Registration Dossier

Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Equivalent or similar to OECD Guideline 414 GLP study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988
Report Date:
1988

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
yes
Principles of method if other than guideline:
Overall method conforms to OECD test guideline 414, except maternal body weight measured more frequently at gestation days 0, 6, 9, 12, 16 and 21.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Toluene diisocynate
- Molecular formula (if other than submission substance): Benzene, 2,4- or 2,6-diisocyanateo-1-methyl; CH3C6H3 (NCO)2]
- Substance type: diisocynate
- Physical state: liquid
- Analytical purity: approximately 99%
- Impurities (identity and concentrations): no
- Composition of test material, percentage of components: 80%:20% mixture of the 2,4-TDI and 2,6-TDI
- Isomers composition: 80% 2,4- and 20% 2,6- isomers
- Lot/batch No.: 2,4-TDI and 2,6- TDI (CAS No. 584-84-9 and 91-08-7, respectively)
- Stability under test conditions: Stable, no significant compositional changes occurred while the study progressed and the test material remained approximately 79% 2,4- and 20% 2,6-TDI throughout the study.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Kingston, NY., USA
- Age at study initiation: Males 11 weeks and females 10 weeks old.
- Weight at study initiation: 220.6-24.2 gd 0, females.
- Fasting period before study: No
- Housing: Animals during acclimation were housed separately by sex, two-three per cage in stainless-steel wire-mesh cages. During mating, rats were housed 1:1 (on male: one female) in stainless steel wire mesh cages. Plug-positive females were individually housed for the duration of the study (except during exposure). For exposures, plug-positive females were transferred to stainless steel wire-mesh exposure cage.
- Diet (e.g. ad libitum): Food (chow) was available ad libitum except during exposures.
- Water (e.g. ad libitum): Tap water was available ad libitum except during exposures.
- Acclimation period: Two weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): measured but ranges not given
- Humidity (%):measured but ranges not given
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12hrs dark / 12 hrs light.

IN-LIFE DATES: From: 29 March 1987 To: 20-22 April 1987.

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus:Exposure chamber
- Method of holding animals in test chamber: The animals were exposed to the test material in cages placed in the chamber.
- Temperature and humidity in air chamber: Temperature (22.6-23.9 °C) and relative humidity (50.1-54.4%).
- Air flow rate: approximately 1000-1500L/minute with a t99 (theoretically-derived time required for the chamber to reach 99% of the equilibrium concentration) of approximately 20 minutes.
- Air change rate: at least 14 air changes/h.


TEST ATMOSPHERE
- Brief description of analytical method used: liquid TDI was metered from a syringe pump into a heated glass evaporator. The temperature in the evaporator was monitored and maintained at the lowest level sufficient to vaporise the liquid (46 - 60°C). The resultant vapour was carried into the chamber (4320 liter chambers) by dilution air stream. Each chamber atmosphere was analysed for TDI approximately six times during each 6-hour exposure. Daily nominal concentrations and chamber airflow during the exposure period were calculated for each chamber. Chamber concentrations were monitored via Autostep Portable Monitors. In addition, chamber atmosphere samples were drawn through midget impingers and samples measured via UV.

VEHICLE (if applicable)
- Vehicle: Countercurrent air stream
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
To determine appropriate target concentrations of TDI for the definitive study (this study), a range-finding study was performed following the same study design in the definitive study, except eight inseminated females/group were employed. The concentrations were 0.00, 0.1, 0.50 and 1.0 ppm and the dams were terminated after the last exposure on gd 15. At termination, immediately after the last exposure, the dams were anesthetised with methoxyflurane (Metofan, Pittman Moore) and arterial blood was removed from the abdominal aorta into arterial blood samples containing heparin as an anticoagulant and analysed by Corning 170 Blood Gas analyser, Corning NY. Blood samples were analysed for pO2, pCO2 and pH and bicarbonate calculated using (Corning 170 Blood Gas analyser, Corning NY).

The dams were examined for body weight, gravid uterine weight, liver weight, number of ovarian corpora lutea, number of uterine implantation sites (total early and late absorptions and dead implants and live implants.

At 1.0 ppm: maternal body weights, weight changes, and liver weights (absolute but not relative) were profoundly and significantly reduced. Audible respiration and nasal discharge were observed; stomach and intestines were gas filled and adrenal glands were enlarged.

These were no effects on gestational parameters. The maternal blood gas results include the statistically significant changes at 1.0 ppm.

