3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate homopolymer, isocyanurate type

Endpoint summary

Description of key information

3 -Isocyanatomethyl-3,5,5 -trimethylcyclohexylisocyanate homopolymer, isocyanurate type (IPDI homopolymer) is skin sensitizing in a guinea pig maximization test (Notox B.V., 2004) and a LLNA (Vohr_2003).

Under the condition of the animal study (Bayer AG, 1996) the test item does not induce respiratory sensitization in guinea pigs.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-07-15 - 2003-03-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

yes

Remarks:

- modified LLNA (IMDS): Measurement of cell counts instead of radioactive labeling. In addition, measurements of ear swelling and ear weights were done to discriminate the irritating potential from the sensitizing potential of the test substance.

Principles of method if other than guideline:

Modified LLNA (IMDS; Integrated Model for the Differentiation of Skin Reactions). Modifications are authorized in the OECD TG 429 and the Note of
Guidance SWP/ 2145/00 of the CPMP (2001). Information on validation of IMDS and scientific justification is given in: Vohr HW et al., Arch. Toxicol.,
73, 501-509 (2000); Ehling G et al., Toxicology 212, 60-68 and 69-79 (2005).

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

NMRI

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan-Winkelmann GmbH, Borchen, Germany
- Strain: Hsd Win: NMRI
- Age at study initiation: no data
- Weight at study initiation: no data
- Housing: individual
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+/- 2
- Humidity (%): 40 - 70
- Air changes (per hr): about 10
- Photoperiod (hrs dark/ hrs light): 12/12

Vehicle:

dimethylformamide

Remarks:

The stability of the test item in the vehicle was analytically verified for up to 2 hours.

Concentration:

0, 3, 10, 30%

No. of animals per dose:

6

Details on study design:

TREATMENT PREPARATION AND ADMINISTRATION:
The test item was formulated immediately before each administration in dimethylformamide. The test item in the formulation was applied
epicutaneously onto the dorsal part of both ears of the animals. This treatment was repeated on three consecutive days (d0, d1 and d2). The volume
administered was 25µl/ear.
The animals were anaesthetized by inhalation of carbon dioxide and sacrificed one day after the last application (d3). The appropriate organs were
then removed. Lymphatic organs (the auricular lymph nodes) were transferred into physiiological saline (PBS).
Investigations:
- weight of lymph nodes
- cell counts in lymph nodes
- stimulation index is calculated by dividing the absolute number of weight or cell counts of the substance treated lymph nodes by the vehicle treated ones.
- ear swelling
- ear weight

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

When it was statistically reasonable, the values from treated groups were compared with those from the control group(s; vehicle) by a the Mann-
Whitney (Ann. Math. Stat. 18, 1947, 50-60) or the Wilcoxon (Biometrics 1, 1945, 80-83) significance test. at significance levels of 5%. Outlying values
in the LN weights were eliminated at a probability level of 99% by Nalimov's method (Statistik für naturwissenschaftliche Berufe, 1982, 88-89). In
addition, for the LLNA/IMDS the smallest significant differentes in the means were calculated by Scheffe's method (Biometrica 40, 1953, 87-104),
which according to Sachs (Angewandte Statistik 6th and 10th edition, Springer Verlag, Berlin, 1978/2002 ) can be used for both equal and unequal
sample sizes.

Positive control results:

Performed in 2002. The "positive level" which is 1.3 for cell counts has been statistically significant exceeded in the highest dose group (30%).
(Cell index/concentration: 0.88 / 3%; 1.13/ 10%; 1.77/ 30%)

Parameter:

SI

Remarks on result:

other: see Remark

Remarks:

The "positive level" which is 1.3 for cell counts has been exceeded in all dose groups, but the increase was only statistifically significant in the lowest dose group (3%). Cell count index = 2.29 (3%) / 1.43 (10%) / 1.68 (30%); test substance: 70 % solution in 1-Methoxypropylacetate-2/Xylol (1:1)

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: modified LLNA; measurement of cell counts instead of radioactive labeling

Compared to vehicle-treated animals, there was no increase regarding weight of the draining lymph nodes in all dose groups (weight index = 1.16 (3%) / 1.14 (10%) / 1.26 (30%)). The "positive level" of ear swelling which is 2 x 10exp-2 mm increase has not been reached or exceeded in any dose group. A slight significant increase compared to vehicle treated animals regarding ear swelling was detected in the highest dose group. No increase in the ear weights were observed in any dose group. (ear swelling - day 0 = 18.67 (0%) / 18.00 (3%) / 18.75 (10%) / 18.17 (30%); - day 3 = 18.17 (0%) / 18.25 (3%) / 18.92 (10%) / 19.50 (30%); ear weight - day 3 = 11.53 (0%) / 11.33 (3%) / 11.58 (10%) / 11.68 (30%))

Conclusions:

The results show that the test item (Desmodur Z 4470 MPA/X) has a slight irritating and a sensitizing potential in mice after dermal application.

