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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Read-across, EU Method C.3, OECD Guideline 201, GLP, key study, validity 2:
72h-ErC50 = 14.0 mg/L (95% confidence interval: 11.3 -17.5 mg/L).
72h-ErC10 = 4.6 mg/L (95% confidence interval: 2.8 -6.2 mg/L).
72h-NOECr = 1.7 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
14 mg/L
EC10 or NOEC for freshwater algae:
1.7 mg/L

Additional information

To assess the toxicity of the registered substance, 2 -pentylcyclopentan-1-one, to aquatic algae, one valid experimental study is available.


This GLP study, assessed as a key study, was performed on a read-across substance, 2 -pentylcyclopentan-1-ol, according to EU Method C.3 and OECD Guideline 201. Both compounds (the registered substance and the read-across substance) acting with a non-polar narcotic MOA (Class 1) and are structurally related, in that each has an alkyl chain with five carbon (pentyl) with a cyclopentane ring. Both compounds contain a 2 -pentylcyclopentane skeleton. The cyclopentane ring is associated with a ketone functional group for the registered substance and with an alcohol functional group for the read-across substance.

In this study, the algae Pseudokirchneriella subcapitata were exposed to the test substance (nominal concentrations: 0.32, 1.0, 3.2, 10, 32 and 100 mg/L) in a static condition during 72 hours, to assess the influence of the test substance on the growth of the freshwater green algal species. Additionally, a control group was tested in parallel. Since the test substance was determined to be volatile, the test was performed in a closed system to avoid losses of the volatile substance. The measured concentrations of the test substance in the test media samples were between 63 and 107% of nominal values at the start of the test. During the test period of 72 hours, a decrease of test substance concentration in the test media occurred at least in the lower test concentrations. The mean measured test concentrations (calculated as the geometric means of the concentrations measured at the start and the end of the test) were between 21 and 101% of nominal values. The biological results were related to the mean measured test item concentrations, which were 0.10, 0.21, 1.7, 6.6, 22 and 101 mg/L, respectively, corresponding to the nominal test item concentrations mentioned above. Unfortunately, the geometric spacing of critical measured concentrations between 15 and 72% effects was greater than a factor of 3.2 as recommended in the guideline due to substance loss at the lower concentration. Based on the growth rate, the 72h-ErC10 and 72h-ErC50 were determined to be 4.6 mg/L (95% confidence interval: 2.8 -6.2 mg/L) and 14.0 mg/L (95% confidence interval: 11.3 -17.5 mg/L), respectively. The 72h-NOEC was 1.7 mg/L.

This supporting substance is considered adequate for read-across purposes based on structural similarity, on similar basic physico-chemical properties and similar environmental profile as well as the same mode of action between the registered substance and the analogue material used. In addition, as the log Kow value of the analogue material is slightly greater than the registered substance, the read-across approach is considered as a worst case scenario (see IUCLID section 13 for justification).