2-ethylhexanoic acid

Long-term toxicity to aquatic invertebrates

Description of key information

Long-term effects for aquatic invertebrates are not expected.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC10

Effect concentration:

19.9 mg/L

Additional information

A study on the toxicity of 2-ethylhexanoic acid (CAS 149 -57 -5) towards aquatic invertebrates was conducted as a non-GLP study according to OECD guideline 211 (Finnish Chemicals Oy., 1997; report no. E2702). Daphnia magna was used as a test organism. The test solutions were renewed 3 times per week. The analytical concentrations were monitored; however, the dilution water interfered with the analytical method for the monitoring of the test item concentrations. However, the test item is considered to be stable based on other available studies (e.g. NITE). After 21 days of exposure a NOEC of 25 mg/L and an EC50 of 75 mg/L were estimated based on the nominal concentrations.

As the study with ethylhexanoic acid is not performed under GLP and with regard to difficulties with the analytical method as well as the reproduction in the control, a study with sodium 2-ethylhexanoate (CAS 19766-89-3) is selected as key study.

Under supervision of the Japanese Ministry of the Environment, a semi-static reproduction test on Daphnia magna was conducted according to OECD 211 under GLP and published in 2002. The test concentrations were analytically verified and deviated less than 20% from the nominal concentrations. Moreover, the study was performed with the salt of the acid (Sodium 2-ethylhexanoate, CAS 19766-89-3) which resembles the acid after neutralization. By that, in this study, the toxicity of the test substance was not influenced by acidic pH effects.The test duration was 21 days. The NOEC for reproduction was determined to be 18 mg/L (NITE, 2002, report no.: A010465 -3).

The data of the original report were re-evaluated using ToxRat v3.3 in order to obtain an EC10, which is not originally reported (BASF SE, 2020). According to REACH Guidance document chapter R.10 Table R.10-1 (Overview of toxicity test endpoints and guidance on derivation of L(E)C50 and NOEC values) an EC10 for a long-term test which is obtained using an appropriate statistical method (usually regression analysis) will be used preferentially.

There has been a recommendation within OECD in 1996 to phase out the use of the NOEC, in particular as it can correspond to large and potentially biologically important magnitudes of effect. The advantage of regression method for the estimation of ECx is that information from the whole concentration-effect relationship is taken into account and that confidence intervals can be calculated. These methods result in an ECx, where x is a low effect percentile (e.g. 5-20%). It makes results from different experiments more comparable than NOECs. The recalculation fulfills the required validity criteria.

The 21 -d EC50 (reproduction) was 43.1 mg/L (95% CL: 34.8 - 53.5 mg/L; based on nominal concentrations, recalculated, BASF SE, 2020). The 21 -d EC10 (reproduction) was determined to be 19.9 mg/L (95% CL: 9.9 - 26.6 mg/L; based on nominal concentrations, recalculated, BASF SE, 2020).