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Environmental fate & pathways

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Calculation of the log Koc to determine the potential for adsorption/desorption of chemicals is acceptable provided that a recognised and scientifically robust method is used. The TGD includes a method for calculating a log Koc using the log Kow. As a Log Kow was not available for Hydrocarbons, C5, n-alkanes, isoalkanes it was deemed suitable to use data from n-pentane to read-across as the substances have a similar structure and so are predicted to have a similar behaviour in the environment. The log Kow of n-pentane is 3.54. The Koc was calculated to be 794.3 (log Koc = 2.9) using TGD calculation of Koc = 0.81 x Log Kow + 0.1. This value was also used in the EU RAR for n-pentane and so is considered suitable as key study for this endpoint. The Koc of cyclopentane was calculated as 339 using the same equation and the Log Kow of 3. These values indicate that although the adsorption of the pentane substance to soil will be moderate they still have good mobility in the environment.