1-[5-(2,6-difluorophenyl)-4,5-dihydro-1,2-oxazol-3-yl]ethanone

Toxicity to reproduction

Administrative data

Endpoint:

multi-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3800 (Reproduction and Fertility Effects)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: MAFF Japan Test Guidelines for Agricultural Chemicals 2-1-17 Notification 12-Nousan-8147 (2000)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Test material form:

solid

Details on test material:

Purity: 89.7% by analysis

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)

Details on species / strain selection:

The rat was selected for this study because it is a preferred species for reproductive toxicity testing and recommended by regulatory guidelines. The Crl:CD(SD) strain was chosen because extensive background data are available from the literature. This strain is also considered suitable relative to longevity, hardiness, and incidence of spontaneous disease.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories International, Inc., Raleigh, North Carolina, U.S.A.
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: approximately 41 days old
- Weight at study initiation: 223.5 to 299.1 grams (males) and 175.3 to 230.8 grams (females) the day after arrival
- Housing: All male animals were housed individually during non-mating periods in solid-bottom caging with bedding containing Nestlets™as enrichment. Each cage rack contained only animals of one sex, except during cohabitation when the animals were housed as breeding pairs (female in male’s cage). Fourteen days after the first day of cohabitation, females without evidence of copulation were housed singly. During lactation periods, adult females were housed with their litters.
- Diet: PMI® Nutrition International, LLC Certified Rodent LabDiet® 5002 ad libitum
- Water: All animals were provided tap water ad libitum
- Acclimation period: 11 days
ENVIRONMENTAL CONDITIONS
- Temperature: 20-26ºC (68-79ºF)
- Humidity: 30-70%
- Photoperiod: 12-hour light/dark cycle
- Air changes (per hr): Not reported

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): Test substance was added to the diet and thoroughly mixed for a period of time that was adequate to ensure homogeneous distribution in the diet. The diet preparation was corrected for the sponsor-reported purity. Control diets were mixed for the same period of time.
- Storage temperature of food: The diets were used within the period of established stability and were stored in the refrigerator until used.

Details on mating procedure:

- M/F ratio per cage: one male and one female per cage during mating
- Length of cohabitation: Until the evidence of copulation was observed or until two eeks elapsed. The cohabitation period ended on the morning on day 15 of pairing.
- Any other deviations from standard protocol: No

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were taken from the diet mixer, stored and analysed to verify concentration, homogeneity, and stability of test substance in the diets. Samples were collected from the top, middle, and bottom of the initial diet preparation for each diet concentration and were analysed to verify the homogeneity and concentration (average of homogeneity samples) of test substance in the diets. Stability of the test substance in the concentration range from 100 to 18000 ppm in the diet stored at room temperature for up to 22 days has been established in a previously conducted study. However, for this study, an additional set of samples was taken from the lowest and highest dietary concentration of the initial diet preparation and analyzed to verify extended stability of test substance in the diets. The stability of test substance in the diet was demonstrated by comparing samples stored at room temperature or refrigerated with the average measured values of top, middle, and bottom homogeneity samples. To ensure that diets were analyzed at regular intervals, samples to verify concentrations were taken from at least 2 more different time points for each of the concentrations throughout the course of the study. A sample of control diet was analyzed together with each set of samples to verify the absence of test substance in the diet.
Analysis was performed by the DuPont Haskell Regulatory Analytical group. At the time of the analysis, the samples were extracted with an appropriate solvent and the extracts were analyzed by ultra high-performance liquid chromatography (UHPLC) with ultraviolet (UV) detection.

The analyses results show that the test substance was homogeneously mixed and on target for all concentrations levels analyzed during the study period. Homogeneity of the 120 ppm diet was reached when the formulations were prepared by adding the test substance pre-dissolved in acetone to the rodent chow. The test substance was homogeneously mixed and on target for all concentration levels analyzed, except for the 480 ppm sample. For this single concentration on this single date, the results from the analysis of the samples collected indicated that these samples were outside of the range of acceptable values for concentration verification and diet homogeneity. This atypical result is not considered to have adversely impacted the study because it was the only occurrence of a less than acceptable result for this concentration which was analyzed at several points during the course of the study. Additionally, the data indicate that the diets were otherwise on target, homogeneous, and stable under the conditions of use at concentrations both lower and higher than 480 ppm. The test substance was homogeneously mixed and on target for all concentration levels analyzed. The data also show that the test substance losses homogeneity when stored at room temperature in the diet with time, therefore stability of the test substance was only reached up to 17 days of room temperature storage in the diet at the concentration range from 120 to 12800 ppm. In addition, the data show that the test substance was stable in the diet when stored refrigerated for up to 32 days in the concentration range from 120 to 7260 ppm.