Based on these results 1.0 ppm was deemed too toxic for use in the definitive study. Therefore, the target exposure concentrations for the definitive study were 0.00, 0.02, 0.10 and 0.50 ppm.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: 3 days (maximum)
- Further matings after two unsuccessful attempts: no
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
Duration of treatment / exposure:
Exposures were for 6 hours/day, gestation day 6-15.
Frequency of treatment:
6 hours per day
Duration of test:
21 days (days 0-21 of gestation)
Doses / concentrations
Remarks:
Doses / Concentrations:
Target concentrations: 0.0, 0.02, 0.10, 0.50 ppm (The mean analytical concentrations: 0,00, 0.21±0.0018, 0.12±0,017 and 0.48±0.038 ppm)
Basis:
other: Target and analytical concentrations
No. of animals per sex per dose:
25 Pregnant females rats/group/dose level
Control animals:
yes, sham-exposed

Examinations

Maternal examinations:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Maternal clinical signs were taken daily.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were measured on gestation day 0, 6, 9, 12, 16, and 21.

FOOD CONSUMPTION: Yes
- Time schedule for examinations: - Food consumption were measured every 3 days.

WATER CONSUMPTION: Yes
- Time schedule for examinations: - Water consumption were measured every 3 days.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: yes
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes:
All live fetuses were anesthetised by hypothermia, and were weighed, sexed and examined for external malformations including cleft palate, and variations.

- Soft tissue examinations: Yes:
Approximately ½ of the live fetuses in each litter were examined for thoracic and abdominal visceral abnormalities.

- Skeletal examinations: Yes:
Intact fetuses in each litter were eviscerated, fixed in ethanol, and then processed for skeletal staining and examined for skeletal malformations and variations.

- Head examinations: Yes:
The fetuses examined viscerally were decapitated and their heads fixed in Bouin's solution for examination of craniofacial structures.
Statistics:
Quantitative continuous variables were intercompared via Levene's test, ANOVA, and T-tests with Bonferroni probabilities. Nonparametric data were analyzed using the Kruskal-Wallis test followed by the Mann-Whitney U test. Incidence data were compared using Fisher's Exact Test. The fiducial limit of 0.05 (two-tailed) was used as the criterion for significance.
Indices:
Not applicable.
Historical control data:
Not applicable.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Maternal weight gain was significantly depressed over the exposure period for 0.5 ppm group. Significant body weight reduction, significant body weight gain reduction and significantly reduced food consumption.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEC
Effect level:
0.1 ppm
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
0.1 ppm
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
No embryotoxicity or teratogenicity was observed at any exposure concentration employed.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

No deaths in dams. No significant differences in the number pregnant/dose level, number of dams aborting, pre- and post-implantation loss, number of corpora lutea, and number of resorptions. Number of total implants/litter and number of viable implants reduced at 0.02 ppm.

Maternal weight gain was significantly depressed over the exposure period for 0.5 ppm group. Maternal weight gain was significantly reduced early in the exposure period, gd 6-9, at 0.02, 0.1. Maternal food consumption was reduced at the high dose from exposure day 9 onward. In addition, food consumption was reduced at 0.02 ppm for gd 18-21 due to the dam with one fully resorbed litter eating at a nonpregnant rate in this group.

Treatment-related clinical signs of toxicity were limited to audible respiration in dams at 0.5 ppm and red nasal discharge at 0.02, 0.1, and 0.5 ppm.

No differences in maternal gross observations at necropsy. No differences in gravid uterine weights, or body weight change was observed among the groups. Hydronephrosis, a typical finding in CD® rats was observed in 2 dams at 0.1 and 1 dam at 0.5 ppm.

No significant differences in litter size and weights, number of viable fetuses, or sex ratio. Increased incidence of poorly ossified cervical centrum 5 at 0.5 ppm ( exhibited a statistically significant increase relative to controls) indicating minimal fetotoxicity or this variation could be described as a common rat skeletal variation. The NOAEL for maternal and developmental toxicity is 0.1 ppm.

Applicant's summary and conclusion

Conclusions:
No embryotoxicity or teratogenicity was observed at any exposure concentration employed. Exposure to toluene diisocyanate vapor by inhalation
during organogenesis in rats resulted in maternal toxicity and minimal fetotoxicity at 0.50 ppm. The NOAEL for maternal and developmental toxicity was 0.10 ppm.