2,2'-dimethyl-2,2'-azodipropiononitrile

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

A GLP-compliant oral toxicity study was performed in SD (Crj:CD) rats by an OECD combined repeated dose and reproductive / developmental toxicity screening test (OECD Guideline 422). The test substance was administered by gavage at doses of 2, 10 and 50 mg/kg bw/day for 45 days to males and from 14 days before mating to day 3 of lactation to females. The substance showed no adverse effects on copulation, fertility, duration of pregnancy, gestation index and parturition in all treated groups. At 50 mg/kg bw/day (12 dams), three dams showed difficulty of nursing and two of them let all their offsprings die within the first 4 days after birth. Although the substance showed no adverse effects on viability, sex ratio and body weight of newborns at birth, viability an body weight of nurslings on postnatal day 4 at 50 mg/kg bw/day were lower than the control levels. These changes were considered to be caused by maternal toxicity. There were no morphological abnormalities in pups in all treated groups. Therefore, the NOAEL for reproductive toxicity was considered to be 50 mg/kg bw/day.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

other information

Study period:

1997

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on mating procedure:

- premating exposure period: 14 days

Duration of treatment / exposure:

male: from 14 days before mating to 14 days after mating; males were exposed for 42 days
female: from 14 days before mating to day 3 of lactation

Frequency of treatment:

daily

Dose / conc.:

2 mg/kg bw/day (nominal)

Dose / conc.:

10 mg/kg bw/day (nominal)

Dose / conc.:

50 mg/kg bw/day (nominal)

No. of animals per sex per dose:

13

Control animals:

yes, concurrent vehicle

Parental animals: Observations and examinations:

BODY WEIGHT: Yes
- Time schedule for examinations: twice a week the first week; weekly afterwards, including during the pregnancy of females. Additionally for females, days 0 and 4 of lactation.

FOOD CONSUMPTION AND COMPOUND INTAKE
- Food consumption determined in four day blocks during the first week and weekly afterwards.
- Compound intake calculated in mean diet as g food/rat/average over the period of calcul.

Sperm parameters (parental animals):

Parameters examined in all male parental generations: testis weight, epididymis weight

Litter observations:

STANDARDISATION OF LITTERS
no

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
number and sex of pups, live births, postnatal mortality (on day 4), body weight recorded on day 0 and day 4.

GROSS EXAMINATION OF DEAD PUPS
yes, morphological

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals on day 43.
- Maternal animals: All surviving animals on day 4 post partum.

HISTOPATHOLOGY / ORGAN WEIGHTS
The following tissues were prepared for microscopic examination: Heart, thymus, spleen and liver, kidney, adrenal gland, testis, epididymis. These ones were also weighed.

Postmortem examinations (offspring):

SACRIFICE
- Supposed on day 4. Not accurately indicated.

GROSS NECROPSY
- Gross necropsy consisted of external examinations

Reproductive indices:

Copulation index, fertility index, gestation index, duration of pregnancy

Offspring viability indices:

viability index

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Males: Temporary salivation after each administration was observed in the animals exposed at 10 mg/kg and more.
Females: One female in the 50 mg/kg group died on post-partum day 3.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Males: Suppression of body weight gain and food consumption during the early administration period were noted in the 50 mg/kg group.
Females: Slight decrease in body weight gain and food consumption during the early administration period were observed in the animals exposed at 10 mg/kg and more.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Males: Increased eosinophilic bodies and basophilic changes of the renal tubular epithelial cells in the kidneys of all the animals exposed were noted, as well as granular casts in the lower nephrons. Centrilobular hypertrophy of hepatocytes was also detected in the groups of animals exposed at 10 mg/kg and more.
Females: Centrilobular hypertrophy of hepatocytes was observed in the groups of animals exposed at 10 mg/kg and more.

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

The compound showed no adverse effects on copulation and fertility, duration of pregnancy, gestation index and parturition at any of the dose levels tested. Three dams in the 50 mg/kg group showed abnormal lactation.

There were no adverse effects of 2,2'-azobis(2- methylpropanitrile) on copulation and fertility, duration of pregnancy, gestation index and parturition at all treated group. Three of 12 dams at 50 mg/kg showed the difficulty of nursling and two of them let all their offsprings die within the first 4 days after birth.

