A rT%H United Stales
Environmental Protection
^Ur inn* I M * Agency
EPA/690/R-17/008
FINAL
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Provisional Peer-Reviewed Toxicity Values for
Lactonitrile
(CASRN 78-97-7)
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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AUTHORS, CONTRIBUTORS, AND REVIEWERS
CHEMICAL MANAGER
Chris Cubbison, PhD
National Center for Environmental Assessment, Cincinnati, OH
DRAFT DOCUMENT PREPARED BY
SRC, Inc.
7502 Round Pond Road
North Syracuse, NY 13212
PRIMARY INTERNAL REVIEWERS
Elizabeth Owens, PhD
National Center for Environmental Assessment, Cincinnati, OH
Jeff Swartout
National Center for 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 content of this PPRTV assessment should be directed to the EPA Office
of Research and Development's National Center for Environmental Assessment, Superfund
Health Risk Technical Support Center (513-569-7300).
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TABLE OF CONTENTS
COMMONLY USED ABBREVIATIONS AND ACRONYMS	iv
BACKGROUND	1
DISCLAIMERS	1
QUESTIONS REGARDING PPRTVs	1
INTRODUCTION	2
REVIEW OF POTENTIALLY RELEVANT DATA (NONCANCER AND CANCER)	5
HUMAN STUDIES	8
ANIMAL STUDIES	8
Oral Exposures	8
Inhalation Exposures	9
OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)	10
Acute Toxicity	10
Genotoxicity	10
DERIVATION 01 PROVISIONAL VALUES	12
DERIVATION OF ORAL REFERENCE DOSES	12
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS	13
CANCER WEIGHT-OF-EVIDENCE DESCRIPTOR	13
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES	13
APPENDIX A. SCREENING PROVISIONAL VALUES	14
APPENDIX B. DATA TABLES	19
APPENDIX C. BENCHMARK DOSE MODELING RESULTS	23
APPENDIX D. REFERENCES	41
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COMMONLY USED ABBREVIATIONS AND ACRONYMS1
a2u-g
alpha 2u-globulin
MN
micronuclei
ACGIH
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
7V-acetyl-P-D-glucosaminidase
AR
androgen receptor
NCEA
National Center for Environmental
AST
aspartate aminotransferase

Assessment
atm
atmosphere
NCI
National Cancer Institute
ATSDR
Agency for Toxic Substances and
NOAEL
no-observed-adverse-effect level

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

number

relationship
CBI
covalent binding index
RBC
red blood cell
CHO
Chinese hamster ovary (cell line cells)
RDS
replicative DNA synthesis
CL
confidence limit
RfC
inhalation reference concentration
CNS
central nervous system
RfD
oral reference dose
CPN
chronic progressive nephropathy
RGDR
regional gas dose ratio
CYP450
cytochrome P450
RNA
ribonucleic acid
DAF
dosimetric adjustment factor
SAR
structure activity relationship
DEN
diethylnitrosamine
SCE
sister chromatid exchange
DMSO
dimethylsulfoxide
SD
standard deviation
DNA
deoxyribonucleic acid
SDH
sorbitol dehydrogenase
EPA
Environmental Protection Agency
SE
standard error
ER
estrogen receptor
SGOT
serum glutamic oxaloacetic
FDA
Food and Drug Administration

transaminase, also known as AST
FEVi
forced expiratory volume of 1 second
SGPT
serum glutamic pyruvic transaminase,
GD
gestation day

