p-(1,1-dimethylpropyl)phenol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

90-2-23 to 91-4-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study with no significant deviations from protocol

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 83-3 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

p-(1,1-dimethylpropyl)phenol

EC Number:

201-280-9

EC Name:

p-(1,1-dimethylpropyl)phenol

Cas Number:

80-46-6

Molecular formula:

C11H16O

IUPAC Name:

4-(2-methylbutan-2-yl)phenol

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): phenol, 4-(1,1-dimethylpropyl)-
- Lot/batch No.: 20409018

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

Animals were housed throughout the study in an environment controlled room with a 12-hour light/12-hour dark cycle. The controls were
set to maintain a room temperature of 64-79.F and a relative humidity of 40-70%. Room temperature and relative humidity were determined and
recorded daily.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

Dosing solutions were prepared: 10, 40 and 100 mg/mL. Animals were dosed with 5 ml/kg.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical analyses indicated that Nipacide PTAP was homogeneous and stable in aqueous solution when stored for up to eight days at room
temperature. Analysis of dosing solutions resulted in,average test article recoveries ranging from 101.6 to 108.7% indicating that the solutions
were accurately prepared.
Concentration Verification Analysis Data on Week 1 for Nipacide PTAP in Corn Oil
Nominal Actual Average (mg/mL) n=2
10.73, 11.00
41.76, 40.80
107.10, 105.03

Concentration Verification Analysis Data on Week 2 for Nipacide PTAP in Corn O i l
10.55, 10.64
41.55, 41.57
102.47, 100.57

Details on mating procedure:

Animals were acclimated to the laboratory conditions for a period of 12 days prior to mating. At the conclusion of acclimation, the animals were
weighed and examined. Females determined to be suitable test subjects based on age, healthy appearance, and body weight, were cohabitated
with proven resident Sprague-Dawley Crl:CDaBR VAF/Plusa male rats. At the initiation of breeding, all females were approximately 90 days of age with body weights ranging from 220 to 266 g. Evidence of mating was determined by the presence of a copulatory plug in the vagina or a sperm positive vaginal smear. The day evidence of copulation was confirmed was designated as day 0 of gestation. At that time, the female rats were assigned
consecutively, in a block design, to study groups. Gestation day 0 body weights ranged from 215-266 g.

Duration of treatment / exposure:

The dosage preparations were administered orally by gavage as a single dose daily, from gestation day 6 through gestation day 15.

Frequency of treatment:

Once daily. The animals were dosed at approximately the same time each day.

Duration of test:

Gestation day 0 to scheduled caesarian section which took place at gestation day 20.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 50, 200, 500 mg/kg bw/day
Basis:
nominal conc.

No. of animals per sex per dose:

25 females per dose group

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

During the experimental period, all animals were observed daily for clinical signs of toxicity including physical or behavioral abnormalities.
Mortality checks were performed twice daily, in the morning and afternoon. In addition, during the treatment period, the rats were observed
between one-half and two hours following dosing for detection of overt signs of toxicity.

Individual body weights were measured on gestation days 0, 6, 9 , 12, 16 and 20. Body weight changes were calculated for the following gestation
intervals: 0-6, 6-9, 9-12, 12-16, 16-20, 6-16 and 0-20. Individual food consumption was measured for gestation days 0-6, 6-9, 9-12, 12-16, 16-20, 6-16 and0-20. Food consumptionwas calculated and reported as grams/animal/day.

All females were sacrificed on gestation day 20 by carbon dioxide, asphyxiation and subjected to a gross necropsy examination. The thoracic,
abdominal and pelvic cavities were opened and the viscera examined. Abnomalities were recorded.

Ovaries and uterine content:

The uterus was removed from the body, examined externally, weighed and then opened for internal examination. The number
of viable fetuses and the presence of any nonviable fetuses and early and late resorptions were then recorded beginning with the left distal uterine
horn, noting the position of the cervix, and continuing up the right uterine horn. Corpora lutea were counted and recorded for each ovary.

Fetal examinations:

Fetuses were examined for external, visceral, and skeletal anomalies. Malformations and variations were classified based upon the severity of the
anatomical change(s) and their potential for interference with organ and/or body functions. The sex of each fetus was determined.
The fetuses were weighed and tagged individually.

Approximately one-half of the fetuses were fixed in Bouin' s solution for subsequent visceral examination by the method of Wilson 1965 [in
Teratology Principles and Techniques, eds. J. G. Wilson and J. Workany, pp. 262-277.] The examination was performed under a low power dissection scope.

Approximately one-half ofthe fetuses were eviscerated and fixed in 95% isopropyl alcohol. Following fixation, the fetuses were macerated
in 1.5% aqueous potassium hydroxide solution, stained with Alizarin Red S, and cleared in 25% aqueous glycerin solution. The examination was
performed under low power magnification.

