4-methyl-m-phenylene diisocyanate

Toxicity to reproduction

Administrative data

Endpoint:

two-generation reproductive toxicity

Remarks:

based on test type (migrated information)

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 416 GLP study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Deviations:

not applicable

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

m-tolylidene diisocyanate

EC Number:

247-722-4

EC Name:

m-tolylidene diisocyanate

Cas Number:

26471-62-5

Molecular formula:

C9 H6 N2 O2

IUPAC Name:

m-tolylidene diisocyanate

Details on test material:

80:20 % mixture of the 2,4- and 2,6-isomers.

Data on physical and chemical properties, eco-toxicity and toxicity can be used for read-across from 2,4-TDI to 2,6-TDI and mixed TDI isomers (i.e. 80/20, 65/35, 2,4/2,6 ratios). 2,4 TDI is the major component of the TDI mixed isomers and so has the major influence on their properties and effects. The reactivity of the 2,6-TDI isomer is somewhat less than that of 2,4-TDI but is of the same order of magnitude. It may therefore be concluded that the effects of 2,6-TDI will be similar to those of 2,4-TDI. This is in fact observed where there are overlapping data.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female Sprague-Dawley weanling rats F0 (28 animals/sex/group) were exposed to TDI vapour at different concentrations, 6 hours/day, 5 days/week, for 10 weeks. Animals were paired randomly within groups for 3 weeks to produce the F1 generation. Exposures of females continued through mating and the first 19 days of gestation and were discontinued from gestation day 20 through the fourth day postpartum. Exposures of females resumed on day 5 postpartum and continued through postnatal day 20. Exposures of F0 males were continuous from the mating period through delivery of the first F1 litters. At weaning, 28 weanlings/sex/group F1 were randomly selected to produce the F2 generation. F1 weanlings were exposed to the same TDI protocol as the F0 generation. In addition, 10 F1 weanlings/sex/group were necropsied for gross lesions. F0 males were necropsied following delivery of the first F1 litters. F0 females were necropsied after the F1 pups were weaned. Selected tissues from 10 F0 animals/sex/group in the high exposure and control groups were examined for histopathological lesions. Tissues from the upper respiratory tract from 10 animals/sex from the mid- and low-exposure groups also were examined for histopathological lesions. The selected F1 weanings were exposed to the same exposure concentration of TDI as their parents for 12 weeks. After their pre-breed exposure, F1 animals were paired as described above to produce the F2 generation. Mating, gestation, lactation, necropsy of the F1 parents and selected F2 weanlings and historic examination of selected F1 adults tissues were performed as described above except that no F2 animals were selected as parents. Remaining non-selected F1 and F2 pups at weaning were euthansised and discarded after the necropsy of the selected pups. Mating 1 male to 1 female.

Rats exposed to TDI vapour in 4320 litre chambers. Atmospheres monitored by paper tape devices based upon modified Marcali method.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: Countercurrent air stream

Details on exposure:

The route of exposure was by whole-body inhaltion of the vapours. TDI vapour was generated using a glass evaporator system. Temperature measurements were obtained from the inside surface of each evaporator during the exposure regimen. Throughout the study, TDI atmosphere were monitored by placing probes in the breathing zone of the animals approximately six times per each 6h exposure. Control chamber atomosphere was measured six times daily for the first 11 exposure days and once per day thereafter.

Details on mating procedure:

Each female F0 animal was mated with a single male from the same exposure group for 3 weeks, with exposure to TDI continuing throughout the mating period, 7 days/week. During the mating period, mating pairs remained together during the daily exposure periods.

Observations of vaginal sperm and/or dropped or vaginal copulation plug were considered evidence of successful mating. Once the animals mated, they were housed individually.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Two Autostep Isocyanate paper tape monitoring devices (GMD) System, Inc., Hendersonville, PA), one for 0.00, 0.02, 0.08, and one for 0.3 ppm were used to measure TDI concentrations in the exposure chamber atmospheres.

The 2,4- and 2,6-TDI isomer concentrations in the exposure chamber atmospheres were measured prior to the onset of the F0 exposure period and on exposure day 143. Samples were obtained and reverse-phase HPLC was used to separate and quantify the 2,4- and 2,6-isomers.

