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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The BCF is calculated applying the EPIsuite v4.0 QSAR on a measured log Kow of 0. This log Kow is measured using a slow-stirring method at 1% of the CMC. The CMC is 790 mg/L. This high CMC value supports the measured log Kow of 0.

Key value for chemical safety assessment

BCF (aquatic species):
70.79 L/kg ww

Additional information

Diquat C16 -18 sorbs easily to negatively charged surfaces like glassware, clay etc and the parent is biodegraded into an intermediate which has a shorter alkyl chain with most likely a carboxilic acid at the end. Standard OECD 305 tests are technically not feasible with these strongly sorbing easily degradable 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 biodegraded. The bioaccumulation potential of diquat C16 -18 was therefore assessed based on a measured log Kow. This log Kow of 0 is measured in an OECD 123 slow-stirring test. The observed low Log Kow indicates that Diquat C16-18 has a low bioaccumulation potential.

The predicted low bioaccumulation potential is supported by the low acute to chronic ratio observed in the long-term daphnia test.

The daphnia reproduction test result shows that at 810 μg/L all parental daphnids were immobile within two days, without reproduction, while at the next concentration of 270 µg/L there is no detrimental effect on reproduction for the surviving daphnids when compared to the control. These observations result in the derivation of a NOEC of 270 µg/L for reproduction 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.

A calculated BCF of 70.79 indicates that N,N,N',N',N''-Pentamethyl-N-C16-18 (even numbered) C18 unsat.-alkyl-1,3-propanediammonium chloride has a low bioaccumulation potential