Reaction mass of 2-(phosphonooxy)ethyl acrylate and bis[2-(acryloyloxy)ethyl] hydrogen phosphate

Toxicity to aquatic algae and cyanobacteria

Description of key information

The EC50 for cell growth inhibition (EBC50: 0-72h) and EC50 for growth rate reduction (ERC50: 0-72h) based on TWA concentrations were determined to be 90 and 165 mg/L, respectively, while the NOEC for both cell growth inhibition and growth rate reduction based on TWA concentrations was 39 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

165 mg/L

EC10 or NOEC for freshwater algae:

39 mg/L

Additional information

A study was conducted to assess the toxicity potential of the read across substance (2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, reaction products with phosphorus oxide (P2O5)) to algae according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. In the range-finding test, exponentially growing algal cultures were exposed to test substance concentration range of 0.1 to 100 mg/L increasing by a factor of 10. In addition, a blank and treatment-control (with adjusted pH) were tested. The results showed that the EC₅₀for both cell growth inhibition and growth rate reduction were above nominally 100 mg/L. The project was continued with a final test exposing exponentially growing algal cultures to a blank-control and nominal test substance concentrations of 10, 20, 40, 80 and 160 mg/L. In addition, a treatment-control with pH adjusted to that of the highest test substance concentration was included to correct for possible pH-related effects on algal cell growth at 160 mg/L. The initial algal cell density was 10^4cells/mL. The total test period was 72 h. Samples for analyses were taken at the start, after 24 h of exposure and at the end of the 72 h test period. Analyses showed that the measured concentrations at the start of the test were in agreement with nominal. Analysis was only considered for the nominal concentrations of 40, 80 and 160 mg/L, which were essential for determination of the toxicity parameters. Measured concentrations were 38 mg/L (96%), 73 mg/L (91%) and 149 mg/L (93%) at the expected nominal concentrations of 40, 80 and 160 mg/L, respectively. During the 72 h exposure period the measured concentrations decreased by more than 20% below initial. Based on these results, the Time Weight Average (TWA) exposure concentrations were calculated to correspond to 17, 39 and 114 mg/L, respectively. The study met the acceptability criteria prescribed by the protocol and was considered valid. The EC50for cell growth inhibition (EBC50: 0-72h) and EC50for growth rate reduction (ERC50: 0-72h) based on TWA concentrations were determined to be 90 and 165 mg/L, respectively, while the NOEC for both cell growth inhibition and growth rate reduction based on TWA concentrations was 39 mg/L (Migchielsen MHJ, 2004).