α-phenyl-1H-benzimidazole-2-methanol

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

NOAEL (Reproduction) = 350 mg/kg bw/d; OECD 422; S. Fulcher. (2019)

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 June 2018 to TBC

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

2016

Deviations:

yes

Remarks:

Deviation from target value for relative humidity (RH) from 50 ± 20% to 76%, but the study was unaffected.

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EC) No 440/2008 of 30 May 2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).

Version / remarks:

2008

Deviations:

yes

Remarks:

Deviation from target value for relative humidity (RH) from 50 ± 20% to 76%, but the study was unaffected.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Wistar HanTM:RccHanTM:WIST strain

Details on species / strain selection:

Based on guideline requirement

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Envigo RMS (UK) Limited, Blackthorn, Bicester, Oxon, UK
- Females (if applicable) nulliparous and non-pregnant: yes

- Date of birth: Not specified

- Age at study initiation: male 11 weeks and female 12 weeks

- Weight at study initiation: Male 284 to 354g and female 193 to 225g
- If immature animals, whether or not supplied with dam or foster dam and date of weaning: N/A

- Fasting period before study: No

- Housing: Groups of three in solid floor polypropylene cages with stainless steel mesh lids and softwood flake bedding (Datesand Ltd., Cheshire, UK). During the pairing phase, animals were transferred to polypropylene grid floor cages suspended over trays lined with absorbent paper on a one male: one female basis within each dose group. Following evidence of successful mating, the males were returned to their original cages. Mated females were housed individually during gestation and lactation in solid floor polypropylene cages with stainless steel mesh lids and softwood flakes.
- Diet (e.g. ad libitum): Free access to food, a pelleted diet (Rodent 2018C Teklad Global Certified Diet, Envigo RMS (UK) Limited, Oxon, UK.) was used.
- Water (e.g. ad libitum): Free access to mains drinking water supplied from polycarbonate bottles attached to the cage.
- Acclimation period: 20 days



DETAILS OF FOOD AND WATER QUALITY


ENVIRONMENTAL CONDITIONS

- Temperature (°C):22 ± 3 °C
- Humidity (%): 50 ± 20%
- Air changes (per hr): The rate of air exchange was at least fifteen air changes per hour.
- Photoperiod (hrs dark / hrs light): Low intensity fluorescent lighting was controlled to give twelve hours continuous light and twelve hours darkness

IN-LIFE DATES: From: To: Not indicated

Route of administration:

oral: gavage

Vehicle:

other: Polyethylene glycol 400 (PEG 400)

Details on exposure:

The test item was administered daily by gavage using a stainless steel cannula attached to a disposable plastic syringe. The volume of test and control item administered to each animal were based on the most recent scheduled body weight and adjusted accordingly.
PREPARATION OF DOSING SOLUTIONS:
 The test item was prepared at the appropriate concentrations in Polyethylene glycol 400 (PEG 400). Formulations were therefore prepared in batches of up to two weeks and made up to three days in advance of first use and stored at approximately 4oC in the dark.

 VEHICLE 
 - Justification for use and choice of vehicle (if other than water): The substance was miscible in Polyethylene glycol 400 grade
- Concentration in vehicle: 99-104% of the nominal concentration
- Amount of vehicle (if gavage): Dose Volume of 6mL/kg
- Lot/batch no. (if required): 1729820

- Purity: Not stated

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: up to 2 weeks
- Proof of pregnancy: vaginal plug and sperm in vaginal smear referred to as Day 0 of pregnancy.
- Further matings after unsuccessful attempts: no
- After successful mating each pregnant female was caged (how): housed individually in a cages comprised of a polycarbonate body with a stainless steel mesh lid.
- Any other deviations from standard protocol:no

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytical procedure was successfully validated with respect to specificity of chromatographic analysis, linearity of detector response, method accuracy and precision.

The homogeneity and stability was confirmed for the test item in PEG 400 formulations at nominal concentration of 3.75 mg/mL and 250 mg/mL when stored refrigerated for 18 days.

The mean concentrations of the test item formulations analysed for the study were within +/- 10% of nominal concentrations, confirming accurate formulation.

Duration of treatment / exposure:

6 - 8 weeks

Frequency of treatment:

Daily

Details on study schedule:

Chronological Sequence of Study
i. Males and females were housed for a suitable acclimatization period which allowed at least two weeks of pre-treatment vaginal smears to be performed for females enabling the exclusion of females not showing appropriate estrous cycling.
ii. Groups of twelve male and twelve female animals were treated daily at the appropriate dose level throughout the study (except for females during parturition where applicable). The first day of dosing was designated as Day 1 of the study.
iii. Prior to the start of treatment and once weekly thereafter, all animals were observed for signs of functional/behavioral toxicity.
iv.On Day 15, animals were paired on a 1 male: 1 female basis within each dose group for a maximum of fourteen days.
v. Following evidence of mating (designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages.
vi. On completion of the pairing phase, five selected males per dose group were evaluated for functional/sensory responses to various stimuli during Week 6.
vii. Pregnant females were allowed to give birth and maintain their offspring until Day 13 post partum. Litter size, offspring weight and sex, ano-genital distance, visible nipple counts (male offspring) and clinical signs were also recorded during this period.
viii. On Day 4 post partum, where possible, blood sampling was performed on two randomly allocated offspring from each litter in order to obtain serum samples.
ix. At Day 12 post partum, five selected females per dose group were evaluated for functional/sensory responses to various stimuli.
x. Blood samples were taken from five males from each dose group for hematological and blood chemical assessments on Day 43. The male dose groups were killed and examined macroscopically on Day 44 or 45.
xi. On Day 13 post partum, where possible, blood sampling to produce serum samples for assessment of thyroid hormones was performed on two randomly selected offspring (one male and one female) per litter. Where possible, a further two randomly selected offspring (one male and one female) per litter were sampled to produce surther serum samples as a contingency against the need to measure TSH. Thyroid/parathyroid samples were also retained from one male and one female from each litter where litter sizes allowed. All surviving offspring were killed and examined externally; where external observations were detected an internal necropsy was performed.
xii. Blood samples were taken from five randomly selected females from each dose group for hematological and blood chemical assessment on Day 13 post partum. All surviving females were sacrificed on Day 14 post partum and examined macroscopically. A vaginal smear was also performed for all females in the morning of the day of necropsy. In addition, blood samples to produce both serum and plasma were taken from all adult animals at termination. Blood samples from all adult males and Day 13 offspring were analyzed for Thyroxine (T4).
xiii. Selected tissues were taken from five males from Groups 2 to 4 and all 3 positive control males (Group 5) for subsequent processed as part of the comet assay assessment.

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

1. Control

Dose / conc.:

100 mg/kg bw/day (nominal)

Remarks:

2. Low

Dose / conc.:

350 mg/kg bw/day (nominal)

Remarks:

3. Intermediate

Dose / conc.:

750 mg/kg bw/day (nominal)

Remarks:

4. High

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Details on study design:

i. Males and females were housed for a suitable acclimatization period which allowed at least two weeks of pre-treatment vaginal smears to be performed for females enabling the exclusion of females not showing appropriate estrous cycling.
ii. Groups of twelve male and twelve female animals were treated daily at the appropriate dose level throughout the study (except for females during parturition where applicable). The first day of dosing was designated as Day 1 of the study.
iii. Prior to the start of treatment and once weekly thereafter, all animals were observed for signs of functional/behavioral toxicity.
iv. On Day 15, animals were paired on a 1 male: 1 female basis within each dose group for a maximum of fourteen days.
v. Following evidence of mating (designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages.
vi. On completion of the pairing phase, five selected males per dose group were evaluated for functional/sensory responses to various stimuli during Week 6.
vii. Pregnant females were allowed to give birth and maintain their offspring until Day 13 post partum. Litter size, offspring weight and sex, ano-genital distance, visible nipple counts (male offspring) and clinical signs were also recorded during this period.
viii. On Day 4 post partum, where possible, blood sampling was performed on two randomly allocated offspring from each litter in order to obtain serum samples.
ix. At Day 12 post partum, five selected females per dose group were evaluated for functional/sensory responses to various stimuli
x.Blood samples were taken from five males from each dose group for hematological and blood chemical assessments on Day 43. The male dose groups were killed and examined macroscopically on Day 44 or 45.
xi.On Day 13 post partum, where possible, blood sampling to produce serum samples for assessment of thyroid hormones was performed on two randomly selected offspring (one male and one female) per litter. Where possible, a further two randomly selected offspring (one male and one female) per litter were sampled to produce surther serum samples as a contingency against the need to measure TSH. Thyroid/parathyroid samples were also retained from one male and one female from each litter where litter sizes allowed. All surviving offspring were killed and examined externally; where external observations were detected an internal necropsy was performed.
xii.Blood samples were taken from five randomly selected females from each dose group for hematological and blood chemical assessment on Day 13 post partum. All surviving females were sacrificed on Day 14 post partum and examined macroscopically. A vaginal smear was also performed for all females in the morning of the day of necropsy. In addition, blood samples to produce both serum and plasma were taken from all adult animals at termination. Blood samples from all adult males and Day 13 offspring were analyzed for Thyroxine (T4).
xiii.Selected tissues were taken from five males from Groups 2 to 4 and all 3 positive control males (Group 5) for subsequent processed as part of the comet assay assessment.

Positive control:

Three males were dosed with N- Nitroso-N-methylurea (vehicle: distilled water) for two consecutive days to act as a positive control group for the comet assay investigation.

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Throughout the study
- Cage side observations checked in table [No.?] were included. Yes


DETAILED CLINICAL OBSERVATIONS: Yes

- Time schedule:
Group 1 - 4: 30 mins post dosing & an hour after dosing. Comet male, immediately before dosing and up to 30 mins post dosing. 
Group 5: Daily but formal recording began on day 44 when observations were made immediately before dosing and up to 30 mins post dosing and day 45 only immediately before dosing and up to 30 mins post dosing.

BODY WEIGHT: Yes 
- Time schedule for examinations:
Groups 1 to 4: Individual body weights were recorded for males on Day -5 (Day of allocation), Day 1 and then weekly until termination. Individual body weights were also recorded at terminal kill.
For females, individual body weights were recorded on Day -5 (Day of allocation), Day 1 and then weekly until pairing. During the pairing phase, females were weighed daily until mating was confirmed. Mated females were weighed on Day 0, 7, 14 and 20 post coitum and body weights for females which give birth were recorded on Days 1, 4, 7 and 14 post partum.
Group 5:
During the pre-treatment period, individual body weights will be recorded on a weekly basis to coincide with the scheduled weighing of Group 1 to 4 animals. Individual body weights were recorded on Day 44 (prior to start of dosing) and were also recorded on the day of termination (Day 45).
Individual body weights were recorded on Day 1 (prior to dosing) and then weekly for males until termination and weekly for females until pairing. During pairing phase females were weighed daily until mating was confirmed. Body weights were then recorded for females on Days 0, 7, 14 and 20 post coitum, and on Days 1, 4, 7 and 14 post partum. Body weights were also recorded at terminal kill.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule for examinations:
Group 1 to 4: During the pre-pairing period, weekly food consumption was recorded for each cage of adults. This was continued for males after the mating phase. For females showing evidence of mating, food consumption was recorded for the periods covering post coitum Days 0-7, 7-14 and 14-20. For females during lactation, food consumption was recorded for the periods covering post partum Days 1-4, 4-7 and 7-14.
Group 5: No formal measurement of food consumption was performed for these animals.

FOOD EFFICIENCY: Yes
- Time schedule for examinations:
Group 1 to 4: Food efficiency (the ratio of body weight change/dietary intake) was calculated retrospectively for males throughout the study period (with the exception of the mating phase) and for females during the pre-pairing phase. Due to offspring growth and milk production, food efficiency could not be accurately calculated during gestation and lactation.


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes 
- Time schedule for examinations: Daily



OPHTHALMOSCOPIC EXAMINATION: No

- Time schedule for examinations:

- Dose groups that were examined:



HAEMATOLOGY: Yes 

- Time schedule for collection of blood: Male day 43 & female Day 13 Post partum

- Anaesthetic used for blood collection: No

- Animals fasted: No
- How many animals: Five male and five female from groups 1 -4

- Parameters checked in table [No.?] were examined. Yes



CLINICAL CHEMISTRY: Yes

- Time schedule for collection of blood:Male day 43 & female Day 13 Post partum
- Animals fasted: No

- How many animals:Five male and five female from groups 1 -4
- Parameters checked in table [No.?] were examined. Yes



URINALYSIS: No

- Time schedule for collection of urine:

- Metabolism cages used for collection of urine: 

- Animals fasted: 

- Parameters checked in table [No.?] were examined.



