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Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Description of key information

EC50 (30min) 49 mg/L (measured) for activated sludge (similar to OECD 209)

Key value for chemical safety assessment

Additional information

No study on the toxicity of acetic acid, chromium salt, basic to mircoorganisms is available. According to "ECHA Guidance on information requirements and chemical safety assessment, ChapterR.6: QSAR and grouping of chemicals, R. Metals, metal compounds and other inorganic compounds", the hypothesis is that properties are likely to be similar as a result of a presence of a common metal ion, i.e. the trivalent chromium. Thus, results from a study with chromium(III)sulfate by Vankova et al. (1999) are read-across to acetic acid, chromium salt, basic. This study was conducted similar to OECD 209 using activated sludge as test system. Cr(III) was added to test flasks in the form of chromic sulfate at concentrations of 1-100 mg Cr(III)/L. When the required pH values were kept at 7.3 ± 0.2 in accordance with ISO test conditions, precipitation of chromic ions in the form of Cr2O3 x nH2O occurred so that the actual concentration of Cr(III) in solution was considerably lower. Without adjustment of pH no precipitation of Cr(III) occurred but pH dropped to 4.9 at a concentration of 100 mg Cr(III)/L. From the inhibition curve of chromic ions without pH adjustment the mean value of the 0.5-h EC50 (49 mg Cr(III)/L), was calculated, this being the result of combined inhibition by chromic ions and pH. The addition of 49 mg Cr(III)/L caused a drop in pH to approximately 5.8. Reduction of pH to this value alone brings about an approximately 30% inhibition of respiratory activity (data not provided in study). When the pH values were kept at 7.3, most of the chromic ions precipitated. Thus, the EC50 (30min) for growth inhibition based on elemental chromium(III) was determined to be 49 mg/L (measured).