Cyclohexane, 1,3-bis(isocyanatomethyl)-

Endpoint summary

Description of key information

Two reliable in vivo studies are available. Both studies show that 1,3-H6XDI has skin sensitising properties.

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:

12 March-18 April 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

(Adopted: 17 July 1992)

Deviations:

no

Principles of method if other than guideline:

The method followed is also described by Magnusson, B. and Kligman, AM (1970): "Allergic Contact Dermatitis in the guinea pig: identification of contact allergens", Thomas, CC Springfield, Illinois, USA

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

At the time of performance of the test the guinea pig maximisaton test was considered the most relevant test for this endpoint and this test item.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: D. Hall, Newchurch, Staffordshire, UK
- Age at study initiation: 6 to 7 weeks old
- Weight at study initiation: 455 to 534 g
- Housing: animals were housed in groups of five in suspended metal cages with mesh floors
- Diet: ad libitum (Vitamin C enriched guinea pig diet FD2; hay provided weekly)
- Water: ad libitum
- Acclimatisation period: twelve days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18.5-21
- Humidity (%): 24-61
- Air changes (per hr): approximately 15
- Photoperiod (hrs dark / hrs light): 12/12

Route:

intradermal

Vehicle:

other: Alembicol D

Concentration / amount:

0.01% v/v

Day(s)/duration:

Day 1

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Route:

epicutaneous, occlusive

Vehicle:

other: Alembicol D

Concentration / amount:

20% v/v

Day(s)/duration:

Day 8, 48 hours

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: Alembicol D

Concentration / amount:

2.5% and 5%

Day(s)/duration:

Day 21, 24 hours

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

Preliminary: 2 (intradermal injections), 8 (topical application);
Main: 10 (test), 5 (control)

Details on study design:

CONCENTRATIONS TESTED
Preliminary study:
For Intradermal concentrations 0.001%, 0.0025%, 0.005%, 0.01%, 0.025%, 0.05%, and 0.1% v/v;
For Topical concentrations: 7.5%, 10%, 15%, 20%, 30%, 50%, 70% and 100% v/v.
Main study:
Intradermal injection: 0.01% v/v;
Topical application: 20% v/v;
Challenge application: 5 and 2.5% v/v.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: three pairs of injections, 0.1 ml each: Freund's Complete Adjuvant plus water in ratio 1:1, a 0.01% v/v formulation of the test substance in Alembicol D, a 0.01% v/v formulation of the test substance in a 50:50 mixture of Freund's Complete Adjuvant plus Alembicol D.
- Exposure period: One week later day 7, same region was clipped again and treated with a topical application (0.4 ml) of a paper saturated with test material (20% v/v). An occlusive dressing was kept in place for 48 hours.
- Control group: Identical procedure as test animals, except test substance was omitted.
- Site: 40x60 mm area, hair was removed on the shoulder region
- Duration: 21 days

B. CHALLENGE EXPOSURE
- Day of challenge: day 21, two weeks after topical induction.
- Exposure period: A filter paper saturated with approx. 0.2 ml of 5% v/v test substance was applied to an anterior site of the flank. A filter paper saturated with 2.5% v/v test substance was applied to the posterior site. Patches were occluded. After 24 hours of occlusive dressing this was removed.
- Control group: All animals were treated the same.
- Site: An area on left flank of each animal was clipped free of hair.
- Evaluation (hr after challenge): 24 + 48 after removal of dressing

Positive control substance(s):

yes

Remarks:

historical control data of hexyl cinnamic aldehyde (HCA), benzocaine and 2-mercaptobenzothiazole (MBT)

Positive control results:

Summary of positive control data from 1995 and 1996: 6/10 for benzocaine, 8/10 and 10/10 for HCA, 10/10 (twice) for MBT included.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.01% intradermal, 20% epidermal, 2.5% and 5% challenge

No. with + reactions:

10

Total no. in group:

10

Clinical observations:

Necrotic effects (necrosis/ necrotic edges/ necrotic patches) in all animals, dryness and sloughinig of the epidermis in one animal, blanching in two animals.

