM; n = 4-5/group.
°Value in parentheses is % change relative to control = ([treatment mean - control mean] + control mean) x 100.
* Significantly different from control by Mann-Whitney U test (U < 2; p < 0.05), as reported by the study authors.
ER = extrarespiratory; HEC = human equivalent concentration; NR = not reported; NZW = New Zealand White;
SEM = standard error of the mean.
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Table B-39. Pulmonary Lesions in Male NZW Rabbits Exposed to 2-Nitropropane via
Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3


(HECpu in mg/m3)c

Parameterb
0
98 (16)d
754 (130)
Interstitial pneumonitis



1 mo
1/5 (20%)
1/4 (25%)
2/5 (40%)
3 mo
1/5 (20%)
2/4 (50%)
2/5 (40%)
6 mo
4/5 (80%)
3/4 (75%)
3/5 (60%)
Alveolar necrosis



1 mo
0/5 (0%)
0/4 (0%)
3/5 (60%)
3 mo
1/5 (20%)
0/4 (0%)
1/5 (20%)
6 mo
1/5 (20%)
0/4 (0%)
1/5 (20%)
Focal hemorrhage



1 mo
0/5 (0%)
0/4 (0%)
3/5 (60%)
3 mo
1/5 (20%)
0/4 (0%)
1/5 (20%)
6 mo
1/5 (20%)
1/4 (25%)
2/5 (40%)
Pulmonary edema



1 mo
0/5 (0%)
0/4 (0%)
3/5 (60%)
3 mo
1/5 (20%)
0/4 (0%)
0/5 (0%)
6 mo
1/5 (20%)
0/4 (0%)
0/5 (0%)
Interstitial edema



6 mo
0/5 (0%)
0/4 (0%)
2/5 (40%)
aUlrich et at (1977).
bValues denote number of animals showing changes/total number of animals examined (% incidence).
°HECpu values calculated using 6-month TWA body weight values based on graphically reported body weight data
extracted using Grab It! software.
dData are only legible for 4 in this group; it appears that data for the 5th animal is cut off in the study report.
HEC = human equivalent concentration; NZW = New Zealand White; PU = pulmonary; TWA = time-weighted
average.
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Table B-40. Hepatic Lesions in Male NZW Rabbits Exposed to 2-Nitropropane via
Inhalation for up to 6 Months (7 Hours/Day, 5 DaysAVeek)3

Dose Group, Analytical Concentration in mg/m3
(HECer in mg/m3)
Parameterb
0
98 (20)c
754 (157)
Liver pericholangitis
1 mo
3 mo
6 mo
1/5 (20%)
2/5 (40%)
5/5 (100%)
2/4 (50%)
3/4 (75%)
3/4 (75%)
3/5 (60%)
3/5 (60%)
5/5 (100%)
Hepatocyte vacuolation
3 mo
6 mo
0/5 (0%)
0/5 (0%)
1/4 (25%)
0/4 (0%)
0/5 (0%)
1/5 (20%)
Focal mononuclear cell infiltration
3 mo
6 mo
0/5 (0%)
0/5 (0%)
1/4 (25%)
0/4 (0%)
1/5 (20%)
0/5 (0%)
aUlrich et at (1977).
bValues denote number of animals showing changes total number of animals examined (% incidence).
Data are only legible for 4 in this group; it appears that data for the 5th animal is cut off in the study report.
ER = extrarespiratory; HEC = human equivalent concentration; NZW = New Zealand White.
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APPENDIX C. BENCHMARK DOSE MODELING RESULTS
MODELING PROCEDURE
Dichotomous Noncancer Data
The benchmark dose (BMD) modeling of dichotomous data is conducted with the
U. S. EPA's Benchmark Dose Software (BMDS, Version 2.6 was used for this document). For
these data, the Gamma, Logistic, Log-Logistic, Log-Probit, Multistage, Probit, and Weibull
dichotomous models available within the software are fit using a benchmark response (BMR) of
10% extra risk. Alternative BMRs may also be used where appropriate, as outlined in the
Benchmark Dose Technical Guidance (U.S. EPA. 2012b). In general, the BMR should be near
the low end of the observable range of increased risk in the study. BMRs that are too low can
result in widely disparate benchmark dose lower confidence limit (BMDL) estimates from
different models (high model dependence). Adequacy of model fit is judged based on the
X2 goodness-of-fitp-value (p > 0.1), magnitude of scaled residuals (absolute value < 2.0), and
visual inspection of the model fit. Among all models providing adequate fit, the BMDL from the
model with the lowest Akaike's information criterion (AIC) is selected as a potential point of
departure (POD), if the BMDLs are sufficiently close (threefold), model dependence is indicated, and the model with the lowest
reliable BMDL is selected.