The test substance was not detected in the control samples.

Duration of treatment / exposure:

Dietary administration of the test substance for P1 animals began on test day 1 and continued until the day of sacrifice. Measured dietary administration of the test substance for F1 animals began on PND 21, and continued until the day of sacrifice.

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

200 ppm

Doses / concentrations 2

Dose / conc.:

800 ppm

Doses / concentrations 3

Dose / conc.:

3 200 ppm

Doses / concentrations 4

Dose / conc.:

12 100 ppm

No. of animals per sex per dose:

30

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: Dietary concentrations of 0, 200, 800, 3200, and 12800 ppm were originally selected for the current study based on the results of a previous one-generation reproduction study. After approximately 7 weeks of exposure during the current study, body weight reductions at the highest concentration were of sufficient magnitude such that it was deemed necessary to reduce the concentration to 12100 ppm from that point forward.

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily throughout the study

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily throughout the study

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly schedule and at sacrifice

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

Oestrous cyclicity (parental animals):

Estrous cycle parameters were evaluated daily for 3 weeks prior to cohabitation and up to the day of presumed mating in P1 and F1 adult rats.

Sperm parameters (parental animals):

Parameters examined in [all/P/F1/F2] male parental generations: Sperm motility, morphology, concentration in the cauda epididymis, and spermatid concentration in the testis were determined for P1 and F1 adult rats at the terminal sacrifice.

Litter observations:

Litter examinations (live, dead, or missing pups, individual pup weights, clinical observations) were determined at birth, on PND 4, and weekly during the 21-day lactation period.

Postmortem examinations (parental animals):

Ovarian Follicle Counts:
A quantitative evaluation of primordial and growing follicles was conducted on 10 lactating F1 females (surviving to scheduled sacrifice) from control and high-dose (12100 ppm) groups. No treatment-related change was observed; therefore, counting of follicles in intermediate groups to determine a no-effect level was not required. Six ovarian cross sections (5 μm thick) were taken from the central area of the ovary using a step section technique. Primordial and growing follicles (up to but not including antral follicles) were enumerated for up to 12 ovarian sections per animal.

SACRIFICE
P1 and F1 Adults
Method of Euthanasia:
All adult females that were scheduled (SS) or unscheduled (US) sacrifices and all adult males that were unscheduled sacrifices (US) were euthanized by isoflurane anesthesia and exsanguination. All adult males that that survived until the scheduled sacrifice (SS) were euthanized by CO2 inhalation and exsanguination. Carbon dioxide anesthesia alone was used in these surviving males in order to avoid the effects of isoflurane on sperm motility. The order of sacrifice for scheduled deaths, for each generation, was random among all treatment groups within each sex.

Postmortem Examinations:
All P1 (30/sex/concentration) and F1 (30/sex/concentration) adult rats received a gross pathological examination. The necropsy included examination of the external surface, all orifices, and the cranial, thoracic, abdominal, and pelvic cavities, including viscera. The uteri of all cohabited P1 and F1 adult females were examined for the presence and number of implantation sites.

Organ Weights:
The following organs were weighed fresh at necropsy from all P1 and F1 adults at the scheduled sacrifice. Paired organs were weighed together. Group mean values, organ weight ratios (% body weight and % brain weight), and combined accessory sex organs (ASO) values were calculated. Final body weight data were used for the calculation of organ/body weight ratios.

Tissues Collected:
The following tissues were collected from all P1 and F1 adults and preserved in appropriate fixative (10% neutral buffered formalin or modified Davidson’s solution) for histopathological examination (or possible future examination).

Histopathology:
Tissues designated for microscopic evaluation were embedded in paraffin, cut at a nominal thickness of 5 micrometers, stained with hematoxylin and eosin (H&E), and examined microscopically by a veterinary pathologist. A second veterinary pathologist peer reviewed representative tissue slides, as well as other pathology data and interpretations. Tissues collected at necropsy were processed and evaluated microscopically in the first 10 parental rats (i.e., the first 10 consecutive animal numbers in each group that parented a litter) surviving to scheduled sacrifice in the P1 and F1 male and female control and high-dose groups. Any organs demonstrating potential test substance-related microscopic findings in the first 10 parental high-dose males or females were subsequently examined in the remaining rats in that generation and sex in order to establish the effect and no-effect levels. In the current study, the liver and thyroid were examined from adult rats (30/sex/dose/generation) in groups 1, 3, 4 and 5. Additionally, the available kidneys (P1 and F1, both sexes) and spleen (P1 females) were examined in groups 1 and 5. The reproductive organs from rats with impaired reproductive performance (i.e., reproductive failures: failed to produce a litter) were evaluated from all adult groups. Microscopic examination of tissues from other P1 and F1 adult rats that died before the scheduled sacrificed was limited to gross lesions. These early decedents included 1 P1 female and 1 F1 female. Most gross lesions in P1 and F1 adults were saved and evaluated microscopically. Selected gross observations for which a microscopic diagnosis would not be additive were saved, but not processed for microscopic evaluation.

