tert-butyl peroxypivalate

Endpoint summary

Description of key information

 

A study to according OECD 408/GLP was performed with the structural analogue tert-butyl 3,5,5-tris(methylperoxy)hexanoate (TBPIN, CAS 13122 -18 -4). The test item was administered by oral gavage at 10, 40 and 160 mg/kg bw/day to rats. No adverse effects were observed up to the high dose level. A NOAEL of 160 mg/kg bw/day in males and female rats was determined.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the Read-Across Justification attached to IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEL

Effect level:

160 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: no adverse effects observed at the highest dose tested

Key result

Dose descriptor:

NOEL

Effect level:

10 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

clinical signs

histopathology: non-neoplastic

Key result

Dose descriptor:

NOEL

Effect level:

< 10 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

clinical signs

Key result

Critical effects observed:

no

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

160 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

OECD 408/ GLP (Read-Across)

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Oral route

Key (OECD 408)

No subchronic study with the target substance tert-butyl 2,2-dimethylpropaneperoxoate (TBPPI) is available. However, a study performed with the structural analogue tert-butyl 3,5,5-tris(methylperoxy)hexanoate (TBPIN, CAS 13122 -18 -4) is available:

TBPIN, a structure analogue of the target substance, was administered at three dose levels over a prolonged period of time (90 days) followed by a 28-day recovery period orally (by gavage) to Hsd.Brl.Han: Wistar rats (n=15 animals/sex in the control and high dose groups, n= 10 animals/sex in the low and middle dose groups). Doses of 160, 40 and 10 mg/kg bw/day corresponding to concentrations of 0, 32, 8 and 2 mg/mL were applied in a dose volume of 5 mL/kg bw daily. 5 animals/ sex in the control and high dose groups were observed without administration for four weeks (recovery observations). A sufficient stability of the substance in the chosen vehicle was analytically verified up front. The substance was stable in the applied concentrations in sunflower oil at room temperature for 4 hours and in a refrigerator for 3 days. Concentrations of the test item in the dosing formulations varied from 99 % to 106 % of nominal concentrations at both analytical occasions, thereby confirming proper dosing. Animals were observed for mortality twice a day in the course of the study. Daily general clinical observations and weekly detailed clinical observations were performed. A functional observation battery was conducted in the last week of treatment. The body weight and food consumption were measured and evaluated weekly. Clinical pathology examinations (including hematology and clinical chemistry) and gross pathology were conducted one day after the last treatment and at the end of the recovery period. The absolute and relative weights of selected organs were measured. Full histopathology was performed on the preserved organs or tissues of the animals of the control and high dose groups including recovery groups. The kidneys were also evaluated histologically in all animals of the low and mid dose groups due to the necropsy and histopathological findings in the high dose group.

The results of study were interpreted comparing test item treated groups with respect to controls, which were administered concurrently with vehicle only.

There was no test item related mortality. One control female rat died on Day 39 due to individual disease. There were no preceding clinical signs or body weight changes. Histological examinations revealed pulmonary alterations (acute alveolar emphysema, multifocal hemorrhages in the lungs), circulatory disturbances (passive hyperemia in the organs) in connection with a probable suffocation as the cause of death and a focal subchronic perihepatitis accompanied with local fibrosis in one of the liver lobes as an individual disease.

Toxic signs related to the test item were not detected at any dose level at the daily and detailed weekly clinical observations and in the course of the functional observation battery. Salivation was observed in the male and female animals of the 160 or 40 mg/kg bw/day groups with variable frequency within a group but in a dose related manner regarding the incidence and onset.

The body weight development of male and female animals was not affected by the test item. No test item-related body weight, or body weight gain changes were observed with respect to controls at any dose level during the course of the study.

The daily mean food consumption was similar in animals of the control and test item treated groups (160, 40 and 10 mg/kg bw/day).

There were no abnormalities in the eyes of animals in the high dose group at termination of the treatment.

A test item influence on the estrous cycle was not detected.

No test item-related changes were observed in investigated hematology or blood coagulation parameters.

Clinical chemistry examinations did not reveal any pathologic changes in the examined parameters.

The kidneys were judged to be pale in some animals (male and female) of 160 mg/kg bw/day groups and in two female animals at 10 mg/kg bw/day at the terminal necropsy. The liver was enlarged, pale and nutmeg-like patterned in several animals of 160 mg/kg bw/day group and in single male animals of 40 and 10 mg/kg bw/day groups. Since kidney and liver weight values remained within the historical control ranges and there were no related histopathological lesions in the kidneys and the liver these changes were considered to be signs of adaptation of the organ to the altered demands.

