Nonan-4-olide

Toxicity to aquatic algae and cyanobacteria

Description of key information

OECD 201, EU Method C3, GLP, key study, validity 2:
72h-ErC10 = 23.2 mg/L.
72h-ErC50 = 63.5 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

63.5 mg/L

EC10 or NOEC for freshwater algae:

23.2 mg/L

Additional information

One valid key study is available to assess the toxicity of γ-nonalactone to the growth of the unicellular green alga Pseudokirchneriella subcapitata.

This study was performed according to EU method C3 and OECD guideline 201 with GLP statement.

Triplicate algal cultures, with an initial cell density of 1.3 x 10^4/mL were exposed to the test substance dissolved in algal nutrient medium at nominal concentrations of 0.954, 3.05, 9.77, 31.3 and 100 mg/L, for 72 hours.

At the start of the test, the measured levels of the test substance in samples of the test cultures ranged between 66 and 101% of their nominal values. At 0.954 to 9.77 mg/L, the measured concentrations decreased during the test, with measured values between 19 and 48% of nominal at 72 hours (between 29 and 48% of their starting values). At the higher concentrations of 31.3 and 100 mg/L, the measured levels were maintained between 64 and 93% during the 72h exposure period, with measured levels between 98 and 108% of their starting concentrations at study termination. The test substance at 0.954 and 100 mg/L, that had been incubated without algal cells, gave higher measured levels than samples incubated in the presence of algal cells. These results indicated that the presence of agal cells affected the stability of the test substance. The overall mean measured levels of the test substance were 0.524, 2.16, 7.62, 23.0 and 75.1 mg/L.

Cell numbers were counted daily to monitor growth. Abnormally low cell counts were observed at a measured concentration of 0.524 mg/L. Although the reason for the low counts was not identified, it was not considered to be treatment-related as cell counts at measured concentrations of 2.16 and 7.62 mg/L were comparable to that of the control and provided sufficient information to enable the calculation of a NOEC. Therefore, cell counts at 0.524 mg/L were not included in the statistical analysis of the study data. This had not impact on either the integrity or validity of the study.

All validity criteria were fulfilled.

After 72h of exposure to the test substance, the ErC10 and ErC50 were 23.2 mg/L and 63.5 mg/L, respectively. The NOEC for growth rate was 7.62 mg/L.

In conclusion, the 72h-ErC₅₀ at 63.5 mg/L and the 72h-ErC10 at 23.2 mg/L were chosen for the chemical safety assessment.