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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 (72 h, growth rate) = 0.13 mg/L (nominal) (Scenedesmus subspicatus, 79/831/EEC, C.3)

EC50 (72 h, growth rate) = 0.205 mg/L (nominal) (Scenedesmus subspicatus, 92/69/EEC, C.3)

EC50 (96 h, cell number) = 0.17 mg/L (nominal) (Selenastrum capricornutum, OECD TG 201)

EC10 (72 h, growth rate) = 0.03 mg/L (nominal) (Scenedesmus subspicatus, 92/69/EEC, C.3)

EC10 (72 h, growth rate) = 0.031 mg/L (nominal) (Scenedesmus subspicatus, 92/69/EEC, C.3)

Key value for chemical safety assessment

EC50 for freshwater algae:
0.13 mg/L
EC10 or NOEC for freshwater algae:
0.03 mg/L

Additional information

An algal growth inhibition study was conducted with Scenedesmus subspicatus (BASF AG 1994) according to 79/831/EEC, C.3 using a static design. Nominal exposure concentrations were 0.0078, 0.016, 0.031, 0.063, 0.13, 0.25, 0.5, 1, 10, 100 (not neutralised) and 100 (neutralised) mg/L. Analytical recovery rates were between 94 – 101 % of nominal concentrations. Therefore, all effect values were based on nominal test substance concentrations. For determination of acute ecotoxicity of acrylic acid, the EC50 value for growth rate was determined. For the assessment of chronic ecotoxicity of acrylic acid, the corresponding EC10 value was calculated (according to Guidance on Information Requirements and Chemical safety - R.10). The relevant 72-hour effect concentrations were determined to be EC50(growth rate) = 0.13 mg/L and EC10(growth rate) = 0.03 mg/L.


In addition, there is another algal growth inhibition study with Scenedesmus subspicatus conducted according to 92/69/EEC, C.3 using a static design (Huels AG 1995). Nominal test concentrations were 1, 2.5, 5, 10, 20, 40 mg/L. Since the analytical recovery rates were > 80 %, all effect values were based on nominal concentrations. The relevant 72-hour effect concentrations were determined to be EC50(growth rate) = 0.205 mg/L and EC10(growth rate) = 0.031 mg/L.


Then, an acute toxicity study was conducted with Selenastrum capricornutum (BAMM, 1990) according to EPA OTS 797.1050 and OECD Guideline 201 using a static design. Nominal exposure concentrations were 0.13, 0.25, 0.5, 1.0, 2.0 mg/L. At time 0, the analyzed concentrations were 0.15, 0.26, 0.49, 0.96, 1.9 mg/L. After 96 hours, analyses of the test media were all below the limit of detection. The loss of acrylic acid was considered to be related to volatility and/or adsorption to the vessels and the algae. Since such a loss of test substance did not occur in any of the other freshwater algae tests, this study has to be regarded as valid with restrictions.

Growth inhibition of algae was observed at all concentrations from 24 through 96 hours. Based on cell counts, the 72 and 96 hour EC50 values were 0.14 and 0.17 mg/L (nominal), respectively. The 96-hour NOEC was < 0.13 mg/L.

Several publication reported the effects of acrylic acid on freshwater and saltwater algae. All reported species showed effects but were not the most sensitive algae species.