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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Direct or indirect exposure  of sediment is unlikely.

Key value for chemical safety assessment

Additional information

TDI is rapidly hydrolysed in aqueous solution with a half-life of under one minute. TDI is hydrophobic and poorly soluble in water and thus the heterogeneous reaction with water or soil is less rapid. The major product of such a reaction is insoluble polyurea. In the production of TDI the formation of insoluble polyurea would cause abrasion problems and blockage of valves and pipes and therefore releases of TDI to effluents are expected to be non-existent. Since production is performed in closed systems, releases to soil and sediment are also expected to be negligible (TDI producer’s draft risk assessment report, December 2008, chapter 3.1.1). Furthermore, the EUSES (2.0) program has been used to calculate PEC values based on measured emission data provided by TDI producers and processors, including polyurethane producers (ibid., chapter 3.1.5.3). Calculated PEC values were 1 x 10-9 mg/l for water, 5x10-10 mg/kg for sediment and ranged from 3.2 x 10-9 to 6.9 x 10-8 mg/kg for soils/grassland. The corresponding PEC/PNEC ratios would be extremely small and less than 1.

Taking into account the scientific and exposure arguments, it appears appropriate to waiver the long-term fish/plant/soil and sediment toxicity studies.

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