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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

A measured BCF is not available for any of the members of this category. Instead, log BCF have been calculated on the basis of measured or calculated log Kow using two QSAR. The calculated BCF increase from C6 to C14, before decreasing at higher carbon numbers. The maximum calculated log BCF was 4.66 for tetradecene.

Key value for chemical safety assessment

Additional information

A measured BCF is not available for any members of this category. 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 bioaccumulation endpoint cannot be waived for any category member. However, ECHA's Guidance on Information Requirements and Chemical Safety Assessment R7c Endpoint Specific Guidance (2008) indicates that before commissioning a new vertebrate test alternative sources of data on the bioaccumulation potential of a chemical should be used.

Nonpolar substances have been shown to have a linear relationship between log Kow and BCF in the log Kow range 1 -6. However, at log Kow >6 a decreasing relationship is observed. Several QSAR have been developed that calculate the BCF of non-polar, hydrophobic compounds on the basis of their log Kow (e.g. Veith et al, 1979, Connell and Hawker, 1988 and USEPA, 2008). Alpha olefins with carbon number ranges of C6-C20 and olefins with carbon number ranges of C6-C22 fall within the applicability domain of these QSAR. For category members with carbon numbers above this log BCF are not calculated, but instead read across from other category members based on the observed trend in calculated log BCF.

The log Kow of icos-1 -ene has been calculated in KOWWIN (log Kow 10.03) and SPARC (log Kow 11.65). The log Kow of icos-2-ene has been calculated in KOWWIN (log Kow 9.95) and SPARC (log Kow 11.68). ECHA's guidance on information requirements and chemical safety assessment - Part C: PBT assessment (2008) states that the aquatic BCF of a substance is probably lower than 2000l/kg if the calculated log Kow is higher than 10. As none of the Kow models have experimental data in this Kow range the reliability of modelled log Kow values >10 is not known. However, as both models indicate a log Kow >10 we can conclude that category members with carbon numbers of C20 and above are unlikely to bioaccumulate.

Category members with carbon number ranges of C10-C18 have calculated log BCF greater than 3, indicating that they may bioaccumulate or pose a risk of secondary poisoning.