NEUROBEHAVIOURAL EXAMINATION: Yes 

- Time schedule for examinations: Prior to the start of treatment and at approximately weekly intervals thereafter, all animals were observed for signs of functional/behavioral toxicity. These observations were performed on mated females on Days 4, 11 and 18 post coitum and for littering females on Days 4 and 12 post partum. Functional performance tests were also performed on five selected males and females from each dose level, prior to termination, together with an assessment of sensory reactivity to various stimuli.

- Dose groups that were examined:Groups 1 - 4
- Battery of functions tested: sensory activity / grip strength / motor activity /: All
other: Behaviourals ( Gait, Tremors, Twitches,Convulsions Bizarre/Abnormal/Stereotypic behavior, Salivation ,Pilo-erection ,Exophthalmia Lachrymation,
Hyper/Hypothermia Skin color Respiration Palpebral closure Urination Defecation, Transfer arousal & Tail elevation.

IMMUNOLOGY: No

- Time schedule for examinations:

- How many animals:

- Dose groups that were examined:

- Parameters checked in table [No.?] were examined.

Oestrous cyclicity (parental animals):

Vaginal smears:

For 15 days before pairing using cotton swabs (Reproductive phase females only).

Wet smears:

Using pipette lavage during the following phases:
- For 14 days before treatment (all females including spares); animals that failed to exhibit 4-5 day cycles were not allocated to the Reproductive phase of the study.
- After pairing until mating (Reproductive phase females only).
- For four days before scheduled termination (all females except for premature decedents).
- Females showed no evidence of mating: following completion of pairing period female was separated from the male and vaginal smearing continued for up to five days or until the first estrous smear was seen. If a female shows an estrous smear during this period, she was killed and subject to macroscopic examination.

Sperm parameters (parental animals):

Parameters examined in F0 male parental generations:
testis weight, epididymis weight.

For the assessment of the testes, a detailed qualitative examination was made, taking into account the tubular stages of the spermatogenic cycle. The examination was conducted in order to identify treatment related effects such as missing germ cell layers or types, retained spermatids, multinucleate or apoptotic germ cells and sloughing of spermatogenic cells in the lumen. Any cell- or stage-specificity of testicular findings was noted.

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
clinical signs, litter size, sex ratio, survival indices, ano-genital distance, body weight change, presence of nipple/areolae in male offspring , macropathology/ abnormalities.

GROSS EXAMINATION OF DEAD PUPS:
no

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY: no

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY: no

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals - Day 45
- Maternal animals: All surviving animals - Day 14 (lactating)

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

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in a table were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring were sacrificed at 13 days of age.
- These animals were subjected to postmortem examinations (macroscopic examination) as follows:

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

Statistics:

Data were analyzed using the decision tree from the ProvantisTM Tables and Statistics Module.
The homogeneity of variance from mean values was analyzed using Bartlett’s test. Intergroup variances were assessed using suitable ANOVA, or if required, ANCOVA with appropriate covariates. Any transformed data were analyzed to find the lowest treatment level that showed a significant effect using the Williams Test for parametric data or the Shirley Test for non-parametric data. None dose response with data showing non- homogeneity of means, a stepwise Dunnett’s (parametric) or Steel (non-parametric) test to determine significant difference from the control group. Where the data were unsuitable for these analyses, pair-wise tests was performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).
Data not analyzed by the Provantis data capture system, R Environment for Statistical Computing was used. Initially, the distribution of the data was assessed by the Shapiro-Wilk normality test, followed by assessment of the homogeneity of the data using Bartlett’s test. Where considered appropriate, parametric analysis of the data was applied incorporating analysis of variance (ANOVA), which if significant, was followed by pair-wise comparisons using Dunnett’s test. Where parametric analysis of the data was considered to be unsuitable, non-parametric analysis of the data was performed incorporating the Kruskal- Wallis test which if significant was followed by the Mann-Whitney "U" test. Dose response relationships were also investigated by linear regression. Where the data were unsuitable for these analyses then pair-wise tests were performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).
Probability values (p):
p<0.01 **
p<0.05 *
p>0.05 (not significant)

Reproductive indices:

Percent mating, conception rate, fertility and gestation index determined.

Offspring viability indices:

Post-implantation survival index, viability index, lactation index and sex ratio determined.

Clinical signs:

effects observed, treatment-related

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

There was one unscheduled adult death (Female 94) on day 50, occurring at a dosage of 750 mg/kg bw/day. The animal had shown hunched posture, pallor of the extremities, apparent hypothermia and piloerection on the previous day. This female had littered but had shown total litter on Day 1 post partum. Necropsy examination revealed enlarged liver, spleen and right adrenal, a pale area on the liver and thin appearance of the non-glandular region of the stomach and raised limiting ridge. Additionally, a pale mass was observed in the right ventricle of the heart during tissue processing. At histopathology examination, the main changes observed were abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies. It is considered likely that sepsis, as a result of complications of pregnancy, was the cause of death. This isolated atypical death was, therefore, considered to be incidental and unrelated to treatment.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

There was no effect of treatment on food consumption of males throughout the study or of females during the pre-pairing or gestation phases at 100, 350 or 750 mg/kg bw/day.
At all dosages, food consumption was lower than control from Day 4 of lactation and whilst group mean values showed no dosage relationship, the difference from control was most notable at 750 mg/kg bw/day during the second week of lactation. The observed differences in food intake for these females was considered to reflect lower demand due to smaller litter size for the treated females.

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

For males at 750 mg/kg bw/day, mean values for mean corpuscular hemoglobin and mean corpuscular volume were statistically significantly lower than control. For mean corpuscular volume, 3/5 individual values for these treated animals were below the historical control range but all individual values for mean corpuscular hemoglobin were within the historical control range. These findings, in isolation, were considered most likely to be incidental and, in the absence of any supporting histopathology, were insufficient to be regarded as an adverse effect.
For males at 350 or 750 mg/kg bw/day, mean reticulocyte counts were statistically significantly higher than control but values showed no dosage relationship. All individual values at 350 mg/kg bw/day were within the historical control range but 2/5 values at 750 mg/kg bw/day were below this historical range. However, all individual values for control animals were also below the historical range and it is considered that the observed differences in mean values were due to atypical low values for the control group rather than any effect of treatment.
For males at 350 or 750 mg/kg bw/day, mean total leucocyte count were statistically significantly higher than control principally due to statistically significant higher mean number of lymphocytes. For total leucocyte count, 2/5 values at 350 mg/kg bw/day and 3/5 values at 750 mg/kg bw/day exceeded the historical control range and for lymphocytes count, 2/5 values at each dosage exceeded the historical control range. In the absence of any supporting histopathology, this finding was considered to be of little toxicological significance and insufficient to represent an adverse effect.
For females at 750 mg/kg bw/day, the mean value for mean corpuscular hemoglobin was statistically significantly lower than control. All individual values for these treated females were within the historical control range whist 2/5 control exceeded this historical range. This finding, in the absence of any supporting histopathology, was therefore considered to be incidental and unrelated to treatment.
For females at 350 or 750 mg/kg bw/day, mean total leucocyte count were statistically significantly higher than control principally due to statistically significant higher mean number of lymphocytes. All individual values for these treated females were within the historical control range and this finding, in the absence of any supporting histopathology, was considered to be of little toxicological significance and insufficient to represent an adverse effect.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

The mean levels of thyroxine (T4) in adult males were statistically significant higher then control at 100, 350 and 750 mg/kg bw/day, although mean values showed no dosage-relationship at the lower dosage levels. These differences from control for T4 levels in males occurred in the absence of any effect on organ weight or evidence of histopathological change for the male thyroid and, therefore, this finding was considered to be incidental and unrelated to treatment

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Isolated occasions of noisy respiration were observed for one male at 100 mg/kg bw/day, one female at 350 mg/kg bw/day and one male and one female at 750 mg/kg bw/day during these assessments. These findings were consistent with the clinical signs observed during routine pot-dosing observations throughout the study and were considered not to indicate any systemic effect of treatment.
At 350 mg/kg bw/day, one female showed piloerection during the behavioral assessment for the third week of gestation but this finding, in isolation, was considered to be incidental and of no toxicological significance.
Grip strength and motor activity assessments did not indicate any adverse effect of treatment for either sex at 100, 350 or 750 mg/kg bw/day.
For females at all dosages, mean hind limb grip strength was statistically significantly lower than control during trial two, however there was no dosage relationship and no other statistically significant differences were apparent during the other trial of grip strength. This finding was therefore considered to be incidental and unrelated to treatment.
For females at 750 mg/kg bw/day, lower motor activity, compared to control was apparent during at the last 20% of the testing period. Motor activity followed the expected pattern of behavior and there was no similar decrease apparent for males at this dosage. There were no histopathological findings apparent for the brain or nervous system and no other findings apparent during the study to indicate any neurological effect. In isolation, this finding was considered to be incidental and unrelated to treatment

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Histopathological examinations did not indicate any adverse effect of treatment at 100, 350 and 750 mg/kg bw/day.
It was noted that follicular hypertrophy was present in the thyroid glands of 1/12, 9/12 and 7/11 females at 100, 350 and 750 mg/kg bw/day respectively, although no histopathological changes in the thyroid were apparent for males. The follicular hypertrophy for females appeared to correlate with increased thyroid weights compared to control, however neither the incidence of the microscopic finding nor the differences in mean thyroid weights showed any dosage relationship. Whilst this finding could possibly represent a direct stand-alone change in the thyroid gland, this is considered to be unlikely when occurring only in females. Thyroid activity is increased in females which are pregnant/lactating and, in view of the lack of a true dose-response, this findings was considered to reflect an uneven incidence of normal variability for these female animals within the study.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

Mating performance was unaffected, the number of females that achieved pregnancy and gestation length were unaffected by treatment at 100, 350 or 750 mg/kg bw/day.

At 750 mg/kg bw/day, the mean number of implantations was lower than control leading to lower litter size from birth until termination on Day 13. Although one female total litter loss post partum at this dosage, offspring survival for remaining litters was good and there was considered to be no effect of maternal treatment on post-implantation loss or post-natal survival.

At 100 and 300 mg/kg bw/day, the mean number of implantations was also lower than control but, to a lesser extent, than observed at 750 mg/kg bw/day. This resulted in slightly lower litter size from birth although post-implantation loss and post-natal survival appeared unaffected by treatment.

Key result

Dose descriptor:

NOAEL

Effect level:

350 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

reproductive performance

Remarks on result:

other: Lower numbers of implantations

Key result

Critical effects observed:

no

Lowest effective dose / conc.:

750 mg/kg bw/day (nominal)

System:

other: No effects observed

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

At 750 mg/kg bw/day, there was a higher incidence of small offspring consistent with the lower offspring growth at this dosage, but otherwise, offspring clinical signs appeared unaffected by maternal treatment at 100, 350 or 750 mg/kg bw/day.

Dermal irritation (if dermal study):

not examined

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

At 750 mg/kg bw/day, offspring body weight gain was slightly lower than control, despite the lower litter size at this dosage, leading to lower mean offspring body weight at Day 13 of age. Litter weight at 750 mg/kg bw/day, was lower than control throughout, initially reflecting the lower litter size and additionally the lower weight gain as lactation progressed.
At 100 or 350 mg/kg bw/day, mean offspring body weight on Day 1 and subsequent mean offspring body weight gain to Day 13 were unaffected by maternal treatment. Litter weights were lower than control throughout lactation but this reflected the slightly lower litter size at these dosages compared to control.
At 750 mg/kg bw/day, there was a higher incidence of small offspring consistent with the lower offspring growth at this dosage, but otherwise, offspring clinical signs appeared unaffected by maternal treatment at 100, 350 or 750 mg/kg bw/day

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

It was noted that follicular hypertrophy was present in the thyroid glands of 1/12, 9/12 and 7/11 females at 100, 350 and 750 mg/kg bw/day respectively, although no histopathological changes in the thyroid were apparent for males. The follicular hypertrophy for females appeared to correlate with increased thyroid weights compared to control, however neither the incidence of the microscopic finding nor the differences in mean thyroid weights showed any dosage relationship. Whilst this finding could possibly represent a direct stand-alone change in the thyroid gland, this is considered to be unlikely when occurring only in females. Thyroid activity is increased in females which are pregnant/lactating and, in view of the lack a true dose-response, this findings was considered to reflect an uneven incidence of normal variability for these female animals within the study.