The mean liver and kidney weights (absolute and relative to the body and brain weights) were higher with respect to their controls in the male and female animals of 160 mg/kg bw/day group. Similar findings were also noted for the higher mean liver weight relative to body weight in male animals of 40 and 10 mg/kg bw/day groups and for the higher mean kidney weights relative to body and brain weights of male animals at 40 mg/kg bw/day. Although these differences reached statistical significances with respect to controls, all values remained within the historical control ranges.

Sperm analysis did not reveal test item influence on the sperm cells (count, motility and morphology) at 160 mg/kg bw/day dose.

Histopathology investigations revealed test item related hyaline –like droplets in the epithel cells of some proximal convoluted tubules in the kidney of male animals treated with 160, 40 and 10 mg/kg bw/day, which was accompanied by dilatation of tubuli in the distal area, at the border of cortical – medullary region at 160 and 40 mg/kg bw/day. The severity of the lesions decreased in the low dose group as compared with the middle or high dose groups. The renal lesion was not present at the end of the recovery period and no additional renal lesions or increased cell turnover were determined. In accordance with literature data (ECETOC, 2002) the isolated and reversible finding hyaline-like droplets in male rats has to be considered as a toxicological relevant, but not adverse effect.

Immunohistochemistry examinations demonstrated lower level of α2μ-globulin in male animals of the 160 mg/kg bw/day compared with control animals, therefore the presence of α2μ-globulin in the kidneys of male animals was deemed to reflect the normal physiological situation. Therefore, hyaline-like droplets at 160, 40 and 10 mg/kg bw/day doses in male rats could not be caused by α2μ-globulin.

Under the conditions of the present study TBPIN caused salivation (male and female) at 160 and 40 mg/kg bw/day, and reversible hyaline-like droplets at 160, 40 and 10 mg/kg bw/day doses in male Hsd.Brl.Han: Wistar rats after the consecutive 90-day oral (gavage) administration. Based on these observations the No Observed (Adverse) Effect Level (NO(A)EL) was determined as follows:

NOEL: < 10 mg/kg bw/day for male animals

NOEL: 10 mg/kg bw/day for female animals

NOAEL: 160 mg/kg bw/day for male and female animals

Supporting study (OECD 422)

The purpose of this Combined Repeated Dose Toxicity Study with the Reproduction/Developmental toxicity screening test was to provide initial information concerning the toxic potential of TBPPI and on its possible effects on male and female reproductive performance such as gonadal function, mating behavior, conception, pregnancy, parturition as well as on development of the F1 offspring from conception to day 4 post-partum associated with oral administration to rats at repeated doses. Four groups of Hsd.Brl.Han:Wist rats (n=12/sex/group) were administered orally (by gavage) once a day at 0 (vehicle only), 50, 150 and 310 mg/kg bw/day at concentrations of 25 mg/mL, 75 mg/mL and 155 mg/mL, corresponding to 2 mL/kg bw dose volume. The suitability of the chosen vehicle for the test item at the intended concentrations was analytically verified up front. TBPPI was stable at room temperature for 24 hours and in a refrigerator (5 ± 3 °C) for 3 days. Concentration of the test item in the dosing formulations varied in the range of 98 % to 104 % in comparison to the nominal values, thereby confirming proper dosing. All animals of the parent (P) generation received test item or vehicle prior to mating (14 days) and throughout mating. Test item or vehicle was administered to male animals post mating up to the day before the necropsy. For females with living pups, test item was administered through the gestation period and up to lactation days 3 – 6, i.e. up to the day before the necropsy. Observations included mortality, clinical signs, body weight, food consumption, mating, pregnancy and delivery process, as well as development of pups. Five dams and males cohabited with were selected from each group for further toxicity examinations such as functional observations, hematology, clinical chemistry, gross necropsy, organ weighing and histopathology. The dams were allowed to litter, and rear their young up to termination on days 4 – 7 postpartum. Pups were weighed and observed for possible abnormalities. All parental animals were subjected to gross pathology one day after the last treatment and offspring were euthanized. Selected organs were weighed. Full histopathology was performed in the selected animals of control and high dose groups. Histopathology examination was performed on reproductive organs and pituitary of the remaining animals in the control and high dose groups. The reproductive organs and pituitary of non-pregnant female animals and males cohabited with in the low and mid dose groups were also processed and evaluated histologically. The results were interpreted comparing treatment groups with respect to controls, which were treated concurrently with vehicle (sunflower oil) only.

