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Environmental fate & pathways

Adsorption / desorption

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Description of key information

A measured log Koc is available for alkenes C20 - 24. Fox and White (2008) report a log Koc of >5.63 using the HPLC screening column method. Other than this single experimental value, measured log Koc are not available for any other category members. Instead, log Koc have been calculated on the basis of measured or calculated log Kow using a QSAR. The calculated log Koc increase with increasing carbon number.

Key value for chemical safety assessment

Koc at 20 °C:
1 698

Additional information

Log Kow is observed to increase with increasing carbon number for members of this category. As the measured log Kow of the category member with the lowest carbon number (C6, hex-1-ene) is >3 the adsorption/desorption endpoint cannot be waived for any category member. However, ECHA's Guidance on Information Requirements and Chemical Safety Assessment R7a Endpoint Specific Guidance (2008) indicates that before commissioning a new study alternative sources of data (e.g. QSAR) on the adsorption/desorption potential of a chemical should used. If the calculated log Koc proves to be influential in the risk assessment then it may be necessary to conduct a new study.

Soil sorption of non-ionic substances can be estimated from their log Kow. Several QSARs have been developed that calculate the log Koc of non-polar hydrocarbons on the basis of their log Kow (e.g. Sabljic and Gusten, 1995). Category members with carbon number ranges of C6-C16 fall within the applicability domain of this QSAR. For category members with carbon numbers above this log Koc are not calculated, but instead read across from other category members based on the observed trend in calculated log Koc. The calculated log Koc support the measured value for alkenes C20-24.

[LogKoc: 3.23]