Executive summary:

A modified LLNA (IMDS; OECD TG 429) was performed on 6 female NMRI mice per dose group using test item concentrations of 0% (vehicle control), 3%, 10% and 30%.

 

There was no increase compared to control animals regarding weight of the draining lymph nodes in all dose groups. Compared to vehicle treated animals the cell counts exceeded the "positive levels" defined for this assay in all dose groups, but only in the lowest group the increase was statistically significant. A slight significant increase compared to vehicle treated animals regarding ear swelling was detected in the highest dose group. No increase was determined for the ear weights in any dose group.

Under the conditions of this study the test item IPDI homopolymer has a slight irritating and a sensitizing potential in mice after dermal application.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-11-27 - 2004-03-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study; GLP study without deviations

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 406 (1992)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Directive 96/54/EC, B.6

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS 870.2600 (2003)

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

This skin sensitization test according to OECD 406 has already excisted since 2004 and is sufficient for evaluation of the skin sensitisation potential of the test substance.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

- Strain: Dunkin Hartley (SPF quality)
- Source: Charles River Deutschland, Kisslegg (Germany)
- Sex: female
- Age: approx. 6 weeks
- Weight at study initiation: 431 +/- 24 g
- Controls: 5 females (440 +/- 50 g); treatment: vehicle

Route:

intradermal and epicutaneous

Vehicle:

other: corn oil (intracutaneous) / acetone (epicutaneous)

Concentration / amount:

1st application: Induction 50 % intracutaneous
2nd application: Induction 100 % occlusive epicutaneous
3rd application: Challenge 50 % occlusive epicutaneous

Route:

epicutaneous, occlusive

Vehicle:

other: corn oil (intracutaneous) / acetone (epicutaneous)

Concentration / amount:

1st application: Induction 50 % intracutaneous
2nd application: Induction 100 % occlusive epicutaneous
3rd application: Challenge 50 % occlusive epicutaneous

No. of animals per dose:

10 females (test) / 5 females (control)

Details on study design:

ADMINISTRATION/EXPOSURE 
- Preparation of test substance for induction: Within 4 hours prior to  treatment, homogeneous preparation with vehicle
- Induction schedule:  Day 1: Injections,  Day 3: Assessment for dermal irritation,  Day 8: 48 hours occlusive patch with 0.5 ml of 100 % test 
substance on  clipped injection sites (control animals: vehicle),  Day 10: Removal of patch and residual test substance (sticking, thus  requiring 
soaking with water and pulling out hairs), assessment for  dermal irritation
- Injection details: 0.1 ml each at 6 sites in clipped scapular region:  2 x Freund's Complete Adjuvant (FCA) / water for injection (50:50),   
2 x test substance 50 % in vehicle,  2 x test substance 50 % in FCA, pairwise administration of each solution / suspension, symmetrical to  midline and from cranial to caudal, controls: vehicle instead of test substance
- Challenge schedule:  Day 21: Two 24 hours occlusive patches (each 0.10 ml) on one clipped  flank with     
(a) 50 % test substance and  (b) vehicle alone,  Day 22: Removal of patches and residual test substance,  Days 23 and 24: Assessment for challenge
reaction 24 and 48 hours after  patch removal
- Rechallenge: On day 28, similar to first challenge but on other flank
- Positive control: alpha-hexylcinnamic aldehyde (tech. 85 %) (not more  than 6 months previously)

