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Toxicity to microorganisms

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Description of key information

Toxicity to activated sludge microorganisms:
- EC10 (3h) >= 1000 mg/L (EU Method C.11 and OECD guideline 209)
- EC50 (3h) > 1000 mg/L (EU Method C.11 and OECD guideline 209)

Key value for chemical safety assessment

Additional information

A 3h respiration inhibition limit test was performed with a nominal concentration of 1000 mg/L of sodium hypophosphite according to the EU Method C.11 and the OECD guideline 209 (Eisner, 2009).Two controls and a positive control (3,5-dichlorophenol) were tested in parallel.

No significant toxic effects were observed and the results of the positive control confirmed suitability of the activated sludge and the method used. The EC10 (3h) of the test substance to activated sludge microorganisms was at least 1000 mg/L. The EC20, EC50, and EC80 (3h) could not be calculated but were clearly higher than 1000 mg/L.

Therefore, sodium hypophosphite has no significant inhibitory effect on the respiration rate of activated sludge and is thus not toxic to these microorganisms.