p-cresol

Toxicity to reproduction

Administrative data

Endpoint:

two-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: TSCA Health Effects Test Guideline for Specific Organ/Tissue Toxicity - Reproduction/Fertility Effects (EPA 1983)

Deviations:

no

Principles of method if other than guideline:

Reproductive toxicity of p-cresol was examined in a two-generation toxicity study for specific organ/tissue toxicity - Reproduction/Fertility effects.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

p-cresol

EC Number:

203-398-6

EC Name:

p-cresol

Cas Number:

106-44-5

Molecular formula:

C7H8O

IUPAC Name:

p-cresol

Details on test material:

Test substance: p-cresol, 98.93% pure

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston NY
- Age at study initiation: 6 weeks (P)
- Weight at study initiation: (P) Males: 189-191 g; Females: 141-142 g;

- Housing:
initially 2 /same sex during acclimatisationperiod; and then singly except for the cohabitation and lactation periods
- Diet ad libitum
- Water ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 68-74
- Humidity (%): 40-60
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing formulations were prepared by weighing the amount of test chemical into a volumetric flask and diluting to volume with certified corn oil. The resulting solutions were mixed by repeated inversions and stored at room temperature.

Details on mating procedure:

- M/F ratio per cage: 1/1
-Length of cohabitation: 21 days
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
- After 7 days of unsuccessful pairing replacement of first male by another male with proven fertility.
- Further matings after two unsuccessful attempts: no
- After successful mating each pregnant female was caged singly
- Any other deviations from standard protocol: no
- M/F ratio per cage:
- Length of cohabitation:
- Proof of pregnancy: [vaginal plug / sperm in vaginal smear] referred to as [day 0 / day 1] of pregnancy
- After ... days of unsuccessful pairing replacement of first male by another male with proven fertility.
- Further matings after two unsuccessful attempts: [no / yes (explain)]
- After successful mating each pregnant female was caged (how):
- Any other deviations from standard protocol:

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A standard stock solution was prepared (1 mg/ml propanol), which was used to prepare standards ranging form 10 to 100 ng/μl. With these solutions standard curve was generated using HPLC. Dosing formulation concentrations were verified by preparing aliquots which were injected on HPLC column. The measured concentration of each dosing solution was then calculated from the equitation for the standard curve developed by linear regression.

Duration of treatment / exposure:

Exposure period: 27 weeks
Premating exposure period (males): 10 weeks
Premating exposure period (females): 10 weeks
Duration of test: 29 weeks

Frequency of treatment:

P- and F1-generation: once per day, 5 days per week
F1 generation producing F2: once per daym 7 days per week

Details on study schedule:

Number of generation studies: 2
At day 28-40 post partum F1 animals were selected to be parents of the F2-generation and were gavaged with their respective formulations for at least 11 weeks on 5 days per week
The F1 animals were approximately 15-17 weeks of age at the initiation of the mating period.
they were dosed from that time point 7 days/week. Mating procedure was performed as done with the P-generation.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 30, 175, 450 mg/kg bw
Basis:

No. of animals per sex per dose:

25 rats/sex/dose

Control animals:

yes, concurrent vehicle

Details on study design:

no further data

Positive control:

no data

Examinations

Parental animals: Observations and examinations:

Mortality:
twice daily
General condition:
daily throughout the course of the study including skin and fur, eyes and mucous membranes, respiratory symptoms, circulatory system, autonomic and central nervous system, somatomotor activity, behavior pattern
Body weight dertermination
male, female: initially and then weekly until mating
female during gestation: day 0, 7, 13, 20 post partum day 0, 4, 7, 14, 21
Food concumption:
measured weekly during pre-breed dosing period for P and F 1 generation;
all other phases of this study determination was made visually

Oestrous cyclicity (parental animals):

vaginal smears were examined to determine pregnancy

Sperm parameters (parental animals):

no data

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- If yes, maximum of .8 pups/litter (4/sex/litter as nearly as possible); excess pups were killed and discarded.


PARAMETERS EXAMINED
The following parameters were examined in [F1 / F2 / F3] offspring:
number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities,

GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities; possible cause of death wwas not determined for pups born or found dead.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals after the completion of the mating period
- Maternal animals: All surviving animals after the F1 and F2 litters have been weanded

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

HISTOPATHOLOGY
Male and female adult rats of the highest doses groups and the controls
The tissues as indicated below were prepared for microscopic examination and weighted, respectively:
Pituitary, vagina, uterus, ovaries, testes, epididmides, seminal vesicles, prostate, and other tissues with gross lesions identified as being potentially treatment-related
A complete histopathological examination was conducted for any parental animal dying on test.

Postmortem examinations (offspring):

All pups dying during lactation are necropsied to investigate the cause of death.
At weaning, postnatal day 21, 1 female and 1 male from each F1 litter is selected on a random basis to become parents of the next generation.
The remaining offspring is examined for gross external abnormalities, euthanized and discarded

Statistics:

Levene's test, ANOVA, t-test corredted by bonferroni method, Kruskal-Wallis test, Mann-Whitney U-test, Fisher's exact test

Reproductive indices:

calculated for p- and F1 animals:
Mating index (%):
---for males: number of males impregnation females divided through the total number of males paired multiplied by 100
---for females: number of females with copulation plugs divided through the number of females cohabited multiplied by 100
Fertility index(%):
---for males: number of males producing pregnant females divided through number of males impregnating females multiplied by 100
---for females: number of females with copulation plugs divided through the number of females
cohabited multiplied by 100
Gestational Index (%):
number of females with live litters divided through number of females pregnant multiplied by 100

