o-cresol

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

According to TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects (EPA, 1983) o-cresol was continuously administered by gavage to Sprague-Dawley rats for two generations and resulted in general toxicity including increased mortality at 450 mg/kg bw/d and in clinical signs of toxicity including hypoactivity, ataxia, twitches, tremors, prostration, gasping, rapid respiration and perioral wetness at >= 175 mg/kg bw/d (NOAEL (general toxicity) 30 mg/kg bw/d). No reproductive parameters were affected by treatment in either of the two generations (NOAEL (fertility) 450 mg/kg bw/d. The NOAEL (offspring) is 175 mg/kg bw/d based on significantly reduced body weights in F1 males and in significantly reduced lactation index in F2 at 450 mg/kg bw (Union Carbide Corp 1989).

Link to relevant study records

Reference

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:

guideline study

Qualifier:

according to guideline

Guideline:

other: TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects (EPA, 1983)

GLP compliance:

yes

Limit test:

no

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 wks (P) ;
- Weight at study initiation: (P) Males: 193-194g; Females: ca. 151 g;
- Housing: initially 2/same sex during acclimation period; and then singly except for the cohabitation and lactation periods
- Diet : ad libitum
- Water : ad libitum
- Acclimation period: 14 days


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

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 / sperm in vaginal smear 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

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A standard stock solution was prepared (1mg/ml propanol),which was used to prepare standards ranging fron 10 to 100 ng/µl. With these solutiower a standard curve was generated using HPLC. Dosing formulation concentrations were veryfied by preparing aliquots which were injected onto the 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 w
Premating exposure period (males): 10 weeks
Premating exposure period (females): 10 weeks

Frequency of treatment:

once per day , 5 d/w
F1 generation producing F2: once per day, 7 days per week

Details on study schedule:

at day 28-40 post partum F1 animals selected to be parents of the F2 generation were gavaged with their respective formulations for at least
11 weeks 5 days/week.
the F1 animals were approximately 15 to 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

Remarks:

Doses / Concentrations:
0, 30, 175, 450 mg/kg/day in corn oil
Basis:
actual ingested

No. of animals per sex per dose:

25 animals/sex/group

Control animals:

yes, concurrent vehicle

Details on study design:

no further data

Positive control:

no data

Parental animals: Observations and examinations:

Mortality: twice daily
General conditon: 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 determination
male, female: initially and weekly until mating
female during gestation : day 0, 7, 13, 20 post partum: day 0, 4, 7, 14, 21
Food consumption
measured weekly during pre-breed dosing period for P and F1 generation; all other phases of this sutdy determination was made visually

Oestrous cyclicity (parental animals):

Vaginal smears were examined to determe 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 was 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 weaned


GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.
A complete gross necropsy was conducted for any parental animal dying on test.


HISTOPATHOLOGY
Male and female adult rats of the highest dose groups and the controls
The tissues as indicated below, were prepared for microscopic examination and weighed, respectively:
pituitary, vagina, uterus, ovaries, testes, epididymides, 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 neccropsied 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 cexamined for gross external abnormalities , euthanized and discarded.

Statistics:

Levene's test for equal variances, analysis of variance (ANOVA), t-test, 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 impregnating females devided through the total number of males paired multiplied by 100
---for females: number of females with copulation plugs devided through the mumger of females cohabited multiplied by 100

Fertility Index(%):
---for males: number of males producing pregnant females devided through number of males impregnating females multiplied by 100
---for females. number of pregnant females devided through number of plug-positive females multiplied by 100

Gestational Index (%)
number of females with live litters devided through number of females pregnant multiplied by 100

Offspring viability indices:

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

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 examined

Histopathological findings: non-neoplastic:

not specified

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

see section "remarks on results"

Dose descriptor:

other: NOAEL (fertility)

Effect level:

450 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: There were no treatment related reproductive effects observed in this study.

Remarks on result:

other: Generation: F0 and F1 (parental)

Dose descriptor:

other: NOAEL (offspring)

Effect level:

175 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: F1 (males) significantly reduced body weights at 450 mg/kg bw group F2: Significantly reduced lactation index in the 450 mg/kg bw group.