Continuous Noncancer Data
BMD modeling of continuous data is conducted with U.S. EPA's BMDS (Version 2.6) as
well. All continuous models available within the software (Exponential, Hill, Linear,
Polynomial, and Power models) are fit using a standard reporting BMR of 1 standard deviation
(SD) relative risk. Alternate BMRs may also be used (e.g., BMR = 10% relative derivation [RD]
for body weight based on a biologically significant weight loss of 10%), as outlined in the
Benchmark Dose Technical Guidance (U.S. EPA. 2012b). In general, the BMR should be near
the low end of the observable range of increased risk in the study. BMRs that are too low can
result in widely disparate BMDL estimates from different models (high model dependence). An
adequate fit is judged based on the %2 goodness-of-fit p-value (p > 0.1), magnitude of the scaled
residuals near the BMR (absolute value < 2.0), and visual inspection of the model fit. In addition
to these three criteria forjudging adequacy of model fit, a determination is made as to whether
the variance across dose groups is homogeneous. If a homogeneous variance model is deemed
appropriate based on the statistical test provided by BMDS (i.e., Test 2), the final BMD results
are estimated from a homogeneous variance model. If the test for homogeneity of variance is
rejected (p < 0.1), the model is run again while modeling the variance as a power function of the
mean to account for this nonhomogeneous variance. If this nonhomogeneous variance model
does not adequately fit the data (i.e., Test 3;p<0 .1), the data set is considered unsuitable for
BMD modeling. Among all models providing adequate fit, the lowest BMDL is selected if the
BMDL estimates from different models vary >threefold (indicating model dependence);
otherwise, the BMDL from the model with the lowest AIC is selected as a potential POD from
which to derive the reference value.
Cancer Data
The model-fitting procedure for dichotomous cancer incidence is as follows. The
Multistage cancer model in the U.S. EPA's BMDS (Version 2.6) is fit to the incidence data using
the extra risk option. The Multistage cancer model is run for all polynomial degrees up to n - 1
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(where n is the number of dose groups, including control). An adequate model fit is judged by
three criteria: (1) goodness-of-fit/>-value (p < 0.1), (2) visual inspection of the dose-response
curve, and (3) scaled residual at the data point (except the control) closest to the predefined BMR
(absolute value < 2.0). Among the models providing adequate fit to the data, the BMDL for the
model with the lowest AIC is selected as the POD, if the BMDLs are sufficiently close
(threefold), model dependence is
indicated, and the model with the lowest reliable BMDL is selected. In accordance with U.S.
EPA (2012b) and U.S. EPA (2005a) guidance, BMD and BMDL values associated with an extra
risk of 10% are calculated, which should be within the observable range of increased risk in a
cancer bioassay. Modeling is performed for each individual tumor type with at least a
statistically significant trend. Where applicable, the MS Combo model is used to evaluate the
combined cancer risk of multiple tumor types. MS Combo is run using the incidence data for the
individual tumor types and the polydegrees identified in the model runs for the individual tumor
types.
Dropping the High Dose
In the absence of a mechanistic understanding of the biological response to a toxic agent,
data from exposures much higher than the study lowest-observed-adverse-effect level (LOAEL)
do not provide reliable information regarding the shape of the response at low doses. Such
exposures, however, can have a strong effect on the shape of the fitted model in the low-dose
region of the dose-response curve. Thus, if lack of fit is due to characteristics of the
dose-response data for high doses, then the Benchmark Dose Technical Guidance document
allows for data to be adjusted by eliminating the high-dose group (U.S. EPA. 2012b). Because
the focus of BMD analysis is on the low-dose regions of the response curve, elimination of the
high-dose group may be reasonable for certain data sets.
BMD MODELING TO IDENTIFY POTENTIAL POINTS OF DEPARTURE FOR THE
DERIVATION OF A SCREENING SUBSCHRONIC PROVISIONAL REFERENCE
DOSE
The data sets for relative liver weights and hepatocyte hypertrophy in male rats exposed
to 2-nitropropane via gavage for 28 days (Kawakami et al. 2015) were selected to determine
potential PODs for the screening subchronic provisional reference dose (p-RfD), using BMD
analysis. Table A-l in Appendix A shows the data that were modeled. Summaries of modeling
approaches and results follow (see Tables C-3 and C-4 and Figures C-l and C-2 for each data
set).
Increased Relative Liver Weight in Male Rats Exposed to 2-Nitropropane via Gavage for
28 Days (Kawakami et al.. 2015)
The procedure outlined above for continuous data was applied to the data for increased
relative liver weight in male S-D rats exposed to 2-nitropropane via gavage for 28 days
(see Table A-l). Table C-l summarizes the BMD modeling results. The constant variance
model provided an adequate fit to the variance data. With the constant variance model applied,
all models except Exponential 5 and Hill models provided adequate fit to the data. BMDL
values for models providing adequate fit were sufficiently close (
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Table C-l. BMD Modeling Results for Increased Relative Liver Weight in Male Rats
Exposed to 2-Nitropropane via Gavage for 28 Days3
Model
Variance
/>-Valucb
Means
/>-Valucb
Scaled Residual at
Dose Nearest BMD
AIC
BMDio
(HED, mg/kg-d)
BMDLio
(HED, mg/kg-d)
Exponential 2°
0.2603
0.6681
-0.1759
-45.1230
4.4
3.6
Exponential 3°
0.2603
0.6681
-0.1759
-45.1230
4.4
3.6
Exponential 4°
0.2603
0.7996
-0.1959
-43.8652
3.3
1.7
Exponential 5°
0.2603
NA
-1.32 x 10-7
-41.9297
3.5
1.7
Hillc
0.2603
NA
-1.30 x 10-6
-41.9297
3.5
1.6
Linear"1' *
0.2603
0.7796
-0.162
-45.4317
4.1
3.3
Polynomial
(2-degree)d
0.2603
0.7796
-0.162
-45.4317
4.1
3.3
Polynomial
(3 -degree )d
0.2603
0.7796
-0.162
-45.4317
4.1
3.3
Power0
0.2603
0.7796
-0.162
-45.4317
4.1
3.3
aKawakami et at (2015).
