This is a clarification under which certain activated phosphors that are not on the Toxic Substances Control Act (TSCA) section 8(b) Chemical Substance Inventory (TSCA Inventory) will be considered to be new chemical substances under TSCA section 5, and thus will be subject to applicable notification requirements under TSCA section 5. In certain letters and other statements issued by EPA from 1978 to 2003, the Agency erroneously indicated that activated phosphors (otherwise known as doped phosphors) constitute mixtures of phosphors and dopants for purposes of the TSCA Inventory, and thus that they were not separately reportable as chemical substances under TSCA section 5(a) new chemical notification requirements. This clarification is necessary because EPA's statements in this area have not been consistent.