Methylcyclohexane

Short-term toxicity to fish

Description of key information

LC50 (96h) = 2.07 mg/L (Oryzias latipes, OECD 203, time weighted average concentration)
LC50 (96h) = 5.8 mg/L (Morone saxatilis, method similar to OECD 203, mean measured concentration)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2.07 mg/L

Marine water fish

Marine water fish

Effect concentration:

5.8 mg/L

Additional information

Three studies investigating the short-term toxicity of methylcyclohexane (CAS No. 108 -87 -2) to fish are available. Two studies were conducted by Japanese authorities using the freshwater species Oryzias latipes as test organism. The key study, was conducted under GLP conditions according to the Circular on Test Methods of New Chemical Substances (Japan), Fish, acute toxicity test (2005). This method is comparable to the OECD 203 (1992). A 96 h-LC50 value of 2.07 mg/L on the basis of time weighted average concentrations was determined for Oryzias latipes under semi-static test conditions. There was a significant loss of the test substance due to volatilisation during the preparation of test solution. Even if the test solutions were prepared freshly, the measured concentrations ranged approximately 30% of nominal. To minimize further substance losses during the test, the test was performed in a closed system without headspace. In this way, 82 – 101% of the initial measured concentrations remained stable during the 24 hour intervals.

A supporting study observed a similar LC50 value of 5.02 mg/L (nominal); however, using a shorter exposure time of 48 h (METI, 1986). A further study (Benville et al., 1985), which investigated the toxicity of the test substance to fish (Morone saxatilis) under marine conditions, determined a comparable 96h-LC50 of 5.8 mg/L (mean measured concentration).