Butyl isocyanate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The sensitisation potential of butyl isocyanate was evaluated in the guinea-pig by intradermal route and cutaneous application, according to the maximisation method of Magnusson and Kligman. This study provides evidence of a skin sensitizing potential of n-butyl isocyanate.

Migrated from Short description of key information:
skin sensitisation: method according Magnuson + Kligman; result: sensitising

Respiratory sensitisation

Endpoint conclusion

Additional information:

Due to regulation 67/548/EEC isocyanates have to be classified as respiratory sensitisers with R 42. Based on comparative analysis regarding studies on skin sensitisation with other isocyanates (p-isopropylphenylisocyanate_CAS 31027-31-3, n-butylisocyanante_CAS 111-36-4, 3,4-dichlorphenylisocyanante_CAS 102-36-3, 3,5-dichlorphenylisocyanate_CAS 28479-22-3, phenylisocyanate_CAS 103-71-9, trifluormethoxyphenylisocyanate_CAS 35037-73-1) which all have strong skin sensitisation properties, monoisocyanates without reliable studies will be additionally classifified with R43.

According RL 1272/2008/EG (GHS) a classification as Skin Sens.1A (H 317: May cause an allergic skin reaction) is warranted, based on comparative analysis regarding other isocyanates isocyanates (p-isopropylphenylisocyanate_CAS 31027-31-3, n-butylisocyanante_CAS 111-36-4, 3,4-dichlorphenylisocyanante_CAS 102-36-3, 3,5-dichlorphenylisocyanate_CAS 28479-22-3, phenylisocyanate_CAS 103-71-9, trifluormethoxyphenylisocyanate_CAS 35037-73-1 are all strong sensitisers, classified as Skin Sens. 1A). No classification for respiratory sensitisation is necessary (see discussion below).

There are no data on respiratory sensitization available. p-tolyl isocyanate is a monoisocyanate. The UK Health and Safety Commission Working Group on the Assessment of Toxic Chemicals, Working Group on Action to Control Chemicals concluded performed an assessment of the potential for isocyanic acid and other monoisocyanates to cause respiratory irritation and sensitization (WATCH Committee Paper WATCH/2008/4, 17 Jun., 2008; http://www.hse.gov.uk/aboutus/meetings/iacs/acts/watch/170608/p4.pdf) and came to the following conclusion: “With the exception of methyl isocyanate, information on the toxicity of the monoisocyanates is sparse. There is no direct evidence that any of the monoisocyanates can cause respiratory sensitisation. … However, this indirect information on the allergenicity and immunoreactivity of the monoisocyanates is very limited, and insufficient to reliably inform on their potential to cause respiratory sensitisation.” A similar conclusion was drawn by the German MAK commission concerning the monoisocyanates in 2009 (MAK- und BAT-Werteliste 2009).

 

In addition it should be also mentioned that the ‘default’ assumption of the former EU hazard classification systems that all isocyanates have the potential to cause respiratory sensitisation is not in agreement with the strategy for evaluating respiratory sensitisation data in the Technical Guidance Document (TGD) on information requirements for REACH (R.7a; page 256ff). The TGD proposes that, in the absence of specific health effects data, only diisocyanates that also meet the criteria for classification for skin sensitisation are presumed to be respiratory sensitisers.

Migrated from Short description of key information:
respiratory sensitisation: Guinea pigs were exposed by head only to an aerosol of protein-isocyanate conjugate. 
result: Result: BSA-BI (bovine serum albumin-butyl isocyanate conjugate) induced only weak, transient responses
to a few guinea pigs.

Justification for classification or non-classification

Due to regulation 67/548/EEC isocyanates have to be classified as respiratory sensitisers with R 42. Based on comparative analysis regarding studies on skin sensitisation with other isocyanates (p-isopropylphenylisocyanate_CAS 31027-31-3, n-butylisocyanante_CAS 111-36-4, 3,4-dichlorphenylisocyanante_CAS 102-36-3, 3,5-dichlorphenylisocyanate_CAS 28479-22-3, phenylisocyanate_CAS 103-71-9, trifluormethoxyphenylisocyanate_CAS 35037-73-1) which all have strong skin sensitisation properties, monoisocyanates without reliable studies will be additionally classifified with R43.

According RL 1272/2008/EG (GHS) a classification as Skin Sens.1A (H 317: May cause an allergic skin reaction) is warranted, based on comparative analysis regarding other isocyanates isocyanates (p-isopropylphenylisocyanate_CAS 31027-31-3, n-butylisocyanante_CAS 111-36-4, 3,4-dichlorphenylisocyanante_CAS 102-36-3, 3,5-dichlorphenylisocyanate_CAS 28479-22-3, phenylisocyanate_CAS 103-71-9, trifluormethoxyphenylisocyanate_CAS 35037-73-1 are all strong sensitisers, classified as Skin Sens. 1A). No classification for respiratory sensitisation is necessary (see discussion).