2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

In accordance with Annex IX, 8.7.3 of the REACH legislation, this study at the 100-1000 tpa level is only required if the 28- or 90-day study indicate adverse effects on reproductive organs or tissues. No such effects on reproductive organs were observed in two subchronic studies (see Chapter 7.5).

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

Developmental and teratogenic effects were not detected in the rat and at doses that were not significantly toxic to the parent animals. NOAEL (parental) = 3000 mg/kg bw/day and NOAEL (developmental) = 3000 mg/kg bw

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

(limited documentation of: males and mating procedure; treatment not through the entire period of gestation, but on days 6-15)

GLP compliance:

yes

Species:

rat

Strain:

other: (CrL: COBS CD (SD) BR strain) SPF

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Limited, Manston Road, Margate, Kent
- Age at study initiation: 8-9 weeks
- Weight at study initiation: 170-204 g
- Housing: groups of five in suspended, galvanised metal cages (Bowman R) equipped with solid sides and back, wire mesh front, floor and top
- Diet (ad libitum): Spratt's Laboratory Diet No. 1 (LAD 1)
- Tap water (ad libitum)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 4
- Humidity (%): 59 +/- 7
- Air changes (per hr): 13
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: 1% aqueous methylcellulose

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
During preparation of suspensions on the first day of dosing, a check of the specific gravity of the highest, intended concentration (30% w/v) indicated that an excessive amount of air was being trapped in the mixture. This problem had not been encountered in the feasibility study where a smaller volume was prepared. Attempts to disperse the air ultrasonically were unsatisfactory and absence of stability data precluded overnight preparation. Therefore, in order to ensure greater accuracy of formulation, the concentration was halved and the dosage volume doubled for each group, thereby maintaining the same dosage levels.
Each concentration was prepared separately by suspending a weighed amount of the test material in an appropriate amount of 1% aqueous methylcellulose.
The test suspensions were formulated each day, and to ensure homogeneity, suspensions were stirred with a magnetic stirrer during the dosing procedure.
Dosage volumes were calculated for individual animals on Day 6 of pregnancy and adjusted according to bodyweight on Days 10 and 14.

VEHICLE
- Justification for use and choice of vehicle (if other than water): no data
- Concentration in vehicle: 1.5, 5 and 15 % w/v at 300, 1000 and 3000 mg/kg bw
- Amount of vehicle (if gavage): 2 ml/ 100 g bw

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- Proof of pregnancy: The day of mating, as judged by the appearance of sperm in the vaginal smear or by the presence of a vaginal plug was considered as Day 0 of pregnancy.
No further details on mating procedure were given.

Duration of treatment / exposure:

Treatment commenced on Day 6 of pregnancy and continued daily up to and including Day 15 of pregnancy.

Frequency of treatment:

daily

Duration of test:

Animals were killed on day 20 of gestation.

Dose / conc.:

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

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Dose / conc.:

3 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Prior to the main study, the feasibility of administering 3000 mg/kg/day - the highest intended dosage - was investigated in non-pregnant females which were treated for ten consecutive days. No clinical signs of reaction to treatment were observed in this feasibility study and there were no deaths; other parameters, such as overall food intake and mean bodyweight gain, also appeared to be unaffected and no macroscopic changes attributable to treatment were recorded at terminal autopsy.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: All rats were weighed initially (=Day 1 of gestation) and on Days 3, 6, 10, 14, 17 and 20.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day: 20
- Organs examined: On Day 20 of pregnancy the animals were killed by CO2 asphyxiation, dissected and examined for congenital abnormalities and macroscopic pathological changes in maternal organs.

OTHER: All animals that died were weighed and subjected to post mortem examination.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: [half per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: No data

Statistics:

Statistical analyses were performed routinely on litter data, using the litter as the basic sample unit; non-parametric tests (Jonckheere and Kruskal-Wallisl) were employed for mean values of litter size, pre- and post implantation loss, litter weight, mean pup weight and the incidence of anomalous offspring as these values rarely follow a 'normal' distribution.

Historical control data:

No data.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Pale coloured faeces were observed amongst rats treated at 3000 mg/kg bw/d, the incidence - occurring between Days 8 and 16 of gestation - basically coinciding with the dosing period. No signs of reaction were recorded at either 300 or 1000 mg/kg bw/d.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Two deaths occurred, one at 1000 mg/kg bw/d and another at 3000 mg/kg bw/d, but both were consistent with intubation error.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

At 3000 mg/kg bw/d, a gradual retardation of mean bodyweight gain was apparent during the dosing period. No further retardation occurred after cessation of dosing, but parity with the controls had not been regained by termination. Mean weight gains at 300 and 1000 mg/kg bw/d were comparable to that of the control group throughout the study.

Food consumption and compound intake (if feeding study):

not examined

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

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Description (incidence and severity):

When surviving animals were killed on Day 20 of gestation, autopsy findings did not reveal any macroscopic changes considered to be attributable to treatment with the test substance.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

Pregnancy rate, as assessed by the number of pregnant animals, was essentially comparable for all groups. Slight differences between test groups and the control, in respect of mean values for corpora lutea count and preimplantation loss, were neither statistically significant (P>0.05) nor adversely dosage-related. Mean post implantation loss of all treated groups was lower than that of the control group.