Other effects:

not examined

Behaviour (functional findings):

no effects observed

Developmental immunotoxicity:

not examined

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

350 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Lower numbers of implantations were apparent for females at 750 mg/kg bw/day as well as lower offspring growth

Remarks on result:

other: Effects observed in number of implantation and offspring growth

Key result

Critical effects observed:

no

Lowest effective dose / conc.:

750 mg/kg bw/day (nominal)

System:

other: No effects or abnormalities observed

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

750 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to other toxic effects:

reproductive effects in the absence of other toxic effects

Dose response relationship:

no

Relevant for humans:

not specified

Table 3. Summary of Reproductive Index

Group	Mating Index (%)	Group/ sex	Number of females showing evidence of regular estrous cycling	Number of females showing di-estrus	Pregnancy Index (%)	Female with living offspring	Parturition Index (%)
1	100	1(F)	12	12	100	12	100
2	100	2(F)	12	12	100	12	100
3	100	3(F)	12	12	100	12	100
4	100	4(F)	12	11#	100	12@	100@

# One female found dead on Day 50 (Day 7 of lactation) prior to scheduled necropsy

@ = Includes one female which had a total litter loss

Table 4. Group Mean Litter Size

Group	Number of ImplantationSites	Total Number of Offspring Born	Number of Live Offspring
			Day 1	Day 4 BC	Day 4 AC	Day 7	Day 13
1	12.5	11.9	11.9	11.9	10.0	9.9	9.9
2	11.0	9.8	9.8	9.8	8.4	8.4	8.3
3	10.3	10.0	10.0	9.8	8.4	8.4	8.4
4	9.5	8.6	8.6	8.5	7.7	7.7	7.6

Table 5. Group Mean Litter Values for Offspring Weights and Litter Weight

Group	Offspring Weight (g)										Litter Weight (g)					Offspring Body Weight Change (g)								Cumulative Offspring Body Weight Change (g)
	Day 1		Day 4 BC		Day 4 AC		Day 7		Day 13		Day 1	Day 4 BC	Day 4 AC	Day7	Day 13	Day 1-4 BC		Day 1-4 AC		Day 4-7 AC		Day 7-13		Day 1-7		Day 1-13
	M	F	M	F	M	F	M	F	M	F						M	F	M	F	M	F	M	F	M	F	M	F
1	5.97	5.67	8.86	8.43	8.87	8.43	13.91	13.36	26.67	25.83	25.83	68.63	101.58	132.55	255.0	2.90	2.77	2.90	2.77	5.04	4.93	12.76	12.47	7.94	7.70	20.70	20.16
2	6.28	6.01	9.06	8.89	9.07	8.91	13.91	13.92	26.81	26.81	25.83	58.51	83.59	112.58	214.77	2.78	2.88	2.79	2.90	2.79	5.00	12.90	12.98	7.63	7.90	20.53	20.88
3	6.11	5.82	8.69	8.33	8.70	8.34	13.17	12.57	25.56	24.61	25.83	58.68	81.00	107.21	208.71	2.58	2.52	2.58	2.52	2.58	4.23	12.39	12.04	7.05	6.75	19.44	18.79
4	6.18	5.72	8.32	7.79	8.32	7.81	11.96	11.24	22.15	21.24	25.83	49.49	65.55	88.06	163.51	2.13	2.06	2.13	2.09	2.13	3.46	10.19	10.01	5.78	5.51	15.97	15.52

Table 6. Group Mean Litter Values for Implantation Losses, Survival Indices and Offspring Sex Ratio

Group	Post implantation loss (%)	Live birth index (%)	Viability index 1 (%)	Viability index 2 (%)	Sex ratio (% males) Post partum day
					At birth	1	4BC	4AC	7
1	4.7	100.0	100.0	99.1	45.6	45.6	45.6	51.4	52.0
2	12.0	100.0	100.0	98.5	41.0	41.0	41.0	46.1	46.1
3	1.9	100.0	97.9	100.0	51.4	51.4	51.7	57.0	57.0
4	8.4	99.2	98.9	98.9	40.4	40.8	44.1	44.1	44.1

Table. 8. Group Mean Litter Values for Offspring Ano-Genital Distance.

Group	Male				Female
	Ano-genital Distance (mm)	Body weight on Day 1 (g)	Normalised Ano-genital Distance (mm)	% Male Offspring Showing Visible Nipples	Ano-genital Distance (mm)	Body weight on Day 1 (g)	Normalised Ano-genital Distance (mm)
1	3.18	5.97	1.76	0.0	1.50	5.67	0.84
2	3.36	6.28	1.82	0.0	1.56	6.01	0.86
3	3.30	6.11	1.81	0.0	1.65	5.82	0.92
4	3.56	6.18	1.94	0.0	1.75	5.72	0.98

Table 9. Group Mean Blood Chemical and Haematology Values

Blood chemistry parameters	Male				Female
	Group 1	Group 2	Group 3	Group 4	Group 1	Group 2	Group 3	Group 4
P mmol/l	2.00	2.38*	2.48*	2.52*	1.74	1.60	1.46	1.44
ASAT IU/l	99.6	84.0	83.8	90.0	106.2	95.4	135.4	101.4
ALAT (IU/l)	54.6	53.0	45.8	50.8	104.0	82.6	121.4	125.4
AP (IU/l)	160.4	157.0	154.6	200.8	199.4	184.2	245.2	258.4
Creat mg/dl	0.670	0.654	0.610	0.638	0.662	0.584	0.536*	0.538**
Chol mg/dl	78.4	86.2	99.6*	135.0**	113.8	142.2	212.2**	200.0**
Bili mg/dl	0.060	0.062	0.104**	0.134**	0.076	0.088	0.112*	0.120**
Bile acid μmol/l	17.32	23.50	16.32	48.56*	23.30	28.32	53.92	50.22
Urea mg/dl	44.2	41.0	37.8	39.0	58.2	52.4	55.8	52.6
Glucose mg/dl	143.6	129.4	126.0	123.0	128.8	124.4	117.8	128.4
Tot. Prot. g/dl	6.012	6.352	6.330	6.588	5.672	5.408	5.010**	4.772**
Abumin g/dl	3.30	3.48	3.52	3.60	3.22	3.08	2.68**	2.52**
A/G Ratio	1.204	1.214	1.264	1.202	1.324	1.336	1.136	1.132
Na+mmol/l	148.2	147.8	148.4	151.6	145.4	146.4	144.2	144.2
K+mmol/l	5.522	5.188	4.882	5.328	5.418	5.144	5.348	4.864
Cl-mmol/l	101.6	100.6	101.6	101.8	102.4	99.6	99.6	100.0
Ca++mmol/l	2.462	2.592	2.544	2.470	2.614	2.588	2.478	2.340**
Hematology parameters	Male				Female
	Group 1	Group 2	Group 3	Group 4	Group 1	Group 2	Group 3	Group 4
Hbg/dl	16.04	16.12	15.78	15.56	14.30	14.18	13.88	14.02
RBC 10^12/l	8.566	8.970	8.602	8.910	6.928	7.252	6.738	7.472
Hct %	45.02	45.20	44.90	44.24	40.40	40.36	39.36	40.66
MCH pg	18.70	18.00	18.38	17.50**	20.68	19.64	20.68	18.74*
MCV f1	52.38	50.36	52.16	49.70*	58.46	55.56	58.58	54.48
MCHC g/d1	35.62	35.72	35.18	35.18	35.40	35.22	35.12	34.32
WBC 10^9/l	7.12	7.56	9.18*	9.30*	4.78	5.50	6.34*	6.10*
Neut 10^9/l	1.170	1.330	1.368	1.122	1.510	1.908	2.278	1.936
Lymp 10^9/l	5.894	6.185	7.744*	8.106*	3.242	3.578	4.062*	4.166*
Mono 10^9/l	0.000n	0.000n	0.000n	0.014n	0.000n	0.000n	0.000n	0.000n
Eco 10^9/l	0.058	0.046	0.072	0.058	0.000n	0.014n	0.000n	0.000n
Bas 10^9/l	0.000n	0.000n	0.000n	0.000n	0.000n	0.000n	0.000n	0.000n
CT Seconds	9.84	912	9.06	9.84	8.58	8.74	8.82	8.78
PLT10^9/l	528.4	668.4**	692.8**	759.6**	598.0	613.0	592.2	591.6
APTTSeconds	16.26	14.56	16.22	13.34	15.22	14.42	15.90	15.06
Retics%	2.70	3.00	3.40*	3.36*	4.08	4.78	4.66	4.58

Table 10. Mean Serum T4 Concentrations (pg/mL)

Group	Adult Terminal Male	Males offspring on Day 13 of age	Females offspring on Day 13 of age
1	43800	39800	40200
2	52400*	41400	43200
3	54200**	39100	41800
4	57100**	33900	36700

Table 11. Group Mean Organ Weights with Corresponding Relative (% of Body Weight) Organ Weights.

Organ	Male				Female
	Group 1	Group 2	Group 3	Group 4	Group 1	Group 2	Group 3	Group 4
Terminal Bodyweight	402.6	399.5	419.1	410.0	307.8	303.1	297.9	290.0
Adrenals	0.07604	0.8212	0.08306	0.08738	0.08944	0.08984	0.08634	0.06886*
Relative weight	0.019	0.021	0.020	0.023	0.030	0.030	0.029	0.024*
Brain (Including Cerebrum,Cerebellum And Pons	2.03794	1.96792	2.11446	2.11988	1.89094	1.88286	1.85480	1.86090
Relative weight	0.503	0.503	0.523	0.545	0.631	0.634	0.617	0.629
Epididymides	1.57071	1.57443	1.57373	1.65603
Relative weight	0.392	0.397	0.379	0.406
Heart	1.20340	1.16954	1.05046	1.25526	1.26666	1.21634	1.24060	1.26134
Relative weight	0.297	0.304	0.260	0.319	0.418	0.409	0.413	0.423
Kidneys	2.53500	2.28878	2.63396	2.83520*	1.92546	1.86024	2.11782	1.96906
Relative weight	0.625	0.591	0.653	0.723*	0.639	0.626	0.702	0.662
Liver	14.7494	12.9958	16.7185*	18.9891**	14.9901	16.2430**	18.3088**	19.9560**
Relative weight	3.623	3.306	4.131*	4.807**	4.971	5.451**	6.043**	6.669**
Ovaries					0.08398	0.10168**	0.10708**	0.09728**
Relative weight					0.027	0.034**	0.036**	0.033**
Pituitary	0.01346	0.01462	0.01453	0.01428	0.01688	0.01684	0.01973	0.01516
Relative weight	0.003	0.004	0.003	0.003	0.005	0.006	0.007	0.005
Prostate	0.59454	0.65658	0.6887	0.74909*
Relative weight	0.149	0.164	0.166	0.184*
Seminal Vesicles (With Coagulaƒtion Gland)	1.83467	1.80241	2.13610*	2.10727*
Relative weight	0.457	0.453	0.515*	0.522*
Spleen	0.79592	0.84392	0.81226	0.64332	0.78504	0.79592	0.76730	0.62180
Relative weight	0.196	0.218	0.200	0.207	0.214	0.264	0.254	0.207
Testes	3.89569	3.88659	3.90728	3.99370
Relative weight	0.970	0.979	0.940	0.979
Thymus	0.44948	0.26398	0.43702	0.47466	0.26014	0.28096	0.27406	0.27402
Relative weight	0.111	0.068	0.108	0.119	0.087	0.095	0.091	0.091
Thyroid/Parathyroid	0.03972	0.04271	0.04116	0.04364	0.02671	0.03178	0.03821*	0.03509*
Relative weight	0.010	0.011	0.010	0.011	0.009	0.010	0.013*	0.012*
Uterus & Cervix (And Oviducts)					0.54190	0.57278	0.50861	0.59657
Relative weight					0.177	0.192	0.171	0.171

Conclusions:

Based on the results of this study the No Observed Adverse Effect Level (NOAEL) for systemic toxicity of α-phenyl-1H-benzimidazole-2-methanol to the adult animal was considered to be 750 mg/kg bw/day. Lower numbers of implantations were apparent for females at 750 mg/kg bw/day, therefore, the NOAEL for reproduction was considered to be 350 mg/kg bw/day.

Executive summary:

OECD 422 (2019) - In a combined repeat dose toxicity study with reproductive toxicity screening with Comet Assay (OECD 422), α-phenyl-1H-benzimidazole-2-methanol was administered by gavage to three groups, each of twelve male and twelve female Wistar Han™:RccHan™:WIST strain rats, for approximately six weeks for males and for approximately eight weeks for females (including a two week pre-pairing phase, pairing, gestation and early lactation for females), at dose levels of 100, 350 and 750 mg/kg bw/day.  A control group of twelve males and twelve females was dosed with vehicle alone (Polyethylene Glycol ) over the same period.  A further three males were dosed with N-Nitroso-N-methylurea (vehicle: distilled water) for two consecutive days to act as a positive control group for the comet assay 

Treatment at dosages of 100, 350 and 750 mg/kg bw/day was well tolerated with no adverse effect on body weight gain, food consumption, food conversion efficiency or water consumption for either sex throughout the study.  Food consumption was lower than control for treated females from Day 4 of lactation, with differences being most notable at 750 mg/kg bw/day during the second week of lactation; however, this was considered to reflect lower demand from the smaller litters for treated females, in comparison to their control counterparts, rather than any effect of treatment on the lactating females.  Post-dosing salivation was observed for the majority of animals at 750 mg/kg bw/day and this was also apparent for fewer animals and to a lesser extent at 350 mg/kg bw/day.  Increased post-dosing salivation is frequently observed when animals are dosed via the oral gavage route and is generally considered to reflect slight distaste or irritancy of the dosing formulations rather than any systemic effect of treatment.  Isolated occasions of noisy respiration were observed for all dose groups, including control, although the highest incidence was at 350 mg/kg bw/day and 750 mg/kg bw/day during the study.  The higher incidence of noisy respiration at 350 and 750 mg/kg bw/day may have been influenced by the increased post-dosing salivation observed at these higher dosages and this finding was considered to reflect slight distaste of the test item formulations and/or occasional difficulties in dosing isolated animals rather than any systemic effect of treatment.  

