1,3-bis(isocyanatomethyl)benzene

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 24 to August 25, 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study was initiated after final decision CCH-D-2114489560-42-01/F was received, in which ECHA requested to submit information on a pre-natal developmental toxicity study (Annex IX, Section 8.7.2.; test method: OECD TG 414) in a first species (rat or rabbit), oral route with the registered substance.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

25 June 2018

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,3-bis(isocyanatomethyl)benzene

EC Number:

222-852-4

EC Name:

1,3-bis(isocyanatomethyl)benzene

Cas Number:

3634-83-1

Molecular formula:

C10H8N2O2

IUPAC Name:

1,3-bis(isocyanatomethyl)benzene

Test material form:

liquid

Details on test material:

Other name: XDI
Appearance: Colorless and transparent liquid, pungent odor
Storage conditions: Stored in a tight container at cool place (7.9°C to 11.8°C), protect from light, dehumidified
Stable under the storage conditions

Test animals

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Crl:CD(SD) [SPF]

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc.
- Age at study initiation: 11 weeks
- Weight at study initiation: 234.5 to 307.2 g.
- Fasting period before study: No
- Housing: individual housing in steel mesh cages (W29.1 × D 26.3 × H 18.0 cm) hung on a water flushing breeding rack (Toyo-Riko)
- Diet: pellet diet CRF-1 (Oriental Yeast), ad libitum
- Water: tap water, ad libitum
- Acclimation period: 7 days (following a quarantine period of 7 days)
The test facility obtained certificates of analyses on the contaminant levels for each lot of pellet diet, and confirmed that the levels were within the acceptable limits proposed by the Japan Experimental Animal Feed Association. The drinking water was analyzed for quality in April 2020 at another inspection agency, in accordance with the specifications of the Water Works Law. The drinking water was analyzed for bacteria (common bacteria and Escherichia coli) in May and June 2020 by the BSRC. The results of these analyses indicated that the levels of contaminants were within the acceptable ranges in the Tap Water Quality Standard.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.9 to 23.0
- Humidity (%): 43 to 56%
- Air changes (per hr): 12 times or more
- Photoperiod (hrs dark / hrs light):12/12 (light on: 7:00, light off: 19:00)

IN-LIFE DATES: From: May 18, 2020 To: June 9, 2020

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test substance was mixed with corn oil and it was administered to the animals once a day by gavage using a stomach tube and a disposable syringe.
At first, 100 mg/mL solution was prepared. A required amount of the test substance was accurately weighed into a measuring cylinder and mixed with an adequate amount of the vehicle. Then the vehicle was added up to the final volume. Dosing formulations of 50 and 25 mg/mL were prepared by diluting 100 mg/mL solution. The prepared dosing formulations were divided for daily use, and stored in the refrigerator until use [actual temperature: 4.0 to 8.1°C, duration of storage: from May 19, 2020 to June 8, 2020 (from the second day of preparation of dosing formulations to the final day of dosing)].

VEHICLE
- Justification for use and choice of vehicle: The substance is highly reactive in water, therefore no aqueous solution could be used.
- Concentration in vehicle: 25, 50 or 100 mg/mL
- Amount of vehicle: 4 mL/ kg bw
- Supplier and Lot no.: FUJI Film Wako Pure Chemical Corporation, Lot No. CAR2149

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability/homogeneity analysis: The 25 and 100 mg/mL dosing formulations were analyzed just after preparation, after 3 days of storage in a tight light-resistant container under refrigeration (acceptable range: 1 to 9°C) and subsequent 6 hours of storage in a tight light-resistant container at room temperature (acceptable range: 1 to 30°C). Remaining (ratio of each mean measured concentration after storage to those just after preparation) and relative standard deviation (RSD) were calculated from the measured concentration. When the remaining are within 100.0±10.0%, the test substance formulations would be judged to be stable. When the RSD are 5.0% or less, the test substance formulations would be judged to be homogeneous.

Concentration/homogeneity analysis: Concentrations of XDI in the dosing formulations were examined at the first and last preparations by the method established previously (Validation of Determination method of m-Xylylene diisocyanate in corn oil: Exp. No. J078 (575-012)). Whether each formulation have been appropriately prepared or not was judged according to the following criteria. The dosing formulations on the first preparation were prepared for concentration/homogeneity analysis, these formulations were not used for dosing.
Acceptance citerium vehicle: No interference peak should be detected at the retention time of XDI on the chromatogram. If the peak is detected, the peak area should be less than 10.0% of that of the standard solution for calibration curve (nominal concentration: 0.005 mg/mL).
Acceptence criteria test item formulations: The ratio to the nominal concentration should be within 100.0±10.0%. The relative standard deviation of the homogeneity analyses should be 5.0% or less.

