Registration Dossier
Registration Dossier
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EC number: 205-743-6 | CAS number: 149-57-5
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriately low concentrations.
Key value for chemical safety assessment
- EC50 for microorganisms:
- 112 mg/L
- EC10 or NOEC for microorganisms:
- 71.7 mg/L
Additional information
To assess the toxicity of 2-ethylhexanoic acid (CAS 149 -57 -5) to microorganisms, experimental data for the substance are available.
The key study is a growth inhibition test according to Bringmann-Kuehn with Pseudomonas putida, conducted with 2-ethylhexanoic acid by BASF AG (1988, report no. 0949/88). The 17-h EC10 was determined to be 71.7 mg/L; the 17-h EC50 was 112 mg/L.
The effect of 2-etylhexanoic acid is most likely caused by the low pH of the test solutions. According to the guideline, the test solutions should be set to pH 7.4±0.3. In this study, the pH decreased from pH 6.9 at the lowest test concentration of 31.25 mg/L to pH 4.1 at 1000 mg/L. Therefore, it is plausible that the observed inhibition is mainly due to the low pH induced by the substance. Up to a concentration of 62.5 mg/L or a pH of 6.6, no significant inhibition was observed. At 125 mg/L, the pH was already below 6 (pH 5.5) and inhibited growth by 72%. At test concentrations >= 250 mg/L, no growth was observed.
Based on the available experimental data, it can be concluded that inhibition of the degradation activity of activated sludge is not anticipated when the substance is introduced in appropriate low concentrations.
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