also known as ALT
GDH
glutamate dehydrogenase
SSD
systemic scleroderma
GGT
y-glutamyl transferase
TCA
trichloroacetic acid
GSH
glutathione
TCE
trichloroethylene
GST
glutathione-S-transferase
TWA
time-weighted average
Hb/g-A
animal blood-gas partition coefficient
UF
uncertainty factor
Hb/g-H
human blood-gas partition coefficient
UFa
interspecies uncertainty factor
HEC
human equivalent concentration
UFc
composite uncertainty factor
HED
human equivalent dose
UFd
database uncertainty factor
i.p.
intraperitoneal
UFh
intraspecies uncertainty factor
IRIS
Integrated Risk Information System
UFl
LOAEL-to-NOAEL uncertainty factor
IVF
in vitro fertilization
UFS
subchronic-to-chronic uncertainty factor
LC50
median lethal concentration
U.S.
United States of America
LD50
median lethal dose
WBC
white blood cell
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
LACTONITRILE (CASRN 78-97-7)
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 National Center for
Environment Assessment (NCEA) 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.
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 EPA
Office of Research and Development's (ORD's) NCEA, Superfund Health Risk Technical
Support Center (513-569-7300).
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INTRODUCTION
Lactonitrile, CASRN 78-97-7, belongs to a class of compounds known as cyanohydrins.
It is used mainly as a solvent and as an intermediate in the manufacture of lactic acid and its
derivatives, such as ethyl lactate (Lewis and Hawley, 2007; Cholod, 2001). Lactonitrile is listed
on EPA's Toxic Substances Control Act (TSCA) public inventory (U.S. EPA 2015a). is
registered with Europe's Registration, Evaluation, Authorization and Restriction of Chemicals
(REACH) program (ECHA 2017). and was assessed under the EPA's High Production Volume
(HPV)/Organisation for Economic Co-operation and Development (OECD) Screening
Information Data Set (SIDS) Programme (OECD. 2004). Lactonitrile is listed as an EPA
Extremely Hazardous Substance (S302) and has been assigned a Threshold Planning Quantity of
1,000 pounds (U.S. EPA 2015b).
The empirical formula for lactonitrile is C3H5NO, and its structure is shown in Figure 1.
Synonyms for lactonitrile include the following: laktonitrile, lactonitrite,
2-hydroxypropanenitrile, and 2-hydroxypropionitrile. Commercial production of lactonitrile
occurs by the base-catalyzed reaction of equimolar amounts of acetaldehyde and hydrogen
cyanide in the presence of 1.5 of 20% sodium hydroxide (Cholod. 2001). Table 1 summarizes
the physicochemical properties of lactonitrile. Lactonitrile is a straw-yellow liquid at room
temperature. It is unstable at high pH and will undergo acid hydrolysis to form propanoic acid
(Cholod. 2001). The hydrolysis half-life for lactonitrile was reported as 15 days at pH 9 and
25C; however, it was not hydrolyzed at pH 4 or 7 (ECHA. 2017). Lactonitrile's vapor pressure
indicates that it will exist almost entirely as a vapor in the atmosphere. The estimated half-life of
vapor-phase lactonitrile in air by reaction with photochemically produced hydroxyl radicals is
6.7 days. The moderate vapor pressure and Henry's law constant for lactonitrile indicate that it
may volatilize from either dry or moist surfaces. The estimated high water solubility and low
soil adsorption coefficient for lactonitrile indicate that the compound may leach to groundwater
or undergo runoff after a rain event. Based on screening tests, lactonitrile may also undergo
ready biodegradation in the environment (ECHA. 2017).
Figure 1. Lactonitrile Structure
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Table 1. Physicochemical Properties of Lactonitrile (CASRN 78-97-7)
Property (unit)
Value
Physical state
Liquid
Boiling point (C)
160.963
Melting point (C)
-403
Density (g/cm3 at 20C)
0.9877b
Vapor pressure (mm Hg at 25 C)
0.119a
pH (unitless)
NA
pKa (unitless)
NA
Solubility in water (mg/L at 25 C)
4.66 x 105 3
Octanol-water partition coefficient (log Kow)
-0.943
Henry's law constant (atm-m3/mol at 25C)
9.8 x 10 6 (estimated)3
Soil adsorption coefficient Koc (L/kg)
1 (estimated)3
Atmospheric OH rate constant (cm3/molecule-sec at 25C)
1.6 x 1012 (estimated)3
Atmospheric half-life (d)
6.7 (estimated)3
Relative vapor density (air = 1)
2.45
Molecular weight (g/mol)
713
Flash point (closed cup in C)
IT
"U.S. EPA (2012c).
bLide (2008).
kLewis (2012).
NA = not applicable.
A summary of available toxicity values for lactonitrile from EPA and other
agencies/organizations is provided in Table 2.
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Table 2. Summary of Available Toxicity Values for Lactonitrile (CASRN 78-97-7)
Source (parameter)3'b
Value (applicability)
Notes
Reference(s)
Noncancer
IRIS
NV
NA
U.S. EPA (2017)
HEAST
NV
NA
U.S. EPA (201 la)
DWSHA
NV
NA
U.S. EPA (2012a)
ATSDR
NV
NA
ATSDR (2017)
IPCS
NV
NA
IPCS (2017); WHO (2017)
Cal/EPA
NV
NA
Cal/EPA (2014); Cal/EPA (2017a):
Cal/EPA (2017b)
OSHA
NV
NA
OSHA (2006): OSHA (2011)
NIOSH
NV
NA
NIOSH (2016)
ACGIH
NV
NA
ACGIH (2016)
DOE (PAC)
PAC-1: 0.24 mg/m3;
PAC-2: 2.6 mg/m3;
PAC-3: 16 mg/m3
Based on TEEL values
DOE (2015)
USAPHC (air-MEG)
1-hr critical: 150 mg/m3;
1-hr marginal: 18 mg/m3;
1-hr negligible: 10 mg/m3
Based on TEEL values
U.S. APHC (2013)
Cancer
IRIS
NV
NA
U.S. EPA (2017)
HEAST
NV
NA
U.S. EPA (2011a)
DWSHA
NV
NA
U.S. EPA (2012a)
NTP
NV
NA
NTP (2014)
IARC
NV
NA
IARC (2015)
Cal/EPA
NV
NA
Cal/EPA (2011): Cal/EPA (2017a):
Cal/EPA (2017b)
ACGIH
NV
NA
ACGIH (2016)
aSources: ACGIH = American Conference of Governmental Industrial Hygienists; ATSDR = Agency for Toxic
Substances and Disease Registry; Cal/EPA = California Environmental Protection Agency; DOE = Department of
Energy; DWSHA = Drinking Water Standards and Health Advisories; HEAST = Health Effects Assessment
Summary Tables; 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;
USAPHC = U.S. Army Public Health Command.
Parameters: MEG = military exposure guideline; PAC = protective action criteria; TEEL = temporary emergency
exposure limit.
NA = not applicable; NV = not available.
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Non-date-limited literature searches were conducted in June 2015 and updated in
April 2017 for studies relevant to the derivation of provisional toxicity values for lactonitrile.
Searches were conducted using the 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 data: American Conference of Governmental Industrial
Hygienists (ACGIH), Agency for Toxic Substances and Disease Registry (ATSDR), California
Environmental Protection Agency (Cal/EPA), U.S. EPA Integrated Risk Information System
(IRIS), U.S. EPA Health Effects Assessment Summary Tables (HEAST), U.S. EPA Office of
Water (OW), U.S. EPA TSCATS2/TSCATS8e, U.S. HPV, European Centre for Ecotoxicology
and Toxicology of Chemicals (ECETOC), Japan Existing Chemical Data Base (JECDB),
European Chemicals Agency (ECHA), OECD SIDS, OECD International Uniform Chemical
Information Database (IUCLID), OECD HPV, National Institute for Occupational Safety and
Health (NIOSH), National Toxicology Program (NTP), Occupational Safety and Health
Administration (OSHA), and Defense Technical Information Center (DTIC).
REVIEW OF POTENTIALLY RELEVANT DATA
(NONCANCER AND CANCER)
Tables 3 A and 3B provide overviews of the relevant noncancer and cancer databases,
respectively, for lactonitrile and include all potentially relevant repeated-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" and the
term "significant(ly)," used throughout the document, indicate a/>value of < 0.05 unless
otherwise specified.
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Table 3A. Summary of Potentially Relevant Noncancer Data for Lactonitrile (CASRN 78-97-7)
Category"
Number of Male/Female,
Strain, Species, Study
Type, Reported Doses,
Study Duration
Dosimetryb
Critical Effects
NOAELb
LOAELb
Reference
(comments)
Notes0
Human
1. Oral (mg/kg-d)
ND
2. Inhalation (mg/m3)
ND
Animal
1. Oral (mg/kg-d)
Combined
subchronic
toxicity and
R/D screening
study
10 M/10 F, Crj:CD(SD)
rat; gavage (vehicle not
specified); 7 d/wk, 6 wk
(2 wk premating through
2 wk postmating [M] or
PND 3 [F])
ADD:
0,1.2,6,30
Systemic: Increased absolute and relative
liver weights, and centrilobular
hypertrophy in males; increased absolute
liver weight in females; transient clinical
signs of toxicity in both sexes
(hypolocomotion, hypopnea, salivation)
R/D: No observed effects
Systemic: 6
R/D: 30
Systemic: 30
R/D: NDr
UNEP (2003):
Mitsubishi
Chemical
Safety Institute
Ltd. (1992b)
NPR, PS
Based on UNEP
summary of
Japanese
language
publication with
data tables in
English
2. Inhalation (mg/m3)
ND
"Duration 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 ~90 days in typically used laboratory animal species); and chronic = repeated exposure for
>10% lifespan for humans (more than ~90 days to 2 years in typically used laboratory animal species) (U.S. EPA. 20021.
bDosimetry: Values are presented as ADDs (mg/kg-day) for oral noncancer effects. In contrast to other repeated exposure studies, values from animal gestational
exposure studies are not adjusted for exposure duration in calculation of the ADD.
Notes: NPR = not peer reviewed; PS = principal study.
ADD = adjusted daily dose; F = female(s); LOAEL = lowest-observed-adverse-effect level; M = male(s); ND = no data; NDr = not determined;
NOAEL = no-observed-adverse-effect level; PND = postnatal day; R/D = reproductive/developmental; UNEP = United Nations Environment Programme.
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Table 3B. Summary of Potentially Relevant Cancer Data for Lactonitrile (CASRN 78-97-7)
Category
Number of Male/Female, Strain, Species, Study
Type, Reported Doses, Study Duration
Dosimetry
Critical Effects
NOAEL
LOAEL
Reference
(comments)
Notes
Human
1. Oral (mg/kg-d)
ND
2. Inhalation (mg/m3)
ND
Animal
1. Oral (mg/kg-d)
ND
2. Inhalation (mg/m3)
ND