Remarks on result:

other: Generation: F1 and F2

Dose descriptor:

other: NOAEL (general toxicity)

Effect level:

30 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: 450mg/kg bw: increased mortaliity; 450 and 175 mg/kg bw/d: Signs of intoxication

Remarks on result:

other: Generation: F0 and F1

Critical effects observed:

yes

Lowest effective dose / conc.:

175 mg/kg bw/day (nominal)

System:

other:

Organ:

other: 450mg/kg bw: increased mortaliity; 450 and 175 mg/kg bw/d: Signs of intoxication

Treatment related:

yes

Dose response relationship:

yes

Clinical signs:

not specified

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings:

not specified

see section " remarks on results"

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

175 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: F1 (males) significantly reduced body weights at 450 mg/kg bw group F2: Significantly reduced lactation index in the 450 mg/kg bw group

Remarks on result:

other: Generation: F1 and F2

Critical effects observed:

yes

Lowest effective dose / conc.:

450 mg/kg bw/day (nominal)

Organ:

other: F1 (males) significantly reduced body weights at 450 mg/kg bw group F2: Significantly reduced lactation index in the 450 mg/kg bw group.

Treatment related:

yes

Dose response relationship:

yes

Dose descriptor:

NOAEL

Generation:

F2

Effect level:

175 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: F1 (males) significantly reduced body weights at 450 mg/kg bw group F2: Significantly reduced lactation index in the 450 mg/kg bw group.

Critical effects observed:

yes

Lowest effective dose / conc.:

450 mg/kg bw/day (nominal)

Organ:

other: F1 (males) significantly reduced body weights at 450 mg/kg bw group F2: Significantly reduced lactation index in the 450 mg/kg bw group.

Treatment related:

yes

Dose response relationship:

yes

Reproductive effects observed:

no

F0-generation:
---Mortality during pre-breed period:
450 mg/kg bw/d males: 12/25 and females: 8/25
---Signs of intoxication.
450 mg/kg bw/d, males and females:
hypoactivity, ataxia, twitches, tremors, prostration, gasping, rapid respiration, lacrimation, amd perioral wetness occurred immediately after dosing but did not persist until the next day.
---Mean weight gain in F0 males and F0 females were equivalent across the groups
---Mean body weight, significantly reduced: males: 175 mg-gr., 450 mg-gr., week 13: 489.9 g,470.9 g versus 522 g of controls.

---Reproductive parameters for F0 parents at F1 breed:
Mating index (males and females), fertility index (males and females) and gestational index were not affected by treatment.
--Body weight development during gestation and lactation was equivalent across the groups.
--F1-pups:
-Live-birth index was comparable across the groups, sex ratio was not affected
-Survival Indices: 4-day-, 7-day-, 14-day- and 21-day-survival indices and lactation index were equivalent across the groups.
450 mg/kg bw/d,males (pre-breed period): significantly reduced mean body weights: 139.6 g versus 162 g in controls
F1-adult-generation
---Signs of intoxication.
450 mg/kg bw/d, males and females: hypoactivity, ataxia, twitches, tremors, prostration, gasping, rapid respiration, lacrimation, and perioral wetness.
175 mg/kg bw/d:
males: perioral wetness
females: hypoactivity, ataxia, perioral wetness
---Mortality
450 mg-group:
pre-breed period: 8 males and 14 females
additionally:
7 males and 9 females died prior to mating, 3 females which were found pregnant died and another one died during gestation
---body weight and weight development
females: equivalent across the groups
males: week 14, low, mid, high dose: 586.6 g, 564.1 g, 494.4 g versus 526.3 g of controls
---Reproductive parameters for F1 parents at F2 breed:
Mating index (males and females), fertility index (males and females) and gestational index were not affected by treatment.
--Body weight development during gestation and lactation was equivalent across the groups.
--F2-pups:
-Live-birth index was comparable across the groups, sex ratio was not affected
-Survival Indices: 4-day-, 7-day-, 14-day- and 21-day-survival indices were equivalent across the groups.
lactation index
450 mg-group: was significantly reduced (75.5 versus 99.4 in controls)

Conclusion:
The A/D ratio (the dose level at which there were no observable effects in offsprings) is less than 1: (30/175) indicating no increased risk to offspring from o-cresol in the absence of parental effects.

Executive summary:

Two-generation reproductive toxicity according to TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects (EPA, 1983)

Continued administration of o-cresol by gavage for two generations to Sprague-Dawley rats resulted in general toxicity including increased mortality at 450 mg/kg bw/d and in clinical signs of toxicity including hypoactivity, ataxia, twitches, tremors, prostration, gasping, rapid respiration and perioral wetness at >= 175 mg/kg bw/d (NOAEL (genral toxicity) 30 mg/kg bw/d). No reproductive parameters were affected by treatment in either of the two generations (NOAEL (fertility) 450 mg/kg bw/d.