Details on mating procedure:

Males and females were cohabited on one-on-one basis overnight until evidence of mating is confirmed. For female animals the day when sperm was confirmed in the vaginal smear at examination in the morning time was designated as Day 0 of gestation. Estrus cycles of all animals were examined for at least 7 days prior to mating, and those animals in a suitable condition for mating were subjected to the mating process.
Successfully copulated females were assigned to the test groups on the day of copulation using the system package software for safety study (LATOX-F/V5, FFC), on the basis of the body weight on Day 0 of gestation. Animals copulated on the same day were uniformaly assigned to the groups. The clinical signs were recorded daily during the mating period.

Duration of treatment / exposure:

From Day 5 to 19 of gestation

Frequency of treatment:

Once daily

Duration of test:

16 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Remarks:

Low dose group

Doses / concentrations 2

Dose / conc.:

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

Remarks:

Mid dose group

Doses / concentrations 3

Dose / conc.:

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

Remarks:

High dose group

No. of animals per sex per dose:

23 copulated females

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale:
In a dose range finding study for prenatal developmental toxicity study of m-xylylene diisocyanate in rats (dose levels: 0, 100, 300, 500 mg/kg bw/day, N=5), no dead dams were observed in any groups. In the 300 and 500 mg/kg bw/day groups, decreased food consumption values were observed from Day 5 of gestation (start dosing day) to Day 11 of gestation. Moreover, in the 300 and 500 mg/kg bw/day groups, white patches on the kidneys were observed at gross pathology. However, there were no effects on fetuses in any of the groups. The effects of test substance treatment on dams were slightly in the 300 mg/kg bw/day group, and more severe in the 500 mg/kg bw/day group.
From these results, the 400 mg/kg bw/day (intermediate dose between 300 and 500 mg/kg bw/day) was set as the high dose level, and 200 and 100 mg/kg bw/day were selected for middle and low dose levels, respectively, using a common ratio of 2.

Examinations

Maternal examinations:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least twice daily (before and after each administration) during the administration period and once daily during the rest of the experimental period.

BODY WEIGHT: Yes
- Time schedule for examinations: Animals were weighed on Days 0, 2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 of gestation.
Body weight gain during Day 0 to 5, 5 to 20 and 0 to 20 of gestation were calculated.

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- The amount of food including the feeder was measured on Days 0, 2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 of gestation. However, only the supplied food was measured on Day 0 of gestation, and only the remaining food on Day 20 of gestation. The mean daily food consumption was calculated using the weights of supplied and remained diets.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20 (by exsanguination from the abdominal aorta under isoflurane anesthesia)
- Gross macroscopy was performed on all surviving animals: the external surfaces and orifices were observed, and the organs and tissues in the abdominal, thoracic, pelvic and cranial cavities were examined macroscopically.
- The thyroid glands of all survival dams were collected and weighed. On the basis of the body weight on the day of necropsy, relative weights were calculated.
- Histopathology was performed on thyroid glands.

HORMONE ANALYSES: Yes
- Blood was collected from each animal at necropsy. TSH, T3 and T4 levels were determined by ELISA.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
The gravid uterus (including the uterine contents) was weighed. On the basis of the body weight on the day of necropsy, their relative weights were calculated. In addition, the ovaries and uterine contents were examined, and the number of corpora lutea graviditatis, number of implantations, number of live fetuses and number of resorbed and dead fetuses (number of early dead embryos: deciduoma, number of late dead embryos: morphologically indistinct dead embryos with placenta and amnion, number of dead fetuses: including macerated fetuses), based on the implantation rate, live fetus rate and resorbed and dead fetus rate were calculated. The placentas of dams with live fetuses were weighed after gross examination for anomalies. The mean placental weight for each sex per litter was calculated. The uterus of the dam which was not pregnant (control animal) was stained with 10 vol% ammonium sulfide solution to confirm absence of implantation sites.

Fetal examinations:

The anogenital distance (AGD) of each fetus was measured using digital caliper. The mean AGD per sex per litter was calculated. All live fetuses were examined externally, and the incidence of external abnormalities per litter in each litter was calculated. The sex of each fetus was determined, and the sex ratio in each litter was calculated. Each fetus was weighed individually, and the mean fetal weight per sex per litter was calculated.
Approximately half of the live fetuses of a litter were examined for internal organ defects. Their head and abdomen were microscopically examined according to the modified Wilson method and their thorax was examined according to Nishimura’s microscopic necropsy method.
The remaining half of the live fetuses of a litter were stained for skeletal anomalies according to the modified Dawson method (Alizarin red S stain). Abnormalities were classified as skeletal malformations and variations, and the degree of ossification (number of ossified bones in the cervical centrum, number of incompletely ossified and unossified sternebra, number of ossified bones in metacarpal, fore proximal phalanx, middle phalanx, distal phalanx, metatarsal, hind proximal phalanx, middle
phalanx and distal phalanx, number of ossified bones in sacrococcygeal vertebra and other regions with incomplete ossification or unossification).