The only unscheduled adult death on the study occurred at 750 mg/kg bw/day, when a female was found dead on Day 50.  This animal had previously shown total litter loss post-partum and hunched posture, pallor of the extremities, apparent hypothermia and piloerection had been apparent on the day prior to death.  Necropsy revealed enlarged liver, spleen and right adrenal, a pale area on the liver and thin appearance of the non-glandular region of the stomach and raised limiting ridge and additionally, a pale mass was observed in the right ventricle of the heart during tissue processing.  Histopathology examination revealed abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies. It was considered that sepsis, as a result of complications of pregnancy, was the underlying cause of death and this isolated atypical occurrence was considered to be unrelated to treatment.  

Behavioral and function observations did not indicate any underlying neurological effect of treatment for either sex at 100, 350 or 750 mg/kg bw/day.  

There was no adverse effect of treatment on hematology or blood chemistry parameters at 100, 350 or 750 mg/kg bw/day.  Some intergroup differences in these parameters did attain statistical significance when compared to control but, in the absence of any supporting histopathological change, they were considered to be of little toxicological significance.

Necropsy of adults revealed a small number of liver findings (eg enlarged, mottled appearance, pale area) for females at 100 and 350 mg/kg bw/day and both sexes at 750 mg/kg bw/day and liver weights were statistically significantly higher than control for females at 100 mg/kg bw/day and both sexes at 350 and 750 mg/kg bw/day.  However, histopathological evaluation of the liver did not reveal any evidence of hepatic change and, while some adaptive alteration to liver metabolism may have occurred, these findings were considered not to represent an adverse effect of treatment.    

For females at 350 and 750 mg/kg bw/day, absolute and body weight-relative thyroid weights were statistically significantly higher than control, but mean values showed no dosage relationship. At both dosages, the majority of individual absolute and body weight-relative weights exceeded the respective historical control range, but again, these incidences showed no dosage response.  Follicular hypertrophy was present in the thyroid glands of 1/12, 9/12 and 7/11 females at 100, 350 and 750 mg/kg bw/day respectively but showed no true dose response and this follicular hypertrophy may be the underlying cause of the observed differences in the thyroid weights at 350 and 750 mg/kg bw/day.  No histopathological changes in the thyroid were apparent for males and, whilst a direct stand-alone change in the thyroid gland is possible, it is considered to be less likely when occurring only in females. Thyroid activity is increased in females which are pregnant/lactating and, in view of the lack a true dose-response, these findings was considered to reflect an uneven incidence of normal variability for these female animals within the study rather than an adverse effect of treatment.

All other statistically significant differences in organ weights observed during the study were not supporting by any accompanying histopathological change and were considered to be of little toxicological significance and not to represent an adverse effect.  

There was no effect of treatment on estrous cycles of females, mating performance or gestation length at 100, 350 or 750 mg/kg bw/day.  Although, there was no effect on fertility, as assessed by the number of females that achieved pregnancy at 100, 350 or 750 mg/kg bw/day, the number of implantations was lower than control at 750 mg/kg bw/day.  The number of implantation were also lower than control at 100 and 350 mg/kg bw/day but the differences were slight and probably reflect normal biological variation.  Histopathological evaluations of reproductive tissues at 750 mg/kg bw/day did not reveal any test item-related microscopic findings for the reproductive tissues and, in particular, there were no test item-related abnormalities in the integrity of the various cell types present within the different stages of the sperm cycle or for follicles and corpora lutea in the ovaries.  The lower number of implantations at 750 mg/kg bw/day is therefore unexplained, and while it this may also reflect normal variation, an effect of treatment cannot be discounted.

Subsequent post-implantation and post-natal survival of the offspring was unaffected by treatment at all dosages.  One female at 750 mg/kg bw/day did show total litter post partum but this was considered to reflect a decline in the clinical condition for this animal due to sepsis, as a result of complications of pregnancy, and therefore the high offspring mortality for this particular litter was considered to be unrelated to maternal treatment.  Mean offspring body weight on Day 1 of age was similar to control at all dosages but, body weight gain at 750 mg/kg bw/day was slightly lower than control, despite the lower litter size at this dosage, leading to lower mean offspring body weight at termination on Day 13 of age.  A number of small offspring were noted during clinical observations and at necropsy, consistent with this lower gain and litter weight at 750 mg/kg bw/day was lower than control throughout, initially reflecting the lower litter size and subsequent the lower litter size and weight gain. At 100 or 350 mg/kg bw/day, there was no effect of maternal treatment on offspring body weight gain to Day 13; litter weights were lower than control throughout, but this reflected the slightly lower litter size at both dosages.

Mean offspring ano-genital distance (actual and normalized) for males at 100 mg/kg bw/day and both sexes appeared longer than control at 100, 350 or 750 mg/kg bw/day; mean values for males at 100 and 350 mg/kg bw/day showed no dosage relationship.  For female offspring at 100 mg/kg bw/day, measured ano-genital distance was longer than control, but was similar to control when normalized for body weight.  All individual litter values for ano-genital distance, normalized for body weight, were within the historical control range at 100, 350 or 750 mg/kg bw/day.  As no normalized for body weight values for either sex were outside the normal historic range, an effect of treatment on ano-genital distance appeared unlikely and this finding was considered to be incidental and of no toxicological significance.  Evaluation of visible nipple count for male offspring on Day 13 post partum did not reveal any effect of maternal treatment at 100, 350 or 750 mg/kg bw/day.  

For the additional comet investigation, there were no significant increases in the percentage tail intensity or median percentage tail intensity for the jejunum, glandular stomach or liver at 100, 350 or 750 mg/kg bw/day and the test item was, therefore, considered to not induce DNA damage in these tissues under the conditions of the test.

The mean levels of thyroxine (T4) in adult males were statistically significant higher then control at 100, 350 and 750 mg/kg bw/day, although mean values showed no dosage-relationship at the lower dosage levels.  These differences from control for T4 levels in males occurred in the absence of any effect on organ weight or evidence of histopathological change for the male thyroid and, therefore, this finding was considered to be incidental and unrelated to treatment.

Under the condition of this study, the No Observed Adverse Effect Level (NOAEL) for systemic toxicity of α-phenyl-1H-benzimidazole-2-methanol to the adult animal was considered to be 750 mg/kg bw/day. Lower numbers of implantations were apparent for females at 750 mg/kg bw/day and as the etiology of this finding was unknown, the NOAEL for reproduction was considered to be 350 mg/kg bw/day.  

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

350 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The endpoint is concluded based on a single key study with a Klimisch rating of 1. The database for this endpoint met all relevant data requirements under REACH for the respective tonnage band.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

OECD 422 (2019) - In a combined repeat dose toxicity study with reproductive toxicity screening with Comet Assay (OECD 422), α-phenyl-1H-benzimidazole-2-methanol was administered by gavage to three groups, each of twelve male and twelve female Wistar Han™:RccHan™:WIST strain rats, for approximately six weeks for males and for approximately eight weeks for females (including a two week pre-pairing phase, pairing, gestation and early lactation for females), at dose levels of 100, 350 and 750 mg/kg bw/day.  A control group of twelve males and twelve females was dosed with vehicle alone (Polyethylene Glycol ) over the same period.  A further three males were dosed with N-Nitroso-N-methylurea (vehicle: distilled water) for two consecutive days to act as a positive control group for the comet assay.

At 750 mg/kg bw/day, Female 94 was found dead on Day 50 of the study, after having shown hunched posture, pallor of the extremities, apparent hypothermia and piloerection on Day 49.  Histopathology examination revealed abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies.  It is considered likely that sepsis, as a result of complications of pregnancy, was the underlying reason for mortality and this isolated atypical occurrence was considered to be incidental and unrelated to treatment.

There were no clinical signs observed that indicated any systemic effect of treatment for either sex at 100, 300 or 750 mg/kg bw/day.

Behavioral assessments were unaffected by treatment at 100, 350 and 750 mg/kg bw/day. Functional performance tests were unaffected by treatment at 100, 350 and 750 mg/kg bw/day.

Sensory reactivity assessments were unaffected by treatment at 100, 350 and 750 mg/kg bw/day.

There was no effect of treatment on body weight gain throughout the study for either sex, including for females during gestation and lactation phases, at 100, 350 or 750 mg/kg bw/day.

There was no effect of treatment on food consumption of males throughout the study or of females during the pre-pairing or gestation phases at 100, 350 or 750 mg/kg bw/day.  At all dosages, food consumption was lower than control from Day 4 of lactation and whilst group mean values showed no dosage relationship, the difference from control was most notable at 750 mg/kg bw/day during the second week of lactation.  The observed differences in food intake for these females was considered to reflect lower demand due to smaller litter size for the treated females.

There was no effect of treatment on food conversion efficiency of either sex during the pre-pairing phase of the study or for males during the post-pairing phase at 100, 350 or 750 mg/kg bw/day.  Visual inspection of water bottles throughout the study did not indicate any effect of treatment for either sex at 100, 300 or 750 mg/kg bw/day. There was no effect of treatment on estrous cycles of females and matting performance were unaffected with all female achieving pregnancy at 100, 350 or 750 mg/kg bw/day. Gestation length was unaffected by treatment at 100, 350 or 750 mg/kg bw/day.

At 750 mg/kg bw/day, the mean number of implantations was lower than control leading to lower litter size from birth, however, there was no effect of maternal treatment on post-implantation loss or post-natal survival. At 100 and 300 mg/kg bw/day, implantation count was lower than control but, to a lesser extent, than observed at 750 mg/kg bw/day, and resulted in slightly lower litter size from birth, although post-implantation loss and post-natal survival were unaffected by treatment. Sex ratio for the offspring was unaffected by maternal treatment at 100, 350 or 750 mg/kg bw/day. At 750 mg/kg bw/day, offspring body weight gain was slightly lower than control, despite the lower litter size at this dosage, leading to lower mean offspring body weight at Day 13 of age.  Litter weight at 750 mg/kg bw/day, was lower than control throughout, initially reflecting the lower litter size and additionally the lower weight gain as lactation progressed.   At 100 or 350 mg/kg bw/day, mean offspring body weight on Day 1 and subsequent mean offspring body weight gain to Day 13 were unaffected by maternal treatment.  Litter weights were lower than control throughout lactation but this reflected the slightly lower litter size at these dosages compared to control. At 750 mg/kg bw/day, there was a higher incidence of small offspring consistent with the lower offspring growth at this dosage, but otherwise, offspring clinical signs appeared unaffected by maternal treatment at all doses.  Mean ano-genital distance for offspring (both sexes) generally appeared longer than control at 100, 350 or 750 mg/kg bw/day, but all normalized for body weight values, for either sex,  were within the normal historic range and this finding was considered to be incidental and of no toxicological significance.   Visible nipple count for male offspring on Day 13 post partum was unaffected by maternal treatment at all treatment dose.

There was no adverse effect of treatment on blood chemistry and hematological parameters at all tested dose.The mean levels of thyroxine (T4) in adult males were statistically significant higher than control at all treatment groups, this effect was not observed in offspring.

At 750 mg/kg bw/day, there was a higher incidence of small offspring at necropsy, consistent with the lower offspring growth at this dosage, but otherwise, offspring necropsy findings appeared unaffected by maternal treatment. Necropsy findings did not indicate any adverse effect of treatment.

There was no adverse effect of treatment on organ weights and histopathology did not reveal any evidence of adverse effects at treatment dosage. It was noted that absolute and body weight-relative thyroid weights were statistically significantly higher than control for females at 350 and 750 mg/kg bw/day.  This increase in thyroid weights appeared to reflect follicular hypertrophy in the thyroid of some females at these dosages, however, neither the incidence of this microscopic finding nor the differences in mean thyroid weights showed any dosage relationship and this finding was considered not to represent an adverse effect of treatment.

Comet assay investigations during the study did not show any treatment induced DNA damage in the jejunum, glandular stomach or liver under the conditions of the test at 100, 350 and 750 mg/kg bw/day. The No Observed Adverse Effect Level (NOAEL) for systemic toxicity for the adult animal was considered to be 750 mg/kg bw/day. Lower numbers of implantations were apparent for females at 750 mg/kg bw/day, therefore, the NOAEL for reproduction was considered to be 350 mg/kg bw/day.

