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Aquatic toxicity-testing on CAS 16090-02-1 presents a number of critical issues because of factors like:

- strong influence of pH on solubility

- strong adsorption to organic fraction

- influence of cation on solubility under customary test conditions (flocculation can occur)

- increase of toxicity for speciates like calcium

Based on a dissertation [1]:

- the substance forms strong ion-pairs with calcium ions in water

- the octanol-water partition coefficients of the ion-pairs are two orders of magnitude higher than the partitioning coefficient of the native substance

- the strongly decreased hydrophilicity due to ion-pair formation decreases the water solubility

The mentioned experimental results suggest precipitation of ion-pairs/complexes (the medium for the daphnia test contains Ca2++). During a test performed in Bayer facilities (report not more available) microscopic pictures of daphnia antennas were taken that showed crystalline deposits, which were interpreted as calcium complexes of same brightener. The test was then stopped.

The solubility and ionic interaction effects in the laboratory testing on CAS 16090-02-1 is an artefact and it is not representing a realistic environmental situation, as the concentrations of CAS 16090-02-1 hardly exceed 2 μg/l. Under environmental conditions, it can be expected an almost complete dissociation [2].

In well conducted short-term tests on Fish and Daphnia no effect were reported until more than 100 mg/l, while for Algae a physical effect (the turbidity of the solution) impaired the test results. Nevertheless, the result on an analogous substance (CAS 16470-24-9) demonstrated that also for algae the EC50 is higher than 100 mg/l. CAS 16470-24-9 can be considered as a conservative representative example for environmental toxicity and it does not present the solubility problems as CAS 16090-02-1.

In conclusion, for all of the three throphic levels short-term toxicity tests the EC50 is higher than 100 mg/l.

Regarding long-term studies, the test on Daphnia magna Reproduction on the substance to be registered was disregarded. Considering the 14 days repeated dose toxicity screening test on Fish, the NOEC Algae and the results of the Daphnia Reproductive Toxicity test on the analogous substance CAS 16470-24-9, all results are consistent and agree to setting a NOEC for the substance between 5 and 50 mg/l.

No further long-term studies are proposed, since direct and indirect exposure is unlikely due to the risk management measures that will be applied at industrial level and discussed in details within the exposure scenario to avoid any release of the substance directly in the municipal waste water treatment. The local RCR in surface water is calculated as 0.04 and 0.0052 based on estimated and monitored quantities.

REFERENCE

[1]“Poiger, T.: Behavior and Fate of Detergent-derived Fluorescent Whitening Agents in SewageTreatment. Swiss Federal Institute of Technology, Zürich,1994. ”

[2]HERA Report 2004: Substance: Fluorescent Brightener FWA-1 (CAS 16090-02-1)