OO-tert-butyl O-(2-ethylhexyl) peroxycarbonate

Toxicity to reproduction

Administrative data

Endpoint:

extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)

Type of information:

experimental study planned

Study period:

The study will be conducted in 2021 or later depending on ECHAs final decision oon the testing proposal

Justification for type of information:

TESTING PROPOSAL ON VERTEBRATE ANIMALS

NON-CONFIDENTIAL NAME OF SUBSTANCE:
OO-tert-butyl O-(2-ethylhexyl) peroxycarbonate, CAS 34443-12-4, EC 252-029-5


CONSIDERATIONS THAT THE GENERAL ADAPTATION POSSIBILITIES OF ANNEX XI OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
- Available GLP studies : No toxicity to reproduction studies which cover the Annex X requirement (OECD 443 or equivalent study) for CAS 34443-12-4 are available.
- Available non-GLP studies : No toxicity to reproduction studies which cover the Annex X requirement (OECD 443 or equivalent study) for CAS 34443-12-4 are available.
- Historical human data : The registrant is not aware of human data for the endpoint toxicity to reproduction.
- (Q)SAR : A QSAR calculation is not sufficient to cover the endpoint toxicity to reproduction as requested by Annex X of the REACH Regulation.
- In vitro methods : No data for 34443-12-4 available. No acceptable in vitro method is available to cover the endpoint toxicity to reproduction as requested by Annex X of the REACH Regulation.
- Weight of evidence : No data for a weight of evidence approach are available.
- Grouping and read-across : The substance registration is covered within the organic peroxide consortium and is part of the subgroup Peroxymonocarbonates. None of the group members is registered in Annex X, thus no data for the endpoint toxicity to reproduction as requested by Annex X of the REACH Regulation is available. A possible read-across to the similar group of Peroxydicarbonates also is not possible as there are also no data for the requested endpoint.
CONSIDERATIONS THAT THE SPECIFIC ADAPTATION POSSIBILITIES OF ANNEXES VI TO X (AND COLUMN 2 THEREOF) OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
Annex X Column 2 specific rules for adaptation for this endpoint are not applicable for the registered substance

FURTHER INFORMATION ON TESTING PROPOSAL IN ADDITION TO INFORMATION PROVIDED IN THE MATERIALS AND METHODS SECTION:
Extended one-generation reproductive toxicity study (Annex X, Section 8.7.3.; test method: EU B.56./OECD TG 443) in rats, oral route with the registered substance specified as follows:
- Ten weeks premating exposure duration for the parental (P0) generation
- Dose level setting shall aim to induce some toxicity at the highest dose level
- Cohort 1A (Reproductive toxicity)
- Cohort 1B (Reproductive toxicity) without extension to mate the Cohort 1B animals to produce the F2 generation
For justification of the test design see below in the field “Justification of study design”.

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 443 (Extended One-Generation Reproductive Toxicity Study)

Justification for study design:

SPECIFICATION OF STUDY DESIGN FOR EXTENDED ONE-GENERATION REPRODUCTION TOXICITY STUDY WITH JUSTIFICATIONS:

- Premating exposure duration for parental (P0) animals

Ten weeks premating exposure duration for the parental (P0) generation as recommended by ECHA. This is the default value as specified by ECHA in recent decisions on OECD 443 studies.

- Basis for dose level selection

The dose level setting shall aim to induce some toxicity at the highest dose level. As no screening study (e.g. OECD 421 or 422) with the registered substance is available a pre-test (similar to OECD 422) will be needed to properly set the dose levels for the main study.

- Inclusion/exclusion of extension of Cohort 1B

This cohort is a standard requirement of the OECD 443 guideline. Cohort 1B (Reproductive toxicity) will be included without extension to mate the Cohort 1B animals to produce the F2 generation.