Postmortem examinations (offspring):

F1 and F2 Weanlings
On day 21 postpartum, some offspring in the F1 litters were selected (one rat/sex/litter, when possible) to become F1 adults and parents of an F2 generation.

SACRIFICE
Method of Euthanasia:
On day 21 postpartum, offspring in the F1 and F2 litters that were selected for organ weights and/or postmortem examination were euthanized by isoflurane anesthesia followed by CO2 inhalation. All remaining weanlings, excluding those F1 weanlings selected to become F1 adults, were similarly euthanized.

Postmortem Examinations, Organ Weights, and Histopathology
One weanling/sex/litter (litter size permitting) underwent a gross pathological examination. Selected organs were weighed at necropsy (brain, spleen, thymus). Suspect target organs (liver, thyroid, spleen) were saved for microscopic evaluation. Microscopic evaluation of weanling tissues included all saved thyroids and livers (groups 1, 3, 4, 5) and spleens (groups 1, 5) in the F1 and F2, males and females.

F1 and F2 Pups
SACRIFICE
Method of Euthanasia: Pups through lactation day 4 were euthanized by decapitation. For lactating pups between lactation days 5 and 20, euthanasia was achieved by an intraperitoneal injection of a commercial euthanasia agent.

Postmortem Examinations:
Pups (nursing offspring) that died during the lactation period or were sacrificed due to the death of the dam underwent a gross pathological evaluation and the carcass was discarded. Organs were not weighed and tissues were not saved.

Sperm Assessment:
Sperm parameters for all surviving P1 parental males were evaluated. The right epididymis was removed, and the right cauda epididymis was weighed. Sperm was collected from the right cauda epididymis for evaluation of motility and morphology. The left epididymis and testis were frozen in liquid nitrogen and stored between -65°C and -85°C for sperm and spermatid counts, respectively.

Statistics:

See any other information on materials and methods incl. tables.

Reproductive indices:

Reproductive indices were tested

Offspring viability indices:

Offspring viability was performed

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

The incidence of animals with hair loss was increased at 3200 and 12100 ppm; 4 and 3 males from each of these respective groups were affected. These increases were considered to be spurious since this is a common finding, and it was not observed in the P1 females or in either the F1 males or F1 females. All other clinical observations were unremarkable and not considered to be related to the test substance because they were not dose dependent and occurred in only one or 2 animals from any group. There were no test substance-related clinical observations in P1 females during premating, gestation, and lactation periods. All reported observations were unremarkable, occurred infrequently, and were not dose dependent

Mortality:

mortality observed, non-treatment-related

Description (incidence):

There was no test substance-related mortality in P1 males. All males survived to the scheduled sacrifice. There was no test substance-related mortality in P1 females. However, one female at 200 ppm was
euthanized on test day 72 due to lymphoma.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related systemic toxicity during the in-life portion of the study was limited to reductions in body weight at 3200 and 12100 ppm in adult P1 male and/or female rats. There were no adverse effects
on body weights in P1 adult rats at 800 ppm or lower.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Test substance-related systemic toxicity during the in-life portion of the study was limited to reductions in food consumption parameters at 3200 and 12100 ppm in adult P1 male and/or female rats. There were
no adverse effects on nutritional parameters in P1 adult rats at 800 ppm or lower.

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

Reductions in food consumption parameters at 3200 and 12100 ppm in adult P1 male and/or female rats. There were no adverse effects on nutritional parameters in P1 adult rats at 800 ppm or lower.

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):

In addition, thyroid follicular cell hypertrophy occurring secondary to the induction of liver metabolizing enzymes was present in P1 males and females at 12100 ppm. These secondary thyroid changes are known to be rat-specific and not relevant to humans.

