Uranium compounds, especially uranyl acetate, have been widely and routinely used as transmission electron microscopy centrist stains for biological materials since 1958. Those of us who do TEM of biologicals use small quantities of uranyl acetate, nitrate, formate, sulfate and perhaps other uranium compounds almost daily and therefore keep inventories of these salts and their solutions.

In the 1980's growing concerns about medical and research wastes entering regional dump sites prompted state radiation officials in Oregon to begin tightening the regulations for monitoring and controlling all radioactive substances including the uranium compounds commonly used in processing biological specimens for TEM.