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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

In a valid growth inhibition test with green algae similar to OECD TG 201, the EC50 of isobutyric acid was determined to be 45.1 mg/L (BASF AG, 1990)

Key value for chemical safety assessment

EC50 for freshwater algae:
45.1 mg/L
EC10 or NOEC for freshwater algae:
29.4 mg/L

Additional information

Hydrolysis studies show that isobutyric anhydride added to water rapidly converts to isobutyric acid. Thererfore, isobutyric acid data is being used by read across for most environmental fate and ecotox endpoints.

The toxicity of isobutyric acid to aquatic algae was investigated in two studies. One study is only reported in a Handbook, thus reliability of the data cannot be assessed (Verschueren, 1983). The second study (BASF AG, 1990) was performed according to a German test guideline (DIN 38412 part 9) which is comparable to OECD TG 201. Reliability is 2.


BASF 1990


In a 72-h acute toxicity study similar to OECD TG 201, cultures of Scenedesmus subspicatus (new name Desmodesmus subspicatus), strain SAG 86.81, were exposed to isobutyric acid at nominal concentrations of 0 (controls), 3.9, 7.8, 15.6, 31.25, 62.5, 125, 250, and 500 mg/L under static conditions. Cell density was recorded at 0, 24, 48 and 72h by fluorescence measurement.


The 72-h EC50 was determined to be 45.1 mg/L (BASF AG, 1990).