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No effect on reproductive toxicity in males

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: At 50 mg/kg bw/d, abnormal lactation in 3 dams

Critical effects observed:

no

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Gross pathological findings:

no effects observed

This compound showed no adverse effects on viability, sex ratio and body weight gain of pups. However, viability of newborns at birth and body weight of nurslings on postnatal day 4 was lower than the control levels at 50 mg/kg/day. These changes were considered to be caused by maternal toxicity. There were no morphological abnormalities in pups at all treated groups.
For reproductive and developmental toxicity the NOEL was 10 mg/kg in pups according to the authors.
It was considered that the effects on pups were caused by maternal toxicity since a difficulty in nursing (lactation) was reported. Then the NOAEL for reproduction in offspring was considered to be 50 mg/kg.

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

10 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: decreased viability index and body weight on day 4 at 50 mg/kg/day

Reproductive effects observed:

not specified

General parenteral toxicity:

There were no adverse effects of 2,2'-azobis(2- methylpropanitrile) on copulation and fertility, duration of pregnancy, gestation index and parturition at all treated group. Three of 12 dams at 50 mg/kg showed the difficulty of nursling and two of them let all their offsprings die within the first 4 days after birth.

Toxicity to offspring:

This compound showed no adverse effects on viability, sex ratio and body weight gain of pups. However, viability of newborns at birth and body weight of nurslings on postnatal day 4 was lower than the control levels at 50 mg/kg/day. These changes were considered to be caused by maternal toxicity. There were no morphological abnormalities in pups at all treated groups.

Table 1: Summary of development of pups

Dose (mg/kg)	0	2	10	50
Number of pregnant females	12	12	11	12
Number of pregnant females with pup alive	12	12	11	12
Gestation Index	100	100	100	100
Gestation length in days	22.3 +/-0.5 (12)	22.1 +/-0.3 (12)	22.2 +/-0.4 (11)	22.4 +/-0.5 (12)
Number of corpora lutea	18.8 +/-2.5 (12)	17.8 +/-1.5 (12)	18.1 +/-2.0 (11)	16.9 +/-2.0 (12)
Number of implantation sites	17.3 +/-25 (12)	16.8 +/-1.5 (12)	17.1 +/-2.1 (11)	15.6 +/-1.4 (12)
Implantation index	92.9 +/-10.6 (12)	95.0 +/-5.7 (12)	94.7 +/-7.7 (11)	92.8 +/-9.3 (12)
Day 0 of lactation
Number of pups born	15.4 +/-2.5 (12)	15.8 +/-1.9 (12)	15.5 +/- 1.8 (11)	14.8 +/-1.5 (12)
Delivery index	88.8 +/-6.2 (12)	94.0 +/-6.1 (12)	91.6 +/-10.3 (11)	94.6 +/-4.4 (12)
Number of pups alive	15.0 +/-2.5 (12)	15.8 +/-1.9 (12)	15.5 +/-1.8 (11)	14.8 +/-1.5 (12)
Birth index	86.6 +/- 8.3 (12)	93.5 +/- 5.8 (12)	91.6 +/-10.3 (11)	94.6 +/-4.4 (12)
Live birth index	97.4 +/-4.9 (12)	99.4 +/- 1.9 (12)	100.0 +/-0.0 (11)	100.0 +/- 0.0 (12)
Pup weight in grams
Male	6.2 +/-0.6 (12)	6.3 +/-0.5 (12)	6.3 +/-0.4 (11)	6.1 +/-0.2 (12)
Female	5.9 +/-0.5 (12)	6.0 +/-0.5 (12)	6.0 +/-0.3 (11)	5.9 +/-0.2 (12)
Sex ratio	50.5 +/-9.9 (12)	43.9 +/-12.8(12)	54.4 +/-10.9 (11)	53.6 +/-11.7 (12)
Day 4 of lactation
Number of pups alive	14.6 +/-2.3 (12)	15.6 +/-1.9 (12)	15.5 +/-1.8 (11)	11.6 +/-5.9 (12)
Viability index	97.5 +/-4.1 (12)	99.0 +/-2.4 (12)	100.0 +/-0.0 (11)	77.9 +/-38 (12)
Pup weight in grams
Male	9.8 +/-1.4 (12)	9.8 +/-1.1 (12)	9.8 +/-1.0 (11)	9.0 +/-1.2 (12)
Female	9.5 +/-1.2 (12)	9.5 +/-1.1 (12)	9.4 +/-1.0 (11)	8.5 +/-1.1 (12)

Gestation Index: Number of pregnant female with pups alive/Number of pregnant females

Implantation Index: Number of implantation sites/Number of corpora lutea *100 (%)

Delivery Index: Number of pups born/Number of implantation sites *100 (%)

Birth Index: Number of pups alive on day 0/ Number of implantation sites *100 (%)

Live Birth Index: Number of pups alive on day 0/ Number of pups born *100 (%)

Sex ratio: Number of male pups alive on day 0/ Number of pups alive on day 0 *100 (%)

Viability index: Number of pups alive on day 4/ Number of pups alive on day 0 *100 (%)

Conclusions:

In conclusion, the NOEL for reproductive and developmental toxicity was 50 mg/kg/day in males and 10 mg/kg/day in females and in pups. According to CLP criteria, the test substance is not classified.

