Most man-made applications of radiation are controlled by law. These laws generally allow only authorized users to utilize radioactive materials. They place strict limits on any potential discharge of radioactive substances into the environment. They also require employers to manage and restrict the radiation exposure of their staff.

In health care, radiation is generally used only when a doctor considers that a patient should undergo a particular procedure, which might be a diagnostic X-ray, a computed tomography (CT) scan, an isotope scan, or radiotherapy. In these situations, the doctor makes a judgement about the benefit to the patient from achieving a diagnosis or treatment effect, in comparison with the small additional cancer risk from the radiation exposure. Most countries have guidelines to support these clinical judgements.

Some natural sources of radiation are not easily controllable. Our exposure to cosmic radiation and gamma radiation from natural radioactivity in rocks and soils is determined largely by where we live. The most important source of exposure from natural radioactivity is radon in homes and workplaces, and this can be controlled.