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Toxicity to aquatic algae and cyanobacteria

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Description of key information

No toxic effects against algae were observed at the limit of water solubility under exposure conditions.

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Additional information

A study was performed to assess the adverse effects of Triazin UV-Absorber on the growth rate (= rate of increase in cell density with time) and the yield (= biomass at time t minus initial biomass) of the planktonic freshwater algal species Desmodesmus subspicatus (former name: Scenedesmus subspicatus) over several generations.

The study was conducted in accordance with Commission Regulation (EC) No 761/2009 amending Regulation No 440/2008, Method C.3 ‘Freshwater Alga and Cyanobacteria, Growth inhibition test’ (2009) which is equivalent to OECD Guideline for Testing of Chemicals No. 201 (2006).

Exponentially growing algal cells were exposed for a period of 72 hours to a range of concentrations, nominally 0.5 and 1.0 mg/L of Triazin UV-Absorber dissolved in dilution water. Auxiliaries used to prepare the test media were an ultrasonic bath, a magnetic stirrer and a centrifuge.

The cell densities were measured at 24 hour intervals. Inhibition of the algal population was measured as reduction in growth rate (index r), relative to control cultures grown under identical conditions. The following values were determined:

Results [mg/L]:

ErC 50 (0-72 h): > 0.0063

ErC 10 (0-72 h): > 0.0063

NOEC [r] (tα 0.05): ≥ 0.0063

LOEC [r] (tα 0.05): > 0.0063

No toxic effects against algae were observed at the limit of water solubility under exposure conditions.

The results are expressed in terms of geometric mean measured concentrations (lower limit of quantification 0.005 mg/L). Effective concentrations ranged from 1.0% to 1.6% of nominal values at 0 hours. After 72 hours exposure all analytical values were below the quantification limit (0.005 mg/L).