Cyclohexyl(methyl)amine

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72-h ErC50 and ErC10 values in aquatic algae are 15.4 mg/L and 3.7 mg/L (nominal; non- pH adjusted), respectively.

Additional information

The toxicity towards freshwater algae was determined in a study according to DIN 38412, part 9 (BASF, 1989). In this study, exponentially growing freshwater alga (D. subspicatus) were exposed to nominal test substance concentrations of 0 (control), 1.0, 2.5, 5.0, 10 and 25 mg/L for 72 hours under static conditions. Test concentrations were not analytical verified. Algal biomass and growth rates were recorded at the start of the test and after 24, 48, 72 and 96 hours exposure. In the study a significant increase in pH was noted directly after addition of test substance to the medium. This rise in pH was most pronounced at the higher test concentrations. Therefore, an additional 25 mg/L concentration was tesed after adjustment of pH. After 72 hours exposure inhibition of growth rate was first observed at a test concentration of 5.0 mg/L (7.9%). Inhibition of growth rate increased in a concentration-dependent manner to reach 25.5% and 82.7% at the two highest tested concentrations. Based on these findings the 72 -h ErC50 and the 72 -h ErC10 values were determined at 15.4 and 3.7 mg/L, respectively. The 72 -h NOErC is 2.5 mg/L. The inhibition effect was however less pronounced when the pH of the test medium was adjusted. The 25 mg/L test solution with pH adjustment gave a growth rate inhibition of only 44.9%.

Based on these findings, it may be concluded that the effects observed are attributable, at least in part, to the increased pH rather than to the test substance exposure. In the environment, the effect of the rapidly increasing pH on aquatic organisms depends on the buffer capacity of the aquatic ecosystem. There is a possibility that the emission of the substance could locally increase the pH in the aquatic environment. However, normally the pH of effluents is measured frequently to maintain water quality and the range of pH can be managed properly to prevent adverse effects on the aquatic environment. Therefore, a significant increase of the pH of the receiving water is not expected. Generally the changes in pH of the receiving water should stay within the natural range of the pH, and for this reason, adverse effects on the aquatic environment are not expected.

Nonetheless, as the effect on algae was still visble after neutralisation of pH, for environmental assessment the 72 -h ErC50 and 72 -h ErC10 values of 15.4 and 3.7 mg/L are taken as a worst case approach.