2-methylbutyric acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details on endpoint specific justification please see read-across report in section 13 or find a link in cross-reference “assessment report”.

Reason / purpose:

read-across source

Reason / purpose:

assessment report

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

88.1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

65.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Remarks:

acc. to OECD 202, 2004

Conclusions:

Following effect concetrations were derived: 48h-EC50 (Daphnia magna, immobility) = 88.1 mg/L; 48h-NOEC (Daphnia magna, immobility) = 65.2 mg/L.

Executive summary:

The study used as source investigated acute toxicity to aquatic invertebrates. The study results of the source compound were considered applicable to the target compound. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13 or find a link in cross reference “assessment report”.

Description of key information

Following effect concentrations were derived: 48h-EC50 (Daphnia magna, immobility) = 88.1 mg/L; 48h-NOEC (Daphnia magna, immobility) = 65.2 mg/L (mean measured, OECD 202, 2003).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:

88.1 mg/L

Additional information

A reliable key study is available on acute toxicity to aquatic invertebrates (RL1; read-across from isopentanoic acid). The study was conducted according to OECD 202 (1984) and in compliance with GLP. The study was performed with two replicates (n=2) of ten daphnids. Daphnids were exposed to nominal test concentrations of 0 (water control), 7.78, 13.0, 21.6, 36.0, 60.0 and 100 mg/L test substance over a time period of 48 hours in a static test system. Test concentrations were confirmed on days 0 (from bulk solutions) and 2 (from each test vessel). Deviation from nominal concentrations was <20%. Nonetheless, effect concentrations were based on mean measured values: control < LOD (LOD = 0.8 mg/L), 7.5, 13.0, 23.0, 38.1, 65.2, and 110 mg/L for the treatment groups.

Observations were made at 24 and 48 hours for immobility. Observed adverse effects (immobility) were in part pH-related rather than to inherent toxicity of the test compound: In the preliminary study, pH of the test solutions was not adjusted, and no immobility occurred up to the highest concentration at 100 mg/L. The definitive study was conducted with no pH adjustment, and therefore represents a more conservative estimate of toxicity by including pH-effects. The derived test concentrations were: 48h-EC50 = 88.1 mg/L (mean measured), with a 95% confidence interval of 82.9–93.7 mg/L; 48h-NOEC = 65.2 mg/L (mean measured).

The study fulfilled the validity criteria of the guideline (OECD 202 adopted 1984 and 2004). The study was considered reliable and adequate for the environmental hazard assessment for aquatic organisms.