Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The 72-hour NOEC (highest concentration tested without toxic effects) was 1.0 mg/L, since at this test concentration the mean biomass and the mean growth rate r of the algae was statistically not significant lower than in the control. The 72 h EC50 value was 43 mg/L based on the growth rate with the 95 % confidence limit of 26-86 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
43 mg/L
EC10 or NOEC for freshwater algae:
1 mg/L

Additional information

The influence of the test item FAT 40825/A on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to the OECD Guideline No. 201, 1984. However, the test method was modified to quantify not only the algicidal effect of the test item, but also the growth inhibition effect caused by reduced light intensities in the colored test solutions.

The nominal test concentrations were 0.32, 1.0, 3.2, 10, 32 and 100 mg/L in parallel with a control. All test media down to the lowest test concentration were slightly to strongly colored by the test item.

The analytically determined test item concentrations in the analyzed test media varied in the range from 86 to 108 % of the nominal values. Consequently, the test item was stable during the test period of 72 hours under the conditions of the test, and the reported biological results are based on the nominal concentrations of the test item.

The test design consisted of two experimental parts. In experimental part A, the algae were grown in the presence of different test item concentrations as in the usual algal toxicity test. In experimental part B, the algal growth inhibition caused by the pure light effect (the reduced light intensities in the colored test media) was quantified: the algae grew in test water without test item (as in the control), however under changed light conditions due to the filter effect of the colored test media in glass dishes above the algal suspensions. These dishes contained test medium with same test item concentrations as in part A, however without algae. The results in experimental parts A and B based on growth rates were compared.

The growth inhibition effect of FAT 40825/A on Scenedesmus subspicatus was caused in part by the indirect effect, the light absorption in the colored test solutions. However, at the higher test concentrations a real toxic effect of the test item on the growth of Scenedesmus subspicatus can not be excluded. Therefore, the results of the experimental part, where the algae grew in the test media with dissolved test item as in a usual algal growth inhibition test are taken into consideration for the determination of the toxic effect of the test item on the growth Scenedesmus subspicatus.

FAT 40825/A had a statistically significant inhibition effect on the growth of Scenedesmus subspicatus after the exposure period of 72 hours first at the concentration of 3.2 mg/L (= 72 hour LOEC: lowest concentration tested with toxic effects). The 72-hour NOEC (highest concentration tested without toxic effects) was 1.0 mg/L, since at this test concentration the mean biomass and the mean growth rate r of the algae was statistically not significant lower than in the control. The 72 h EC50 value was 43 mg/L based on the growth rate with the 95 % confidence limit of 26-86 mg/L.