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Environmental fate & pathways

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Releases into the environment may occur during production of isophorone diisocyanate, during formulation and use of formulations as well as from its use as a monomer for the production of polymers or other downstream products.

 

Distribution modelling according to Mackay Level I indicates that the main target compartments will be soil and sediment with approximately 43 % each, followed by water with about 10 %.The calculated Henry’s law constant of 0.941 Pa m3/mol (vapor pressure x molecular weight / water solubility) at 20-23 °C indicates low volatility from aqueous solution. Both Henry’s law constant and adsorption / desorption constant cannot be studied due to rapid hydrolysis of isophorone diisocyanate. Environmental distribution considerations for isophorone diisocyanate are of little relevance because the reaction with water is expected to eliminate the substance from the environment rapidly.

The rate constant of the OH radical sensitized indirect photodegradation of isophorone diisocyanate corresponds to a half-life of 1.8 days at a 24 hour mean OH radical concentration of 500,000 molecule/cm³, which is typical of Central Europe. A preliminary hydrolysis test resulted in a dissipation half-life of 0.84 hours (approx. 50 minutes) at 23 °C. No ready biodegradation (0% degradation within 28 days) was observed in a manometric respiratory test performed with domestic, non-adapted activated sludge according to Directive 92/69/EEC, C.4-D. Biodegradation of the substance itself is irrelevant as primary degradation step because hydrolysis is much faster.

Rapid hydrolysis of the substance makes approximation of equilibrium in the environment impossible resulting in a low potential for bioaccumulation.