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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

The key study carried according to OECD Guideline provides a 72h-EC50 value above 8.1 mg/L (nom.). Therefore, the registered substance (HDI Trimer MEKO-blocked) is not considered as harmful to Desmodesmus subspicatus at the limit of water solubility.

Key value for chemical safety assessment

Additional information

Solubility and stability of HDI Trimer MEKO-blocked in water

The test material was insoluble in water (far from 100 mg/L). Thus, test material meets the definition of poorly water soluble mixture and has to be considered as a "difficult mixture to test" according to OECD Guidance No 23 (2000) on aquatic toxicity testing of difficult substances and mixtures.

Nevertheless, the registered substance (HDI Trimer MEKO-blocked) with a half-life of 139 d (for pH 7 and 25 °C, calculated from experimental data at 50, 65 and 80 °C), is stable in water for short-term testing.

Study design of Algae ecotoxicity testing on HDI Trimer MEKO-blocked (Weyers, 2007)

Test solutions were prepared by direct addition in water using ultra turrax, magnetic stirrer and filter as auxiliaries. Nominal test concentrations were 4.0 and 8.1 mg/L.

The study design included analytical determination of concentration. The preparation of the test solutions met recommendations from OECD Guidance No 23 (2000):

i. solution concentration higher than theoretical water solubility limit to achieve the maximum dissolved substance

ii. separation of undissolved test substance from the test solution

iii. direct addition to water and use of mixing techniques such as shaking and stirring

Results of Algae ecotoxicity (Weyers, 2007)

According to OECD Guidance No 23, the effect concentration should be determined and expressed relative to the geometric mean of the measured concentrations. However, in this study the observed recovery of the registered substance was variable. This variability might be explained by difficulties in preparing media leading more to a dispersion of test material rather than solution of test item. As a result, EC50 values are based on nominal test concentration.


The registered substance (HDI Trimer MEKO-blocked) is not harmful to Desmodesmus subspicatus at the limit of water solubility.