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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

No effects were observed at any of the loading rates tested. The test substance is thus considered to be non-toxic at the water solubility limit.

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Additional information

Two tests were performed according to OECD 201 testing guideline to assess the toxicity of the test substance to the freshwater microalgae, Pseudokirchneriella subcapitata.

In both tests, the concentration of the test substance in the medium cannot be determined no suitable analytical methods being available due to the high insolubility in water of the test substance. Therefore, the results have been expressed in terms of the loading rates.

In a first test, micro-algae were exposed to six loading rates (1.94, 4.27, 9.39, 20.7, 45.5 and 100 mg/L). As the test is highly insoluble, a solubilising agent (acetone) and ultrasound treatment were employed to prepare the test solution, followed by prolonged stirring (48 h) to aid dispersion. Then, the preparation was left stand for ca. 24h then being passed through a nylon mesh sieve (20 µm pore size) to remove the undissolved particles in suspension. The 72h-ErL50 and 72h-EbL50 values were > 100 mg/L and 36.8 mg/L, respectively. The 72h-NOELR was 9.39 mg/L. The effects observed at a concentration higher than the water solubility limit, were probably related to undissolved test material. The results obtained were thus considered as non-representative of the toxicity of the test substance and thus not reliable.

Therefore, a second test was performed to remove all undissolved test material. The test solution was prepared as described above except for the filtration. A cellulose nitrate filter with a 0.45 µm pore size was used. Six loading rates were tested (4.27, 9.38, 20.7, 45.5 and 100%). No toxicity were observed at the water solubility limit.