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

effects observed, non-treatment-related

Description (incidence and severity):

In P1 males, there were no test substance-related effects on sperm parameters at any dietary concentration tested. The data for testicular and epididymal sperm counts, motility, and morphology were c
omparable to control group data at all concentrations tested. A single instance of statistical significance in caudal sperm counts in F1 males at 12,100 ppm was not considered to be toxicologically relevant
since the magnitude of the reduction was minimal (12% lower than control) and the data were not dose dependent. Caudal sperm count means of 238.5, 229.2, 210.4, 230.1, and 208.2 were reported at 0, 200,
800, 3200, and 12100 ppm, respectively. All values fall well within the test facility historical control data range for this endpoint.

Reproductive performance:

no effects observed

Description (incidence and severity):

The data for mating, fertility, precoital interval length, gestation length, and implantation site counts were comparable across all groups tested for each respective generation. Additionally, there were no adverse,
treatment-related effects noted on pup survival indices, estrous parameters, or sperm parameters at any concentration for either generation.

Effect levels (P0)

Key result

Dose descriptor:

NOAEL

Effect level:

800 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Results: F1 generation

General toxicity (F1)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

All reported clinical observations were unremarkable and not considered to be related to the test substance, because they were not dose dependent and occurred in only one, 2, or 3 animals from any group. There were no test substance-related clinical observations in F1 females during premating, gestation, and lactation. All reported observations were unremarkable, occurred infrequently, and were not dose dependent

Mortality / viability:

mortality observed, non-treatment-related

Description (incidence and severity):

There was no test substance-related mortality in F1 males. All males survived to the scheduled sacrifice. There was no test substance-related mortality in F1 females. However, one female at 800 ppm was euthanized on lactation day 0 due to endometritis.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related systemic toxicity during the in-life portion of the study was limited to reductions in body weight at 3200 and 12100 ppm in F1 male and/or female rats. There were no adverse effects on body weights in F1 adult rats at 800 ppm or lower.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Test substance-related systemic toxicity during the in-life portion of the study was limited to reductions in food consumption parameters at 3200 and 12100 ppm in F1 male and/or female rats. There were no adverse effects on nutritional parameters in F1 adult rats at 800 ppm or lower.

Food efficiency:

effects observed, non-treatment-related

Description (incidence and severity):

Mean food efficiency data were generally comparable to control group values throughout the premating period. Cumulative mean food efficiency values from test days 1 to 71 were within 1% of control at all concentrations tested. Occasional instances of statistical significance occurred at 3200 and 12100 ppm and reflected both increases and decreases; none of these changes impacted the cumulative data

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

Non-adverse test substance-related increases in liver and kidney weight in one or more parental groups administered ≥800 ppm were considered adaptive changes associated with induction of metabolizing enzymes. At 12100 ppm, the liver weight changes were associated with microscopic hepatocellular hypertrophy. In addition, thyroid follicular cell hypertrophy occurring secondary to the induction of liver metabolizing enzymes was present in F1 females at 12100 ppm and in F1 males at ≥3200 ppm. These secondary thyroid changes are known to be rat-specific and not relevant to humans.

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

Effect levels (F1)

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

800 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Results: F2 generation

General toxicity (F2)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In F2 offspring, beginning on postnatal day 4 and persisting throughout lactation at 12100 ppm. Mean pup weights ranged from 11 to 18% lower than the respective control means.
At 3200 ppm, mean F2 pup weights were slightly and statistically significantly lower on postnatal days 14 and 21; mean pup weights were 5 and 6% lower than respective controls at both weighings.
Because of the magnitude of the changes, the effects on mean pup weight at 12100 ppm were considered to be adverse. Due to the minimal magnitude of the change at 3200 ppm, the pup weight effects at 3200 ppm were not considered to be adverse.
There were no test substance-related reductions in pup weight at 800 ppm or lower.

Sexual maturation:

effects observed, non-treatment-related

Description (incidence and severity):

Because the initial review of the developmental landmark data revealed statistical changes, the measurement of anogenital distance in F2 offspring was a triggered endpoint. There were no test substance-related effects on anogenital distance at any dietary concentration tested.

