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Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information

The rat (three generation study) NOAEL was considered to be between 80 - 750 ppm (<50 mg/kg/bw/day).

 

Link to relevant study records
Reference
Endpoint:
three-generation reproductive toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1977-05-22 to 1979-07-30
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-guideline study, pre-GLP 1979 study, limitations in design and/or reporting but otherwise adequate for assessment
Reason / purpose for cross-reference:
reference to same study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)
Deviations:
yes
Remarks:
There were only 2 dietary concentrations tested
Principles of method if other than guideline:
n/a
GLP compliance:
no
Remarks:
study report is dated July 1979, pre-GLP
Limit test:
no
Justification for study design:
n/a
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: MC/B (2909 Highland Avenue, Norwood, Ohio 45212); Catalog No. TX 310
- Expiration date of the lot/batch: Not specified
- Purity test date: Analysis of DCPD was performed with a UC-W98 column post receipt on August 18, 1976. (Purity: 98 to 99%)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Closed container in the freezer
- Stability under test conditions: Stability analysis revealed that in the closed containers, the concentration dropped 27.6% for the 80 ppm level and 30.8% for the 750 ppm level over a 10-day period.
- Solubility and stability of the test substance in the solvent/vehicle: Because of poor water solubility, DCPD was prepared for administration to animals by dissolving it in corn oil (Mazola).

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: waxy solid converted to an easily measured liquid by slight warming

FORM AS APPLIED IN THE TEST (if different from that of starting material) : waxy solid converted to an easily measured liqud by slight warming

Species:
rat
Strain:
Sprague-Dawley
Details on species / strain selection:
CRL:COB (SD) BR
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. (Portage, Michigan, USA)
- Females (if applicable) nulliparous and non-pregnant: [yes/no]
- Age at study initiation: (P) - Weanling albino rats
- Weight at study initiation: Not specified
- Fasting period before study: Not specified
- Housing: housed individually (except when mating) in shoe box cages on AB-SORB-DRI bedding
- Use of restrainers for preventing ingestion (if dermal): yes/no
- Diet (e.g. ad libitum): Purina Laboratory Chow meal provided ad libitum
- Water (e.g. ad libitum): water provided ad libitum
- Acclimation period: Acclimated to laboratory conditions for 11 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Not specified
- Humidity (%): Not specified
- Air changes (per hr): Not specified
- Photoperiod (hrs dark / hrs light): Not specified

IN-LIFE DATES: From: 1977-05-22 To: Not specified
Route of administration:
oral: feed
Remarks on MMAD:
n/a
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Rate of preparation of diet (frequency): Fresh diets were prepared weekly
- Mixing appropriate amounts with (Type of food): Diets prepared by adding the appropriate quantity of DCPD, dissolved in 300 mL of corn oil, to 10 Kg of Purina Laboratory Chow meal, and mixing for at least 15 minutes in a twin shell blender. Control diet was mixed with corn oil in the same fashion.
- Storage temperature of food: Stored at ambient conditions

VEHICLE
- Justification for use and choice of vehicle (if other than water): Because of poor water solubility, DCPD was prepared for administration to animals by dissolving it in corn oil (Mazola). The handling of DCPD itself was facilitated by slight warming, which converted the waxy solid to an easily measured liquid.
- Concentration in vehicle: at concentrations appropriate to the various studies
Details on mating procedure:
- M/F ratio per cage: Each male caged with two females of its dose group
- Length of cohabitation: 2 weeks
- Proof of pregnancy: Not specified
- Further matings after two unsuccessful attempts: Not specified
- After successful mating each pregnant female was caged (how): rats were returned to their respective cages and the females were allowed to litter
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Because of the possible loss from the diet through volatility of DCPD, samples of each week's dietary batch were analyzed by the LBI Chemistry Department. The analytical method employed gas-liquid chromatography and was supplied by the sponsor and developed at LBI.
Duration of treatment / exposure:
For 7 weeks prior to mating of the F0 parents through to study termination.
Frequency of treatment:
Continuous in diet
Details on study schedule:
- F0 rats were mated seven weeks after initiation of treated diet. One week after weaning the first litters (F1a pups), the F0 parents were remated, each male with a different pair of females from that of the first mating. One week after weaning the second litters (F1b pups), parent F0 rats were killed.
- Selected F1b pups were designated F1 parents and were approx. 100 days old when mated to produce the F2a litters and subsequently the F2b litters. Selected F2b pups were designated F2 parents and similarly used to produce the F3 a and b litters.
Dose / conc.:
0 ppm
Remarks:
Basis: nominal in diet
Group 1 (Control)
Dose / conc.:
80 ppm
Remarks:
Basis: nominal in diet
69.3 ppm (analytical concentration)
Group 2
Dose / conc.:
750 ppm
Remarks:
Basis: nominal in diet
693 ppm (analytical concentration)
Group 3
No. of animals per sex per dose:
10 males, 20 females
Control animals:
yes, plain diet
Details on study design:
Dose selection rationale:
A clear rationale for selection of the doses that were used in the study is not provided in the study report. However, in a rat teratology study with DCPD conducted by the same laboratory in 1977 (LBI Project number 10734-05), the study report mentions that the dose levels used in the study were approved by Dr. E. Ross Hart of LBI based on previous studies.

Rationale for animal assignment (if not random):
Rats were assigned randomly to the study groups
Positive control:
n/a
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily observations were made of parent rats for mortality and general condition

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: At 4 and at 8-9 weeks, and shortly before each mating, parent rats were weighed

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes; At 4 and at 8-9 weeks, and shortly before each mating, the food consumption of parent rats was estimated
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data
Oestrous cyclicity (parental animals):
No
Sperm parameters (parental animals):
No
Litter observations:
STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- At Day 4 each litter was reduced to eight total pups, four per sex if possible

PARAMETERS EXAMINED
The following parameters were examined in [F1 / F2 / F3] offspring:
- Gross abnormalities of pups
- Numbers of live and dead pups, and their mean body weight by sex at birth
- Number per sex Day 4 of lactation
- Number per sex and body weights Day 21 of lactation (weaning)

GROSS EXAMINATION OF DEAD PUPS: Yes; At weaning, gross necropsies were performed on approximately one-third of the first litters from all three generations, and on one-third of the F3b litters.

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY: No

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY: No
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: All surviving animals (A gross necropsy was performed on each Parent F0 animal one week after weaning the second litters (F1b pups).
- Maternal animals: All surviving animals (A gross necropsy was performed on each Parent F0 animal one week after weaning the second litters (F1b pups).

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

HISTOPATHOLOGY / ORGAN WEIGHTS
No data
Postmortem examinations (offspring):
At weaning, gross necropsies were performed on approximately one-third of the first litters from all three generations, and on one-third of the F3b litters.
Statistics:
Student's t-test; Chi-square test
Reproductive indices:
Male and female fertility; gestation index.
Offspring viability indices:
Newborn viability; pup viability (Days 0-4); lactation viability (days 4-21); sex ratio Day 0; Live pups per litter
Clinical signs:
no effects observed
Description (incidence and severity):
Data for compound-treated groups were entirely comparable to control figures at each interval.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One F0 female (No. 5196, 80 ppm) was found dead at Week 28, but all other F0 rats survived their portion of the study in generally good condition. Data for compound-treated groups were entirely comparable to control figures at each interval.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
F0 parents - Data for compound-treated groups were entirely comparable to control figures at each interval.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
F0 - Data for compound-treated groups were entirely comparable to control figures at each interval.
Food efficiency:
not specified
Description (incidence and severity):
n/a
Water consumption and compound intake (if drinking water study):
not specified
Description (incidence and severity):
n/a
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
no effects observed
Description (incidence and severity):
Reproductive and litter indices were unaffected by exposure to DCPD (Tables 3 and 4).
n/a
Key result
Dose descriptor:
NOAEL
Remarks:
F0 Parents
Effect level:
750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Systemic Toxicity
Key result
Critical effects observed:
no
Clinical signs:
no effects observed
Description (incidence and severity):
F1b Parents - No clinical signs reported.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Description (incidence):
F1b Parents - No mortality observed.
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
F1b Parents - At all intervals, rats in the compound-treated groups weighed as much as or more than the controls, except for the 80-ppm females at 20 weeks (just prior to the second mating). In this instance, the slightly lower mean body weight was not statistically significant.

F2b Parents - No meaningful differences between groups at the various intervals were seen with respect to body weight.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
F1b Parents - food consumption means were comparable among the groups, except that in both males and females of the 750-ppm group, the reductions at 20 weeks in food intake were statistically significant (p<0.05, Student's t-test).

F2b Parents - No meaningful differences between groups at the various intervals were seen with respect to food consumption.
Food efficiency:
not specified
Description (incidence and severity):
n/a
Water consumption and compound intake (if drinking water study):
not specified
Description (incidence and severity):
n/a
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Description (incidence and severity):
F1b Parents - At necropsy, no gross lesions were found in the F1b parent rats.

F2b Parents - Necropsy findings of the F2b parents were unexceptional.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Details on results:
n/a
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
effects observed, non-treatment-related
Description (incidence and severity):
F1b Parents - In the first mating to produce the F2a generation, except for reduced female fertility in the 750-ppm group, litter data in all groups were comparable.
However, the 70% figure (Table 5) for the F2a was not statistically significantly different (Chisquare test) from the control index (95%). In addition, it may be noted that male No. 7349 in the 750-ppm group failed to sire a litter in either mating, and could thus be responsible for the lack of litters from two of six non-productive females at the first mating. It was therefore concluded that the apparently lowered fertility of the high-dose females at the first mating was not related to compound administration.

In the second mating to produce the F2b generation, fertility in the 750-ppm females was reduced. However, the 85% figure (Table 6) for the F2b's was not statistically significantly different (Chisquare test) from the control index (95%). In addition, it may be noted that male No. 7349 in the 750-ppm group failed to sire a litter in either mating, and could thus be responsible for the lack of litters from two of three non-productive females at the second mating. It was therefore concluded that the apparently lowered fertility of the high-dose females at the second mating is not related to compound administration.

F2b Parents - Although female fertility was only 80% and 83% in the DCPD-treated groups, control fertility was worse, only 65%. There was nothing in these records to suggest a compound-related effect.
n/a
Key result
Dose descriptor:
NOAEL
Remarks:
F1b Parents
Effect level:
80 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Systemic Toxicity
Key result
Dose descriptor:
NOAEL
Remarks:
F2b Parents
Effect level:
750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Systemic toxicity
Key result
Critical effects observed:
no
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
There was nothing in the data to distinguish DCPD-treated groups (F1a) from control rats. Observations of the pups did not indicate anything of importance in the three groups. One F1a pup in a 80-ppm litter had an opaque left eye, and one F1a pup in a 750-ppm litter had a crooked tail. Such isolated findings were not considered to be meaningful.

All F1b generation groups were comparable to one another with respect to both litter data and pup observations. A single instance of a pup in the 80-ppm group with an abnormality (a deformed hind foot) was not considered to be meaningful.
Dermal irritation (if dermal study):
not examined
Mortality / viability:
mortality observed, non-treatment-related
Description (incidence and severity):
No mortality observed in F1a offspring.

F1b Offspring - Group 1 (Control (0 ppm)): 3 males and 3 females were found dead on lactation days 0-6; Group 2 (80 ppm): 3 males and 3 females were found dead on lactation days 0-4; Group 3 (750 ppm): 2 males were found dead on lacation days 4-11; and one pup was found dead, partially cannabalized on lacation day 0. Please see table Table 7 (pup observations (F1b)) of the attached study report for further details.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
F1a Offspring - No compound-related findings were reported

F1b Offspring - No compound-related findings were reported
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
F1a Offspring - No compound-related findings were reported

F1b Offspring - No compound-related findings were reported
Food efficiency:
not specified
Description (incidence and severity):
n/a
Water consumption and compound intake (if drinking water study):
not specified
Description (incidence and severity):
n/a
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Anogenital distance (AGD):
not examined
Nipple retention in male pups:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Description (incidence and severity):
F1a Offspring - No compound-related findings were reported

F1b Offspring - No compound-related findings were reported
Histopathological findings:
not examined
Other effects:
not examined
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
F1a Offspring - All groups were comparable to one another with respect to both litter data and pup observations.

F1b Offspring - All groups were comparable to one another with respect to both litter data and pup observations.
Key result
Dose descriptor:
NOAEL
Generation:
F1a
Effect level:
750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Dose descriptor:
NOAEL
Generation:
F1b
Effect level:
750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Critical effects observed:
no
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
F2a Offspring - No general findings of significance were recorded, but one male pup in the 80-ppm group was found to have had hydrocephalus.
F2b Offspring - General pup observations were unexceptional.

F3a Offspring - Pup general observations showed nothing to indicate compound-related effects
F3b Offspring - Pup general observations showed nothing to indicate compound-related effects
Dermal irritation (if dermal study):
not examined
Mortality / viability:
mortality observed, non-treatment-related
Description (incidence and severity):
F2a Offspring - Group 1 (Control (0 ppm)): 1 male was found dead on lactation day 4; Group 2 (80 ppm): 2 females, 1 found dead and 1 in moribund condition (killed) were found on lactation day 4 while 1 male was found dead on lacation day 20; Group 3 (750 ppm): 1 female was found dead on lactation day 4. Please see Table 12 (pup observations F2a in the attached study report for further details).

F2b Offspring - Group 1 (Control (0 ppm)): 1 male was found dead on lactation day 4; Group 2 (80 ppm): 2 males, 1 found dead on lactation day 2 and 1 found dead on lactation day 4; Group 3 (750 ppm): 1 male was found dead on lactation day 4. Please see Table 15 (pup observations F2b in the attached study report for further details).

F3a Offspring - Group 1 (Control (0 ppm)): Three males and 2 females found dead while 1 pup was cannibalized on lactation day 11. One male was found dead on lactation day 12; Group 2 (80 ppm): No mortality; Group 3 (750 ppm): 1 female found dead on lactation day 3 and 1 male found dead on lactation day 4.

F3b Offspring - Group 1 (Control (0 ppm)): 1 female was found dead and 3 females were cannabilized on lactation day 4; Group 2 (80 ppm): No mortality; Group 3 (750 ppm): 3 females were cannibalized on lactation day 4.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
F2a Offspring - No effect on body weights of F2a offspring was reported.
F2b Offspring - No effect on body weights of F2b offspring was reported.

F3a Offspring - No effect on body weights of F3a offspring was reported.
F3b Offspring - A slight reduction in mean pup weight at weaning (compared to controls) was noted in each compound-treated group, that for the high dose female pups being statistically significant (p<0.05; Student's t-test). The low-dose female pup weight, while numerically the same as that of the 750-ppm weanlings, was not statistically significant. Since mean weanling pup weights in the other generations were not appreciably different among the groups involved, the study authors felt that the F3b differences were fortuitous.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
F2a Offspring - No effect on food consumption of F2a offspring was reported.
F2b Offspring - No effect on food consumption of F2b offspring was reported.

F3a Offspring - No effect on food consumption of F3a offspring was reported.
F3b Offspring - No effect on food consumption of F3b offspring was reported.
Food efficiency:
not specified
Description (incidence and severity):
n/a
Water consumption and compound intake (if drinking water study):
not specified
Description (incidence and severity):
n/a
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Anogenital distance (AGD):
not examined
Nipple retention in male pups:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
F2a Offspring - no necropsy findings of significance were recorded, but one male pup in he 80-ppm group was found to have had hydrocephalus.
F2b Offspring - no necropsy findings of significance were reported.

F3a Offspring - Gross necropsy did not reveal any remarkable findings.
F3b Offspring - Gross necropsy did not reveal any remarkable findings.
Histopathological findings:
not examined
Other effects:
not examined
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
F2a Offspring - Except for reduced female fertility in the 750-ppm group (discussed earlier), litter data in all groups were comparable.

F2b Offspring - Except for reduced female fertility in the 750-ppm group (discussed earlier), litter data in all groups were comparable.

F3a Offspring - Litter parameters were not affected by treatment. The study authors concluded that there was nothing to suggest a compound-related effect, although female fertilitywas only 80% and 83% in the DCPD-treated groups, control fertility was worse, only 65%.