LOAEL = lowest-observed-adverse-effect level; ND = no data; NOAEL = no-observed-adverse-effect level.
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HUMAN STUDIES
Human data are limited to a single case report. A fatal case of poisoning, attributed to
lactonitrile, was reported in a worker exposed to lactonitrile while cleaning discharge pipes in a
factory where acrylonitrile was produced (Nauata et aL 1968). The man experienced severe
headache, nausea, palpitation, and abdominal pain while working. He was found unconscious
after leaving work and admitted to a hospital under a preliminary diagnosis of cyanide poisoning.
Despite medical intervention, the patient died. Autopsy observations included intense posterior
lividity, petechial hemorrhages in conjunctiva and in mucosa of the renal pelvis, blood and fluid
in pericardium, and marked congestion of all viscera. Gas chromatography was used to verify
the presence of acrylonitrile, but showed that lactonitrile was present in much higher quantities
in the waste products collected from the factory discharge pipes, the deceased patient's clothing
(some items of which, most notably the undershirt and mask, had no acrylonitrile at all), and
blood and urine collected postmortem. The authors hypothesized that in the heavy rain that was
falling, lactonitrile has dissolved in water and saturated in the thick, tight clothing, from which it
was absorbed into the body.
ANIMAL STUDIES
Oral Exposures
Repeated-dose oral toxicity data are limited to an unpublished OECD Test Guideline 422
combined repeated-dose and reproductive/developmental (R/D) screening toxicity study
conducted by the Mitsubishi Chemical Safety Institute Ltd. (1992b) and written in Japanese.
Data tables are presented in English, and an English summary is available in the OECD SIDS
dossier (UNEP. 2003).
UNEP (2003); Mitsubishi Chemical Safety Institute Ltd. (1992b)
Groups of male and female Crj:CD(SD) rats (10/sex/group) were exposed to lactonitrile
(purity 92.3%) at doses of 0, 1.2, 6, or 30 mg/kg-day via gavage, 7 days/week for 14 days before
mating, and during a mating period of up to 2 weeks. Daily dosing of females continued through
gestation until Postnatal Day (PND) 3; males continued to receive daily gavage doses for
2 weeks postmating (~6 weeks total exposure). It is unclear from the English summary what
vehicle was used; however, the summary indicates that concurrent vehicle controls were used.
Rats were evaluated daily for mortality and clinical signs of toxicity. Body weight and food
consumption were measured weekly. Reproductive endpoints that were evaluated included the
length of time between initial pairing and detection of coitus (precoital interval); mating, fertility,
implantation, delivery, gestational and viability indices; numbers of corpora lutea, implantation
sites, and live and dead offspring; gestation length; and F1 birth weight. On PND 4, all F0 and
F1 animals were weighed and sacrificed. At terminal sacrifice, blood was collected from
F0 males for clinical chemistry (aspartate aminotransferase [AST], alanine aminotransferase
[ALT], alkaline phosphatase [ALP], y-glutamyl transferase [GGT], total bilirubin, blood urea
nitrogen [BUN], creatinine, glucose, total cholesterol, triglyceride, total protein, albumin,
calcium, inorganic phosphate, sodium, potassium, chloride) and hematology (red blood cell
[RBC] count, white blood cell [WBC] count, and differential, reticulocyte count, platelet count,
hematocrit [Hct], hemoglobin [Hb] concentration, mean corpuscular volume [MCV], mean
corpuscular hemoglobin [MCH], mean corpuscular hemoglobin concentration [MCHC]). Based
on data presentation, it is unclear whether clinical chemistry or hematological evaluations were
conducted in F0 females. The thymus, liver, kidneys, testes, and epididymides from F0 animals
were removed and weighed. All F0 and F1 animals were examined grossly, and the liver, heart,
spleen, kidneys, adrenals, testes, and epididymides were fixed for histopathological evaluation in
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control and high-dose F0 animals. The livers were also examined microscopically in low- and
mid-dose F0 males.
One control male died on Day 23 of the experiment due to "manipulation error" (not
further defined) and one high-dose female died on Day 41 of the experiment (2 days postpartum)
due to disseminated intravascular coagulation which could be treatment-related, but hematology
was not evaluated in female rats. No other mortalities occurred. Transient clinical signs of
toxicity (decreased locomotion, hypopnea, salivation) were observed in the majority of high-dose
males and females; clinical signs of toxicity were not observed in low- or mid-dose rats. No
exposure-related changes were observed in body weight or food consumption. All reproductive
endpoints were comparable between the exposure and control groups. Slight, but statistically
significant increases were observed in several clinical chemistry values in high-dose males,
including increased total protein (8%), albumin (9%), and calcium (4%), but the clinical
relevance of these small changes is unclear (see Table B-l). Similarly, the relevance of a
statistically significant 17% decrease in serum AST is unknown while serum ALT levels did not
differ from control (see Table B-l). There is an upward trend in serum bilirubin (75, 200, and
150%, at the low, middle, and high dose, respectively) in F0 males compared with control
animals. Elevated bilirubin reached statistical significance at the mid-dose (200%) but not at the
high and low dose (see Table B-l).
No significant hematological differences were observed between exposed and control
F0 males. Absolute and relative liver weights were statistically and biologically significantly
elevated by 23 and 21%, respectively, in F0 males exposed to 30 mg/kg-day lactonitrile, but not
in the lower dose F0 male groups; absolute liver weights were biologically (>10%) but not
statistically elevated at 30 mg/kg-day in exposed F0 females compared with control animals
(see Table B-2). No exposure-related changes were observed in thymus, kidney, testes, or
epididymides weights in F0 rats (see Table B-2). Elevated liver weights in high-dose males were
accompanied by a statistically significantly increased incidence of grossly observed liver
enlargement, and microscopically observed centrilobular hypertrophy; these findings were not
observed in any other dose group (see Table B-3). A centrilobular fatty change was observed in
a single male rat (1/10 animals) in the high-dose group, but this increase was not statistically
significant. No other exposure-related lesions were observed in F0 animals. No abnormal gross
findings were reported in exposed F1 pups.
A systemic no-observed-adverse-effect level (NOAEL) of 6 mg/kg-day and a
lowest-observed-adverse-effect level (LOAEL) of 30 mg/kg-day are identified based on a
>10%) increase in absolute and relative liver weights and centrilobular hypertrophy in males, a
>10%) increase in absolute liver weight in females, and transient clinical signs of toxicity in both
sexes (hypolocomotion, hypopnea, salivation).
Inhalation Exposures
No data regarding the chronic- or subchronic-duration toxicity of lactonitrile to animals
following repeated-dose inhalation exposure have been identified.
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OTHER DATA (SHORT-TERM TESTS, OTHER EXAMINATIONS)
Acute Toxicity
Oral median lethal dose (LD50) values of 21-87 mg/kg have been reported in rats, with
deaths occurring as low as 10 mg/kg (IJNKP. 2003; Hartung. 1993; Mitsubishi Chemical Safety
Institute Ltd.. 1992a; Smyth et al.. 1969). Clinical signs observed in male and female rats
(SD/Crj:CD) at acute exposures (>21 mg/kg) included hypopnea, decreased activity, ataxia,
pronation, and convulsions; focal hemorrhaging in the lung, and dilation of the atrium were
observed in animals that died (Mitsubishi Chemical Safety Institute Ltd.. 1992a). An inhalation
study reported no deaths among six rats (sex and strain not reported) exposed to 62.5 ppm of
lactonitrile for 4 hours and 6/6 deaths after exposure to 125 ppm for 4 hours (Smvth et al.. 1969).
A single application of lactonitrile to the skin of rabbits (sex and strain not reported) resulted in
an LD511 value of 20 mg/kg (UNLP. 2003; Smvth et al.. 1969). For intraperitoneal (i.p.)
administration, an LD50 value of 15 mg/kg was reported in male CD-I mice (Kaplita and Smith.
1986). Clinical signs of toxicity exhibited were dyspnea, ataxia, hypothermia, and convulsions.
No other details regarding toxic effects were provided. Furthermore, the acute-duration data
came from either secondary sources, are published in a foreign language or lack details on
experimental methods, thus making interpretation questionable.
Genotoxicity
A limited number of genotoxicity studies indicate that lactonitrile is not mutagenic to
bacteria but has the potential to cause clastogenic effects in yeast and mammalian cells
(see Table 4 and below for details).
Lactonitrile was not mutagenic to Salmonella typhimurium or Escherichia coli, with or
without metabolic activation (FDSC HRI. 2016a; LNEP. 2003; Zeiger et al.. 1992).
Chromosomal aberrations (CAs) were induced in Chinese hamster lung (CHL) cells, with and
without metabolic activation (FDSC HRI. 2016b; UNEP. 2003). Additionally, lactonitrile
induced chromosomal malsegregation and respiratory deficiency in Saccharomyces cerevisiae
strain D61.M (/immermann and Mohr. 1992).
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Table 4. Summary of Lactonitrile (CASRN 78-97-7) Genotoxicity
Endpoint
Test System
Doses/Concentrations
Tested
Results
without
Activation3
Results
with
Activation3
Comments
Reference(s)
Genotoxicity studies in prokaryotic organisms
Mutation
Salmonella
typhimurium TA97,
TA98, TA100,
TA1535, and TA1537
0,0.1,0.3, 1.0,3.0, 10,33,
100, 333, 500 ng/plate


