Pyrochlore, antimony lead yellow

Toxicity to aquatic algae and cyanobacteria

Description of key information

For algae, 7 individual reliable freshwater acute toxicity data points for one species were put forward for hazard assessment purposes. The acute toxicity values (48h-LC50) for Pseudokirchneriella subcapitata varied between of 21.7 µg dissolved Pb/L (at pH 7.5 and hardness of 24.2 mg/L) and 322.9 µg dissolved Pb/L (at pH 7.3 and hardness of 174.4 mg/L). 2 different chronic high quality no-effect levels for dissolved lead for freshwater algae situated between 34.1µg Pb/L and 93.0 µg Pb/L (Pseudokirchneriella subcapitata) were observed. High quality no-effect levels for dissolved lead for marine algae plants were situated between 52.9 µg Pb/L (Skeletonema costatum; endpoint: yield) and 1231.8 µg Pb/L (Dunaliella tertiolecta; endpoint: growth rate).

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:

For algae, 7 individual reliable freshwater acute toxicity data points for one species were put forward for hazard assessment purposes. The acute toxicity values (48h-LC50) for Pseudokirchneriella subcapitata varied between of 21.7 µg dissolved Pb/L (at pH 7.5 and hardness of 24.2 mg/L) and 322.9 µg dissolved Pb/L (at pH 7.3 and hardness of 174.4 mg/L). 2 different chronic high quality no-effect levels for dissolved lead for freshwater algae situated between 34.1µg Pb/L and 93.0 µg Pb/L (Pseudokirchneriella subcapitata) were observed. High quality no-effect levels for dissolved lead for marine algae plants were situated between 52.9 µg Pb/L (Skeletonema costatum; endpoint: yield) and 1231.8 µg Pb/L (Dunaliella tertiolecta; endpoint: growth rate).