F3b Offspring - Litter data in all groups was generally comparable with respect to the various indices. Femalefertility percentages were 85, 80 and 83 for the controls, 80- and 750-ppm groups, respectively. The differences were not considered to be meaningful by the study authors.
Key result
Dose descriptor:
NOAEL
Generation:
F2a
Effect level:
> 80 - < 750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Dose descriptor:
NOAEL
Generation:
F2b
Effect level:
> 80 - < 750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Dose descriptor:
NOAEL
Generation:
other: F3a
Effect level:
750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Dose descriptor:
NOAEL
Generation:
other: F3b
Effect level:
> 80 - < 750 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reproductive Toxicity
Key result
Critical effects observed:
no
Key result
Reproductive effects observed:
yes
Lowest effective dose / conc.:
750 ppm (nominal)
Treatment related:
yes
Relation to other toxic effects:
not specified
Dose response relationship:
yes
Relevant for humans:
not specified

Diet Concentrations

Overall, the  results of the DCPD weekly feed analyse showed  a  69.3 ppm  (87%)  average value for the 80-ppm diet level,  and 693 ppm  (92%)  for the  750-ppm diet level.  Considering the volatility of DCPD,  these results are thought  to indicate reasonable achievement of the intended dietary concentrations.

Table 2. Mean Food Consumption (G) In F1b Rats

Dose (ppm)

Sex

 

Week

4

9

11

20

0

Male

Mean

25

26

26

32

SD

3.8

3.0

3.7

5.7

SE

1.2

1.1

1.4

1.8

N

10

8

7

10

 

80

Male

Mean

26

28

27

30

SD

3.2

1.3

1.7

3.2

SE

1.3

0.46

0.55

1.0

N

6

8

10

10

 

750

Male

Mean

25

25

25

25*

SD

1.9

1.9

0.58

3.2

SE

0.67

0.63

0.20

1.0

N

8

9

8

10

 

0

Female

Mean

22

22

23

29

SD

4.6

4.2

6.0

4.0

SE

1.1

0.89

1.4

1.0

N

17

18

18

16

 

80

Female

Mean

25

25

26

33

SD

2.6

3.6

4.4

6.1

SE

0.91

0.96

1.2

1.4

N

8

14

13

18

 

750

Female

Mean

21

22

21

24*

SD

4.9

4.3

5.0

5.9

SE

1.3

1.0

1.2

1.6

N

15

17

19

14

*p<0.05 as compared to controls: Student's t-test

Table 3. Summary of First Generation – First Mating (F1a)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

10/10

100

10/10

100

9/10

90

 

Female Fertility

(females producing litter/ mated)

19/20

95

18/20

90

16/20

80

 

Gestation

(females live litter/pregnant)

19/19

100

18/18

100

16/16

100

 

Newborn viability

(live pups/total pups)

209/211

99

210/212

99

198/200

99

 

Pup Viability

(pups Day 4/pups Day 0)

205/209

98

207/210

99

194/198

98

 

Lactation

(pups Day 21/pups Day 4)a

140/140

100

140/140

100

128/128

100

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

7 ± 0.66

7 ± 0.68

7 ± 0.60

Day 0 females

7 ± 0.75

6 ± 0.59

6 ± 0.72

Day 21 males

52 ± 5.4

50 ± 5.6

48 ± 5.1

Day 21 females

49 ± 4.6

46 ± 5.1

46 ± 4.7

Sex Ratio offspring (M/F Day 0)

110/101

111/101

94/106

Live pups per litter (Mean ± SD)

11 ± 3.7

12 ± 2.8

12 ± 2.3

aAfter Litters Reduced

Table 4. Summary of F0 Generation – Second Mating (F1b)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

10/10

100

10/10

100

10/10

100

 

Female Fertility

(females producing litter/ mated)

18/20

90

18/20

90

19/20

95

 

Gestation

(females live litter/pregnant)

18/18

100

18/18

100

19/19

100

 

Newborn viability

(live pups/total pups)

199/201

99

196/202

97

229/231

99

 

Pup Viability

(pups Day 4/pups Day 0)

193/199

97

187/196

95

216/229

94

 

Lactation

(pups Day 21/pups Day 4)a

128/132

97

128/132

97

139/145

96

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

6 ± 1.1

5 ± 1.6

6 ± 0.61

Day 0 females

6 ± 1.1

5 ± 1.6

6 ± 0.61

Day 21 males

46 ± 7.8

47 ± 8.8

42 ± 6.8

Day 21 females

44 ± 6.9

44 ± 8.2

40 ± 5.7

Sex Ratio offspring (M/F Day 0)

100/101

94/108

108/123

Live pups per litter (Mean ± SD)

11 ± 3.5

11 ± 3.7

12 ± 3.2

aAfter Litters Reduced

Table 5. Summary of F1b Generation – First Mating (F2a)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

10/10

100

10/10

100

9/10

90

 

Female Fertility

(females producing litter/ mated)

19/20

95

18/20

90

14/20

70

 

Gestation

(females live litter/pregnant)

19/19

100

18/18

100

14/14

100

 

Newborn viability

(live pups/total pups)

241/242

100

209/216

97

162/162

100

 

Pup Viability

(pups Day 4/pups Day 0)

237/241

98

196/209

94

159/162

98

 

Lactation

(pups Day 21/pups Day 4)a

147/150

98

135/139

97

107/109

98

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

6 ± 0.90

6 ± 0.84

6 ± 0.83

Day 0 females

6 ± 0.79

6 ± 0.92

6 ± 0.95

Day 21 males

44 ± 5.9

46 ± 6.4

44 ± 5.5

Day 21 females

41 ± 5.3

43 ± 6.6

42 ± 5.3

Sex Ratio offspring (M/F Day 0)

111/131b

94/122b

84/78b

Live pups per litter (Mean ± SD)

13 ± 2.6

12 ± 2.7

12 ± 2.7

aAfter Litters Reduced

bSome pups mis-sexed

Table 6. Summary of F1b Generation – Second Mating (F2b)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

10/10

100

10/10

100

9/10

90

 

Female Fertility

(females producing litter/ mated)

19/20

95

19/20

95

17/20

85

 

Gestation

(females live litter/pregnant)

19/19

100

19/19

100

17/17

100

 

Newborn viability

(live pups/total pups)

263/266

99

286/287

100

230/235

98

 

Pup Viability

(pups Day 4/pups Day 0)

250/263

95

280/286

98

214/230

93

 

Lactation

(pups Day 21/pups Day 4)a

149/151

99

149/152

98

127/128

99

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

6 ± 0.84

6 ± 0.63

6 ± 0.54

Day 0 females

6 ± 0.75

6 ± 0.52

6 ± 0.66

Day 21 males

45 ± 6.8

48 ± 7.2

51 ± 6.6

Day 21 females

43 ± 7.4

46 ± 6.6

48 ± 6.6

Sex Ratio offspring (M/F Day 0)

121/145

146/141

119/116

Live pups per litter (Mean ± SD)

14 ± 2.5

15 ± 1.6

14 ± 1.4

aAfter Litters Reduced

Table 7. Summary of F2b Generation – First Mating (F3a)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

9/10

90

10/10

100

8/9

89

 

Female Fertility

(females producing litter/ mated)

13/20

65

16/20

80

15/18

83

 

Gestation

(females live litter/pregnant)

13/13

100

16/16

100

15/15

100

 

Newborn viability

(live pups/total pups)

162/163

99

195/196

99

204/206

99

 

Pup Viability

(pups Day 4/pups Day 0)

156/162

96

187/195

96

201/204

99

 

Lactation

(pups Day 21/pups Day 4)a

92/100

92

118/118

100

117/120

98

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

6 ± 0.77

6 ± 1.3

7 ± 0.82

Day 0 females

7 ± 0.80

5 ± 1.2

6 ± 0.80

Day 21 males

46 ± 5.8

46 ± 4.7

48 ± 6.1

Day 21 females

45 ± 7.6

42 ± 4.2

45 ± 5.7

Sex Ratio offspring (M/F Day 0)

81/82

103/92

108/98

Live pups per litter (Mean ± SD)

12 ± 3.3

12 ± 3.9

14 ± 2.0

aAfter Litters Reduced

Table 8. Summary of F2b Generation – First Mating (F3b)

Indices

Dose (ppm)

0

80

750

Ratio

Percent

Ratio

Percent

Ratio

Percent

Male Fertility

(males producing litter/ mated)

9/10

90

10/10

100

9/9

100

 

Female Fertility

(females producing litter/ mated)

17/20

85

16/20

80

15/18

83

 

Gestation

(females live litter/pregnant)

17/17

100

16/16

100

15/15

100

 

Newborn viability

(live pups/total pups)

211/215

98

206/213

97

188/191

98

 

Pup Viability

(pups Day 4/pups Day 0)

207/211

98

206/206

100

185/188

98

 

Lactation

(pups Day 21/pups Day 4)a

134/135

99

127/128

99

114/117

97

 

Pup Weight in Grams (Mean ± SD)

Day 0 males

6 ± 0.79

7 ± 0.98

7 ± 0.83

Day 0 females

6 ± 0.64

6 ± 0.87

6 ± 0.83

Day 21 males

49 ± 10

44 ± 11

43 ± 11

Day 21 females

48 ± 9.3

41 ± 12

41 ± 9.5*

Sex Ratio offspring (M/F Day 0)

93/122

107/106

93/98

Live pups per litter (Mean ± SD)

12 ± 2.7

13 ± 2.5

13 ± 2.8

aAfter Litters Reduced

*p<0.05 compared to control: Student’s t-test.

Conclusions:
The authors of the study considered that dietary administration of DCPD at 80 and 750 ppm to three successive generations of rats had no deleterious effects on reproductive performance or the general condition of the animals. However, DCPD was not devoid of reproductive or systemic effects at the 750 ppm dietary level, as previously described.

Thus, the NOAEL in this study is considered to be between 80 - 750 ppm (69 - 693 ppm actual concentration).

Executive summary:

This three generation reproduction non-GLP study in rats using dicyclopentadiene was conducted in 1979, prior to the adoption of the OECD test guidelines for reproductive and developmental toxicity. However the methods used and overall quality of the study were considered similar to OECD 416 and the study was considered adequate for assessment.

 

F0 rats were mated seven weeks after initiation of treated diet. Selected F1b pups were designated F1 parents and were approx. 100 days old when mated to produce the F2a litters and subsequently the F2b litters. Selected F2b pups were designated F2 parents and similarly used to produce the F3 a and b litters. Animals were exposed to nominal dietary concentrations of 0, 80, 750 ppm DCPD.

 

The authors of the study considered that dietary administration of DCPD at nominal concentrations of 80 and 750 ppm to three successive generations of male and female albino rats had no deleterious effects on reproductive performance or the general condition of the animals, in comparison to performance of control rats maintained concurrently. However, DCPD was not devoid of reproductive or systemic effects at the 750 ppm dietary level. Mean food consumption at 20 weeks in the F1B parents was reduced in both sexes in a treatment-related manner, with statistical significance at the 750 ppm level. At 750 ppm, female fertility was reduced in the F2A and F2B generations, however, the differences from control were not statistically significant, and this may have been due to one male in the 750 ppm group that failed to sire litters in either mating. A treatment- related reduction in mean pup weight on PND 21 was noted in the F3B generation, with mean m/f pup weights of 49/48, 44/41, and 43/41* grams in the control, 80 and 750 ppm groups, respectively.

 

Thus, the NOAEL in this study is considered to be between 80 - 750 ppm (69 - 693 ppm actual concentration).

Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
Study duration:
subchronic
Species:
rat
Quality of whole database:
Three generation reproductive toxicity study (Klimisch score = 2). The NOAEL was considered to be between 80 - 750 ppm (69 - 693 ppm actual concentration).
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

Non-human information:

In a key three generation reproduction study (Litton Bionetics, LBI Project no. 10734 -07, 1979, pre-GLP) with two litters per generation, dicyclopentadiene (DCPD) was administered to Sprague Dawley rats (10 males and 20 females per dose group) in the diet at nominal concentrations of 0, 80 or 750 ppm. DCPD was suspended in 300 mL corn oil and blended with 10 kg of the basal diet. Samples of each diet were analysed at weekly intervals by gas-liquid chromatography. The results showed actual average dietary concentrations of 69.3 ppm (87% of nominal) and 693 ppm (92% of nominal) for the low and high dietary groups. The second and third generations were derived from the second (b) litters of the previous generation. 

One F0 female from the 80 ppm group was found dead on study week 28 but all other F0 rats survived until the end of the study. Mean food consumption at 20 weeks in the F1B parents was reduced in both sexes in a treatment-related manner, with statistical significance at the 750 ppm level. At 750 ppm female fertility was reduced in the F2A and F2B generations, however, the differences from control were not statistically significant and this may have been due to one male in the 750 ppm group that failed to sire litters in either mating. A treatment-related reduction in mean pup weight on PND 21 was noted in the F3B generation with mean m/f pup weights of 49/48, 44/41, and 43/41* grams in the control, 80 and 750 ppm groups, respectively.

The authors of the study considered that dietary administration of DCPD at 80 and 750 ppm to three successive generations of rats had no deleterious effects on reproductive performance or the general condition of the animals. However, DCPD was not devoid of reproductive or systemic effects at the 750 ppm dietary level, as described above. Thus, the NOAEL is considered to be between 80 - 750 ppm (69 - 693 ppm actual concentration).

According to the BG Chemie Toxicological Evaluation No. 84 (dicyclopentadiene), the highest concentration (693 ppm) was judged equivalent to a daily intake of 50 mg/kg body weight at an assumed feed intake of 70 g/kg body weight/day. Consideration of the reported food and body weight data at week 4 (when the amount of dicyclopentadiene consumed would be high in relation to body weight) indicates that males of 300g body weight consuming 25g diet would receive 58 mg/kg/ body weight/day and females of 200g body weight consuming 25g diet would receive 87 mg/kg/ body weight/day. The value for females would not be exceeded during pregnancy.

In a supporting OECD test guideline 422 (combined repeated dose toxicity study with the reproduction/developmental toxicity screening test), dicyclopentadiene (DCPD), was administered to rats by oral gavage at dose levels of 0, 4, 20 or 100 mg/kg/day (Matsuura 1993). This study was conducted in compliance with GLP at the Mitsubishi Chemical Safety Inst., Kashima Laboratory, Japan. The doses used were selected following a dose range-finding study, in which male and female rats were orally dosed for 10 days with 0, 30, 100 or 300 mg/kg/day. The high dose in the range-finding study produced lethality, so the top dose for the OECD 422 study was set at 100 mg/kg/day. Although the study report is written in Japanese, the study details were summarized in English by the Japan Chemical Industry Ecology-Toxicology and Information Centre JETOC (1998a), and an abridged English translation of the GLP study report is also available.

The study design for OECD Guideline 422 includes administration of the test substance for two weeks prior to the mating of male and female rats and, during mating (approximately 2 weeks). The females continue to be dosed throughout gestation and until termination on day 4 of lactation. The males are dosed through to approximately day 45 of the study.

In the 100 mg/kg/day group, two females died. In these decedents the following findings were observed: lung congestion, enlargement of the adrenal gland, bleeding in the thymus and bleeding in the gastric mucosa. In addition, signs of systemic toxicity were seen in both males and females in the 100 mg/kg/day group, including transient salivation, depressed body weight gain and decreased food consumption. An increase in the incidence of fatty droplets in the fascicular zone of the adrenals in males and females in the high dose group and in males in the mid-dose group were reported to be of unknown toxicological significance. Based on these observations, the NOAEL for systemic toxicity of the parental animals in this study appears to have been 4 mg/kg/day for males and 20 mg/kg/day for females.

DCPD had no effects on reproductive parameters such as: mating index, fertility index, gestation length, number of corpora lutea or implantations, implantation index, gestation index, delivery index or parturition. However, two dams in the 100 mg/kg/day group had total litter loss during the lactation period. Examination of the neonates in the 100 mg/kg/day group revealed a low viability index, lower birth weight and reduced body weight gain. The number of live pups on PND 4 and the viability index were: 16.3/98.9%; 13.4/99.2%; 13.2/100% and 9.1*/66.1**% in the 0, 4, 20 and 100 mg/kg/day groups, respectively. There were no significant differences in the number of offspring or live offspring at birth, the sex ratio or the live birth index. Exposure to DCPD produced no effects on external features, clinical signs or necropsy of the offspring. Based on these results, the NOAEL for parental females and offspring appears to be 20 mg/kg/day and for parental males is 100 mg/kg/day.

The reproductive effects of DCPD were also evaluated in a continuous breeding study in Sprague-Dawley rats performed by US NTP (Jamieson et al., 1995). Although a Society of Toxicology abstract is available for this study, the full study report is not available, and therefore it is considered to be Klimisch category 4. In this study oral (gavage) doses of 100 mg/kg/day DCPD was shown to produce reproductive effects such as reduced pup body weight, increased pup mortality and decreased pup survival in F1 litters. Effects in the F2 generation were similar to those in F1. It is uncertain if the F1 -F2 pup body weight reductions (9 -12%) were secondary to maternal toxicity.

