Isobutyric acid

Endpoint summary

Additional information

Valid experimental data are available for the endpoints 6.1.1 - short-term toxicity to fish, 6.1.3 - Short-term toxicity to aquatic invertebrates, 6.1.5 - toxicity to aquatic algae and cyanobacteria and 6.1.7 - Toxicity to microorganisms. For the other endpoints obligatory for REACH, waiving arguments are used.

 

Short-term-toxicity to fish

 

In three individual short term (96 hr) tests, the toxicity of isobutyric acid to three fish species was tested. All tests were performed using the same method (similar to OECD TG 203). Although there are some restrictions (test substance concentration not measured, only four concentrations tested) the studies are assessed as acceptable.

 

The 96 -h LC50 for golden orfe (Leuciscus idus) was 146.6 mg/L (BASF AG, 1989).

The 96-h LC50 for rainbow trout (Oncorhynchus mykiss) was 286 mg/L (Hoechst AG, 1979).

The 96-h LC50 for pumpkinseed (Lepomis gibbosus) was 435 mg/L (Hoechst AG, 1979).

 

There was no adjustment of pH after addition of test substance. In two tests (Hoechst AG), pH-values were measured during the test period. pH-values in the test medium declined in a concentration dependent manner within 24 hours to a pH as low as 4.6. For high test substance concentrations, the observed toxicity may have been influenced by the acidic conditions of the test medium.

 

Long-term toxicity to fish

 

Waiving argument:

According to EACH Annex IX, 9.1, Column 2, the test is not required (CSR does not indicate the need for further investigations).

 

Short-term toxicity to aquatic invertebrates

 

Valid data on the short-term toxicity to aquatic invertebrates is available from one test (BASF AG, 1989).In a second study (Hüls, 1979), a test period of only 24 h was used.

 

BASF 1989

 

Isobutyric acid was tested on the waterflea Daphnia magna in a 48-h acute toxicity 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.

 

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

 

Long-term toxicity to aquatic invertebrates

 

Waiving argument:

According to EACH Annex IX, 9.1, Column 2, the test is not required (CSR does not indicate the need for further investigations).

 

Toxicity to aquatic algae and cyanobacteria

 

Valid data on the toxicity of isobutyric acid to aquatic algae and cyanobacteria is available from one test.

 

BASF AG, 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.

 

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

 

Toxicity to microorganisms

 

From three studies identified, only one test is valid (Schulz, 1997). The documentation of the other two (BASF AG, 1989; Hoechst AG 1979) is insufficient for assessment.

 

Schulz 1997

 

In a valid 40 hour growth inhibition study, test cultures of the cilliate Tetrahymena pyriformis were exposed to graduate concentrations of isobutyric acid. The assay was performed in three independent replicate runs.

 

The IC50 value based on cell density was determined to be 2.15 mg/L indicating low to moderate toxicity of isobutyric acid to aqueous microorganisms (cilliates) (Schultz, 2006).