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
Tower restricted to >1.
Coefficients restricted to be positive.
* Selected model.
AIC = Akaike's information criterion; BMD = maximum likelihood estimate of the dose associated with the
selected BMR; BMDL = 95% lower confidence limit on the BMD (subscripts denote benchmark response:
i.e., RD10 = exposure concentration associated with a 10% relative deviation change in parameter);
BMR = benchmark response; HED = human equivalent dose; NA = not applicable (computation failed);
RD = relative deviation.
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Linear Model, with BMR of 0.1 Rei. Dev. for the BMD and 0.95 Lower Confidence Limit for the BMDL
t—|—i—i—i—i—i—i—i—i—i—|—i—i—i—i—i—i—i—i—i—|—i—i—i—i—i—i—i—i—i—|—i—i—i—i—i—i—i—i—i—|—i—i—i—i—i—i—i—i—i—r
Linear
dose
10:00 06/07 2018
Figure C-l. Fit of Linear Model to Data for Increased Relative Liver Weight in Male Rats
Exposed to 2-Nitropropane via Gavage for 28 Days (Kawakami et al., 2015)
(BMR = RD 10)
Text Output for Figure C-l:
Polynomial Model. (Version: 2.20; Date: 10/22/2014)
Input Data File:
C:/BMDS2 601/Data/DataFiles/lin_2NP_kawakami_relLW_Lin-ConstantVariance-BMR10. (d)
Gnuplot Plotting File:
C:/BMDS2 601/Data/DataFiles/lin_2NP_kawakami_relLW_Lin-ConstantVariance-BMR10.pit
Thu Jun 07 10:00:13 2018
BMDS Model Run
The form of the response function is:
Y[dose] = beta_0 + beta_l*dose + beta_2*dose/s2 + ...
Dependent variable = Mean
Independent variable = Dose
rho is set to 0
Signs of the polynomial coefficients are not restricted
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A constant variance model is fit
Total number of dose groups = 4
Total number of records with missing values = 0
Maximum number of iterations = 5 00
Relative Function Convergence has been set to: le-008
Parameter Convergence has been set to: le-008
Default Initial Parameter Values
alpha =	0.034275
rho =	0 Specified
beta_0 =	2.92139
beta_l = 0.0707191
Asymptotic Correlation Matrix of Parameter Estimates
the user,
alpha
beta_0
beta 1
( *** The model parameter(s) -rho
have been estimated at a boundary point, or have been specified by
and do not appear in the correlation matrix )
alpha
1
-le-007
1.4e-007
beta_0
-le-007
1
-0.71
beta_l
1.4e-007
-0.71
1
Interval
Variable
Limit
alpha
0.0455346
beta_0
3.02633
beta_l
0.0895653
Estimate
0.0281113
2.92139
0.0707191
Parameter Estimates
Std. Err.
0.00888958
0.0535396
0.00961562
95.0% Wald Confidence
Lower Conf. Limit Upper Conf.
0.0106881
2.81646
0.0518728
Table of Data and Estimated Values of Interest
Dose
Obs Mean
Est Mean
Obs Std Dev Est Std Dev Scaled Res.
0	5
1	5
5	5
9.9	5
2.91
2.98
3.32
3.6
2.92
2.99
3.27
3. 62
0.09
0.23
0.2
0.19
0.1*
0.1*
0.1*
0.1*
Model Descriptions for likelihoods calculated
Model A1:	Yij = Mu(i) + e(ij)
Var(e(ij)) = Sigma^2
Model A2:	Yij = Mu(i) + e(ij)
Var(e(ij)) = Sigma(i)/S2
Model A3:	Yij = Mu(i) + e(ij)
Var(e(ij)) = Sigma^2
Model A3 uses any fixed variance parameters that
were specified by the user
-0.152
-0.162
0.6
-0.287
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Model R:	Yi = Mu + e(i)
Var(e(i)) = Sigma^2
Likelihoods of Interest
Model
Log(likelihood)
# Param's
AIC
A1
25.964826
5
-41.929652
A2
27.970389
8
-39.940778
A3
25.964826
5
-41.929652
fitted
25.715827
3
-45.431654
R
12.620311
2
-21.240623
Explanation of Tests
Test 1
Test 2
Test 3
Test 4
(Note:
: Do responses and/or variances differ among Dose levels?
(A2 vs. R)
: Are Variances Homogeneous? (A1 vs A2)
: Are variances adeguately modeled? (A2 vs. A3)
: Does the Model for the Mean Fit? (A3 vs. fitted)
When rho=0 the results of Test 3 and Test 2 will be the same.)