There are no reproduction studies available using the dermal or inhalation routes of exposure to dicyclopentadiene.

Human information:

There are no human data available for effects of dicyclopentadiene on fertility.


Effects on developmental toxicity

Description of key information

The rat maternal NOAEL was established to be 30 mg/kg/day and the developmental NOAEL to be at least 30 mg/kg/day (OECD 414 study).

The rabbit maternal and developmental NOAELs were established to be 20 mg/kg/day (OECD 414 study).

Link to relevant study records

Referenceopen allclose all

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 January 2021 - 23 May 2022
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Version / remarks:
Version: June 2018
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
n/a
Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
TEST ANIMALS:
Source: Charles River (Chatillon sur Chalaronne, France)
Age at dosing: 18-20 weeks old
Weight (on the first day of dosing): 2886 to 4250 g (at initiation of dosing)
Housing: individually housed in Cages with perforated floors (Ebeco, Germany, dimensions 67 x 62 x 55 cm) equipped with water bottles. Cages were arranged on the racks according to a Latin square model.
Diet:Pellets (KLIBA NAFAG Rabbit Diet 3409 maintenance and breeding, from Granovit AG, Kaiseraugst, Switzerland). Restricted access. On arrival, animals received approximately 25 grams pelleted diet and on subsequent days 140-160 grams was supplied.
Water: ad libitum
Acclimation period: at least 4 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-19°C
- Humidity (%): 47-55%
- Photoperiod (hrs dark / hrs light):12-hours light and 12-hours dark (except during designated procedures)
- Ventilation ten or more air changes per hour
Route of administration:
oral: gavage
Vehicle:
corn oil
Remarks:
Supplier: Sigma Aldrich
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The design of test item analysis was based on ICH Harmonised Tripartite Guideline Q2 (R1): Validation of Analytical Procedures: Text and Methodology. November 2005.
A quantitative analysis of the test item in vehicle was performed by an ultra performance liquid chromatographic method with spectrophotometric detection (UPLC-UV) in order to determine the accuracy, homogeneity, stability and resuspension of formulations over a large concentration range.
Concentration results were considered acceptable if mean sample concentration results were within or equal to 90-110% of target concentration. Homogeneity results were considered acceptable if the coefficient of variation was = 5%. Stability results were considered acceptable if the relative difference between the stored and initial taken samples was = 10%. Resuspension homogeneity was demonstrated if the coefficient of variation is = 5%.
Calibration curves were constructed using six concentration levels. For each level, duplicate responses were used. Linear regression analysis was performed using the least squares method with a 1/concentration2 weighting factor. The coefficient of correlation (r) was > 0.99 for each curve.
The mean accuracies of the QC samples were within the criterion range of 90-110%. It demonstrated that the analytical methods were adequate for the determination of the test item in the study samples.
The formulations at 1 mg/mL and 200 mg/mL were homogeneous (i.e. coefficient of variation = 5%).
Analysis of the formulations after storage at room temperature yielded a relative difference of = 10%. The formulations were found to be stable when stored at room temperature protected from light for at least 5 hours, in a refrigerator (2-8°C) protected from light for at least 8 days, and in a freezer (= -15°C) protected from light for at least 21 days (3 weeks). Resuspension homogeneity after storage in a refrigerator for 8 days was demonstrated with a coefficient of variation of = 5%.
Results:
The concentrations analyzed in the formulation of Group 3 were in agreement with target concentrations (i.e. mean accuracies between 90% and 110%).
For the formulation of Groups 2 and 4, the mean accuracies were below the target concentration (i.e. both 88% of target). The results were accepted as they were only slightly below the target concentration.
No test item was detected in the Group 1 formulation.
The formulations of Groups 2, 3 and 4 were homogeneous (i.e. coefficient of variation = 10%).
Details on mating procedure:
Untreated females were mated at the Supplier and were at Day 1-2 post-coitum (Day 0 post-coitum is defined as the day of successful mating) when arrived at test facility.
Duration of treatment / exposure:
Day 6 to Day 28 post-coitum
Frequency of treatment:
Once daily
Duration of test:
Day 6 to Day 28 post-coitum
Dose / conc.:
0 mg/kg bw/day
Dose / conc.:
20 mg/kg bw/day
Dose / conc.:
60 mg/kg bw/day
Dose / conc.:
200 mg/kg bw/day
No. of animals per sex per dose:
22 females per dose
Control animals:
yes, concurrent vehicle
Details on study design:
Rationale for Test System and Number of Animals:
Studies in laboratory animals provide the best available basis for extrapolation to humans and are required to support regulatory submissions. Acceptable models which do not use live animals currently do not exist. The New Zealand White rabbit was chosen as the animal model for this study as it is an accepted non-rodent species for developmental toxicity testing by regulatory agencies. Charles River Den Bosch has historical data on the background incidence of fetal malformations and developmental variations in this species from the same strain and source. This animal model has been proven to be susceptible to the effects of developmental toxicants. The total number of animals used in this study was considered to be the minimum required to properly characterize the effects of the test item. This study has been designed such that it does not require an unnecessary number of animals to accomplish its objectives. This Study Plan was reviewed and agreed by the Animal Welfare Body of Charles River Laboratories Den Bosch B.V. within the framework of Appendix 2 of project license AVD2360020172866 approved by the Central Authority for Scientific Procedures on Animals (CCD) as required by the Dutch Act on Animal Experimentation (December 2014).

Rationale for Route and Dose Levels:
The oral route of exposure was requested by the ECHA (European Chemicals Agency) in the Final Decision Letter following a Compliance Check (ECHA, 2020); they considered that this route was the most appropriate for hazard characterization.
The dose levels were selected based on the results of the Dose Range Finder, at the request of the Study Monitor and in an attempt to produce graded responses to the test item. These dose levels were considered to have a better dose spacing (i.e. 3 to 4 fold as recommended in the OECD 414 TG (2018)) than the previously used dose levels of 50, 100 and 200 mg/kg/day which were utilized in the previous dose range finding study in the rabbit. The high dose level of 200 mg/kg/day has been selected as this dose level is expected to produce some toxicity such as a reduction in body weight gain and food consumption, but not excessive lethality that would prevent meaningful evaluation, at this dose level in the previous dose range finding study in the rabbit effects were observed on body weight, bodyweight gain and food consumption, therefore, based on the magnitude of body weight loss being observed which was approximately 100 g to 150 g based on significantly reduced food consumption and/or inappetence in the first three days of dosing (Days 6 to 9 of gestation) it was considered that this would be an adequate high dose level as the previous information from the Gulati (1993) study showed that higher doses gave increased mortality at 300 mg/kg/day and 400 mg/kg/day, in 1/9 and 3/9 animals, respectively, which would be excessive and signs of systemic toxicity were also noted (body weight loss and decreased food and water consumption). A decreased body weight gain was also noted at 200 mg/kg/day on this previous study; therefore, this further justifies that the high dose level should not exceed 200 mg/kg/day, in order not to prevent meaningful evaluation.
It is also noteworthy, that there were no effects observed at 100 mg/kg/day or 25 mg/kg/day on the previous Gulati (1993) study. However, the mid-dose level of 60 mg/kg/day is expected to produce minimal to moderate toxicity and be a no observed-adverse-effect-level for maternal toxicity and developmental toxicity. The low-dose level of 20 mg/kg/day should produce no observable indications of toxicity and be a clear no-observed-effect-level for maternal and developmental toxicity.

References:
Gulati D.R, Grimes L. K. and Smith M. (1993). Range Finding Studies: Developmental Toxicity of Dicyclopentadiene When Administered Via Gavage In New Zeland White Rabbits. Report. Stuyd No:NTP-92-RF/DT-044
Maternal examinations:
Mortality/Moribundity Checks:
At least twice daily throughout the study. Animals were observed for general health/mortality and moribundity. Animals were not removed from the cage during observation, unless necessary for identification or confirmation of possible findings.

Clinical Observations:
At least once daily, starting on Day 6 post-coitum onwards up to the day prior to necropsy. During the dosing period, this observation were performed immediately postdose. Animals were removed from the cage for clinical sign observation. Clinical sign examination was performed according to standard procedures for the cage side observation as well as the detailed observation. Cage debris was examined to detect premature birth, if applicable.

Body Weights:
Animals were weighed on Days 6, 9, 12, 15, 18, 21, 24, 27 and 29 post coitum. In addition, data on body weight Day 0 post-coitum (i.e. the day of mating) was provided by the Supplier (non-GLP) and included in the report. Animals were individually weighed.

Food Consumption:
Food consumption of animals were measured daily from Day 3 post coitum onwards. Food consumption was quantitatively measured.

Water Consumption:
Regular basis throughout the study. Water consumption was monitored by visual inspection of the water bottles.

Terminal Procedures:
Unscheduled Deaths: one female in the control group, three females in the 60 mg/kg/day dose group and seven females in the 2000 mg/kg/day dose group were euthanised for humane reasons by an intravenous injection of sodium pentobarbital, underwent necropsy, and specified tissues were retained.
Scheduled Euthanasia:animals surviving until scheduled euthanasia were euthanized by an intravenous injection of sodium pentobarbital on Day 29 post-coitum.

Necropsy:
All animals (including animals sacrificed before planned necropsy) were subjected to an external, thoracic and abdominal examination, with special attention being paid to the reproductive organs. All macroscopic abnormalities were recorded, collected and fixed in 10% buffered formalin.

Organ Weights:
The uterus was weighed at necropsy for all scheduled euthanasia animals. Organ weights were not recorded for animals euthanized in poor condition or in extremis

Tissue Collection and Preservation:
Macroscopic abnormalities and placentas of live fetuses were collected from all animals and preserved in 10% buffered formalin or Davidson’s fixative and were transferred to formalin after at least 24 hours.
Ovaries and uterine content:
Each ovary and uterine horn of all animals were dissected and examined as quickly as possible to determine:
-number of corpora lutea
-weight of the uterus (not for animals sacrificed before planned necropsy)
-placental weights (for live fetuses only; after weighing, placentas were fixed in formalin)
-number of implantation sites
-number and distribution of live and dead fetuses
-number and distribution of early and late resorptions
Blood sampling:
Not examined
Fetal examinations:
Fetal examinations:
For recognisable fetuses or normal implantations in development of females sacrificed before planned necropsy, a gross external examination was performed (if possible). Recognisable fetuses with abnormalities were fixed in 10% buffered formalin.
Litters of females surviving to scheduled necropsy were subjected to detailed external, visceral and skeletal examinations, as described in the following sections. External, visceral, and skeletal findings were recorded as developmental variations (alterations in anatomic structure that are considered to have no significant biological effect on animal health or body conformity and/or represent slight deviations from normal) or malformations (those structural anomalies that alter general body conformity, disrupt or interfere with normal body function, or may be incompatible with life).

External examinations:
Each viable fetus was examined in detail to detect macroscopic visible abnormalities and their weight (not for fetuses of animals sacrificed before planned necropsy) was determined.
Nonviable Fetus in one of the littes of the 20 mg/kg/day dose group was examined and weighed.
For late resorptions (three fetuses in the control group, three fetuses in the 20 mg/kg/day dose group and three fetuses in the 200 mg/kg/day dose group), a gross external examination was performed.

Visceral Examinations:
The sex of all fetuses was confirmed by internal examination and approximately one-half of all fetuses were internally sexed and examined for visceral anomalies by dissection in the fresh (non-fixed) state. The thoracic and abdominal cavities were opened and dissected. This examination included the heart and major vessels. Fetal kidneys were examined and graded for renal papillae development. Abnormalities were not collected and fixed at discretion of the Study Director.
The heads were removed from approximately one-half of the fetuses in each litter and placed in Bouin's solution for soft-tissue examination of all groups After examination, the tissues without variation or malformations were discarded. Tissues with variations or malformations were stored in 10% formalin. The heads from the remaining one-half of the fetuses in each litter of all groups were examined by a mid-coronal slice. All carcasses, including the carcasses without heads, were eviscerated, skinned, labeled and fixed in 96% aqueous ethanol for subsequent examination of skeletons.

Skeletal Examinations:
All eviscerated fetuses, following fixation in 96% aqueous ethanol, were macerated in potassium hydroxide and processed for double staining with Alcian Blue 8GX and Alizarin Red S. Subsequently, the skeletal examination was done on all fetuses from all groups. All specimens were archived in glycerin with bronopol as preservative. A few bones were not available for skeletal examination because they were accidentally damaged or lost during processing. The missing bones were listed in the raw data; evaluation by the fetal pathologist and Study Director determined there was no influence on the outcome of the individual or overall skeletal examinations, or on the integrity of the study as a whole.
Statistics:
Numerical data collected on scheduled occasions were summarised and statistically analyzed according to sex and occasion or by litter (Table 1).
Means, standard deviations (or % coefficient of variation or standard error, when deemed appropriate), ratio, percentages, numbers, and/or incidences were reported as appropriate by dataset.
All statistical tests were conducted at the 5% significance level. All pairwise comparisons were conducted using two sided tests and were reported at the 1% or 5% levels.
The following pairwise comparisons were made:
Group 2 vs. Group 1
Group 3 vs. Group 1
Group 4 vs. Group 1
Analyses were performed according to the matrix (Table 2) when possible but exclude any group with less than 3 observations.