Duration of treatment / exposure:

Male and female Sprague-Dawley weanling rats F0 were exposed to TDI vapour at different concentrations, for 10 weeks, then paired randomly within groups for 3 weeks to produce the F1 generation. Exposures of females continued through mating and the first 19 days of gestation and were discontinued from gestation day 20 through the fourth day postpartum. Exposures of females resumed on day 5 postpartum and continued through postnatal day 20. Exposures of F0 males were continuous from the mating period through delivery of the first F1 litters. At weaning, 28 weanlings/sex/group were randomly selected to produce the F2 generation.

Frequency of treatment:

F0 parents exposed 6h/day, 5 days/week for 10 weeks; and then, during mating, 6h/day, 7 days/week until day 19 of gestation. Dams not exposed day 20-24; then exposed again 6h/day, 7 days/week to day 20 postnatal. At day 21 litters weaned. Parents for second generation selected and exposed 6h/day, 5 days/week for 12 weeks prior to mating. Exposure during mating and subsequently, as above.

Details on study schedule:

Male and female weanling rats (28/sex/group) were exposed to TDI concentrations of 0, 0.020, 0.080, and 0.30 ppm, 6 hours/day, 5 days/week, for 10 weeks. They then were paired randomly within groups for 3 weeks to produce the F1 generation. Exposures of females continued through mating and the first 19 days of gestation and were discontinued from gestation day 20 through the fourth day postpartum. Exposures of females resumed on day 5 postpartum and continued through postnatal day 20. Exposures of P0 males were continuous from the mating period through delivery of the first F1 litters.

At weaning, 28 weanlings/sex/group were randomly selected to produce the F2 generation. F1 weanlings were exposed to the same TDI protocol as the F0 generation. In addition, 10 F1 weanlings/sex/group were necropsied for gross lesions. F0 males were necropsied following delivery of the first F1 litters. F0 females were necropsied after the F1 pups were weaned. Selected tissues from 10 F0 animals/sex/group in the high exposure and control groups were examined for histopathological lesions. Tissues from the upper respiratory tract from 10 animals/sex from the mid- and low-exposure groups also were examined for histopathological lesions.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 0.02, 0.08, 0.30 ppm.
Basis:
other: by inhalation

No. of animals per sex per dose:

Twenty-eight pups/sex/group

Control animals:

yes, concurrent no treatment

Details on study design:

F0 and F1 parents and ten F1 and F2 weanlings/sex/group were necropsied, and adult reproductive organs, pituitary, liver, kidneys, and upper respiratory tract (target organs) were evaluated histologically in ten/sex/group.

Examinations

Parental animals: Observations and examinations:

Clinical signs of toxicity (nasal discharge in males and red-tinged fur in females) were observed in the high-exposure F0 group, but there were no effects on body weight. Histopathology revealed a significant increase in the incidence of rhinitis in the nasal turbinates of F0 animals (both sexes) exposed to 0.080 and 0.30 ppm and hyperplasia and dysplasia of the respiratory epithelium of F0 males at 0.30 ppm. The incidence of hyperplasia was significantly increased in F0 females at 0.30 ppm. There were no treatment-related gross lesions in F1 animals that were necropsied. F1 males had a significant increase in the incidence of rhinitis at all exposure concentrations; in females, this increase was apparent only at the two higher doses. In the high-exposure group (males), there was a significant increase in the incidence of submucosal lymphoid infiltrates in both the larynx and the trachea as well as a significant increase in the incidence of intracellular eosinophilic droplets. There were no treatment-related effects in the trachea or larynx of F1 females.

During the 12-week prebreed exposure of F1 animals, animals from the 0.30 ppm group exhibited reduced body weights (both sexes) and weight gain (males only). The only treatment-related clinical signs were observed in F1 females and included perinasal encrustation and red-tinged fur. F2 pup body weights and weight gain per litter were reduced at 0.080 and 0.30 ppm during lactation.

Oestrous cyclicity (parental animals):

Not applicable.