EXAMINATIONS
- Grading system: Irritation: Draize scores (0 / 1 / 2 / 3 / 4 each for erythema + eschar  and for edema)   
- Challenge:   0 = no visible change,   1 = discrete or patchy erythema,   2 = moderate and confluent erythema,   3 = moderate erythema and swelling,   4 = intense erythema and swelling  
 Animals with any skin reaction more severe or more persistent than  observed in the control = sensitized   
Evaluation of sensitization rate (% animals sensitized) according to  current version of 67/548/EEC adaptations and OECD system (1998)
- Pilot study: Range finding: mild to moderate (for induction) and  non-irritant (for challenge) concentrations,   
Concentration series 100 %, 50 %, 20 %, 10 %, 5 %, 2 %, 1 % and so on  as far down as necessary   
A) Intracuteaneous: Series of 4 concentrations, 2 concentrations per  animal, duplicate 0.1 ml injections per concentration in clipped scapular  region, assessment 24 and 48 hours after treatment   
B) Epicutaneous: Initial test with undiluted material in 2 animals  followed by a series of 4 concentrations, 2 concentrations per animal,  0.5 ml per 
concentration in 24 hours occlusive patch on clipped flank,  assessment 24 and 48 hours after exposure

Challenge controls:

Treatment: vehicle

Positive control substance(s):

yes

Remarks:

alpha-hexylcinnamic aldehyde (tech. 85 %)

Positive control results:

The skin reactions observed in six experimental animals in response to the 20 % test substance (= alpha-hexylcinnamic aldehyde) concentration in
the challenge phase were considered indicative of sensitisation, based on the absence of any response in the control animals. These results lead to a sensitisation rate of 60 per cent to the 20 % concentration.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50 % test substance

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

see below

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 50 % test substance. No with. + reactions: 8.0. Total no. in groups: 10.0. Clinical observations: see below.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50 % test substance

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

see below

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 50 % test substance. No with. + reactions: 8.0. Total no. in groups: 10.0. Clinical observations: see below.

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

50 % test substance

No. with + reactions:

6

Total no. in group:

10

Clinical observations:

see below

Remarks on result:

other: Reading: rechallenge. . Hours after challenge: 24.0. Group: test group. Dose level: 50 % test substance. No with. + reactions: 6.0. Total no. in groups: 10.0. Clinical observations: see below.

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

50 % test substance

No. with + reactions:

2

Total no. in group:

10

Clinical observations:

see below

Remarks on result:

other: Reading: rechallenge. . Hours after challenge: 48.0. Group: test group. Dose level: 50 % test substance. No with. + reactions: 2.0. Total no. in groups: 10.0. Clinical observations: see below.

no remarks

Conclusions:

In the main study, ten experimental animals were intradermally injected with a 50 % concentration of test substance and epidermally exposed to a
100 % concentration. Both concentration were the maximal irritant concentrations for induction. Five control animals were similarly treated, but with
vehicle alone. Two weeks after the epidermal application all animals were challenged with a 50 % test substance concentration, which was the maximal concentration non irritant for challenge and the vehicle. A second challenge was performed one week later with the test concentration 50 % and
vehicle.
The skin reactions observed in response to 50% test substance concentration in eight (of ten) experimental animals in the first
challenge phase and in six (of ten) in the second challenge phase were considered indicative of sensitisation, based on the absence of any response
in the control animals. Therefore, IPDI homopolymer should be classified as contact sensitizer.

Executive summary:

The skin sensitization properties of IPDI homopolymer (approx. 70% in Solvesso 100) were conducted in a guinea pig maximization test according to OECD 406 in compliance with Good Laboratory Practice regulations.

The test substance concentrations selected for the main study were based on the result of a preliminary study. The preliminary study was performed using Solvesso 100 as vehicle. Since treatment of the animals with this vehicle showed technical problems and resulted in necrosis, other vehicles were selected and the preliminary irritation study was repeated. Based on the results of this study, the test substance concentrations selected for the main study were 50% concentration for the intradermal induction and a 100% concentration for the epidermal induction exposure, which were the maximal irritant concentrations for induction. A 50% test substance concentration, which was the maximal concentration non irritant for challenge, was selected for the challenge phase.

In the main study, IPDI homopolymer (approx. 70% in Solvesso 100) was administered at a concentration of 50 % intradermally (in corn oil) and 100 % epidermally to 10 female guinea pigs. Five control females were similarly treated, but with vehicle alone (corn oil for injection, acetone for epidermal exposure). Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle. A second challenge was performed one week later with the test substance concentration 50% and the vehicle.

Sensitisation was observed in 8 of 10 animals in the first challenge phase using a challenge concentration of 50 % test substance. In the second challenge phase with test substance concentration of 50 % six of ten animals were positive. No skin reactions were evident in the control animals. The second challenge confirmed that the skin reactions, as seen after the first challenge, were caused by the test substance and not by the vehicle. Therefore, the skin reactions observed in response to a 50% test substance concentrations in eight (of the ten) experimental animals in the first challenge phase were considered indicative of sensitisation, based on the absence of any response in the control animals.

