[No public or meaningful name is available]

Toxicity to aquatic plants other than algae

Description of key information

Available study on analogue substance 1:

ErC50 (Lemna minor, 7d, frond number) 141.40 mg/L (geom. mean of measured conc.)

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.

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

The measured concentrations lay between 27 % and 49 % of the nominal concentrations at the beginning of the test and between 23 % and 61 % of the nominal concentrations at the end of the test. At the end of the test the measured concentration of treatment 1 mg/L was lower than the LOQ. Therefore, the determination of the results was based on the geometric mean of the measured. Half the LOQ (0.05 mg/L) of the 7d value was used to calculate the geometric mean of the 1 mg/L treatment.

The measured concentrations were much lower than the nominal concentration. It is very likely that the solubility in STEINBERG medium is lower than the solubility in demineralized water. Due to a strong colour of the stock solution at the concentration 100 mg/L, presence of undissolved test item could not be observed. This can be stated as uncritical for the outcome of the study because in the lower concentrations no undissolved test item was present and also toxicity was observed and the biological results were based on the real measured concentration.

 

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.