Statistics:

The body weight, body weight gain, food consumption, organ weights (absolute and relative), hormones, number of corpora lutea graviditatis, number of implantations, number of live fetuses, number of resorbed and dead fetuses (number of implantation sites), AGD, fetal weight, placental weight and degree of ossification were analyzed by Bartlett’s test for equality of variance. When the Bartlett’s test showed homoscedasticity (not significantly different), the data were analyzed by Dunnett’s multiple comparison test to assess the statistical significance of difference between the control group and each test substance-treated group. When the Bartlett’s test showed heteroscedasticity (significantly different), the data were analyzed by the Steel’s test to assess the statistical significance of difference between the control group and each test substance-treated group.
The implantation rate, live fetus rate, resorbed and dead fetus rate, sex ratio, and incidences of external anomalies, visceral abnormalities, skeletal variations, skeletal malformations and incomplete ossification were analyzed by Steel’s test to assess the statistical significance of difference between the control group and each test substance-treated group.
The significance level of the Bartlett's test was two-sided 5%. The significance levels of the other tests were two-sided 5% and 1%.
No statistical tests were used for clinical signs and gross and histopathological findings.

Indices:

Implantation rate: (Number of implantations/number of corpora lutea graviditatis) × 100
Live fetus rate: (Number of live fetuses/number of implantations) × 100
Resorbed and dead fetus rate: (Number of dead embryos and fetuses/number of implantations) × 100
Incidence of external abnormalities: (Number of abnormal fetuses / number of fetuses observed) × 100
Sex ratio: (Surviving male fetuses / surviving male and female fetuses) × 100
Incidence of visceral abnormalities: (Number of abnormal fetuses / number of fetuses observed) × 100
Incidence of skeletal malformation: (Number of fetuses with malformation / number of fetuses observed) × 100
Incidence of skeletal variation: (Number of fetuses with variation / number of fetuses observed) × 100
Incidence of incomplete ossification: (Number of abnormal fetuses/ number of fetuses observed) × 100

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Irregular respiration and abnormal respiratory noise were observed sporadically in two dams in the 400 mg/kg bw/day group during the latter half of the gestation period.

Mortality:

no mortality observed

Description (incidence):

No animals died in any group.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In the 400 mg/kg bw/day group, the mean body weight on Day 20 of gestation was statistically significantly lower compared to the control group (-5%, p=< 0.05). The body weight gains from Day 5 to 20 of gestation and from Day 0 to 20 of gestation were significantly lower than those in the control group (-16% and -14%, respectively, both p=< 0.01). Moreover, in the 400 mg/kg bw/day group, the mean body weights on Days 6 and 7 were decreased from Day 5 of gestation (start day of administration), and a lower tendency of mean body weight was observed from Day 8 to 19 of gestation.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In the 200 and 400 mg/kg bw/day groups, the mean daily food consumption was significantly lower than that in the control group on Day 6 of gestation (Day 5 to 6 of gestation). In addition, in the 400 mg/kg bw/day group, significantly lower daily food consumption was observed from Day 7 to 12 and on Day 18 of gestation.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no statistically significant differences in the levels of T4, T3 and TSH between each treatment group and the control group. The results are summarized in a tabel below.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There were no statistically significant differences in the absolute and relative weights of thyroid glands and gravid uterus between treatment groups and control group.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

In the observation of placentas, enlarged placenta, white patch in the placenta and placenta accreta were observed in the control, 100 and 400 mg/kg bw/day groups, respectively. However, these findings were not considered to be treatment-related because each finding was observed in only one dam.

White patches on the kidneys were observed in 1/23 and 21/23 dams in the 200 and 400 mg/kg bw/day groups, respectively. Furthermore, in the 400 mg/kg bw/day group, atrophic thymus and wasting of whole body was observed in one dam. All other findings, brown patches on the lungs, hepatodiaphragmatic nodule of the liver and focal depression of the kidneys were observed sporadically in all groups. These findings were often observed in the rats of this strain, therefore, these were judged to be spontaneous occurring lesions.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

No abnormal findings were noted in the thyroid glands in any group.

