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Environmental fate & pathways

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ZMBT is essentially not volatile with the Henry's law constant H lower than 1.53*10-12Pa * m³/mole at 25°C from aquatic media according to the criteria of Thomas (1990). The distribution calculation (Mackay level I) showed that the main target compartment for ZMBT is soil and sediment of 46.75% and 47.27% , followed by water of 5.65%. However, this calculation is based on a QSAR estimation of the partition coefficient with KOWWIN v. 1.67, which is not applicable for organic complexes. The estimated logP of 5.02 is deemed much too high as already the water solubility of ZMBT is in the range of 20 mg/L indicating that a high logP around 5 is not reasonable or realistic

The read across approach from MBT is used as a worst case consideration to cover the endpoint of adsoprtion/desorption. According to the interpretation from Swann, MBT has moderate adsorption potential in soil/sediment with the adsorption coefficient (log Koc) of 2.51- 3.55. Considering the lower water solubility of ZMBT in comparison to MBT but higher Log Pow, the adsorption potential of ZMBT is expected to be higher than MBT. However the lower log Koc of 2.51 is used to estimate PNECs for sediment and soil compartment as a worst case.