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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Exponentially growing cultures of a unicellular freshwater green alga Desmodesmus subspicatus were exposed to different concentrations of 400160 for a period of 72h. Under the tested conditions the lowest concentration which causes reduction of the growth compared to the control within a 72-h exposure period was 100 mg/L (=LOELR) whereas the highest concentration not causing growth inhibition (=NOEC) was 46 mg/L. Therefore the loading rate of the test substance causing 50% reduction in growth was higher than 100 mg/L (=EL50).

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Additional information

The study has been performed according to OECD guideline 201 and EU method C.3 in a GLP certified testing facility.

The study was performed using five concentrations of 400160 ranging from 4.6 to 100 mg/L. The unicellular freshwater green alga Desmodesmus subspicatus was exposed for a period of 72 h. The cell concentration of each replicate was determined by measuring the absorption of the cuvettes at 440 nm every 24 h with a spectral photometer. With the absorption values, the cell number was calculated. Then the growth rate µ, the area under the growth curve (AUC) and the yield were determined.

As the test item is poorly soluble in water, the water-accommodated fraction was tested. Results based on the loading rate (nominal concentrations) as the measured concentrations of 400160 in medium were lower than the limit of quantification.

Potassium dichromate was tested as positive control. No observations were made which might cause doubts concerning the validity of the study outcome as all validity criteria were met. Therefore the results of the test can be considered valid.

The following parameters were determined:

Endpoint

NOELR

LOELR

EL50

Growth rate (µ)

46 mg/L

100 mg/L

> 100 mg/L

AUC

46 mg/L

100 mg/L

Approx. 100 mg/L

Yield

46 mg/L

100 mg/L

98 mg/L