Effects on developmental toxicity

Description of key information

NOAEL (Development) = 350 mg/kg bw/d; OECD 422; S. Fulcher. (2019)

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 June 2018 to TBC

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 422 (Combined Repeat Dose Toxicity Study with the Reproduction/Developmental Toxicity Test)

Version / remarks:

2016

Deviations:

yes

Remarks:

Deviation from target value for relative humidity (RH) from 50 ± 20% to 76%, but the study was unaffected.

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EC) No 440/2008 of 30 May 2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).

Version / remarks:

2008

Deviations:

yes

Remarks:

Deviation from target value for relative humidity (RH) from 50 ± 20% to 76%, but the study was unaffected.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Wistar HanTM:RccHanTM:WIST strain

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Envigo RMS (UK) Limited, Blackthorn, Bicester, Oxon, UK
- Females (if applicable) nulliparous and non-pregnant: yes

- Date of birth: Not specified

- Age at study initiation: male 11 weeks and female 12 weeks

- Weight at study initiation: Male 284 to 354g and female 193 to 225g
- If immature animals, whether or not supplied with dam or foster dam and date of weaning: N/A

- Fasting period before study: No

- Housing: Groups of three in solid floor polypropylene cages with stainless steel mesh lids and softwood flake bedding (Datesand Ltd., Cheshire, UK). During the pairing phase, animals were transferred to polypropylene grid floor cages suspended over trays lined with absorbent paper on a one male: one female basis within each dose group. Following evidence of successful mating, the males were returned to their original cages. Mated females were housed individually during gestation and lactation in solid floor polypropylene cages with stainless steel mesh lids and softwood flakes.
- Diet (e.g. ad libitum): Free access to food, a pelleted diet (Rodent 2018C Teklad Global Certified Diet, Envigo RMS (UK) Limited, Oxon, UK.) was used.
- Water (e.g. ad libitum): Free access to mains drinking water supplied from polycarbonate bottles attached to the cage.
- Acclimation period: 20 days



DETAILS OF FOOD AND WATER QUALITY


ENVIRONMENTAL CONDITIONS

- Temperature (°C):22 ± 3 °C
- Humidity (%): 50 ± 20%
- Air changes (per hr): The rate of air exchange was at least fifteen air changes per hour.
- Photoperiod (hrs dark / hrs light): Low intensity fluorescent lighting was controlled to give twelve hours continuous light and twelve hours darkness

IN-LIFE DATES: From: To: Not indicated

Route of administration:

oral: gavage

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
 The test item was prepared at the appropriate concentrations in Polyethylene glycol 400 (PEG 400). Formulations were therefore prepared in batches of up to two weeks and made up to three days in advance of first use and stored at approximately 4°C in the dark.

 VEHICLE 
 - Justification for use and choice of vehicle (if other than water): The substance was miscible in Polyethylene glycol 400 grade
- Concentration in vehicle: 99-104% of the nominal concentration
- Amount of vehicle (if gavage): Dose Volume of 6mL/kg
- Lot/batch no. (if required): 1729820

- Purity: Not stated

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytical procedure was successfully validated with respect to specificity of chromatographic analysis, linearity of detector response, method accuracy and precision.

The homogeneity and stability was confirmed for the test item in PEG 400 formulations at nominal concentration of 3.75 mg/mL and 250 mg/mL when stored refrigerated for 18 days.

The mean concentrations of the test item formulations analysed for the study were within +/- 10% of nominal concentrations, confirming accurate formulation.

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: up to 2 weeks
- Proof of pregnancy: vaginal plug and sperm in vaginal smear referred to as Day 0 of pregnancy.
- Further matings after unsuccessful attempts: no
- After successful mating each pregnant female was caged (how): housed individually in a cages comprised of a polycarbonate body with a stainless steel mesh lid.
- Any other deviations from standard protocol:no

Duration of treatment / exposure:

6 - 8 weeks

Frequency of treatment:

Daily

Duration of test:

6-8 weeks

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

1.Control

Dose / conc.:

100 mg/kg bw/day (nominal)

Remarks:

2.Low

Dose / conc.:

350 mg/kg bw/day (nominal)

Remarks:

3. Intermediate

Dose / conc.:

750 mg/kg bw/day (nominal)

Remarks:

4.High

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Details on study design:

i. Males and females were housed for a suitable acclimatization period which allowed at least two weeks of pre-treatment vaginal smears to be performed for females enabling the exclusion of females not showing appropriate estrous cycling.
ii. Groups of twelve male and twelve female animals were treated daily at the appropriate dose level throughout the study (except for females during parturition where applicable). The first day of dosing was designated as Day 1 of the study.
iii. Prior to the start of treatment and once weekly thereafter, all animals were observed for signs of functional/behavioral toxicity.
iv. On Day 15, animals were paired on a 1 male: 1 female basis within each dose group for a maximum of fourteen days.
v. Following evidence of mating (designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages.
vi. On completion of the pairing phase, five selected males per dose group were evaluated for functional/sensory responses to various stimuli during Week 6.
vii. Pregnant females were allowed to give birth and maintain their offspring until Day 13 post partum. Litter size, offspring weight and sex, ano-genital distance, visible nipple counts (male offspring) and clinical signs were also recorded during this period.
viii. On Day 4 post partum, where possible, blood sampling was performed on two randomly allocated offspring from each litter in order to obtain serum samples.
ix. At Day 12 post partum, five selected females per dose group were evaluated for functional/sensory responses to various stimuli
x.Blood samples were taken from five males from each dose group for hematological and blood chemical assessments on Day 43. The male dose groups were killed and examined macroscopically on Day 44 or 45.
xi. On Day 13 post partum, where possible, blood sampling to produce serum samples for assessment of thyroid hormones was performed on two randomly selected offspring (one male and one female) per litter. Where possible, a further two randomly selected offspring (one male and one female) per litter were sampled to produce surther serum samples as a contingency against the need to measure TSH. Thyroid/parathyroid samples were also retained from one male and one female from each litter where litter sizes allowed. All surviving offspring were killed and examined externally; where external observations were detected an internal necropsy was performed.
xii. Blood samples were taken from five randomly selected females from each dose group for hematological and blood chemical assessment on Day 13 post partum. All surviving females were sacrificed on Day 14 post partum and examined macroscopically. A vaginal smear was also performed for all females in the morning of the day of necropsy. In addition, blood samples to produce both serum and plasma were taken from all adult animals at termination. Blood samples from all adult males and Day 13 offspring were analyzed for Thyroxine (T4).
xiii. Selected tissues were taken from five males from Groups 2 to 4 and all 3 positive control males (Group 5) for subsequent processed as part of the comet assay assessment.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Throughout the study
- Cage side observations checked in table [No.?] were included. Yes


DETAILED CLINICAL OBSERVATIONS: Yes

- Time schedule:
Group 1 - 4: 30 mins post dosing & an hour after dosing. Comet male, immediately before dosing and up to 30 mins post dosing. 
Group 5: Daily but formal recording began on day 44 when observations were made immediately before dosing and up to 30 mins post dosing and day 45 only immediately before dosing and up to 30 mins post dosing.

BODY WEIGHT: Yes 
- Time schedule for examinations:
Groups 1 to 4: Individual body weights were recorded for males on Day -5 (Day of allocation), Day 1 and then weekly until termination. Individual body weights were also recorded at terminal kill.
For females, individual body weights were recorded on Day -5 (Day of allocation), Day 1 and then weekly until pairing. During the pairing phase, females were weighed daily until mating was confirmed. Mated females were weighed on Day 0, 7, 14 and 20 post coitum and body weights for females which give birth were recorded on Days 1, 4, 7 and 14 post partum.
Group 5:
During the pre-treatment period, individual body weights will be recorded on a weekly basis to coincide with the scheduled weighing of Group 1 to 4 animals. Individual body weights were recorded on Day 44 (prior to start of dosing) and were also recorded on the day of termination (Day 45).
Individual body weights were recorded on Day 1 (prior to dosing) and then weekly for males until termination and weekly for females until pairing. During pairing phase females were weighed daily until mating was confirmed. Body weights were then recorded for females on Days 0, 7, 14 and 20 post coitum, and on Days 1, 4, 7 and 14 post partum. Body weights were also recorded at terminal kill.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule for examinations:
Group 1 to 4: During the pre-pairing period, weekly food consumption was recorded for each cage of adults. This was continued for males after the mating phase. For females showing evidence of mating, food consumption was recorded for the periods covering post coitum Days 0-7, 7-14 and 14-20. For females during lactation, food consumption was recorded for the periods covering post partum Days 1-4, 4-7 and 7-14.
Group 5: No formal measurement of food consumption was performed for these animals.

FOOD EFFICIENCY: Yes
- Time schedule for examinations:
Group 1 to 4: Food efficiency (the ratio of body weight change/dietary intake) was calculated retrospectively for males throughout the study period (with the exception of the mating phase) and for females during the pre-pairing phase. Due to offspring growth and milk production, food efficiency could not be accurately calculated during gestation and lactation.


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes 
- Time schedule for examinations: Daily



OPHTHALMOSCOPIC EXAMINATION: No

- Time schedule for examinations:

- Dose groups that were examined:



HAEMATOLOGY: Yes 

- Time schedule for collection of blood: Male day 43 & female Day 13 Post partum

- Anaesthetic used for blood collection: No

- Animals fasted: No
- How many animals: Five male and five female from groups 1 -4

- Parameters checked in table [No.?] were examined. Yes



CLINICAL CHEMISTRY: Yes

- Time schedule for collection of blood:Male day 43 & female Day 13 Post partum
- Animals fasted: No

- How many animals:Five male and five female from groups 1 -4
- Parameters checked in table [No.?] were examined. Yes



URINALYSIS: No

- Time schedule for collection of urine:

- Metabolism cages used for collection of urine: 

- Animals fasted: 

- Parameters checked in table [No.?] were examined.



NEUROBEHAVIOURAL EXAMINATION: Yes 

- Time schedule for examinations: Prior to the start of treatment and at approximately weekly intervals thereafter, all animals were observed for signs of functional/behavioral toxicity. These observations were performed on mated females on Days 4, 11 and 18 post coitum and for littering females on Days 4 and 12 post partum. Functional performance tests were also performed on five selected males and females from each dose level, prior to termination, together with an assessment of sensory reactivity to various stimuli.

- Dose groups that were examined:Groups 1 - 4
- Battery of functions tested: sensory activity / grip strength / motor activity /: All
other: Behaviourals ( Gait, Tremors, Twitches,Convulsions Bizarre/Abnormal/Stereotypic behavior, Salivation ,Pilo-erection ,Exophthalmia Lachrymation,
Hyper/Hypothermia Skin color Respiration Palpebral closure Urination Defecation, Transfer arousal & Tail elevation.

IMMUNOLOGY: No

- Time schedule for examinations:

- How many animals:

- Dose groups that were examined:

- Parameters checked in table [No.?] were examined.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: No
- Number of late resorptions: No
- Other:

Fetal examinations:

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

Statistics:

Data were analyzed using the decision tree from the ProvantisTM Tables and Statistics Module.
The homogeneity of variance from mean values was analyzed using Bartlett’s test. Intergroup variances were assessed using suitable ANOVA, or if required, ANCOVA with appropriate covariates. Any transformed data were analyzed to find the lowest treatment level that showed a significant effect using the Williams Test for parametric data or the Shirley Test for non-parametric data. None dose response with data showing non- homogeneity of means, a stepwise Dunnett’s (parametric) or Steel (non-parametric) test to determine significant difference from the control group. Where the data were unsuitable for these analyses, pair-wise tests was performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).
Data not analyzed by the Provantis data capture system, R Environment for Statistical Computing was used. Initially, the distribution of the data was assessed by the Shapiro-Wilk normality test, followed by assessment of the homogeneity of the data using Bartlett’s test. Where considered appropriate, parametric analysis of the data was applied incorporating analysis of variance (ANOVA), which if significant, was followed by pair-wise comparisons using Dunnett’s test. Where parametric analysis of the data was considered to be unsuitable, non-parametric analysis of the data was performed incorporating the Kruskal- Wallis test which if significant was followed by the Mann-Whitney "U" test. Dose response relationships were also investigated by linear regression. Where the data were unsuitable for these analyses then pair-wise tests were performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).
Probability values (p):
p<0.01 **
p<0.05 *
p>0.05 (not significant)

Indices:

Offspring viability indices including; viability index, lactation index and sex ratio.

Historical control data:

Historical control data was available to the Study Director.