Statistics:

Statistical analyses were performed by a Digital Vax 11/730 computer. All analyses were two-tailed with a minimum significance level of 5%. One
way analysis of variance followed by Dunnett's test was used to analyze maternal and fetal data including body weights, food consumption, number of
viable fetuses, implantation sites, and corpora lutea. Mann-Whitney U test was used to compare post-implantation loss, dead fetuses, and
resorptions. Fetal sex ratios were analyzed using the Chi-Square test. Fisher's Exact test was used to analyze the incidence and number of fetal
malformations and variations.

Historical control data:

Relevant historical control data for bent ribs observations = 0-3.6%.
All data provided in Appendix N of the study report.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
All females survived to scheduled caesarean section on gestation day 20.
Treatment-related clinical signs were observed at the 200 and 500 mg/kg/day levels. The most notable findings included urine staining, mucoid
or soft stools, rales, hairloss and post-dose salivation. The hairloss was particularly evident in the abdominal and hip regions of these animals. The
overall severity of the effects were greater at the 500 mg/kg/day level.
External findings of hairloss and urine stain were confirmed at necropsy.
Significant body weight losses occurred at the 200 and 500 mg/kg/day levels during the first three days of dosing (gestation days 6-9). Body weight gains and food consumption were significantly reduced at the 200 and 500 mg/kg/day 'level throughout the treatment period.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOEL

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
A slight, but statistically significant decrease in mean fetal body weight was observed at the 500 mg/kg/day level. All other cesarean section
parameters evaluated, including the number of corpora lutea, implantation sites, viable fetuses, early and late resorptions, fetal sex ratios and
gravid uterus weights, were comparable between the control and treatment.

No statistically significant differences were noted in the fetal malformation data. Observed malformations included one control fetus with
multiple craniofacial anomalies, one 200 mg/kg/day fetus with absent tail and anal atresia, and four fetuses in the 500 mg/kg/daygroup with a
single malformation per fetus (hydrocephaly, forked rib, fused ribs or skull anomaly). The low incidence, lack of statistical significance, and
dissimilar nature of the findings indicated that they were not the result of test article treatment groups.

Evaluation of the fetal variations revealed an apparent dose-related increase in the incidence of fetuses and litters with bent ribs. The
percentage of fetuses with bent ribs in the control, 50, 200 and 500 mg/kg/day groups was 0.6, 2.6, 5.8 and 9.6, respectively. The percentage
of fetuses with bent ribs at the 50 mg/kg/day level was well within the SLS historical control range of 0.0-3.6%. while the percentage of fetuses in
the 200 and 500 mg/kg/day groups slightly exceeded the range. The incidence of litters with bent ribs was statistically increased in the 500 mg/kg/day group when compared to control litters. It is noteworthy that the occurrence of bent ribs was outside the historical control range at the 200 and 500 mg/kg/day levels where overt maternal toxicity was evident.

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOEL

Effect level:

200 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: fetotoxicity

2

Key result

Dose descriptor:

NOEL

Effect level:

> 500 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Key result

Abnormalities:

not specified

Overall developmental toxicity

Key result

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, this substance showed now signs of teratogenicity. Some signs of maternal and fetal toxicity were present.
A level of 50 mg/kg/day is considered a no-observed-effect level (NOEL) for maternal toxicity.
A level of 200 mg/kg/day was considered a NOEL for fetal toxicity.
A level of 500 mg/kg/day (top dose tested) was considered a NOEL for teratogenicity.

Executive summary:

In a teratology study, p-tert amylphenol was administered by oral gavage as a suspension in corn oil to Sprague Dawley rats (25 females per dose group) at dose levels of 0, 50, 200 and 500 mg/kg bw/day.

No maternal mortality occurred during the study. Treatment-related clinical signs of toxicity were observed at the 200 and 500 mg/kg/day levels. The most notable findings included urine staining, mucoid or soft stools, rales, hairloss and post-dose salivation. The hairloss was particularly evident in the abdominal and hip regions of these animals. Significant body weight losses occurred at the 200 and 500 mg/kg/day levels during the first three days of dosing (gestation days 6-9). Body weight gains and food consumption were significantly reduced at the 200 and 500 mg/kg/day level throughout the treatment period.

The NOEL for maternal toxicity is 50 mg/kg bw/day in females based on reduced body weight and clinical observations.

The NOEL for fetal toxicity is 200 mg/kg bw/day based upon the presence of bent ribs at the top dose.

The NOEL for teratogenicity is 500 mg/kg bw/day based upon no teratogenic effects seen at the top dose tested.