SCREENING-LEVEL HAZARD CHARACTERIZATION
OF HIGH PRODUCTION VOLUME CHEMICALS
CHEMICAL CATEGORY NAME
Alkyl Nitriles
SPONSORED CHEMICALS
Propionitrile (CAS No. 107-12-0)
[9th CI Name: Propanenitrile]
Butyronitrile (CAS No. 109-74-0)
[9th CI Name: Butanenitrile]
Isobutyronitrile (CAS No. 78-82-0)
[9th CI Name: Propanenitrile, 2-methyl-]
October 2007
INTERIM
Prepared by
High Production Volume Chemicals Branch
Risk Assessment Division
Office of Pollution Prevention and Toxics
Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460-0001
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SCREENING-LEVEL HAZARD CHARACTERIZATION
OF HIGH PRODUCTION VOLUME CHEMICALS
The High Production Volume (HPV) Challenge Program1 is a voluntary initiative aimed at developing and making
publicly available screening-level health and environmental effects information on chemicals manufactured in or
imported into the United States in quantities greater than one million pounds per year. In the Challenge Program,
producers and importers of HPV chemicals voluntarily sponsor chemicals; sponsorship entails the identification and
initial assessment of the adequacy of existing toxicity data/information, conducting new testing if adequate data do
not exist, and making both new and existing data and information available to the public. Each complete data
submission contains data on 18 internationally agreed to "SIDS" (Screening Information Data Set1'2) endpoints that
are screening-level indicators of potential hazards (toxicity) for humans or the environment.
The Environmental Protection Agency's Office of Pollution Prevention and Toxics (OPPT) is evaluating the data
submitted in the HPV Challenge Program on approximately 1400 sponsored chemicals. OPPT is using a hazard-
based screening process to prioritize review of the submissions. The hazard-based screening process consists of two
tiers described below briefly and in more detail on the Hazard Characterization website3.
Tier 1 is a computerized sorting process whereby key elements of a submitted data set are compared to established
criteria to "bin" chemicals/categories for OPPT review. This is an automated process performed on the data as
submitted by the sponsor. It does not include evaluation of the quality or completeness of the data.
In Tier 2, a screening-level hazard characterization is developed by EPA that consists of an objective evaluation of
the quality and completeness of the data set provided in the Challenge Program submissions. The evaluation is
performed according to established EPA guidance2'4 and is based primarily on hazard data provided by sponsors.
EPA may also include additional or updated hazard information of which EPA, sponsors or other parties have
become aware. The hazard characterization may also identify data gaps that will become the basis for a subsequent
data needs assessment where deemed necessary. Under the HPV Challenge Program, chemicals that have similar
chemical structures, properties and biological activities may be grouped together and their data shared across the
resulting category. This approach often significantly reduces the need for conducting tests for all endpoints for all
category members. As part of Tier 2, evaluation of chemical category rationale and composition and data
extrapolation(s) among category members is performed in accord with established EPA2 and OECD5 guidance.
The screening-level hazard characterizations that emerge from Tier 2 are important contributors to OPPT's existing
chemicals review process. These hazard characterizations are technical documents intended to support subsequent
decisions and actions by OPPT. Accordingly, the documents are not written with the goal of informing the general
public. However, they do provide a vehicle for public access to a concise assessment of the raw technical data on
HPV chemicals and provide information previously not readily available to the public. The public, including
sponsors, may offer comments on the hazard characterization documents.
The screening-level hazard characterizations, as the name indicates, do not evaluate the potential risks of a chemical
or a chemical category, but will serve as a starting point for such reviews. In 2007, EPA received data on uses of
and exposures to high-volume TSCA existing chemicals, submitted in accordance with the requirements of the
Inventory Update Reporting (IUR) rule. For the chemicals in the HPV Challenge Program, EPA will review the
IUR data to evaluate exposure potential. The resulting exposure information will then be combined with the
screening-level hazard characterizations to develop screening-level risk characterizations4'6. The screening-level
risk characterizations will inform EPA on the need for further work on individual chemicals or categories. Efforts
are currently underway to consider how best to utilize these screening-level risk characterizations as part of a risk-
based decision-making process on HPV chemicals which applies the results of the successful U.S. High Production
Volume Challenge Program and the IUR to support judgments concerning the need, if any, for further action.
1 U.S. EPA. High Production Volume (HPV) Challenge Program; http://www.epa.gov/chemrtk/index.htm.
2 U.S. EPA. HPV Challenge Program - Information Sources; http://www.epa.gov/chemrtk/pubs/general/guidocs.htm.
3 U.S. EPA. HPV Chemicals Hazard Characterization website (http://www.epa.gov/hpvis/abouthc.html).
4 U.S. EPA. Risk Assessment Guidelines; http://cfpub.epa.gov/ncea/raf/rafguid.cfm.
5 OECD. Guidance on the Development and Use of Chemical Categories; http://www.oecd.org/dataoecd/60/47/1947509.pdf.
6 U.S. EPA. Risk Characterization Program; http://www.epa.gov/osa/spc/2riskchr.htm.
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SCREENING-LEVEL HAZARD CHARACTERIZATION
Alkyl Nitriles
Introduction
The sponsors, Eastman Chemical Company and Solutia Inc., submitted a Test Plan and Robust Summaries to EPA
for the Alkyl Nitriles Category on November 17, 2003. EPA posted the submission on the ChemRTK HPV
Challenge website on December 19, 2003 (http://www.epa.gov/chemrtk/pubs/summaries/alkvntrl/cl4860tc.htm').
EPA comments on the original submission were posted to the website on May 5, 2004. Public comments were also
received and posted to the website. The sponsor submitted updated/revised documents on June 12, 2004, which
were posted to the ChemRTK website on September 1, 2004. The Alkyl Nitriles Category consists of the following
chemicals:
Propionitrile (CAS No. 107-12-0)
[9th CI Name: Propanenitrile]
Butyronitrile (CAS No. 109-74-0)
[9th CI Name: Butanenitrile]
Isobutyronitrile (CAS No. 78-82-0)
[9th CI Name: Propanenitrile, 2-methyl-]
This screening-level hazard characterization is based primarily on the review of the Test Plan and Robust
Summaries of studies submitted by the sponsors) under the HPV Challenge Program. In preparing the hazard
characterization, EPA considered its own comments and public comments on the original submission as well as the
sponsor's responses to comments and revisions made to the submission. The structures of the sponsored chemical(s)
are included in Appendix. Summary tables of SIDS endpoint data are included in the document. The screening-
level hazard characterization for environmental and human health toxicity is based largely on SIDS endpoints and is
described according to established EPA or OECD effect level definitions and hazard assessment practices.