The NOAEL (offspring) is 175 mg/kg bw/d based on significantly reduced body weights in F1 males and in significantly reduced lactation index in F2 at 450 mg/kg bw.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

450 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

GLP guideline study

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

According to TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects (EPA, 1983) o-cresol was continuously administered by gavage to Sprague-Dawley rats for two generations and resulted in general toxicity including increased mortality at 450 mg/kg bw/d and in clinical signs of toxicity including hypoactivity, ataxia, twitches, tremors, prostration, gasping, rapid respiration and perioral wetness at >= 175 mg/kg bw/d (NOAEL (general toxicity) 30 mg/kg bw/d). No reproductive parameters were affected by treatment in either of the two generations (NOAEL (fertility) 450 mg/kg bw/d. The NOAEL (offspring) is 175 mg/kg bw/d based on significantly reduced body weights in F1 males and in significantly reduced lactation index in F2 at 450 mg/kg bw (Union Carbide Corp 1989).

Additionally, testing for reproductive toxicity of o-cresol in mice using the NTP continuous breeding protocol (0, 0.05 - 0.5 %, approximately 66 - 660 mg/kg bw/d in the diet) resulted in a NOAEL for reproduction as well as for general toxicity of 0.2 % (ca. 263 mg/kg bw/d US Department of Health and Human Services 1992).

Reproduction studies were performed with mink (one generation; Hornshaw et al., 1986), rats (two generations; Union Carbide, 1989) and mice (two generations; Izard et al., 1992). None of these studies indicated increased risks to offspring from o-cresol in the absence of parental effects. NOAELs for parental toxicity were 25-40 mg/kg bw/day for mink and 30 mg/kg bw/day for rats

(OECD SIDS o-Cresol, CAS N°: 95-48-7, UNEP publication).

Two-generation reproduction studies in rats (up to 450 mg/kg/day of each isomer by gavage) and mink (up to 105 mg/kg/day dietary o-cresol for 6 months) also failed to detect adverse effects on reproductive function or lesions in reproductive tissues. These studies also included doses producing maternal toxicity. No histopathological lesions and only mild organ weight changes of doubtful significance were reported in the reproductive organs of animals exposed to up to 600 mg/kg/day of cresols by gavage for 13 weeks.

Two studies have evaluated the effects of o-cresol and a mixture of m/p-cresol on reproductive function end points in CD-1 mice using a continuous breeding protocol (NTP 1992). End points evaluated included fertility, mean number of litters per pair, live litter size, weight and histopathology of reproductive organs, vaginal cytology, and sperm parameters. Both studies started with a 14-week

cohabitation period in which males and females received the test material in the diet. The highest doses during this period were 660 mg/kg/day for o-cresol and 1,682 mg/kg/day for m/p-cresol. No significant alterations were observed with o-cresol at any stage of the study. However, the highest dose of m/p-cresol significantly decreased the number of live pups/litter and increased the cumulative days to litter; a dose level of 1,390 mg/kg/day was a NOAEL. To determine which sex was the affected sex during the cohabitation period, a 1-week crossover mating trial was conducted, but the results indicated that either sex could have been affected. In neither study was fertility affected. In addition, sperm parameters and gross and microscopic morphology of reproductive organs were not affected by treatment with the cresols (U.S. DEPART- MENT OF HEALTH AND HUMAN SERVICES, Public Health Service, Agency for Toxic Substances and Disease RegistrySeptember 2008).

.

Short description of key information:
According to TSCA Health Effects Test Guideline for specific organ/tissue toxicity - Reproduction/Fertility effects (EPA, 1983) up to 450 mg/kg bw/dayo-cresol was continuously administered by gavage to Sprague-Dawley rats for two generations and resulted in NOAEL(general toxicity) ) 30 mg/kg bw/d), NOAEL (fertility) 450 mg/kg bw/d and NOAEL (offspring) 175 mg/kg bw/d

Justification for selection of Effect on fertility via oral route:
Key study used

Effects on developmental toxicity

Description of key information

In rats and rabbits no developmental effects were observed for o-cresol below the NOAEL used for the systemic toxicity risk assessment (50 mg/kg bw/day).

