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Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April - May 1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
e.g. readings were performed 24 and 48 h after start of challenge application, no data on test substance purity, no information on stability testing in the vehicle used
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Version / remarks:
(1981)
Deviations:
yes
Remarks:
e.g. readings were performed 24 and 48 hours after start of challenge application (no 48 and 72-hour value)
GLP compliance:
not specified
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
Test performed prior to LLNA guideline.
Species:
guinea pig
Strain:
other: Pirbright
Sex:
not specified
Details on test animals and environmental conditions:
TEST ANIMALS: 
- Strain: Pirbright, Hoe: DHPK (SPF - LAC.) /Boe.
- Sex: no data
- Source: Lippische Versuchstierzucht, Extertal, Germany
- Age at study initiation: no data
- Weight at study initiation (mean): 280 g
- Housing: in groups of 2 per cage, Makrolon type III-cages (14 cm x 25 cm x 42 cm)
- Diet and Water: ad libitum
- Acclimation period: approx. 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2
- Humidity (%): 45-55
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12
Route:
intradermal
Vehicle:
paraffin oil
Concentration / amount:
10 % / 0.05 mL
Day(s)/duration:
Day 0
Route:
epicutaneous, occlusive
Vehicle:
unchanged (no vehicle)
Concentration / amount:
100 % / 0.5 mL
Day(s)/duration:
Day 7 / exposure 48 h
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
paraffin oil
Concentration / amount:
100 % / 0.5 mL
Day(s)/duration:
after 3 weeks / exposure 24 h
No. of animals per dose:
20 test animals / 20 controls
Details on study design:
RANGE FINDING TESTS: For range finding 0.5 mL test substance formulation at 100, 75 , and 50 % (in paraffin oil) was applied once on 2 animals. Primary irritation was not detected in any of the concentrations tested.

MAIN STUDY
Prior to treatment the fur of the shoulder region was shorn (ca. 8 x 5 cm).

A. INDUCTION EXPOSURE
Day 0: Intradermal induction - pairwise injections in the shoulder region of 0.05 mL
1) test substance 10 % in vehicle
2) test substance 10 % in FCA (FCA diluted 1:1 in oleum arachidis)
3) FCA diluted 1:1 in aqua dest.
Control animals received 1) FCA undiluted 2) paraffin oil 10 % in in FCA (FCA diluted 1:1 in oleum arachidis) and 3) paraffin oil undiluted.

Day 7: Topical induction - 0.5 mL undiluted test substance or vehicle were applied on the same sites used for intradermal injection; closed patch treatment for 48 hours

B. CHALLENGE EXPOSURE
3 weeks after dermal induction: challenge - 0.5 mL undiluted test substance is applied on the left flank and 0.5 mL vehicle on the right flank, closed patch treatment for 24 hours, readings after patch removal, i.e. 24 hours after challenge start and at 48 hours after challenge.

Assessment scheme:
0 = no skin reaction   
0.5 = slight, spotted (i.e. irregular) erythema
1 = slight, confluent, or moderately spotted erythema   
2 = moderate erythema    
3 = severe erythema or edema
Positive control substance(s):
no
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
100 %
No. with + reactions:
20
Total no. in group:
20
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
100 %
No. with + reactions:
19
Total no. in group:
20
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0 %
No. with + reactions:
0
Total no. in group:
20
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0 %
No. with + reactions:
0
Total no. in group:
20

24 and 48 hours after challenge start animals exhibited slight up to moderate erythema (24 hours after challenge start: 20/20 positive, mean score 1.18; 48 hours after challenge: 19/20 positive, mean score 1.10)

The negative control group that received the vehicle alone for challenge showed no skin reactions.

Executive summary:

The potential for skin sensitization of 4,4´-Methylenedicyclohexyl diisocyanate was tested in a guinea pig maximization test similar to OECD 406. The test item was administered at a concentration of 10 % intradermally (with FCA, in paraffin oil) and 100 % epidermally (occlusive) to 20 guinea pigs. After challenge at a 100 % concentration slight to merked erythema was observed in 20/20 animals 24 hours after challenge and in 19/20 animals 48 hours after challenge. No skin reactions were observed for control animals. Thus, a sensitising potential of the test substance can be concluded.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

4,4´-Methylenedicyclohexyl diisocyanate has been assessed in the OECD HPV programme, 2005.

