((a)) ** .—** Material that emits ionizing radiation spontaneously may be transported on a passenger-carrying aircraft in air commerce (as defined in ) only if the material is intended for a use in, or incident to, research or medical diagnosis or treatment and does not present an unreasonable hazard to health and safety when being prepared for, and during, transportation.

((b)) ** .—** The Secretary shall prescribe procedures for monitoring and enforcing regulations prescribed under this section.

((c)) ** .—** This section does not apply to material the Secretary decides does not pose a significant hazard to health or safety when transported because of its low order of radioactivity.