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

not examined

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined

Changes in number of pregnant:

not examined

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
CLINICAL SIGNS and MORTALITY
Pale coloured faeces were observed amongst rats treated at 3000 mg/kg bw/d, the incidence - occurring between Days 8 and 16 of gestation - basically coinciding with the dosing period. No signs of reaction were recorded at either 300 or 1000 mg/kg bw/d. Two deaths occurred, one at 1000 mg/kg bw/d and another at 3000 mg/kg bw/d, but both were consistent with intubation error.

BODY WEIGHT
At 3000 mg/kg bw/d, a gradual retardation of mean bodyweight gain was apparent during the dosing period. No further retardation occurred after cessation of dosing, but parity with the controls had not been regained by termination. Mean weight gains at 300 and 1000 mg/kg bw/d were comparable to that of the control group throughout the study.

PREGNANCY RATE AND PRE-IMPLANTIATION LOSS
Pregnancy rate, as assessed by the number of pregnant animals, was essentially comparable for all groups. Slight differences between test groups and the control, in respect of mean values for corpora lutea count and preimplantation loss, were neither statistically significant (P>0.05) nor adversely dosage-related.

GROSS PATHOLOGY
When surviving animals were killed on Day 20 of gestation, autopsy findings did not reveal any macroscopic changes considered to be attributable to treatment with the test substance.

Dose descriptor:

NOAEL

Effect level:

3 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

Fetal body weight changes:

no effects observed

Description (incidence and severity):

Mean foetal weight of all test groups was similar or superior to the control mean. Intergroup variation in mean values for litter weight reflected differences in mean litter size; there was no indication of any adverse effect of treatment.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

There was no appreciable intergroup difference in mean sex ratio.

Changes in litter size and weights:

effects observed, non-treatment-related

Description (incidence and severity):

The slightly lower mean values recorded for litter size in all test groups were not significantly different from the control value (P> 0.05) and appeared to be largely a perpetuation of differences in ovulation rate which would have pre-dated commencement of treatment.

External malformations:

no effects observed

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Of the nine foetuses which were recorded as showing malformations, none occurred at 3000 mg/kg bw/d: three were recorded in the control group, five at 300 mg/kg bw/d and one at 1000 mg/kg bw/d. Neither the types of defect seen nor their distribution indicated any association with treatment. The overall incidence of visceral and skeletal anomalies did not indicate any adverse treatment-related pattern. There were no foetuses with extra (14) ribs amongst treated groups and mean values for variant sternebrae did not indicate any adverse treatment-related effects.

Visceral malformations:

effects observed, non-treatment-related

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no instances of total litter loss (total resorption) in any group.

LITTER SIZE AND POST-IMPLANTATION LOSS
Mean post implantation loss of all treated groups was lower than that of the control group. The slightly lower mean values recorded for litter size in all test groups were not significantly different from the control value (P> 0.05) and appeared to be largely a perpetuation of differences in ovulation rate which would have pre-dated commencement of treatment. There was no appreciable intergroup difference in mean sex ratio.

LITTER AND MEAN FOETAL WEIGHT
Mean foetal weight of all test groups was similar or superior to the control mean. Intergroup variation in mean values for litter weight reflected differences in mean litter size; there was no indication of any adverse effect of treatment.

MALFORMATIONS AND ANOMALIES
Of the nine foetuses which were recorded as showing malformations, none occurred at 3000 mg/kg bw/d: three were recorded in the control group, five at 300 mg/kg bw/d and one at 1000 mg/kg bw/d. Neither the types of defect seen nor their distribution indicated any association with treatment. The overall incidence of visceral and skeletal anomalies did not indicate any adverse treatment-related pattern.

SKELETAL VARIANTS
There were no foetuses with extra (14) ribs amongst treated groups and mean values for variant sternebrae did not indicate any adverse treatment-related effects.

Dose descriptor:

NOAEL

Effect level:

3 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Embryonic and foetal development did not appear to have been adversely affected by treatment of the dam at any of the dosages used in this study.

Abnormalities:

not specified

Developmental effects observed:

not specified

Executive summary:

The test article was administered at dosages of 0 (Control), 300, 1000 and 3000 mg/kg/day by intra gastric intubation during Days 6 to 15 inclusive of gestation. The animals were killed on Day 20 of gestation, litter values determined and the foetuses examined for

structural malformations and anomalies. Prior to the main study, the feasibility of administering 3000 mg/kg/day - the highest intended dosage - was investigated in non-pregnant females which were treated for ten consecutive days. No clinical signs of reaction to treatment were observed in the feasibility study and there were no deaths; other parameters, such as overall food intake and mean bodyweight gain, also appeared to be unaffected and no macroscopic changes attributable to treatment were recorded at terminal autopsy. In the main study, pale coloured faeces were observed amongst rats treated at 3000 mg/kg/day, the incidence - occurring between Days 8 and 16 of gestation - basically coinciding with the dosing period. No signs of reaction were recorded at either 300 or