Overall reproductive toxicity

Key result

Reproductive effects observed:

no

Lowest effective dose / conc.:

12 000 ppm

Applicant's summary and conclusion

Conclusions:

NOAEL (systemic and offspring): 800 ppm
NOAEL (reproductive toxicity): 12100 ppm

Executive summary:

The objective of this study was to evaluate the effect of the test substance on the gonadal function, conception, parturition, and growth and development of male and female Crl:CD(SD) rats over 2 generations involving the production of one set of litters in each generation. The test substance was administered orally because it is a potential route for human exposure and is a route recommended by regulatory agencies for this type of study. In the current study, groups of rats (30/sex/concentration) were exposed to the test substance via the diet at concentrations of 0, 200, 800, 3200, or 12100 ppm. During lactation and for the first 3 weeks post-weaning for the F1generation adults, the dietary concentrations were reduced to 0, 120, 480, 1920, or 7260 ppm to maintain relatively constant mean daily intake levels of the test substance during these periods of increased maternal food consumption. Samples of the test diets were analyzed and confirmed to be at targeted concentrations, homogeneously mixed, and stable under the conditions of use for the study. Mean daily intake values (mg/kg/day) for the various phases of the study are tabulated below. To simplify reporting the effects at each dietary concentration, the groups will be referred to by the full (unreduced) concentration values. Following at least 10 weeks of exposure to the test substance (premating), P1 and F1 generation males and females were co-housed within their respective treatment groups to produce F1 and F2 litters, respectively. Dams were allowed to deliver and rear their offspring until weaning on postnatal day 21 (PND 21). F1 and F2 litters were culled to 4 pups/sex/litter (litter size permitting) on PND 4; all remaining pups were discarded without further evaluation. At weaning, selected F1 offspring (one rat per sex per litter when possible) were randomly selected to serve as parents for the F2 generation. F2 litters were terminated at weaning. Clinical observations, body weight, and food consumption were determined weekly throughout the study. Litter examinations (live, dead, or missing pups, individual pup weights, clinical observations) were determined at birth, on PND 4, and weekly during the 21-day lactation period. Estrous cycle parameters were evaluated daily for 3 weeks prior to cohabitation and up to the day of presumed mating in P1 and F1 adult rats. The age at either vaginal opening or preputial separation was recorded for the F1generation. Anogenital distance measurements were recorded for F2 offspring. Sperm motility, morphology, concentration in the cauda epididymis, and spermatid concentration in the testis were determined for P1 and F1 adult rats at the terminal sacrifice.

 

Gross postmortem examinations were performed on selected animals, and selected organs were weighed and/or retained for histopathological examination. A quantitative evaluation of ovarian follicles was conducted on 10 lactating F1 females from the control and high-dose (12100 ppm) groups.

 

Test substance-related systemic toxicity during the in-life portion of the study was limited to reductions in body weight and food consumption parameters at 3200 and 12100 ppm in adult P1 and F1 male and/or female rats. There were no adverse effects on body weight or nutritional parameters in P1or F1 adult rats at 800 ppm or lower. There was no test substance-related mortality, nor were there any adverse test substance-related clinical observations.

 

Similar to and consistent with the parental body weight effects, test substance-related reductions in offspring weights during lactation were observed at 3200 ppm (F2 generation) and 12100 ppm (F1 and F2 generation). Test substance-related delays in the onset of puberty were also observed in F1 offspring at 12100 ppm; however, these delays were considered secondary to the body weight effects that were evident at these concentrations. There were no adverse test substance-related effects on reproductive outcomes or on offspring at any exposure concentration tested in either the P1 or F1 generations. The data for mating, fertility, precoital interval length, gestation length, and implantation site counts were comparable across all groups tested for each respective generation. Additionally, there were no adverse, treatment-related effects noted on pup survival indices, estrous parameters, or sperm parameters at any concentration for either generation.

 

There were no adverse gross or microscopic anatomic pathological changes or organ weight changes at any dietary concentration tested. No adverse changes in pathology parameters were observed in P1 or adult F1 generation males and females or in the F1 and F2 male and female offspring. Non-adverse test substance-related increases in liver and kidney weight in one or more parental groups administered ≥800 ppm were considered adaptive changes associated with induction of metabolizing enzymes. At 12100 ppm, the liver weight changes were associated with microscopic hepatocellular hypertrophy. In addition, thyroid follicular cell hypertrophy occurring secondary to the induction of liver metabolizing enzymes was present in P1 males and females at 12100 ppm, in F1 females at 12100 ppm and in F1 males at ≥3200 ppm. These secondary thyroid changes are known to be rat-specific and not relevant to humans.

 

Under the current experimental conditions, adverse test substance-related effects were limited to decreases in body weights and/or food consumption parameters in adults and offspring at 3200 and 12100 ppm. The no-observed-adverse-effect level (NOAEL) for adult systemic and offspring toxicity was 800 ppm. There was no evidence of reproductive toxicity at any dietary concentration tested. The NOAEL for reproductive toxicity was 12100 ppm, the highest dose tested.