Link to relevant study records

Reference

Reference 1

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: TSCA Health Effect Guidelines for Specific Organ/Tissue Toxicity - Developmental Toxicity (EPA 1984, 1987)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory, Kingston N
- Weight at study initiation: 228-230 g
- Housing: after mating singly
- Diet :. ad libitum
- Water : ad libitum
- Acclimation period: 2 week

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 72
- Humidity (%): 40-60
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12/12

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.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A standard stock solution (1 mg/ml) was prepared as needed by weighing 50 mg o-cresol into a 50 ml volumetric flask and diuting to volume with propanol. Standards ranging vrom 10 to 100 ng/ml were prepared by diluting the stock solution with propanol. 10 µl of each standard was injected onto the HPLC . The actual concentration of each dosing solution was calculated from the equitation for the standard curve developed by linear regression.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy

Duration of treatment / exposure:

10 d (gd 6-15)

Frequency of treatment:

once daily

Duration of test:

gd 21 (scheduled sacrifice)

No. of animals per sex per dose:

25 females /group, 50 control females

Control animals:

yes, concurrent vehicle

Details on study design:

mo further data

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations : mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: gd 0, 6, 11, 15, 21


FOOD CONSUMPTION Yes
- Food consumption for each animal determined throughout gestation gd 0-21


WATER CONSUMPTION No


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: body weight, liver, gravid uterine weight, number of corpora lutea, number and status of implantation sites:

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: half per litter

Statistics:

Levene's test for equal variances, ANOVA, pooled t-test with Bonferroni probabilities for pairwise comparison, Kruskal-Wallis test, Mann-Whitney U-test, Fisher's exact test.

Indices:

no data

Historical control data:

no data

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
see section "Remarks on results"

Dose descriptor:

NOAEL

Effect level:

ca. 175 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Remarks on result:

other:

Remarks:

450 mg/kg bw/day: treatment related clinical signs including hypoactivity, ataxia, tremor, twitches, prone positioning, audible respiration, perioral wetness, mortality of 4 dams, statistically significant reduction in body weights and body weight gain.

Dose descriptor:

NOAEL

Effect level:

ca. 175 mg/kg bw/day

Basis for effect level:

other: developmental toxicity

Remarks on result:

other:

Remarks:

450 mg/kg bw: slight fetotoxicity: one visceral variation: dileted lateral ventricles of the brain with no tissue compression.

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
see section "Remarks on result"

Dose descriptor:

NOAEL

Effect level:

ca. 175 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: 450 mg/kg bw: slight fetotoxicity: one visceral variation: dilated lateral ventricles of the brain with no tissue compression.

Abnormalities:

not specified

Localisation:

other: 450 mg/kg bw: slight fetotoxicity: one visceral variation: dilated lateral ventricles of the brain with no tissue compression.

Description (incidence and severity):

450 mg/kg bw: slight fetotoxicity: one visceral variation: dilated lateral ventricles of the brain with no tissue compression.

Developmental effects observed:

yes

Lowest effective dose / conc.:

450 mg/kg bw/day

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

---Maternal toxicity:
450 mg-group:
4/25 died,
significant reduction in periodic maternal body weight and
weight gain during dosing,
reduction of food consumption,
clinical signs: at 450 mg/kg bw
hypoactivity, ataxia, tremor, twitches, prone positioning,
audible respiration, perioral wetness,

for all groups: gestational parameters uneffected, no early
delivery, no abortion;

---Evaluation of offspring:
450 mg/kg bw: slight fetotoxicity:
one visceral variation: dileted lateral ventricles of the
brain with no tissue compression;
NOEL (maternal): 175.0 mg/kg bw/day
NOEL (developmental): 175.0 mg/kg bw/day

Conclusions:

The NOAEL (developmental toxicity) is 175 mg/kg bw/d.

Executive summary:

Developmental toxicity study according to TSCA Health Effect Guidelines for Specific Organ/Tissue Toxicity - Developmental Toxicity (EPA 1984, 1987):

Administration of o-cresol by gavage to time-pregnant Sprague-Dawley rats during organogenesis at 0.0, 30.0, 175.0, 450.0 mg/kg bw/d resulted in significant maternal toxicity at 450 mg/kg bw/d including treatment related clinical signs (hypoactivity, ataxia, tremor, twitches, prone positioning, audible respiration, perioral wetness), mortality of 4 dams, statistically significant reduction in body weights and body weight gain (NOAEL (maternal toxicity) 175 mg/kg bw/d). Slight fetotoxicity only at 450 mg/kg bw/d as one visceral variation (dilateted lateral ventricles of the brain with no tissue compression). Thus the NOAEL (developmental toxicity) is 175 mg/kg bw/d.