Tests of Interest
Test
-2*log(Likelihood Ratio) Test df
p-value
Test
Test
Test
Test
30.7002
4.01113
4.01113
0.497998
<.0001
0.2603
0.2603
0.7796
The p-value for Test 1 is less than .05. There appears to be a
difference between response and/or variances among the dose levels
It seems appropriate to model the data
The p-value for Test 2 is greater than .1. A homogeneous variance
model appears to be appropriate here
The p-value for Test 3 is greater than .1. The modeled variance appears
to be appropriate here
The p-value for Test 4 is greater than .1. The model chosen seems
to adeguately describe the data
Benchmark Dose Computation
Specified effect =	0.1
Risk Type	=	Relative deviation
Confidence level =	0.95
BMD =	4.13098
BMDL =	3.27604
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Increased Incidence of Hepatocyte Hypertrophy in Male Rats Exposed to 2-Nitro pro pane
via Gavage for 28 Days CKawakami et at, 2015)
The procedure outlined above for dichotomous data was applied to the data for increased
incidence of hepatocyte hypertrophy in male S-D rats exposed to 2-nitropropane via gavage for
28 days (see Table A-l). Table C-2 summarizes the BMD modeling results. All models
provided adequate fit to the data. BMDLs for models providing adequate fit were not
sufficiently close (>threefold), so the model with the lowest BMDL was selected (1-degree
Multistage). Figure C-2 shows the fit of the 1-degree Multistage model to the data. Based on
HEDs, the BMDio and BMDLio for increased hepatocellular hypertrophy in male rats were 0.64
and 0.34 mg/kg-day.
Table C-2. BMD Modeling Results for Increased Incidence of Hepatocyte Hypertrophy in
Male Rats Exposed to 2-Nitropropane via Gavage for 28 Days3
Model
DF
x2
x2
Goodness-of-Fit
/>-Valucb
Scaled Residual
at Dose Nearest
BMD
AIC
BMDio
(HED, mg/kg-d)
BMDLio
(HED, mg/kg-d)
Gamma0
3
0.01
0.9998
-0.019
8.74717
3.85
1.17
Logistic
2
0
1
0
10.7301
4.61
1.70
LogLogisticd
3
0
1
0
8.73019
4.53
1.48
LogProbitd
2
0
1
0
10.7301
4.44
1.42
Multistage
(1-degree)' *
3
2.64
0.4511
-0.944
13.0787
0.64
0.34
Multistage
(2-degree)e
3
0.71
0.8706
-0.38
9.88838
1.92
0.62
Multistage
(3-degree)6
3
0.11
0.9907
-0.152
8.92047
2.84
0.71
Probit
2
0
1
0
10.7301
4.25
1.51
Weibull0
2
0
1
0
10.7301
4.16
1.08
aKawakami et at (2015).
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
Tower restricted to >1.
dSlope restricted to >1.
"Betas restricted to >0.
* Selected model.
AIC = Akaike's information criterion; BMD = maximum likelihood estimate of the dose associated with the
selected BMR; BMDL = 95% lower confidence limit on the BMD (subscripts denote benchmark response:
i.e., 10 = dose associated with 10% extra risk); BMR = benchmark response; DF = degree(s) of freedom;
HED = human equivalent dose.
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Multistage Model, with BMR of 10% Extra Risk for the BMD and 0.95 Lower Confidence Limit for the BMDL
1
0.8
~o
& 0.6
O
0)
<
c
o
o
ro
lH 0.4
0.2
0
0	2	4	6	8	10
dose
09:32 06/07 2018
Figure C-2. Fit of 1-Degree Multistage Model to Data for Hepatocyte Hypertrophy in Male
Rats Exposed to 2-Nitropropane via Gavage for 28 Days (Kawakami et al., 2015)
(BMR = 10% Extra Risk)
Text Output for Figure C-2:
Multistage Model. (Version: 3.4; Date: 05/02/2014)
Input Data File:
C:/BMDS2601/Data/DataFiles/mst_2NP_kawakami_hypertrophy_Mstl-BMR10-Restrict.(d)
Gnuplot Plotting File:
C:/BMDS2 601/Data/DataFiles/mst_2NP_kawakami_hypertrophy_Mstl-BMR10-Restrict.pit
Thu Jun 07 09:32:45 2018
BMDS Model Run
The form of the probability function is:
P[response] = background + (1-background)*[1-EXP(
-betal*doseAl) ]
The parameter betas are restricted to be positive
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Dependent variable = Effect
Independent variable = Dose
Total number of observations = 4
Total number of records with missing values = 0
Total number of parameters in model = 2
Total number of specified parameters = 0
Degree of polynomial = 1
Maximum number of iterations = 5 00
Relative Function Convergence has been set to: le-008
Parameter Convergence has been set to: le-008
Default Initial Parameter Values
Background =	0
Beta(1) = 9.74386e+018
Asymptotic Correlation Matrix of Parameter Estimates
the user,
Beta(1)
( *** The model parameter(s) -Background
have been estimated at a boundary point, or have been specified by
and do not appear in the correlation matrix )
Beta(1)
1
Parameter Estimates
Interval
Variable
Limit
Background
Beta(1)
0.296319
Estimate
0
0.164132
Std. Err.
NA
0.0674432
NA - Indicates that this parameter has hit a bound
implied by some ineguality constraint and thus
has no standard error.