There was no test item related mortality at any dose level (310, 150 and 50 mg/kg bw/day). Test item related salivation appeared in male and female animals administered with 310 and 150 mg/kg bw/day groups with a dose related onset and incidence. No toxic signs related to the test item were found at the detailed weekly and terminal functional observations. The behavior and physical condition of animals were normal during the entire observation period (pre-mating, mating, post-mating, gestation and lactation periods). The body weight gain was reduced with respect to controls at 310 mg/kg bw/day in male animals during the entire observation period (with statistical significances on weeks 1, 2, 3 and 6 and if summarized) and in dams during lactation period. These changes resulted in a slightly less body weight in the range of -5 to -7 % in male animals with respect to control from day 20 up to the termination and -13 % in dams on lactation day 4. The mean daily food consumption was slightly less comparing to the control group at 310 and 150 mg/kg bw/day doses during first week of premating period (male), during the premating (female) and at 310 mg/kg bw/day between lactation days 0 and 4. Hematology examinations did not reveal any test item related changes in the evaluated hematological parameters at any dose level (310, 150 and 50 mg/kg bw/day). No test item-related changes were observed in investigated clinical chemistry parameters for the male animals. In the female animals treated with 310 mg/kg bw/day, the glucose (GLUC) concentration was slightly but significantly below the value of control and historical control ranges in this treatment group and a test item related effect cannot be ruled out. However, as the reduction in GLUC was very slight, the finding was considered to be of no toxicological concern. Specific macroscopic alterations related to the test item were not found during the necropsy. A test item influence on renal function was observed as mean weights of kidneys (absolute, and relative to body and brain weights) were slightly higher with respect to the controls and above the historical control ranges in male animals at 310 mg/kg bw/day dose. The increases in absolute, relative to body, and brain weights were determined to be 26, 31 and 23%, respectively. Histopathology investigation did not detect any microscopic changes related to the test item effect. There were no differences between the control and test item treated groups in the reproductive performance of male and female animals and in delivery data of dams.

Under the conditions of the present study, TBPPI caused salivation (male and female), changes in body weight (male and female), food consumption (male and female), slightly reduced glucose concentration (female) and elevated kidney weights (male) following an oral administration at 310 mg/kg bw/day to Hsd.Brl.Han:Wistar rats during the Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test. At 150 mg/kg bw/day, salivation and slightly reduced food consumption were observed in male and female animals. At 50 mg/kg bw/day, no test item related adverse effects were observed. Based on these observations the No Observed Adverse Effect Levels (NOAEL) were determined as follows: NOAEL for male and female rats: 150 mg/kg bw/day.

Supporting study OECD 421

A modified OECD 421 study in rats was performed with TBPPI. The purpose of this study was to obtain information on the possible effects of the test item on reproduction and development when repeatedly administered orally (by gavage) to rats at doses of 100, 250 and 350 mg/kg bw/day compared to control animals receiving vehicle only. Four groups of Han:WIST rats (n=12/sex/group) were administered with the test item orally (by gavage) once a day at 0 (vehicle), 100, 250 and 350 mg/kg bw/day doses corresponding to concentrations of 0, 50 mg/mL, 125 mg/mL and 175 mg/mL. The application volume was 2 mL/kg bw. Control animals received the vehicle, sunflower oil. The suitability of the vehicle at the intended concentrations of the test item was analytically verified up front (concentration and homogeneity). The concentration of the test item in the dosing formulations used for animal’s treatment was checked three times during the study. Concentration of TBPPI-75-AL in the dosing formulations varied between the range of 90 % and 108 % of the nominal values and formulations were homogenous thereby confirming the proper dosing. All animals of the parent (P) generation were dosed prior to mating (70 days) and throughout mating. In addition, males received the test item or vehicle after mating up to the day before the necropsy (altogether for 100 days). Dams were additionally exposed through the gestation period and up to lactation days 21-23 (altogether for 114, 115, 118 or 125 days). Non-pregnant female animals and dam not delivered were administered for 95, 97, 98 or 102 days. Observations included mortality, clinical signs, body weight, food consumption, mating, pregnancy and delivery process, as well as development of offspring. Estrous cycle was monitored by examining vaginal smears for two weeks before the start of mating period and during the mating period until evidence of mating and on the day of the necropsy. The dams were allowed to litter and rear their offspring up to day 21 - 23 post-partum then were subjected to necropsy on post-partum day 22 - 24. Litters were weighed and offspring were observed for possible abnormalities. One or two male and one or two female pups per litter were selected on post-natal day 21 and were separated and administered (2 mL/kg bw/day) from postnatal day 22 up to and including post-natal day 35. Clinical signs were observed daily after the treatment and body weight was determined twice weekly and were recorded. The food consumption was determined by weekly interval. All selected pups were subjected to macroscopic necropsy observation on post-natal day 36. Remaining pups were euthanized on post-natal day 22. Blood samples were collected for determination of serum levels of thyroid hormones (FT4, TSH) from 2-5 pups per litter (except for litters with 9 or less pups) on post-natal day 4, from all dams and from 3-6 pups per litter on post-partum/post-natal day 22 and from all parent male animals at termination. Non-pregnant female animals and dam not giving birth were sampled for thyroid hormone determination at termination on the day of the necropsy (Days 95, 97, 98 or 102). All parental animals were subjected to gross pathology one day after the last treatment. The ovaries, uterus with oviduct and cervix, vagina, testes, epididymides (total and cauda), prostate, and seminal vesicles with coagulating glands and thyroid glands of all adult animals were preserved. In addition, organs with macroscopic findings were also preserved for a possible histological examination. A quantitative examination of the ovaries was performed in all female animals in the control and high dose groups. The body weight, brain weight, weight of the testes, epididymides and prostate and seminal vesicles with coagulating glands as a whole of all adult male animals were determined.