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

There was one unscheduled adult death (Female 94)on day 50, occurring at a dosage of 750 mg/kg bw/day. The animal had shown hunched posture, pallor of the extremities, apparent hypothermia and piloerection on the previous day. This female had littered but had shown total litter on Day 1 post partum. Necropsy examination revealed enlarged liver, spleen and right adrenal, a pale area on the liver and thin appearance of the non-glandular region of the stomach and raised limiting ridge. Additionally, a pale mass was observed in the right ventricle of the heart during tissue processing. At histopathology examination, the main changes observed were abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies. It is considered likely that sepsis, as a result of complications of pregnancy, was the cause of death. This isolated atypical death was, therefore, considered to be incidental and unrelated to treatment.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

At all dosages, food consumption was lower than control during Days 4-7 of lactation, but group mean values showed no dosage relationship. Food consumption was again lower than control for treated animals during the second week of lactation, with differences being most notable at 750 mg/kg bw/day. These observed differences in food intake of the lactating females may reflect lower demand from the smaller litters for the treated females.

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

For females at 750 mg/kg bw/day, the mean value for mean corpuscular hemoglobin was statistically significantly lower than control. All individual values for these treated females were within the historical control range whist 2/5 control exceeded this historical range. This finding, in the absence of any supporting histopathology, was therefore considered to be incidental and unrelated to treatment.
For females at 350 or 750 mg/kg bw/day, mean total leucocyte count were statistically significantly higher than control principally due to statistically significant higher mean number of lymphocytes. All individual values for these treated females were within the historical control range and this finding, in the absence of any supporting histopathology, was considered to be of little toxicological significance and insufficient to represent an adverse effect.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

For females at 350 or 750 mg/kg bw/day, mean creatinine levels were statistically significantly lower than control but, all individual values were within the historical control range. Whilst changes in mean creatinine levels may indicate slight changes in liver metabolism or kidney performance, in the absence of any supporting histopathological change, they were considered to be of little toxicological significance and not to indicate any adverse effect.
At 350 or 750 mg/kg bw/day, mean total cholesterol levels were statistically significantly higher than control, although mean values showed no dosage relationship for females. For males only 2/5 individual values at 750 mg/kg bw/day exceeded the historical control. For females all values at 350 or 750 mg/kg bw/day exceeded the historical control but so did 3/5 of the control values. Whilst these levels may indicate slight changes in liver metabolism, in the absence of any supporting histopathological change, they were considered to be of little toxicological significance and not to indicate any adverse effect.

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Isolated occasions of noisy respiration were observed for one female at 350 mg/kg bw/day and one female at 750 mg/kg bw/day. At 350 mg/kg bw/day, one female showed piloerection during the behavioral assessment for the third week of gestation but this finding, in isolation, was considered to be incidental and of no toxicological significance. These findings were consistent with the clinical signs observed during routine pot-dosing observations throughout the study and were considered not to indicate any systemic effect of treatment.
At 350 mg/kg bw/day, one female showed piloerection during the behavioral assessment for the third week of gestation but this finding, in isolation, was considered to be incidental and of no toxicological significance.
Grip strength and motor activity assessments did not indicate any adverse effect of treatment for either sex at 100, 350 or 750 mg/kg bw/day.
For females at all dosages, mean hind limb grip strength was statistically significantly lower than control during trial two, however there was no dosage relationship and no other statistically significant differences were apparent during the other trial of grip strength. This finding was therefore considered to be incidental and unrelated to treatment.
For females at 750 mg/kg bw/day, lower motor activity, compared to control was apparent during at the last 20% of the testing period. Motor activity followed the expected pattern of behavior. There were no histopathological findings apparent for the brain or nervous system and no other findings apparent during the study to indicate any neurological effect. In isolation, this finding was considered to be incidental and unrelated to treatment

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

For females at 100 mg/kg bw/day and both sexes at 350 and 750 mg/kg bw/day, absolute and body weight-relative liver weights were statistically significantly higher than control. For this organ, body weight relative values are generally considered to be the more accurate indicator of any toxicological effect. For males, all individual relative weight exceeded the historical control at 350 and 750 mg/kg bw/day compared to 2/5 in the control group. For females, all individual relative weight exceeded the historical control at 100, 350 and 750 mg/kg bw/day, however, so did 4/5 control values. The increase in liver weight may represent adaptive changes in liver metabolism but as there was no evidence of histopathological change detected for this organ, this finding was considered not to represent an adverse effect.
For females at 350 and 750 mg/kg bw/day, absolute and body weight-relative thyroid weights were statistically significantly higher than control, although mean values showed no dosage relationship. At 350 mg/kg bw/day, 11/12 absolute and 10/12 relative weights and at 750 mg/kg bw/day 9/11 absolute and 7/11 relative weights, exceeded the respective historical control range compared to only 3/12 absolute and 2/12 relative weights in the control group. Follicular hypertrophy was observed in the thyroid of some females receiving 350 or 750 mg/kg bw/day and may be the underlying cause of the observed differences in thyroid weights. In the absence of any dosage relationship this finding was considered most likely to be incidental and not to represent an adverse effect of treatment.
For females at all dosages, absolute and body weight-relative ovary weights were statistically significantly higher than control, however, mean values showed no dosage relationship. At 100 mg/kg bw/day, 2/12 absolute and 3/12 relative weights were below the respective historical control range, at 350 mg/kg bw/day, 1/12 absolute values exceeded and 3/12 relative weights were below the respective historical control range and at 750 mg/kg bw/day, 2/11 absolute and 4/11 relative weights were below the respective historical control range. For the control group, however, 6/12 absolute and 11/12 relative weights were below the respective historical control range and it is considered that the observed differences in ovary weight represented atypically low values for the control groups and was unrelated to treatment.
For females at 750 mg/kg bw/day, absolute and body weight-relative adrenal weights were statistically significantly higher than control, however mean values were adversely influence by one female that showed an atypically low adrenal weight. Excluding this animal, all individual absolute and body weight relative weights were within the historical control range. In the absence of any histopathological change this finding was considered to be incidental and unrelated to treatment.

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Follicular hypertrophy was present in the thyroid glands of 1/12, 9/12 and 7/11 females at 100, 350 and 750 mg/kg bw/day respectively; at 350 and 750 mg/kg bw/day this finding correlated with a non-dosage dependent increase in organ weight. No histopathological changes in the thyroid were apparent for males and whilst a direct stand-alone change in the thyroid gland cannot be ruled out, it is considered to be less likely when occurring only in females. Additionally, thyroid activity is increased in females which are pregnant/lactating, therefore, this finding, in view of the lack a true dose-response, may represent an uneven incidence of normal variability for these female animals.
Other incidental findings detected at microscopic evaluation of the tissues did not indicate any effect of treatment at 750 mg/kg bw/day. In particularly, there were no test item-related microscopic findings in the reproductive tracts following the qualitative examination of the stages of spermatogenesis in the testes (no test item-related abnormalities in the integrity of the various cell types present within the different stages of the sperm cycle) or the evaluation of the uterus or of follicles and corpora lutea in the ovaries.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Number of abortions:

no effects observed

Pre- and post-implantation loss:

effects observed, treatment-related

Description (incidence and severity):

Although post-implantation loss and post-natal survival were unaffected by treatment, at 100, 300 & 750 mg/kg bw/day, the mean number of implantations was lower than control leading to lower litter size from birth.

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

350 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks on result:

other: Lower numbers of implantations

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

Group mean values for total litter weights, offspring body weights and body weight changes, a summary incidence of clinical signs, ano-genital distance and visible nipple counts (male offspring) are given in Tables 13, 17, 17 and 19. Individual values and observations are given in Appendices 13, 16, 17 and 18.
At 750 mg/kg bw/day, mean body weight of the offspring was similar to control on Day 1, however subsequent offspring body weight gain was slightly lower than control, leading to lower mean offspring body weight at termination on Day 13 of age. This lower gain at 750 mg/kg bw/day occurred despite the lower litter size at this dosage, compared to control. Litter weight at this dosage was lower than control throughout, initially reflecting the lower litter size and subsequent the lower litter size and weight gain.
At 100 or 350 mg/kg bw/day, there was no effect of maternal treatment on mean offspring body weight on Day 1 and subsequent mean offspring body weight gain to Day 13. Litter weights were lower than control throughout, but this was considered to reflect the slightly lower litter size at both dosages compared to control.

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Description (incidence and severity):

Sex ratio for the offspring was similar to control in all treated groups and did not indicate any selective effect of maternal treatment on survival for either sex at 100, 350 or 750 mg/kg bw/day.

Changes in litter size and weights:

effects observed, treatment-related

Description (incidence and severity):

At 750 mg/kg bw/day, the mean number of implantations was lower than control leading to lower litter size from birth until termination on Day 13. Although one female total litter loss post partum at this dosage, offspring survival for remaining litters was good and there was considered to be no effect of maternal treatment on post-implantation loss or post-natal survival.
At 100 and 300 mg/kg bw/day, the mean number of implantations was also lower than control but, to a lesser extent, than observed at 750 mg/kg bw/day. This resulted in slightly lower litter size from birth although post-implantation loss and post-natal survival appeared unaffected by treatment.

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

no effects observed

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

350 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: Lower litter size and lower offspring growth

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

750 mg/kg bw/day (nominal)

Treatment related:

no

Relation to maternal toxicity:

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

Dose response relationship:

no

Relevant for humans:

not specified

Table 3. Group Mean Functional Test Values

Group/ sex	No of animal /Group	Test 1 Forelimb	Test 1 Hindlimb	Test 2 Forelimb	Test 2 Hindlimb	Test 3 Forelimb	Test 3 Hindlimb	Overall activity	Overall Mobile	Last 20%activity	Last 20%mobile
1(F)	5	975.8	434.2	933.0	423.0	963.2	285.0	401.0	0.0	50.8	0.0
2(F)	5	950.6	338.4*	964.2	303.4	894.0	290.0	412.6	0.0	57.0	0.0
3(F)	5	794.8	212.6**	883.0	343.2	1018.0	413.8	351.4	0.0	32.0	0.0
4(F)	5	1012.6	340.4**	1012.8	321.2	979.0	282.8	301.6	0.0	11.6*	0.0

Table 4. Summary Incidence of Sensory Reactivity Assessments (Scores).

Group/ sex	No of animal /Group	Grasp response	Vocalisation	Toe pinch	Tail pinch	Fingerapproach	Touchescape	Pupilreflex	Blinkreflex	Startlereflex
1	5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
2	5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
3	5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
4	5	0.0	0.0	0.0	0.2	0.0	0.0	0.0	0.0	0.0

Table 5. Group Mean Body Weight and Body Weight Gains Values

Group	Body Weight (g)											Increase in Body Weight (g)
	Day Numbers Relative to Start Date			Gestation				Lactation				Day Numbers Relative to Start Date		Abs gain	% gain	Gestation			Cumulative Body Weight Change (g)Days		Lactation			Cumulative Body Weight Change (g)Days
	1	8	15	0	7	14	20	1	4	7	14	1 - 8	8 - 15	1 - 15	1 - 15	0 - 7	7-14	14-20	0 - 14	0 - 20	1 - 4	4 - 7	7-14	1 - 7	1 - 14
1	211.5	217.8	224.7	227.4	254.5	280.2	339.0	257.8	270.8	276.0	307.8	6.3	6.8	13.2	6.2	27.1	25.7	58.8	52.8	111.6	13.1	5.2	31.8	18.3	50.0
2	211.5	217.2	227.5	226.9	251.0	273.8	325.8	251.6	267.5	277.7	303.1	5.7	10.3	16.0	7.6	24.1	22.8	51.9	46.9	98.8	15.9	10.2	25.4	26.1	51.5
3	206.6	214.3	223.5	220.9	249.8	272.4	324.7	251.0	265.8	277.7	297.9	7.8	9.2	16.9	8.2	28.8	22.7	52.3	51.5	103.8	14.8	11.2	20.9	26.0	46.9
4	211.5	215.0	222.3	220.3	241.8	265.8	315.8	249.5	261.9	268.5	290.0	3.5	7.3	10.8	5.1	21.5	23.9	50.1	45.4	95.5	12.4	6.5	21.5	18.9	40.5

Table 6. Group Mean Food Consumptions and Efficiency

Group/ sex	Day Numbers Relative to Start Date					Group/ sex	Day Numbers Relative to Start Date		Gestation			Lactation
	1 - 8	8 - 15	15 -22	29 – 36	36 - 43		1 - 8	8 - 15	0 - 7	7-14	14-20	1 - 4	4 - 7	7-14
1(M)	23.8	23.8	23.1	24.5	25.4	1(F)	16.1	16.6	21.6	24.5	25.4	31.9	47.7	54.0
2(M)	22.8	22.6	22.6	22.8	23.7	2(F)	17.5	16.3	19.7	22.9	24.8	30.0	41.8	49.4
3(M)	24.3	23.4	23.4	25.1	24.8	3(F)	15.7	16.6	20.5	24.0	24.9	32.4	39.4	49.3
4(M)	24.6	23.6	23.7	25.6	25.8	4(F)	14.6	16.9	19.7	24.2	24.6	34.1	42.0	44.6

