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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when acrylic acid is introduced into biological treatment plants in appropriately low concentrations.

EC20 (30 min) = 900 mg/L (domestic activated sludge, ISO 8192)

NOEC (30 min) = 100 mg/L (domestic activated sludge, ISO 8192)

TTC = 0.9 mg/L (Chilomonas paramaecium, cell multiplication inhibition test)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

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. The NOEC was determined to be 100 mg/L.


In addition, there are several publications concerning acute toxicity of acrylic acid towards microorganisms. Radix et al. (1999, 2000) reported a NOEC for Vibrio fisheri of 6.25 mg/L (nominal) determined in the Microtox Chronic Toxicity Test (bioluminescence). Seward & Schultz (1999) found the IC50 for Tetrahymena pyriformis in the Tetratox assay to be 49.85 mg/L for acrylic acid.


But the most 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 and therefore, was used for derivation of the PNEC STP in the EU Risk Assessment (2002).


Taking all these test results into consideration, inhibition of the degradation activity of activated sludge in a WWTP is not anticipated when the substance is introduced in appropriately low concentrations in WWTPs.