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Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 for algae: no effects within water solubility
NOEC50 for algae: no effects within water solubility

Key value for chemical safety assessment

Additional information

A study by Hanstveit and Oldersma (1993) is available on the toxicity of stearic acid to aquatic algae. However, due to methodological insuffiency, the study was rated reliability 3. Since no further studies are available, read across to palmitic acid (C16), which is a member of the fatty acids category, was done.

The 72h test provided by the Ministry of the Environment, Government of Japan was conducted by an unknown author in 2000. It was accomplished according to OECD 201 and in accordance with GLP. Pseudokirchnereilla subcapitata was tested under static conditions with 95% pure palmitic acid. Based on growth rate an EC50 (72h) as well as a NOEC (72h) were determined to be >0.9 mg/L. Thus, no toxic effects on aquatic algae were observed within the water solubility of the test substance.

This result from palmitic acid (C16) is applicable to stearic acid, since the water solubility declines with chain length and toxicity of the fatty acid substances declines likewise with chain-length starting with C12. Thus, no toxicity on algae is to be expected from stearic acid within water solubility.