Table 7. Summary of Reproductive Index

Group	Mating Index (%)	Number of females showing evidence of regular estrous cycling	Number of females showing di-estrus	Pregnancy Index (%)	Female with living offspring	Parturition Index (%)
1	100	12	12	100	12	100
2	100	12	12	100	12	100
3	100	12	12	100	12	100
4	100	12	11#	100	12@	100@

# One female found dead on Day 50 (Day 7 of lactation) prior to scheduled necropsy

@ = Includes one female which had a total litter loss

Table 8. Group Mean Litter Size

Group	Number of ImplantationSites	Total Number of Offspring Born	Number of Live Offspring
			Day 1	Day 4 BC	Day 4 AC	Day 7	Day 13
1	12.5	11.9	11.9	11.9	10.0	9.9	9.9
2	11.0	9.8	9.8	9.8	8.4	8.4	8.3
3	10.3	10.0	10.0	9.8	8.4	8.4	8.4
4	9.5	8.6	8.6	8.5	7.7	7.7	7.6

 

Table 9. Group Mean Litter Values for Implantation Losses, Survival Indices and Offspring Sex Ratio

Group	Post implantation loss (%)	Live birth index (%)	Viability index 1 (%)	Viability index 2 (%)	Sex ratio (% males) Post partum day
					At birth	1	4BC	4AC	7
1	4.7	100.0	100.0	99.1	45.6	45.6	45.6	51.4	52.0
2	12.0	100.0	100.0	98.5	41.0	41.0	41.0	46.1	46.1
3	1.9	100.0	97.9	100.0	51.4	51.4	51.7	57.0	57.0
4	8.4	99.2	98.9	98.9	40.4	40.8	44.1	44.1	44.1

Table 10. Group Mean Litter Values for Offspring Weights and Litter Weight

Group	Offspring Weight (g)										Litter Weight (g)					Offspring Body Weight Change (g)								Cumulative Offspring Body Weight Change (g)
	Day 1		Day 4 BC		Day 4 AC		Day 7		Day 13		Day 1	Day 4 BC	Day 4 AC	Day7	Day 13	Day 1-4 BC		Day 1-4 AC		Day 4-7 AC		Day 7-13		Day 1-7		Day 1-13
	M	F	M	F	M	F	M	F	M	F						M	F	M	F	M	F	M	F	M	F	M	F
1	5.97	5.67	8.86	8.43	8.87	8.43	13.91	13.36	26.67	25.83	25.83	68.63	101.58	132.55	255.0	2.90	2.77	2.90	2.77	5.04	4.93	12.76	12.47	7.94	7.70	20.70	20.16
2	6.28	6.01	9.06	8.89	9.07	8.91	13.91	13.92	26.81	26.81	25.83	58.51	83.59	112.58	214.77	2.78	2.88	2.79	2.90	2.79	5.00	12.90	12.98	7.63	7.90	20.53	20.88
3	6.11	5.82	8.69	8.33	8.70	8.34	13.17	12.57	25.56	24.61	25.83	58.68	81.00	107.21	208.71	2.58	2.52	2.58	2.52	2.58	4.23	12.39	12.04	7.05	6.75	19.44	18.79
4	6.18	5.72	8.32	7.79	8.32	7.81	11.96	11.24	22.15	21.24	25.83	49.49	65.55	88.06	163.51	2.13	2.06	2.13	2.09	2.13	3.46	10.19	10.01	5.78	5.51	15.97	15.52

Table. 11. Group Mean Litter Values for Offspring Ano-Genital Distance

Group	Male				Female
	Ano-genital Distance (mm)	Body weight on Day 1 (g)	Normalised Ano-genital Distance (mm)	% Male Offspring Showing Visible Nipples	Ano-genital Distance (mm)	Body weight on Day 1 (g)	Normalised Ano-genital Distance (mm)
1	3.18	5.97	1.76	0.0	1.50	5.67	0.84
2	3.36	6.28	1.82	0.0	1.56	6.01	0.86
3	3.30	6.11	1.81	0.0	1.65	5.82	0.92
4	3.56	6.18	1.94	0.0	1.75	5.72	0.98

Table 12. Group Mean Blood Chemical and Haematology Values

Blood chemistry parameters	Female
	Group 1	Group 2	Group 3	Group 4
P mmol/l	1.74	1.60	1.46	1.44
ASAT IU/l	106.2	95.4	135.4	101.4
ALAT (IU/l)	104.0	82.6	121.4	125.4
AP (IU/l)	199.4	184.2	245.2	258.4
Creat mg/dl	0.662	0.584	0.536*	0.538**
Chol mg/dl	113.8	142.2	212.2**	200.0**
Bili mg/dl	0.076	0.088	0.112*	0.120**
Bile acid μmol/l	23.30	28.32	53.92	50.22
Urea mg/dl	58.2	52.4	55.8	52.6
Glucose mg/dl	128.8	124.4	117.8	128.4
Tot. Prot. g/dl	5.672	5.408	5.010**	4.772**
Abumin g/dl	3.22	3.08	2.68**	2.52**
A/G Ratio	1.324	1.336	1.136	1.132
Na+mmol/l	145.4	146.4	144.2	144.2
K+mmol/l	5.418	5.144	5.348	4.864
Cl-mmol/l	102.4	99.6	99.6	100.0
Ca++mmol/l	2.614	2.588	2.478	2.340**
Hematology parameters	Female
	Group 1	Group 2	Group 3	Group 4
Hbg/dl	14.30	14.18	13.88	14.02
RBC 10^12/l	6.928	7.252	6.738	7.472
Hct %	40.40	40.36	39.36	40.66
MCH pg	20.68	19.64	20.68	18.74*
MCV f1	58.46	55.56	58.58	54.48
MCHC g/d1	35.40	35.22	35.12	34.32
WBC 10^9/l	4.78	5.50	6.34*	6.10*
Neut 10^9/l	1.510	1.908	2.278	1.936
Lymp 10^9/l	3.242	3.578	4.062*	4.166*
Mono 10^9/l	0.000n	0.000n	0.000n	0.000n
Eco 10^9/l	0.000n	0.014n	0.000n	0.000n
Bas 10^9/l	0.000n	0.000n	0.000n	0.000n
CT Seconds	8.58	8.74	8.82	8.78
PLT10^9/l	598.0	613.0	592.2	591.6
APTTSeconds	15.22	14.42	15.90	15.06
Retics%	4.08	4.78	4.66	4.58

Table 13. Mean Serum T4 Concentrations (pg/mL).

Group	Adult Terminal Male	Males offspring on Day 13 of age	Females offspring on Day 13 of age
1	43800	39800	40200
2	52400*	41400	43200
3	54200**	39100	41800
4	57100**	33900	36700

Table 14. Group Mean Organ Weights with Corresponding Relative (% of Body Weight) Organ Weights

Organ	Female
	Group 1	Group 2	Group 3	Group 4
Terminal Bodyweight	307.8	303.1	297.9	290.0
Adrenals	0.08984	0.0984	0.08634	0.06886*
Relative weight	0.030	0.030	0.029	0.024*
Brain (Including Cerebrum,Cerebellum And Pons	1.89094	1.88286	1.85480	1.86090
Relative weight	0.631	0.634	0.617	0.629
Heart	1.26666	1.21634	1.24060	1.26134
Relative weight	0.418	0.409	0.413	0.423
Kidneys	1.92546	1.86024	2.11782	1.96906
Relative weight	0.639	0.626	0.702	0.662
Liver	14.9901	16.2430**	18.3088**	19.9560**
Relative weight	4.971	5.451**	6.043**	6.669**
Ovaries	0.08398	0.10168**	0.10708**	0.09728**
Relative weight	0.027	0.034**	0.036**	0.033**
Pituitary	0.01688	0.01684	0.01973	0.01516
Relative weight	0.005	0.006	0.007	0.005
Spleen	0.78504	0.79592	0.76730	0.62180
Relative weight	0.214	0.264	0.254	0.207
Thymus	0.26014	0.28096	0.27406	0.27402
Relative weight	0.087	0.095	0.091	0.091
Thyroid/Parathyroid	0.02671	0.03178	0.03821*	0.03509*
Relative weight	0.009	0.010	0.013*	0.012*
Uterus & Cervix (And Oviducts)	0.54190	0.57278	0.50861	0.59657
Relative weight	0.177	0.192	0.171	0.171

Conclusions:

Based on the results of this study the No Observed Adverse Effect Level (NOAEL) for systemic toxicity of α-phenyl-1H-benzimidazole-2-methanol to the adult animal was considered to be 750 mg/kg bw/day. At 750 mg/kg bw/day, offspring growth was lower than control, therefore, the NOAEL for the offspring was considered to be 350 mg/kg bw/day.

Executive summary:

OECD 422 (2019) - In a combined repeat dose toxicity study with reproductive toxicity screening with Comet Assay (OECD 422), α-phenyl-1H-benzimidazole-2-methanol was administered by gavage to three groups, each of twelve male and twelve female Wistar Han™:RccHan™:WIST strain rats, for approximately six weeks for males and for approximately eight weeks for females (including a two week pre-pairing phase, pairing, gestation and early lactation for females), at dose levels of 100, 350 and 750 mg/kg bw/day.  A control group of twelve males and twelve females was dosed with vehicle alone (Polyethylene Glycol ) over the same period.  A further three males were dosed with N-Nitroso-N-methylurea (vehicle: distilled water) for two consecutive days to act as a positive control group for the comet assay 

Treatment at dosages of 100, 350 and 750 mg/kg bw/day was well tolerated with no adverse effect on body weight gain, food consumption, food conversion efficiency or water consumption for either sex throughout the study.  Food consumption was lower than control for treated females from Day 4 of lactation, with differences being most notable at 750 mg/kg bw/day during the second week of lactation; however, this was considered to reflect lower demand from the smaller litters for treated females, in comparison to their control counterparts, rather than any effect of treatment on the lactating females.  Post-dosing salivation was observed for the majority of animals at 750 mg/kg bw/day and this was also apparent for fewer animals and to a lesser extent at 350 mg/kg bw/day.  Increased post-dosing salivation is frequently observed when animals are dosed via the oral gavage route and is generally considered to reflect slight distaste or irritancy of the dosing formulations rather than any systemic effect of treatment.  Isolated occasions of noisy respiration were observed for all dose groups, including control, although the highest incidence was at 350 mg/kg bw/day and 750 mg/kg bw/day during the study.  The higher incidence of noisy respiration at 350 and 750 mg/kg bw/day may have been influenced by the increased post-dosing salivation observed at these higher dosages and this finding was considered to reflect slight distaste of the test item formulations and/or occasional difficulties in dosing isolated animals rather than any systemic effect of treatment.  

The only unscheduled adult death on the study occurred at 750 mg/kg bw/day, when a female was found dead on Day 50.  This animal had previously shown total litter loss post-partum and hunched posture, pallor of the extremities, apparent hypothermia and piloerection had been apparent on the day prior to death.  Necropsy revealed enlarged liver, spleen and right adrenal, a pale area on the liver and thin appearance of the non-glandular region of the stomach and raised limiting ridge and additionally, a pale mass was observed in the right ventricle of the heart during tissue processing.  Histopathology examination revealed abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies. It was considered that sepsis, as a result of complications of pregnancy, was the underlying cause of death and this isolated atypical occurrence was considered to be unrelated to treatment.  

Behavioral and function observations did not indicate any underlying neurological effect of treatment for either sex at 100, 350 or 750 mg/kg bw/day.  

There was no adverse effect of treatment on hematology or blood chemistry parameters at 100, 350 or 750 mg/kg bw/day.  Some intergroup differences in these parameters did attain statistical significance when compared to control but, in the absence of any supporting histopathological change, they were considered to be of little toxicological significance.

Necropsy of adults revealed a small number of liver findings (eg enlarged, mottled appearance, pale area) for females at 100 and 350 mg/kg bw/day and both sexes at 750 mg/kg bw/day and liver weights were statistically significantly higher than control for females at 100 mg/kg bw/day and both sexes at 350 and 750 mg/kg bw/day.  However, histopathological evaluation of the liver did not reveal any evidence of hepatic change and, while some adaptive alteration to liver metabolism may have occurred, these findings were considered not to represent an adverse effect of treatment.    

For females at 350 and 750 mg/kg bw/day, absolute and body weight-relative thyroid weights were statistically significantly higher than control, but mean values showed no dosage relationship. At both dosages, the majority of individual absolute and body weight-relative weights exceeded the respective historical control range, but again, these incidences showed no dosage response.  Follicular hypertrophy was present in the thyroid glands of 1/12, 9/12 and 7/11 females at 100, 350 and 750 mg/kg bw/day respectively but showed no true dose response and this follicular hypertrophy may be the underlying cause of the observed differences in the thyroid weights at 350 and 750 mg/kg bw/day.  No histopathological changes in the thyroid were apparent for males and, whilst a direct stand-alone change in the thyroid gland is possible, it is considered to be less likely when occurring only in females. Thyroid activity is increased in females which are pregnant/lactating and, in view of the lack a true dose-response, these findings was considered to reflect an uneven incidence of normal variability for these female animals within the study rather than an adverse effect of treatment.

