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Toxicity to other above-ground organisms

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Description of key information

An assessment factor of 6 has been selected on the lowest toxicity data. Considering a background concentration of 1.3 mg Pb/kg in the food, the PNECoral can be calculated as:PNECoral= (NOEC +Cb)/AF = (64+1.3)/6 =10.9 mg/kg food (mammal). This value is further used for risk characterisation purposes.

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:

The lowest NOEC for mammals refers to a full chronic study for mammals (Morris et al. 1938), which resulted in a NOEC value of 64 mg Pb/kg ww.Sub-chronic and chronic studies for 3 different mammal species were collected from literature, ie for Rattus sp. (different strains), Rattus norvegicus and for mice. For mammal oral toxicity the values varied between 64 and >12800 mg/kg ww. The lowest value of 64 mg Pb/kg ww was used to derive the PNEC, which was observed in several experiments with the Osborn-Mendel rat. According to the guidance, the PNECoral was calculated from the lowest NOECoral using an assesment factor.

An assessment factor of 6 has been selected on the lowest toxicity data. Considering a background concentration of 1.3 mg Pb/kg in the food, the PNECoral can be calculated as:PNECoral= (NOEC +Cb)/AF = (64+1.3)/6 =10.9 mg/kg food (mammal). This value is further used for risk characterisation purposes.