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Sediment toxicity

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Under environmental conditions the substance dissociates completely in water. Distribution modelling (Mackay) yields 100% of the substance in the aqueous phase and not exposed to sediment. Bivalent metal cations like Ca2+ are present in the aqueous environment in high concentrations compared to the substance and form clusters with the anionic substance. These clusters exhibit different partitioning behaviour. Specific interactions and ion-exchange interactions between the substance and suspended solids may contribute strongly to the observed partitioning (Poiger 1994). Precipitation as the calcium or magnesium salts is a pathway that can be significant (Baughman 1994). There is sufficient weight of evidence leading to the assumption that the substance itself is not exposed and is not harmful to sediment organisms.

It can be shown by exposure estimation with the EUSES Modelling program version 2.1 that under the use conditions of the test item the sediment concentrations are low. As measured sorption/desorption data are available from an OECD 106 study (see IUCLID Section 5.4.1) it is justified to apply the Equilibrium partitioning method to derive a reasonably PNEC sediment (PNEC sediment (freshwater): 251 µg/L sediment dw). Based on the estimated PEC local sediment and the PNEC sediment it can be demonstrated that sediment toxicity testing is not warranted. The statement given above fulfills the requirement for waiving as given in 1907/2006/EC Annex X, Column 2, 9.5.1.

Poiger, T., Behavior and Fate of Detergent-derived Fluorescent Whitening Agents in Sewage Treatment, Dissertation ETH Zürich No. 10832, EWAG 1994, p. 37 – 44.

Baughman, G.L., Fate of dyes in aquatic systems. Part 3. The role of suspended sediments in adsorption and reaction of acid and direct dyes. Dyes Pigm., 1995. 27(3), p. 197-210.