Cytotoxicity was observed >100 |ig/platc.
Zeieeretal. (1992)

Mutation
S. typhimurium
TA100, TA1535,
TA98, and TA1537
0, 4.69, 9.38, 18.75, 37.5,
75, 150 ng/plate


Cytotoxicity was observed at 150 |ig/platc.
I DSC HRI (2016a):
UNEP (2003)
Mutation
Escherichia coli WP2
uvrA
0, 75, 150, 300, 600,
1,200, 2,400 ng/plate


Cytotoxicity was observed at 2,400 |ig/platc.
FDSCHRI (2016a):
UNEP (2003)
Genotoxicity studies in nonmammalian eukaryotic organisms
Mitotic
malsegregation
Saccharomyces
cerevisiae strain
D61.M; continuous
assay (28C for 16 hr)
and cold-shock assay
(4 hr at 28C, 16-hr
ice bath, 4 hr at 28 C)
0, 1.96, 2.45, 2.94, 3.43,
4.41, 5.86 mg/mL
(continuous assay)
0, 2.45, 2.94, 4.41, 5.87,
7.81, 9.47 mg/mL
(cold-shock assay)
+
ND
Increased incidence of malsegregation was
observed at >2.94 mg/mL in continuous
incubation and >4.41 mg/mL in cold-shock assay.
An increased incidence of respiratory-deficient
cells was noted at >4.41 mg/mL in continuous
incubation and >5.87 mg/mL in cold-shock assay.
Zitntnermatm and
Mohr (1992)
Genotoxicity studies in mammalian cells in vitro
CAs
CHL cells
0,0.10, 0.19, 0.38 mg/mL
(-S9; 24- or 48-hr
incubation)
0,0.18, 0.36,0.71 mg/mL
(S9; 6-hr incubation)
+
+
CAs were induced at >0.38 mg/mL after 24-48 hr
without metabolic activation and at 0.71 mg/mL
after 6 hr with or without metabolic activation.
In a separate assay, cytotoxicity was observed at
1.00 mg/mL without metabolic activation and
>0.38 mg/mL with metabolic activation.
UNEP (2003);
FDSCHRI (2016b)
a+ = positive; - = negative
CA = chromosomal aberration; CHL = Chinese hamster lung; ND = no data.
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DERIVATION OF PROVISIONAL VALUES
Tables 5 and 6 present summaries of noncancer and cancer reference values, respectively.
Table 5. Summary of Noncancer Reference Values for Lactonitrile (CASRN 78-97-7)
Toxicity Type
(units)
Species/Sex
Critical Effect
p-Reference
Value
POD
Method
POD
(HED)
UFc
Principal Study
Screening
Subchronic p-RfD
(mg/kg-d)
Rat/F
Elevated absolute
liver weight
2 x 1(T3
BMDLio
0.5
300
Mitsubishi Chemical
Safety Institute Ltd.
(1992b)
Screening Chronic
p-RfD (mg/kg-d)
Rat/F
Elevated absolute
liver weight
2 x 1(T4
BMDLio
0.5
3,000
Mitsubishi Chemical
Safety Institute Ltd.
(1992b)
Subchronic p-RfC
(mg/m3)
NDr
Chronic p-RfC
(mg/m3)
NDr
BMDLio = 10% benchmark dose lower confidence limit; F = female(s); HED = human equivalent dose; NDr = not
determined; POD = point of departure; p-RfC = provisional reference concentration; p-RfD = provisional reference
dose; UFC = composite uncertainty factor.
Table 6. Summary of Cancer Reference Values for Lactonitrile (CASRN 78-97-7)
Toxicity Type (units)
Species/Sex
Tumor Type
Cancer Value
Principal Study
p-OSF (mg/kg-d) 1
NDr
p-IUR (mg/m3)-1
NDr
NDr = not determined; p-IUR = provisional inhalation unit risk; p-OSF = provisional oral slope factor.
DERIVATION OF ORAL REFERENCE DOSES
The available human and animal data are not considered sufficiently reliable to use in
deriving subchronic or chronic provisional reference doses (p-RfDs) for lactonitrile.
Repeated-dose oral toxicity data for lactonitrile are limited to an unpublished OECD combined
repeated-dose and R/D screening toxicity test conducted by the Mitsubishi Chemical Safety
Institute Ltd. (1992b) and written in Japanese. Because the study is not available in English, it
cannot be independently reviewed; therefore, it is not appropriate to use as the basis of a
provisional toxicity value. However, study data tables are provided in English, and there is an
English language summary of the study in the OECD S1DS dossier (UNKP. 2003); therefore, this
study is suitable for the derivation of "screening-level" values for subchronic and chronic oral
exposure to lactonitrile (see Appendix A). Further, the NOAEL for systemic toxicity
(6 mg/kg-day), identified in the Mitsubishi Chemical Safety Institute Ltd. (1992b) summary is
close to LD511 values (21-87 mg-kg-day) derived from several acute toxicity studies (UNEP.
2003; Hartung, 1993; Mitsubishi Chemical Safety Institute Ltd., 1992a; Smyth et ai, 1969). The
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close proximity of LD50 values to NOAELs found in the principal study supports the derivation
of screening values rather than provisional values.
DERIVATION OF INHALATION REFERENCE CONCENTRATIONS
No subchronic- or chronic-duration, repeated-exposure studies were located regarding
toxicity of lactonitrile to humans or animals by inhalation; therefore, neither subchronic nor
chronic provisional reference concentrations (p-RfCs) are derived.
CANCER WEIGHT-OF-EVIDENCE DESCRIPTOR
No relevant cancer data are available. Under the 2005 Guidelines for Carcinogen Risk
Assessment (U.S. EPA. 2005). there is "Inadequate Information to Assess Carcinogenic
Potential" for lactonitrile by either oral or inhalation exposure (see Table 7).
Table 7. Cancer Weight-of-Evidence Descriptor for Lactonitrile (CASRN 78-97-7)
Possible WOE Descriptor
Designation
Route of Entry (oral,
inhalation, or both)
Comments
"Carcinogenic to Humans "
NS
NA
There are no human data to support this.
"Likely to Be Carcinogenic to
Humans "
NS
NA
There are no suitable human or animal
studies to support this.
"Suggestive Evidence of
Carcinogenic Potential"
NS
NA
There are no suitable human or animal
studies to support this.
"Inadequate Information to
Assess Carcinogenic Potential"
Selected
Both
Available studies are insufficient to
assess carcinogenic potential.
"Not Likely to Be Carcinogenic
to Humans "
NS
NA
There are no suitable human or animal
studies to support this.
NA = not applicable; NS = not selected; WOE = weight of evidence.
DERIVATION OF PROVISIONAL CANCER POTENCY VALUES
The absence of suitable data precludes development of cancer potency values for
lactonitrile.
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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 toxicity values for lactonitrile. 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 Superfund Health Risk Technical Support Center 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 Superfund Health Risk Technical Support Center.
Derivation of a Screening Subchronic Provisional Reference Dose
The unpublished Japanese-language Organisation for Economic Co-operation and
Development (OECD) combined repeated-dose and reproductive/developmental (R/D) screening
toxicity test conducted by the Mitsubishi Chemical Safety Institute Ltd. (1992b) and summarized
in UMEP (2003). The UMEP (2003) described the report as "well controlled" and performed
according to Good Laboratory Practices (GLP), and is considered the principal study for use in
deriving the screening provisional reference doses (p-RfDs). The critical effect was increased
absolute liver weight in female rats observed at 30 mg/kg-day.
The subchronic-duration study by Mitsubishi Chemical Safety Institute Ltd. (1992b)
conducted daily administration of lactonitrile by gavage to Cij:CD(SD) rats (10/sex/group) for
6 weeks, including prior to mating and during a mating period. The report included a
comprehensive assessment of body weight, hematology (males only), serum chemistry (males
only), organ weights, and gross pathology of various organs. The authors also performed a
microbiological exam of several organs at the control (0 mg/kg-day) and high dose
(30 mg/kg-day), and male livers at all doses.
The study, however, is available as a secondary summary source and foreign language
publication. A lowest-observed-adverse-effect level (LOAEL) of 30 mg/kg-day with a
corresponding no-observed-adverse-effect level (NOAEL) of 6 mg/kg-day is identified based on
>10% increase in absolute and relative liver weights in male F0 rats, >10% increase in absolute
liver weight in female rats, and clinical signs of toxicity in male and female rats.
Potential points of departure (PODs) (see Table A-l) were modeled using the EPA's
Benchmark Dose Software (BMDS, Version 2.6). The incidence data for centrilobular
hypertrophy and clinical signs of toxicity were not suitable for benchmark dose (BMD) modeling
because effects were only observed in high-dose animals (zero incidence in control and
lower-dose animals). Details of the BMD modeling can be found in Appendix C. PODs
considered for derivation of the screening subchronic p-RfD are presented in Table A-l.
Bilirubin was elevated (75, 200, and 150% respectively) at 1.2, 6, and 30 mg lactonitrile/kg-day
in male rats, and the effect is consistent with liver toxicity. But the effect was not considered as
a POD because only the mid-dose (6 mg/kg-day) was statistically significant. Further, because
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the reference range of total bilirubin varies by up to 1,200% in humans (Cherneckv and Berger.
2013) and a comparable amount in CD rats (Giknis and Clifford. 2006). the toxicological
significance of a 200% elevation in bilirubin is uncertain.
Table A-l. PODs Considered for Derivation of the Screening Subchronic p-RfD
from the 6-Week Gavage Study in Crj:CD(SD) F0 Rats
(2 Weeks Premating through 2 Weeks Postmating [Males] or PND 3 [Females])3
Species/Sex
Critical Effect
NOAEL
(mg/kg-d)
LOAEL
(mg/kg-d)
POD Method
POD
(mg/kg-d)
Rat/M
Increased absolute liver weight
6
30
BMDLio
10
Rat/M
Increased relative liver weight
6
30
BMDLio
10
Rat/F
Increased absolute liver weight
6
30
BMDLio
2
Rat/M
Centrilobular hypertrophy
6
30
NOAEL
6
Rat/M &F
Clinical signs of toxicity