Executive summary:

The reproductive / developmental toxicity of the test substance was evaluated in male and female rats after oral administration (gavage) at doses of 0, 2, 10 and 50 mg/kg/day until day 43 for males and day 4 of post partum for females.

The test substance had no effects on the copulation index or fertility index at 50 mg/kg or lower doses. The test substance did not affect the length of gestation period or delivery index in maternal animals, either. No abnormal parturition was observed. Abnormal nursing behavior was noted in 3 animals from the 50 mg/kg group.

The findings in offspring showed no effects on the parturition index, live pup delivery index, overall delivery index, or the sex ratio and body weight on day 0 at all dose-levels. In the 50 mg/kg group, the offspring viability index and body weight on day 4 of lactation showed a tendency to decrease. No offspring from the test substance treated groups showed any morphological anomaly.

Based on these results, the NOEL for reproductive and developmental toxicity was 50 mg/kg/day in males and 10 mg/kg/day in females and in pups.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

50 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

The reproductive / developmental toxicity of the test substance was evaluated in male and female rats after oral administration (gavage) at doses of 0, 2, 10 and 50 mg/kg/day until day 43 for males and day 4 of post partum for females.

The test substance had no effects on the copulation index or fertility index at 50 mg/kg or lower doses. The test substance did not affect the length of gestation period or delivery index in maternal animals, either. No abnormal parturition was observed. Abnormal nursing behavior was noted in 3 animals from the 50 mg/kg group.

The findings in offspring showed no effects on the parturition index, live pup delivery index, overall delivery index, or the sex ratio and body weight on day 0 at all dose-levels. In the 50 mg/kg group, the offspring viability index and body weight on day 4 of lactation showed a tendency to decrease. No offspring from the test substance treated groups showed any morphological anomaly.

Based on these results, the NOEL for reproductive and developmental toxicity was 50 mg/kg/day in males and 10 mg/kg/day in females and in pups.

Effects on developmental toxicity

Description of key information

A GLP-compliant oral toxicity study was performed in SD (Crj:CD) rats by an OECD combined repeated dose and reproductive / developmental toxicity screening test (OECD Guideline 422). The test substance was administered by gavage at doses of 2, 10 and 50 mg/kg bw/day for 45 days to males and from 14 days before mating to day 3 of lactation to females. The substance showed no adverse effects on copulation, fertility, duration of pregnancy, gestation index and parturition in all treated groups. At 50 mg/kg bw/day (12 dams), three dams showed difficulty of nursing and two of them let all their offsprings die within the first 4 days after birth. Although the substance showed no adverse effects on viability, sex ratio and body weight of newborns at birth, viability an body weight of nurslings on postnatal day 4 at 50 mg/kg bw/day were lower than the control levels. These changes were considered to be caused by maternal toxicity. There were no morphological abnormalities in pups in all treated groups. Therefore, the NOAEL for reproductive toxicity was considered to be 50 mg/kg bw/day and the NOAEL for developmental toxicity was considered to be 10 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

10 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

The reproductive / developmental toxicity of the test substance was evaluated in male and female rats after oral administration (gavage) at doses of 0, 2, 10 and 50 mg/kg/day until day 43 for males and day 4 of post partum for females.

The test substance had no effects on the copulation index or fertility index at 50 mg/kg or lower doses. The test substance did not affect the length of gestation period or delivery index in maternal animals, either. No abnormal parturition was observed. Abnormal nursing behavior was noted in 3 animals from the 50 mg/kg group.

The findings in offspring showed no effects on the parturition index, live pup delivery index, overall delivery index, or the sex ratio and body weight on day 0 at all dose-levels. In the 50 mg/kg group, the offspring viability index and body weight on day 4 of lactation showed a tendency to decrease. No offspring from the test substance treated groups showed any morphological anomaly.

Based on these results, the NOEL for reproductive and developmental toxicity was 50 mg/kg/day in males and 10 mg/kg/day in females and in pups.

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The available reproductive / developmental screening study is reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for fertility or developmental toxicity under Regulation (EC) No. 1272/2008, as amended for the tenth time in Regulation (EC) No. 2017/776.