Parametric/Non-Parametric
Levene’s test was used to assess the homogeneity of group variances.
The groups were compared using an overall one-way ANOVA F-test if Levene’s test was not significant or the Kruskal-Wallis test if it was significant. If the overall F-test or Kruskal Wallis test was found to be significant, then pairwise comparisons were conducted using Dunnett’s or Dunn’s test, respectively.
Non-Parametric
The groups were compared using an overall Kruskal-Wallis test. If the overall Kruskal Wallis test was found significant, then the above pairwise comparisons were conducted using Dunn’s test.
ANCOVA
The data corresponding to a response variable of interest and to a related covariate were submitted to an analysis of covariance (ANCOVA), including only groups with at least three non-missing paired values and if found to be significant, then pairwise comparisons were conducted using Dunnett’s test.
Incidence
A Fisher’s exact test was used to conduct pairwise group comparisons of interest.
Indices:
n/a
Historical control data:
Charles River Den Bosch has historical data on the background incidence of fetal malformations and developmental variations in this species from the same strain and source.
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Females with premature deaths showed hunched posture, piloerection and/or a thin appearance (Table 1). One female at 200 mg/kg/day, which was sacrificed in extremis on Day 13 post-coitum, was noted with limited usage of the hindlegs during the morning check. Examination by a veterinarian confirmed paralysis of both the hindlegs. This finding was correlated with a dislocation of lumbar vertebra no. 7 and accumulation of dark red fluid in the same area at necropsy. No explanation was found for the dislocated vertebra, however given the convulsions observed for another female at 200 mg/kg/day, this female may have had convulsions as well that could have caused the dislocation of the vertebra. As such, a possible relationship with treatment with the test item could not be excluded.
At 60 and 200 mg/kg/day, decreased feces output was observed for most females at a higher incidence compared to control animals and with a higher incidence with increasing dose.
At 200 mg/kg/day, erected fur and/or a thin appearance were regularly noted for 6/15 surviving animals between Days 9 and 21 post-coitum.
One animal in the 200 mg/kg/day dose group was in a poor condition on Day 20 post-coitum and was examined by a veterinarian. The animal showed convulsions, slight tremors, an abnormal stance, small pupils and hyperemia of the right nictitans with a fixed stare. Additionally, the animal showed abnormal chewing, an increased heart rate, panting and had a pale appearance. These clinical signs were of short duration; the next morning, no abnormalities were noted for this animal.
At 20 mg/kg/day, no test item-related clinical observations were noted. Decreased feces output was observed for most females. This finding was considered to be unrelated to treatment with the test item because it also occurred in control animals at a comparable incidence.
Other clinical observations recorded occurred within the range of background findings to be expected for rabbits of this age and strain which are housed and treated under the conditions in this study. At the incidence observed, these were considered to be unrelated to treatment with the test item.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, treatment-related
Description (incidence):
A total of 11 females did not survive until scheduled necropsy: one control female, three females at 60 mg/kg/day and seven females at 200 mg/kg/day. Of these premature deaths, one female at 60 mg/kg/day and five females at 200 mg/kg/day were considered to be related to treatment with the test item. All of these females showed strongly reduced or no food intake for at least 6 consecutive days, along with body weight loss (12%) and a decreased feces output. Additionally, one female at 200 mg/kg/day was sacrificed in extremis on Day 13 post-coitum.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
At 60 mg/kg/day, a reduced body weight gain compared to controls was observed between Days 6 and 15 post coitum, followed by a slight body weight loss between Days 18-21 post coitum and increased body weight gain thereafter (Table 2 and 3). Overall body weight gain between Days 6 and 29 post-coitum was 90% of control.
At 200 mg/kg/day, body weight losses were noted mainly between Days 6 and 9 post-coitum. Mean body weight gain remained lower than controls up to Day 15 post-coitum, after which mean body weight gain was similar or even higher compared to control animals. Overall body weight gain between Days 6 and 29 post-coitum was 61% of control.
At 20 mg/kg/day, mean body weights, body weight gain and weight gain corrected for gravid uterus of treated animals remained in the same range as control over the treatment period.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
At 60 and 200 mg/kg/day, a (slightly) lower food consumption was noted, mainly between Days 6 and 18 post-coitum (not always statistically significant) (Table 4). In subsequent intervals, food consumption was similar to controls. Mean food consumption over Days 6 to 29 post-coitum was 90% and 70% of control, respectively (reaching no statistical significance at 60 mg/kg/day).
At 20 mg/kg/day, mean food consumption was similar to the control level over the study period.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Gross pathological findings:
no effects observed
Description (incidence and severity):
Macroscopic observations at necropsy did not reveal any alterations that were considered to have arisen as a result of treatment with the test item.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Details on results:
All females, including the preterm sacrificed animals, were found to be pregnant, except for one female in the 20 mg/kg/day dose group , one female in the 60 mg/kg/day dose group and one female in the 200 mg/kg/day dose group.
Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
The numbers of pre- and post implantation loss in the control and test groups were considered in the range of normal biological variation (Table 5).
Total litter losses by resorption:
not specified
Early or late resorptions:
not specified
Description (incidence and severity):
There were 2 females of the 60 and 200 mg/kg/day groups each with early resorptions only (Table 5). These 4 females were all preterm sacrifices: one female had an early abortion on Day 20, and three females were sacrificed for welfare reasons due to severe body weight loss and low food consumption. At the incidence observed, a relationship with the test item could not be excluded.
Dead fetuses:
not specified
Description (incidence and severity):
The total number of litters with viable fetuses available for evaluation was 21, 21, 18 and 15 in the control, 20, 60 and 200 mg/kg/day groups, respectively (Table 5).
Changes in pregnancy duration:
not specified
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
The numbers of corpora lutea and implantation sites in the control and test groups were considered in the range of normal biological variation (Table 5).
Other effects:
not examined
Key result
Dose descriptor:
NOAEL
Effect level:
20 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
body weight and weight gain
food consumption and compound intake
Key result
Abnormalities:
effects observed, treatment-related
Localisation:
other: clinical effects
Description (incidence and severity):
hunched posture, piloerection and/or a thin appearance, convulsions, slight tremors, an abnormal stance, small pupils and hyperemia of the right nictitans with a fixed stare, abnormal chewing, an increased heart rate, panting and had a pale appearance, reduced food intake and body weight loss.
Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
At 200 mg/kg/day, male fetal weights were considered affected by treatment with the test item (Table 5). Male fetal weights appeared to be more affected than female fetal weights, as mean values were, respectively, 11 and 3% lower than concurrent control weights (not statistically significant). The mean combined fetal weight was 7% lower than concurrent controls.
The fetal weights (male, female and combined) were comparable to the controls for the 20 and 60 mg/kg/day dose groups and remained within the historical control range of the Test Facility.
Reduction in number of live offspring:
not specified
Changes in sex ratio:
no effects observed
Description (incidence and severity):
The male:female ratio was considered unaffected by treatment with the test item up to 200 mg/kg/day (Table 5).
Changes in litter size and weights:
no effects observed
Description (incidence and severity):
There were no test item-related effects on litter size of any group (Table 5).
Mean litter sizes were 9.0, 8.3, 9.2 and 9.5 live fetuses/litter for the control, 20, 60 and 200 mg/kg/day groups, respectively.
Anogenital distance of all rodent fetuses:
not examined
Changes in postnatal survival:
not specified
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
At scheduled necropsy, one fetus of the control, 20 mg/kg/day and 200 mg/kg/day dose groups each presented with external malformations (Table 7). The fetus in the control group appeared with multiple external malformations including hyperflexion of both forepaws, ectrodactyly of the left forepaw, a misshapen right forepaw and lastly omphalocele. The (dead) fetus from the low dose group (20 mg/kg/day) presented with a distended abdomen, and the fetus from the high dose group (200 mg/kg/day) had a hyperflexion of the left forepaw and gastroschisis.
Additionally, one fetus from the mid-dose group (60 mg/kg/day) that did not survive until scheduled necropsy had an omphalocele.
Due to a lack of a dose-related response and/or comparable observations in the control group, the recorded external malformations were considered chance findings and not related to the test-item.
No external variations were observed in this study.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Skeletal malformations were observed in 4, 3, 2 and 1fetuses of the control, 20, 60 and 200 mg/kg/day groups, respectively (Table 6) and 7.
Skeletal malformations occurred in the forepaw, ribs, sternebra and vertebra. All occurred in single animals and/or in absence of a dose-related response and were therefore considered to be chance findings.
Higher incidences of unossified fore- and hindpaw phalanges (variations) were noted in fetuses of the 200 mg/kg/day group. Mean litter incidences were 8 and 25%, respectively, vs 1 and 10% in the concurrent group (not statistically significant).
All other skeletal variations occurred in the absence of a dose-related incidence trend and/or infrequently. Therefore, they were considered not test item-related.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Visceral malformations were observed in 3, 2, 2 and 2 fetuses of the control, 20, 60 and 200 mg/kg/day groups, respectively (Table 6 and 7).
Visceral malformations occurred in the aortic arch, heart, lungs, diaphragm, ductus arteriosus, pulmonary trunk and intestines. All occurred in single animals and/or in absence of a dose related response and were therefore considered to be chance findings.
All visceral variations occurred in absence of a dose-related response. Therefore, they were considered not test item-related.
Other effects:
no effects observed
Description (incidence and severity):
Placental weight of live fetuses was considered not to be affected by treatment with the test item.
Key result
Dose descriptor:
NOAEL
Effect level:
20 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: resorptions
Key result
Developmental effects observed:
yes
Lowest effective dose / conc.:
60 mg/kg bw/day
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
not specified
Relevant for humans:
presumably yes

Table 1 Test Item-Related Premature Decedents

Dose Level

Female No.

Day of Sacrifice

Findings

60 mg/kg/day

56

Day 23 PC

-  Extremely low FC on 7 consecutive days

-  BW loss of 5% between Days 12 and 21 PC

-  Decreased feces output from Day 13 PC onwards, enlarged eyeballs on Days 22 and 23 PC

-  No macroscopic findings at necropsy

-  Gravid with 14 live fetuses

200 mg/kg/day

75

Day 14 PC

-  Extremely low/absent FC on 7 consecutive days

-  BW loss of 12% between Days 6 and 14 PC

-  Decreased feces output from Day 8 PC onwards, thin appearance on Days 12 and 14 PC, and erected fur and hunched posture on Day 14 PC

-  No macroscopic findings at necropsy

-  Gravid with 12 normal implantations

76

Day 14 PC

-  Extremely low/absent FC on 8 consecutive days

-  BW loss of 11% between Days 6 and 14 PC

-  Decreased feces output from Day 8 PC onwards, thin appearance on Days 12 and 14 PC, and erected fur and hunched posture on Day 14 PC

-  Enlarged uterus at necropsy (with no microscopic correlate)

-  Non-gravid

81

Day 14 PC

-  Extremely low FC on 8 consecutive days

-  BW loss of 9% between Days 6 and 14 PC

-  Decreased feces output from Day 7 PC onwards, thin appearance and erected fur on Days 12 and 13 PC, and hunched posture on Day 13 PC

-  No relevant macroscopic findings at necropsy

-  Gravid with 9 normal implantations

83

Day 13 PC

-  Extremely low/absent FC on 7 consecutive days

-  BW loss of 9% between Days 6 and 13 PC

-  Decreased feces output from Day 8 PC onwards, erected fur and hunched posture on Day 13 PC

-  No relevant macroscopic findings at necropsy

-  Gravid with 12 early resorptions

87

Day 18 PC

-  Extremely low/absent FC on 9 consecutive days

-  BW loss of 11% between Days 6 and 18 PC

-  Decreased feces output from Day 7 PC onwards, erected fur from Day 12 PC onwards, and thin appearance on Day 18 PC

-  No macroscopic findings at necropsy

-  Gravid with 10 normal implantations

Table 2 Summary of Body Weights: Gestation

Sex: Female Day Relative to Mating (Litter A)
  0 6 9 12 15 18 21 24 27 29
0 mg/kg/day (Group 1) Mean 3636.6 3592.1 3644.8 3699.4 3766.7 3776.8 3815 3855.4 3868.4 3916.3
SD 319.9 279.1 275.8 265 246.3 262.5 272.9 245.2 234.9 244.5
N 22 22 21 21 21 21 21 21 21 21
20 mg/kg/day (Group 2) Mean 3670.8 3612.2 3665.7 3720.3 3788 3808.3 3843.3 3871.3 3920.4 3978.2
SD 349.3 319.4 315.6 319.5 312.3 328.5 300 298.6 279.6 270.3
N 21 21 21 21 21 21 21 21 21 21
%Diff 0.9 0.6 0.6 0.6 0.6 0.8 0.7 0.4 1.3 1.6
60 mg/kg/day (Group 3) Mean 3575 3510.8 3550.5 3585.6 3634.2 3655.7 3647.2 3682.9 3723.1 3798.6
SD 335.7 321.6 305.1 305.7 291.1 271.3 286.1 282.3 276.7 264
N 21 21 20 20 20 20 19 18 18 18
%Diff -1.7 -2.3 -2.6 -3.1 -3.5 -3.2 -4.4 -4.5 -3.8 -3
200 mg/kg/day (Group 4) Mean 3669.8 3588.9 3458.3 3472.5 3541.8 3562.1 3620.6 3690.5 3757.7 3797.2
SD 370.3 338.1 342.8 354 353.4 357.7 337.8 350.7 339.7 350.3
N 21 21 20 20 16 16 15 15 15 15
%Diff 0.9 -0.1 -5.1 -6.1 -6 -5.7 -5.1 -4.3 -2.9 -3

Anova & Dunnett

Table 3 Summary of Body Weight Gains (g): Gestation

Sex: Female Day Relative to Mating (Litter A)
  6 ¿ 9 [G] 9 ¿ 12 [G1] 12 ¿ 15 [G] 15 ¿ 18 [G] 18 ¿ 21 [G] 21 ¿ 24 [G] 24 ¿ 27 [G] 27 ¿ 29 [G] 6 ¿ 29 [G1]
0 mg/kg/day (Group 1) Mean 67.5 54.7 67.3 10 38.2  40.4 13.0 13 47.9 339
SD 41.9 46.2 72.2 65.4 50.1 51.3 79.5 44.2 184.2
N 21 21 21 21 21 21 21 21 21
20 mg/kg/day (Group 2) Mean 53.4 54.7 67.7 20.2 35 28 49.1 57.8 366
SD 53.5 40.3 90.6 52.9 58.8 72.7 66.7 53.6 210.3
N 21 21 21 21 21 21 21 21 21
60 mg/kg/day (Group 3) Mean 23.1*  35.1 48.6 21.5 -11* 54.4 40.2 75.5 306.1
SD 38.9 38.3 74.7 70 41.3 44.5 69.5 32.4 128.1
N 20 20 20 20 19 18 18 18 18
200 mg/kg/day (Group 4) Mean -128.9**  14.2*  39.1 20.3 27.5 69.9 67.3 39.5 206.3
SD 61.9 63.3 84.6 72.7 61.4 65.8 58 56.9 159.4
N 20 20 16 16 15 15 15 15

15

[G] - Anova & Dunnett; * = p = 0.05; ** = p = 0.01

[G1] - Kruskal-Wallis & Dunn; * = p = 0.05

Table 4 Summary of Food Consumption (Food Mean Daily Consumption (g/animal/day))

Sex: Female Day Relative to Mating (Litter A)
  6 ¿ 9 [G] 9 ¿ 12 [G1] 12 ¿ 15 [G] 15 ¿ 18 [G] 18 ¿ 21 [G] 21 ¿ 24 [G] 24 ¿ 27 [G] 27 ¿ 29 [G] 6 ¿ 29 [G1]
0 mg/kg/day (Group 1) Mean 134.14 131.38 93.03 83.79 113.21 106.05 80.27 91.33 104.71
SD 23.9 23.58 45.74 42.23 35.48 34.94 37.14 33.54 24.07
N 21 21 21 21 21 21 21 21 21
20 mg/kg/day (Group 2) Mean 131.56 126.08 94.49 87.75 120.84 98.95 81.38 98.83 105.25
SD 28.46 27.7 37.46 45.81 27.94 36.34 40.77 29.52 21.98
N 21 21 21 21 21 21 21 21 21
%Diff -1.93 -4.04 1.57 4.72 6.74 -6.69 1.38 8.21 0.52
60 mg/kg/day (Group 3) Mean 117.67  109.70*  65.9 69.75 93.58 95.52 87 103.11 93.76
SD 19.01 24.18 37.09 37.95 39.31 28.06 36.11 28.73 21.31
N 20 20 20 20 19 18 18 18 18
%Diff -12.28 -16.5 -29.16 -16.76 -17.34 -9.93 8.38 12.9 -10.46
200 mg/kg/day (Group 4) Mean 36.27**  53.68**  37.19**  49.10*  91.22 106.47 103.04 96.13 72.88**
SD 28.85 37.73 25.25 25.83 35.95 24.71 16.75 22.83 12.97
N 20 20 16 16 15 15 15 15 15
%Diff -72.96 -59.14 -60.03 -41.4 -19.42 0.4 28.37 5.26  -30.40

[G] - Anova & Dunnett: * = p = 0.05; ** = p = 0.01

[G1] - Kruskal-Wallis & Dunn

Table 5 Summary of Maternal Performance, Mortality, Ovarian and Uterine Examinations and Litter Observations

Sex: Female   0 mg/kg/day Group 1 20 mg/kg/day Group 2 60 mg/kg/day Group 3 200 mg/kg/day Group 4
Group Size - Females   22 22 22 22
Number of Females Pregnant [f] N+ve 22 21 21 21
% 100 95.5 95.5 95.5
Female with Live Fetuses [f] N+ve 22 21 19 19
% 100 100 90.5 90.5
Total Resorptionst [f] N+ve 0 0 2 2
% 0 0 9.5 9.5
Female with all Nonviable [f] N+ve 0 0 2 2
% 0 0 9.5 9.5
Terminal Euthanasia [f] N+ve 21 22 19 15*
% 95.5 100 86.4 68.2*
Unscheduled Death/Euthanasia [f] N+ve 1 0 3 7*
% 4.5 0 13.6 31.8*
Unscheduled Euthanasia [f] N+ve 1 * 0 2 7
% 4.5 0 9.1 31.8*
Delivered [f] N+ve 0 0 1 0
% 0 0 4.5 0
Female with Live Fetuses N+ve 21 21 18 15
% 100 100 100 100
Number of Corpora Lutea [k] Mean  11.5 10.3 10.3 10.9
SD 2.8 1.7 1.9 1.6
N 21 21 18 15
%Diff - -10 -10 -5.3
Number of Implantations [k] Mean  9.6 9 9.4 9.9
SD 3.5 2 2.5 2.1
N 21 21 18 15
%Diff - -5.9 -1.8 2.6
Pre-implantation Loss (%)[k] Mean  16.45 11.48 8.76 9.09
SD 21.04 16.13 18.33 13.98
N 21 21 18 15
%Diff - -30.21 -46.75 -44.72
Total Number of Fetuses [k] Mean  9 8.4 9.2 9.5
SD 3.5 2 2.5 2.1
N 21 21 18 15
%Diff - -6.4 2.4 5.7
Number of Live Fetuses [k] Mean  9 8.3 9.2 9.5
SD 3.5 2 2.5 2.1
N 21 21 18 15
%Diff - -6.9 2.4 5.7
Number of Dead Fetuses [k] Mean  0 0 0 0
SD 0 0 0 0
N 21 21 18 15
%Diff - - - -
Number of Early Resorptions [k] Mean  0.5 0.5 0.3 0.2
SD 0.9 0.7 0.6 0.4
N 21 21 18 15
%Diff - 0 -47 -61.8
Number of Late Resorptions [k] Mean  0.1 0.1 0 0.2
SD 0.7 0.4 0 0.4
N 21 21 18 15
%Diff -      
Total Number of Resorptions [k] Mean  0.7 0.7 0.3 0.4
SD 1.1 0.7 0.6 0.6
N 21 21 18 15
%Diff - 0 -58.3  -40
Post-implantation Loss (%) [k] Mean  6.91 8.59 2.83 4.43
SD 11.31 11.68 6.46 6.89
N 21 21 18 15
%Diff - 24.44 -58.95 -35.8
Number of Live Male Fetuses [k] Mean  4.7 4.1 4.3 5.1
SD 2.3 1.8 1.7 2.1
N 21 21 18 15
%Diff - -11.2 -8.3 10
Number of Live Female Fetuses [k] Mean  4.3 4.2 4.9 4.3
SD 1.8 1.7 1.8 1.6
N 21 21 18 15
%Diff - -2.2 14.1 1.1
Live Male Fetus/Litter (%) [k] Mean  51.39 49.06 46.62 52.93
SD 10.88 16.72 12.84 16.38
N 21 21 18 15
%Diff - -4.54 -9.29 2.99
Live Female Fetuses/Litter (%) [k] Mean  48.61 50.35 53.38 47.07
SD 10.88 17.43 12.84 16.38
N 21 21 18 15
%Diff - 3.58 9.82 -3.16
Mean Fetal Weight males (g) [G] Mean  39.55 42.3 38.57 35.35
SD 7.29 3.94 6.49 4.29
N 21 21 18 15
%Diff - 6.97 -2.47 -10.6

