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Environmental fate & pathways

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Description of key information

Additional information

Bioconcentration factor (BCF):

When measured BCF values are not available, a BCF may be predicted from the relationship between Pow and BCF. According to ECHA guidance, the most common and simplest QSAR models are based on correlations between BCF and chemical hydrophobicity (as modelled by logPow). The mechanistic basis for this relationship is the analogy of the partitioning process between lipid-rich tissues and water to that between n-octanol and water (whereby n-octanol acts as a lipid surrogate). In this model, uptake is considered to be a result of passive diffusion through gill membranes.

Based on the QSAR calulation (EpiSuite - KOWWIN v1.67) logPows for C16 and C18 component was determined as follows: 11.2 (Hexadecyl nonanoate) and 12.2 (Octadecyl nonanoate); mean value: 11.7.

Nevertheless, the logPow of 11.7 (mean value) is out of the applicability domain of this calcualtion and thus according to EpiSuite – BCFBAF v.3.01 “user Guide help”: “bioconcentration factor estimates are less accurate for compounds outside the MW and logPow ranges of the training set compounds.”Furthermore, it should be considered that“BCF estimates have more instances of a given correction factor than the maximum for all training set compounds.”

However, according to ECHA guidance on information requirements and chemical safety assessment - chapter R.11: PBT assessment, May 2008, “at very high logPow (>6), a decreasing relationship between the two parameters (logPow and logBCF) is observed. Apart from experimental errors in the determination of BCF values for these very hydrophobic chemicals, reduced uptake due to the increasing molecular size may play a role as well. Moreover, the experimental determination of logPow for very hydrophobic chemicals is normally also very uncertain due to experimental difficulties (...) The aquatic BCF of a substance is probably lower than 2000 L/kg if the calculated logPow is higher than 10.

Based on this, it can safely be assumed that the BCF of SymMollient® S is below 2000 L/kg ww 

Biomagnification factor (BMF):

No experimental data are available. According to ECHA guidance, the availability of measured BMF data on predatory organisms is very limited at present and so the provided default values should be used as a screening approach designed to identify substances for which it may be necessary to obtain more detailed information. Accordingly, the default BMF value is 1 (BCFfish < 2,000) for organic substances with a logPow >9. Therefore, biomagnification appears to be low.