Based on the available data there is no indication that organs for reproduction are negatively affected by the test item as shown in the OECD 408 study.
There may be an effect on vagina which is considered as non adverse:
Mucification of vaginal mucosa was observed in 3/10 high-dose, 2/10 mid-dose and 1/10 low-dose females. Other females in these groups displayed a normal distribution of estrous cycle assessed histologically. With the exception of one high-dose female, all these rats had prolonged diestrus. However, prolonged diestrus was also observed in two control rats without vaginal mucification. The mean duration of diestrus was only marginally increased at the high-dose, without statistical significance. Overall, vaginal mucification is possibly related to treatment at the high-dose only, and could represent an indirect non-adverse effect of the test item. The effects seen in vagina disappeared after the recovery period.
Estrus cycle
There were no statistically significant test item-related effects on the mean length of the estrus cycle or the mean number of cycles. A trend towards an increase in the mean length of diestrus was observed in females given 600 mg/kg/day at the end of the treatment period. This was due to two high-dose females for which the diestrus period represented 13 to 14 days. This was considered to be of minor importance in the absence of statistical significance and as microscopic findings (marked mucification of vaginal mucosa for the same two females) were considered to be an indirect, non-adverse effect of the test item and as these variations were no longer observed at the end of the treatment-free period. Other differences observed in the diestrus duration for females given 100 or 300 mg/kg/day (i.e. 8.4 and 8.5 days vs. 7.0 days in controls) were considered to be of no toxicological importance as there was no clear relationship between the cycle length and the severity of the vaginal mucosa mucification.
Seminology
No test item-related effects were noted on testicular sperm count, or on epididymal sperm count, motility or morphology. The lower values in the epididymal (only statistically significant at 300 mg/kg/day) and/or testicular sperm counts recorded in males given 300 or 600 mg/kg/day were considered to be of no toxicological importance as they resulted from slightly higher mean control values (due to one male: 162.4 10E6/g of testis and 26.6 10E6/g of testis/day), as most of individual values were within the standard deviation of the control group, and/or as differences were of minor magnitude and/or not dose-related.

In conclusion, mating of cohort 1B to produce F2 generation is not required. If on the other hand effects in F1 generation are observed or equivocal findings would need clarification, inclusion of F2 generation will be considered to be included.
The developmental toxicity study in rats showed that pre- and post-implantation loss, total litter loss by resorption, early/late resorption, pregnancy parameter (number of animals, duration) were not affected by test item treatment.

- Termination time for F2

F2 generation is not planned to be included in the study design (see above)

- Inclusion/exclusion of developmental neurotoxicity Cohorts 2A and 2B

Cohorts 2A and 2B are not planned to be included in the study design. There are no adverse effects observed in the previous OECD 408 study which might trigger the inclusion of Cohort 2A and 2B.
There were no test item-related effects on functional observation battery tests or motor activity data in any group. Higher mean numbers of horizontal movements and rearing were noted in males at 300 and 600 mg/kg/day; they were considered to be of no toxicological importance as they were of minor magnitude (not statistically significant), poorly dose-related and/or as values remained within the standard deviation of control values. No differences from controls were noted in the motor activity of test item-treated females. Differences from controls in landing foot splay were noted in males and females at 600 mg/kg/day (69 mm and 88 mm vs. 79 mm and 99 mm in control males and females, respectively). In view of the very slight magnitude, and in the absence of correlating clinical signs during the study, this finding was considered to be unrelated to the test item treatment.

- Inclusion/exclusion of developmental immunotoxicity Cohort 3

Cohort 3 is not planned to be included in the study design. There are no adverse effects observed in the previous OECD 408 study which might trigger the inclusion of Cohort 3. There were no changes in organ weight of organs related to immunotoxcicity (like spleen or thymus). In addition, there were no relevant changes in hematology/clinical chemistry parameter and no gross pathology/histopathology findings in organs related to immunotoxicity.

- Route of administration

Standard route of administration is oral via gavage. All previous repeated dose data were obtained via this route of administration.

- Other considerations, e.g. on choice of species, strain, vehicle and number of animals

Standard species is the rat. It is intended to use the same rat strain as used in previous studies (Sprague-Dawley or Wistar) depending on the historical control database in the selected CRO. All other parameters will be done as recommended by the OECD guideline.

Test material

Test material information

Constituent 1

Reference substance name:

OO-tert-butyl O-(2-ethylhexyl) peroxycarbonate

EC Number:

252-029-5

EC Name:

OO-tert-butyl O-(2-ethylhexyl) peroxycarbonate

Cas Number:

34443-12-4

Molecular formula:

C13H26O4

IUPAC Name:

3-({[(tert-butylperoxy)carbonyl]oxy}methyl)heptane

Test material form:

liquid

Test animals

Species:

rat