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Toxicity to aquatic plants other than algae

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Description of key information

ErC50 (Lemna minor, 7d, frond number) > 93.1 mg/L (meas. (geom. mean))

Key value for chemical safety assessment

Additional information

This study was performed in order to evaluate the toxicity of tehe test item towards Lemna minor following the OECD Guideline 221 (2006).The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L (nominal concentration). Incubation time was 7 days. The frond number of each replicate was determined at the beginning, at day 2 and 5 during the test and at the end of the experiment. Additionally, the dry mass of 12 representative fronds was determined at the beginning of the experiment. At the end of the experiment the dry mass of each replicate was determined.

Growth rate µ and the yield were determined from the frond number and the drymass at the respective observation times.

Due to contamination, the lowest concentration was excluded from the evaluation. Although fewer concentrations were taken into account, the statistical significance of the results is still given.

At the start and at the end of the test, the content of the test item in the test solutions was determined using a photometric method.

The measured concentrations lay between 91 % and 103 % of the nominal concentrations at the beginning of the test and between 65 % and 129 % of the nominal concentrations at the end of the test. Therefore, the determination of the results was based on the geometric mean of the measured concentrations (cf. OECD Guideline No. 221 §47). The decrease of the test item could be explained by the inclusion of the test item in the plants. However, this is only an assumption.

The 7d-EC50s of 3,5-Dichlorophenol (1,3-Dichloro-5-hydroxybenzene, C6H4Cl2O, CAS-No. 591-35-5) were determined in a separate reference test. The EC50value of the growth rate lay within the desired range of 1.7 - 5.7 mg/L, mentioned in the paper “OECD Lemna Growth Inhibition Test, Development and ring testing of draft OECD test guideline”, Research and Development Technical Report EMA 003, page 34.

The ErC50 based on frond number for the test item was found to be > 93.1 mg/L  (geom. mean corresponding to nominal concentration of 100 mg/L).