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Toxicity to microorganisms

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Description of key information

Based on results of the structural analogue acrylic acid (CAS# 79-10-7) the inhibition of degradation activity of activated sludge is not anticipated when sodium acrylate is introduced into biological treatment plants in appropriately low concentrations.

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Additional information

No data on toxicity to microorganisms are available for sodium acrylate. Therefore, results from investigations on the structural analogous substance acrylic acid were taken into account for the assessment of toxicity to microorganisms of sodium acrylate.

In a test with domestic activated sludge the inhibition of oxygen consumption was examined according to guideline ISO 8192 (BASF AG, 1993). After 30 minutes oxygen uptake was inhibited by 16 % at 500 mg/L and by 21 % at 1000 mg/L, the highest concentration tested. Thus, the EC20 was determined to be 900 mg/L.

Another very sensitive microorganism to acrylic acid was the protozoan Chilomonas paramaecium with a 48-hour Toxicity Threshold of 0.9 mg/L determined in a cell multiplication inhibition test (Bringmann 1980). Although this species does not influence the degradation processes in a wastewater treatment plant itself, it is necessary for a proper function of a WWTP; therefore, the result of this study was used for derivation of the PNEC STP in the EU Risk Assessment. 

In conclusion, based on the results of the structural analogue acrylic acid, inhibition of the degradation activity of activated sludge is not anticipated when sodium acrylate is introduced in appropriately low concentrations in WWTPs.