Category Justification
All three category members have closely related molecular and generic chemical structure and the same
functionality. The category members differ in having either two or three carbons in the alkyl chain, and in the case
of the butyronitrile and isobutyronitrile members, the only difference is in their alky chain branching. The generic
structure of the category members is depicted as:
RC=N, where R = CH3CH2-, CH3CH2CH2- or (CH3)2CH-
Much of the category chemicals' behavior is due to the nitrile function. A putative metabolite of all three materials
is cyanide. The acute and repeated-dose toxicity data for the category members are similar to that of cyanide. In
addition, the relatively short aliphatic hydrocarbon side chains and lack of reactive functional groups result in very
similar physicochemical characteristics and environmental fate properties among the three chemicals. All three
category members are used primarily as intermediates that are chemically converted to other chemicals. There are
no reported uses in consumer products or formulations.
EPA agreed that the data provided by the sponsors demonstrate very similar physicochemical properties for the three
compounds. Data submitted for the ecotoxicity and human health endpoints show similarities among the three
compounds with respect to toxic effects and effect levels. The sponsor included data showing that the mode of
action for the mammalian toxicities of the alkyl nitriles is cyanide intoxication. In general, sufficient information
has been presented to support the category.
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Sum in an-Conclusion
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ciin irnunieui.
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decrcnscd wemlil unui. chnimes iu nrunu wemlils (iiicludiim lesies). nllernlinus in heninlnlnmcnl ;uid chuicnl
elienusiiA pnrnniclers ;iud ninrinhls ;il llie limhesi dnse Repented nrnl e\pnsures (' "2 uiu ku-hw dn> ) resulted iu
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wcmlil \ii iiierensed iueideuee nl" uunssilicd sieruehrne w;is seen ;il 4t> nud Si) nm ku-hw dn> I >111\ mmirile nud
isnhuis rniuirile e\pnsure \ in iulinlnlinu nlsn resulted mi iiierensed prc-iniplniiinlinu Insses nud deerensed lelnl hnd\
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elirnninsnninl nherrnlinus w lieu lesied iu viini nr in vivn kesulls nl' nieelinuisiie siudies uidienle llinl prnpinuiirile
nud h111\ rnuiirile nre ncli\nled In llie li\erin relense csnuidc. which is respnusihle Inrncuie ln\icil>
l lie pnieuiinl hcnllli lin/nrd nl'nlk\ I ininlcs cnleunrs uienihers is hiuli hnsed nil repenled-dnse nud dc\ clnpuiciiinl
ln\icil\
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1. Physical-Chemical Properties and Environmental Fate
A summary of physical-chemical properties and environmental fate data submitted is provided in Table 1. For the
purpose of the screening-level hazard characterization, the review and summary of these data was limited to the
octanol-water partition coefficient and biodegradation endpoints as indictors of bioaccumulation and persistence,
respectively.
Octanol-Water Partition Coefficient
Propionitrile (CAS No. 107-12-0)
Log Kow: 0.16 (measured)
Butyronitrile (CAS No. 109-74-0)
Log Kow: 0.53 (measured)
Isobutyronitrile (CAS No. 78-82-0)
Log Kow: 0.46 (measured)
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Biodegradation
Biodegradation tests conducted for propionitrile and butyronitrile were for inherent biodegradability and of shorter
durations (48 or 72 hours) than the recommended duration of 28 days. Therefore they are considered inadequate for
the purposes of the HPV Challenge Program. Data for isobutyronitrile are used for the read across purposes.
Proprionitrile and butyronitrile are considered readily biodegradable based on data for isobutyronitrile.
Isobutyronitrile (CAS No. 78-82-0)
A 14-day MITI test was conducted using isobutyronitrile (lOOmg/L) and activated sludge. The test article was 54 -
66% degraded after 14 days.
Isobutyronitrile is readily biodegradable.
Conclusion: The log Kow values for the alkyl nitriles category members indicate that their potential to
bioaccumulate is low. The alkyl nitriles category members are considered readily biodegradable, indicating that
they are not expected to persist in the environment.
Table 1. Summary of Physical-Chemical Properties and Environmental Fate Data
End points
Propionitrile
Butvronitrile
Isobutvronitrilc
(107-12-0)
(109-74-0)
(78-82-0)
Melting Point (°C)
-92.8 (m)
-112 (m)
-71.5 (m)
Boiling Point (°C)
97 (m)
117.5 (m)
103.8 (m)
Vapor Pressure
52 (m) at 20°C
26 (m)
55.2 (m)
(hPa at 25°C)
Log K„w
0.16 (m)
0.53 (m)
0.46 (m)
Water Solubility
(mg/L at 25°C)
93,380 (m)
33,000 (m)
39,000 (m)
Direct Photodegradation
0.194xl0"12 (e)
0.498xl0"12(e)
0.703xl0"12(e)
(cm3/molecule-sec)
Indirect (OH ) Photodegradation
(ll/2)
55.2 days (e)
55.2 days (e)
55.2 days (e)
Stability in Water (Hydrolysis) (t1/2)
Hydrolysis of nitriles cannot be estimated using EPIWIN.
Chemicals in this category are expected to be stable to hydrolysis.
Fugacity
(e)
(e)
(e)
(Level III Model)
Air (%)
14.4
15.0
17.8
Water (%)
48.7
47.9
47.3
Soil (%)
36.97
37.0
34.7
Sediment (%)
0.082
0.082
0.081
Biodegradation at 28 days (%)
No Data
No Data
55 - 66 (14-d)
54-66 (14 d)
54-66 (14 d)
(RA)
(RA)
(m) = measured data (i.e., derived from experiment); (e) = estimated data (i.e., derived from modeling); (RA) = read-across
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2. Environmental Effects - Aquatic Toxicity
A summary of aquatic toxicity data submitted for SIDS endpoints is provided in Table 2. The table also indicates
where data for tested category members are read-across (RA) to untested members of the category.
