4-tert-butylpyrocatechol

Toxicity to reproduction

Administrative data

Endpoint:

reproductive toxicity, other

Remarks:

Repeated toxicity study including reproductive data

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Reproductive toxicity evaluations included in a study that was GLP-compliant and comparable to an OECD-guideline study.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Materials and methods

Principles of method if other than guideline:

Screening on sperm motility and vaginal cytology from animals dosed for 14 weeks in the diet

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-tert-butylpyrocatechol

EC Number:

202-653-9

EC Name:

4-tert-butylpyrocatechol

Cas Number:

98-29-3

Molecular formula:

C10H14O2

IUPAC Name:

4-tert-butylbenzene-1,2-diol

Details on test material:

p-tert-butylcatechol (TBC) from Aldrich Chemical Company (Lot No. 19115EN).
The purity was determined to be greater than 99% by HPLC.
Two impurities were detected, at approximately 0.26 and 0.20% concentration (no data about their nature).

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Laboratory Animals and Services (Germantown, NY)
- Age at study initiation: 6 weeks old
- Weight at study initiation: 78 g (males) and 75 g (females)
- Fasting period before study: no
- Housing: 5 animals per cage (polycarbonate, changed twice per week)
- Diet: NTP-2000 mash feed, available ad libidum
- Water: tap water via automatic watering system, available ad libidum
- Acclimation period: 11 (males) or 12 (females) days

ENVIRONMENTAL CONDITIONS
- Temperature: ca. 22°C
- Humidity: 50% +/- 15%
- Air changes: 10/hour
- Photoperiod: 12 hours light/day

IN LIFE DATES:
26 (males) or 27 (females) August 1996 to 25 (males) or 26 (females) November 1996.

Administration / exposure

Route of administration:

oral: feed

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet: every 4 weeks
- Type of food: irradiated feed
- Storage of food : in plastic bags inside buckets at 5°C for up to 42 days

Details on mating procedure:

No mating performed

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- Analytical verification of homogeneity of doses/concentrations: Yes (performed in the 781 and 12500 ppm dose formulations)
- Analytical verification of stability of doses/concentrations: Yes (stability of the 781 ppm dose formulation was confirmed for 42 days for samples stored in plastic bags at temperatures up to 5°C. Samples subjected to animal room conditions showed declines of up to 37% in TBC concentrations with time.)
- Dose formulations were analyzed at the beginning, midpoint, and end of the study; all dose formulations analyzed were within 10% of the target concentrations. Animal room samples of these dose formulations were also analyzed; the concentrations of 9 of 15 animal room samples were less than 90% of the target concentrations (these low concentrations are attributed to chemical degradation, oxidation, evaporation or binding with feed)

Duration of treatment / exposure:

14 weeks

Frequency of treatment:

7 days per week

Details on study schedule:

No mating performed

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 3125, 6250 and 12500 ppm
Basis:
nominal in diet
(groups for reproductive assessment)

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 270, 525 and 1030 mg/kg bw
Basis:
other: males (groups for reproductive assessment)

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 265, 555 and 1010 mg/kg bw
Basis:
other: females (groups for reproductive assessment)

No. of animals per sex per dose:

10

Control animals:

yes, plain diet

Details on study design:

Dose selection rationale: based on the results in the 15-day study in rats: based on the body weight effects in the 25000 ppm groups and mortality in the 50000 ppm groups, the highest exposure concentration selected for the 14-week study was 12500 ppm.

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule: initially, weekly and at the end of the study

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE: No

Oestrous cyclicity (parental animals):

Parameters assessed on vaginal samples collected for 12 consecutive days prior to sacrifice:
- Number of cycling females
- Number of females with regular cycles
- Number of cycles
- Estrous cycle length
- Percentage of time spent in the various estrous cycle stages

Sperm parameters (parental animals):

- Epididymal sperm motility
- Spermatid heads per testis
- Spermatid heads per gram testis
- Spermatid heads per cauda epididymis
- Spermatid heads per gram cauda epididymis

Litter observations:

Not appropriate

Postmortem examinations (parental animals):

Organ weights in males:
- Left cauda epididymis
- Left epididymis
- Left and right testes

Microscopic examination (0 and 12500 ppm groups):
- Clitoral gland
- Mammary gland
- Ovary
- Uterus
- Preputial gland
- Prostate
- Testis with epididymis and seminal vesicle

Postmortem examinations (offspring):

Not appropriate

Statistics:

Not included

Reproductive indices:

Not included

Offspring viability indices:

Not appropriate

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

not examined

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

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:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

effects observed, treatment-related

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

not examined

Details on results (P0)

BODY WEIGHT AND WEIGHT GAIN
Final mean body weights and body weight gains of animals exposed to 3125 ppm or greater were significantly lower than those of the controls (-7%, -12% and -23% for males and -4.5%, -8.5% and -9% for females, respectively).

FOOD CONSUMPTION AND COMPOUND INTAKE
Feed consumption by males and females in the 6250 and 12500 ppm groups at week 1 and the 12500 ppm groups at week 14 was lower than that by the respective controls.

