Metal salts with low oral bioavailability and considerable exposures from ubiquitous background: Inorganic aluminum salts as an example for issues in toxicity testing and data interpretation.

Oral administration is the preferred route of exposure for non-volatile chemicals with potential environmental exposures. For metal salts, systemic doses in such toxicity testing are often low due to limited oral bioavailability. Issues arising from the low bioavailability for toxicity testing and risk characterization are illustrated using aluminum (Al) salts as example. Al-cations have an oral bioavailability of below 1% and applicable doses are limited resulting in low systemic doses. Consequently, the low systemic doses are insufficient to induce clear adverse effects that may serve as points of departure for risk characterization.