Maternal developmental toxicity

Number of abortions:

no effects observed

Description (incidence and severity):

The Caesarean section data are summarized in a tabel below.

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

not examined

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

One female in the control group was found to be non-pregnant.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

body weight and weight gain

food consumption and compound intake

gross pathology

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Description (incidence and severity):

The Caesarean section data are summarized in a tabel below. There were no differences in average body weight of male and female pups between the control and exposed groups.

Reduction in number of live offspring:

not examined

Changes in sex ratio:

no effects observed

Description (incidence and severity):

The percentage males was 47.6% in the control group and 48.8%, 49.2% and 54.4% in the low, mid and high dose groups, respectively.

Changes in litter size and weights:

not examined

Changes in postnatal survival:

not examined

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

External abnormalities were noted in 0 (0.0%), 2 (0.6%), 0 (0.0%) and 0 (0.0%) fetuses in the control, 100, 200 and 400 mg/kg bw/day groups, respectively. There were no statistically significant differences in the incidences of fetuses with external abnormalities between each treatment group and control group. The findings, gastroschisis and acaudate, were observed in one fetus each at 100 mg/kg bw/day. However, these findings were not considered to be test substance treatment-related, because each finding was observed in only one fetus and not observed in the 200 and 400 mg/kg bw/day groups.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

The results of the skeletal examinations are summarized in tabular form and included as attachment.
Skeletal malformations were noted in 0 (0.0%), 1 (0.5%), 0 (0.0%) and 2 (1.2%) fetuses in the control, 100, 200 and 400 mg/kg bw/day groups, respectively. There were no statistically significant differences in the incidences of fetuses with skeletal malformations between each treatment group and control group. As the findings, sternoschisis was observed in the 100 mg/kg bw/day group, short rib and fused sternebra were observed in each one fetus of the 400 mg/kg bw/day groups.
Skeletal variations were noted in 8 (5.0%), 9 (4.9%), 13 (7.1%) and 8 (4.7%) fetuses in the control, 100, 200 and 400 mg/kg bw/day groups, respectively. There were no statistically significant differences in the incidences of fetuses with skeletal variations between each treatment group and control group. Findings included short supernumerary rib, wavy rib and lumbarization of sacral vertebra in the control or treatment groups, but there were no statistical significances in the incidences of these findings.
Retarded ossification was noted in 86 (57.3%), 89 (53.2%), 100 (53.9%) and 102 (57.1%) fetuses in the control, 100, 200 and 400 mg/kg bw/day groups, respectively. There were no statistically significant differences in the number of fetuses with retarded ossification or in the incidences of findings between each treatment group and control group. Findings included incomplete ossification of the frontal, incomplete ossification of the hyoid, unossified hyoid, incomplete ossification of the interparietal, incomplete ossification of the parietal, bipartite ossification of the sternebra, incomplete ossification of the cervical arch, bipartite ossification of the thoracic centrum, dumbbell ossification of the thoracic centrum, incomplete ossification of the thoracic centrum, unossified thoracic centrum, incomplete ossification of the lumbar arch, bipartite ossification of lumbar centrum, incomplete ossification of the lumbar centrum, incomplete ossification of the sacral arch, unossified sacral centrum, incomplete ossification of the ischium, incomplete ossification of pubis and unossified pubis.
There were no statistically significant differences in number of unossified or incomplete ossification of sternebrae, numbers of ossified metacarpal, metatarsal, fore/hind proximal, middle and distal phalanx, cervical vertebral centrum and sacrococcygeal vertebra between each treatment group and control group.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

The findings are summarized in tabular form and included as attachment.
Visceral abnormalities were noted in 14 (9.6%), 13 (7.8%), 14 (7.4%) and 18 (10.6%) fetuses in the control, 100, 200 and 400 mg/kg bw/day groups, respectively. There were no statistically significant differences in the incidences of fetuses with visceral abnormalities between each treatment group and control group. Findings included thymic remnant in the neck, persistent left umbilical artery, elongate innominate, malpositioned subclavian branch, retroesophageal subclavian, misshapen liver, dilated renal pelvis, small kidney and misshapen plate rugae in the control or treatment groups, but there were no statistical significance in the incidences of these findings.