Acute Toxicity to Fish
Propionitrile (CAS No. 107-12-0)
(1) Fathead minnows (Pimephalespromelas) were exposed to measured concentrations of 375, 611, 887, 1100 and
2188 mg/L under flow-through conditions for 96 hours. One fish exposed to 1100 mg/L and all fish exposed to
2188 mg/L died by 24 hours. Affected fish lost schooling behavior, were darkly colored and lost equilibrium prior
to death.
96-h LCS0 = 1520 mg/L
(2) Bluegill sunfish (Lepomis macrochirus) were exposed to nominal concentrations of 10, 18, 32, 56 and 100 mg/L
under static conditions for 96 hours. Mortality was 10% in the 10 and 18 mg/L groups. The mortality rate for fish
exposed to 32 mg/L was 20% at 24 hours, 20% at 48 hours, 40% at 72 hours, and 50% at 96 hours. The mortality
rate for fish exposed to 56 mg/L was 0% at 24 hours, 40% at 48 and 72 hours, and 50% at 96 hours. The mortality
rate for fish exposed to 100 mg/L was 50% at 24 hours, and 90% at 48, 72 and 96 hours.
96-h LCS0 = 41.0 mg/L
(3) Rainbow trout (Salmo gairdneri) were exposed to nominal concentrations of 0, 100, 180, 320, 560 or 1000 mg/L
under static conditions for 96 hours. None of the fish exposed to 100 or 180 mg/L died. The mortality rate for fish
exposed to 320 mg/L was 10% at 24 hours, 20% at 48 hours, 30% at 72 hours, and 40% at 96 hours. The mortality
for fish exposed to 560 or 1000 mg/L was 100% by 24 hours.
96-h LCS0 = 340 mg/L
Butyronitrile (CAS No. 109-74-0)
Fathead minnow (,Pimephales promelas) were exposed to mean measured concentrations of 107 mg/L under static
conditions for 96 hours. No mortality occurred and all fish exhibited normal behavior and appearance.
96-h LCS0 > 107 mg/L
Isobutyronitrile (CAS No. 109-74-0)
Fathead minnow (,Pimephales promelas) were exposed to mean measured concentrations of 102.1 mg/L under static
conditions for 96 hours. No mortality occurred and all fish exhibited normal behavior and appearance.
96-h LCS0 > 102.1 mg/L
AcuteToxicity to Aquatic Invertebrates
Propionitrile (CAS No. 107-12-0)
Daphnia magna were exposed to a measured concentration of propionitrile at 100, 180, 320, 560 and 1000 mg/L
under static conditions for 48 hours. None of the controls or daphnids exposed to 100 mg/L died during the study.
One daphnid at 180 mg/L died between 24 and 48 hours. Mortality of daphnids exposed to 180 mg/L was 5% at 24
hours and 20% at 48 hours and exposed to 320 mg/L was 50% at 24 hours and 75% at 48 hours. All daphnids
exposed to 560 or 1000 mg/L died within 24 hours.
48-h ECS0 > 250 mg/L
Butyronitrile (CAS No. 109-74-0)
Daphnia magna were exposed to a mean measured concentration of 110 mg/L under static conditions for 48 hours.
All daphnids, but one (mortality), exposed to the test-article exhibited behavior comparable to controls.
48 h EC50 > 110 mg/L
Isobutyronitrile (CAS No. 78-82-0)
Daphnia magna were exposed to mean measured concentration of 94.3 mg/L under static conditions for 48 hours.
All daphnids exposed to test-article exhibited behavior comparable to controls.
48 h ECS0 > 94.3 mg/L
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Toxicity to Aquatic Plants
Propionitrile (CAS No. 107-12-0)
No test data were submitted for propionitrile. A 96-hour ECOSAR estimated EC50 value for green algae was
provided.
96-h ECS0 = 789 mg/L
Butyronitrile (CAS No. 109-74-0)
Green algae (Pseudokirchneriella subcapitata) were exposed to mean measured concentration 133.4 mg/L under
static conditions for 72 hours. Algae exposed to test material exhibited normal growth with respect to control.
EC50> 133.4 mg/L
Isobutyronitrile (CAS No. 78-82-0)
Green algae (P. subcapitata) were exposed to mean measured concentration 87.8 mg/L under static conditions for
72 hours. Algae exposed to test material exhibited normal growth with respect to control.
EC50 > 87.8 mg/L
Conclusion: The evaluation of available aquatic toxicity data for fish, aquatic invertebrates and aquatic plants
indicates that the potential acute hazard of the alkyl nitriles category members to aquatic organisms is low.
Table 2. Summary of Environmental Effects - Aquatic Toxicity Data
Endpoints
Propionitrile
(107-12-0)
Butyronitrile
(109-74-0)
Isobutyronitrile
(78-82-0)
Fish
96-h LCS0 (mg/L)
41 -1520 (m)
>107 (m)
> 102.1 (m)
Aquatic Invertebrates
48-h ECS0 (mg/L)
250 (m)
>110 (m)
> 94.3 (m)
Aquatic Plants
72-h ECS0 (mg/L)
(growth and biomass)
No Data
> 134.4
(RA)
789 (e)
> 134.4 (m)
> 87.8 (m)
(m) = measured data (i.e., derived from testing); (e) = estimated data (i.e., derived from modeling); (RA) = Read
Across
3. Human Health Effects
A summary of health effects data submitted for SIDS endpoints is provided in Table 3. The table also indicates
where data for tested category members are read-across (RA) to untested members of the category.
Acute Oral Toxicity
Propionitrile (CAS No. 107-12-0)
(1) Male and female Sprague-Dawley rats were administered single doses of propionitrile at 25.1, 31.6, 50.1,63.1 or
79.4 mg/kg-bw and observed for 14 days. Signs of toxicity included increasing weakness and collapse in both sexes
and tremors in two males. Necropsy of animals that died revealed hemorrhagic lungs and liver, discoloration of
liver, kidneys and spleen and acute gastrointestinal inflammation.
