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Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information
No other studies specifically investigating the reproductive effects of acetonitrile are available.
Link to relevant study records
Reference
Endpoint:
screening for reproductive / developmental toxicity
Remarks:
based on test type (migrated information)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 December 1998 - 28 December 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: OECD Guideline study under GLP conditions
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc.
- Age at study initiation: (P) x 8 weeks
- Weight at study initiation: (P) Males: 302 - 344 g; Females: 207 - 248 g
- Acclimation period: 2 weeks


Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
unchanged (no vehicle)
Details on exposure:
TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: up to 9 days
- Proof of pregnancy: vaginal plug or sperm in vaginal smear (day 0 of pregnancy)
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
male: 42 days
female: 35-41 days
Frequency of treatment:
6 hours daily
Remarks:
Doses / Concentrations:
0, 150, 300, 600, 1200 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0, 150.4, 300.3, 599.9, 1199.7 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
10 rats/sex/dose
Control animals:
yes, concurrent vehicle
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: weekly. Mated females: day 0, 7, 14 and 20 of pregnancy. Day 0 and 4 of postpartum. Scheduled sacrifice day.

FOOD CONSUMPTION: Yes
Oestrous cyclicity (parental animals):
From the start day of acclimation period until the day of successful copulation.
Sperm parameters (parental animals):
Parameters examined in male parental generations:
sperm count, sperm motility, sperm morphology in epididymis.
Litter observations:
PARAMETERS EXAMINED
The following parameters were examined in offspring:
number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight, physical or behavioural abnormalities


GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities; possible cause of death was determined for pups born or found dead.
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: All surviving animals at the scheduled sacrifice day in the combined general toxicity study.
- Maternal animals: All surviving animals on day 4 of postpartum.


GROSS NECROPSY
- Gross necropsy performed in the combined general toxicity study.


HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues examination performed in the combined general toxicity study.
Postmortem examinations (offspring):
SACRIFICE
- The F1 offspring on day 4 of postpartum was subjected to postmortem macroscopic examination.


GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.
Statistics:
chi-square test, Bartlett test, one-way analysis of variance, multiple analysis of Dunnett, Kruskal-Wallis rank test
Reproductive indices:
Gestational period, gestation rate, implantation index, delivery index, birth index, live birth index, sex ratio.
Offspring viability indices:
viability index=(number of pups alive on day 4/number of pups alive on day 0) × 100
Clinical signs:
effects observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Other effects:
not examined
Reproductive function: oestrous cycle:
effects observed, treatment-related
Reproductive function: sperm measures:
no effects observed
Reproductive performance:
effects observed, treatment-related
CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
See the part of repeated dose general toxicology. (7.5.3 Repeated dose toxicity: inhalation)

REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS)
Prolonged estrus stages were found in 3 females of the 1200 ppm group.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
Fertility rates decreased slightly in the 1200 ppm group without statistically significance.

ORGAN WEIGHTS (PARENTAL ANIMALS)
See the part of repeated dose general toxicology. (7.5.3 Repeated dose toxicity: inhalation)

GROSS PATHOLOGY (PARENTAL ANIMALS)
See the part of repeated dose general toxicology. (7.5.3 Repeated dose toxicity: inhalation)

HISTOPATHOLOGY (PARENTAL ANIMALS)
See the part of repeated dose general toxicology. (7.5.3 Repeated dose toxicity: inhalation)
Dose descriptor:
NOEC
Effect level:
600 ppm
Sex:
male/female
Basis for effect level:
other: In the 1200 ppm groups, fertility rate was slightly low , and estrous cycles changed in some animals. Mortality also occurred.
Clinical signs:
no effects observed
Mortality / viability:
no mortality observed
Body weight and weight changes:
no effects observed
Sexual maturation:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings:
not examined
Reproductive effects observed:
not specified
Executive summary:

The IPH of Japan (1980) has reported results of a guideline (OECD 422) and GLP reproduction /developmental toxicity screening test of acetonitrile in rats. Groups of 10 males and 10 females were exposed to acetonitrile vapor in whole-body inhalation chambers for 6 hours daily for 6 weeks (42 days) for males (from 2 weeks before mating until 2 weeks after the end of the mating period), and for 35 -41 days for females (from 2 weeks before mating until day 19 of pregnancy) at concentrations of 0, 150, 300, 600 or 1200 ppm. In the 1200 ppm group, the fertility rate was slightly lower than controls, and the changes of estrous cycles were found in some animals in the study. Mortality also occurred at the 1200 ppm exposure level. Based on these results the NOECs for systemic toxicity and reproductive toxicity were considered to be 600 ppm in both sexes.

