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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The EC50 of Citrowanil B for the algae toxicity is 18 mg/l after 72 h.

Key value for chemical safety assessment

EC50 for freshwater algae:
18 mg/L
EC10 or NOEC for freshwater algae:
5 mg/L

Additional information

The study was performed to assess adverse effects of Citrowanil B on the growth (= increase in cell density) and the growth rate (= rate of increase in cell density with time) of the planktonic freshwater algal species Desmodesmus subspicatusover several generations.

The Study was conducted in accordance with EEC methods for Determination of Ecotoxicity Annex to Directive 92/69/EEC Part C, Method 3 “Algal inhibition test”.

Exponentially growing algal cells were exposed for a period of 72 hours to a rage of concentrations, nominally 2.5, 5, 10, 20 and 40 mg/l of Citrowanil B dissolved in water. Auxiliaries used to prepare the test media were an ultra turrax, a magnetic stirrer and a folded filter.

The cell density was measured at 24 hour intervals. Inhibition of the algal population was measured as reduction in growth (index b) and growth rate (index r), relative to control cultures grown under identical conditions. Growth and growth rate were used to calculate a No Observed Effect Concentration and a Lowest Observed Effect Concentration according to DUNNET (1955. 1964). The following values were determined:

Results [mg/l]:

EbC 50 (0-72h):     18

ErC 50 (0-72h):      24

NOEC [b] (tα 0.05):   5

LOEC [b] (tα 0.05):   10

NOEC [r] (tα 0.05):    5

LOEC [r] (tα 0.05):    10


All results are expressed in terms of nominal concentrations. The recovery rates ranged from 94.3 – 97.1 % of nominal values at 0 hours, and from 83.4 – 97.1 % of nominal values at 72 hours, respectively.