An elemental impurity in drug product arises from several sources; they may be added intentionally in the synthesis of drug product component (e.g. Catalysts) or may be present as a contamination and subsequently detected in drug product. Elemental impurities do not provide any therapeutic benefit to the patient, their levels in the drug product should be controlled within acceptable limits. This article discusses the assessment process to ensure that elemental impurities are consistently maintained below the most stringent PDE limits between USP and ICHQ3D.