Based on these results and according to the OECD Classification System, IPDI homopolymer should be classified as contact sensitizer.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The skin sensitization properties of 3 -isocyanatomethyl-3,5,5 -trimethylcyclohexylisocyanate homopolymer, isocyanurate type (IPDI homopolymer, tested as a 70% solution in Solvesso 100) were conducted in a guinea pig maximization test according to OECD 406 in compliance with Good Laboratory Practice regulations (Notox B.V., 2004). The test substance was administered at a concentration of 50 % intradermally (in corn oil) and 100 % epidermally to 10 female guinea pigs. Sensitisation was observed in 8 of 10 animals in the first challenge phase using a challenge concentration of 50 % test substance. In the second challenge phase with test substance concentration of 50 % six of ten animals were positive. Based on these results and according to the OECD Classification System, IPDI homopolymer should be classified as contact sensitizer.

A modified LLNA (IMDS; OECD TG 429) was performed on 6 female NMRI mice per dose group using test item (IPDI homopolymer, tested as a 70% solution in 1-Methoxypropylacetate-2/Xylol (1:1)) in concentrations of 0% (vehicle control), 3%, 10% and 30% (Vohr, 2003).

There was no increase compared to control animals regarding weight of the draining lymph nodes in all dose groups. Compared to vehicle treated animals the cell counts exceeded the "positive levels" defined for this assay in all dose groups, but only in the lowest group the increase was statistically significant. A slight significant increase compared to vehicle treated animals regarding ear swelling was detected in the highest dose group. No increase was determined for the ear weights in any dose group.

Under the conditions of this study the test item IPDI homopolymer has a slight irritating and a sensitizing potential in mice after dermal application.

Justification for selection of skin sensitisation endpoint:
There are two skin sensitization tests according to OECD 406 (Notox B.V., 2004) and OECD 429 (Vohr, 2003) available. Both studies are valid without restrictions (Klimisch score 1). Therefore, both studies are selected.

Respiratory sensitisation

Link to relevant study records

Reference

Endpoint:

respiratory sensitisation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-04-03 - 1995-05-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: exposure criteria of OECD 403 and EC Guideline 892/69/EEC (1992) were fullfilled

Qualifier:

equivalent or similar to guideline

Guideline:

other: exposure criteria of OECD 403 and EC Guideline 892/69/EEC (1992) were fullfilled

GLP compliance:

yes

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS:
- Strain: DHPW (Dunkin-Hartley Pirbright-White) strain from the Charles River [Crl:(HA)BR]
- Sex: female
- Source: Sulzfeld, Germany
- Age: ca. 2 weeks
- Weight at study initiation:
- pre-experimental treatment of animals and animal housing: animals were acclimatized for at least 5 days before use;before start of experiment
health status of each animal was assessed; animals were assigned to exposure gruops at random; room temperature: 22 °C (+/- 2°C);
humidity: appr. 50%; dark/light: 12h/12h (14 watt/m2); air-exchange: appr. 10-fold/h; diet: Altromin 3022 (Altromin GmbH, Lage);
tap-water ad libitum

Route of induction exposure:

other: intradermal or inhalation

Route of challenge exposure:

other: nose only inhalation of aerosol

Vehicle:

other: intradermal: aceton; inhalation: unchanged (no vehicle)

Concentration:

see: "Details on study design"

No. of animals per dose:

8 treated (intradermal and inhalation)
8 vehicle (control

Details on study design:

STUDY DESIGN:
Groups of eight female guinea-pigs were intradermally induced once per day on days 0, 2, and 4 (injection volume: 50 µl; 5% solution in aceton) and
one additional group of animals was exposed for five consecutive days by inhalation (duration of exposure per day: 3 hrs/day) to 147 mg/m3
IPDI-homopolymer dust (solid aerosol). The aerosolized test item proved to be of adequate respirability (MMAD approximately 2.1 µm, GSD ca. 1.8;
relative mass of particle <= 3 µm approximately 75%). Eight female controls received the vehicle alone (acetone intradermally) under otherwise
identical conditions. During the recovery period (starting on day 21) a IPDI-challenge (mean concentration: 48 mg/m3 air) was performed (challenge duration: 30 min) which was followed (one day after hapten challenge) by an acetylcholine bronchoprovocation challenge (ramped
concentrations).
Following day 28 all guinea pigs were challenged again with the guinea pig serum albumin (GPSA) conjugate of the hapten (mean concentration:
49 mg/m3 air).
During and after challenge exposures immediate-onset respiratory reactions were evaluated by measurement of respiratory rate, tidal volume,
respiratory minute volume, inspiratory and expiratory times, and peak expiratory flow rate. Additional parameters were derived mathematically.
One day thereafter, animals were sacrificed, the lungs, including trachea and lung associated lymph nodes, were examined histopathologically. The weight of the exised lungs was determined. At sacrifice blood was sampled for serological examinations.

