Reaction mass of 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-5-yl isobutyrate and 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-6-yl isobutyrate

Toxicity to aquatic algae and cyanobacteria

Description of key information

Cyclabute and its EC50 and NOEC for algae are 1.95 and 0.163 mg/l based on read across from Cyclobutanate which was tested in an OECD TG 201.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.95 mg/L

EC10 or NOEC for freshwater algae:

0.163 mg/L

Additional information

The executive summary of the Cyclobutanate test is presented here. The read across justification is presented in the Aquatic toxicity Endpoint summary.

Cyclobutanate and its algae toxicity

For assessing the toxicity of Cyclabute towards algae information from Cyclobutanate is used. The acute toxicity of Cyclobutanate towards Scenedesmus subspicatus was investigated according to OECD guideline 201 under GLP. Algal cells were exposed to nominal concentrations of 0.81, 1.63, 3.25, 6.5 and 12.9 mg/l and were observed for 72 hours. In a preliminary study, the measured concentration at t=0 were in line with the nominal ones (80-120%). After 72h the test concentrated diminished with < 40%, during storage in light or dark or with or without algae. In the main test at 72h the test concentrations were all below the LoQ.  The result show that the EC50 at t=24 h is the same as at 72h and no recovery takes place after disappearance of the parent substance. This leads to the conclusion that Cyclobutanate has a direct effect on algae and therefore the toxicity values based on the geometric mean and the LoQ was not considered justified. The toxicity values have been based on the concentrations measured in the preliminary stability tests. This means that the NOEC results in a value of 0.163 (1.63 x 0.1, being worst case because at 1 mg/l the loss was 90% but at 3.25 only 40%). The EC50 results in a value 1.95 mg/l (Taking the EC42 as the EC50 and 40% loss on the nominal concentration: 3.25 x 0.6)