LDS0 = 40 mg/kg-bw
(2) Male and female Sprague-Dawley rats received single doses of propionitrile at 50.1, 63.1, 79.4, 100, 126, 158
mg/kg-bw (males) and 158, 200, 251, 316 mg/kg-bw (females). Signs of toxicity in both sexes included weight loss
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(at 1 - 3 days in survivors), increasing weakness, ocular discharge, tremors, convulsions, collapse and death.
Diarrhea and dyspnea were also observed in females. Animals that died had hemorrhagic lungs, liver hyperemia
and/or discoloration and gastrointestinal inflammation.
LDS0(male) = 75 mg/kg-bw
LDS0 (female) = 270 mg/kg-bw
Butyronitrile (CAS No. 109-74-0)
(1) Rats (strain and sex not reported) received butyronitrile as single doses ranging from 10 - 3200 mg/kg-bw.
Mortality occurred within 15 minutes to 1 day following exposure. Signs of toxicity (other than mortality) included
moderate to very weak, rapid respiration, prostration and very severe vasodialation (especially at lower doses).
LDS0 = 50 mg/kg-bw
(2) Rats (strain/ sex not reported) received butyronitrile as single doses ranging from 25 - 3200 mg/kg-bw. All
animals receiving 100 mg/kg-bw and above died within 1 day following exposure. Other than mortality, signs of
toxicity included moderate to severe tremors, vasodilation, rough coat, sides caved in, labored breathing and
convulsions.
LDS0 = 50 - 100 mg/kg-bw
(3) Male Carworth-Winstar rats received a single dose (concentrations not reported) of butyronitrile. Details of the
study were not provided.
LDS0 = 111 mg/kg-bw
Isobutyronitrile (CAS No. 78-82-0)
(1) Rats (strain and sex not reported) received isobutyronitrile at single doses ranging from 25 to 400 mg/kg-bw.
Mortality occurred within 1-4 hours following exposure. Reported sign of toxicity (other than mortality) included
weakness, ataxia and abnormal behavior (kicking).
LDS0 = 50 - 100 mg/kg-bw
(2) Male Carworth-Winstar rats received a single dose (not reported) of isobutyronitrile. Mortality and clinical
signs/observations were not reported.
LDS0 = 77 mg/kg-bw
Acute Dermal Toxicity
Propionitrile (CAS No. 107-12-0)
In three separate studies, propionitrile was dermally applied to closely clipped intact skin of male and female New
Zealand White rabbits at 12.5, 25, 50 or 100 mg/kg-bw under occluded conditions. Twenty-four hours after
exposure, wrappings were removed and the test sites were wiped free of test material. Signs of toxicity included
ataxia, convulsions, tremors, respiratory abnormalities (hyperpnea, hypopnea, dyspnea, and arrhythmic respiration)
hypoactivity, prostration, hypothermia, nasal or ocular discharge, fecal staining, nasal discharge, soft stool, reddened
nictitating membrane and reduced food consumption. Most animals in the 12.5 and 25 mg/kg dose groups were free
of significant abnormalities from days 3 to 14. Mortality occurred at the two high doses. Slight to very slight
erythema was evident among 50% of the survivors.
LDS0 = 40-90 mg/kg-bw
Butyronitrile (CAS No. 109-74-0)
New Zealand White rabbits were exposed to a single dose (not reported) of butyronitrile. Details of the test were not
reported.
LDS0 = 398 mg/kg-bw
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Isobutyronitrile (CAS No. 78-82-0)
New Zealand White rabbits were exposed to a single exposure (concentration not reported) of isobutyronitrile.
Mortality or clinical signs/observations were not reported.
LDS0 = 0.31 ml/kg (~ 239 mg/kg-bw)
Acute Inhalation Toxicity
Propionitrile (CAS No. 107-12-0)
Male and female Sprague-Dawley rats were exposed via inhalation to propionitrile vapor at 1.58, 2.51, 3.98, 6.31,
10.0 or 15.8 mg/L for 4 hours. All deaths occurred within 2-24 hours following exposure. Signs of toxicity
included salivation, lethargy, increasing weakness, tremors and convulsions. Animals that died had hemorrhagic
lungs, discolored liver (mottled in some) and acute gastrointestinal inflammation.
LC50 = 3.3 mg/L
Butyronitrile (CAS No. 109-74-0)
(1) Male and female rats (Sprague-Dawley) were exposed via inhalation to butyronitrile vapor at 1147 (~3.2 mg/L)
or 1220 (~ 3.4 mg/L) ppm for 1 hour and observed for 14 days. All rats survived the study duration. No clinical
signs were reported.
LC50 > ~ 3.4 mg/L
(2) Male and female Sprague-Dawley rats were exposed to butyronitrile vapor at concentrations of 1972, 4421, 6296
and 8261 ppm for 1 hour. Mortality was extensive in the top three groups and occurred on day 1. At 1972 ppm, one
animal died on day 1. An LC50 could not be calculated.
LC10 ~ 5.2 mg/L
Isobutyronitrile (CAS No. 78-82-0)
(1) Male and female Sprague-Dawley rats (5/sex/concentration) were exposed to isobutyronitrile at 1200 ppm (~3.4
mg/L) for 1 hour. All rats survived the study duration. No clinical signs were reported.
LC50 > ~3.4 mg/L
(2) Male and female Sprague-Dawley rats were exposed to isobutyronitrile vapor at concentrations of 1248, 1778
and 2709 ppm (~3.5, 5.0 and 7.7 mg/L, respectively). Deaths were 1/10, 5/10 and 8/10 at 1246, 1778 and 2709
ppm, respectively. Lethargy, sialorrhea, abnormal gait and narcosis were seen. Pulmonary function assessment
conducted on some rats revealed decrease in dynamic compliance and forced expiratory flow. These changes were
associated with pulmonary edema or congestion.
