Risk Assessment Methodology for Medical Devices and Radiation-Emitting Products
Ronald P. Brown and W. Howard Cyr, Ph.D., Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD 20857
FDA's Center for Devices and Radiological Health (CDRH) is responsible for ensuring the safety and effectiveness of medical devices and eliminating unnecessary human exposure to man-made radiation from medical, occupational and consumer products. This broad mandate requires microbial, chemical and radiation risk assessments to be performed to support regulatory decision making in these areas. For example, microbial risk assessments have been performed to support the establishment of Sterility Assurance Levels (SAL) for devices. Chemical risk assessment activities in CDRH focus on three areas: 1) the development and validation of new risk assessment methodologies, 2) bench-top research to provide information for the hazard identification and dose-response assessment stages of the risk assessment process, and 3) the application of risk assessment approaches to assist with regulatory decision making. Risk assessment methodologies under development in CDRH include PBPK models to describe the pharmacokinetic behavior of compounds released from devices and a risk assessment-based approach for the biological evaluation of medical devices. Risk assessments have been used by CDRH to assist in reaching decisions on various issues that have received considerable attention in the media, including the safety of phthalate esters released from PVC devices, dioxin released from tampons, and 2,4-toluenediamine released from polyurethane-foam covered breast implants. CDRH actively participates in the development of consensus standards for risk assessment through various organizations, including the International Organisation for Standardization (ISO).
Radiation risk assessments have been conducted for exposure to electronic product radiation in a wide variety of situations, e.g., malfunctioning diagnostic or therapeutic x-ray machines; UV-emitting sunlamps, tungsten halogen lamps, and fluorescent lamps; microwave and extremely low frequency radiation from cell phone and police radar, and ultrasound diagnostic imaging systems. These radiation risk assessments often use assumptions, models and procedures that don't necessarily fit into the methodology that has been developed for chemical risk assessments. Furthermore, with radiation, there is often a high natural background level of exposure. Sometimes this level can be very high, as in the case of ultraviolet radiation. In such cases, a fraction of the background level may be used to establish a regulatory limit.