This document, issued by the Food and Drug Administration (FDA), provides the answers to seventeen frequently asked questions regarding Prussian blue. Prussian blue has been used as a pigment in industry and for artists since 1704. It has been used as a treatment to speed up the excretion of radioactive cesium or non-radioactive thallium from the body, according to studies reported in literature. The FDA has encouraged manufacturers to submit applications for Prussian blue as part of efforts to encourage the development of drug products for treatment of people exposed to harmful levels of radioactive materials and poisons and for counter-terrorism agents.
U.S. Food and Drug Administration: http://www.fda.gov