[f] - Fisher's Exact: * = p = 0.05

[k] - Kruskal-Wallis & Dunn

[G] - Anova & Dunnett

Table 6 Summary of Fetal Malformations - Individual Descriptions

Dose Level (mg/kg/day) Female No. Fetus No. Malformation(s)#
0 4 L6 Forepaw, Both, Hyperflexion (E)
Forepaw, Left, Ectrodactyly (E)
Forepaw, Right, Misshapen (E)
Trunk, Omphalocele (E)
Aortic arch, Narrow (V)
Heart, Musc Ventricular Septal Defect (V)
Lung Lobe, Right medial, Fused (V)
Forepaw phalanges, 1 or more, Absent (S)
Metacarpal, 1 or more, Absent (S)
Radius, Left, Absent (S)
Sternebra, 1 or more, Absent (S)
L7 Rib, 1 or more, Fused (S)
R11 Lumbar vertebra, 1 or more, Supernumerary (S)
8 L6 Heart, Large (V)
11 L2 Sternebra, 1 or more, Fused, Severe (S)
12 L4 Diaphragm, Hernia (V)
20 24 L2@ Abdomen, Distended (E)
Heart, Large (V)
25 R6 Lumbar vertebra, 1 or more, Supernumerary (S)
36 R7 Lumbar vertebra, 1 or more, Supernumerary (S)
41 L1 Diaphragm, Hernia (V)
43 R9 Lumbar vertebra, 1 or more, Supernumerary (S)
60 56$ R14 Trunk, Omphalocele (E)
60 L5 Aortic arch, Dilatation (V)
Ductus arteriosus, Narrow (V)
Ventricular wall, Left, Thick (V)
Pulmonary trunk, Narrow (V)
R12 Lumbar vertebra, 1 or more, Supernumerary (S)
61 L1 Heart, Musc Ventricular Septal Defect (V)
L4 Lumbar vertebra, 1 or more, Supernumerary (S)
200 74 R7 Intestine, Distended (V)
80 L1 Forepaw, Left, Hyperflexion (E)
Trunk, Gastroschisis (E)
Lateral ventricle, Left, Dilatation, Severe (V)*
Lumbar centrum, 1 or more, Fused (S)
Lumbar vertebra, 1 or more, Hemivertebra (S)

#: Including external (E), visceral (V) and skeletal (S) examinations.

*: Cephalic examimation.

@: Dead fetus.$: Unscheduled necropsy.

Table 7 Summary of Fetal Abnormalities by Finding

    0 mg/kg/day Group 1 20 mg/kg/day Group 2 60 mg/kg/day Group 3 200 mg/kg/day Group 4
  Number of Fetuses Examined 188 176 165 142
  Number of Fetuses Evaluated 191 179 165 145
  Number of Litters Examines 21 21 18 15
  Number of Litters Evaluated 21 21 18 15
Paw          
Forepaw, Both, Hyperflexion - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Forepaw, Left, Hyperflexion - Malformation Fetuses N (%) 0(0.00) 0(0.00)  0(0.0) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Paw/digit          
Forepaw, Left, Ectrodactyly - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Forepaw, Right, Misshapen - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Trunk          
Abdomen, Distended - Malformation Fetuses N (%) 0(0.00) 1(0.60) 0(0.00) 0(0.00)
   Litters N (%) 0(0.00) 1(4.8) 0(0.00) 0(0.00)
Trunk, Gastroschisis - Malformation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Trunk, Omphalocele - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
    0 mg/kg/day Group 1 20 mg/kg/day Group 2 60 mg/kg/day Group 3 200 mg/kg/day Group 4
  Number of Fetuses Examined 96 87 82 72
  Number of Fetuses Evaluated 191 179 165 145
  Number of Litters Examines 21 21 18 15
  Number of Litters Evaluated 21 21 18 15
Brain          
Lateral ventricle, Left, Dilatation, Severe - Malformation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(1.11)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
    0 mg/kg/day Group 1 20 mg/kg/day Group 2 60 mg/kg/day Group 3 200 mg/kg/day Group 4
  Number of Fetuses Examined 188 176 165 142
  Number of Fetuses Evaluated 191 179 165 145
  Number of Litters Examines 21 21 18 15
  Number of Litters Evaluated 21 21 18 15
Aortic arch          
Aortic arch, Dilatation - Malformation Fetuses N (%) 0(0.00) 0(0.00) 1(0.43) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)
Aortic arch, Narrow - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Artery          
Artery, Supernumerary - Variation Fetuses N (%) 0(0.00) 0(0.00) 1(0.62) 2(2.41)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 2(13.3)
Diaphragm          
Diaphragm, Hernia - Malformation Fetuses N (%) 1(0.68) 1(0.60) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 1(4.8) 0(0.00) 0(0.00)
Ductus arteriosus          
Ductus arteriosus, Narrow - Malformation Fetuses N (%) 0(0.00) 0(0.00) 1(0.43) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)
Gallbladder/bile duct          
Gallbladder, Bilobed - Variation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Gallbladder, Cyst - Variation Fetuses N (%) 1(0.43) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Gallbladder, Small - Variation Fetuses N (%) 4(1.64) 2(1.28) 1(0.43) 1(0.83)
   Litters N (%) 3(14.3) 2(9.5) 1(5.6) 1(6.7)
Gallbladder content, Abnormal consistency - Incidental Fetuses N (%) 0(0.00) 1(0.48) 0(0.00) 0(0.00)
   Litters N (%) 0(0.00) 1(4.8) 0(0.00) 0(0.00)
General          
Abdomen, Fluid filled - Variation Fetuses N (%) 1(0.34) 1(0.60) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 1(4.8) 0(0.00) 0(0.00)
Gonad          
Ovary, Both, Discolored - Incidental Fetuses N (%) 1(0.68) 0(0.00) 0(0.00) 2(1.11)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 1(6.7)
Ovary, Left, Discolored - Incidental Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 0(0.00)
Oviduct, Left, Cyst - Variation Fetuses N (%) 1(0.43) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Oviduct, Right, Cyst - Variation Fetuses N (%) 1(0.48) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Heart          
Atrium, Right, Large - Variation Fetuses N (%) 1(0.34) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Heart, Large - Malformation Fetuses N (%) 1(0.34) 1(0.60) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 1(4.8) 0(0.00) 0(0.00)
Heart, Musc Ventricular Septal Defect - Malformation Fetuses N (%) 1(0.37) 0(0.00) 1(0.51) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 1(5.6) 0(0.00)
Ventricle, Left ventricle, Large - Variation Fetuses N (%) 0(0.00) 0(0.00) 1(0.43) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)
Ventricular wall, Left, Thick - Malformation Fetuses N (%) 0(0.00) 0(0.00) 1(0.43) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)
Innominate artery          
Innominate artery, Absent - Variation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Intestine          
Intestine, Distended - Malformation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.74)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Kidney          
Renal papilla, Right, Absent - Variation Fetuses N (%) 1(0.34) 2(1.12) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 2(9.5) 0(0.00) 0(0.00)
Liver          
Lobe, Caudate process, Cyst - Variation Fetuses N (%) 0(0.00) 1(0.48) 1(0.51) 0(0.00)
   Litters N (%) 0(0.00) 1(4.8) 1(5.6) 0(0.00)
Lobe, Left medial, Supernumerary - Variation Fetuses N (%) 1(1.19) 0(0.00) 0(0.00) 1(0.83)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 1(6.7)
Lobe, Papillary process, Cyst - Variation Fetuses N (%) 1(1.19) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Lung          
Lobe, Accessory, Absent - Variation Fetuses N (%) 1(0.37) 2(1.19) 5(2.90) 1(0.74)
   Litters N (%) 1 (4.8)  2(9.5)  2(11.1) 1(6.7)
Lobe, Right medial, Fused - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Pulmonary trunk          
Pulmonary trunk, Narrow - Malformation Fetuses N (%) 0(0.00) 0(0.00) 1(0.43) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)
Spleen          
Spleen, Discolored - Incidental Fetuses N (%) 0(0.00) 1(0.68) 0(0.00) 0(0.00)
   Litters N (%) 0(0.00) 1(4.8) 0(0.00) 0(0.00)
Spleen, Small - Variation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Spleen, Supernumerary - Variation Fetuses N (%) 2(0.95) 3(1.21) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 2(9.5) 0(0.00) 0(0.00)
Ureter          
Ureter, Right, Retrocaval - Variation Fetuses N (%) 5(2.24)  5(2.86)  5(2.90)  1(0.61)
   Litters N (%) 4(19.0) 4(19.0)  4(22.2)  1(6.7)
Forelimb          
Forepaw phalanges, 1 or more, Absent - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Forepaw phalanges, 1 or more, Unossified - Variation Fetuses N (%) 2(1.12)  3(1.64)  2(1.02)  11(7.74)
   Litters N (%) 2(9.5)  3(14.3)  2(11.1)  4(26.7)
Metacarpal, 1 or more, Absent - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Metacarpal, 1 or more, Unossified - Variation Fetuses N (%) 0(0.00) 1(0.68) 0(0.00) 0(0.00)
   Litters N (%) 0(0.00) 1(4.8) 0(0.00) 0(0.00)
Radius, Left, Absent - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Ulna, Left, Misshapen - Variation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Hindlimb          
Hindpaw phalanges, 1 or more, Unossified - Variation Fetuses N (%) 23(10.08)  19(11.21)  23(12.01)  34(25.46)
   Litters N (%) 9(42.9)  6(28.6)  10(55.6)  12(80.0)
Talus, Both, Unossified - Variation Fetuses N (%) 9(3.53)  2(1.01)  1(0.51) 6(3.95)
   Litters N (%) 5(23.8)  2(9.5)  1(5.6)  4(26.7)
Talus, Left, Unossified - Variation Fetuses N (%) 1(0.37)  0(0.00)  1(0.46)  3(2.07)
   Litters N (%) 1(4.8)  0(0.0)  1(5.6)  3(20.0)
Talus, Right, Unossified - Variation Fetuses N (%) 1(0.34) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Pelvic girdle          
Ilium, Both, Misaligned - Variation Fetuses N (%) 4(2.01) 3(1.48)  6(3.32)  5(3.54)
   Litters N (%) 3(14.3)  3(14.3)  4(22.2)  5(33.3)
Pubis, Both, Unossified - Variation Fetuses N (%) 1(0.34) 0(0.00) 0(0.00) 1(0.74)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 1(6.7)
Pubis, Left, Unossified - Variation Fetuses N (%) 2(0.68) 0(0.00) 0(0.00) 1(0.61)
   Litters N (%) 2(9.5) 0(0.00) 0(0.00) 1(6.7)
Rib          
Costal cartilage, 1 or more, Fused - Variation Fetuses N (%)   0(0.00) 0(0.00) 0(0.00)
   Litters N (%)   0(0.00) 0(0.00) 0(0.00)
Rib, 1 or more, Fused - Malformation Fetuses N (%)   0(0.00) 0(0.00) 0(0.00)
   Litters N (%)   0(0.00) 0(0.00) 0(0.00)
Sternebra          
Sternebra, 1 or more, Absent - Malformation Fetuses N (%) 1(0.37) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Sternebra, 1 or more, Branched - Variation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Sternebra, 1 or more, Fused, Severe - Malformation Fetuses N (%) 1(0.48) 0(0.00) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8) 0(0.00) 0(0.00) 0(0.00)
Sternebra, 1 or more, Fused - Variation Fetuses N (%) 2(1.02) 0(0.00) 2(1.16) 1(1.67)
   Litters N (%) 2(9.5) 0(0.00) 2(11.1) 1(6.7)
Sternebra, 1 or more, Misaligned - Variation Fetuses N (%) 3(1.73) 0(0.00) 3(1.62) 1(0.61)
   Litters N (%) 2(9.5) 0(0.00) 2(11.1)  1(6.7)
Sternebra, 1 or more, Unossified - Variation Fetuses N (%) 37(16.94) 43(23.10)  39(21.99)  38(24.93)
   Litters N (%) 12(57.1) 16(76.2)  14(77.8)  12(80.0)
Sternebra, 1 or more, Incomplete ossification - Variation Fetuses N (%) 26(13.00) 17(10.26) 28(15.76)  9(6.35)
   Litters N (%) 11(52.4) 11(52.4)  10(55.6)  5(33.3)
Xiphoid cartilage, Hole - Variation Fetuses N (%) 2(1.27) 1(0.60) 0(0.00) 0(0.00)
   Litters N (%) 2(9.5) 1(4.8) 0(0.00) 0(0.00)
Supernumerary rib          
Cervical, 1 or more, Short - Variation Fetuses N (%) 3(1.93) 2(1.07)  2(1.16) 0(0.00)
   Litters N (%) 2(9.5) 2(9.5)  2(11.1) 0(0.00)
Thoracolumbar, 1 or more, Full - Variation Fetuses N (%) 97(49.95)  88(52.53)  70(38.87)  103(72.32)
   Litters N (%) 20(95.2)  19(90.5)  16(88.9)  15(100.0)
Thoracolumbar, 1 or more, Short - Variation Fetuses N (%) 50(28.97)  39(23.58)  29(20.96)  21(14.99)
   Litters N (%) 18(85.7)  17(81.0)  14(77.8)  11(73.3)
Vertebra          
Caudal vertebra, 1 or more, Incomplete ossification - Variation Fetuses N (%) 1(0.53)  2(1.16) 0(0.00) 0(0.00)
   Litters N (%) 1(4.8)  2(9.5) 0(0.00) 0(0.00)
Lumbar centrum, 1 or more, Fused - Malformation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Lumbar vertebra, 1 or more, Hemivertebra - Malformation Fetuses N (%) 0(0.00) 0(0.00) 0(0.00) 1(0.56)
   Litters N (%) 0(0.00) 0(0.00) 0(0.00) 1(6.7)
Lumbar vertebra, 1 or more, Misaligned - Variation   0(0.00) 0(0.00) 0(0.00) 1(0.56)
    0(0.00) 0(0.00) 0(0.00) 1(6.7)
Lumbar vertebra, 1 or more, Supernumerary - Malformation Fetuses N (%) 1(0.37)  3(1.67)  2(0.93) 0(0.00)
   Litters N (%) 1(4.8)  3(14.3)  2(11.1) 0(0.00)
Thoracic centrum, 1 or more, Incomplete ossification - Variation Fetuses N (%) 0(0.00) 0(0.00) 1(0.62) 0(0.00)
   Litters N (%) 0(0.00) 0(0.00) 1(5.6) 0(0.00)

[Fetuses %] - Kruskal-Wallis & Dunn

FetusesN(%) N=Group Fetal Incidence;(%)=Mean Litter % of Fetuses with the Abnormality

Conclusions:
The maternal and developmental No Observed Adverse Effect Levels (NOAEL) for DCPD were established to be 20 mg/kg/day.
Executive summary:

In this OECD 414 test guideline study, rabbits were dosed orally with 20, 60 and 200 mg/kg/day DCPD. Treatment with DCPD resulted in a significant level of maternal toxicity at 200 mg/kg/day and five females were euthanised in extremis between post-coitum Days 13 and 18 due to severely reduced or no food consumption for at least 7 consecutive days and a significant body weight loss. These females also showed erected fur, hunched posture, thin appearance and/or reduced feces production. Additionally, one female at 200 mg/kg/day was sacrificed in extremis on Day 13 post-coitum with paralysis of both the hindlegs. This finding was correlated with a dislocation of lumbar vertebra no. 7 and accumulation of dark red fluid in the same region at necropsy. No explanation was found for the dislocated vertebra. However, given the convulsions observed for another female at 200 mg/kg/day, this animal may have had convulsions as well that could have caused the dislocation of the vertebra. As such, a relationship with the test item could not be excluded. At 60 mg/kg/day, one female was sacrificed in extremis on Day 23 post-coitum, based on similar findings as observed for the females at 200 mg/kg/day (severely reduced food consumption, body weight loss and reduced feces production). Lower fetal body weights were noted at 200 mg/kg/day, mainly in male fetuses. These changes were considered related to signs of delayed ossification (unossified fore and hindpaw phalanges) noted at the same dose level. There were 2 females of the 60 and 200 mg/kg/day groups each with early resorptions only. At the incidence observed, a relationship with the test item could not be excluded. It should be noted that finding might be related to severe maternal toxicity, as these 4 females were all preterm sacrifices. The maternal and developmental No Observed Adverse Effect Levels (NOAEL) for DCPD were established to be 20 mg/kg/day based on test item-related mortality and reduced food intake and body weight loss starting at 60 mg/kg/day and the incidence of females with resorptions only starting at 60 mg/kg/day as well as lower fetal body weights combined with delayed skeletal development at 200 mg/kg/day, respectively.