Sperm parameters (parental animals):

Not applicable.

Litter observations:

No effects.

Postmortem examinations (parental animals):

No effects.

Postmortem examinations (offspring):

Not applicable.

Statistics:

The unit of comparison was the male, the female or the litter. Results of the quantitative continuous variables e.g., body weights, food consumption, organ weights, etc. were intercomparted for the 3 treatment groups and one control group by use of Levene’s test for equal variances, analysis of variance (ANOVA) and t-tests. Nonparametric data were statistically evaluated using the Kruskal-Wallis test followed by the Mann-Whitney U-test for pairwise comparisons when appropriate. Frequency data such as the various indices were compared using the Fisher’s exact-test. For all statistical tests, the fiducial limit of 0.05 (two-tailed) was used as the criterion for statistical significance.

Reproductive indices:

The reproductive indices were calculated for F0 and F1 males and females for each breed (F0 to produced F1 litters and F1 to produce F2 litters).

a. Mating index (%) = Number of females with copulation plugs/Number of females cohabited x 100
b. Fecundity index (%) = Number of pregnancies/Number of plug-positive females x 100
c. Fertility index (female) (%) = Number of females pregnant/ Total number of females cohabitated x 100
d. Fertility index (male) (%) = Number of males shown to be fertile/Total number of males mated x 100
e. Gestational index = Number of females with live litters/Number of females pregnant
f. Live birth index = Number of live pups at birth/Total number of pups born
g. 4-Day survival index = Number of pups surviving 4-day (pre-cull)/Total number of live pups at birth
h. 7-Day survival index = Number of pups surviving 7-days/Total number of live pups at 4-days (post-cull)
i. 14-Day survival index = Number of pups surviving 14-days/Total number of live pups at 7-days (post-cull)
j. 21-Day survival index = Number of pups surviving 21-days/Total number of live pups at 14-days (post-cull)
k. Lactation index = Number of pups surviving 21 days/ Total number of live pups at 4-days (post-cull)

Offspring viability indices:

See above.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Details on results (P0)

Clinical signs of toxicity (nasal discharge in males and red-tinged fur in females) were observed in the high-exposure F0 group, but there were no effects on body weight. Histopathology revealed a significant increase in the incidence of rhinitis in the nasal turbinates of F0 animals (both sexes) exposed to 0.080 and 0.30 ppm and hyperplasia and dysplasia of the respiratory epithelium of F0 males at 0.30 ppm. The incidence of hyperplasia was significantly increased in F0 females at 0.30 ppm.

Effect levels (P0)

Key result

Dose descriptor:

NOAEC

Effect level:

0.08 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive performance

Results: P1 (second parental generation)

General toxicity (P1)

Body weight and weight changes:

effects observed, treatment-related

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

Details on results (F1)

There were no treatment-related gross lesions in F1 animals that were necropsied. F1 males had a significant increase in the incidence of rhinitis at all exposure concentrations; in females, this increase was apparent only at the two higher doses. In the high-exposure group (males), there was a significant increase in the incidence of submucosal lymphoid infiltrates in both the larynx and the trachea as well as a significant increase in the incidence of intracellular eosinophilic droplets. There were no treatment-related effects in the trachea or larynx of F1 females.

During the 12-week prebreed exposure of F1 animals, animals from the 0.30 ppm group exhibited reduced body weights (both sexes) and weight gain (males only). The only treatment-related clinical signs were observed in F1 females and included perinasal encrustation and red-tinged fur. F2 pup body weights and weight gain per litter were reduced at 0.080 and 0.30 ppm during lactation.

Effect levels (F1)

Key result

Dose descriptor:

NOAEC

Generation:

F1

Effect level:

0.3 ppm

Based on:

test mat.

Sex:

not specified

Basis for effect level:

body weight and weight gain

Results: F2 generation

Effect levels (F2)

Dose descriptor:

NOAEC

Generation:

F2

Effect level:

0.02 ppm

Based on:

test mat.

Sex:

not specified

Basis for effect level:

body weight and weight gain

Overall reproductive toxicity

Reproductive effects observed:

not specified