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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The test item was found to inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata with the following effect values expressed as geometric mean measured concentrations. The EC50 values for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 hours of exposure were 0.733 mg a.i./L and 0.383 mg a.i./L respectively. The ErC10 and NOEC values for inhibition of specific growth were 0.341 and 0.0720 mg a.i./L respectively, and the EyrC10 and NOEC values for yield were 0.207 and 0.0720 mg a.i./L respectively. The most reliable values are considered to be 72h-ErC10 growth rate 0.341 mg a.i./L and the 72h-ErC50 growth rate 0.733 mg a.i./L  (geometric mean measured concentration).

Key value for chemical safety assessment

EC50 for freshwater algae:
0.733 mg/L
EC10 or NOEC for freshwater algae:
0.341 mg/L

Additional information

The toxicity of the test item to the green algae Pseudokirchneriella subcapitata was tested according to the OECD guideline 201 and GLP. The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours.

The study was conducted under static conditions. The algae at the initial concentration of 5.3 × 103 cells/mL were exposed during 72 hours to the following nominal concentrations 0 (control), 0.030, 0.090, 0.27, 0.80, and 2.4 mg a.i./L. The tested concentrations, analysed by High Performance Liquid Chromatography with dual mass spectrometry (LC-MS/MS), were not maintained within 80% of the nominal concentrations during the exposure. Therefore the biological response results are reported based upon the following geometric mean concentrations : 0.00838, 0.0270, 0.0720, 0.260, and 0.993 mg a.i./L, which represented recoveries of 27 to 41% of the nominal concentrations.

All the validity criteria of the guidelines were fulfilled : the pH did not increase more than 1.5 units, the biomass in the controls increased 86 times, the coefficient of variation of average specific growth rates during the whole test period in control replicates was 3% and the mean coefficient of variation in growth rate between adjacent time periods was 9 % for the control replicates.

The EC50 values for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 hours of exposure were 0.733 mg a.i./L and 0.383 mg a.i./L respectively. The ErC10 and NOEC values for inhibition of specific growth were 0.341 and 0.0720 mg a.i./L respectively, and the EyrC10 and NOEC values for yield were 0.207 and 0.0720 mg a.i./L respectively.

Since the validity criteria are fulfilled for the growth rates in the controls, the results of the inhibition of the test item on the growth rate are prefered to the results obtained on the yield. The most reliable value to expressed the inhibition of the test item to the green algae Pseudokirchneriella subcapitata is considered to be 72h-ErC10 growth rate 0.341 mg a.i./L and the 72h-ErC50 growth rate 0.733 mg a.i./L (geometric mean measured concentration).