1000 mg/kg/day. Two deaths occurred, one at 1000 mg/kg/day and another at 3000 mg/kg/day, but both were consistent with intubation error. Mean bodyweight gain of dams treated at 3000 mg/kg/day was slightly retarded during the dosing period and parity with that of the control group had not been regained by Day 20. Mean weight gain at 300 and 1000 mg/kg/day remained essentially similar to that of the control group throughout. No macroscopic changes were observed at terminal autopsy of treated animals which were considered to be attributable to the test article. There were no instances of total litter loss (total resorption) at any dosage, nor any significant effects on litter parameters, as assessed by mean values for pre- and post implantation loss, litter size, sex ratio, litter weight and foetal weight. Embryonic and foetal development, as assessed by the overall incidence of malformations, anomalies and skeletal variants did not appear to have been adversely affected by treatment of the dam at any of the dosages used in this study. It was concluded that under the conditions of this study, the test item showed no evidence of teratogenicity or of significant effects on embryo-foetal development.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

3 000 mg/kg bw/day

Species:

rat

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

In a developmental toxicity study the test substance (purity of > 99%) was administered to 25 pregnant rats ((CrL: COBS CD (SD) BR strain) SPF) per dose by gavage at dose levels of 300, 1000, 3000 mg/kg bw/day in aqueous methylcellulose (1%). Treatment was performed once daily from days 6 through 15 of gestation. Control animals were treated with the vehicle only. Animals were sacrificed on day 20 of gestation. Two deaths occurred, one at 1000 mg/kg day and another at 3000 mg/kg bw/day, but both were consistent with intubation error. Pale coloured faeces were observed amongst rats treated at 3000 mg/kg bw/day, the incidence - occurring between Days 8 and 16 of gestation - basically coinciding with the dosing period. No signs of reaction were recorded at either 300 or 1000 mg/kg bw/day. No other effects in the dams were observed. The maternal NOAEL is 3000 mg/kg bw/day. There were no instances of total litter loss (total resorption) in any group. Mean post implantation loss of all treated groups was lower than that of the control group. Slightly lower mean values recorded for litter size in all test groups were not significantly different from the control value (P > 0.05) and appeared to be largely a perpetuation of differences in ovulation rate which would have pre-dated commencement of treatment. There was no appreciable intergroup difference in mean sex ratio. Mean foetal weight of all test groups was similar, or superior, to the control mean. Intergroup variation in mean values for litter weight reflected differences in mean litter size; there was no indication of any adverse effect of treatment. Of the nine foetuses which were recorded as showing malformations, none occurred at 3000 mg/kg bw/day: three were recorded in the control group, five at 300 mg/kg bw/day and one at 1000 mg/kg bw/day. Neither the types of defect seen nor their distribution indicated any association with treatment. The overall incidence of visceral and skeletal anomalies did not indicate any adverse treatment-related pattern. There were no foetuses with extra (14) ribs amongst treated groups and mean values for variant sternebrae did not indicate any adverse treatment-related effects. Based on these findings, no substance-related effect on embryonic or foetal development is assumed. The NOAEL for developmental toxicity is 3000 mg/kg bw/day (Ciba Geigy, 1983).

The developmental toxicity study in the rat is classified acceptable for assessment purposes of developmental toxicity as it satisfies the guideline requirement for a developmental toxicity study (OECD 414) in rodents in all but one aspect: treatment of dams was limited to gestation periods Day 6-15 of gestation as opposed to treatment up to a day before scheduled kill.

The findings of the above described study are supported by the findings observed in a combined 2 -Generation toxicity/Carcinogenicity study, performed by Mosinger (1976), where Wistar rats were treated with 200 mg/kg bw /day (nominal concentration) of the unchanged substance in diet for 2 years. The animals were treated as follows: 3 months treatment before mating for the P1 generation, 6 months treatment before mating for the F1 generation and 8 months treatment for the F2 generation. The first treatment was conducted on January 20, 1974 and the last one on January 20, 1976. Each 1 male and 5 females of the P1 and F1 generations were mated, each 5 animals per sex of the F1 generation were further treated until mating. Each 5 animals per sex of the F2 generation were further treated until the end of the study (growth). The following parameters were examined in F1 / F2 offspring: number and sex of pups, live births, postnatal mortality, presence of gross anomalies, weight gain. The pups were examined for external and internal abnormalities, including the cervical, thoracic, and abdominal viscera (not further specified). Liver, kidneys and lungs were prepared for microscopic examination in 2 animals. In the dams, no toxic effects were observed. In the F1 and F2 generations, no congenital malfomations, teratogenic effects or growth retardations were observed at this unique dose level. Therefore, a NOAEL was set at 200 mg/kg bw/day for maternal toxicity as well as for developmental toxicity.

Justification for classification or non-classification

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

The available experimental test data is reliable and suitable for the purpose of classification under Regulation (EC) No.1272/2008. Based on the data, classification for toxicity to reproduction is not warranted under Regulation (EC) No.1272/2008.