Effect on fertility: via oral route
Endpoint conclusion:
no study available
Effect on fertility: via inhalation route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
1 008 mg/m³
Quality of whole database:
An OECD 422 screening study is supported by assessment of relevant parameters in the rat and mouse from chronic inhalation studies.
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

Screening study with acetonitrile

The IPH of Japan (1980) has reported results of a guideline (OECD 422) and GLP reproduction /developmental toxicity screening test of acetonitrile in rats. Groups of 10 males and 10 females were exposed to acetonitrile vapour in whole-body inhalation chambers for 6 hours daily for 6 weeks (42 days) for males (from 2 weeks before mating until 2 weeks after the end of the mating period), and for 35 -41 days for females (from 2 weeks before mating until day 19 of pregnancy) at concentrations of 0, 150, 300, 600 or 1200 ppm. In the 1200 ppm group, the fertility rate was slightly lower than controls, and the changes of estrous cycles were found in some animals in the study. Mortality also occurred at the 1200 ppm exposure level. Based on these results the NOECs for systemic toxicity and reproductive toxicity were considered to be 600 ppm in both sexes.

Supporting data from NTP bioassays

Morrissey et al. (1988), published an evaluation of rodent sperm, vaginal cytology and reproductive organ weight data from fifty US National Toxicology Program 13-week studies, including results from acetonitrile rat and mouse studies.  Male rats or mice exposed over 92 days to 0, 25, 50, 100, 200 or 400 ppm acetonitrile by inhalation showed no change in (absolute or relative) weight of the right cauda or right testis, and no effect on sperm motility. No data were provided on the effects of acetonitrile on the female reproductive system of rats or mice.

Two-generation study with acrylonitrile

No effects were seen on reproduction or reproductive organs, including mating, sperm quality, estrus cyclicity or histopathology in a guideline (OECD 416) and GLP 2 -generation reproduction study of acrylonitrile (a close structural analog of the submission substance acetonitrile) in rats (Nemec et al, 2008).

Nemec et al (2008) reported results of a guideline (OECD 416) and GLP study of acrylonitrile (a close structural analog of the candidate substance acetonitrile, although with a higher degree of systemic toxicity). Sprague-Dawley rats (25/sex/group) were exposed to vapor atmospheres via whole-body inhalation at concentrations of 0, 5, 15, 45 (two offspring generations) and 90 ppm (one offspring generation), 6 h daily, 1 litter/generation, through F2 weanlings on postnatal day 28. After approximately 3 weeks of direct exposure following weaning, exposure of the F1 animals at 90 ppm was terminated due to excessive systemic toxicity in the males. There were no exposure-related mortalities in adult animals, no functional effects on reproduction or effects on reproductive organs, and no evidence of cumulative toxicity or of enhanced toxicity in pregnant and lactating dams or in developing animals. Adult systemic toxicity was limited to body weight and/or food consumption deficits in both sexes and generations (greater in males) at 45 and 90 ppm and increased liver weights in the 90 ppm F0 males and females and 45 ppm F1 males. Neonatal toxicity was expressed by F1 offspring weight decrements at 90 ppm.

Based on the absence of reproductive toxicity reported in these studies, further testing of acetonitrile for reproductive toxicity is not scientifically justified.

 


Short description of key information:
An OECD 422 screening study is supported by assessment of relevant parameters in the rat and mouse from chronic inhalation studies with acetonitrile and a 2-generation study with the structrual analogue acrylonitrile.

Justification for selection of Effect on fertility via inhalation route:
Study performed with the submission substance.

Effects on developmental toxicity

Description of key information
Inhalation studies are available in the rabbit and rat; gavage studies are available in the rat and hamster.
Link to relevant study records

