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Environmental fate & pathways

Phototransformation in air

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Description of key information

The half-life of 4,4'-MDI in the atmosphere has been estimated using the AOPWIN (TM) (v1.92) model and was 0.92 days (Pemberton and Tury, 2008).

Key value for chemical safety assessment

Half-life in air:
1 d

Additional information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). Hence, data of the category substances can be used to cover this endpoint.

There are no measured phototransformation data in air for the test substance. According to Pemberton and Tury (2008), the estimated dissipation half-life has been rounded off to 1 day. The exactly calculated value is 0.92 days.

This result was corroborated with a phototransformation analysis of a structural analogue 4-tolylisocyanate (PTI) (Carter et al., 1999). The phototransformation was determined using the relative rate method where the rates of consumption of PTI relative to a reference compound with a known OH radical rate constant were measured in the presence of OH radical source. The environmental chamber system employed was the Dividable Teflon Chamber. This gave a phototransformation half-life of 0.89 days.