All other statistically significant differences in organ weights observed during the study were not supporting by any accompanying histopathological change and were considered to be of little toxicological significance and not to represent an adverse effect.  

There was no effect of treatment on estrous cycles of females, mating performance or gestation length at 100, 350 or 750 mg/kg bw/day.  Although, there was no effect on fertility, as assessed by the number of females that achieved pregnancy at 100, 350 or 750 mg/kg bw/day, the number of implantations was lower than control at 750 mg/kg bw/day.  The number of implantation were also lower than control at 100 and 350 mg/kg bw/day but the differences were slight and probably reflect normal biological variation.  Histopathological evaluations of reproductive tissues at 750 mg/kg bw/day did not reveal any test item-related microscopic findings for the reproductive tissues and, in particular, there were no test item-related abnormalities in the integrity of the various cell types present within the different stages of the sperm cycle or for follicles and corpora lutea in the ovaries.  The lower number of implantations at 750 mg/kg bw/day is therefore unexplained, and while it this may also reflect normal variation, an effect of treatment cannot be discounted.

Subsequent post-implantation and post-natal survival of the offspring was unaffected by treatment at all dosages.  One female at 750 mg/kg bw/day did show total litter post partum but this was considered to reflect a decline in the clinical condition for this animal due to sepsis, as a result of complications of pregnancy, and therefore the high offspring mortality for this particular litter was considered to be unrelated to maternal treatment.  Mean offspring body weight on Day 1 of age was similar to control at all dosages but, body weight gain at 750 mg/kg bw/day was slightly lower than control, despite the lower litter size at this dosage, leading to lower mean offspring body weight at termination on Day 13 of age.  A number of small offspring were noted during clinical observations and at necropsy, consistent with this lower gain and litter weight at 750 mg/kg bw/day was lower than control throughout, initially reflecting the lower litter size and subsequent the lower litter size and weight gain. At 100 or 350 mg/kg bw/day, there was no effect of maternal treatment on offspring body weight gain to Day 13; litter weights were lower than control throughout, but this reflected the slightly lower litter size at both dosages.

Mean offspring ano-genital distance (actual and normalized) for males at 100 mg/kg bw/day and both sexes appeared longer than control at 100, 350 or 750 mg/kg bw/day; mean values for males at 100 and 350 mg/kg bw/day showed no dosage relationship.  For female offspring at 100 mg/kg bw/day, measured ano-genital distance was longer than control, but was similar to control when normalized for body weight.  All individual litter values for ano-genital distance, normalized for body weight, were within the historical control range at 100, 350 or 750 mg/kg bw/day.  As no normalized for body weight values for either sex were outside the normal historic range, an effect of treatment on ano-genital distance appeared unlikely and this finding was considered to be incidental and of no toxicological significance.  Evaluation of visible nipple count for male offspring on Day 13 post partum did not reveal any effect of maternal treatment at 100, 350 or 750 mg/kg bw/day.  

For the additional comet investigation, there were no significant increases in the percentage tail intensity or median percentage tail intensity for the jejunum, glandular stomach or liver at 100, 350 or 750 mg/kg bw/day and the test item was, therefore, considered to not induce DNA damage in these tissues under the conditions of the test.

The mean levels of thyroxine (T4) in adult males were statistically significant higher then control at 100, 350 and 750 mg/kg bw/day, although mean values showed no dosage-relationship at the lower dosage levels.  These differences from control for T4 levels in males occurred in the absence of any effect on organ weight or evidence of histopathological change for the male thyroid and, therefore, this finding was considered to be incidental and unrelated to treatment.

Under the condition of this study, the No Observed Adverse Effect Level (NOAEL) for systemic toxicity of α-phenyl-1H-benzimidazole-2-methanol to the adult animal was considered to be 750 mg/kg bw/day.

Lower numbers of implantations were apparent for females at 750 mg/kg bw/day and as the etiology of this finding was unknown, the NOAEL for reproduction was considered to be 350 mg/kg bw/day.  

At 750 mg/kg bw/day, offspring growth was lower than control although there was no accompanying effect on offspring survival or development; the NOAEL for the offspring was considered to be 350 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

350 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The endpoint is concluded based on a single key study with a Klimisch rating of 1. The database for this endpoint met all relevant data requirements under REACH for the respective tonnage band.

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

OECD 422 (2019) - In a combined repeat dose toxicity study with reproductive toxicity screening with Comet Assay (OECD 422), α-phenyl-1H-benzimidazole-2-methanol was administered by gavage to three groups, each of twelve male and twelve female Wistar Han™:RccHan™:WIST strain rats, for approximately six weeks for males and for approximately eight weeks for females (including a two week pre-pairing phase, pairing, gestation and early lactation for females), at dose levels of 100, 350 and 750 mg/kg bw/day.  A control group of twelve males and twelve females was dosed with vehicle alone (Polyethylene Glycol ) over the same period.  A further three males were dosed with N-Nitroso-N-methylurea (vehicle: distilled water) for two consecutive days to act as a positive control group for the comet assay.

At 750 mg/kg bw/day, Female 94 was found dead on Day 50 of the study, after having shown hunched posture, pallor of the extremities, apparent hypothermia and piloerection on Day 49.  Histopathology examination revealed abscessation in the lungs and marked inflammatory change in the heart with the presence of bacterial colonies.  It is considered likely that sepsis, as a result of complications of pregnancy, was the underlying reason for mortality and this isolated atypical occurrence was considered to be incidental and unrelated to treatment.

There were no clinical signs observed that indicated any systemic effect of treatment for either sex at 100, 300 or 750 mg/kg bw/day.

Behavioral assessments were unaffected by treatment at 100, 350 and 750 mg/kg bw/day. Functional performance tests were unaffected by treatment at 100, 350 and 750 mg/kg bw/day.

Sensory reactivity assessments were unaffected by treatment at 100, 350 and 750 mg/kg bw/day.

There was no effect of treatment on body weight gain throughout the study for either sex, including for females during gestation and lactation phases, at 100, 350 or 750 mg/kg bw/day.

There was no effect of treatment on food consumption of males throughout the study or of females during the pre-pairing or gestation phases at 100, 350 or 750 mg/kg bw/day.  At all dosages, food consumption was lower than control from Day 4 of lactation and whilst group mean values showed no dosage relationship, the difference from control was most notable at 750 mg/kg bw/day during the second week of lactation.  The observed differences in food intake for these females was considered to reflect lower demand due to smaller litter size for the treated females.

There was no effect of treatment on food conversion efficiency of either sex during the pre-pairing phase of the study or for males during the post-pairing phase at 100, 350 or 750 mg/kg bw/day.  Visual inspection of water bottles throughout the study did not indicate any effect of treatment for either sex at 100, 300 or 750 mg/kg bw/day. There was no effect of treatment on estrous cycles of females and mating performance were unaffected with all female achieving pregnancy at 100, 350 or 750 mg/kg bw/day. Gestation length was unaffected by treatment at 100, 350 or 750 mg/kg bw/day.

At 750 mg/kg bw/day, the mean number of implantations was lower than control leading to lower litter size from birth, however, there was no effect of maternal treatment on post-implantation loss or post-natal survival. At 100 and 300 mg/kg bw/day, implantation count was lower than control but, to a lesser extent, than observed at 750 mg/kg bw/day, and resulted in slightly lower litter size from birth, although post-implantation loss and post-natal survival were unaffected by treatment. Sex ratio for the offspring was unaffected by maternal treatment at 100, 350 or 750 mg/kg bw/day. At 750 mg/kg bw/day, offspring body weight gain was slightly lower than control, despite the lower litter size at this dosage, leading to lower mean offspring body weight at Day 13 of age.  Litter weight at 750 mg/kg bw/day, was lower than control throughout, initially reflecting the lower litter size and additionally the lower weight gain as lactation progressed.   At 100 or 350 mg/kg bw/day, mean offspring body weight on Day 1 and subsequent mean offspring body weight gain to Day 13 were unaffected by maternal treatment.  Litter weights were lower than control throughout lactation but this reflected the slightly lower litter size at these dosages compared to control. At 750 mg/kg bw/day, there was a higher incidence of small offspring consistent with the lower offspring growth at this dosage, but otherwise, offspring clinical signs appeared unaffected by maternal treatment at all doses.  Mean ano-genital distance for offspring (both sexes) generally appeared longer than control at 100, 350 or 750 mg/kg bw/day, but all normalized for body weight values, for either sex,  were within the normal historic range and this finding was considered to be incidental and of no toxicological significance.   Visible nipple count for male offspring on Day 13 post partum was unaffected by maternal treatment at all treatment dose.

There was no adverse effect of treatment on blood chemistry and hematological parameters at all tested dose.The mean levels of thyroxine (T4) in adult males were statistically significant higher than control at all treatment groups, this effect was not observed in offspring.

At 750 mg/kg bw/day, there was a higher incidence of small offspring at necropsy, consistent with the lower offspring growth at this dosage, but otherwise, offspring necropsy findings appeared unaffected by maternal treatment. Necropsy findings did not indicate any adverse effect of treatment.

There was no adverse effect of treatment on organ weights and histopathology did not reveal any evidence of adverse effects at treatment dosage. It was noted that absolute and body weight-relative thyroid weights were statistically significantly higher than control for females at 350 and 750 mg/kg bw/day.  This increase in thyroid weights appeared to reflect follicular hypertrophy in the thyroid of some females at these dosages, however, neither the incidence of this microscopic finding nor the differences in mean thyroid weights showed any dosage relationship and this finding was considered not to represent an adverse effect of treatment.

Comet assay investigations during the study did not show any treatment induced DNA damage in the jejunum, glandular stomach or liver under the conditions of the test at 100, 350 and 750 mg/kg bw/day. The No Observed Adverse Effect Level (NOAEL) for systemic toxicity for the adult animal was considered to be 750 mg/kg bw/day. At 750 mg/kg bw/day, offspring growth was lower than control, therefore, the NOAEL for the offspring was considered to be 350 mg/kg bw/day.

Mode of Action Analysis / Human Relevance Framework

During the treatment period of the OECD 422 study there was no effect on fertility based on the number of females that achieved pregnancy at all dose groups,  however, the number of implantations was lower than control at 750 mg/kg bw/day. The number of implantation were also lower than control at 100 and 350 mg/kg bw/day but the differences were slight and attributed to normal biological variation.   This was reflected in the lower offspring growth albeit without accompanying effect on offspring survival or development and offspring necropsy findings appeared unaffected. Histopathological evaluations of reproductive tissues at 750 mg/kg bw/day did not reveal any test item-related microscopic findings for the reproductive tissues and, in particular, there were no test item-related abnormalities in the integrity of the various cell types present within the different stages of the sperm cycle or for follicles and corpora lutea in the ovaries. The effects observed in this study are considered slight and therefore they are not suitable with which to conclude on a mode of actions. For the purpose of hazard assessment, these effects were considered relevant for humans and have thus been considered in the derivation of derived no-effect levels (DNELs).

Justification for classification or non-classification

Based on the observations in the OECD 422 study, the substance does not meet the criteria for classification in accordance with Regulation (EC No. 1272/2008 (CLP).

The key results from the OECD 422 study indicate a lower number of implantations at 750 mg/kg bw/day, slightly lower mean offspring weight gain at 750 mg/kg bw/day and a higher incidence of small offspring at 750 mg/kg bw/day.

Although the mean number of implants was lower at 750 mg/kg/day, there was a considerable within-group variation.  Generally, when there is a true reduction in the number of implantations this will be shown by a slight reduction in each female, rather than the very large within-group variation.  For young female rats, the number of implants will generally be lower, because the rat will still on quite a steep growth curve.  As such, although the NOAEL for this endpoint was determined to be 350 mg/kg/ bw/day based on data observations alone, it is quite possible that the effect is merely a chance distribution of the smaller litter to the treated groups in general and to the high dose group in particular.

There is a slightly lower pup weight gain at 750 mg/kg/day, but it is not possible to state with certainty that this is related to treatment.  Again, based on the data alone a conservative NOAEL of 350 mg/kg bw/day was determined.  There is an interaction between litter size and pup weight, but pups of small litters will not necessarily be larger as a consequence of coming from a small litter.  The observed “small offspring” refers to clinical signs, and this observation will merely supplement the data from pup body weights.

It is not appropriate to classify the substance for reproductive toxicity, because the effects are slight and would not necessarily be repeated in a larger study.  The OECD 422 study is a screening study and the available information does not support classification under the CLP criteria.