Referenceopen allclose all

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1983
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study
Qualifier:
according to
Guideline:
other: US EPA TSCA 48 FR 50942, November 4, 1983. Docket OPTS 42019A.
Qualifier:
according to
Guideline:
other: Environmental Protection Agency, Pesticide Programs, Proposed Guidelines for Registering-Pesticides in the U.S.; Hazard Evaluation: Humans and Domestic Animals, Federal Register, Tuesday, August 22, 1978. 43FR37336; for teratogenicity/reproductive effects
Qualifier:
equivalent or similar to
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes (incl. certificate)
Limit test:
no
Species:
rabbit
Strain:
New Zealand White
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Dutchland Laboratories, Inc. Swampbridge Road, Box 139A, Denver, PA
- Age at study initiation: 5 months old (actual age - 21 weeks)
- Weight at study initiation: 2.79 - 5.08 kg
- Housing: Individually assigned to housing based on computer-generated random numbers. Females were housed in vertical order according to dosage and insemination groups in one of eight individual stainless-steel cages (5 square feet of floor area with 16 inch height per individual cage). Because rabbits were scheduled to be terminated prior to natural delivery, nesting materials were not provided.
- Diet: Approxiamtely 180 g Certified Rabbit Chow® # 5322 (Ralston Purina), contained in an individual stainless-steel “J-type” feeder attached to each cage, were given to each rabbit each day.
- Water: Local water which had been passed through a reverse osmosis membrane was available ad libitum from individual glass bottles attached to each cage.
- Acclimation period: females acclimated for approximately four weeks.

ENVIRONMENTAL CONDITIONS
- Temperature: 62°F and 76°F
- Humidity: 35 - 80%
- Air changes: 12 - 15/hour
- Photoperiod: 12 hr light/dark cycle. Each dark cycle began at 1900 hours EST (2000 hours EDT).

IN-LIFE DATES: From: 17 July 1983 To: 19 August 1983
Route of administration:
oral: gavage
Vehicle:
other: deionized water
Details on exposure:
Acetonitrile was administered to female rabbits by stomach tube followed by approximately 5 mL of air to clear the tube.

PREPARATION OF DOSING SOLUTIONS: All dosages were administered to rabbits as aqueous solutions (R.O. water) at a volume of 5 mL/kg/day. The acetonitrile was assumed to contain 100% active ingredient for the purpose of calculating dosages and concentrations.

OTHER: The oral route was selected for use since it has been demonstrated that exposure via gavage and inhalation produce similar effects. The test agent was administered once each day, between 0856 and 1235 hours EDT (0956 and 1335 EST, respectively). Each daily dosage was administered as closely as practical to the same time each day, with all dosages administered to all rabbits approximately 3 to 6.5 hours after the beginning of the light period at 0700 hours EST.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The test chemical and test vehicle were analyzed for purity by gas-liquid chromatography prior to initiation of the main study. In addition, homogeneity analyses were performed on several concentrations, including the highest (160 mg/mL) concentration that was used in the preliminary studies and the lowest (0.02 mg/mL) concentration that was considered practical to administer in the main study. These same concentrations were determined to be stable at 24 and 72 hours and at 7 days after preparation. Analysis performed on the first day the test chemical was used demonstrated that the concentrations were correctly prepared and stable during the period of use.
Details on mating procedure:
- Impregnation procedure: Artificial insemination from five untreated proven males. A different buck was used each day of insemination. Twenty female rabbits were inseminated on each of five consecutive days. These female rabbits were intravenously administered 20 USP Units/kg of HCG approximately three hours prior to insemination with an estimated 0.25 mL of semen which had been diluted with normal saline to a concentrations of 6.0 x 10^6 spermatozoa/0.25 mL. Male rabbits were not administered the test agent.
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: Day of artificial insemination referred to as day 0 of presumed gestation.
Duration of treatment / exposure:
Days 6-18 of pregnancy
Frequency of treatment:
Once daily
Duration of test:
Day 29 of gestation
Remarks:
Doses / Concentrations:
0, 2.0, 15.0, 30.0 mg/kg bw/day
Basis:

No. of animals per sex per dose:
4 dose groups of 25 animals each.
Control animals:
yes, concurrent vehicle
Details on study design:
- Sex: female
- Dose selection rationale: Doses selected on the basis of two pilot studies.
- Rationale for animal assignment: Computer-generated (weight-ordered) randomization order was used to assign 100 female rabbits to the four dosage groups. These rabbits were in apparent good health and had body weights ranging from 3.03 to 5.27b kg each.
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: several times during pre-study period and on days 0 and 5 of presumed gestation. Observations for physical signs of agent effect, abortion and/or viability were made several times each day during the administration period (days 6 through 18 of presumed gestation) and daily during the post-administration period (days 19 through 29 of presumed gestation).

BODY WEIGHT: Yes
- Time schedule for examinations: More frequent than required. Weights were recorded the day after arrival, once weekly during acclimation period, on days 0 and 5 of presumed gestation and daily during administration and post-administration period.