REPRODUCTIVE ORGAN WEIGHTS
In male rats given 12500 ppm, the absolute left cauda epididymis, epididymis, and testis weights were decreased by 15%, 10%, and 9%, respectively, compared to controls.

SPERM MEASURES
The number of spermatid heads per testis and epididymal sperm motility of male rats given 12500 ppm were signicantly lower than those of the controls (by 17% and 7%, respectively).

ESTROUS CYCLE
In females dosed at 6250 and 12500 ppm, the numbers of cycling animals and those with regular estrous cycles were lower than in controls. Females exposed at 3125, 6250 and 12500 ppm had significantly fewer estrous cycles than controls (-28%, 44% and 44% vs. controls, respectively). Estrous cycle length increased with exposure concentration. Females at 6250 and 12500 ppm showed significantly longer cycles (+31% and +47%, respectively) and spent more time in diestrus and less time in proestrus, estrus, and metestrus compared to controls.

Effect levels (P0)

1

Key result

Dose descriptor:

NOAEL

Remarks:

(reproductive parameters)

Effect level:

6 250 ppm (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Lower reproduction organ weights and lower number of spermatid

2

Key result

Dose descriptor:

NOAEL

Remarks:

(reproductive parameters)

Effect level:

< 3 125 ppm (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: estrous cycle number

Target system / organ toxicity (P0)

Critical effects observed:

yes

Lowest effective dose / conc.:

3 125 ppm

System:

other: Estrous cycle

Organ:

other: Estrous cycle

Results: F1 generation

Effect levels (F1)

Remarks on result:

not measured/tested

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

Summary of reproductive tissue evaluations for males:

	0 ppm	3125 ppm	6250 ppm	12500ppm
n	10	10	10	10
Weights(g)
Necropsy body weight	320	296**	279**	247**
Absolute L. Cauda epididymis	0.1611	0.1593	0.1613	0.1364**
Absolute L. Epididymis	0.4706	0.4713	0.4634	0.4221**
Absolute L. Testis	1.5258	1.5280	1.5006	1.3843*
Spermatid and sperm measurements
Spermatid heads (10^7/testis)	181.88	157.13	168.69	150.31**
Epididymal sperm motility(%)	72.15	70.87	70.76	67.08**

*Significantly different (P ≤ 0.05) from the control group  ** P ≤0.01

Estrous cycle characterisation for females:

	0 ppm	3125 ppm	6250 ppm	12500ppm
n	10	10	10	10
Necropsy body weight	184	175*	170**	162**
Number of cycling females^a	10	10	5*	4*
Nb of females with regular estrous cycles	10	8	2*	2*
Number of estrous cycles	1.8	1.3*	1.0*	1.0*
Estrous cycle length (days)	4.75	5.50	6.20*	7.00**
Estrous stages (% of cycle)
Diestrus	47.1	57.5	78.3	77.1
Proestrus	15.1	14.2	4.2	5.9
Estrus	23.5	17.5	11.7	10.2
Metestrus	14.3	10.8	5.8	6.8

*Significantly different (P ≤ 0.05) from the control group  ** P ≤0.01

^adoes not include animals with estrous cycles that were longer than 12 days or unclear

Applicant's summary and conclusion

Conclusions:

Following 14 weeks of dietary administation to rats, effects on reproductive organ weights, sperm count and motility in males and effects on estrous cycle number and duration in females were observed.

Executive summary:

In a 14 week dietary toxicity study (NTP study, 2002), 4 -tert-butylpyrocatechol was administered to 6 -week male and female Fischer 344 rats, 10/dose, in diet, at the dose levels of 0, 781, 1562, 3125, 6250 and 12500 ppm, resulting in doses of 0, 70, 135, 270, 525 and 1030 mg/kg bw to males and 0, 70, 145, 265, 555 and 1010 mg/kg bw to females. In the 0, 3125, 6250 and 12500 ppm groups, reproductive evaluations were included at the end of the dosing period. These evaluations consisted of cauda epididymis, epididymis, and testis weights, spermatid and sperm measurements at necropsy for males, and estrous cycle determinations for 12 consecutive days prior to necropsy for females.

There were no clinical findings of toxicity and no mortality. Mean body weights of rats exposed to 3125 ppm or greater were significantly lower than those of the controls (from -4.5% to -23%). Feed consumption by males and females in the 6250 ppm (week 1) and 12500 ppm (weeks 1 and 14) was less than that by the controls.

The absolute left cauda epididymis, epididymis and testis weights, number of spermatid heads per testis, and epididymal sperm motility of males in the 12500 group were significantly less than those of the controls. The number of cycling females and females with regular estrous cycles were decreased in the 6250 and 12500 ppm groups. Exposed groups of females had significantly fewer estrous cycles than did the controls. Estrous cycle length increased with increasing exposure concentration; females in the 6250 and 12500 ppm group had significantly longer cycles and spent more time in diestrus and less time in proestrus, estrous and metestrus than did the controls.

The NOEL for reproductive parameters was 6250 ppm (equivalent to 525 mg/kg bw/day) for males, based on decreased organ weights, and < 3125 ppm (equivalent to 265 mg/kg bw/day) for females, based on decreased estrous cycle number.