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Environmental fate & pathways

Hydrolysis

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Description of key information

The stability of an other isocyanate, isopropyl isocyanate, was tested in an aqueous test solution showing a rapid degradation (half live less than 1 hour). Further the stability of 1-chloro-4-isocyanatobenzene in a second test yielded a half-life of 7.3 h. The only hydrolysis products of both isocyanates were found to be the corresponding amines. These results can be taken as read-across for the isocyanate examined here, a rapid hydrolysis in water with the corresponding amine as degradation product.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 h
at the temperature of:
25 °C

Additional information

Isocyanates are known to rapidly hydrolyse under the formation of the corresponding amine as well as solid polyurea compounds *. However, the insoluble inert polyurea is not assumed to cause environmental hazards due to the reduced uptake of high molecular mass compounds, whereas the amine is assumed to be the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of isocyanates assuming the complete transfer of the isocyanate into the corresponding amine while neglecting the formation of a certain fraction ecotoxicological not active polyurea compounds. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004). 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.

Bayer Industry Services (2003). Isopropylisocyante: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.