LCio = 3.3 mg/L
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Repeated-Dose Toxicity
Propionitrile (CAS No. 107-12-0)
(1) Male and female Sprague-Dawley rats (15/group) were exposed to propionitrile vapor at 0, 60, 120 or 209 ppm
(approximately 0.135, 0.271 and 0.472 mg/L/day, respectively) via whole-body inhalation for 6 hours/day, 5
days/week for 14 weeks. Effects at all exposure concentrations included labored breathing, nasal discharge,
salivation, discharge from the eyes, hypoactivity and/or alopecia. All effects were dose-dependent. All exposed
animals had decreased red blood cells and hemoglobin values and increased urine thiocyanate concentrations.
Mortality occurred at 209 ppm (three males). Arched back, tremors, convulsions, biting, pawing, biting and chining
against the cage, irritation of the conjunctiva and breathing difficulties were among the clinical signs observed.
Animals also exhibited significant (p<0.01) decreases in body weights. Absolute and/or relative heart, liver, spleen
and kidney weights were increased in males and/or females. Absolute testes weights were decreased in males;
however, no histopathological correlation was seen. Microscopic examination revealed changes in spleen in females
(hemosiderin deposition). Effects at 120 ppm included ataxia (2 females), weight decreases (males) and increased
absolute and/or relative spleen weights (males). Mean corpuscular hemoglobin concentrations were lower in males
than controls. There was a mild increase in hemosiderin deposition in spleen of females. In animals exposed to 60
ppm absolute and relative spleen weights were increased in males and serum thiocyanate concentrations were
marginally increased in males and females
LOAEL ~ 0.135 mg/L/day (based on increased organ weights and serum thiocyanate concentration)
NOAEL = Not established
(2) Male and female albino rats (5/sex/group) were exposed to propionitrile via drinking water at concentrations of
2.5, 12.5 and 62.5 mg/L/day for 28 days. From records of water consumption, the mean intake of propionitrile is
calculated as 0.32, 1.34 and 3.72 mg/kg-bw/day. Over the 28-day period, no differences between the groups
receiving the two lower concentrations of the compound and their respective controls were noted for mortality, food
intake and weight gain. At the highest concentration (3.72 mg/kg-bw/day) there was one death that occurred on
day 14; this animal had hemorrhagic lungs. At this dose food consumption, weight gain in both sexes was less than
for controls and efficiency of food utilization was impaired.
LOAEL = 3.72 mg/kg-bw/day (based on mortality and reduced food consumption and body weight gain)
NOAEL = 1.34 mg/kg-bw/day
Reproductive Toxicity
Propionitrile (CAS No. 107-12-0)
The sponsor conducted two fertility studies in which male rats were exposed in one study and were mated with
virgin females and female rats were exposed in another study and were mated with virgin males. The conventional
reproductive toxicity study was not conducted in which both treated sexes were mated to evaluate functional aspects
of reproduction. Based on EPA's comments, the sponsor submitted information on the evaluation of reproductive
organs from the 14-week repeated-dose toxicity study. This information along with the non-conventional
reproductive studies (fertility) and the available developmental toxicity study, EPA considers that the reproductive
toxicity endpoint has been addressed for the purposes of the HPV Challenge Program.
(1) Female Sprague-Dawley rats (24/concentration) were exposed to propionitrile at 0, 60, 120 or 210 ppm
(approximately 0.14, 0.27 and 0.47 mg/L/day, respectively) via whole-body inhalation 6 hours/day, daily for 21days
and were randomly mated with untreated males. Females continued the exposure regime until gestation day 13 or
15. Each female was examined for general health, body weight, gross lesions, pregnancy status, nidation sites and
number of corpora lutea. No mortality was reported. There were no effects on maternal body weight. Animals
exposed to 210 ppm exhibited arched back, lacrimation, salivation, hypoactivity, staining of facial fur and red nasal
encrustation. Red nasal encrustation was also present in animals from the two other groups. Alopecia was observed
in a dose-dependent manner. At necropsy (gross) uterine hydrometra was found bilaterally in one animal at the 210
ppm and in the left uterine horn in one animal exposed to 120 ppm. There was no observed effect on fertility.
Efficiency of mating and pregnancy rate was comparable between groups. The numbers of live implants,
resorptions, nidations, corpora lutea, pre- and post-implantation losses were not affected by treatment. Evaluation of
the vaginal smears of two females that did not copulate showed that one did not cycle (but was pregnant at
necropsy) and the other only went through the cycling stage of proestrus. The biological significance of this finding
could not be established because no additional information was provided on this finding.
10
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LOAEL (systemic toxicity) ~ 0.27 mg/L/day (based on clinical signs of toxicity)
NOAEL (systemic toxicity) ~ 0.14 mg/L/day
LOAEL (reproductive toxicity) > ~ 0.47 mg/L/day
NOAEL (reproductive toxicity) ~ 0.47 mg/L/day
(2) Male Sprague-Dawley rats (15/group) were exposed to propionitrile at 0, 60, 120 or 210 ppm (approximately
0.14, 0.27 and 0.47 mg/L/day, respectively) via whole-body inhalation 6 hours/day, daily for 46 days and were
randomly mated with untreated females. Mated females were weighed on gestation days 0 and 13. Males were
given a thorough physical examination and were observed for signs of toxicity, mortality and gross abnormalities.
One-half of the males in each group were examined for gross lesions of the testes, epididymides, prostate glands and
seminal vescicles. Mated females were euthanized on gestation day 13 and gross necropsies were performed and
pregnancy status, nidation sites and the number of corpora lutea were determined. During exposure body weights of
animals exposed to 210 ppm remained lower than those of controls, but were similar at study termination, following
a 2-week recovery period. Animals exposed to 210 ppm exhibited arched back, hypoactivity, labored breathing and
salivation. Behavioral observations included grinding teeth, head bobbing, body tremors, involuntary movement
and pawing at the cage. A few animals exposed to 120 ppm exhibited salivation and hypoactivity. Signs of toxicity
generally disappeared by the morning following exposure. Alopecia was also observed. Gross necropsy revealed
one animal in the 120 ppm dose group with a small right testis. Efficiency of mating was 34.4, 30.6,29.8 and 27.1%
and pregnancy rates were 90.5, 97.6, 90.0 and 97.4% at 0, 60, 120 and 210 ppm, respectively. The numbers of live
implants, resporptions, corpora lutea, pre- and post-implantation losses were not affected by treatment. Although
thedecrease in mating efficiency was dose-related, pregnancy rates were unaffected; therefore, the NOAEL was
established at the high dose.
