Reaction mass of cyclohexanol and cyclohexanone

Endpoint summary

Description of key information

Endpoint	value
Short-term toxicity to fish	LC50 (96 h) ≥ 527 mg/l (cyclohexanone)
Long term toxicity to fish	No data available
Short-term toxicity to aquatic invertebrates	EC50 (48 h) = 366.02 mg/l (reaction mass)
Long-term toxicity to aquatic invertebrates	NOEC = 0.953 mg/l (cyclohexanol)
Toxicity to aquatic algae and cyanobacteria	EC50 (72h) = 32.9 mg/l (cyclohexanone) EC10 (72h) = 3.56 mg/l (cyclohexanone)
Toxicity to microorganisms	EC50 > 1000 mg/l (cyclohexanone)

Additional information

Short-term toxicity to fish

The short-term toxicity of the single components of the test item was assessed in two different experimental studies with the Fathead minnow according to the test method of the U.S. EPA Committee on Methods for Toxicity (1975) for 96 h. The LC50 (96 h) was 704 mg/l for cyclohexanol (Brooke, 1984) and 527 mg/l respectively 732 mg/l for cyclohexanone (two tests were performed under the same conditions) (Brooke, 1984). The toxicity of the mixture of both components is assumed to be in the same range as for the single components so the LC50 (96 h) >= 527 mg/l can be derived.

Long term toxicity to fish

The hazard assessment of cylcohexanone and cyclohexanol reveals neither a need to classify the substance as dangerous to the environment, nor is it a PBT or vPvB substance. Moreover, based on the information on short-term aquatic toxicity and the available long-term studies with invertebrates and green algae as well taking into account the known non-specific mode of action, there are no further indications that the substance may be chronic hazardous to the environment. Therefore, and for reasons of animal welfare, a long-term toxicity study in fish is not provided.

Short-term toxicity to aquatic invertebrates

The acute toxicity of the reaction mass to aquatic invertebrates was assessed in an experimental study according to OECD 202 (Rhodia, 2009). The test organisms were exposed to the nominal initial concentrations of 0, 125, 250, 500, 1000, 2000 mg/L (test item) for 48 h and the immobility of the test organisms was observed during the test period. As reference substance potassium dichromate was used. The EC 50 (24 h) for the reference substance was 1.39 mg/l. The EC50 (48 h) for the test item was 366.02 mg/l.

Long-term toxicity to aquatic invertebrates

The NOEC for the reaction mass was derived from the most sensitive value from the single components. The NOEC for cyclohexanol is more sensitive (0.953 mg/l) than the with QSAR predicted NOEC for cyclohexanone (26.6 mg/l) and it resulted from an experimental study. Therefore, the NOEC for the reaction mass can be derived from the NOEC of the single component. By choosing the most sensitive value of one component the worst-case scenario for the mixture is covered. In order to this, the NOEC for the reaction mass is 0.953 mg/l.

Toxicity to aquatic algae and cyanobacteria

No experimental study with the mixture was conducted. Since there are reliable experimental studies for the single components of the mixture, the most sensitive value of both can be used to derive the value for the mixture assuming a worst-case scenario. The EC50 (72h) for cyclohexanone (32.9 mg/l) was lower than the value for cyclohexanol (>500 mg/l). Therefore, it is the more sensitive endpoint and is chosen to derive the EC50 and EC10 for the mixture. Assuming a worst-case scenario the EC50 (72h) for the reaction mass is 32.9 mg/l and the EC10 (72h) 3.56 mg/l.

 Toxicity to microorganisms

No experimental study with the mixture was conducted. Since there are reliable experimental studies for the single components of the mixture available, the most sensitive value of both can be used to derive the value for the mixture assuming a worst-case scenario. In both studies with the single components of the mixture no relevant inhibition of the respiration rate was measured therefore an EC50 > 1000 mg/l can be assumed also for the mixture.