Reference 2

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: TSCA Health Effects Test Guidelines for Specific Organ/Tessue Toxicity-Developmental Toxicity (EPA, 1984, 1987)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hazleton-DeuchlandLaboratories Inc., Denver, PA
- Age at study initiation: 5.5 months
- Weight at study initiation: 2.5 kg
- Housing: after mating: singly
- Diet : e.g. ad libitum
- Water :. ad libitum
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°F): 72
- Humidity (%): 40-60
- Photoperiod (hrs dark / hrs light): 12/12

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

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A standard stock solution (1 mg/ml) was prepared as needed by weighing 50 mg o-cresol into a 50 ml volumetric flask and ddiluting to volume with propanol. Standards ranging from 10 to 100 ng/ml were prepared by diluting the stock solution with propanol. 10 ml of each stndard was injected onto the HPLC. The actual concentration of each dosing solution was calculated from the equitation for the standard curve developed by linear regression

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnan

Duration of treatment / exposure:

13 d (gd 6-18)

Frequency of treatment:

once daily

Duration of test:

until gd 29

No. of animals per sex per dose:

14 females /group, control females: 28

Control animals:

yes, concurrent vehicle

Details on study design:

Sex: female
Duration of test: until gd 29

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily


BODY WEIGHT: Yes
- Time schedule for examinations: gd 0,6, 12, 18, 24, 29


FOOD CONSUMPTION Yes

WATER CONSUMPTION: No


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 29
- Organs examined: stomach gland, liverm gall bladderm kidneysm uterus

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
The ovaries and uterine content was examined after termination: Yes / No / No data
Examinations included:
- Gravid uterus weight: Yes / No / No data
- Number of corpora lutea: Yes / No / No data
- Number of implantations: Yes / No / No data
- Number of early resorptions: Yes / No / No data
- Number of late resorptions: Yes / No / No data
- Other: number of fetus alive and number of dead fetuses

Fetal examinations:

-determination of the number of fetuses alive: yes
-determination of the number of dead fetuses: yes
-determination of sex ratio: yes
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: half per litter

Statistics:

Levene's test, ANOVA with Bonferroni prohability,pooled t-test, Kruskal -Wallis test, Mann-Whitney U test, Fisher's exact test

Indices:

no data

Historical control data:

no data

Details on maternal toxic effects:

Maternal toxic effects: yes

Details on maternal toxic effects:
see section "Remarks on results"

Dose descriptor:

NOEL

Effect level:

ca. 5 mg/kg bw/day

Basis for effect level:

other: other:

Remarks on result:

other:

Remarks:

>= 50 mg/kg bw/d: clinical signs of toxicity including hypoactivity, audible respiration, ocular discharge.

Dose descriptor:

NOAEL

Effect level:

ca. 50 mg/kg bw/day

Basis for effect level:

other: developmental toxicity

Remarks on result:

other:

Remarks:

100 mg/kg bw/day: slight fetotoxicity (increased incidence of 1 external variation and 1 skeletal variation) in the absence of any other indications of toxicity for the conceptus.

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

Remarks on result:

other:

Remarks:

no abortions, no early deliveries, gestational parameters were not affected.

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
see section "Remarks on results"

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: 100 mg/kg bw/day: slight fetotoxicity (increased incidence of 1 external variation and 1 skeletal variation) in the absence of any other indications of toxicity for the conceptus.

Abnormalities:

not specified

Description (incidence and severity):

100 mg/kg bw/day: slight fetotoxicity (increased incidence of 1 external variation and 1 skeletal variation) in the absence of any other indications of toxicity for the conceptus

Developmental effects observed:

yes

Lowest effective dose / conc.:

100 mg/kg bw/day

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

---all groups:
No treatment related deaths, no significant changes in periodic maternal body weights or weight gain, no treatment related effects on food consumption, no abortions, no early deliveries, gestational parameters were not affected;
---clinical observations:
50.0 and 100.0 mg-group:
audible respiration, ocular discharge

---Evaluation of offspring
100.0 mg-group: slight fetotoxicity:
Ecchymosis on the head: 4/129 fetuses in 4/14 litters versus none in controls, poorly ossified sternum: 52/129 fetuses in 14/14 litters versus 62/212 fetuses in 16/23 litters.