LOAEL (systemic toxicity) ~ 0.27 mg/L/day (based on clinical signs of toxicity and changes in behavior)
NOAEL (systemic toxicity) ~ 0.14 mg/L/day
LOAEL (reproductive toxicity) > ~ 0.47 mg/L/day (based on effects on mating efficiency)
NOAEL (reproductive toxicity) ~ 0.47 mg/L/day
(3) In the 14-week repeated-dose study described previously, reproductive organs were evaluated. The absolute left
testes weights were decreased in males exposed to the highest concentration 209 ppm (~ 0.47 mg/L/day). The
relative testes weights were decreased in animals exposed to the lowest concentration 60 ppm (0.14 mg/L/day).
Histopathological examination did not correlate with these findings. There were no histopathological changes in the
ovaries, testes (with epididymides), pituitary, prostate, uterus (with cervix), mammary gland or thyroid.
Developmental Toxicity
Propionitrile (CAS No. 107-12-0)
Female Sprague-Dawley rats were exposed to propionitrile via oral gavage at concentrations of 0, 20, 40 or 80
mg/kg-bw/day during gestation days 6-19. A single mortality was reported in the high-dose group (80 mg/kg-
bw/day). Survival was 100% in the other groups. There was a slight to moderate reduction in mean maternal body
weight gain over the entire treatment period for the high-dose group. The mean maternal adjusted body weight
(body weight gain minus the uterus and its contents) of the high-dose group was also reduced in comparison to
controls and other treatment groups. There was no effect of treatment on the number of pregnancies, mean number
of viable fetuses, late resporptions, total implantations or corpora lutea. There was a marked increase in the number
of early resporptions and a corresponding increase in the number of post-implantation losses in the high-dose group.
There was no effect of treatment in fetal sex ratio. The mean fetal body weight was markedly decreased in the high-
dose group compared to controls. Malformations of the fetuses (and litters) were 5(3), 1(1), 1(1) and 0(0) at 0, 20,
40 and 80 mg/kg-bw/day, respectively. One fetus from the low- and mid-dose groups had a diaphragmatic hernia.
An increase in the number of fetuses and litters with unossified sternebrae was noted in the mid- and high-dose
group compared to controls.
LOAEL (maternal toxicity) = 80 mg/kg-bw/day (based on mortality and reduced body weight gain)
NOAEL (maternal toxicity) = 40 mg/kg-bw/day
LOAEL (developmental toxicity) = 40 mg/kg-bw/d (based on unossified sternebrae)
NOAEL (developmental toxicity) = 20 mg/kg-bw/day
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Butyronitrile (CAS No. 109-74-0)
Female Sprague-Dawley rats were exposed to butyronitrile via inhalation at 50, 100, 150 or 200 ppm (~ 0.14, 0.28,
0.42 or 0.56 mg/L/day, respectively) 6 hours/day during days 6 - 21 of gestation. All animals survived the study
duration. There was no effect on maternal weight gain. Indices of pregnancy were comparable among groups.
There was no significant effect of treatment on the mean number of implants or incidence of non-surviving implants
and resorptions. The mean number of live fetuses and sex ratios were not affected at any concentration. A
concentration-dependent trend toward a decrease in fetal body weight was seen with weights of fetuses from the 200
ppm group being reported as significant (statistical significance not provided). The incidence of visceral and
skeletal variations in treated fetuses was similar to controls. However, a single case of fused ribs was observed at
100 ppm.
LOAEL (maternal toxicity) > ~ 0.56 mg/L/day (based on no effects at the highest dose tested)
NOAEL (maternal toxicity) ~ 0.56 mg/L/day
LOAEL (developmental toxicity) ~ 0.56 mg/L/day (based on decreased fetal body weight)
NOAEL (developmental toxicity) ~ 0.42 mg/L/day
Isobutyronitrile (CAS No. 78-82-0)
Female Sprague-Dawley rats were exposed to isobutyronitrile via inhalation at 50, 100, 200 or 300 ppm (~ 0.14,
0.28, 0.56 or 0.84 mg/L/day, respectively) 6 hours/day during days 6 - 21 of gestation. One of 21 animals exposed
to 200 ppm and 3 of 21 exposed to 300 ppm died prior to study termination. The indices of non-surviving implants
and rate of embryonic resorptions (per litter) in rats exposed to 300 ppm were markedly greater than controls. The
mean number of live fetuses or sex ratio was unaffected. A dose-dependent decrease in fetal body weights (females
in the 200 ppm and both males and females in the 300 ppm) was noted. One case of unilateral hydronephrosis was
observed in one fetus from the 300 ppm group. The incidences of visceral and skeletal variations in treated fetuses
were not noticeably different from controls.
LOAEL (maternal toxicity) ~ 0.56 mg/L/day (based on mortality)
NOAEL (maternal toxicity) ~ 0.28 mg/L/day
LOAEL (developmental toxicity) ~ 0.56 mg/L/day (based on pre-implantation resorptions and decreased fetal
body weight)
NOAEL (developmental toxicity) ~ 0.28 mg/L/day
Genetic Toxicity - Gene Mutation
In vitro
Propionitrile (CAS No. 107-12-0)
In two studies, mouse lymphoma L5178Y cells were exposed to concentrations of 2143, 2714, 3286, 3857, 4429 or
5000 |ig/mL in the presence and absence of metabolic activation. All cultures exhibited mutant frequencies similar
to the negative (solvent, DMSO) controls. All positive controls responded appropriately.
Propionitrile was not mutagenic in this assay.