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Food consumption was recorded to the nearest 25% of 180 g daily during acclimation. Observations for anorexia during study were recorded.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 29 with carbon dioxide was based on computerized random assignment which rotated throughout dosage groups.
-Organs examined: Lungs were examined, liver weights were recorded, and gross lesions considered appropriate were retained and preserved
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
- Gravid uterus weight: No, this parameter was considered extremely inaccurate due to variation in fluid loss resulting from necropsy procedures. More accurate data, consisting of frequent maternal weights and individual fetal weights, rather than a litter weight, were recorded.
Examinations included:
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Number of live and dead fetuses: Yes
Fetal examinations:
-Only body weights of live fetuses were used in determining fetal body weight averages for litters.
- Soft tissue examinations: Yes: all fetuses per litter. Only specimens observed to be grossly abnormal at soft tissue examination of fetuses were preserved. Dissected fetal tissue which had been determined to appear grossly normal was not considered necessary to preserve.
- Skeletal examinations: Yes: all fetuses were eviscerated, stained with alizarin red-S(6) and evaluated for skeletal alterations.
-Other: A transverse section was made of each unfixed fetal head, between the parietal and frontal bones, and the head then examined for the presence of internal hydrocephaly. As no viscera had grossly observed abnormalities, none was preserved.
Statistics:
Standard deviations were cited in tables only where appropriate. Maternal physical sign data and the incidence of pregnancy and abortion were analyzed using Fisher’s exact test.

The one-way analysis of variance was used to evaluate average body weights of rabbits assigned to the four dosage groups on days 0 and 5 of presumed gestation. Maternal body weight data for days 0, 6, 9, 12, 15, 19, 24 and 29 and maternal body weight change for days 0 to 6, 6 to 9, 9, to 12, 12 to 15, 15 to 19, 19 to 24, 24 to 29, 19 to 29, 6 to 19, 6 to 29 and 0 to 29 of pregnancy were analyzed using Bartlett’s test of homogeneity of variances and either the one-way analysis of variance or the Mann-Whitney U test. If Bartlett’s test was positive (P≤0.05), then the Mann-Whitney U test was used to analyze the data by testing each group individually against the control dosage group. If Bartlett’s test was negative (P≥0.05), then the one-way analysis of variance was used to analyze the data. If the F-ration was positive (P≤0.05), then Dunnett’s test was used to test each group individually against the control dosage group. The same statistical analyses were used to evaluate maternal absolute liver weight data. Data obtained during Caesarean-sectioning and for malformations and variations were evaluated using Jonckheere’s test with the population of affected fetuses per litter considered to be the basic experimental unit. If Jonckheere’s test was positive (P≤0.05), and if there were fewer than 75% ties in a group, then the Mann-Whitney U test was used to analyze the data by testing each group individually against the control dosage group. If Jonckheere’s test was positive (P≤0.05), and if there were more than 75% ties in a group, the Fisher’s exact test was used with fixed point censoring to evaluate the data.
Indices:
Average number of live fetuses, incidence of resorption, incidence of pregnancy, average number of corpora lutea, average number of implantations, average fetal body weight, sex ratios, average percentage of malformed fetuses per litter.
Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Five deaths and 2 abortions out of 25 rabbits, and reduced weight gain followed by a 'rebound phenomenon' (weight gain) during the 11 days post-treatment, occurred in the 30 mg/kg group. The 15 mg/kg/day group showed only the 'rebound phenomenon'. Upon necropsy, two of the five high dosage group rabbits which died had a stomach wall that appeared thin in the cardiac region. This finding was considered agent-related, since it was observed only in rabbits whose deaths were attributed to administration of acetonitrile. Necropsy of the middle dosage group rabbit which died revealed a spontaneous umbilical hernia and marked hemorrhage in the herniated portion of the intestine (strangulation). Average maternal body weight change was affected by administration of the middle and high dosages of acetonitrile, as compared with the vehicle. Average maternal body weight gain was decreased for high dosage group rabbits on days 6 to 19 of gestation; the decrease was significant (P 0.05). As compared with control values, the increase in average maternal body weight which was observed for the middle and high dosage group rabbits after agent administration was stopped represented a rebound effect.
Dose descriptor:
NOAEL
Effect level:
15 mg/kg bw/day (actual dose received)
Basis for effect level:
other: maternal toxicity
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
A significant decrease in the average number of live foetuses/litter and a slight (non-significant) increase in resorptions were seen in the 30 mg/kg group. Acetonitrile did not adversely affect the incidence of pregnancy or the average number of corpora lutea, implantations, average foetal body weight and sex ration. There were no treatment related gross external, soft tissue or skeletal malformations or developmental variations.
Dose descriptor:
NOAEL
Effect level:
15 mg/kg bw/day (actual dose received)
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEL
Effect level:
30 mg/kg bw/day (actual dose received)
Basis for effect level:
other: teratogenicity
Abnormalities:
not specified
Developmental effects observed:
not specified

One 15.0 mg/kg/day dosage group rabbit died on day 23 of gestation. At necropsy, this rabbit had an umbilical hernia which had increased in size during gestation and resulted in intestinal strangulation. This death was not considered agent-related.

