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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

No significant reduction of growth rate or inhibition of yield was recorded at any of the concentrations of Acetoguanamine tested. 

Both the EC50 for growth rate reduction and the EC50 for yield inhibition exceeded an analytically confirmed nominal concentration of 100 mg/l.

The NOEC for growth rate reduction and yield inhibition was >= 100 mg/l.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

The 72 -h EC50 value of Acetoguanamine in Desmodesmus subspicatus determined according to OECD 201 resp. EU C.3.

The study was performed in the test system using five concentrations ranging from 4.6 to 100 mg/L.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 microscope counts. Growth rate µ, area under the growth curve (AUC) and the yield were determined from the cell densities at the respective observation times.Marginal, but statistically significant inhibition of algal growth was observed at the highest concentration of 100 mg/L regarding the endpoint AUC. The other endpoints showed no significant inhibition. 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 recovery after 72 hours was in a range of 102 % up to 105 % of the start concentration. The measured concentrations lay between 90 % and 100 % of the nominal concentration at the beginning of the test and between 93 % and 105 % of the nominal concentration at the end of the test. Therefore, the determination of the results was based on the nominal concentrations. The EC50 values of potassium dichromate were tested in a separate reference test (GLP study no. 201206R301). The values lay within the normal range of the laboratory.

 

The following results for the test item Acetoguanamine were determined:  

Endpoint

NOEC

LOEC

EC50

Growth Rate

≥100 mg/L

> 100 mg/L

> 100 mg/L

AUC

46 mg/L

100 mg/L

> 100 mg/L

Yield

≥100 mg/L

> 100 mg/L

> 100 mg/L