Which federal department regulates the use and possession of radioactive isotopes?

The regulation of the use and possession of radioactive isotopes falls under the jurisdiction of the Nuclear Regulatory Commission (NRC). The NRC is a federal agency responsible for overseeing and ensuring compliance with national standards for the safe use of nuclear materials. This includes licensing and regulating nuclear reactors, as well as monitoring the use of radioactive isotopes in various fields such as medical, industrial, and research applications. The Commission's role is critical for public health and safety, as they set stringent guidelines and regulations to manage radiation hazards effectively.

While other agencies like the Environmental Protection Agency (EPA) focus on protecting the environment from contaminants, including radiation, and the Food and Drug Administration (FDA) regulates the safety of food and pharmaceuticals which can include radioactive materials in some contexts, their scope does not extend to the comprehensive regulation of radioactive isotopes like that of the NRC. Similarly, the Occupational Safety and Health Administration (OSHA) while concerned with worker safety regarding exposures, is not the primary regulatory body for isotopes themselves. Therefore, the NRC plays a key role specifically in this area, making it the correct answer.