6
30
NOAEL
6
"Mitsubishi Chemical Safety Institute Ltd. (1992b).
BMDLio = 10% benchmark dose lower confidence limit; F = female(s); LOAEL = lowest-observed-adverse-effect
level; M = male(s); NOAEL = no-observed-adverse-effect level; PND = postnatal day; POD = point of departure;
p-RfD = provisional reference dose.
The lowest available POD is a 10% benchmark dose lower confidence limit (BMDLio) of
2 mg/kg-day for female rats with elevated absolute liver weight that is biologically significant
(>10%) change). This POD is protective of other effects observed following lactonitrile
exposure, including liver-weight changes in male and female rats. These liver-weight increases
are consistent with the centrilobular hypertrophy, gross liver enlargement, and centrilobular fatty
changes reported in male rats. Based on the consistency in these effects within the study, the
BMDLio for elevated absolute liver weight in female rats (2 mg/kg-day) is selected as the
POD for derivation of the screening subchronic p-RfD.
The BMDLio of 2 mg/kg-day was converted to a human equivalent dose (HED)
according to current U.S. EPA (201 lb) guidance. In Recommended Use of Body Weight3/4 as the
Default Method in Derivation of the Oral Reference Dose (U.S. EPA. 201 lb), the EPA endorses
body-weight scaling to the 3/4 power (i.e., BW3/4) as a default to extrapolate toxicologically
equivalent doses of orally administered agents from all laboratory animals to humans for the
purpose of deriving a p-RfD from effects that are not portal-of-entry effects.
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Following U.S. EPA (2011b) guidance, the POD for systemic toxicity is converted to an
HED through the application of a dosimetric adjustment factor (DAF)2 derived as follows:
DAF = (BWa1/4 - BWh1/4)
where
DAF = dosimetric adjustment factor
BWa = animal body weight
BWh = human body weight
Using a reference BWa of 0.25 kg for rats and a reference BWh of 70 kg for humans, the
resulting DAF is 0.24 (U.S. EPA. 2011b). Applying this DAF to the BMDLio of 2 mg/kg-day
yields a POD (HED) as follows:
POD (HED) = BMDLio (mg/kg-day) x DAF
= 2 mg/kg-day x 0.24
= 0.5 mg/kg-day
The screening subchronic p-RfD for lactonitrile was derived using the POD (HED) and 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):
Screening Subchronic p-RfD = POD (HED) UFc
= 0.5 mg/kg-day -^300
= 2 x 10"3 mg/kg-day
Table A-2 summarizes the uncertainty factors for the screening subchronic p-RfD for
lactonitrile.
2As described in detail in Recommended Use of Body Weight4 as the Default Method in Derivation of the Oral
Reference Dose (U.S. EPA. 201 lb), rate-related processes scale across species in a manner related to both the direct
(BWm) and allometric scaling (BW3/4) aspects such that BW3'4 ^ BW1 1 = BW ' converted to a
DAF = BWa"4 - BWi,1'4.
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Table A-2. Uncertainty Factors for the Screening Subchronic p-RfD for
Lactonitrile (CASRN 78-97-7)
UF
Value
Justification
UFa
3
A UFa of 3 (105) is applied to account for uncertainty in characterizing the toxicokinetic or
toxicodynamic differences between rats and humans following oral lactonitrile treatment. The
toxicokinetic uncertainty has been accounted for by calculating an HED through application of a
DAF as outlined in the EPA's Recommended Use of Body WeightB/4 as the Default Method in
Derivation of the Oral Reference Dose ('U.S. EPA. 20 lib).
UFd
10
A UFd of 10 is applied to account for the limited toxicity database for lactonitrile, specifically the
lack of a repeated-dose systemic toxicity study longer than 6 wk; lack of a repeated-dose toxicity
study in a second species; lack of a comprehensive evaluation in females; reproductive and
developmental toxicity in a second species; and the lack of evaluation of CNS toxicity based on
behavioral and clinical signs of toxicity.
UFh
10
A UFh of 10 is applied for intraspecies variability to account for human-to-human variability in
susceptibility in the absence of quantitative information to assess the toxicokinetics and
toxicodynamics of lactonitrile in humans.
UFl
1
A UFl of 1 is applied because the POD is a BMDLio.
UFs
1
A UFS of 1 is applied because a subchronic-duration study was selected as the principal study.
UFC
300
Composite UF = UFA x UFD x UFH x UFL x UFS.
BMDLio = 10% benchmark dose lower confidence limit; CNS = central nervous system; DAF = dosimetric
adjustment factor; HED = human equivalent dose; LOAEL = lowest-observed-adverse-effect level;
NOAEL = no-observed-adverse-effect level; POD = point of departure; UF = uncertainty factor; UFA = interspecies
uncertainty factor; UFC = composite uncertainty factor; UFD = database uncertainty factor; UFH = intraspecies
variability uncertainty factor; UFl = LOAEL-to-NOAEL uncertainty factor; UFS = subchronic-to-chronic
uncertainty factor.
Derivation of a Screening Chronic Provisional Reference Dose
The unpublished Japanese-language OECD combined repeated-dose and R/D screening
toxicity test conducted by the Mitsubishi Chemical Safety Institute Ltd. (1992b) is considered the
principal study for use in deriving the screening chronic p-RfD. No studies evaluating
chronic-duration exposure to lactonitrile have been identified. Therefore, the BMDLio of
2 mg/kg-day for elevated absolute liver weight in female rats is used as the POD for the
screening chronic p-RfD. An additional subchronic-to-chronic uncertainty factor (UFs) of 10 is
applied to account for extrapolation from a sub chronic-duration study.
The screening chronic p-RfD for lactonitrile is derived using the POD (HED) and a UFc
of 3,000 (reflecting a UFa of 3, a UFh of 10, a UFd of 10, and a UFs of 10):
Screening Chronic p-RfD = POD (HED) UFc
= 0.5 mg/kg-day ^ 3,000
= 2 x 10"4 mg/kg-day
Table A-3 summarizes the uncertainty factors for the screening chronic p-RfD for
lactonitrile.
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Table A-3. Uncertainty Factors for the Screening Chronic p-RfD for
Lactonitrile (CASRN 78-97-7)
UF
Value
Justification
UFa
3
A UFa of 3 (105) is applied to account for uncertainty in characterizing the toxicokinetic or
toxicodynamic differences between rats and humans following oral lactonitrile treatment. The
toxicokinetic uncertainty has been accounted for by calculating an HED through application of a
DAF as outlined in the EPA's Recommended Use of Body WeightB/4 as the Default Method in
Derivation of the Oral Reference Dose ('U.S. EPA. 20 lib).
UFd
10
A UFd of 10 is applied to account for the limited toxicity database for lactonitrile, specifically the
lack of a repeated-dose systemic toxicity study longer than 6 wk; lack of a repeated-dose toxicity
study in a second species; lack of a comprehensive evaluation in females; reproductive and
developmental toxicity in a second species; and the lack of evaluation of CNS toxicity based on
behavioral and clinical signs of toxicity.
UFh
10
A UFh of 10 is applied for intraspecies variability to account for human-to-human variability in
susceptibility in the absence of quantitative information to assess the toxicokinetics and
toxicodynamics of lactonitrile in humans.
UFl
1
A UFl of 1 is applied because the POD is a BMDLio.
UFS
10
A UFS of 10 is applied because a subchronic-duration study was selected as the principal study.
UFC
3,000
Composite UF = UFA x UFD x UFH x UFL x UFS.
BMDLio = 10% benchmark dose lower confidence limit; CNS = central nervous system; DAF = dosimetric
adjustment factor; HED = human equivalent dose; LOAEL = lowest-observed-adverse-effect level;
NOAEL = no-observed-adverse-effect level; POD = point of departure; UF = uncertainty factor; UFA = interspecies
uncertainty factor; UFC = composite uncertainty factor; UFD = database uncertainty factor; UFH = intraspecies
variability uncertainty factor; UFl = LOAEL-to-NOAEL uncertainty factor; UFS = subchronic-to-chronic
uncertainty factor.
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APPENDIX B. DATA TABLES
Table B-l. Selected Clinical Chemistry Endpoints in Male Crj:CD(SD) F0 Rats
Exposed to Lactonitrile by Gavage up to 6 Weeks
(2 Weeks Premating through 2 Weeks Postulating)3
Endpointb
Exposure Group, mg/kg-d
0
1.2
6
30
GOT (AST) (IU/L)
81  12.6
77  10.8 (-4.9%)
77  10.5 (-4.9%)
67  5.9* (-17.3%)
GPT (ALT) (IU/L)
27 6.4
27  7.3 (0%)
25  4.0 (-7.4%)
24 6.4 (-11.1%)
ALP (IU/L)
251 65.8
236  37.3 (-6%)
219 38.7 (-12.7%)
225  47.7 (-10.4%)
Total bilirubin (mg/dL)
0.04 0.05
0.07  0.05 (+75%)
0.12 0.04* (+200%)
0.10 0.07 (+150%)
Total protein (g/dL)
6.43 0.276
6.42 0.167 (-0.2%)
6.53 0.233 (+1.6%)
6.93  0.276** (+7.8%)
Albumin (g/dL)
3.85 0.122
3.79 0.094 (-1.6%)
3.88 0.134 (+0.8%)
4.2 0.169** (+9.1%)
Calcium (mg/dL)
9.1 0.25
9.1 0.19(0%)
9.2 0.3 (+1.1%)
9.5  0.2* (+4.4%)
"Mitsubishi Chemical Safety Institute Ltd. (1992b).
bValues are reported as mean  SD for 9 control rats and 10 rats/exposure group.
* Statistically significantly different from control value at p< 0.05, as reported by the study authors.
**Statistically significantly different from control value at p< 0.01, as reported by the study authors.
ALP = alkaline phosphatase; ALT = alanine aminotransferase; AST = aspartate amino transferase; GOT = glutamic
oxaloacetic transaminase; GPT = glutamic pyruvic transaminase; SD = standard deviation.
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Table B-2. Body and Organ Weights for Male and Female Crj:CD(SD) F0 Rats Exposed to Lactonitrile by Gavage for 6 Weeks

