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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Description of key information

In duckweed (L. gibba), the 7-d EC50 and EC10 values for growth rate (based on frond numbers) are both >900 mg/L after correction for the percentage active ingredient in the tested substance.

Key value for chemical safety assessment

Additional information

The toxicity to aquatic plants other than algae was determined in a study according to OECD guideline No 221 and in compliance with GLP criteria (BASF, draft report).

In this study 3 replicates of 3 uniform, healthy-looking duckweed (L. gibba), with 3 fronds each, were introduced in test vessels containing test substance at 0 (control), 0.013, 0.064, 0.32, 1.6, 8.0, 40, 200 and 1000 mg/L. Plants were exposed for 7 days under semi-static conditions (renewal of test solutions at days 3 and 5). Test concentrations were analytically verified at the start and the end of the test and before and after renewal, and all measured test concentrations were found to be well within ±20% of nominal. Therefore, effect values are expressed as nominal. In order to quantify the test item related effects on vegatitive growth rate and yield, the total number of fronds in each replicate was counted on days 3 and 5 and exposure termination. At the end of the test period, dry weight of all plants was determined. Throughout the test morphological indicators of plant development were scored. These obseractions included shape and appearance of fronds, colony break-up or loss of buoyancy, root length and appearance. Based on frond numbers no significant effects on growth rate and yield were observed up to a concentration of 40 mg/L. Growth rate and yield were affected at higher concentrations to reach a maximum inhibition of 12% and 32.1%, respectively at the 1000 mg/L test concentration. Based on dry weight, no effects on growth rate and yield were observed up to a concentration of 1.6 mg/L. At higher concentrations inhibition of growth rate and yield increased concentration dependently up to 21.6% in case of growth rate and 54.1% in case of yield. Based on these findings, the 7 -day ErC50 (growth rate, based on frond number) and EyC50 (yield, based on frond number) values are both determined at >1000 mg/L. The 7 -day ErC10 and EyC10 values are >1000 mg/L and 113 mg/L, respectively. Based on a reported 90% active ingredient in the tested substance, these values are >900 and >101 mg/L.