6,6'-di-tert-butyl-4,4'-thiodi-m-cresol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The evaluation of the study is hampered by lacking information concerning the Guidelines for testing and the purity of the tested substance; further the study is well documented and performed.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

screening test
In Phase I and II the LD10 is determined. In Phase III pregnant female mice were administered the test substance during gestation for 10 days (gestation day 6-15). Effects on litter and parental animals were recorded.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

- Analytical purity: "the purest grade commercially available".

Test animals

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

sex: female

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc.
- Age at study initiation: 6-8 wks
- Housing: individually polycarbonate shoe box
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 -24
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Extracted by acetonitrile and analyzed by HPLC. Recovery in phase I: 80 - 105%; in phase II: 93 - 106%; in phase III: 76-96%.

Duration of treatment / exposure:

Phase I: 5 days
Phase II: 12 days
Phase III: gestation day 6-15

Frequency of treatment:

Phase I: once daily for 5 days
Phase II and III: once daily for 10 days

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
10, 100, 1000 mg/kg bw/day
Basis:
actual ingested
Phase I

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 100, 310, 400, 500, and 630 mg/kg bw/day.
Basis:
actual ingested
Phase II repeated

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 485 mg/kg bw/day
Basis:
actual ingested
Phase III

No. of animals per sex per dose:

Phase I: three mice
Phase II: four mice
Phase III: 50 mice

Control animals:

yes, concurrent vehicle

Details on study design:

Other:
Phase I: range-finding study in non-pregnant mice dosing 5 days.
Phase II: because of the high mortality rate, a repeated Phase II was conducted with 100, 310, 400, 500, and 630 mg/kg bw/day, using pregnant mice dosing 10 days . Based on the mortality data, the predicted LD10 for 4,4'-thiobis(6-t-butyl-m-cresol) was 485 mg/kg bw/ day.
Phase III: 485 mg/kg bw/ day during 10 days.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: maternal moratlity and toxicity, twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: maternal body weights on days 6 - 15, 17 of gestation, and on day 0, 3 postpartum

Ovaries and uterine content:

no data

Fetal examinations:

PARAMETERS EXAMINED
The following parameters were examined in [F1] offspring: number of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight when delivery was complete and on day 3.

Statistics:

An overall test for homogeneity of variance (Bartlett's test and F-test) was performed on the weight data of each group following randomization. Average body weight per group and average body weight change per group were calculated for treatment and control groups. Pro bit analysis of mortality and morbidity data generated in Phase II of the range finding study was used to determine the predicted LD10 for the Phase III.
Phase III maternal data:
- Random weights: ANOVA (2-tail) (all groups, pregnant dams) (all groups, viable litters only)
- Survival: Fisher's Exact Test (one-tail) (each group vs control, all dams) (each group vs control, pregnant only)
- Weight gains: Mann-Whitney U-Test (2-tail) (each animal, day 6 to day 0 postnatal) (each group vs control; viable litters only)
- Proportion of viable litters Fisher's Exact Test (one-tail) (each group vs control, pregnant only)
- Survival of pups Chi-Square Test (one-tail) (each group vs control)

The Mann-Whitney U-test (2-tail) was used to compare each group to the concurrent control.
- Number live pups/litter (day 0, day 3)
- Length of gestation
- Average pup weight (day 0, day 3)
- Average wt. gain/litter (day 3 - day 0)

The p-value listed is not corrected for multiple comparisons.
14

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: increased mortality

Details on maternal toxic effects:
4,4'-Thiobis (6-t-butyl-m-cresol) caused an increased maternal mortality.

Effect levels (maternal animals)

Key result

Dose descriptor:

other: LD10

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: decreased survival

Details on embryotoxic / teratogenic effects:
4,4'-Thiobis (6-t-butyl-m-cresol) caused a decreased percent survival of the pups while having no effect on the number of viable litters, the litter size, birth weight of the pups and weight gain of the pups.

Effect levels (fetuses)

Key result

Dose descriptor:

other: LD10

Effect level:

485 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: maternal toxicity

Remarks on result:

other: 485 mg/kg bw/ day of 4,4'-thiobis (6-t-butyl-m-cresol) caused increases in rnaternal mortality and a decreased percent of pup survival while not affecting the number of viable litters, the litter size, birth weight or weight gain of the pups.

Fetal abnormalities

Key result

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Phase I:

4,4 1 -Thiobis (6-t-butyl-m-cresol) did not produce chemical related ·mortality when administered at

dose levels of 10, 100, and 1000 mg/kg/day. Therefore, the dose levels for the Phase II selected

were 600, 1200, 2400, 4800, and 9600 mg/kg/day.

Phase II: Because of the high mortality rate, a repeated Phase II was conducted with 100, 310,

400, 500, and 630 mg/kg bw/day. Based on the mortality data, the predicted LD10 for 4,4'-thiobis

(6-t-butyl-m-cresol) was 485 mg/kg bw/ day.

Applicant's summary and conclusion

Conclusions:

In a screening study with female pregnant CD1 mice, the predicted median lethal dose for 4,4' -thiobis(6-t-butyl-m-cresol) was 485mg/kg/day. In addition, 485 mg/kg bw/ day of 4,4'-thiobis (6-t-butyl-m-cresol) caused increases in rnaternal mortality and a decreased percent of pup survival while not affecting the number of viable litters, the litter size, birth weight or weight gain of the pups.