95.0% Wald Confidence
Lower Conf. Limit Upper Conf.
0.0319463
Model
Full model
Fitted model
Reduced model
Analysis of Deviance Table
Log(likelihood)	# Param's	Deviance Test d.f.	P-value
-3.36506	4
-5.53935	1	4.34858 3	0.2262
-12.9489	1	19.1677 3	0.0002524
AIC:	13.0787
Goodness of Fit
Dose	Est._Prob. Expected Observed	Size
Scaled
Residual
0.0000
1.0000
5.0000
9.9000
0.0000
0.1514
0.5599
0.8031
Chi^2 = 2.64	d.f. = 3
Benchmark Dose Computation
0.000	0.000	5.000
0.757	0.000	5.000
2.799	2.000	5.000
4.015	5.000	5.000
P-value = 0.4511
0. 000
-0.944
-0.720
1.107
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Specified effect =	0.1
Risk Type =	Extra risk
Confidence level =	0.95
BMD =	0.641924
BMDL =	0.341573
BMDU =	1.33967
Taken together, (0.341573, 1.33967) is a 90	% two-sided confidence
interval for the BMD
BMD MODELING TO IDENTIFY POTENTIAL POINTS OF DEPARTURE FOR THE
DERIVATION OF A SUBCHRONIC PROVISIONAL REFERENCE
CONCENTRATION
The data sets for increased absolute and relative liver weights for 3 months (Lewis et al..
1979; Ulrich et al.. 1977) were modeled to determine potential PODs for the subchronic
provisional reference concentration (p-RfC), using BMD analysis. Table 7 in the "Derivation of
Inhalation Reference Concentrations" section of the main document shows the data that were
modeled. Summaries of modeling approaches and results (see Tables C-3 and C-4 and
Figures C-3 and C-4) for each data set follow.
Increased Absolute Liver Weight in Male Rats Exposed to 2-Nitropropane via Inhalation
for 3 Months (Lewis et al.. 1979: Ulrich et al.. 1977)
The procedure outlined above for continuous data was applied to the data for increased
absolute liver weight in male Sprague-Dawley (S-D) rats exposed to 2-nitropropane via
inhalation for 3 months (see Table 8). Table C-3 summarizes the BMD modeling results. The
constant variance model did not provide an adequate fit to the variance data, but the nonconstant
variance model did. With the nonconstant variance model applied, all models except the
Exponential 4 model provided adequate fit to the data (Exponential 5 and Hill models did not run
because the data included too few exposure groups for those models). Benchmark concentration
lower confidence limit (BMCL) values for models providing adequate fit were sufficiently close
(
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Table C-3. BMD Modeling Results for Increased Absolute Liver Weight in Male S-D Rats
Exposed to 2-Nitropropane via Inhalation for 3 Months3
Model
Variance
/>-Valucb
Means
/>-Valucb
Scaled Residual at
Dose Nearest BMC
AIC
BMC 10
(HEC, mg/m3)
BMCLio
(HEC, mg/m3)
Constant variance
Lineal
0.07045
0.4396
0.576
68.2915
40.68
30.63
Nonconstant variance
Exponential 2d
0.8709
0.2521
0.853
65.7268
45.38
34.90
Exponential 3 d
0.8709
0.2521
0.853
65.7268
45.38
34.90
Exponential 4d
0.8709
NA
0.039
66.4149
20.17
9.15
Linear0' *
0.8709
0.3195
0.761
65.4060
39.39
28.70
Polynomial
(2-degree)°
0.8709
0.3195
0.761
65.4060
39.39
28.70
Power"1
0.8709
0.3195
0.761
65.4060
39.39
28.70
aLewis et at (1979): Ulrich et at (1977).
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
Coefficients restricted to be positive.
dPower restricted to >1.
* Selected model.
AIC = Akaike's information criterion; BMC = maximum likelihood estimate of the exposure concentration
associated with the selected BMR; BMCL = 95% lower confidence limit on the BMC (subscripts denote
benchmark response: i.e., RD10 = exposure concentration associated with a 10% relative deviation change in
parameter); BMD = benchmark dose; BMR = benchmark response; HEC = human equivalent concentration;
NA = not applicable (computation failed); S-D = Sprague-Dawley.
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Linear Model, with BMR of 0.1 Rei. Dev. for the BMD and 0.95 Lower Confidence Limit for the BMDL
dose
11:29 02/20 2018
Figure C-3. Fit of Linear Model to Data for Increased Absolute Liver Weight in Male S-D
Rats Exposed to 2-Nitropropane via Inhalation for 3 Months (Lewis et al., 1979; Ulrich et
al.. 1977) (BMR = RD 10)
Text Output for Figure C-3:
Polynomial Model. (Version: 2.20; Date: 10/22/2014)
Input Data File:
C:/BMDS2601/Data/DataFiles/lin_2NP_urlich_absLW_Lin-ModelVariance-BMR10.(d)
Gnuplot Plotting File:
C:/BMDS2 601/Data/DataFiles/lin_2NP_urlich_absLW_Lin-ModelVariance-BMR10.pit
Tue Feb 20 11:29:43 2018
BMDS Model Run
The form of the response function is:
Y[dose] = beta_0 + beta_l*dose + beta_2*dose/s2 + ...
