Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

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:

As mentioned previously, in the case of the current substance (i.e., Pb-salt ), the chemical safety assessment will be based on elemental metal concentrations, regardless of their (pH-dependent) speciation in the environment. Hence, as the assessment is based on the element concentration (i.e., Pb), physicochemical processes like phototransformation and hydrolysis are not relevant. Formation of different Pb-hydroxides may occur, but the chemical assessment will not make any differentiation among the different Pb-species (pooling of different speciation forms). This elemental-based assessment (pooling all speciation forms together) can be considered as a worst-case assumption for the chemical assessment. In general, (abiotic) degradation is an irrelevant process for inorganic substances that are assessed on an elemental basis.