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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of PPDA towards Desmodesmus subspicatus was determined according to OECD Guideline 201.

Key value for chemical safety assessment

EC50 for freshwater algae:
73 mg/L
EC10 or NOEC for freshwater algae:
7 mg/L

Additional information

The study was performed according to OECD Guideline 201 using five concentrations ranging from 4.6 to 100 mg/L. Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the absorption of the solutions at 440 nm every 24 hours with a spectral photometer. The cell density of the cultures was calculated based on the correlation curve between the adsorption and the cell density of the cultures determined by cell counting using a cell counter. Growth rate µ, area under the growth curve (AUC[1]) and the yield[2]were determined from the cell densities at the respective observation times.

Significant inhibition of algal growth was observed at the following concentrations:

22 / 46 / 100 mg/L. Because of cloudiness of the test solution, the highest test concentration was not used for evaluation of the results.

At the start and at the end of the test, the content of the test item in the test solutions was determined using HPLC. The measured concentrations lay between 88 % and 93 % of the nominal concentration at the beginning of the test and between 47 % and 76 % at the end of the test. The recovery after 72 hours was in a range of 51 and 85 % of the start concentration. Therefore, the determination of the results was based on the mean of the measured concentrations.

The EC50s of potassium dichromate were tested in a separate reference test. The values lay within the normal range of the laboratory.

The following results for the test item PPDA were determined:

Endpoint

NOEC

LOEC

EC10

EC50

Growth Rate

7.0 mg/L

16 mg/L

41 mg/L

> 100 mg/L

AUC

7.0 mg/L

16 mg/L

13 mg/L

> 100 mg/L

Yield

7.0 mg/L

16 mg/L

7.0 mg/L

73 mg/L

(extrapolated)

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