Reaction product of 9-[2-(ethoxycarbonyl)phenyl]-3,6-bis(ethylamino)-2,7-dimethylxanthylium chloride and Naphthalenesulfonic acids, reaction products with formaldehyde, ammonium salts

Toxicity to aquatic algae and cyanobacteria

Description of key information

In a 72-h algal growth inhibition test on Pseudokirchneriella subcapitata with the test substance, the 72-h EC50 based on the growth rate was 0.046 mg/L and based on the yield the 72-h EC50 was 0.014 mg/L. The overall NOEC was determined to be 0.0033 mg/L (all calculations were based on the geometric mean of the measured concentrations). 

Key value for chemical safety assessment

EC50 for freshwater algae:

0.046 mg/L

EC10 or NOEC for freshwater algae:

0.003 mg/L

Additional information

The purpose of the study was to determine the effect of the test substance on the growth of a unicellular green algal species Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) according to OECD 201 Guideline.

Exponentially-growing cultures of Pseudokirchneriella subcapitata were exposed to the test item over several generations under defined conditions.

Based on the results of the preliminary test, six different concentrations arranged in a geometric series and untreated control group were tested: 0.512; 1.28; 3.2; 8; 20 and 50 mg/L. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and thus, over several algal generations.

Samples were taken from the test concentration and the control at the start and at the end of the experiment and analysed by HPLC method. The measured concentration of the test item in the test solution was in the range of 0.0086 – 0.791 mg/L at the start and 0.0003 – 0.093 mg/L at the end of the test. There is an evidence that the concentration of the tested substance was not maintained within ± 20 % of the nominal concentration throughout the test. Therefore the analysis of the results was based on the geometrical mean of the measured concentration values.

The results of the statistical evaluation showed that the 0-72 h average specific growth rate and yield was statistically significantly different from that of the untreated control at the test item concentrations of 0.0137 (nominal 3.2), 0.0406 (nominal 8) 0.1705 (nominal 20) and 0.2712 (nominal 50) mg/L. Accordingly, the No Observed Effect Concentration (NOEC) was determined as 0.0033 (nominal 1.28) mg/L, while the 72h-LOEC was 0.0137 (nominal 3.2) mg/L test item concentration. The 72h-EC50 for growth rate and yield was calculated to be 0.046 and 0.014 mg test item / L, respectively.