m-tolylidene diisocyanate

Respiratory sensitisation

Administrative data

Endpoint:

respiratory sensitisation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Assessment of respiratory hypersensitivity in guinea pigs sensitized to toluene diisocyanate: a comparison of sensitization protocols

Author:

Pauluhn J & Mohr U

Year:

1998

Bibliographic source:

Inhal.Toxicol. 10: 131-54

Materials and methods

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:

C9H6N2O2

IUPAC Name:

2,4-diisocyanato-1-methylbenzene, 2,6-diisocyanato-1-methylbenzene

Details on test material:

Toluene Diisocyanate, Desmodur T80, an 80:20 mixture of the 2,4 and 2,6 isomers (purity >99.9%)

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Housing: Standard housing in groups of 8 or more animals.

Test system

Route of induction exposure:

intradermal

Route of challenge exposure:

inhalation

Vehicle:

corn oil

Concentration:

0.3 % TDI in 100 µL corn oil (intradermal)
0, 3.8, 11, 26, 46, and 51 mg/m³

Details on study design:

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 5 (inhalative), 6 (inhalative + i.d. injection)
- Exposure period: A single intradermal injection (0.3 % TDI in 100 µL corn oil) and repeated inhalation exposure (3 h /day for 5 consecutive days).
- Control group: One group of animals was sensitized by intradermal injection only. Naive and polyisocyanate resin (50 and 250 mg dust/m³ air) sensitized animals served as controls.
- Frequency of applications: daily
- Duration: 3 h
- Concentrations: 0, 3.8, 11, 26, 46, and 51 mg/m³ air.

B. CHALLENGE EXPOSURE
- Concentrations: ~0.5 mg/m³

OTHER:
Three weeks after the first encounter with the inducing agent, animals were challenged with the free TDI (~0.5 mg/m³), and 1 week later with the TDI-protein conjugate. Animals induced with the polyisocyanate resin were similarly challenged with the free chemical (ca 50 mg/m³) and TDI- as well as resin-protein conjugates.

Results and discussion

Results:

Two groups were exposed by inhalation of 136 or 220 mg TDI/m³ for 15 min. They experienced bradypnoea on the day of exposure.
The bradypnoea experienced by the animals exposed to 3.8 mg TDI/m³ was accompanied by a laboured/irregular breathing pattern and breathing sounds at higher concentrations.
Those exposed to >11 mg TDI/m³ displayed reduced motility.
The animals sensitized by a single, brief, high-level exposure appeared to be mildly more responsive to TDI challenge than those in the other groups.
The guinea pigs receiving the i.d. and the inhalation exposure, showed a longer, more intense response to TDI-GPSA, than those which received only the injection.
The guinea pigs were sacrificed 1 day after the conjugate challenge.Tissue sections from TDI exposed animals showed the presence of epithelial disruption, pulmonary inflammation and activation of the lung associated lymph nodes (LALN). Inflammation was characterised by infiltration of eosinophils and polymorphonuclear leucocytes. Histological analysis of the lungs, and LALN, revealed an association of the influx of polymorphonuclear and eosinophilic granulocytes, and the TDI level at induction. The 15 min exposure to 220 mg TDI/m³ caused a statistically significant increase of polymorphonuclear and eosinophilic granulocytes. Infiltrations of these granulocytes were seen in the tracheae of the animals exposed to TDI by inhalation, with the exception of those receiving 138 mg TDI/m³ for 15 min.
The guinea pigs exposed to the polyisocyanate resin had IgG1 antibodies to both TDI-GPSA and resin-GPSA; apparently cross-reactivity.

Any other information on results incl. tables

The inhalation challenge with TDI failed to elicit pulmonary responses, while during the TDI-protein conjugate challenge characteristic changes in breathing patterns occurred. Animals sensitized to higher concentrations of TDI by inhalation displayed increased responsiveness to ACh and an influx of eosinophilic granulocytes in airways or lung-associated lymph nodes (LALN). Guinea pigs of the TDI resin groups did not respond to any challenge, nor was there any influx of eosinophils in airways or LALN; that is, they were indistinguishable from naive controls. IgG1 antibodies were observed in all groups receiving TDI or TDI resin.

In summary, it was demonstrated that the intradermal injection, in addition to the 5 x 3 h inhalation exposures, did not increase markedly the sensitivity of this animal model. However, the outcome of the test appeared to be less dependent on the exposure concentration used for sensitization of the animals when the combined protocol was used. Therefore, it is believed that the combined induction protocol improves the robustness of this animal model. Accordingly, in order to classify a low-molecular-weight substance as a respiratory sensitizer, a triad of responses should be considered: (1) positive respiratory response upon challenge with the hapten, and if negative, also challenge with the conjugate of the hapten, (2) an influx of eosinophilic granulocytes, and (3) increased specific IgG1 response.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met