Dependent variable = Mean
Independent variable = Dose
Signs of the polynomial coefficients are not restricted
The variance is to be modeled as Var(i) = exp(lalpha + log(mean(i)) * rho)
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Total number of dose groups = 3
Total number of records with missing values = 0
Maximum number of iterations = 5 00
Relative Function Convergence has been set to: le-008
Parameter Convergence has been set to: le-008
Default Initial Parameter Values
lalpha =	1.23659
rho =	0
beta_0 =	12.0826
beta_l = 0.0296727
Asymptotic Correlation Matrix of Parameter Estimates
lalpha
rho
beta_0
beta 1
lalpha
1
-1
0.053
-0.1
rho
-1
1
-0.053
0.1
beta_0
0.053
-0.053
1
-0.48
beta_l
-0.1
0.1
-0.48
1
Parameter Estimates
95.0% Wald Confidence Interval
Variable
lalpha
rho
beta_0
beta 1
Estimate
-9.0987
3. 86149
12.0463
0.0305787
Std. Err.
4.78625
1.83111
0.323595
0.00584009
Lower Conf. Limit
-18.4796
0.272584
11.412
0.0191324
Upper Conf. Limit
0.282183
7.4504
12 . 6805
0.0420251
Table of Data and Estimated Values of Interest
Dose	N Obs Mean	Est Mean Obs Std Dev Est Std Dev
Scaled Res.
0 10	11.8	12	1.3	1.29	-0.603
20 10	13	12.7	1.5	1.42	0.761
157	9	16.7	16.8	2.6	2.47	-0.179
Model Descriptions for likelihoods calculated
Model A1:	Yij = Mu(i) + e(ij)
Var(e(ij)) = Sigma^2
Model A2:	Yij = Mu(i) + e(ij)
Var(e(ij)) = Sigma(i)^2
Model A3:	Yij = Mu(i) + e(ij)
Var(e(ij)) = exp(lalpha + rho*ln(Mu(i)))
Model A3 uses any fixed variance parameters that
were specified by the user
Model R:	Yi = Mu + e(i)
Var(e(i)) = Sigma^2
Likelihoods of Interest
Model	Log(likelihood)	# Param's	AIC
A1 -30.847150	4	69.694299
A2 -28.194268	6	68.388536
A3 -28.207463	5	66.414927
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fitted	-28.702983	4	65.405966
R	-43.310851	2	90.621702
Explanation of Tests
Test 1: Do responses and/or variances differ among Dose levels?
(A2 vs. R)
Test 2
Test 3
Test 4
Are Variances Homogeneous? (A1 vs A2)
Are variances adeguately modeled? (A2 vs. A3)
Does the Model for the Mean Fit? (A3 vs. fitted)
(Note: When rho=0 the results of Test 3 and Test 2 will be the same.)
Tests of Interest
Test -2*log(Likelihood Ratio) Test df	p-value
Test 1	30.2332	4	<.0001
Test 2	5.30576	2	0.07045
Test 3	0.026391	1	0.8709
Test 4	0.991039	1	0.3195
The p-value for Test 1 is less than .05. There appears to be a
difference between response and/or variances among the dose levels
It seems appropriate to model the data
The p-value for Test 2 is less than .1. A non-homogeneous variance
model appears to be appropriate
The p-value for Test 3 is greater than .1. The modeled variance appears
to be appropriate here
The p-value for Test 4 is greater than .1. The model chosen seems
to adeguately describe the data
Benchmark Dose Computation
Specified effect =	0.1
Risk Type	=	Relative deviation
Confidence level =	0.95
BMD =	39.3943
BMDL =	28.6968
Increased Relative Liver Weight in Male Rats Exposed to 2-Nitropropane via Inhalation
for 3 Months (Lewis et at, 1979; Ulricfa et at, 1977)
The procedure outlined above for continuous data was applied to the data for increased
relative liver weight in male S-D rats exposed to 2-nitropropane via inhalation for 3 months
(see Table 8). Table C-4 summarizes the BMD modeling results. The constant variance model
did not provide an adequate fit to the variance data, but the nonconstant variance model did.
With the nonconstant variance model applied, only the Linear and Exponential 2 models
provided adequate fit to the data. BMC values were sufficiently close (
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Table C-4. BMD Modeling Results for Relative Liver Weight in Male S-D Rats Exposed to
2-Nitropropane via Inhalation for 3 Months3
Model
Variance
/>-Valucb
Means
/>-Valucb
Scaled Residual at
Dose Nearest BMC
AIC
BMC 10
(HEC, mg/m3)
BMCLio
(HEC, mg/m3)
Constant variance
Lineal
<0.0001
0.5337
-0.442
-26.720
25.93
21.46
Nonconstant variance
Exponential 2d' *
0.4482
0.4473
-0.666
-49.115
32.94
28.06
Exponential 3 d
0.4482
NA
-0.121
-47.693
40.89
28.56
Exponential 4d
0.4482
NA
-1.051
-45.965
28.00
22.79
Lineal
0.4482
0.1887
-1.050
-47.965
28.01
22.79
Polynomial
(2-degree)°
0.4482
NA
-0.121
-47.693
42.18
24.66
Power"1
0.4482
NA
-0.121
-47.693
39.38
24.66
aLewis et at (1979): Ulrich et at (1977).
