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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

Pseudokirchneriella subcapitata, OECD 201, static freshwater test: 
Effects on growth rate (WAF): ErL10(72h): 1.9 mg/L, ErL20(72h): 3.5 mg/L, ErL50(72h): 10 mg/L, NOELR: 1.0 mg/L, LOELR: 3.2 mg/L.
Effects on biomass (WAF): EbL10(72h): 0.86 mg/L, EbL20(72h): 1.3 mg/L, EbL50(72h): 2.4 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
10 mg/L
EC10 or NOEC for freshwater algae:
1.9 mg/L

Additional information

The toxicity towards freshwater algae was investigated according to OECD Guideline 201 / EU Method C.3 by Vryenhoef and Mullee (2012). The unicellular algae Pseudokirchneriella subcapitata was used as test organisms, which is a representative of primary producers in natural waters and can therefore be considered as an important non-target organism in freshwater ecosystems. Based on the inherent properties of the test substance, i.e. poor water solubility and the nature of a complex mixture, the standard method was modified for the preparation of aqueous media. The approach of Water Accomodated Fractions (WAFs) is endorsed by several regulatory authorities in the EU and elsewhere (i.e. ECETOC and OECD). The test substance is mixed with water for a prolonged period of time. Pre-study work showed that a preparation during 24 h is sufficient to ensure equilibrium between the substance and the water phase. After an 1-h settlement period, separation is done by siphon and the test organisms are exposed to the WAFs. Based on the results of two range-finding experiments, the definitive test was conducted with loading rates of 0.10, 0.32, 1.0, 3.2 and 10 mg/L. Three replicates were prepared for each treatment group. A control (six replicates) and a reference item, potassium dichromate, were also included in the experiment. The initial cell density was 5 x 10E3 cells/mL. Samples were taken at the beginning, after 26 h, 48 h and at the end of the exposure period (72 h). The cell densities were determined with a Coulter(R) Multisizer Particle Counter. No abnormalities were microscopically detected in any of the control or test cultures. High Performance Liquid Chromatography (HPLC) was used for analytical monitoring. The algae was affected by the presence of the test substance, which is revealed by the following results (loading rate WAFs): ErL10(72h): 1.9 mg/L, ErL20(72h): 3.5 mg/L, ErL50(72h): 10 mg/L based on growth rate inhibition. The corresponding No Observed Effect Loading Rate (NOELR) was 1.0 mg/L, the Lowest Observed Effect Loading Rate (LOELR) was 3.2 mg/L. It was not possible to calculate the 95 % CL for the ErL50 value as the data generated did not fit the models available for this calculation.

Based on yield inhibitions (biomass), the EbL10(72h) is 0.86 mg/L, EbL20(72h): 1.3 mg/L and EbL50(72h): 2.4 mg/L with 95 % CL of 1.9 - 2.9 mg/L. Since the toxicity cannot be attributed to a single component and the dissolved test substance was below the quantifiable limit of the analytical method, the results were based on nominal loading rates only.