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Toxicity to microorganisms

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Description of key information

Short-term toxicity data were extracted from literature for bacteria (heterotrophs and nitrifiers) and different protozoan species. 2 different no-effect levels for lead, between 1.06 and 2.92 mg/L (depending on the exposure time), were compiled for heterotrophic bacteria. For nitrifiers, 2 different no-effect concentrations, between 2.79 and 9.59 mg/L, were observed. 14 different short-term toxicity data were selected for protozoan species/communities. No-effect concentrations for protozoan communities varied between 1.0 and 7.0 mg Pb/L, while LC50 values for protozoan varied between <1.5 and >250.0 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 mg/L

Additional information

Pyrochlore:

The overall chemical and physiological properties of pyrochlore are principally characterised by a degree of inertness because of the specific synthetic process (calcination at high temperatures, approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which the majority of atoms are tightly bound and not prone to dissolution in environmental and physiological media. This has been shown in transformation/dissolution testing for antimony, in which dissolved Sb concentrations were below 27 µg/L (after 7 days at a loading of 0.1g/L) and 2 µg/L (after 28 days at a loading of 1 mg/L); thus implying a solubility of < 0.03% of antimony. Hence, Sb can be considered as not bioavailable and is not regarded concerning toxicological and environmental effects.

On the other hand, lead dissolution levels were much higher (>2.9 mg/L at a loading of 100 mg/L after 7 days at pH 6; 105 µg/L at a loading of 1 mg/L after 28 days at pH 6) and therefore have to be regarded concerning toxicological and environmental aspects. No substance-specific data on the toxicity of pyrochlore are available, so that instead read-across to lead oxide and sparingly soluble lead compounds was conducted

Lead:

Short-term toxicity data were extracted from literature for bacteria (heterotrophs and nitrifiers) and different protozoan species. 2 different no-effect levels for lead, between 1.06 and 2.92 mg/L (depending on the exposure time), were compiled for heterotrophic bacteria. For nitrifiers, 2 different no-effect concentrations, between 2.79 and 9.59 mg/L, were observed. 14 different short-term toxicity data were selected for protozoan species/communities. No-effect concentrations for protozoan communities varied between 1.0 and 7.0 mg Pb/L, while LC50 values for protozoan varied between