Cerium is a member of the lanthanoid series of rare earth metals. It is also the most abundant and most reactive of the rare earth metals. Cerium oxidizes at room temperature and forms a variety of salt compounds including oxides, hydroxides, sulfates and chlorides. Cerium is used in a variety of ways and is present in many products. For example, cerium is used as a catalyst in emission control systems for gasoline engines, and most recently, as a fuel borne catalyst for diesel engines. In addition, cerium is found in carbon arc lamps, the polishing of lens and mirrors, high temperature ceramics, and the printing and lithographic industries. Cerium is released to the environment as salt compounds from the various uses listed above. This assessment will present reference values for the noncancer effects (RfD and RfC), where supported by the available data, and a cancer evaluation of cerium and cerium compounds. The assessment will be subject to internal review and external peer review along with Agency review. The final product will reflect the Agency's opinion on the toxicity of Cerium and cerium compounds.
U.S. EPA. IRIS Toxicological Review and Summary Documents for Cerium Oxide (Stable) and Compounds. U.S. Environmental Protection Agency, Washington, DC.