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08/10/2021-23/05/2022
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Version / remarks:
Version: June 2018
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
n/a
Species:
rat
Strain:
Wistar
Remarks:
Crl: WI(Han)
Details on test animals or test system and environmental conditions:
TEST ANIMALS:
Source:Charles River Laboratories France, L'Arbresle Cedex, France.
Age at dosing: 11-15 weeks old
Weight (on the first day of dosing):182-286 g
Housing: individually housed in polycarbonate cages (Makrolon type MIII, height 18 cm) containing sterilized wooden fibers as bedding material (Lignocel S 8-15, JRS-J.Rettenmaier & Söhne GmbH + CO. KG, Rosenberg, Germany) equipped with water bottles.
Diet:Pellets SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany
Water: ad libitum
Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C
- Humidity (%): 43 to 57%
- Photoperiod (hrs dark / hrs light):12-hours light and 12-hours dark
Route of administration:
oral: gavage
Vehicle:
corn oil
Remarks:
Supplier: Sigma-Aldrich, Steinheim, Germany; Spexific gravity: 0.92
Details on exposure:
The dose volume for each animal was based on the most recent body weight measurement. The doses were given using a plastic feeding tube.
The dose formulations were stirred continuously during dosing and were dosed within 5 hours after removal from refrigerator if not used on day of preparation.
Dose pot identification via Provantis was used as additional check to verify the dosing procedure.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The design of test item analysis was based on ICH Harmonised Tripartite Guideline Q2 (R1): Validation of Analytical Procedures: Text and Methodology. November 2005.
A quantitative analysis of the test item in vehicle was performed by an ultra performance liquid chromatographic method with spectrophotometric detection (UPLC-UV) in order to determine the accuracy, homogeneity, stability and resuspension of formulations over a large concentration range.
Concentration results were considered acceptable if mean sample concentration results were within or equal to 90-110% of target concentration. Homogeneity results were considered acceptable if the coefficient of variation was = 5%. Stability results were considered acceptable if the relative difference between the stored and initial taken samples was = 10%. Resuspension homogeneity was demonstrated if the coefficient of variation is = 5%.
Calibration curves were constructed using six concentration levels. For each level, duplicate responses were used. Linear regression analysis was performed using the least squares method with a 1/concentration2 weighting factor. The coefficient of correlation (r) was > 0.99 for each curve.
The mean accuracies of the QC samples were within the criterion range of 90-110%. It demonstrated that the analytical methods were adequate for the determination of the test item in the study samples.
The concentrations analyzed in the formulations at 1 mg/mL and 200 mg/mL were in agreement with target concentrations (i.e. mean accuracies between 90% and 110%).
The formulations at 1 mg/mL and 200 mg/mL were homogeneous (i.e. coefficient of variation = 5%).
Analysis of the formulations after storage at room temperature yielded a relative difference of = 10%. The formulations were found to be stable when stored at room temperature protected from light for at least 5 hours, in a refrigerator (2-8°C) protected from light for at least 8 days, and in a freezer (= -15°C) protected from light for at least 21 days (3 weeks). Resuspension homogeneity after storage in a refrigerator for 8 days was demonstrated with a coefficient of variation of = 5%.
Details on mating procedure:
Untreated females were mated at the Supplier and were at Day 0 or 1 post-coitum on arrival at the Test Facility (Day 0 post-coitum is the day of successful mating)
Duration of treatment / exposure:
From Day 6 to Day 20 post-coitum
Frequency of treatment:
Once daily
Duration of test:
Day 6 to Day 20 post-coitum (13 days)
Dose / conc.:
0 mg/kg bw/day
Dose / conc.:
10 mg/kg bw/day
Dose / conc.:
30 mg/kg bw/day
Dose / conc.:
100 mg/kg bw/day
No. of animals per sex per dose:
22 females per dose
Control animals:
yes, concurrent vehicle
Details on study design:
Rationale for vehicle:
Trial preparations were performed to select the suitable vehicle and to establish a suitable formulation procedure. These trials were not performed as part of this study and were not used for dosing.

Rationale for test system and number of animals:
Studies in laboratory animals provide the best available basis for extrapolation tohumans and are required to support regulatory submissions. Acceptable models which do not use live animals currently do not exist. The Wistar Han rat was chosen as the animal model for this study as it is an accepted rodent
species for developmental toxicity testing by regulatory agencies. Charles River Den Bosch has historical data on the background incidence of fetal malformations and developmental variations in this species from the same strain and source. This animal model has been proven to be susceptible to the effects of developmental toxicants. The total number of animals used in this study was considered to be the minimum required to properly characterize the effects of the test item. This study has been designed such that it does not require an unnecessary number of animals to accomplish its objectives. This Study Plan was reviewed and agreed by the Animal Welfare Body of Charles River Laboratories Den Bosch B.V. within the framework of Appendix 2 of project license AVD2360020172866 approved by the Central Authority for Scientific Procedures on Animals (CCD) as required by the Dutch Act on Animal Experimentation (December 2014).

Rationale of route and dose levels:
The oral route of exposure was requested by the ECHA (European Chemicals Agency) in the Final Decision Letter following a Compliance Check (ECHA, 2020); they considered that this route was the most appropriate for hazard characterization. The dose levels were selected based on information from the findings observed in previous toxicity studies (Gulati et al., 1993; JETOC 1998; Tiley, 2020; Flick et al., 2021) conducted with Dicyclopentadiene and in an attempt to produce graded responses to the test item. Dose levels were selected in an attempt to produce graded responses to the test item. The high dose level of 100 mg/kg/day has been selected as this dose level is expected to produce some toxicity such as transient clinical signs, a reduction body weight and/or food consumption but not excessive lethality that would prevent meaningful evaluation. The mid-dose level of 30 mg/kg/day is expected to produce minimal to moderate toxicity. The low-dose level of 10 mg/kg/day should produce no observable indications of toxicity.
Maternal examinations:
All perental animals were observed for the following:

Mortality:
At least twice daily beginning upon arrival through termination/release. Except on days of receipt and necropsy where frequency was at least once daily. Animals were observed within their cage unless necessary for identification or confirmation of possible findings.

Cageside Observations:
At least once daily; starting on Day 6 post-coitum up to the day prior to necropsy. 0 to 1 hours postdose.Animals were observed within their cage unless necessary for identification or confirmation of possible findings. Cage debris was examined to detect premature birth, if applicable.

Detailed Clinical Observations:
On Days 2, 6, 15 and 21 post-coitum. Animals were removed from the cage.

Individual Body Weights:
On Days 2, 6, 9, 12, 15, 18 and 21 post-coitum. In order to monitor the health status animals may have been weighed more often. This is documented in the study raw data.

Food Consumption:
Over Days 2-6, 6-9, 9-12, 12-15, 15-18 and 18-21 post coitum.Quantitatively measured.

Water Consumption:
Regular basis throughout the study. Water consumption was monitored by visual inspection of the water bottles. Data was used for health monitoring of the animals only and therefore was not reported.

Necropsy:
Females of Group 4 (see 'Any other information on materials and methhods Table 1) on were subjected to external an external, thoracic and abdominal examination, with special attention being paid to the reproductive organs. Macroscopic abnormalities were recorded, but not collected or fixed. Ovaries and uterine horn of these animals were not dissected, only the pregnancy status was recorded. All animals (including animals sacrificed before planned necropsy were subjected to an external, thoracic and abdominal examination, with special attention being paid to the reproductive organs. All macroscopic abnormalities were recorded, collected and fixed in the appropriate fixative, together with the animal identification.
As no macroscopically visible implantation sites were present for one female in (10 mg/kg/day dose group , one female in 30 mg/kg/day dose group and pme female in 100 mg/kg/day dose group , nongravid uteri were stained using the Salewski technique in order to detect any former implantation sites.
Necropsy procedures were performed by qualified personnel with appropriate training and experience in animal anatomy and gross pathology. A veterinary pathologist, or other suitably qualified person, was available.

Organ Weights:
The thyroid gland was weighed at necropsy for all scheduled euthanasia animals. Organ weights were not recorded for animals euthanized in poor condition (three females in the (100 mg/kg/day dose group). Paired organs were weighed together. Organ to body weight ratio (using the body weight on Day 21 post-coitum) were calculated.

Tissue Collection and Preservation:
The thyroid gland and macroscopic abnormalities were collected from all animals and preserved in 10% neutral buffered formalin.

Histology:
Thyroid glands of all animals were embedded in paraffin, sectioned at a thickness of 2-4 micrometers, mounted on glass slides, and stained with hematoxylin and eosin.

Microscopic Evaluation:
Thyroid glands were examined by a board-certified toxicological pathologist with training and experience in laboratory animal pathology
Ovaries and uterine content:
Each ovary and uterine horn of all animals were dissected and examined as quickly as possible after the necropsy to determine:
- The number of corpora lutea.
- The weight of the uterus (not for animals sacrificed before planned).
- The number of implantation sites.
- The number and distribution of live and dead fetuses.
- The number and distribution of early and late resorptions.
- The sex of each fetus based on the anogenital distance, if possible (not for animals sacrificed before planned necropsy).
Blood sampling:
Blood of F0-animals (except for animals which were sacrificed in extremis) was collected on the day of scheduled necropsy (Day 21 post-coitum). Animals were not fasted overnight. Samples (1mL) were collected randomized at the discretion of the Study Director, between 7:00 and 9:00 a.m. from the jugular vein in the animal facility. After collection, samples were transferred to the appropriate laboratory for processing. Blood samples were processed for serum, and serum was analysed for the following parameters:Triiodothyronine (T3), Thyroxine (T4) and Thyroid-Stimulating Hormone (TSH).

After receipt of the serum for T3, T4 and TSH analysis it was divided in two aliquots. One aliquot was used for measurement of thyroid hormones using the IMMULITE® 1000 analyser (TSH). These samples were stored in an ultra-low freezer (set to maintain -80°C) until analysis. The other aliquot was used for measurement of T3 and T4 using LC-MS. The aliquots for T3 and T4 was collected in uniquely labelled clear 1.4 mL V-bottom Micronic polypropylene tubes and stored in a freezer (set to maintain -20°C) until analysis. Measurement was performed according to the bioanalytical method validated in Test Facility. The LC-MS analysis was based on the following guidelines:
- European Medicines Agency (EMA). Guideline on Bioanalytical Method Validation. EMEA/CHMP/EWP/192217/2009, 01 February 2012.
-Guidance for industry: Bioanalytical Method Validation, U.S. Department of Health and Human Services, Food and Drug Administration, Center for Drug Evaluation and Research (CDER) and Center for Veterinary Medicine (CVM), May 2018.
Lower limit of quantification were 0.008 uIU/mL, 0.1 ng/mL and 5.00 ng/mL for thyroid stimulating hormone (TSH), triiodothyronine (Total T3) and total thyroxine (Total T4), respectively.
Fetal examinations:
External Examinations:
Each viable fetus was sexed, examined in detail to detect macroscopic visible abnormalities and their weight (not for fetuses of animals sacrificed before planned necropsy) was determined. The anogenital distance (AGD) was measured for all viable fetuses. The AGD was normalized to the cube root of the fetal body weight.

Visceral Examinations:
The sex of all fetuses was confirmed by internal examination and approximately one-half of the fetuses (live and dead) in each litter (all groups) were examined for visceral anomalies by dissection in the fresh (non-fixed) state. The thoracic and abdominal cavities were opened and dissected. This examination included the heart and major vessels. Fetal kidneys were examined and graded for renal papillae development. The heads were removed from this one-half of the fetuses in each litter and placed in Bouin's solution for soft-tissue examination. After examination, the tissues without variations or malformations were discarded. Tissues with variations or malformations were stored in 10% formalin. Any remaining tissues (from the fetuses used for fresh visceral examination) were discarded. The carcasses were processed and stained (see described below), but were not examined in first instance.

