Radiation has been a serious concern to individuals for over 100 years. A process by which an atomic nucleus emits particles to reach a more stable energy state, radiation harms living cells (usually by inhalation and absorption into the lungs) by causing abnormal cell function and structure. Man is constantly exposed to background radiation, both naturally caused and manmade (nuclear power plants and weapons testing, consumer products, medical x-rays, etc.). Uranium mining and milling, an especially dangerous radiation-exposing activity, can be more safely pursued by using mechanical ventilation, isolation and diversion of the radiation source, air cleaning, respiratory protection, and job rotation. Radiation's health effects are numerous. Cancer studies around radiation sources reveal epidemics of respiratory disease and great danger when radioactive gases mix with other pollutants. Pregnant women are the most susceptible to radiation because division of the fetus's cells can greatly increase the damage caused from exposure. Research is still needed on the effects of nonionizing radiation sources (microwaves and radiowaves). Appendices include additional information on radiation measurement, organs at risk, naturally occurring radionuclides, decay series of Uranium-238, radiation exposure and responsible government agencies. (LC)