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Environmental fate & pathways

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Standard OECD 305 tests are technically not feasible with these strongly sorbing hydrolytically unstable substances. In addition is the route of exposure in a standard OECD 305 test unrealistic for these substances because the substance will either be sorbed or (bio)degraded. The bioaccumulation potential of the alkyl amidoamines/imidazolines was therefore assessed based on a measured log Kow.

As indicated before, alkyl amidoamines/imidazolines are hydrolyzed and biodegraded and it is therefore unlikely that they will accumulate in the food chain. Since there is a log Kow measured using the slow stirring method according to OECD 123, this value was used to predict the bioaccumulation potential. Based on this log Kow value of 2.2, the calculated log BCF is 1.24 (BCF = 17.4 EpiSuite v4.0).

Despite the fact that the log Kow is measured applying the most appropriate method according to the REACH guidance i.e. the slow stirring method (OECD 123), there is unfortunately no reliable relationship between the measured log Kow and BCF for this type of substances. The predicted low bioaccumulation potential is however supported by the low acute to chronic ratio observed in the long-term daphnia test.

The daphnia reproduction test result for e.g. DETA based imidazoline shows that at 810 μg nominal/L all parental daphnids were immobile within a few days, without reproduction, while at the next concentration of 270 µg nominal/L not only is there no immobilisation, but there is no detrimental effect on reproduction when compared to the control. These observations result in the derivation of a NOEC of 270 µg/L, resulting in a low acute-to-chronic ratio. A low acute-to-chronic ratio is indicative of a non-specific mode of action and is often associated with not systemic effects. This observation is consistent with the known effects of cationic surfactants on aquatic organisms, where toxicity is associated with physical binding to respiratory membranes. This explains the steep concentration curves seen and the lack of intermediate chronic effects on reproduction.