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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Data is available on the acute toxicity of calcium sulfate to algae. No short-term toxicity was observed at the concentrations tested.

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Additional information

A GLP guideline study was performed which assessed the acute toxicity of calcium sulfate dihydrate (NIER, 2003) to Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) in a limit test. The 72 h EC50 for calcium sulfate dihydrate was found to be >100 mg/L, which is equivalent to >79 mg/L for calcium sulfate anhydrous. No adverse effects were noted at this concentration.

A further OECD guideline study (van Eijk, 2009), investigated the toxicity of flue gas desulphurisation gypsum on algae. The results showed that toxicity of the test material was low in all samples and that no toxicity was detected in the 100% undiluted sample (equivalent to a saturated solution of gypsum at a concentration of 2.1 g/L). The EC50 is therefore >2.1 g/L and hence is greater than the maximum solubility of calcium sulfate in water. The NOEC is equal to 2.1 g/L.

A literature study which assessed the toxicity of calcium sulfate to the algal species Nitscheria linearis gave a 120 h EC50 value of >3200 mg/L. No effects were noted and this concentration is greater than the maximum solubility of calcium sulfate in water.

Using a weight of evidence approach, calcium sulfate showed no short-term toxicity to algae and is not acutely toxic to algae at the limit of its water solubility.