Conclusions:
Administration of aqueous solutions of acetonitrile to pregnant rabbits at dosages of 2.0, 15.0 and 30.0 mg/kg/day on days 6 through 18 of gestation was not a unique hazard to the conceptus. Embryo/fetal lethality was observed only at a maternally lethal dosage. Administration of these dosages to the dams was not demonstrated to adversely affect the surviving fetuses, that is, it did not result in retarded fetal growth or an increased incidence in grossly observed external, soft tissue or skeletal malformations among the fetuses.
Executive summary:

In a guideline (US EPA) and GLP study conducted by Argus Research Labs (1984), oral (gavage) administration of aqueous solutions of Acetonitrile (HPLV grade) to pregnant rabbits at dosages of 2.0, 15.0 and 30.0 mg/kg/day on days 6 through 18 of gestation was not a unique hazard to the conceptus. Embryo/fetal lethality was observed only at a maternally lethal dosage. Administration of these dosages to the dams was not demonstrated to adversely affect the surviving fetuses, that is, it did not result in retarded fetal growth or an increased incidence in grossly observed external, soft tissue or skeletal malformations among the fetuses. Based on these findings, the following NOAELs are established for acetonitrile in the pregnant rabbit:

Maternal toxicity - 15 mg/kg/day

Fetotoxicity - 15 mg/kg/day

Teratogenicity - 30 mg/kg/day

Gastrointestinal symptoms observed in the rabbits that died are considered to be a significant confounder in determining the contribution from systemic chemical toxicity in this study.

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: US National Toxicology Program
GLP compliance:
not specified
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Details on mating procedure:
- Proof of pregnancy: The day of sperm detection was designated as gestation day 0.
Duration of treatment / exposure:
6 hours per day on gestation days 6-19
Remarks:
Doses / Concentrations:
0, 100, 400, or 1200 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
Each of the four treatment groups consisted of 10 non-pregnant females (for comparison), 10 positively mated females for a distribution study evaluating maternal blood for acetonitrile and cyanide, and ~33 positively mated females for evaluating developmental toxicity.
Control animals:
yes, sham-exposed
Maternal examinations:
BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were obtained throughout the study period

Ovaries and uterine content:
Uterine weights were obtained on gestation day 20. Implants were enumerated and their status recorded.
Fetal examinations:
Fetal body weights were obtained on gestation day 20. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects.
Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Exposure of rats to these concentrations of acetonitrile resulted in mortality in the 1200 ppm group (2/33 pregnant females; 1/10 non-pregnant females), and the 400 ppm group (1/33 pregnant females). However, there were no treatment-related effects upon body weights or reproduction indices at any exposure level. Other clinical signs were only noted at 1200 ppm - hypoactivity, 14/33; emaciated, 6/33; dyspnea, 1/33; abnormal posture, 2/33; bloody vaginal discharge, 1/33).
Dose descriptor:
NOAEC
Effect level:
100 ppm (nominal)
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
>= 1 200 ppm (nominal)
Basis for effect level:
other: developmental toxicity
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
Exposure had no effect upon the number of implants per dam, litter size, resorptions, fetal weight or fetal sex ratio. There were no significant increases in the incidence of fetal malformations or variations. There was an increase in the incidence of supranumary ribs at 100 ppm, but the incidence decreased at higher concentrations (2.6%, 9.0, 6.5% & 4.4% at 0ppm, 100ppm, 400ppm and 1200ppm respectively).
Abnormalities:
not specified
Developmental effects observed:
not specified

Determination of acetonitrile and cyanide concentrations in maternal rat blood showed that acetonitrile concentration in the blood increased with exposure concentration for all exposed maternal rats. Detectable amounts of cyanide in the blood were found only in the rats exposed to 1200 acetonitrile (~2 micrograms of cyanide per gram of blood).