(2 Weeks Premating through 2 Weeks Postmating [Males] or PND 3 [Females])11

Exposure Group, mg/kg-d
Endpointb
0
1.2
6
30
Male
Sample size
9
10
10
10
Final body weight (g)
474 31.0
472 33.7 (-0.4%)
479 36.7 (+1.1%)
480 + 28.7 (+1.3%)
Liver
Absolute (g)
12.94  1.675
12.92  1.712 (-0.2%)
13.23 + 1.798 (+2.2%)
15.87+ 1.661** (+22.6%)
Relative (%)
2.72 0.201
2.73  0.203 (+0.4%)
2.75 + 0.176 (+1.1%)
3.30 + 0.261** (+21.3%)
Kidney
Absolute (g)
3.04 0.271
2.97  0.204 (-2.3%)
3.10 + 0.278 (+2%)
3.12+ 0.334 (+2.6%)
Relative (%)
0.64 0.041
0.63 0.016 (-1.6%)
0.65 + 0.020 (+1.6%)
0.65 + 0.062 (+1.6%)
Thymus
Absolute (mg)
340  62.7
382  67.4 (+12.4%)
360 + 95.2 (+5.9%)
381 + 87.1 (+12.1%)
Relative (%)
0.072 0.016
0.081 0.016 (+12.5%)
0.075+ 0.017 (+4.2%)
0.079 + 0.016 (+9.7%)
Testes
Absolute (g)
3.17  0.168
3.170.272 (0%)
3.33 + 0.187 (+5%)
3.22 + 0.389 (+1.6%)
Relative (%)
0.67  0.070
0.67  0.062 (0%)
0.70 + 0.062 (+4.5%)
0.67 + 0.086 (0%)
Epididymis
Absolute (g)
1.26 0.068
1.25 0.089 (-0.8%)
1.27 + 0.109 (+0.8%)
1.30 + 0.144 (+3.2%)
Relative (%)
0.27 0.025
0.26 0.027 (-3.7%)
0.27 + 0.026 (0%)
0.27 + 0.034 (0%)
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Table B-2. Body and Organ Weights for Male and Female Crj:CD(SD) F0 Rats Exposed to Lactonitrile by Gavage for 6 Weeks