Partly cited from SIAR of SIAM 20 (Paris, April 19 -22, 2005): "Animal data are not uniform however they frequently provide evidence of a skin sensitizing potential of 4,4´-methylenedicyclohexyl diisocyanate." Humans case reports have demonstrated skin effects usually attributable to occupational exposure to 4,4´-methylenedicyclohexyl diisocyanate. Some of these cases were subsequently determined to be cases of dermal sensitization as confirmed by patch testing.

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:
Sept - Oct 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Lung sensitization study following intradermal induction. For inhalation challenge the criteria specified in OECD TG 403 were fulfilled in so far as these are applicable to this study.
GLP compliance:
yes
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Strain: Dunkin-Hartley Pirbright-White (Crl: (HA)BR)
- Source: Charles River, Sulzbach, Germany
- Age at study initiation: approx. 2 months
- Weight at study initiation: at study start the variation of individual weights did not exceed +/- 10 % of the mean
- Housing: in groups of 4 in Makrolon Type IV cages (according to Spiegel & Goennert, Zschr. Versuchstierkunde 1, 38, 1961 and Meister, Zschr. Versuchstierkunde 7, 144-153, 1965)
- Diet and Water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): approx. 50 %
- Air changes (per hr): approx. 10
- Photoperiod (hrs dark / hrs light): 12/12
Route of induction exposure:
intradermal
Route of challenge exposure:
inhalation
Vehicle:
other: for intradermal induction: olive oil; for aerosol inhalation: air
Concentration:
intradermal induction: 100 µl / 0.13 % solution in olive oil
challenge: 68 ± 3.6 mg/m³ (mean concentration)
No. of animals per dose:
8 test animals / 8 controls
Details on study design:
ADMINISTRATION:
Groups of eight female guinea-pigs were intradermally induced once on Day 0 (injection volume: 100 µl / 0.13 % solution in olive oil). Eight female controls received vehicle alone under otherwise identical conditions. Following a recovery period of approximately four weeks (starting on Day 28) a test material-hapten challenge was performed at 68 ± 3.6 mg/m³ (mean concentration; challenge duration: 30 min). The aerosolized test material was proven to be of adequate respirability.

EXAMINATIONS:
During and after challenge exposures with the hapten, 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. During sacrifice the trachea, lung, and lung associated lymph nodes were fixed and subjected to histological evaluation.
Results:
Following induction, slight skin reactions at the injection sites occurred. During or following test material-challenges, the incidence of immediate-onset respiratory reactions was roughly the same in vehicle controls and test substance-induced animals. No deaths or anaphylactic reactions were observed during challenge, and no clinical signs or specific abnormalities were observed at necropsy. The histopathological evaluation of lungs revealed a marked influx of eosinophils in test material-sensitized guinea-pigs, a characteristic feature of asthma and airway hypersensitivity.
The study provides evidence that the test substance is a weak respiratory sensitizer in guinea pigs.

Data from IUCLID4

RS-Freetext:
Following induction, slight skin reactions at the injection sites occurred. During or following test material-challenges, the incidence of  immediate-onset respiratory reactions was roughly the same in vehicle controls and test substance-induced animals. No deaths or anaphylactic reactions were observed during challenge, and no clinical signs or specific abnormalities were observed at necropsy. The histopathological evaluation of lungs revealed a marked influx of eosinophils in test  material-sensitized guinea-pigs, a characteristic feature of asthma and airway hypersensitivity.
The study provides evidence that the testsubtance is weak respiratory sensitizer in guinea pigs.

Executive summary:

4,4´-Methylenedicyclohexyl diisocyanate has been assessed in the OECD HPV programme, 2005.

Cited from SIAR of SIAM 20 (Paris, April 19 -22, 2005): In the study "sensitization of 8 guinea pigs with a single intradermal injection of 4,4´-methylenedicyclohexyl diisocyanate (100 μl, 0.13% solution in olive oil) followed after four weeks by inhalation challenge with the 4,4´-methylenedicyclohexyl diisocyanate hapten (30 min, 68 ± 3.6 mg/m³) was examined. No immediate-onset responses were observed. Gross pathological examinations showed roughly the same incidence of lung changes in all Guinea pigs of this study. The histopathological assessment of the degree of eosinophilia revealed an increased influx of eosinophilic granulocytes in animals sensitized with 4,4´-methylenedicyclohexyl diisocyanate. Because eosinophils are known to play a critical role in pathogenesis of asthma and of other hyperresponsive airway diseases the study provided evidence that 4,4´-methylenedicyclohexyl diisocyanate is a weak respiratory sensitizer in guinea pigs."

