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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

There are 18 reliable NOEC or EC10 values selected for 5 different functional parameters for microbial processes. The functional parameters comprise C- and N-mineralization. The selected NOEC and EC10 values on functional parameters vary from 96 to 4144 mg Pb kg-1 (both values observed for respiration). Additionally, 20 NOEC or EC10 values are selected for 8 different enzyme assays, ranging from 132 mg Pb kg-1 for dehydrogenase to 16576 mg Pb kg-1 for phosphatase. The ecological relevance of reduced enzymatic activities is unclear and, therefore these data re not used for PNEC calculation, but only presented as supporting evidence.

Key value for chemical safety assessment

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:

There are 18 reliable NOEC or EC10 values selected for 5 different functional parameters for microbial processes. The functional parameters comprise C- and N-mineralization. The selected NOEC and EC10 values on functional parameters vary from 96 to 4144 mg Pb kg-1 (both values observed for respiration). Additionally, 20 NOEC or EC10 values are selected for 8 different enzyme assays, ranging from 132 mg Pb kg-1 for dehydrogenase to 16576 mg Pb kg-1 for phosphatase. The ecological relevance of reduced enzymatic activities is unclear and, therefore these data re not used for PNEC calculation, but only presented as supporting evidence.