Other effects:

no effects observed

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Remarks:

Development

Effect level:

>= 400 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed on development up to and including the highest dose tested (400 mg/kg bw/day)

Remarks on result:

other: Testing was done up to and including maternal toxic levels

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

Tabel: Hormone measurements on GD 20

Dose level (mg/kg bw/day)	T4 (ng/mL)	T3 (ng/mL)	TSH (ng/mL)
0	13.61 ± 5.00 [22]	0.397 ± 0.132N [20]	1.99 ± 0.47N [16]
100	13.08 ± 4.82 [23]	0.416 ± 0.219 [18]	2.91 ± 2.75 [15]
200	12.34 ± 6.83 [23]	0.340 ± 0.097 [20]	2.27 ± 0.97 [18]
400	12.15 ± 6.52 [22]	0.366 ± 0.157 [20]	2.82 ± 1.65 [20]

Mean ± S.D.

No significant difference from the control.

N: Non parametric analysis

Values in [ ] parentheses expresses number of animals used for the calculation in each parameters

 

Tabel: Caesarean section data

		Controls	100 mg/kg bw/day	200 mg/kg bw/day	400 mg/kg bw/day
No. of animals examined	Total	22	23	23	23
No. of dams with live fetuses	Total	22	23	23	23
No. of corpora lutea	Total (mean±SD)	358 (16.3±1.8)	359 (15.6±2.1)	376 (16.3±1.9)	381 (16.6±3.1)
No. of implantations	Total (mean ± SD)	335 (15.2±2.9)	343 (14.9±2.1)	372 (16.2±1.7)	363 (15.8±2.1)
No. of dead fetuses	Total (mean ± SD)	27 (1.2±1.3)	17 (0.7±0.9)	14 (0.6±0.9)	15 (0.7±0.8)
Early resorptions	Total (mean ± SD)	27 (1.2±1.3)	15 (0.7±0.7)	13 (0.6±0.9)	14 (0.6±0.7)
Late resorptions	Total (mean ± SD)	0	1 (0.0±0.2)	1 (0.0±0.2)	1 (0.0±0.2)
Dead fetuses	Total (mean ± SD)	0	1 (0.0±0.2)	0	0
No. of live fetuses	Total (mean ± SD)	308 (14.0±3.2)	326 (14.2±2.1)	358 (15.6±1.9)	348 15.1±2.0)
Sex ratio	Male:female (% males)	147:161 (47.6±11.2)	159:167 (48.8±15.5)	177:181 (49.2±13.4)	188:160 (54.4±11.7)
Body weight (g)	Males (mean ± SD)	3.79±0.30	3.80±0.29	3.82±0.26	3.61±0.41
Body weight (g)	Females (mean ± SD)	3.57±0.26	3.57±0.30	3.63±0.16	3.43±0.40
Placental weight (g)	Male (mean ± SD)	0.49±0.13	0.44±0.04	0.46±0.04	0.43±0.05#
Placental weight (g)	Female (mean ± SD)	0.46±0.12	0.42±0.03	0.43±0.03	0.41±0.05
Anogenital distance (mm)	Male (mean ± SD)	2.9±0.2	2.9±0.2	2.9±0.3	2.8±0.3
Anogenital distance (mm)	Female (mean ± SD)	1.2±0.2	1.2±0.2	1.2±0.2	1.2±0.2
No. of live fetuses with external anomalies	Total (%)	0 (0)	2 (0.6)	0 (0)	0 (0)

Significant difference from the control; # P ≤ 0.05 (Steel’s test)

Applicant's summary and conclusion

Conclusions:

Based on the results of a prenatal toxicity study, performed according to OECD guideline 414 and GLP principles, the maternal NOAEL was 100 mg/kg bw/day and the developmental NOAEL was at least 400 mg/kg bw/day, the highest dose tested.

Executive summary:

A prenatal toxicity study with exposure of rats via oral gavage was performed with XDI according to OECD guideline 414 and GLP principles. Based on the results of a dose range finder study, the dose levels were set at 100, 200 and 400 mg/kg bw/day. Corn oil was used as a vehicle, dose formulation analyses were included to verify correct dosing of the animals. The rats were dosed from GD 5 to 19, and sacrificed on GD20.

No mortality occurred during the study. Maternal toxicity was found in the mid and the high dose groups, and consisted of lower food consumption (mid dose: GD 5 -6, high dose group GD 5 to the end of the study). For the high dose group, a statistically significant decrease in body weight gain was found. No treatment related clinical signs were observed. At macroscopy white patches were found on the kidneys of animals dosed at 200 and 400 mg/kg bw/day. No effects were found in thyroids (weights and histopathology), or in the levels of thyroid hormones (T3, T4 and TSH). There were no test substance treatment-related effects on the sex ratio, body weights of live fetuses, anogenital distance (AGD), findings of external, visceral and skeletal examinations.

In conclusion, the maternal NOAEL was found to be 100 mg/kg bw/day and the developmental NOAEL was at least 400 mg/kg bw/day, the highest dose tested.