Remarks on result:

positive indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

n.a.

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

Localized dermal reaction (restricted to a small area of the challenge site) was seen in one animal at 24 and 48 hours; dryness and sloughing of the epidermis was observed at 72 hours for another animal.

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

not specified

No. with + reactions:

6

Total no. in group:

10

Clinical observations:

Not speicified

Remarks on result:

positive indication of skin sensitisation

Remarks:

Historical data

No signs of ill health or toxicity were noted. Bodyweight increases in test group animals were comparable to control group animals.

Intradermal injections resulted in necrosis at sites receiving Freund's Complete Adjuvant in test and control animals. Slight irritation was seen in test animals at sites receiving Takenate 600, 0.01% v/v in Alembicol D and slight irritation was observed in control animals receiving Alembicol D.

Slight erythema was observed in test animals following topical induction application with Takenate 600, 20% v/v in Alembicol D. Slight erythema was seen in the control guinea pigs.

After challenge, dermal reactions (erythema and oedema) were seen in all of the ten test animals at 24 and 48 hours after challenge, compared to none in the controls. Well-defined erythema was seen in 9/10 animals, in one animal slight erythema was seen.

Oedema formation was slight in one animal, well-defined (edges of area well-defined by definite raising) in 6 animals and moderate (raised approximately 1 mm) in 3 animals.

Interpretation of results:

Category 1A (indication of significant skin sensitising potential) based on GHS criteria

Conclusions:

In a skin sensitising test in guinea pigs performed according to OECD guidance and GLP principles, Takenate 600 produced evidence of skin sensitisation (delayed contact hypersensitivity) in all of the ten test animals.

Executive summary:

A skin sensitising test in guinea pigs was performed according to OECD guidance and GLP principles. Based on a dose range finder experiment, concentrations for intradermal injection, topical application and challenge application were established at 0.01% v/v, 20% v/v and 2.5%/5% v/v Takenate 600. No signs of ill health or toxicity were noted. Bodyweight increases in test group animals were comparable to control group animals. After challenge, dermal reactions (erythema and oedema) were seen in all of the ten test animals at 24 and 48 hours after challenge, compared to none in the controls. Well-defined (or slight) erythema was seen in 10/10 animals. Oedema formation was slight in one animal, well-defined (edges of area well-defined by definite raising) in 6 animals and moderate (raised approximately 1 mm) in 3 animals. As the test substance produced evidence of skin sensitisation (delayed contact hypersensitivity) in all of the ten test animals, Takenate 600 was found to be a skin sensitiser (cat. 1A).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

For substance analogue 1,3-H6XDI, two studies are available, both performed according to OECD/EC test guidelines and GLP principles. In the first study, a skin sensitising test in guinea pigs, after challenge, dermal reactions (erythema and oedema) were seen in all of the ten test animals at 24 and 48 hours after challenge, compared to none in the controls. In the second, a test for delayed contact hypersensitivity was performed with 1,3-XDI according to Magnusson and Kligman (1970). Challenge resulted in slight to severe dermal reactions (erythema and oedema), in part accompanied by thickening, dryness and sloughing of the skin in 9/10 test animals. Only slight skin effects were seen in one control animal. Based on these data, 1,3-XDI was found to be a skin sensitiser.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

In accordance with the ECHA Guidance document "Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance" of July 2017, diisocyanates need to be considered for classification as a respiratory sensitiser. In the scientific literature diisocyanates are identified as chemicals causing the development of occupational asthma after workplace exposure. There are no data available that show that such a classification is not warranted for 1,3-H6XDI.

Justification for classification or non-classification

Based on the available studies, 1,3-H6XDI is classified cat.1A for skin sensitising properties according to the CLP Regulation (EC) No. 1272/2008.

As 1,3-H6XDI is a diisocyanate, it is classified according to the CLP Regulation (EC) No. 1272/2008 and ECHA Guidance as a respiratory sensitiser cat. 1.