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Toxicity to aquatic algae and cyanobacteria

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Description of key information

No effects on toxicity to aquatic algae up to the limit of water solubility.

Key value for chemical safety assessment

Additional information

In general, all EC/EL50(72h) values derived with dififerent algae species for various test substances in the SCAE C2 -C8 category were above the limit of water solubility. Physical effects caused by the test substance were described in presence of undissolved test material.

The effects of Fatty acids, C16-18, 2-ethylhexyl esters to the freshwater algae Scenedesmus subspicatus were investigated according to DIN 38412 (Kläs 1994). Nominal concentrations of 30, 100 and 300 mg/L without removal of insoluble particles were tested and yielded an EC50(96 h) of 300 mg/L and a NOEC(96 h) of 30 mg/L, both based on biomass. It can be assumed that the undissolved particles inhibited the algal growth due to physical effects and not to systemic toxicity.

To substantiate these findings, a further key study as read-across from 2-ethylhexyl oleate (CAS 26399-02-0) to the freshwater algae Scenedesmus subspicatus was taken into account (Rieche 1995). The test was performed according to EU-Method C.3 with filtered and unfiltered solution of 100 mg/L. The filtered solution showed no significant inhibition of algae growth or growth rate which means that the water soluble part of the test substance turned out not to be toxic. With a more or less homogenous emulsion of test material high inhibitions of algae growth and growth rate were observed (75.7% and 42.6% respectively). This observed inhibition in presence of undissolved test substance can be accounted to physical, but not biological influences and a ErC50(72h) of > 100 mg/L could be stated.

As supporting study, a read across from Fatty acids, C16-18 and C18-unsatd., 2-ethylhexyl esters (CAS: 85049-37-2) was used. In this test, the marine algae Skeletonema costatum was tested according to ISO 10253 (WAF-test). The resulting ErL50(72h) was determined as 281.4 mg/L (nominal loading rate, Hudson 2000).