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
Coefficients restricted to be positive.
dPower restricted to >1.
* Selected model.
AIC = Akaike's information criterion; BMC = maximum likelihood estimate of the exposure concentration
associated with the selected BMR; BMCL = 95% lower confidence limit on the BMC (subscripts denote
benchmark response: i.e., RD10 = exposure concentration associated with a 10% relative deviation change in
parameter); BMD = benchmark dose; BMR = benchmark response; HEC = human equivalent concentration;
NA = not applicable (computation failed); S-D = Sprague-Dawley.
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Exponential 2 Model, with BMR of 0.1 Rel. Dev. for the BMD and 0.95 Lower Confidence Limit for the BMDL
dose
11:30 02/20 2018
Figure C-4. Fit of Exponential 2 Model to Data for Increased Relative Liver Weight in
Male S-D Rats Exposed to 2-Nitropropane via Inhalation for 3 Months (Lewis et al., 1979;
Ulrich et al.. 1977) (BMR = RD 10)
Text Output for Figure C-4:
Exponential Model. (Version: 1.10; Date: 01/12/2015)
Input Data File:
C:/BMDS2601/Data/DataFiles/exp_2NP_urlich_relLW_Exp-ModelVariance-BMR10-Up.(d)
Gnuplot Plotting File:
Tue Feb 20 11:30:42 2018
BMDS Model Run
The form of the response function by Model:
Model 2
Model 3
Model 4
Model 5
Y[dose]	=	a	*	exp(sign * b * dose)
Y[dose]	=	a	*	exp(sign * (b * dose)Ad)
Y[dose]	=	a	*	[c-(c-l) * exp(-b * dose)]
Y[dose]	=	a	*	[c-(c-l) * exp(-(b * dose)Ad)]
Note: Y[dose] is the median response for exposure
sign = +1 for increasing trend in data;
sign = -1 for decreasing trend.
dose;
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Model 2 is nested within Models 3 and 4.
Model 3 is nested within Model 5.
Model 4 is nested within Model 5.
Dependent variable = Mean
Independent variable = Dose
Data are assumed to be distributed: normally
Variance Model: exp(lnalpha +rho *ln(Y[dose]))
The variance is to be modeled as Var(i) = exp(lalpha + log(mean(i)) * rho)
Total number of dose groups = 3
Total number of records with missing values = 0
Maximum number of iterations = 5 00
Relative Function Convergence has been set to: le-008
Parameter Convergence has been set to: le-008
MLE solution provided: Exact
Initial Parameter Values
Variable	Model 2
lnalpha	-10.629
rho	6.75137
a	2.57096
b	0.00296337
c	0 Specified
d	1 Specified
Parameter Estimates
Variable	Model 2 Std. Err.
lnalpha	-10.6902	0.0806022
rho	6.76745	1.65525
a	2.57653	0.032442
b	0.00289355	0.000307666
NC = No Convergence
Table of Stats From Input Data
Dose	N	Obs Mean	Obs Std Dev
0	8	2.6	0.11
20	10	2.7	0.16
157	9	4.1	0.57
Estimated Values of Interest
Dose	Est Mean	Est Std	Scaled Residual
0	2.577	0.1173	0.5656
20	2.73	0.1427	-0.6655
157	4.058	0.5458	0.2299
Other models for which	likelihoods are calculated:
Model A1:	Yij	= Mu(i) + e(ij)
Var(e(ij))	= SigmaA2
Model A2:	Yij	= Mu(i) + e(ij)
Var(e(ij))	= Sigma(i)^2
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Model A3:	Yij
Var(e (ij))
Model R:	Yij
Var(e (ij))
Model
A1
A2
A3
R
2
Mu(i) + e(i j)
exp(lalpha + log(mean(i)) * rho)
Mu + e(i)
SigmaA2
Likelihoods of Interest
Log(likelihood)	DF
16.5538	4
29.13404	6
28.84649	5
-5.987725	2
28.55773	4
AIC
-25.10759
-46.26807
-47.69298
15.97545
-49.11545
Additive constant for all log-likelihoods =	-24.81. This constant added to the
above values gives the log-likelihood including the term that does not
depend on the model parameters.
Explanation of Tests
Does response and/or variances differ among Dose levels? (A2 vs. R)
Are Variances Homogeneous? (A2 vs. Al)
Are variances adeguately modeled? (A2 vs. A3)
Does Model 2 fit the data? (A3 vs. 2)
Tests of Interest
-2*log(Likelihood Ratio)	D. F.	p-value
Test
1:
Test
2 :
Test
3:
Test
4 :
Test
Test 1
Test 2
Test 3
Test 4
70.24
25.16
0.5751
0.5775
<	0.0001
<	0.0001
0. 4482
0.4473
The p-value for Test 1 is less than .05. There appears to be a
difference between response and/or variances among the dose
levels, it seems appropriate to model the data.
The p-value for Test 2 is less than .1. A non-homogeneous
variance model appears to be appropriate.
The p-value for Test 3 is greater than .1.
variance appears to be appropriate here.