(2 Weeks Premating through 2 Weeks Postmating [Males] or PND 3 [Females])11

Exposure Group, mg/kg-d
Endpointb
0
1.2
6
30
Female
Sample size
9
10
9
9
Final body weight (g)
303  15.6
307  13.4 (+1.3%)
31220.5 (+3%)
315 + 16.6 (+4%)
Liver
Absolute (g)
12.61 0.946
12.59  1.135 (-0.2%)
13.62 + 0.941 (+8%)
13.9+ 1.33 (+10.2%)
Relative (%)
4.17 0.347
4.10 0.252 (-1.7%)
4.37 + 0.206 (+4.8%)
4.41 + 0.353 (+5.8%)
Kidney
Absolute (g)
1.96 0.174
1.98 0.188 (+1%)
2.00 + 0.105 (+2%)
1.98 + 0.174 (+1%)
Relative (%)
0.65 0.067
0.65  0.056 (0%)
0.64 + 0.031 (-1.5%)
0.63 + 0.051 (-3.1%)
Thymus
Absolute (mg)
239 53.6
253  54.6 (+5.9%)
224 + 51.7 (-6.3%)
231 + 73.6 (-3.3%)
Relative (%)
0.079 0.019
0.082 0.015 (+3.8%)
0.071 + 0.015 (-10.1%)
0.073 + 0.020 (-7.6%)
"Mitsubishi Chemical Safety Institute Ltd. (1992b).
bValues are reported as mean  SD for 9-10 rats/group.
* Statistically significantly different from control value at p< 0.05, as reported by the study authors.
**Statistically significantly different from control value atp< 0.01, as reported by the study authors.
PND = postnatal day; SD = standard deviation.
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Table B-3. Gross and Microscopic Liver Findings for Male and Female Crj:CD(SD)
F0 Rats Exposed to Lactonitrile by Gavage for 6 Weeks (2 Weeks Premating
Through 2 Weeks Postmating [Males] or PND 3 [Females])3
Endpoint
Exposure Group, mg/kg-d
Male
Female
0
1.2
6
30
0
1.2
6
30
Gross necropsy findings
Liver enlargement
0/9b
0/10
0/10
9/10*
0/10
0/10
0/10
0/9
Microscopic findings
Centrilobular hypertrophy
0/9
0/10
0/10
7/10*
0/10
NDr
NDr
0/9
Centrilobular fatty change
0/9
0/10
0/10
1/10
0/10
NDr
NDr
0/9
Glycogen accumulation in hepatocytes
0/9
0/10
0/10
0/10
1/10
NDr
NDr
1/9
Microgranuloma
4/9
4/10
6/10
2/10
0/10
NDr
NDr
0/9
"Mitsubishi Chemical Safety Institute Ltd. (1992b).
bOne male died due to manipulation error on the 23rd day.
One female died due to disseminated intravascular coagulation on PND 2.
* Statistically significantly different from control value at p< 0.05, Fisher's exact test calculated for this review.
NDr = not determined; PND = postnatal day.
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APPENDIX C. BENCHMARK DOSE MODELING RESULTS
MODELING PROCEDURE FOR CONTINUOUS DATA
Benchmark dose (BMD) modeling of continuous data is conducted with EPA's
Benchmark Dose Software (BMDS, Version 2.6). All continuous models available within the
software are fit using a default benchmark response (BMR) of 1 standard deviation (SD) relative
risk unless a biologically determined BMR is available (e.g., BMR 10% for body weight based
on a biologically significant weight loss of 10%), as outlined in the Benchmark Dose Technical
Guidance (U.S. EPA. 2012b). An adequate fit is judged based on the %2 goodness-of-fit/>-value
(p > 0.1), magnitude of the scaled residuals in the vicinity of the BMR, 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-value < 0.1), the data set is considered unsuitable for BMD modeling. Among all models
providing adequate fit, the lowest benchmark dose lower confidence limit/benchmark
concentration lower confidence limit (BMDL/BMCL) is selected if the BMDL/BMCL estimates
from different models vary >threefold; otherwise, the BMDL/BMCL from the model with the
lowest Akaike's information criterion (AIC) is selected as a potential point of departure (POD)
from which to derive the provisional reference dose/provisional reference concentration
(p-RfD/p-RfC).
BMD MODELING TO IDENTIFY POTENTIAL PODs FOR THE DERIVATION OF A
SCREENING p-RfD
The following data sets were selected for BMD modeling:
	Absolute liver-weight data from male rats administered lactonitrile for 6 weeks
(2 weeks premating through 2 weeks postmating) (Mitsubishi Chemical Safety
Institute Ltd.. 1992b)
	Relative liver-weight data from male rats administered lactonitrile for 6 weeks
(2 weeks premating through 2 weeks postmating) (Mitsubishi Chemical Safety
Institute Ltd.. 1992b)
	Absolute liver-weight data from female rats administered lactonitrile for 6 weeks
(2 weeks premating through gestation and Postnatal Day [PND] 3) (Mitsubishi
Chemical Safety Institute Ltd., 1992b).
Absolute Liver Weight Data from Male Rats Administered Lactonitrile for 6 Weeks
(2 Weeks Premating through 2 Weeks Postmating)
The procedure outlined above was applied to the data for increased absolute liver weight
in F0 male Cij :CD(SD) rats administered lactonitrile via gavage 7 days/week for 2 weeks prior
to mating through 2 weeks postmating (6 weeks total exposure) (see Table C-l). Table C-2
summarizes the BMD modeling results. A BMR of 10% was selected, as this is generally
considered a biologically significant change in liver weight for laboratory rodents. With the
constant variance model applied, all models, except for the Exponential model 5 and the
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Hill model, provided adequate fit to the data. BMDLs for models providing adequate fit were
sufficiently close (differed by 
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Table C-2. BMD Modeling Results for Increased Absolute Liver Weight in Male Rats Exposed to Lactonitrile
by Gavage for 6 Weeks (2 Weeks Premating through 2 Weeks Postmating)
Model
Variance
/>-Valuca
Means
7?-Valuea
Scaled Residual:
Dose Nearest BMDb
AIC
BMD io
mg/kg-d
BMDLio
mg/kg-d
Constant variance
Exponential model 2C'd
0.99
0.94
-0.2682
82.91
13.45
10.06
Exponential model 3
0.99
0.94
0.01288
84.79
16.91
10.13
Exponential model 4
0.99
0.66
-0.3336
84.97
12.61
4.52
Exponential model 5
0.99
NA
1.87 x IO"6
86.78
7.39
4.70
Hillc
0.99
NA
3.33 x IO"7
86.78
7.65
4.58
Linear6
0.99
0.91
-0.334
82.97
12.61
9.06
Polynomial (2-degree)6
0.99
0.92
0.0181
84.79
17.37
9.16
Polynomial (3-degree)6
0.99
0.92
0.0181
84.79
17.37
9.16
Power0
0.99
0.94
0.0113
84.79
16.63
9.16
aValues <0.10 fail to meet conventional goodness-of-fit criteria.
bScaled residual at dose nearest to the BMD.
Tower restricted to >1.
dSelected model.
"Coefficients restricted to be positive.
AIC = Akaike's information criterion; BMD = maximum likelihood estimate of the exposure concentration associated with the selected BMR; BMDL = 95% lower
confidence limit on the BMD (subscripts denote benchmark response: i.e., io = exposure concentration associated with 10% extra risk); BMR = benchmark response;
NA = not applicable (computation failed).
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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]))
rho is set to 0.
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
MLE solution provided: Exact
Initial Parameter Values
Variable	Model 2
lnalpha	0.968728
rho(S)	0
a	12.8153
b	0.00705588
c	0
d	1
(S) = Specified
Parameter Estimates
Variable	Model 2
lnalpha	0.972076
rho	0
a	12.8113
b	0.00708778
c	0
d	1
Table of Stats From Input Data
Dose N Obs	Mean Obs Std Dev
0	9	12.94	1.675
1.2	10	12.92	1.712
6	10	13.23	1.798
30	10	15.87	1.661
Estimated Values of Interest
Dose	Est Mean	Est Std	Scaled Residual
0	12.81	1.626	0.2375
1.2	12.92	1.626	-0.001442
6	13.37	1.626	-0.2682
30	15.85	1.626	0.04529
Other models for which likelihoods are calculated:
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Model A1:
Model A2:
Model A3:
Model R:
Yij
= Mu(i) + e(i j )
Var{e(ij)}
= Sigma^2
Yij
= Mu(i) + e(i j )
Var{e(ij)}
= Sigma(i)^2
Yij
= Mu(i) + e(i j)
Var{e(ij)}
= exp(lalpha + log(mean(i)) * rho)
Yij
= Mu + e(i)
Var{e(ij)}
= Sigma^2
Model
A1
A2
A3
R
2
Likelihoods of Interest
Log (likelihood)	DF
-38.39019	5
-38.34946	8
-38.39019	5
-47.41099	2
-38.45548	3
AIC
86.78038
92.69892
86.78038
98.82198
82.91096
-35.84. This constant added to the
Additive constant for all log-likelihoods =
above values gives the log-likelihood including the term that does not
depend on the model parameters.
Explanation of Tests
Test
1:
Test
2 :
Test
3:
Test
4 :
Does response and/or variances differ among Dose levels? (A2
Are Variances Homogeneous? (A2 vs. Al)
Are variances adeguately modeled? (A2 vs. A3)
Does Model 2 fit the data? (A3 vs. 2)
R)
Tests of Interest
Test
Test 1
Test 2
Test 3
Test 4
-2*log(Likelihood Ratio)
18.12
0.08146
0.08146
0.1306
D. F.
6
3
3
2
p-value
0. 005932
0.994
0.994
0.9368
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.
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
The modeled
Model 2 seems
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BMD =	13.4471
BMDL =	10.0 64 6
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Relative Liver Weight Data from Male Rats Administered Lactonitrile for 6 Weeks
(2 Weeks Premating through 2 Weeks Postmating)
The procedure outlined above was applied to the data for increased relative liver weight
in F0 male Cij :CD(SD) rats administered lactonitrile via gavage, 7 days/week for 2 weeks prior
to mating through 2 weeks postmating (6 weeks total exposure) (see Table C-3). Table C-4
summarizes the BMD modeling results. With the constant variance model applied, all models,
except for the Exponential model 5 and the Hill model, provided adequate fit to the data.
BMDLs for models providing adequate fit were sufficiently close (differed by 
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Table C-4. BMD Modeling Results for Increased Relative Liver Weight in Male Rats Exposed to Lactonitrile by Gavage for 6 Weeks
(2 Weeks Premating through 2 Weeks Postulating)
Model
Variance
/j-Valuc11
Means
/j-Valuc11
Scaled Residual:
Dose Nearest BMDb
AIC
BMDio
mg/kg-d
BMDLio
mg/kg-d
Constant variance
Exponential model 2C'd
0.63
0.63
-0.7994
-78.97
14.19
11.68
Exponential model 3
0.63
0.92
0.000139
-77.88
20.63
12.09
Exponential model 4
0.63
0.28
-0.897
-76.74
13.41
10.77
Exponential model 5
0.63
NA
0.0001451
-75.88
20.33
6.23
Hillc
0.63
NA
0.000147
-75.88
20.28
6.28
Linear"
0.63
0.56
-0.897
-78.74
13.41
10.77
Polynomial (2-degree)6
0.63
0.93
0.000545
-77.88
20.40
11.33
Polynomial (3-degree)6
0.63
0.96
6.82 x IO"5
-77.89
22.10
11.33
Power0
0.63
0.92
0.00014
-77.88
20.34
11.32
aValues <0.10 fail to meet conventional goodness-of-fit criteria.
bScaled residual at dose nearest to the BMD.
Tower restricted to >1.
dSelected model.
"Coefficients restricted to be positive.
AIC = Akaike's information criterion; BMD = maximum likelihood estimate of the exposure concentration associated with the selected BMR; BMDL = 95% lower
confidence limit on the BMD (subscripts denote benchmark response: i.e., io = exposure concentration associated with 10% extra risk); BMR = benchmark response;
NA = not applicable (computation failed).
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Exponential Model 2, with BMR of 0.1 Rel. Dev. for the BMD and 0.95 Lower Confidence Level for BM
a)
CO
c
o
Q.
CO
a)
Q1
c
ro
a)
3.4
3.2
2.8
2.6
Exponential
BMDL
BMD
10
15
dose
20
25
30
15:22 03/14 2016
Figure C-2. Exponential (Model 2) for Increased Relative Liver Weight in Male Rats
Exposed to Lactonitrile by Gavage for 6 Weeks (2 Weeks Premating through 2 Weeks
Postmating) (Mitsubishi Chemical Safety Institute Ltd., 1992b)
Text Output for Figure C-2:
Exponential Model. (Version: 1.9; Date: 01/29/2013)
Input Data File:
C:/BMDS25 0_2014/Data/PTV-Lactonitrile/exp_RelLvrWtmale_Exp-ConstantVariance-BMR10_RelD
ev-Up.(d)
Gnuplot Plotting File:
Mon Mar 14 16:22:11 2016
BMDS Model Run
The form of the response function by Model:
Model 2:	Y[dose] = a * exp{sign * b * dose}
Model 3:	Y[dose] = a * exp{sign * (b * dose)Ad}
Model 4:	Y[dose] = a * [c-(c-l) * exp{-b * dose}]
Model 5:	Y[dose] = a * [c-(c-l) * exp{-(b * dose)Ad}]
Note: Y[dose] is the median response for exposure = dose;
sign = +1 for increasing trend in data;
sign = -1 for decreasing trend.
Model 2 is nested within Models 3 and 4.
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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]))
rho is set to 0.
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
MLE solution provided: Exact
Initial Parameter Values
Variable	Model 2
lnalpha	-3.20237
rho(S)	0
a	2.69213
b	0.00666932
c	0
d	1
(S) = Specified
Parameter Estimates
Variable	Model 2
lnalpha	-3.17875
rho	0
a	2.69089
b	0.00671863
c	0
d	1
Table of Stats From Input Data
Dose N Obs	Mean Obs Std Dev
0	9	2.72	0.201
1.2	10	2.73	0.203
6	10	2.75	0.176
30	10	3.3	0.261
Estimated Values of	Interest
Dose	Est Mean	Est Std	Scaled Residual
0 2.691 0.2041	0.4279
1.2 2.713 0.2041	0.2685
6 2.802 0.2041	-0.7994
30 3.292 0.2041	0.1272
Other models for which	likelihoods are calculated:
Model A1:	Yij	= Mu(i) + e(ij)
Var{e(ij)}	= Sigma^2
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Model A2:
Model A3:
Model R:
Yij = Mu (i) + e (i j )
Var{e(ij)} =
Sigma(i)^2