Offspring viability indices:

calculated for F1 and F2 animals:
live birth index (%):
number of pups at birth devided through the total number of pups born multiplied by 100
4-day survival index (%):
number of pups surviving 4 days devided through the total number of live pups at birth multiplied by 100
7-day survival index(%):
number of pups surviving 7 days devided through the total number of live pups at birth multiplied by 100
14-day survival index(%):
number of pups surviving 14 days devided through the total number of live pups at birth multiplied by 100
21-day survival index(%):
number of pups surviving 21 days devided through the total number of live pups at birth multiplied by 100

Lactation omdex (%):
number of pups surviving 21 days through total number of live pups at 4 days multiplied by 100

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

not specified

Histopathological findings: non-neoplastic:

not examined

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

no effects observed

Details on results (P0)

see section " Remarks on results"

Effect levels (P0)

1

Dose descriptor:

other: NOAEL (general toxicity)

Effect level:

ca. 30 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: >= 175 mg/kg bw/d: clinical signs of toxicity including hypoactivity, ataxia, twitches, tremors, prostration, urine stains, audible respiration, and perioral wetness 450 mg/kg bw/d: increased mortality, and reduced body weight gain

Remarks on result:

other: Generation: P and F1

2

Dose descriptor:

other: NOAEL (offspring)

Effect level:

ca. 175 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: based on toxic effects in the F2 litters of the high dose group animals and no clear evidence of toxic effects in F1 pups.

Remarks on result:

other: Generation: F1 and F2

3

Dose descriptor:

other: NOAEL (fertility)

Effect level:

ca. 450 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: No reproductive parameters were affected in either of the two generations.

Remarks on result:

other: Generation: P and F1

Results: F1 generation

General toxicity (F1)

Clinical signs:

not examined

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings:

not specified

Details on results (F1)

see section: "Remarks on results"

Effect levels (F1)

1

Dose descriptor:

NOAEL

Remarks:

fertility

Generation:

other: F1 and F2

Effect level:

450 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No reproductive parameters were affected in either of the two generations.

2

Dose descriptor:

NOAEL

Generation:

other: offspring

Effect level:

175 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on toxic effects in the F2 litters of the high dose group animals and no clear evidence of toxic effects in F1 pups.

Remarks on result:

other: Generation: F1 and F2

Results: F2 generation

Effect levels (F2)

1

Dose descriptor:

NOAEL

Remarks:

fertility

Generation:

other: F1 and F2

Effect level:

450 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No reproductive parameters were affected in either of the two generations.

2

Dose descriptor:

NOAEL

Generation:

other: offspring

Effect level:

175 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on toxic effects in the F2 litters of the high dose group animals and no clear evidence of toxic effects in F1 pups.

Remarks on result:

other: Generation: F1 and F2

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

Mortality: 8/28 males and 5/25 females at 450 mg/kg bw; 1/25 females at 30 mg/kg bw
Clinical signs of toxicity occurred in F0 and F1 males and females at 450 mg/kg bw/day and included hypoactivity, ataxia, twitches, tremors, prostration, urine stains, audible respiration, perinasal encrustation (not in F0 males), and perioral wetness occurred at >= 175 mg/kg bw.
body weight:
F0 adult males, sign reduced (p<0.01) week1 to week 13 in the 450 mg/kg bw group;
F0 adult females:
sign. reduced week 1 (p<0.05) in the 450 mg/kg bw-group,
gestational weight gain not significantly different from control group, lactational body weight sign. reduced (p<0.05) at d4 at 450 mg/kg bw group

F1 or F2: No reproductive parameters were affected in either of the two generations (mating index of male and females, fertility index of males and females, gestational index.

Still births in the F1 and F2 generations:
in F1 pups increased at 175 mg/kg/day (7/13 of one dam), but not at 450 mg/kg bw/day (low, mid, high dose versus control: 4/290 born pups, 13/312 born pups with 7/13 on one dam, 6/193 born pups) in F2 pups increased at 30 and 450 mg/kg bw, but not at 175 mg/kg/bw (low, mid, high dose versus control: 7/307 born pups, 4/265 born pups,9/163 born pups versus 0/318 born pups).

There was some variability in the number of stillborn in control groups in F1 and F2 generation (2 versus 0). There was no clear dose-dependent effect in both generations (control/low/mid/high dose: F1 pups: 2/4/13/6; F2 pups: 0/7/4/9).

F1,F2: Pup survival indices in both generations were not
affected by treatment (4-day survival index, 7-day survival index, 14-day survival index 21-day survival index and lactation index), except live birth indices in F2 (but not F1) which were reduced at 30 and 450 mg/kg bw, but not at 175 mg/kg/day. Without any other effects especially in the 30 mg/kg bw-group it is unclear whether the effects on live birth indices were substance related gross lesions of parental males and females which died prior to scheduled sacrifice included diffuse, focal or multifocal color changes in the lung and stained skin for males and lung congestion and congestion in the nasal turbinates and erythrocytes on the skin surface for females.
There were no treatment related histologic lesions observed in the examination of organs from parental F0 and F1 adults which survived to scheduled sacrifice.

Applicant's summary and conclusion

Executive summary:

Reproductive toxicity was examined in a two-generation toxicity study according to TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects. Sprague-Dawley rats were given daily 0, 30, 175, or 450 mg/kg bw/day p-cresol in corn oil by gavage. No effects on fertility were detected despite overt general toxicity including increased mortality and reduced body weight gain at 450 mg/kg bw and at >= 175 mg/kg bw/day hypoactivity ataxia, twitches, tremors, prostration, urine stains, audible respiration and perioral wetness. Thus, the NOAEL(fertility) was 450 mg/kg bw/day and the NOAEL(general toxicity) was 30 mg/kg bw/day. The NOAEL(offspring) is 175 mg/kg bw/day due to toxic effects in the F2 litters of the high dose group animals and no clear evidence of toxic effects in F1 pups.