Butyronitrile (CAS No. 109-74-0)
A bacterial reverse mutation assay was conducted with butyronitrile using Salmonella typhimurium (TA98, TA100,
TA1535, TA1537) and Escherichia coli (WP2uvrA(pkM101) at concentrations of 100, 333, 1000, 3333 or 5000
(ig/plate in the presence and absence of metabolic activation. None of the tested concentrations were cytotoxic. No
increase in mutant frequency was evident at any concentration. No precipitate was observed at the maximum
concentration tested. Positive and negative controls were explicitly employed and responded appropriately.
Butyronitrile was not mutagenic in this assay.
Isobutyronitrile (CAS No. 78-82-0)
Reverse mutation studies were conducted with isobutyronitrile in S. typhimurium (TA98, TA100, TA1535, TA
1537) and it. coli (WP2uvrA(pkM101) Using concentrations of 100, 333, 1000, 3333 or 5000 (ig/plate in the
presence and absence of metabolic activation. None of the tested concentrations were cytotoxic. No increase in
mutant frequency was evident at any concentration. No precipitate was observed at the maximum concentration
tested. Positive and negative controls were explicitly employed and responded appropriately.
Isobutyronitrile was not mutagenic in this assay.
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Genetic Toxicity - Chromosomal Aberrations
In vitro
Butyronitrile (CAS No. 109-74-0)
Chinese hamster ovary (CHO) cells were exposed to butyronitrile at concentrations of 4.77, 6.81, 9.73, 13.9, 19.9,
28.4, 40.5, 57.8, 82.6, 118, 169, 241, 344, 491 and 701 (ig/mL in the presence and absence of metabolic activation.
Cells were harvested after incubation periods, fixed, stained and analyzed for mitotic index and chromosomal
aberrations. No significant increases in cells with chromosomal aberrations, polyploidy or reduplication were
observed. None of the concentrations caused a significant reduplication in mitotic index. The positive and negative
controls responded appropriately. No cytogenetic activity was seen in this assay.
Butyronitrile did not induce chromosomal aberrations in this assay.
Isobutyronitrile (CAS No. 78-82-0)
CHO cells were exposed to butyronitrile at concentrations of 239, 342, 489 and 669 (ig/mL (without metabolic
activation) and 296, 394, 525 and 700 (ig/mL (with metabolic activation). Cells were harvested after incubation
periods, fixed, stained and analyzed for mitotic index and chromosomal aberrations. No significant increases in
cells with chromosomal aberrations, polyploidy or endoreduplication were observed. None of the concentrations
caused a significant reduplication in mitotic index. The positive and negative controls responded appropriately. No
cytogenetic activity was seen in this assay.
Isobutyronitrile did not induce chromosomal aberrations in this assay.
In vivo
Propionitrile (CAS No. 107-12-0)
Male and female Sprague-Dawly rats were administered propionitrile at 0, 100 and 200 mg/kg-bw via oral gavage.
Animals were euthanized at 6, 24 or 48 hours following dosing, femur bones were removed, bone marrow cells were
collected, fixed and slides were prepared, stained and analyzed for the mean mitotic indices, chromosome numbers,
percent aberrant cells and mean number of aberrations per cell. There was no effect of treatment with proponitrile
on the frequency of chromosomal aberrations, aberrations per cell, mean chromosome number or mitotic index in
comparison to the control animals at any time point. Positive controls resulted in the expected outcome.
Propionitrile did not induce chromosomal aberrations in this assay.
Additional Information
Mechanistic Study
Propionitrile (CAS No, 107-12-0) and Butyronitrile (CAS No. 109-74-0)
(1) Male mice received a single dose of propionitrile or butyronitrile via intraperitoneal (i.p.) injection. Mice were
divided into 3 groups of 10 animals each. Group 1 received 45 mg/kg-bw i.p. propionitrile only; Group 2 received
i.p. injections of 75 mg/kg-bw sodium nitrite (a cyanide antagonist)20 minutes before and 100 minutes after i.p.
injection of 45 mg/kg propionitrile and Group 3 received i.p. injections of 1 g/kg-bw sodium thiosulfate (a cyanide
antagonist) 20 minutes before and 80 and 180 minutes after i.p. injection of 45 mg/kg propionitrile. The mortality
rate for animals treated only with 45 mg/kg propionitrile was 9/10. Co-treatment with sodium nitrite reduced the
rate to 5/9. None of the 10 animals that were co-treated with sodium thiosulfate died.
(2) Two groups of 10 mice received either 0.2 mL of vegetable oil or 0.2 mL of 20% carbon tetrachloride (a
hepatotoxic dose) in vegetable oil subcutaneously, 24 hours before i.p. treatment with 45 mg/kg proponitrile. In
both experiments, animals were observed for 7 days. The mortality rate for animals treated only the 45 mg/kg
propionitrile was 8/10 whereas none of the animals co-treated with carbon tetrachloride died.
(3) Concentrations of cyanide in liver and brain were determined in (a) 5 mice treated only with 28 mg/kg-bw
propionitrile; (b) 5 mice given 1 g/kg-bw sodium thiosulfate before and after a dose of 28 mg/kg-bw propionitrile;
and (c) 5 mice given 0.2 mL of 20% carbon tetrachloride before i.p. treatment with 28 mg/kg-bw propionitrile. All
mice were killed 2.5 hours after dosing and propionitrile and cyanide concentrations were determined in the livers
and brains. Cyanide concentrations in liver and brain of mice treated with propionitrile alone were markedly greater
than mice co-treated with sodium thiosulfate or carbon tetrachloride.
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These additional studies indicate that propionitrile is activated by the liver to release cyanide, which is responsible
for the acute toxicity observed. Similar results were obtained from studies with butyronitrile.
Conclusion: Acute oral and dermal toxicity of alkyl nitriles category members is high. Acute toxicity via the
inhalation route is moderate. Repeated exposures to alkyl nitriles via inhalation and oral routes show high toxicity
to rats. Repeated inhalation exposures (0.14 mg/L/day) resulted in labored breathing, nasal discharge, salivation,
discharge from the eyes, hypoactivity and/or alopecia. At higher concentrations (0.27 and 0.48 mg/L/day,
respectively) ataxia, decreased weight gain, changes in organ weights (including testes), alterations in hematological
and clinical chemistry parameters and mortality at the highest dose. Repeated oral exposures (3.72 mg/kg-bw/day)
resulted in decreased food consumption and decreased weight gain. The decreased relative testes weight in the
repeated-exposure inhalation study was not correlated histopathologically. No effects were seen on reproductive
parameters in male and female fertility studies or on reproductive organs in the repeated-dose toxicity studies.
