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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/1,3-BD/DEG/PG in the atmosphere has been estimated using data from the read-across substance 4,4'-MDI. The AOPWIN (TM)(v1.92) model estimated a half-life of 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. The read-across justification document is attached in IUCLID section 13.

There are no measured phototransformation data in air for the test substance. 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). 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.

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