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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

A study in S. vacuolatus with hydrogen sulphide is available.

Key value for chemical safety assessment

Additional information

The 24 -hour EC50 of hydrogen sulphide to the algae S. vacuolatuswas calculated to be 0.055 mM, equivalent to 1.87 mg/l (based on measured exposure concentrations). This concentration is calculated to be equivelant to 2.44 mg/l phosphorus pentasulphide.

Phosphorus pentasulphide reacts rapidly with environmental moisture or water, with the formation of hydrogen sulphide and phosphoric acid. Phosphoric acid will dissociate into environmentally ubiquitous ionic species, and is likley to be have a positive (nutritive) effect on algal growth, however a negative secondary effect (due to pH change) is possible at high concentrations. Hydrogen sulphide is likely to be the more toxic of the breakdown products of phosphorus pentasulphide and will therefore be relevant for PNEC derivation.