Developmental effects included increased number of early resorptions, post-implantation losses and decreased mean
fetal body weight. An increased incidence of unossified sternebrae was seen at 40 and 80 mg/kg-bw/day.
Butyronitrile and isobutyronitrile exposure via inhalation also resulted in increased pre-implantation losses and
decreased fetal body weights. The category members were not mutagenic in bacterial or mammalian cell assays and
did not induce chromosomal aberrations when tested in vitro or in vivo. Results of mechanistic studies indicate that
propionitrile and butyronitrile are activated by the liver to release cyanide, which is responsible for acute toxicity.
The potential health hazard of alkyl nitriles category members is high based on repeated-dose and developmental
toxicity.
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Tabic 3. Summary of Health Effects Data
End points
Propionitrile
(107-12-0)
Butvronitrile
(109-74-0)
Isobutvronitrile
(78-82-0)
Acute Oral Toxicity
LDS0 (mg/kg-bw)
40 - 270
50-111
50 - 100
Acute Dermal Toxicity
LDS0 (mg/kg-bw)
40-90
398
-239
Acute Inhalation Toxicity
LCS0 (mg/L)
-3.3
> - 3.4 (1 h)
> - 3.4 (1 h)
Repeated-Dose Toxicity
NOAEL/LOAEL
Oral (mg/kg-bw/day)
NOAEL = 1.34
LOAEL = 3.72
No Data
NOAEL - 1.34
LOAEL ~ 3.72
(RA)
No Data
NOAEL - 1.34
LOAEL-3.72
(RA)
Repeated-Dose Toxicity
NOAEL/LOAEL
Inhalation (mg/L/day)
NOAEL = Not established
LOAEL-0.135
No Data
NOAEL = Not established
LOAEL -0.135
(RA)
No Data
NOAEL = Not established
LOAEL-0.135
(RA)
Reproductive Toxicity
NOAEL/LOAEL
Inhalation (mg/L/day)
Systemic toxicity
Systemic toxicity
NOAEL -0.14
LOAEL - 0.27
No Data
NOAEL-0.14
LOAEL - 0.27
No Data
NOAEL -0.14
LOAEL - 0.27
Reproductive toxicity
Reproductive toxicity
NOAEL - 0.47
LOAEL > - 0.47
NO A F.I. - 0.47
LOAEL > - 0.47
(RA)
NO A F.I. - 0.47
LOAEL > - 0.47
(RA)
Developmental Toxicity
NOAEL/LOAEL
Oral (mg/kg-bw-day)
Maternal toxicity
Developmental Toxicity
Inhalation (mg/L/day)
Maternal toxicity
Developmental Toxicity
NOAEL = 40
LOAEL = 80
NOAEL = 20
LOAEL = 40
NOAEL -0.56
LOAEL > - 0.56
NOAEL - 0.42
LOAEL -0.56
NOAEL - 0.28
LOAEL -0.56
NOAEL - 0.28
LOAEL - 0.56
Genetic Toxicity -
Gene Mutation
In vitro
Negative
Negative
Negative
Genetic Toxicity -
Chromosomal Aberrations
In vitro
No Data
Negative
(RA)
Negative
Negative
Genetic Toxicity -
Chromosomal Aberrations
In vivo
Negative
No Data
Negative
(RA)
No Data
Negative
(RA)
Measured data in bold text; RA = Read Across
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4. Hazard Characterization
The log Kow values for the alkyl nitriles category members indicate that their potential to bioaccumulate is low. The
alkyl nitriles category members are readily biodegradable, indicating that they are not expected to persist in the
environment.
The evaluation of available toxicity data for fish, aquatic invertebrates and aquatic plants indicates that the potential
acute hazard of the alkyl nitriles category members to aquatic organisms is low.
Acute oral and dermal toxicity of alkyl nitriles category members is high. Acute toxicity via the inhalation route is
moderate. Repeated exposures to alkyl nitriles via inhalation and oral routes show high toxicity to rats. Repeated
inhalation exposures (0.14 mg/L/day) resulted in labored breathing, nasal discharge, salivation, discharge from the
eyes, hypoactivity and/or alopecia. At higher concentrations (0.27 and 0.48 mg/L/day, respectively) ataxia,
decreased weight gain, changes in organ weights (including testes), alterations in hematological and clinical
chemistry parameters and mortality at the highest dose. Repeated oral exposures (3.72 mg/kg-bw/day) resulted in
decreased food consumption and decreased weight gain. The decreased relative testes weight in the repeated-
exposure inhalation study was not correlated histopathologically. No effects were seen on reproductive parameters
in male and female fertility studies or on reproductive organs in the repeated-dose toxicity studies. Developmental
effects included increased number of early resorptions, post-implantation losses and decreased mean fetal body
weight. An increased incidence of unossified sternebrae was seen at 40 and 80 mg/kg-bw/day. Butyronitrile and
isobutyronitrile exposure via inhalation also resulted in increased pre-implantation losses and decreased fetal body
weights. The category members were not mutagenic in bacterial or mammalian cell assays and did not induce
chromosomal aberrations when tested in vitro or in vivo. Results of mechanistic studies indicate that propionitrile
and butyronitrile are activated by the liver to release cyanide, which is responsible for acute toxicity.
The potential health hazard of alkyl nitriles category members is high based on repeated-dose and developmental
toxicity.
5. Data Gaps
No data gaps are identified under the HPV Challenge Program.
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Appendix
Alkyl Nitrilcs
CAS No.
Chemical Name
Structure
SPONSORED CHEMICALS
107-12-0
Propionitrile
H2
h3c""%cn
C3H5N
109-74-0
Butyronitrile
H,
X. XN
u r* r%
n w w
h2
c4h7n
78-82-0
Isobutyronitrile
H,C
}C-CN
u r* H
n3u
c4h7n
17
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