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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Very acute toxic to aquatic algae.

Key value for chemical safety assessment

Additional information

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

An acute toxicity study was conducted with Scenedesmus subspicatus (BASF AG 1994) according to 79/831/EEC, C.3 using a static test system. 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. The 72-hour EC50 values were: EbC50 = 0.04 mg/L, ErC50 = 0.13 mg/L. The NOEC and LOEC were determined to be 0.008 and 0.016 mg/L, respectively.

In addition, there is another toxicity study with Scenedesmus subspicatus conducted according to 92/69/EEC, C.3 using a static design (Huels AG 1995). Since the analytical recovery rates were >80 %, all effect values were based on nominal concentrations. The 72-hour EC50 values were as follows: EbC50 = 0.06 mg/L, ErC50 = 0.205 mg/L. The NOEC was determined to be <0.01 mg/L.

 In addition, an acute toxicity study was conducted with Selenastrum capricornutum 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 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.

In conclusion, based on the results of the structural analogue acrylic acid, a very acute toxicity to aquatic algae of sodium acrylate is to be expected, too.