Ceraphyl 55

Endpoint summary

Additional information

The acute toxicity of Ceraphyl 55 to the Rainbow Trout (Oncorhynchus mykiss) was determined in a GLP-compliant, OECD guideline 203 study (Springborn Smithers 2004). The acute toxicity of Ceraphyl 55 to Daphnia magna was determined in a GLP-compliant, static acute toxicity study following OECD guideline 202 (Springborn Smithers 2004). The chronic toxicity of Ceraphyl 55 to Daphnia magna was determined in a GLP-compliant, 21 day flow-through study following OECD guideline 211 (Wildlife International 2008). The toxicity of Ceraphyl 55 to algae was determined in a GLP-compliant, static growth inhibition study following OECD guideline 201 (Springborn Smithers 2004).

The acute toxicity of Ceraphyl 55 to fish, invertebrates and algae was tested at nominal concentrations of 0.0063, 0.013, 0.025, 0.050 and 0.10 mg/L alongside a control and solvent control. The highest concentration tested approximated the water solubility limit of Ceraphyl 55 in the test media. No toxicity to fish or algal growth was observed at the highest concentration tested and therefore Ceraphyl 55 is considered not to be toxic to fish or algae at the limit of solubility. Immobilisation of Daphnia was observed in the two highest concentrations tested in the acute study and the 48 hour EC50 was determined to be 0.012 mg/L for Daphnia. The chronic toxicity of Ceraphyl 55 to Daphnia magna gave a 21 day NOEC of 0.047 mg/L, a 21 day LOEC of 0.096 mg/L and a calculated MATC of 0.067 mg/L.

The measured concentrations in the long-term toxicity to Daphnia study conducted by Wildlife International (2008) are higher, in relation to the nominal concentrations used, than the short-term toxicity to fish and Daphnia and the algae toxicity tests conducted by Springborn Smithers (2004). The acute Daphnia results were based on the mean concentrations under static conditions, whilst the chronic study was based on the mean concentrations under flow through conditions, used to maximize the exposure concentrations. It is likely therefore that the difference in percentage of the nominal concentrations observed in the measured concentrations is due to the difference in study design.

In the acute study, it was noted in the preliminary test that the very flat dose response and the preparation method (dilution of the 100 mg/L solution) indicated that undissolved test material could have been present. The presence of a surface film was also indicated from the trapped Daphnia in the 100, 10 and 1 mg/L exposure solutions. As a result of this, water solubility trials were conducted and based on the results, and in consultation with the sponsor, the definitive concentration range was chosen in order to limit the amount of undissolved test material present and the potential entrapment of the Daphnia.

The acute study states that the test solutions were clear and colourless with no visible undissolved test item and similarly, the chronic study states that test solutions were clear and colourless with no visual evidence of precipitation. The surface tension study indicates that micelle formation at the higher concentration tested (5 mg/L) is likely to have given rise to the increase in surface activity. However, at the lower concentration (2 mg/L), Ceraphyl 55 is not considered to be surface active. Given that the concentrations used in the aquatic toxicity tests were around a factor of 10 lower than the concentrations at which Ceraphyl 55 is considered not to be surface active, surface active properties may be less likely.

The test concentrations used in the chronic study were based on the results of a previous toxicity test and selected in consultation with the sponsor. It was also noted in the chronic study that “a small amount of a clear and colourless surface film was evident in the diluter mixing cups supplying solution to the Ceraphyl 55 test chambers at test initiation and termination” but no further discussion on the potential effects of this solution on the organisms is provided. In the chronic Daphnia study, the EC50 for reproduction was determined to be lower than that for mortality (immobilisation), though the NOEC for both of these endpoints was the same. This difference in mortality and reproduction effect concentrations indicates that immobilisation through the physical effects of micelles is not expected to be significant.