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

4,4´-Methylenedicyclohexyl diisocyanate has been assessed in the OECD HPV programme, 2005.

Cited from SIAR of SIAM 20 (Paris, April 19 -22, 2005): "Although no validated animal model is available to assess the potential for respiratory sensitization or asthma in humans, animal data support to some extent the hypothesis that respiratory hypersensitivity may be induced by 4,4´-methylenedicyclohexyl diisocyanate."

Justification for classification or non-classification

According to Regulation (EC) No 1272/2008, Annex VI, classified as skin sensitising Cat.1 (H317: May cause an allergic skin reaction).


According to Regulation (EC) No 1272/2008, Annex VI, classified as respiratory sensitising Cat.1 (H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled).


 


Regarding sub-categorisation of skin sensitisation:


Regulation (EU) No 286/2011, amending Regulation (EC) No 1272/2008, stipulates that where data are sufficient a refined evaluation should allow the allocation of skin sensitisers into sub-category 1A, strong sensitisers, or sub-category 1B, other skin sensitisers. Where data are not sufficient a classification as Skin Sensitisation Category 1 without sub-categorisation should apply. For classification of 4,4´-methylenedicyclohexyl diisocyanate the following considerations were taken into account:


The classification criteria of regulation EU No 286/2011 cover human as well as animal data. The animal data for 4,4´-methylenedicyclohexyl diisocyanate give no clear picture regarding potency, as e.g. the GPMT were conducted with relatively high induction concentrations and dose-response is not well examined, and with low challenge concentration the result was negative. There is also some inconsistency regarding the irritation properties that might influence the outcome of studies. The result of the LLNAs point to a high potency, but as this test system reveals positive results for skin as well as respiratory sensitizers (and the substance is in fact classified for respiratory sensitization) it can not be conclusively evaluated whether the indicated potency directly relates to skin sensitization. Human experience show positive patch test reactions indicating skin sensitization, but this seems not to be a very frequent observation. A publication from the Federal Institute of Risk Assessment in Germany (BfR) in 2003 assessed the skin sensitization potency of 244 substances taken into account human experience (Schlede et al., Toxicology 193, 219-259, 2003) and came to the conclusion, that 4,4´-methylenedicyclohexyl diisocyanate would fall into category "B" ("Solid-based indication for contact allergenic effects because of: (1) less frequently proven contact allergenic effects in humans taking into account existing positive animal data..."). Compared to the classification criteria of regulation EU No 286/2011 the category "B" would best fit to Category 1B which based on human experience is defined as e.g. "diagnostic patch test data where there is a relatively low but substantial incidence of reactions in a defined population in relation to relatively high exposure". Since the assessment of the BfR some more human cases are published.  Overall as the data on potency are limited and human data and animal data are not fully consistent it is concluded that the available data currently do not allow a solid assessment of the potency. Therefore based on the criteria of regulation EU No 286/2011 "3.4.2.2.1.1. Skin sensitisers shall be classified in Category 1 where data are not sufficient for sub-categorisation" that leads to Category 1 (without further sub-categorization).


 


Regarding sub-categorisation of respiratory sensitisation:


Regulation (EU) No. 286/2011, amending Regulation (EC) No 1272/2008, declares that where data are sufficient a refined evaluation allows the allocation of respiratory sensitisers into sub-category 1 A, strong sensitisers, or sub-category 1 B, other sensitisers. Where data are not sufficient a classification as Respiratory Sensitisation Category 1 without sub-categorisation should apply. For 4,4'-methylenedihexyl diisocyanate the available animal experiments do not allow a solid assessment on the potency of respiratory sensitisation. Moreover, specific, internationally harmonised test procedures for animal models to assess the respiratory sensitisation potential of low- or high-molecular weight compounds do not yet exist. Thus, a comparative evaluation of respiratory sensitisation potency based on animal models is not an easy subject. Furthermore, the available human data do not lead to a robust dicrimination on the frequency of occurence as high or low to moderate. Conclusively, the substance is classified for respiratory sensitisation without sub-categorisation.