The p-value for Test 4 is greater than .1.
to adeguately describe the data.
Benchmark Dose Computations:
Specified Effect = 0.100000
Risk Type = Relative deviation
Confidence Level = 0.950000
BMD =	32.938 9
BMDL =	28.0603
The modeled
Model 2 seems
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BMD MODELING TO IDENTIFY POTENTIAL POINTS OF DEPARTURE FOR THE
DERIVATION OF A PROVISIONAL INHALATION UNIT RISK
Only one data set provided dose-response information for carcinogenicity of
2-nitropropane (Lewis et at.. 1979; Ulricfa et al.. 1977).
Increased Incidence of Hepatocellular Carcinoma in Male S-D Rats Exposed to
2-Nitropropane via Inhalation for 6 Months
The procedure outlined above for dichotomous cancer data was applied to the data for
increased incidence of hepatocellular carcinoma in male rats exposed to 2-nitropropane via
inhalation 7 hours/day, 5 days/week for 6 months (Lewis et al.. 1979; Ulrich et al.. 1977). The
data are shown in Table A-4 in the cancer derivation section in Appendix A. Table C-5
summarizes the BMD modeling results. The Multistage models provided adequate statistical fit
to the data. The BMCL io values were sufficiently close (-Valucb
Scaled Residual at
Dose Nearest BMC
AIC
BMCio
(mg/m3, HEC)
BMCLio
(mg/m3, HEC)
Multistage
cancer
(l-degree)°
2
4.48
0.1067
-1.789
9.95328
7.59
4.09
Multistage
cancer
(2-degree)c' *
2
0.86
0.6516
-0.833
3.66468
25.05
11.39
aLewis et al. (1979); Ulrich et al. (1977).
bValues <0.1 fail to meet conventional goodness-of-fit criteria.
Coefficients restricted to be positive.
* Selected model.
AIC = Akaike's information criterion; BMC = maximum likelihood estimate of the concentration associated with
the selected BMR; BMCL = 95% lower confidence limit on the BMC (subscripts denote BMR:
i.e., 10 = concentration associated with 10% extra risk); BMD = benchmark dose; BMR = benchmark response;
HEC = human equivalent concentration; S-D = Sprague-Dawley.
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Multistage Cancer Model, with BMR of 10% Extra Risk for the BMD and 0.95 Lower Confidence Limit for the BMDL
dose
20:14 02/08 2018
Figure C-5. Fit of the Multistage (2-Degree) Model to Data for Incidence of Hepatocellular
Carcinoma in Male S-D Rats Exposed to 2-Nitropropane via Inhalation for 6 Months
(Lewis et al., 1979; Ulrich et al., 1977)
Text Output for Figure C-5:
Multistage Model. (Version: 3.4; Date: 05/02/2014)
Input Data File:
C:/BMDS2601/Data/DataFiles/msc_2NP_lewis_cancer_Msc2-BMR10.(d)
Gnuplot Plotting File:
C:/BMDS2 601/Data/DataFiles/msc_2NP_lewis_cancer_Msc2-BMR10.pit
Thu Feb 08 20:14:07 2018
BMDS Model Run
The form of the probability function is:
P[response] = background + (1-background)*[1-EXP(
-betal*dose/sl-beta2*dose/s2) ]
The parameter betas are restricted to be positive
Dependent variable = Effect
Independent variable = Dose
Total number of observations = 3
Total number of records with missing values = 0
Total number of parameters in model = 3
Total number of specified parameters = 0
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Degree of polynomial
Maximum number of iterations = 5 00
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) = 4.08933e+015
Asymptotic Correlation Matrix of Parameter Estimates
the user,
Beta (2)
( *** The model parameter(s) -Background -Beta(l)
have been estimated at a boundary point, or have been specified by
and do not appear in the correlation matrix )
Beta(2)
1
Parameter Estimates
Interval
Variable
Limit
Background
Beta(1)
Beta(2)
0.000363693
Estimate
0
0
0. 000167855
Std. Err.
NA
NA
9.99192e-005
95.0% Wald Confidence
Lower Conf. Limit Upper Conf.
-2.79832e-005
NA - Indicates that this parameter has hit a bound
implied by some ineguality constraint and thus
has no standard error.
Model
Full model
Fitted model
Reduced model
Analysis of Deviance Table
Log(likelihood)	# Param's	Deviance Test d.f.	P-value
0	3
-0.832342	1	1.66468 2	0.435
-19.0954	1	38.1909 2	<.0001
AIC:	3.66468
Goodness of Fit
Dose	Est._Prob. Expected Observed	Size
Scaled
Residual
0.0000
20.0000
157.0000
0.0000
0.0649
0.9840
0.000
0.649
9.840
0.000
0.000
10.000
10.000
10.000
10.000
0. 000
-0.833
0. 403
Chi^2 = 0.86
d.f. = 2
P-value = 0.6516
Benchmark Dose Computation
Specified effect =	0.1
Risk Type	=	Extra risk
Confidence level =	0.95
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BMD =	25.0537
BMDL =	11.38 66
BMDU =	38.479
Taken together, (11.3866, 38.479 ) is a 90	% two-sided confidence
interval for the BMD
Cancer Slope Factor = 0.00878225
138	2-Nitr opr opane
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