6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde

Endpoint summary

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Effects on fertility

Description of key information

Under the conditions of the test (OECD 422, GLP), the systemic NOAEL was determined to be at least 120 mg/kg bw/day. The fertility NOAEL is 60 mg/kg bw based on decreased fertility at 120 mg/kg bw/day.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

60 mg/kg bw/day

Study duration:

subacute

Species:

rat

Additional information

Introduction and method: The substance was tested in a Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD 422) following GLP. The dose levels in this study were selected to be 0, 30, 60, 120 mg/kg/day, based on the results of the Dose Range Finder in which mortality was observed at 450 mg/kg/day but no severe effects were recorded at 90 mg/kg/day. The test item and vehicle were administered once daily by oral gavage 7 days a week for a minimum of 29 days. Males were treated for 29 days, up to and including the day before scheduled necropsy. This included a minimum of 14 days prior to mating and during the mating period. Females that delivered were treated for 50 to 57 days, i.e. 14 days prior to mating (with the objective to cover at least two complete estrous cycles), the variable time to conception, the duration of pregnancy and at least 13 days after delivery, up to and including the day before scheduled necropsy.

Parameters measured: Mortality/moribundity, clinical signs, functional observations, body weight and food consumption, estrous cycle determination, clinical pathology, measurement of thyroid hormone T4 (F0-males), gross necropsy findings, organ weights and histopathologic examinations. In addition, the following reproduction/developmental parameters were determined: mating and fertility indices, precoital time, number of implantation sites, gestation index and duration, parturition, maternal care, sex ratio and early postnatal pup development (mortality, clinical signs, body weights, sex, anogenital distance, areola/nipple retention and macroscopy, measurement of thyroid hormone T4 (PND 14-16 pups)).

Results: Mortality: One female (No. 52) at 30 mg/kg/day was found dead on Day 7 post-coitum. No clinical signs were observed that were associated with its death. At necropsy beginning autolysis, a soft urinary bladder wall (probably a result of autolysis) and many dark red foci on the thymus were recorded. There were no microscopic observations indicating the cause of death. At the isolated incidence observed and with the absence of a dose-related trend, this death was considered an incidental occurrence rather than related to treatment with the test item.

Clinical signs: No toxicologically significant changes were noted.

Functional observation tests: No toxicologically significant changes were noted.

Body weight: No toxicologically significant changes were noted.

Food consumption: No toxicologically significant changes were noted.

Haematology and clotting parameters: No effects observed.

Clinical chemistry: Decreased total protein concentrations in males starting at 60 mg/kg/day were considered non-adverse in the absence of corroborating findings.

Hormone levels: Male T4 thyroid hormone levels were not affected.

Organ weights and histopathology: Relationships were suspected between enlarged liver, increased liver weight and hepatocellular hypertrophy. The (mainly periportal) hepatocellular hypertrophy in females at 60 and 120 mg/kg/day and males at 120 mg/kg/day was considered non-adverse at the current severities (minimal to slight) and in the absence of any degenerative findings. Therefore, the higher liver weights (up to 19%) in males and females were considered non-adverse.

Fertility: Fertility index was adversely affected at 120 mg/kg/day, with a fertility index of 50%. In the Dose Range Finder significant treatment-related changes were recorded for sperm parameters at 450 mg/kg/day (reduced mean motile sperm, mean progressive motility, mean number of cells with normal morphology and mean number of cells with coiled tail, and increased mean number of cells with detached head and mean number of cells with abnormal neck). Epididymal sperm count was not considered affected by treatment. These findings were not recorded at 90 mg/kg/day. These extensive sperm analyses were not performed in the current study so it cannot be excluded that any of the abovementioned abnormalities were present at 120 mg/kg/day as well and could (partly) account for the decreased fertility index. No reproduction toxicity was observed up to 60 mg/kg/day. The two non-pregnancies in the mid dose group were considered to be within normal ranges of biological variation. In this study, no treatment-related changes were noted in any of the remaining reproductive parameters investigated in this study (i.e. mating index, precoital time, number of implantations, estrous cycle, spermatogenic profiling, and histopathological examination of reproductive organs).

Conclusion: In conclusion, based on the results of this combined 28-day repeated dose toxicity study with the reproduction/developmental toxicity screening test, the following no-observed-adverse effect level (NOAEL) were established within the current study: Parental NOAEL is at least 120 mg/kg/day. The reproduction NOAEL is 60 mg/kg/day based on decreased fertility index at 120 mg/kg/day.

Effects on developmental toxicity

Description of key information

Under the conditions of the test (OECD 422, GLP), the systemic NOAEL was determined to be at least 120 mg/kg bw/day. The developmental NOAEL is >= 60 mg/kg bw (the high dose was not evaluated as there were insufficient litters).

