Cyclohexyl(methyl)amine

Short-term toxicity to fish

Description of key information

The 96-h LC50 value in fish (L. idus) is >100 mg/L (nominal).

Additional information

Two nearly identical short-term fish studies are available for the substance. In these studies the short-term toxicity to freshwater fish was determined according to DIN 38 412 part 15 (BASF, 1980; BASF, 1983). In both studies groups of 10 golden orfe (Leuciscus idus) were exposed to nominal test concentrations of 0 (control), 6.8, 10.0, 14.7, 21.5, 31.6, 46.4, 68.1 and 100 mg/L for 96 hours under static conditions. Test concentrations were not analytical verified. Observations for mortalities and symptoms of toxicity were made regularly throughout the test. In both studies 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 100 mg/L concentration was tesed after adjustment of pH.

In the first BASF study after the 96 -h exposure period no mortality was recorded up to a test concentration of 31.6 mg/L. At a test concentration of 46.4 mg/L 100% mortality was recorded after 4 hours exposure. At this test concentration sub-lethal effects after 1 hour consisted of gasp, stagger and lateral position. At the two highest test concentrations 100% mortality was observed after 1 hour exposure already. Based on these findings the 96 -h LC50 value is reported as 32 - 46 mg/L (nominal). Especially at the start of the test, right after test solution preparation, a significant increase in pH was noted. From a test concentration of 21.5 mg/L the pH gradually increased from 9.1 to 10.6 with increasing test concentrations. In a parallel experiment in which the pH was neutralised with ca. 10% sulfuric acid, no mortality or other symptoms were observed at 100 mg/L test substance.

The second study is a near copy of the first, the main differences being that 20% hydrochlorid acid instead of 20% sulfuric acid is used for pH adjustment (BASF 1983). In this second study, after the 96 -h exposure period no mortality was recorded up to a test concentration of 21.5 mg/L. At a test concentration of 31.6 mg/L 1 death occured after 4 hours exposure until the end of the test. At the three highest test concentrations 100% mortality was observed after 4 hours exposure. Based on these findings the 96 -h LC50 value is reported as 31.6 - 46.4 mg/L (nominal). In this study also, no mortality or other symptoms were observed in the 100 mg/L test group when pH was neutralised.

Based on these findings, it may be concluded that the effects observed are completely attributable 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.

Therefore, the 96 -h LC50 in fish is determined to be >100 mg/L (based on nominal concentrations).