Yij =
Mu(i) + e(i j)

Var{e(ij)} =
exp(lalpha + log(mean(i)
) * rho)
Yij =
Mu + e(i)

Var{e(ij)} =
Sigma^2


Likelihoods of Interest
Model
Log(likelihood)
DF AIC
Al
42.94622
5 -75.89245
A2
43.80104
8 -71.60208
A3
42.94622
5 -75.89245
R
25.0323
2 -46.0646
2
42.4856
3 -78.97121
Additive constant for all log-likelihoods =	-35.84. 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.
Test
1:
Test
2 :
Test
3:
Test
4 :
Test
Test 1
Test 2
Test 3
Test 4
37.54
1.71
1.71
0.9212
p-value
< 0.0001
0.6348
0.6348
0.6309
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.
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
The modeled
Model 2 seems
Confidence Level
BMD
BMDL
0.950000
14.186
11.6832
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Absolute Liver Weight Data from Female Rats Administered Lactonitrile for 6 Weeks
(2 Weeks Premating through PND 3)
The procedure outlined above was applied to the data for increased (10.2%) absolute liver
weight in F0 female Crj :CD(SD) rats administered lactonitrile via gavage 7 days/week for
2 weeks prior to mating through PND 3 (6 weeks total exposure) (see Table C-l). Table C-5
summarizes the BMD modeling results. With the constant variance model applied, all models,
except for the Exponential model 5 and the Hill model, provided adequate fit to the data. The
BMDLs for models providing adequate fit differed by >threefold, so the model with the lowest
BMDLio was selected (Exponential model 4). Thus, the BMDLio of 2 mg/kg-day from this
model is selected for this endpoint (see Figure C-3 and the BMD text output for details).
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Table C-5. BMD Modeling Results for Increased Absolute Liver Weight in Female Rats Exposed to Lactonitrile
by Gavage for 6 Weeks (2 Weeks Premating through PND 3)
Model
Variance
p-Value3
Means
7?-Valuea
Scaled Residual:
Dose Nearest BMDC
AIC
BMDio
mg/kg-d
BMDLio
mg/kg-d
Constant variance
Exponential model 2
0.6741
0.1585
-0.27
49.55785
32.1179
19.991
Exponential model 3
0.6741
0.1585
0.01
49.55785
32.1179
19.991
Exponential model 4C'd
0.6741
0.4235
-0.33
48.51447
9.40352
2.17676
Exponential model 5
0.6741
NA
1.87 x IO"6
49.8756
6.57339
1.25823
Hillc
0.6741
NA
3.33 x IO"7
49.8756
7.30683
NA
Linear"
0.6741
0.1638
-0.33
49.491986
31.8573
19.3007
Polynomial (2-degree)6
0.6741
0.1638
0.02
49.491986
31.8573
19.3007
Polynomial (3-degree)6
0.6741
0.1638
0.02
49.491986
31.8573
19.3007
Power0
0.6741
0.1638
0.01
49.491986
31.8573
19.3007
aValues <0.10 fail to meet conventional goodness-of-fit criteria.
bScaled residual at dose nearest to the BMD.
Tower restricted to >1.
dSelected model.
"Coefficients restricted to be positive.
AIC = Akaike's information criterion; BMD = maximum likelihood estimate of the exposure concentration associated with the selected BMR; BMDL = 95% lower
confidence limit on the BMD (subscripts denote benchmark response: i.e., io = exposure concentration associated with 10% extra risk); BMR = benchmark response;
NA = not applicable (computation failed); PND = postnatal day.
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Exponential 4 Model, with BMR of 0.1 Rel. Dev. for the BMD and 0.95 Lower Confidence Limit for the BMDL
Exponential 4
14.5
(L)
Cfl
=
o
CL
Cfl
CD

13.5
Z
(C
CL)
12.5
BMDL
Biyip
10
0
5
15
20
25
30
dose
Figure C-3. Exponential (Model 4) for Increased Absolute Liver Weight in Female Rats
Exposed to Lactonitrile by Gavage for 6 Weeks (2 Weeks Premating through PND 3)
(Mitsubishi Chemical Safety Institute Ltd., 1992b)
Text Output for Figure C-3:
Exponential Model. (Version: 1.10; Date: 01/12/2015)
Input Data File: C:/Users/CCUBBIS/Desktop/LAC Female
Rat/exp_LACFemaleABSliver_Exp-ConstantVariance-BMR10-Up.(d)
Gnuplot Plotting File:
Wed Nov 23 10:44:58 2016
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;
Model 2 is nested within Models 3 and 4.
Model 3 is nested within Model 5.
Model 4 is nested within Model 5.
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Dependent variable = Mean
Independent variable = Dose
Data are assumed to be distributed: normally
Variance Model: exp(lnalpha +rho *ln(Y[dose]))
rho is set to 0.
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
MLE solution provided: Exact
Initial Parameter Values
Variable	Model 4
lnalpha	0.0776715
rho	0 Specified
a	11.9605
b	0.0493555
c	1.22027
d	1 Specified
Parameter Estimates
Variable	Model 4	Std. Err.
lnalpha	0.0949857	0.255662
a	12.4722	0.296315
b	0.20211	0.144696
c	1.11758	0.0376269
Table of Stats From Input	Data
Dose	N	Obs Mean	Obs Std Dev
0	9	12.61	0.946
1.2	10	12.59	1.135
6	9	13.62	0.941
30	9	13.9	1.33
Estimated Values of	Interest
Dose Est Mean Est Std Scaled Residual
0	12.47	1.049	0.3942
1.2	12.79	1.049	-0.5972
6	13.5	1.049	0.3361
30	13.94	1.049	-0.1008
Other models for which likelihoods are calculated:
Model A1:	Yij = Mu(i) + e(ij)
Var{e(ij)} = Sigma^2
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Model A2:	Yij
Var{e(ij)}
Model A3:	Yij
Var{e(ij)}
Model R:	Yij
Var{e(ij)}
Mu(i) + e(i j)
Sigma(i)A2
Mu(i) + e(i j)
exp(lalpha + log(mean(i)) * rho)
Mu + e(i)
SigmaA2
Model
A1
A2
A3
R
4
Likelihoods of Interest
Log (likelihood)	DF
-19.93692	5
-19.16914	8
-19.93692	5
-25.0757	2
-20.25724	4
AIC
49.87385
54.33828
49.87385
54.15141
48 .51447
Additive constant for all log-likelihoods =	-34. 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
Test 1: Does response and/or variances differ among Dose levels? (A2 vs. R)
Test 2: Are Variances Homogeneous? (A2 vs. Al)
Test 3: Are variances adeguately modeled? (A2 vs. A3)
Test 6a: Does Model 4 fit the data? (A3 vs 4)
Tests of Interest
Test	-2*log(Likelihood Ratio)	D. F.	p-value
Test 1	11.81	6	0.06627
Test 2	1.536	3	0.6741
Test 3	1.536	3	0.6741
Test 6a	0.6406	1	0.4235
The p-value for Test 1 is greater than .05. There may not be a
difference between responses and/or variances among the dose levels
Modelling the data with a dose/response curve may not be appropriate.
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 6a is greater than .1. Model 4 seems
to adeguately describe the data.
Benchmark Dose Computations:
Specified Effect = 0.100000
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Risk Type = Relative deviation
Confidence Level = 0.950000
BMD =	9.40352
BMDL =	2.17 67 6
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APPENDIX D. REFERENCES
ACGIH (American Conference of Governmental Industrial Hygienists). (2016). 2016 TLVs and
BEIs: Based on documentation of the threshold limit values for chemical substances and
physical agents and biological exposure indices. Cincinnati, OH.
https://www.acgih.ore/forms/store/ProductFormPublic/20164lvs-and-beis
AT SDR (Agency for Toxic Substances and Disease Registry). (2017). Minimal risk levels
(MRLs). June 2017. Atlanta, GA: Agency for Toxic Substances and Disease Registry
(ATSDR). Retrieved from http://www.atsdr.cdc.gov/mrls/index.asp
Cal/EPA (California Environmental Protection Agency). (201 1). Hot spots unit risk and cancer
potency values. Appendix A. Sacramento, CA: Office of Environmental Health Hazard
Assessment.
http://standards.nsf.org/apps/group public/download, php?document id= 19121
Cal/EPA (California Environmental Protection Agency). (2014). All OEHHA acute, 8-hour and
chronic reference exposure levels (chRELs) as of June 2014. Sacramento, CA: Office of
Health Hazard Assessment, http://www.oehha.ca.gov/air/allrels.html
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