Skeletal Examinations:
All fetuses were eviscerated, followed by fixation in 96% aqueous ethanol, and maceration in potassium hydroxide. Thereafter, they were processed for double staining with Alcian Blue 8GX and Alizarin Red S. Subsequently, skeletal examination was done for one-half of the fetuses (i.e. the fetuses with heads). All specimens were archived in glycerin with bronopol as preservative. A few bones were not available for skeletal examination because they were accidentally damaged or lost during processing. The missing bones were listed in the raw data; evaluation by the fetal pathologist and Study Director determined there was no influence on the outcome of the individual or overall skeletal examinations, or on the integrity of the study as a whole.
Statistics:
All statistical analyses were performed within the respective study phase, unless otherwise noted. Numerical data collected on scheduled occasions were summarized and statistically analyzed as indicated in 'Any other information on materials and methods' according to sex and occasion or by litter (Table 1).
Means, standard deviations (or % coefficient of variation or standard error, when deemed appropriate), ratio, percentages, numbers, and/or incidences were reported as appropriate by dataset.
All statistical tests were conducted at the 5% significance level. All pairwise comparisons were conducted using two sided tests and were reported at the 1% or 5% levels. The following pairwise comparisons were made:
Group 2 vs. Group 1
Group 3 vs. Group 1
Group 4 vs. Group 1
Analyses were performed according to the table 2 under 'Any other information on materials and methods' below when possible but excluded any group wit less than 3 observations.
Parametric/Non-Parametric::
Levene’s test was used to assess the homogeneity of group variances. The groups were compared using an overall one-way ANOVA F-test if Levene’s test was not significant or the Kruskal-Wallis test if it was significant. If the overall F-test or Kruskal Wallis test was found to be significant, then pairwise comparisons were conducted using Dunnett’s or Dunn’s test, respectively.
Non-Parametric:
The groups were compared using an overall Kruskal-Wallis test. If the overall Kruskal Wallis test was found significant, then the above pairwise comparisons were conducted using Dunn’s test.
ANCOVA:
The data corresponding to a response variable of interest and to a related covariate were submitted to an analysis of covariance (ANCOVA), including only groups with at least three non-missing paired values and if found to be significant, then pairwise comparisons were conducted using Dunnett’s test.
Incidence:
A Fisher’s exact test was used to conduct pairwise group comparisons of interest.
Indices:
n/a
Historical control data:
Charles River Den Bosch has historical data on the background incidence of fetal malformations and developmental variations in this species from the same strain and source. This animal model has been proven to be susceptible to the effects of developmental toxicants.
Clinical signs:
no effects observed
Description (incidence and severity):
In the 100 mg/kg/day group no clinical signs were observed. All but one female were pregnant. Due to unscheduled deaths in the 100 mg/kg/day group, the maternal findings of these animals were not evaluated for the remaining endpoints.
No clinical signs of toxicity were noted during the observation period at 10 and 30 mg/kg/day. All clinical signs noted during the Dosing Period occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study and did not show any apparent dose-related trend. At the incidence observed, these were considered to be unrelated to treatment with the test item.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, treatment-related
Description (incidence):
At 100 mg/kg/day, no females survived until scheduled necropsy: three animals were sacrificed in extremis on Days 8 or 9 post-coitum, based on a body weight loss of 13-15% between Day 6 and 9 post-coitum and/or low food consumption.
The remaining animals were sacrificed ad interim (on Days 7, 8, 9 or 10 post-coitum, depending on mating date) based on body weight loss.
No mortality was noted at 10 and 30 mg/kg/day.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
At 30 mg/kg/day, lower body weight gain was noted over Days 6-9 post-coitum (Table 1). After this period comparable body weight gain to control was observed. At the end of the Dosing Period (Day 21 post-coitum), mean body weights were 3.5% lower than control (not statically significant) (Table 2). Mean body weight gain corrected for gravid uterus weight was slightly lower than control (Table 3). Given magnitude and in absence of statistical significance, this was considered not toxicologically relevant.
At 10 mg/kg/day, mean body weight gain and body weight gain corrected for gravid uterus remained in the same range as control over the Dosing Period.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
At 30 mg/kg/day, reduced food consumption was noted over Days 6-9 post-coitum (17% lower than control) (Table 4). After this period, slightly reduced food consumption (not statistically significant) was noted, except on Days 12-15 post-coitum. Overall food consumption during the dosing period was 6% lower than in control (not statistically significant).
At 10 mg/kg/day, food consumption was similar to the control level over the Dosing Period.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not specified
Description (incidence and severity):
One female in the 10 mg/kg/day dose group and one female in the 30 mg/kg/day dose group were not gravid and were therefore excluded from the data analysis.
At 30 mg/kg/day, increased T3 levels were observed (1.19x of control) (Table 5). As this increase was observed at the high dose, a test item-related effect could not be excluded. However, the mean value remained within the historical control data. Serum levels of Total T4 levels up to 30 mg/kg/day and Total T3 at 10 mg/kg/day were considered to be unaffected by treatment with the test item due to the minimal magnitude of the change.
Decreased serum levels of TSH were noted at 10 and 30 mg/kg/day (0.80 and 0.79x of control, respectively; not statistically significant), and means remained within the historical control data (Table 5). Although no dose response was observed, a test item-related effect could not be excluded.
Urinalysis findings:
not specified
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
There were no test item-related alterations in thyroid gland weights up to 30 mg/kg/day.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No macroscopic findings were noted in any of the animals in the 100 mg/kg/day group.
Macroscopic observations at necropsy did not reveal any alterations that were considered to have arisen as a result of treatment with the test item in the 10mg/kg/day and 30 mg/kg/day dose groups. There were no test item-related gross observations in the thyroid glands. The heart findings (enlargement, pale and tan discoloration, and adhesion of the left ventricle to the diaphragm and lungs) in one female in the 10 mg/kg/day dose group were considered related to the gavage procedure and were interpreted as not test item-related.
All other findings that were noted among control and/or treated animals were considered to be of no toxicological significance, since they remained within the range of biological variation for rats of this age and strain.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
There were no test item-related microscopic observations in the thyroid glands.
The recorded microscopic findings in the thyroid gland were within the range of background pathology encountered in rats of this age and strain.
Histopathological findings: neoplastic:
not specified
Details on results:
As all females at 100 mg/kg/day were sacrificed in extremis or ad interim, only data up to the mid dose of 30 mg/kg/day are mentioned below.
Number of abortions:
not specified
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
At 10 mg/kg/day, pre-implantation loss was higher than control (11.35 vs. 8.62%, not statistically significant) (Table 6). Furthermore, post-implantation was higher than control (8.74 vs. 4.44%, not statistically significant). At 30 mg/kg/day, pre- and post-implantation loss was similar to control and in the range of normal biological variation. As no dose-response was observed, the higher pre- and post-implantation loss at 10 mg/kg/day were considered not related to treatment with test item.
Total litter losses by resorption:
not specified
Early or late resorptions:
not specified
Dead fetuses:
not specified
Changes in pregnancy duration:
not specified
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
At 100 mg/kg/day, all females were pregnant, except for one.
All females, except for one in the 10 mg/kg/day dose group and one in the 30 mg/kg/day dose group were gravid and had litters with live fetuses (Table 6).
The numbers of pregnant females, corpora lutea and implantation sites in the control and at 10 and 30 mg/kg/day were similar and in the range of normal biological variation.
Other effects:
not examined
Key result
Dose descriptor:
NOAEL
Effect level:
30 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
body weight and weight gain
Key result
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
There were no test item-related effects on fetal body weights (both sexes) noted by treatment with the test item up to 30 mg/kg/day (Table 6).
Reduction in number of live offspring:
not examined
Changes in sex ratio:
no effects observed
Description (incidence and severity):
The male:female ratio was considered unaffected by treatment with the test item up to 30 mg/kg/day.
Changes in litter size and weights:
no effects observed
Description (incidence and severity):
There were no test item-related effects on litter size up to 30 mg/kg/day.
Anogenital distance of all rodent fetuses:
no effects observed
Description (incidence and severity):
There were no test item-related effects on fetal anogenital distance (both sexes) noted after treatment with the test item up to 30 mg/kg/day.
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
There were no external malformations and variations observed up to 30 mg/kg/day.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
There were no skeletal malformations observed at 30 mg/kg/day. Three fetuses, one control and two low-dose (10 mg/kg/day) fetuses had skeletal malformations (Table 7 and 9). At 10 mg/kg/day, bent limb bones (humerus, radius and ulna) occurred in one fetus that also showed sternoschisis. The latter finding was also noted in one control fetus, while another low-dose fetus had a bent humerus. Due to the incidental occurrence in control and/or 10 mg/kg/day fetuses these were considered chance findings. All skeletal variations occurred in the absence of a dose-related incidence trend, infrequently and/or in control fetuses only. Therefore, they were considered not related to the test-item.
Visceral malformations:
no effects observed
Description (incidence and severity):
There were no visceral malformations observed up to 30 mg/kg/day and in groups that received the test-item, only supernumerary liver lobes were noted at low incidences without any indication to a test-item effect (Table 8).
Visceral variations in this study affected the urogenital tract of a single control fetus.
Other effects:
not examined
Details on embryotoxic / teratogenic effects:
n/a
Key result
Dose descriptor:
NOAEL
Effect level:
>= 30 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No abnormalities observed at 30 mg/kg/day but data not available for the next highest dose (100 mg/kg/day) due to excessive maternal mortality
Key result
Abnormalities:
no effects observed
Key result
Developmental effects observed:
no

Table 1 Summary of Body Weight Gains (g): Gestation

Sex: Female   Day(s) Relative to Mating (Litter: A)
    6 ¿ 9 9 ¿ 11 9 ¿ 12 12 ¿ 15 11 ¿ 15 15 ¿ 18 18 ¿ 21 6 ¿ 21
0 mg/kg/day (Group 1) Mean 10.9 12.2 16.7 16.4 19.7 32 36.2 111
SD 4.2 4.3 3.8 4.8 5 7.1 8.1 19.8
N 22 17 16 16 17 22 22 22
10 mg/kg/day (Group 2) Mean 11.5 11.9 16.8 15.9 19.9 29.6 33.5 106.8
SD 5.2 3 3.3 6.2 6.9 9 15.1 29.6
N 21 15 17 17 15 21 21 21
30 mg/kg/day (Group 3) Mean 4.6**  13.3 16.9 17.6 22.2 28 31.9 99
SD 6.8 5 5.9 6.2 6.9 5.6 8 14.7
N 21 15 21 21 15 21 21 21
100 mg/kg/day (Group 4) Mean -24.9 - - - - - - -
SD 6.9 - - - - - - -
N 10 - - - - - - -

Anova & Dunnett: ** = p = 0.01

Table 2 Summary of Body Weights: Gestation

Sex: Female   Day(s) Relative to Mating (Litter: A)
    2 (G) 5 (G1) 6 (G) 7(G) 8(G) 9(G) 10(G) 11(G) 12(G) 13(G) 15(G) 18(G) 21
0 mg/kg/day (Group 1) Mean 218.3 224.8 234.7 230.2 243 245.6 251.2 258.9 2260.1 259.8 277.5 309.5 345.7
SD 14.8 11.4 15.2 12.9 17.4 16.6 16 17.3 14.1 15.1 18.7 24.6 30.8
N 22 5 22 5 11 22 22 17 16 6 22 22 22
10 mg/kg/day (Group 2) Mean 223 233.7 238.3 241.2 246.2 249.8 255 261.5 266 272.4 282 311.6 345.1
SD 12 11.2 12.2 11.5 12.5 10.7 11.8 11.4 10.5 6.9 13.7 17.8 29.4
N 21 6 21 6 10 21 21 15 17 5 21 21 21
%Diff 2.2 3.9 1.5 4.8 1.3 1.5 1.5 1 2.3 4.8 1.6 0.7 -0.2
30 mg/kg/day (Group 3) Mean 218.1 238.2 234.7 243.2 235.6 239.3 245.8 249 256.1 260.4 273.7 301.8 333.6
SD 25.5 12.2 25.8 23 26.7 26.8 27 29.8 26.7 29.3 28.6 31.2 36.2
N 21 6 21 11 16 21 21 15 21 5 21 21 21
%Diff -0.1 5.9 0 5.6 -3 -2.6 -2.2 -1.5 -1.5 0.2 -1.4 -2.5 -3.5
100 mg/kg/day (Group 4) Mean 214 - 231.2 216.5 204.1** 210** 213.5* - - - - - -
SD 14.2 - 14.8 17.3 14.3 13.7 15.1 - - - - - -
N 21 - 21 10 11 10 4 - - - - - -
%Diff -1.7 - -1.5 -6 -16 -14.5 -15 - - - - - -

[G] - Kruskal-Wallis & Dunn: * = p = 0.05; ** = p = 0.01

[G1] - Anova & Dunnett

Table 3 Summary of Gravid Uterine Weights and Gravid Uterus Adjusted Body Weights: Gestation

Sex: Female 0 mg/kg/day (Group 1) 10 mg/kg/day (Group 2) 30 mg/kg/day (Group 3)
Day(s) Relative to Mating (Litter: A)
Bodyweight on Day 6 (g) [G] Mean 234.7 238.3 234.7
SD 15.2 12.2 25.8
N 22 21 21
%Diff - 1.5 0
Terminal Body Weight (g) [G1] Mean 345.7 345.1 333.6
SD 30.8 29.4 36.2
N 22 21 21
%Diff - -0.2 -3.5
Gravid Uterus Weight (g) [G1] Mean 72.77 72.15 69.35
SD 19.46 22.79 12.51
N 22 21 21
%Diff - -0.85 -4.7
Adjusted BWG (6-abw) (g) [G1] Mean 38.23 34.66 29.6
SD 15.29 14.95 7.71
N 22 21 21
%Diff - -9.34 -22.57

[G] - Kruskal-Wallis & Dunn

[G1] - Anova & Dunnett

Table 4 Summary of Food Mean Daily Consumption (g/animal/day)

Sex: Female   Day(s) Relative to Mating (Litter: A)
    6 ¿ 9 [G] 9 ¿ 12 [G] 12 ¿ 15 [G] 15 ¿ 18 [G1] 18 ¿ 21 [G] 6 ¿ 21 [G]
0 mg/kg/day Group 1 Mean 19.74 21.32 22.21 22.74 22.59 21.72
SD 2.16 2.24 3.56 2.56 4.32 2.17
N 22 22 22 22 22 22
10 mg/kg/day Group 2 Mean 19.16 21.44 23.62 21.48 21.71 21.48
SD 2.04 2.1 3.13 4.78 4.94 2.42
N 21 21 21 21 21 21
%Diff -2.96 0.59 6.33 -5.57 -3.88 -1.1
30 mg/kg/day Group 3 Mean 16.37** 19.98 22.44 21.54 21.46 20.36
SD 2.47 2.64 3.32 4.34 2.5 2.31
N 21 21 21 21 21 21
%Diff -17.11 -6.26 1.05 -5.29 -5 -6.27
100 mg/kg/day Group 4 Mean 6.72** - - - - -
SD 2.63 - - - - -
N 6 - - - - -
%Diff -65.95 - - - - -

[G] - Anova & Dunnett: ** = p = 0.01

[G1] - Kruskal-Wallis & Dunn

Table 5 Summary of Thyroid Hormone Values ( Day: 21 Relative to Mating (Litter: A)

Sex: Female   Reporting Special Chemistry
  T3 (ng/mL) [G] T4 (ng/mL) [G] TSH (mU/L) [G]
0 mg/kg/day Group 1 Mean 0.359 22.86 0.2345
SD 0.085 4.44 0.125
N 22 22 22
10 mg/kg/day Group 2 Mean 0.404 24.24 0.1887
SD 0.095 5.6 0.1238
N 21 21 21
tCtrl 1.12 1.06 0.8
30 mg/kg/day Group 3 Mean 0.428 *  25.45 0.1847
SD 0.095 5.12 0.0942
N 21 21 21
tCtrl 1.19 1.11 0.79

[G] - Anova & Dunnett: * = p = 0.05

Table 6 Summary of Ovarian and Uterine Examinations and Litter Observations

Sex: Female   0 mg/kg/day (Group 1) 10 mg/kg/day (Group 2) 30 mg/kg/day (Group 3)
Female with Live Fetuses N+ve 22 21 21
% 100 100 100
Number of Corpora Lutea [k] Mean 12.4 13.2 11.7
SD 2.5 2.1 2.3
N 22 21 20
%Diff - 6.7 -5.7
Number of Implantations [k] Mean 11.3 11.7 10.6
SD 2.7 2.8 2.2
N 22 21 21
%Diff - 3.9 -5.8
Pre-implantation Loss (%) [k] Mean 8.62 11.35 8.56
SD 14.69 17.37 11.52
N 22 21 20
%Diff - 31.72 -0.66
Total Number of Fetuses [k] Mean 10.7 10.8 10.1
SD 2.6 3.5 22
N 22 21 21
%Diff - 0.3 -5.4
Post-implantation Loss (%) [k] Mean 4.44 8.74 4.68
SD 8.55 20.63 7.33
N 22 21 21
%Diff - 96.91 5.41
Number of Live Male Fetuses [k] Mean 6 5.9 5
SD 2.2 2.9 2.3
N 22 21 21
%Diff - -2.4 -16.7
Number of Live Female Fetuses [k] Mean 4.7 4.9 5.1
SD 2 2.3 2.2
N 22 21 21
%Diff - 3.8 8.8
Live Male Fetus/Litter (%) [k] Mean 55.69 54.81 48.94
SD 15.34 23.49 20.09
N 22 21 21
%Diff - -1.58 -12.13
Live Female Fetuses/Litter (%) [k] Mean 44.31 45.19 51.06
SD 15.34 23.49 20.09
N 22 21 21
%Diff - 1.99 15.25
Mean Fetal Weight males (g) [G] Mean 5.073 4.974 5.123
SD 0.315 0.579 0.306
N 22 20 21
%Diff - -1.953 0.995
Mean Fetal Weight females (g) [G] Mean 4.824 4.849 4.897
SD 0.36 0.531 0.225
N 22 20 21
%Diff - 0.534 1.527
Mean Fetal Weight all (g) [G] Mean 4.949 4.889 5.003
SD 0.305 0.552 0.259
N 22 21 21
%Diff - -1.224 1.086
Mean Fetal AGD males (mm) [G1]] Mean 2.6 2.58 2.62
SD 0.33 0.35 0.31
N 22 20 21
%Diff - -0.99 0.85
Mean Fetal AGD females (mm) [G1] Mean 1.14 1.2 1.11
SD 0.13 0.4 0.1
N 22 20 21
%Diff - -0.99 0.85
Mean Normalized Fetal AGD m [G] Mean 1.516 1.509 1.524
SD 0.195 0.173 0.183
N 22 20 21
%Diff - -0.448 0.509
Mean Normalized Fetal AGD f [G] Mean 0.676 0.711 0.654
SD 0.077 0.215 0.061
N 22 20 21
%Diff - 5.158 -3.288

[k] - Kruskal-Wallis & Dunn

[G] - Anova & Dunnett

Table 7 Summary of Malformations – Individual Descriptions

Dose Level (mg/kg/day) No. of Fetuses Malformation(s)#
0 1 Sternebra, 1 or more, Sternoschisis (S)
10 1 Humerus, Both, Bent (S); Radius, Both, Bent (S); Ulna, Both, Bent (S); Sternebra, 1 or more, Sternoschisis (S)
1 Humerus, Right, Short (S)

