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EC number: 946-819-5 | CAS number: -
Toxicity to aquatic plants other than algae
Administrative data
Link to relevant study record(s)
Description of key information
ErC50 (Lemna minor, 7d,frond number)> 27.81 mg/L (measured initial values, corresponding to 100 mg/L nominal)
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 (test system Lemna minor) 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. At the start and at the end of the test, the content of the test item in the test solutions was determined using Photometer. 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
Significant inhibition of plant growth was observed at the following concentrations: 32 - 100 mg/L (nominal). The measured concentrations lay between 20 % and 28 % of the nominal concentrations at the beginning of the test and between 6 % and 13 % of the nominal concentrations at the end of the test. The measured concentrations decrease during the test although the test item was stable during validation. The decrease of the measured concentration of test item can be explained by adsorption and/or uptake of the test item; this is indicated by the observation that some parts of the plant showed a red coloration. Part of the test item was removed with the plants from the test system before the analytical determination. Therefore, the measured initial values are used for statistical evaluation. This procedure is analogous to the OECD Guideline 201 (§40) of the algae test.
All EC50values (except from yield dry mass) are above the solubility limit and are therefore given as a range.
The EC50 of positive control value 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”.
The following results for the test item were determined:
| Endpoint | NOEC | LOEC | EC10 | EC50 |
| Growth Rate frond number | 2.35 mg/L (nominal 10 mg/L) | 8.21 mg/L (nominal 32 mg/L) | 8.64 mg/L | > 27.81mg/L (nominal 100 mg/L) |
| Yield frond number | 2.35 mg/L (nominal 10 mg/L) | 8.21 mg/L (nominal 32 mg/L) | 2.41 mg/L | > 27.81mg/L (nominal 100 mg/L) |
| Growth Rate dry mass | 2.35 mg/L (nominal 10 mg/L) | 8.21 mg/L (nominal 32 mg/L) | 5.70 mg/L | > 27.81 (nominal 100 mg/L) |
| Yield dry mass | 2.35 mg/L (nominal 10 mg/L) | 8.21 mg/L (nominal 32 mg/L) | 2.38 mg/L | 25.55 mg/L |
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