NOEL (clinical signs): 5.0 mg/kg bw/day
NOAEL (developmental): 50 mg/kg bw/day

NOAEL (maternal toxicity): 100 mg/kg bw/d       

Executive summary:

Developmetal toxicity study according to TSCA Health Effects Test Guidelines for Specific Organ/Tessue Toxicity-Developmental Toxicity (EPA, 1984, 1987):

Administration of o-cresol by gavage to time-pregnant New Zealand White rabbits during organogenesis at 0.0, 5.0, 50.0 or 100 mg/kg bw/d caused in dams hypoactivity, audible respiration, ocular discharge from 50 mg/kg bw/d onwards (NOAEL general toxicity: 5 mg/kg bw/day) and slight fetotoxicity observed as increased incidence of one external variation and one skeletal variation in the absence of any other indications of toxicity for the conceptus at 100 mg/kg bw/day: NOAEL (developmental toxicity): 50 mg/kg bw/d. Based on the fact that no abortions, no early deliveries were observed and gestational parameters were not affected: NOAEL (maternal toxicity): 100.0 mg/kg bw/d

                   

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

175 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

GLP gudieline study

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

To determine developmental toxicity according to TSCA Health Effect Guidelines for Specific Organ/Tissue Toxicity - Developmental Toxicity (EPA 1984, 1987) o-cresol was administered by gavage to timed-pregnant Sprague-Dawley rats during organogenesis (gestation day 6-15; 0.0, 30.0, 175.0, 450.0 mg/kg bw/d) and resulted in significant maternal toxicity at 450 mg/kg bw/d including treatment related clinical signs (hypoactivity, ataxia, tremor, twitches, prone positioning, audible respiration, perioral wetness), mortality of 4 dams, statistically significant reduction in body weights and body weight gain leading to a NOAEL (maternal toxicity) 175 mg/kg bw/d). Slight fetotoxicity was observed only at 450 mg/kg bw/d as one visceral variation (dilateted lateral ventricles of the brain with no tissue compression). Thus the NOAEL (developmental toxicity) is 175 mg/kg bw/d (CMA 1988).

Additionally, administration of o-cresol by gavage to time-pregnant New Zealand White rabbits during organogenesis (same guideline, gestaion day 6 through 18, 0.0, 5.0, 50.0 or 100 mg/kg bw/d) caused clinical signs of toxicity in dams including hypoactivity, audible respiration, ocular discharge from 50 mg/kg bw/d onwards (NOAEL general toxicity: 5 mg/kg bw/day) and slight fetotoxicity observed as increased incidence of one external variation and one skeletal variation in the absence of any other indications of toxicity for the conceptus at 100 mg/kg bw/day:: NOAEL (developmental toxicity): 50 mg/kg bw/d  Based on the fact that no abortions, no early deliveries were observed and gestational parameters were not affected: NOAEL (maternal toxicity): 100.0 mg/kg bw/d

A developmental study in rats (gd 6 - 15) showed slight fetotoxicity in the highest dose group (450 mg/kg bw/day) only. The NOEL for maternal and developmental toxicity was 175 mg/kg bw/day (Union Carbide, 1988). In rabbits, o-cresol caused fetotoxicity in the highest dose group of 100 mg/kg bw/day. The NOEL for developmental toxicity was established at 50 mg/kg bw/day (Union Carbide, 1988)(OECD SIDS o-Cresol, CAS N°: 95-48-7, UNEP publication).

.

Developmental toxicity studies in which pregnant rats and rabbits were exposed to cresols by gavage during gestation reported no effects on the reproductive parameters investigated (e.g., number of ovarian corpora lutea, number of implantation sites, number of viable fetuses), even at maternally toxic doses (U.S. DEPART- MENT OF HEALTH AND HUMAN SERVICES, Public Health Service, Agency for Toxic Substances and Disease RegistrySeptember 2008)

                 

Justification for selection of Effect on developmental toxicity: via oral route:
key study in rats is used

Toxicity to reproduction: other studies

Additional information

no data

Justification for classification or non-classification

Classification is not required