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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

One reliable key study is available for the potassium salt of the registered reaction mass. No effect on the respiration rate of activated sludge was measured and therefore the 3h EC50 for STP microorganisms is determined above 1000 mg/L and the 3h NOEC is equal or higher than 1000 mg/L.

Key value for chemical safety assessment

Additional information

One reliable key study is available for the potassium salt of the registered reaction mass.

The reaction mass IBAP and its potassium salt have high water solubility and their behavior in water and biological systems is dominated by their ionization. The main assumption is that the potassium cation is not significant in respect of the toxicological effect on aquatic organisms which are expected to be related to the IBAP. In experimental dilute aqueous conditions at environmental pH (5-9), the salt will be completely dissociated and will not behave differently to the parent acid, at identical concentration of the particular speciated form present.

The inhibitory effect of the substance Kalium isobutylphosphate on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3 hours respiration inhibition test according to OECD guideline for Testing of Chemicals, n°209 (1984) under GLP.

The nominal test item concentrations were 1, 10, 100, and 1000 mg/L. In addition, three controls and six different concentrations of the reference item 3,5-dichlorophenol (0; 2.5; 5, 10; 20 and 40 mg/L) were tested in parallel. No inhibition of the respiration was measured after 3h and therefore the EC50 was determined above 1000 mg/L and the NOEC equal or above 1000 mg/L based on nominal concentration of test item.

For the purpose of risk assessment, the concentration was not corrected for the target substance because the molecular weight of potassium was assessed to be negligible compared to the molecular weight of the other constituents of the reaction mass.