Concerns with low-level ionizing radiation.

Objective: To clarify the effects of ionizing radiation and to dispel fear associated with the use of radioactivity in medical diagnosis and therapy.

Design: Studies of populations in geographic areas of increased cosmic radiation and high natural background radiation, radiation-exposed workers, patients with medical exposure to radioactivity, and accidental exposure are reviewed.

Results: No reproducible evidence shows harmful effects associated with increases in background radiation of 3 to 10 times the usual levels.