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Toxicity to microorganisms

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Description of key information

The key endpoint is the sludge respiration inhibition EC50 of 760 mg/L. 

Key value for chemical safety assessment

EC50 for microorganisms:
760 mg/L

Additional information

One study according to OECD 209 (Volskay & Grady, 1988) and one study with Pseudomonas putida (Bringmann & Kuehn, 1976) are available. The RAR (2008) also summarises data available for flagellated protozoa (Bringmann & Kuehn, 1980).

Two studies are available with V. fischeri and added as supporting information.

According to the RAR (2008), data for both bacteria and protozoa should be taken into account when deriving a PNEC for micro-organisms.

However, this is restricted to ciliated protozoa, constituting the most important class of protozoa in sewage treatment plants (STPs) . The protozoa tested were all flagellates rather than ciliated protozoa and therefore the PNEC derivation is based on data for bacteria, as concluded in the RAR (2008).


Taking the sludge respiration inhibition test EC50 of 760 mg/l with an AF of 100 gives the most conservative PNEC which is therefore used in this assessment, in concurrence with the RAR (2008).

Additional reference:

Bringmann, G and R Kühn, 1980. Bestimmung der biologischen Schadwirkung wassergefährender Stoffe gegen Protozoa (III. Saprozoische Flagellaten). Z. Wasser Abwasser Forsch 13, no.5, pp 170-173.