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Environmental fate & pathways

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Diquat C16 -18 is predicted to have a low bioaccumulation potential.

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. A measured log Kow of 0.0 (slow-stirring method according to OECD 123) indicates tha

t the test substance will have 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 when compared to the control for the surviving daphnia's. These observations result in the derivation of a NOEC of 270 µg/L 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.

The substance will sorb strongly to soil and sediment with an observed Kd ranging from 16000 to 190000 L/kg for loamy sand to clay soil. In a chronic earthworm test no effects were observed up to a concentration of 1000 mg/kg (NOEC = 1000 mg/kg dw). This indicates a low bioaccumulation potential for the soil compartment despite the relatively high sorption.