Table 8 Summary of Fetal Visceral Abnormalities by Finding

    0 mg/kg/day Group 1 10 mg/kg/day Group 2 30 mg/kg/day Group 3
  Number of Fetuses Examined 119 113 104
  Number of Fetuses Evaluated 236 226 213
  Number of Litters Examined 22 20 21
  Number of Litters Evaluated 22 21 21
Kidney        
Renal papilla, Both, Absent - Variation

Fetuses N (%)

Litters N (%)

1 (0.65)

1 (4.5)

0 (0.00)

0 (0.0)

0 (0.00)

0 (0.0) 
Liver        
Lobe, Left medial, Supernumerary - Variation

Fetuses N (%)

Litters N (%)

3 (3.68)

3(13.6)

 2 (1.71)

2 (10.0)

1 (1.19)

1 (4.8) 

Lobe, Right medial, Supernumerary - Variation

Fetuses N (%)

Litters N (%)

 0 (0.0)

0 (0.0)

 1 (1.00)

1 (5.0)

 3 (3.73)

3 (14.3)

 Spleen

 

 

 

 
 Spleen, Discoloured - Incidental

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 1 (1.00)

1 (5.0)

 0 (0.00)

0 (0.0)
 Ureter        
 Ureter, Both Convoluted - Variation

Fetuses N (%)

Litter N (%)

 1 (0.65)

1 (4.5)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

 Ureter, Both, Dilation, Minimal - Variation

Fetuses N (%)

Litters N (%)

 1 (0.65)

1 (4.5)

0 (0.00)

0 (0.0)

0 (0.00)

0 (0.0)
 Urinary bladder        
 Urinary bladder, Distended - Variation

Fetuses N (%)

Litters N (%)

 1 (0.65)

1 (4.5)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

[Fetuses %] - Kruskal-Wallis & Dunn

FetusesN(%) N=Group Fetal Incidence;(%)=Mean Litter % of Fetuses with the Abnormality

Table 9 Summary of Fetal Skeletal Abnormalities by Finding

        0 mg/kg/day Group 1   10 mg/kg/day Group 2   30 mg/kg/day Group 3

 

Number of Fetuses Examined

Number of Fetuses Evaluated

Number of Litters Examined

Number of Litters Evaluated

 

117

236

22

22

113

226

21

21

 

109

213

21

21

 
 Pelvic girdle        
 Ilium, Both, Misaligned - Variation

Fetuses N (%)

Litters N (%)

 6 (6.82)

4 (18.2)

2 (1.75)

2 (9.5) 

5 (4.17)

5 (23.8) 
 Rib        
 Costal cartilage, 1 or more, Fused - Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

 1 (0.85)

1 (4.8)

 Rib, 1 or more, Wavy rib - variation

Fetuses N (%)

Litters N (%)

 6 (5.19)

5 (22.7)

 16 (180.3)

9 (42.9)

 4 (3.46)

3 (14.3)
 Scapula        
 Scapula, Both, Bent - Variation

Fetuses N (%)

Litters N (%)

  0 (0.00)

0 (0.0)

 2 (5.44)

2 (9.5)

 0 (0.00)

0 (0.0)
 Scapula, Right, Bent- Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 1 (0.79)

1 (4.8)

 0 (0.00)

0 (0.0)
 Skull        
 Intraparietal, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

  (7.58)

6 (27.3)

 8 (6.83)

6 (28.6)

 1 (0.95)

1 (4.8)

 Parietal, Both, Incomplete Ossification - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 2 (1.90)

1 (4.8)

0 (0.00)

0 (0.0)

 Parietal, Left, Incomplete sssification - Variation

Fetuses N (%)

Litters N (%)

 1 (0.91)

1 (4.5)

 2 (1.59)

2 (9.5)

 0 (0.00)

0 (0.0)

 Parietal, Right, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 1 (0.79)

1 (4.8)

0 (0.00)

0 (0.0) 

 Squamosal, Left, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

(0.0)

 1 (0.79)

1 (4.8)

 0 (0.00)

0 (0.0)

 Squamosal, Right, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 1 (0.91)

1 (4.5)

0 (0.00)

0 (0.0) 

 0 (0.00)

0 (0.0)

 Suture bone, Supernumerary site - Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

1 (1.19)

1 (4.8) 

 Zygomatic arch, Left, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

1 (0.95)

1 (4.8) 

 0 (0.00)

0 (0.0)

 Zygomatic arch, Right, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

 1 (0.95)

1 (4.8)

 Sternebra

 

 

 

 

 Sternebra, 1 or more, Misaligned -Variation

Fetuses N (%)

Litters N (%)

 3 (2.32)

3 (13.6)

 3 (2.50)

3 (14.3)

 2 (2.14)

2 (9.5)

 Sternebra, 1 or more, Sternoschisis - Malformation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 1 (4.76)

1 (4.8)

 0 (0.00)

0 (0.0)

 Sternebra, 1 or more, Unossified- Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 0 (0.00)

0 (0.0)

 0 (0.00)

0 (0.0)

 Sternebra, 1 or more, Wide - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 1 (4.76)

1 (4.8)

(0.00)

0 (0.0)

 Sternebra, 1 or more, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 2 (1.67)

2 (9.1)

 5 (7.59)

4 (19.0)

 0 (0.00)

0 (0.0)

 Supernumerary rib

 

 

 

 

 Cervical, 1 or more, Full - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 0 (0.00)

0 (0.0)

0 (0.00)

0 (0.0) 

 Cervical, 1 or more, Short - Variation

Fetuses N (%)

Litters N (%)

 4 (3.94)

4 (18.2)

 7 (8.5)

5 (23.8)

 8 (7.35)

6 (28.6)

Thorocolumbar, 1 or more, Full - Variation

Fetuses N (%)

Litters N (%)

 10 (7.36)

4 (18.2)

 14 (11.96)

10 (47.6)

 14 (12.15)

8 (38.1)

 Thoracolumbar, 1 or more, Short - Variation

Fetuses N (%)

Litters N (%)

 78 (66.87)

22 (100.0)

 78 (69.25)

21 (100.0)

 69 (65.11)

19 (90.5)

 Vertebra

 

 

 

 

 Thoracic centrum, 1 or more , Split - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 0 (0.00)

0 (0.0)

 1 (0.68)

1 (4.8)

 Thoracic centrum, 1 or more, Split - Variation

Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 3 (1.98)

2 (9.5)

 4 (3.23)

3 (14.3)

 Thoracic centrum, 1 or more, Incomplete ossification - Variation

Fetuses N (%)

Litters N (%)

 

 

 

Forelimb

 

 

 

 

Humerus, Both, Bent - Malformation

 Fetuses N (%)

Litters N (%)

 0 (0.0)

0 (0.0)

 1 (4.76)

1 (4.8)

 0 (0.00)

0 (0.0)

 Humerus, Right, Short - Malformation

 Fetuses N (%)

Litters N (%)

 0 (0.00)

0 9).0)

1 (0.68)

1 (4.8) 

 0 (0.00)

0 (0.0)

 Metacarpal, 1 or more, Unossified - Variation

 Fetuses N (%)

Litters N (%)

 1 (0.76)

1 (4.5)

 0 (0.00)

0 (0.0)

0 (0.00)

0 (0.0) 

  Radius, Both, Bent - Malformation

 Fetuses N (%)

Litters N (%)

 0 (0.00)

0 9).00)

 1 (4.76)

1 (4.8)

 0 (0.00)

0 (0.0)

 Ulna, Both, Bent - malformation

Fetuses N (%)

Litters N (%)

 0 (0.00)

0 (0.0)

 1 (4.76)

1 (4.8)

 0 (0.00)

0 (0.0)

[Fetuses %] - Kruskal-Wallis & Dunn

FetusesN(%) N=Group Fetal Incidence;(%)=Mean Litter % of Fetuses with the Abnormality

Conclusions:
The maternal No Observed Adverse Effect Level (NOAEL) for DCPD was established to be 30 mg/kg/day and the developmental NOAEL to be at least 30 mg/kg/day.
Executive summary:

In this OECD 414 study, rats were dosed orally with 10, 30 and 100 mg/kg/day DCPD. No females survived until scheduled necropsy in the 100 mg/kg/day dose group due to excessive body weight loss and/or low food consumption. No mortality was noted at 10 and 30 mg/kg/day. No clinical signs of toxicity were observed at any dose group. Due to unscheduled deaths in the 100 mg/kg/day group, the maternal findings of these animals and fetal findings were not evaluated for the remaining endpoints and no effects on the maternal endpoints examined under the OECD 414 test guideline were observed in the 10 and 30 mg/kg/day dose groups. No effects on pre- and post-implantation loss, number of pregnant animals,corpora lutea and implantation sites in the 10 and 30 mg/kg/day dose groups were not affected by the treatment. There were no skeletal malformations observed at 30 mg/kg/day, however, one fetus in the control and two in the 10 mg/kg/day dose group had skeletal malformations. Due to the incidental occurrence in control and/or 10 mg/kg/day fetuses these were considered chance findings. All skeletal variations occurred in the absence of a dose-related incidence trend and infrequently . Therefore, they were considered not related to the test-item. No effects were observed on fetal body weights, sex ratio, litter size, fetal anogenital distance, external or visceral malformations in the 10 and 30 mgkg/day dose groups. Therefore, the maternal No Observed Adverse Effect Level (NOAEL) for DCPD was established to be 30 mg/kg/day based on excessive weight loss at the next highest dose (100 mg/kg/day) and the developmental NOAEL to be at least 30 mg/kg/day as no fetal abnormalities were observed at 30 mg/kg/day but no data were available for the next highest dose (100 mg/kg/day) due to excessive maternal mortality

Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
20 mg/kg bw/day
Study duration:
subchronic
Species:
rabbit
Quality of whole database:
OECD 414 studies in rat and rabbit (Klimisch score = 1) are available, which meet the EU REACH Annex X requirments. OECD 422 study in rats is also available as additional information.
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

Non-human information:

In the OECD 414 study, rats were dosed orally with 10, 30 and 100 mg/kg/day DCPD. No females survived until scheduled necropsy in the 100 mg/kg/day dose group due to excessive body weight loss and/or low food consumption. No mortality was noted at 10 and 30 mg/kg/day. No clinical signs of toxicity were observed at any dose group. Due to unscheduled deaths in the 100 mg/kg/day group, the maternal findings of these animals and fetal findings were not evaluated for the remaining endpoints and no effects on the maternal endpoints examined under the OECD 414 test guideline were observed in the 10 and 30 mg/kg/day dose groups. No effects on pre- and post-implantation loss, number of pregnant animals,corpora lutea and implantation sites in the 10 and 30 mg/kg/day dose groups were not affected by the treatment. There were no skeletal malformations observed at 30 mg/kg/day, however, one fetus in the control and two in the 10 mg/kg/day dose group had skeletal malformations. Due to the incidental occurrence in control and/or 10 mg/kg/day fetuses these were considered chance findings. All skeletal variations occurred in the absence of a dose-related incidence trend and infrequently . Therefore, they were considered not related to the test-item. No effects were observed on fetal body weights, sex ratio, litter size, fetal anogenital distance, external or visceral malformations in the 10 and 30 mgkg/day dose groups. Therefore, the maternal No Observed Adverse Effect Level (NOAEL) for DCPD was established to be 30 mg/kg/day based on excessive weight loss at the next highest dose (100 mg/kg/day) and the developmental NOAEL to be at least 30 mg/kg/day as no fetal abnormalities were observed at 30 mg/kg/day but no data were available for the next highest dose (100 mg/kg/day) due to excessive maternal mortality

In another OECD 414 test guideline study in rabbits, treatment with DCPD resulted in a significant level of maternal toxicity at 200 mg/kg/day and five females were euthanised in extremis between post-coitum Days 13 and 18 due to severely reduced or no food consumption for at least 7 consecutive days and a significant body weight loss. These females also showed erected fur, hunched posture, thin appearance and/or areduced feces production. Additionally, one female at 200 mg/kg/day was sacrificed in extremison Day 13 post-coitum with paralysis of both the hindlegs. This finding was correlated with a dislocation of lumbar vertebra no. 7 and accumulation of dark red fluid in the same region at necropsy. No explanation was found for the dislocated vertebra. However, given the convulsions observed for another female at 200 mg/kg/day, this animal may have had convulsions as well that could have caused the dislocation of the vertebra. As such, a relationship with the test item could not be excluded.At 60 mg/kg/day, one female was sacrificedin extremison Day 23 post-coitum, based on similar findings as observed for the females at 200 mg/kg/day (severely reduced food consumption, body weight loss and reduced feces production). Lower fetal body weights were noted at 200 mg/kg/day, mainly in male fetuses. These changes were considered related to signs of delayed ossification (unossified fore and hindpaw phalanges) noted at the same dose level.There were 2 females of the 60 and 200 mg/kg/day groups each with early resorptions only. At the incidence observed, a relationship with the test item could not be excluded. It should be noted that finding might be related to severe maternal toxicity, as these 4 females were all preterm sacrifices.The maternal and developmental No Observed Adverse Effect Levels (NOAEL) for DCPD were established to be 20 mg/kg/day based on test item-related mortality and reduced food intake and body weight loss starting at 60 mg/kg/day andthe incidence of females with resorptions only starting at 60 mg/kg/day as well as lower fetal body weights combined with delayed skeletal development at 200 mg/kg/day, respectively.

A developmental toxicity study with dicyclopentadiene (DCPD) in Sprague-Dawley rats was conducted using the dietary route of oral exposure (Litton Bionetics, 1978). This is considered to be the key study and includes standard (guideline) methods of evaluation. Dietary concentrations of 0, 80, 250 or 750 ppm were fed to groups of 20 time-mated rats on days 6-15 of gestation (where day 0 was the day of confirmation of mating). There was no maternal toxicity and no developmental toxicity at any dietary level and therefore 750 ppm was a NOAEL.

According to the BG Chemie Toxicological Evaluation No. 84 (Dicyclopentadiene), the highest concentration (750 ppm) was judged equivalent to a daily intake of 150 mg/kg body weight at an assumed feed intake of 200 g/Kg body weight/day. Consideration of the reported food and body weight data for days 6-15 of gestation indicates that females of 250 g body weight consuming 20 g diet would receive 60 mg DCPD/kg body weight/day. On the basis of this study, the oral (dietary) NOAEL for maternal and developmental toxicity is 60 mg/Kg/day.

Limited data are available for the oral (gavage) route of administration of dicyclopentadiene. Dose range finding studies have been conducted in pregnant rats and rabbits (Gulati, 1993). These provide data on maternal toxicity but little information on developmental toxicity because there was no visceral or skeletal examination of the foetuses. Groups of 11 time-mated rats were dosed with 0, 50, 200, 300, 400 or 500 mg/Kg/day on days 6-15 of gestation (where day 0 was the day of confirmation of mating). Dose levels of 300 mg/Kg/day or more caused maternal lethality; a single death occurred in the 200 mg/kg bw/day group. Reduced body weight gain was observed in females given 50 or 200 mg/kg bw/day. Lower foetal weight was associated with 200 mg/Kg/day but not with 50 mg/kg bw/day. A NOAEL for maternal toxicity was not established in this study.

 

Groups of 10 mated New Zealand White rabbits were dosed with 0, 25, 100, 200, 300 or 400 mg/kg/ bw/day on days 6-19 of gestation (where day 0 was the day of mating). Signs of systemic toxicity and lethality were observed in the 300 and 400 mg/kg bw/day groups. Maternal body weight gain was reduced in the 200 mg/kg bw/day group. The abortion of one litter in the 100 mg/kg bw/day group occurred in the absence of a statistically-significant reduction in maternal body weight, and no data for food consumption is provided in this DRF study. Consequently, it is uncertain if the abortion seen in one dam at 100 mg/kg was due to a direct effect of DCPD on the foetuses in this litter, or as the consequence of maternal toxicity at 100 mg/kg.

There are no developmental toxicity studies available using the dermal or inhalation routes of exposure to dicyclopentadiene. 

Human information:

There are no human data available for developmental effects of dicyclopentadiene in humans.

Toxicity to reproduction: other studies

Description of key information

n/a

Additional information

n/a

Mode of Action Analysis / Human Relevance Framework

n/a

Justification for classification or non-classification

Based on the overall weight of evidence, DCPD meets the criteria for classification as a reproductive toxicant (Repr. 2; H361; suspected of damaging fertility or the unborn child) under the Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP) based upon foetotoxic effects such as reduced pup body weight, increased pup mortality, and decreased pup survival observed in rodents at oral doses equal to or below those that produced significant maternal toxicity in adult females.

Additional information