Challenge controls:

Treatment: vehicle

Positive control substance(s):

trimellitic anhydride (TMA)

Negative control substance(s):

other: vehicle (acetone)

Results:

Following induction, mild skin reactions occured which appeared to be related to the vehicle used (acetone). During or following hapten, ACh or conjungate-challenges, the incidence of immediate-onset respiratory reactions were roughly the same in all groups. No deaths or stereotypic anaphylactic reactions were observed during challenge, and no clinical signs, conclusive changes in body weight or specific abnormalities were observed at necropsy. The histopathological investigations were unobstructive, i.e., there was no evidence of a specific airway eosinophilia, a hallmark of allergic airway hyperresponsiveness. The serological investigations did not reveal merked differences in anti-IPDI-Homopolymer IgG1-antibody titres between the groups.

Positive control results:

In previous studies the known human respiratory sensitizer TMA was investigated with the current animal model using roughly the same induction
and challenge protocol. The TMA study demonstrated that the experimental approaches employed provide an adequate basis for a clear assessment of chemicals with a strong potential to cause respiratory hypersensitivity in guinea pigs. Upon challenge with TMA, the most of the guinea pigs
experienced a characteristic "waveform" breathing pattern which had not been observed in IPDI homopolymer challenged guinea pigs. This
stereotypic breathing response has not yet been observed in naive animals and therefore provides a solid basis for the classification of strong
respiratory tract sensitizers.

Negative control results:

no relevant reactions observed

no further remarks

Conclusions:

Under the conditions of this study the test item IPDI-homopolymer did not induce respiratory sensitization in guinea pigs.

Executive summary:

A lung sensitization study with IPDI-homopolymer was performed in accordance with the exposure criteria defined in OECD TG 403 using female guinea pigs . A standard approach was used that included three intradermal injections (one per day, 5%, 50 µl in acetone). In order to investigate wether the test substance has any potential to induce specific or non-specific airway hyperreactivity an additional group of female guinea pigs was induced by using a 5 x 3 hours inhalation (147 mg/m³) sensitization protocol followed by inhalation challenge with the hapten, acetylchloline and conjugate by inhalation.

Under the conditions of this study no conclusive immediate-onset responses were observed nor was there any indirect evidence of a lung sensitizing potential, i.e. eosinophilia of airways or production of specific antibody. Therefore, this study does not provide any evidence that IPDI-homopolymer is a respiratory sensitizer.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

A lung sensitization study with 3 -isocyanatomethyl-3,5,5 -trimethylcyclohexylisocyanate homopolymer (IPDI homopolymer) was performed in accordance with the exposure criteria defined in OECD TG 403 using female guinea pigs (Bayer AG, 1996). A standard approach was used that included three intradermal injections (one per day, 5%, 50 µl in acetone). In order to investigate wether the test substance has any potential to induce specific or non-specific airway hyperreactivity an additional group of female guinea pigs was induced by using a 5 x 3 hours inhalation (147 mg/m³) sensitization protocol followed by inhalation challenge with the hapten, acetylchloline and conjugate by inhalation.

Under the conditions of this study no conclusive immediate-onset responses were observed nor was there any indirect evidence of a lung sensitizing potential, i.e. eosinophilia of airways or production of specific antibody. Therefore, this study does not provide any evidence that IPDI-homopolymer is a respiratory sensitizer.

Justification for classification or non-classification

According to the criteria of EC Regulation 1272/2008 3-isocyanatomethyl-3,3,5 -trimethylcyclohexyl- isocyanate homopolymer, isocyanurate type (IPDI homopolymer) is classified into subcategory 1B of hazard class skin sensitisation. A animal study does not provide any evidence that IPDI homopolymer is a respiratory sensitizer and no respective data are available for humans, therefore the test substance must not be classified.