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Short-term toxicity to aquatic invertebrates

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Description of key information

No valid data could be located regarding the short-term toxicity of butyric acid to aquatic invertebrates.
To compensate for this lack of data, information resulting from isobutyric acid as supporting substance is used as substitute.
Supporting substance isobutyric acid: in a valid Daphnia acute immobilization test similar to OECD TG 202, the EC50 of isobutyric acid was determined to be 51.25 mg/L (BASF AG, 1989)
As molecular weights of butyric acid and isobutyric acid are equal, the EC50 determined for isobutyric acid can be taken unchanged for butyric acid.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
51 mg/L

Additional information

The short-term toxicity of butyric acid to aquatic invertebrates was investigated in several studies. Exposure period was only 24 h or there were methodological deficiencies, thus reliability is low. These data cannot be used to determine the short-term toxicity of butyric acid to aquatic invertebrates taking into account recent guideline requirements.

 

As valid data are not available to assess the short-term toxicity of butyric acid to aquatic invertebrates, data for isobutyric acid as supporting substance will be used based on following reasons.

 

Isobutyric acid is closely related to butyric acid. Both compounds are carboxylic acids with the same number of carbon atoms differing only in the position of one methyl-group (branched versus linear carbon chain). Physical properties and chemical reactivity will be quite similar. Main structural feature is the carboxylic acid group, which will have a major impact on the effects of both substances in aquatic systems. Thus, it is justified to use isobutyric as supporting substance in the evaluation of the toxicity of butyric acid to aquatic invertebrates.

 

Supporting substance isobutyric acid

 

The study was performed according to a German test guideline (DIN 38412, part 11) which is comparable to OECD TG 202. Reliability is 2.

 

BASF AG 1989

 

Isobutyric acid was tested on the waterflea Daphnia magna in a 48-h acute immobilization test similar to OECD TG 202 under static conditions at concentrations of 0 (water control), 15.625, 31.3, 62.5, 125, 250, and 500 mg/L. Immobilization and other toxic effects were observed 3, 6, 24, and 48 h after initiation of the test.

 

The 48-h EC50 was determined to be 51.25 mg/L (BASF AG, 1989).

 

Butyric acid: short-term toxicity to aquatic invertebrates

 

As the molecular weight of both substances is the same, toxicity values have not to be converted to allow for different compounds.

 

The 48-h EC50 for butyric acid is assessed to be 51 mg/L.