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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Isobutyl acrylate is acutely toxic to freshwater algae. The 72-hour EC50, EC10 and NOEC (growth rate) was determined to be 5.28 mg/L, 2.09 mg/L and 0.82 mg/L (meas. arithm. mean), respectively.

Key value for chemical safety assessment

Additional information

Experimental data are available for the target substance isobutyl acrylate (CAS 106 -63 -8) as well as for the source substances tert-butyl acrylate (CAS 1663 -39 -4) and n-butyl acrylate (CAS 141 -32 -2).

isobutyl acrylate

A GLP compliant acute toxicity study was conducted with Desmodesmus subspicatus (BASF AG 2002a) according to OECD Guideline 201 using a static design. Nominal exposure concentrations were 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50, 100 mg/L. The analytical recovery rate was in all analysed test solutions below 80 %. Thus, the effective concentrations were based on the median analytical recovery rate of 52.8 % (all measurements between 0 and 72 h). 72-hour EC50 values for growth rate and biomass were 5.28 and 3.18 mg/L (measured), respectively. The 72 -hour NOEC was determined to be 1.65 mg/L.

In addition, there is an older study with Scenedesmus subspicatus conducted according to the national German standard DIN38412, part 9 without analytical monitoring (BASF AG, 1989). EC50 values after 72 hrs exposure were calculated to be 23.8 mg/L (biomass) and 24.7 mg/L (growth rate), respectively. This study does not take the possible decrease in test concentration by volatilisation of the substance into consideration and therefore is not suitable for the assessment.

n-butyl acrylate

An acute toxicity study was conducted with n-butyl acrylate in Selenastrum capricornutum (BAMM, 1990) according to OECD Guideline 201 using a static design. Based on the arithmetic means for the measured exposure concentrations a 96-hour EC50 and NOEC (cell number) value of 2.65 mg/L and < 1.8 mg/L, respectively, was determined.

tert-butyl acrylate

The growth inhibiting effect of tert-butyl acrylate to Raphidocelis subcapitata was assessed in a GLP-compliant test according to OECD TG 201. The substance was tested at nominal concentrations of  0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50, 100 mg/L. A negative control (without test item) and a positive control with the reference compound potassium dichromate run in parallel. The test item concentrations were analyticaly verfied to be in the range of 20.51 -  53.03 % of nominal at the start of the test and 15.38 -  42.50 % of nominal after 72 hours. Since the analytical recovery rate was in all analysed test solutions below 80 % the test results are based on measured (arith. mean) concentrations. The 72-hour EC50 and EC10 (growth rate) for the test item were determined to be 14.6 mg/L and 5.61 mg/L, respectively (BASF AG, 2002b).

Conclusion

Since isobutyl acrylate is readily biodegradable and moderately volatile, only test results from studies with analytical monitoring were used for the hazard assessment for freshwater algae. Based on the most relevant and reliable information (BASF AG, 2002a) the 72-hour EC50, EC10 and NOEC (growth rate) is considered to be 5.28 mg/L, 2.09 mg/L and 0.82 mg/L (meas. arithm. mean), respectively. These results are supported by data from the structural analogue n-butyl acrylate. However, in a 72 -hour test with the structural analogue tert-butyl acrylate (BASF AG, 2002b) effects to the growth rate were detected at slightly higher test item concentrations (EC50: 14.6 mg/L; EC10: 5.61 mg/L) and EC10 (growth rate).