There was no mortality at any dose level (100, 250 or 350 mg/kg bw/day). Clinical signs of systemic toxicity related to the test item were not detected at any dose level at the daily clinical observations. The behavior and physical condition of the animals was not impaired at any dose level (100, 250 or 350 mg/kg bw/day) during the entire treatment period. Salivation and nuzzling up the bedding material observed at 250 and 350 mg/kg bw/day were with short duration after the administration of the test item therefore these signs were considered to be toxicologically not relevant.

The body weight development was depressed in male animals at 250 and 350 mg/kg bw/day during the pre-mating, mating and post-mating periods. The difference with respect to the control was lower than 10 % at 250 mg/kg bw/day therefore was judged to be toxicologically not relevant.

The mean daily food consumption was slightly reduced in male animals at 350 mg/kg bw/day in accordance with the body weight changes during the entire treatment period. Estrous cycle The examined parameters of the estrous cycle were not adversely affected in any group (control, 100, 250 and 350 mg/kg bw/day). Delivery data of dams There were no significant or dose related differences between the control and test item treated female animals in the examined parameters of the delivery (100, 250 and 350 mg/kg bw/day).

A test item influence on the examined parameters of reproductive performance was not found at any dose level. Serum thyroid hormones The FT4 and TSH levels were not adversely affected in the parental male animals or in PN22 offspring at any dose levels.

Necropsy examinations did not reveal specific macroscopic alterations related to the effect of the test item in male or female animals at 100, 250 or 350 mg/kg bw/day.

The weights of examined organs (absolute, relative to body and brain weights) were not affected by the test item in male animals at 100, 250 or 350 mg/kg bw/day.

There were no toxicologically relevant differences in the mean number of primordial, primary, secondary, tertiary follicles, atresia or corpora lutea at 350 mg/kg bw/day at the quantitative examination of ovaries.

The offspring’s development was not adversely influenced at any dose level. No adverse effects on mortality, clinical signs, body weight development, anogenital distance (male and female) or nipple retention (male) were detected. There were no clinical signs, changes in body weight or mean daily food consumption or necropsy findings in F1 generation (male and female) after the 14 days administration of 100, 250 or 350 mg/kg bw/day.

Based on these observations the NOAELs were determined as follows:

NOAEL for systemic toxicity of male rats: 250 mg/kg bw/day

NOAEL for systemic toxicity of female rats: 350 mg/kg bw/day

Supporting study 14-day-DRF for OECD 422

In this study, TBPPI caused alterations following a consecutive 14 day oral administration at 750 mg/kg bw/day to male and female Hsd.Brl.Han: Wistar rats: clinical signs, reduced body weight development (male and female) and food consumption (male), changes in clinical chemistry parameters and changes in organ pathology. At 250 mg/kg bw/day, salivation was observed in male and female animals. At 50 mg/kg bw/day, no test item related changes were found.

Based on these observations the doses for a Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test according to OECD TG 422 were determined as follows: 50, 150 and 310 mg/kg bw/day.

Inhalation route

One supporting literature study with limited documentation is available. Rats exposed to a test item concentration of 50 ppm (0.36 mg/L) for 5 days a week for 28 days showed no mortality and no clinical signs or adverse effects on gross pathology and histopathology. This study is considered not assignable for risk assessment and therefore not used for DNEL derivation.

Dermal route

In accordance with column 2 of REACH Annex IX, the test repeated dose toxicity after dermal application (required in section 8.6) does not need to be conducted as repeated dose toxicity studies for oral application are available or will be proposed. Thus, no test on repeated dose dermal toxicity has to be conducted and risk assessment is based on the oral studies.

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008
The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Based on available data on subchronic repeated dose toxicity the test item is not classified according to Regulation (EC) No 1272/2008 (CLP), as amended for the eighteenth time in Regulation (EU) 2022/692.