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Description of key information

Key value for chemical safety assessment

Additional information

No data has been provided as this not a required endpoint under REACH.


The lack of terrestrial bioaccumulation data is not considered as being of concern since MDI substances are not predicted to occur in appreciable concentrations in the terrestrial environment. Bioaccumulation in soil is therefore waived for all substances of the category. Furthermore, as described above, due to the rapid reaction with water, the substances of the MDI category react quickly with water and hence will be rapidly hydrolysed in contact with aqueous media. As a result, any attempt to measure its bioaccumulation potential in terrestrial organisms will measure the bioaccumulation of the hydrolysis products. This is corroborated by the results from the MDI bioaccumulation studies reported in Chapter 2.7.1 of the Category Justification Document. Due to the rapid reaction of the MDI substances with water, the bioaccumulation study results reflect the bioaccumulation of their transformation products and not necessarily of the MDI substance constituents themselves. Measurable MDA traces after exposure of substances of the MDI category with water are of transient nature. Furthermore, as described above, the MDI substances will polymerize in the aquatic environment to form solid polyurea. Therefore, this solid, insoluble material is inert, essentially not bioavailable and therefore not expected to cause adverse effects in the environment.
The reactivity of the NCO-group with water, the low measured BCF in fish and the evidence of the mesocosm study, suggest that MDI substances have a low potential to bioaccumulate in terrestrial food-chains. Thus, for substances of MDI category, the terrestrial organisms are not considered relevant for bioaccumulation studies and risk assessment.

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