Effect on developmental toxicity: via oral route

Dose descriptor:

NOAEL

60 mg/kg bw/day

Study duration:

subacute

Species:

rat

Toxicity to reproduction: other studies

Additional information

Introduction and method: The substance was tested in a Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD 422) following GLP. The dose levels in this study were selected to be 0, 30, 60, 120 mg/kg/day, based on the results of the Dose Range Finder in which mortality was observed at 450 mg/kg/day but no severe effects were recorded at 90 mg/kg/day. The test item and vehicle were administered once daily by oral gavage 7 days a week for a minimum of 29 days. Females that delivered were treated for 50 to 57 days, i.e. 14 days prior to mating (with the objective to cover at least two complete estrous cycles), the variable time to conception, the duration of pregnancy and at least 13 days after delivery, up to and including the day before scheduled necropsy.

Parameters measured: Mortality/moribundity, clinical signs, functional observations, body weight and food consumption, estrous cycle determination, clinical pathology, gross necropsy findings, organ weights and histopathologic examinations. In addition, the following reproduction/developmental parameters were determined: mating and fertility indices, precoital time, number of implantation sites, gestation index and duration, parturition, maternal care, sex ratio and early postnatal pup development (mortality, clinical signs, body weights, sex, anogenital distance, areola/nipple retention and macroscopy, measurement of thyroid hormone T4 (PND 14-16 pups)).

Results: Mortality: One female (No. 52) at 30 mg/kg/day was found dead on Day 7 post-coitum. No clinical signs were observed that were associated with its death. At necropsy beginning autolysis, a soft urinary bladder wall (probably a result of autolysis) and many dark red foci on the thymus were recorded. There were no microscopic observations indicating the cause of death. At the isolated incidence observed and with the absence of a dose-related trend, this death was considered an incidental occurrence rather than related to treatment with the test item.

Clinical signs: No toxicologically significant changes were noted.

Functional observation tests: No toxicologically significant changes were noted.

Body weight: No toxicologically significant changes were noted.

Food consumption: No toxicologically significant changes were noted.

Haematology and clotting parameters: No effects observed.

Clinical chemistry: No toxicologically significant changes were noted

Organ weights and histopathology: Relationships were suspected between enlarged liver, increased liver weight and hepatocellular hypertrophy. The (mainly periportal) hepatocellular hypertrophy in females at 60 and 120 mg/kg/daywas considered non-adverse at the current severities (minimal to slight) and in the absence of any degenerative findings. Therefore, the higher liver weights (up to 19%) in were considered non-adverse.

Fertility: Fertility index was adversely affected at 120 mg/kg/day, with a fertility index of 50%. No reproduction toxicity was observed up to 60 mg/kg/day. The two non-pregnancies in the mid dose group were considered to be within normal ranges of biological variation. In this study, no treatment-related changes were noted in any of the remaining reproductive parameters investigated in this study (i.e. mating index, precoital time, number of implantations, estrous cycle, spermatogenic profiling, and histopathological examination of reproductive organs).

Developmental toxicity: No adverse developmental toxicity was observed at 30 and 60 mg/kg/day. Developmental data was available of only 7 and 5 females in the mid and high dose group, respectively. One animal in the mid dose group was pregnant but fetuses were resorbed. As the other litters in the mid dose group showed consistent results, developmental parameters could be evaluated despite a slightly low number of litters in this group (< 8 litters). The 5 litters for the high dose group were considered too limited for a toxicological evaluation. At 60 mg/kg/day pup body weights (both sexes) were decreased compared with control from PND 1 onwards. As body weights partly recovered from PND 1 up to PND 13 (from 15.6% to 9.3%) this difference was considered non-adverse. No toxicologically significant changes were noted in any of the remaining developmental parameters investigated in this study (i.e. gestation, viability and lactation indices, duration of gestation, parturition, sex ratio, maternal care, litter size and early postnatal pup development consisting of mortality, clinical signs, anogenital distance, areola/nipple retention, T4 thyroid hormone levels and macroscopic examination).

Conclusion: In conclusion, based on the results of this combined 28-day repeated dose toxicity study with the reproduction/developmental toxicity screening test, the following no-observed-adverse effect level (NOAEL) were established within the current study: Parental NOAEL is at least 120 mg/kg/day. The reproduction NOAEL is 60 mg/kg/day based on decreased fertility index at 120 mg/kg/day. The developmental NOAEL is at least 60 mg/kg/day as the highest dose could not be evaluated as there were only 5 litters.

Justification for classification or non-classification

Based on the results of the Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD 422) the substance has to be classified for fertility as Category 2: H361 (Suspected of damaging fertility) according to EU CLP (EC 1272/2008 and its amendments).

Based on the results of the Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD 422) the substance does not have to be classified for developmental toxicity according to EU CLP (EC 1272/2008 and its amendments).