Conclusions:
The two highest exposure concentrations were maternally lethal to some rats. However, there were no treatment-related effects upon body weights or reproduction indices at any exposure level, nor was there a significant increase in the incidence of fetal malformations or variations.
Executive summary:

The US National Toxicology Program studied the effects of inhaled Acetonitrile vapor on pregnant rats exposed to concentrations of 100, 400 or 1200 ppm 6 hours per day on days 6 through 19 of gestation. The two highest exposure concentrations were maternally lethal to some rats. However, there were no treatment-related effects upon body weights or reproduction indices at any exposure level, nor was there a significant increase in the incidence of fetal malformations or variations. Based on these findings, the following NOAECs are established for acetonitrile in the pregnant rat:

Maternal toxicity - 100 ppm (168 mg/m3)

Developmental toxicity >= 1200 ppm (2015 mg/m3)

Effect on developmental toxicity: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
15 mg/kg bw/day
Study duration:
subacute
Species:
rabbit
Quality of whole database:
A guideline-compliant and GLP study is avaialable in the rabbit and is supported by a published study in the rat.
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
2 519 mg/m³
Study duration:
subacute
Species:
rat
Quality of whole database:
A high quality NTP study in the rat is supported by published studies in the rat and hamster
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available
Additional information

Developmental studies of acetonitrile by the oral, inhalation and intrperitoneal routes are available in animals. In a study by the US NTP, rats exposed by inhalation to acetonitrile did not result in significant foetal effects, even at concentrations which were overtly toxic to the dam. In this study a maternal NOAEC of 100 ppm and a NOAEC of 1200 ppm with respect to developmental toxicity were established. In another inhalation developmental toxicity study in Sprague-Dawley rats by Saillenfait et al (1993), a NOAEC of 1200 ppm was reported for maternal toxicity and a NOAEC of 1500 ppm for developmental toxicity. The reason for the large difference in maternal toxicity NOAECs in these two studies is not clear.  Other subchronic inhalation studies of non-pregnant rats have reported mortality at 800 ppm. In two studies with pregnant rats that received acetonitrile by gavage no foetal abnormalities were reported (Johannsen et al, 1986; Smith et al, 1987). Developmental NOAELs in these studies were 190 mg/kg bw/d and 500 mg/kg bw/d, respectively.

 

In a rabbit study conducted in compliance with FDA GLP, animals administered 2, 15 or 30 mg/kg bw/d acetonitrile orally showed maternal mortality at 30 mg/kg bw/d. At 15 mg/kg bw/d there was a rebound effect on body weight gain after completion of the administration period. Embryotoxicity was observed only at the 30 mg/kg dose level. There were no treatment-related gross external, soft tissue or skeletal malformations or developmental variations (Argus Research Labs, 1984). Gastrointestinal symptoms observed in the rabbits that died are considered to be a significant confounder in determining the contribution from systemic chemical toxicity in this study. Based on the sensitivity of the rabbit to gastrointestinal effects, the rat data are considered to be more relevant for purposes of evaluating the systemic developmental effects of acetonitrile.

 

Exposure of hamsters to maternally lethal levels of 5000 or 8000 ppm acetonitrile on Day 8 of gestation was shown to increase the incidences of resorptions and malformations including exencephaly, encephalocele and rib fusions. Malformations identical to those noted following inhalation exposure occurred sporadically in a limited number of offspring after oral or intraperitoneal administration of 100- 400 mg/kg acetonitrile, which also produced mortality in the dams (Willhite, 1983).

 

In summary, reliable rat studies by inhalation and gavage, and a rabbit study by gavage have shown foetotoxicity only at maternally toxic doses and have produced no evidence of teratogenicity. NOAECS for maternal toxicity in the rat inhalation studies range from 100 ppm to 1200 ppm (168 - 2015 mg/m3). NOAELs for maternal toxicity in the gavage studies range from 15 mg/kg (rabbit) to 190 mg/kg (rat). Skeletal malformations have been reported in hamsters at higher, maternally lethal, doses.


Justification for selection of Effect on developmental toxicity: via oral route:
Study in the most sensitive species

Justification for selection of Effect on developmental toxicity: via inhalation route:
Most reliable study

Justification for classification or non-classification

No classification is proposed for reproductive toxicity based upon the absence of reproductive effects in reliable animal studies. No reproductive or developmental effects were seen below maternally lethal doses in the following reliable animal studies: reproductive/developmental toxicity screening (rat, inhalation); organ histopathology and sperm motility (chronic rat and mouse, inhalation); developmental (rat, inhalation and gavage; rabbit, gavage); 2 -generation reproduction (rat, inhalation) or structural analog acrylonitrile.