Chronic exposure is exposure spread over a longer period of time. The early effect of radiation exposure include nausea, vomiting, diarrhea, and internal bleeding. These effects are observed in people who receive acute radiation doses of hundreds of rads to the whole body. The delayed effects are biological symptoms which appear in the exposed person years after the exposure. They include cancer, genetic effect, a shortened life span, and cataract.
Genetic effect is the effects of radiation exposure manifested in the offspring of exposed parents.
The following is a simplified list of acute exposure and possible early effects. Soil contains naturally radioactive material such as potassium, uranium, thorium, and their progenies. Radon, one progeny of uranium and thorium, contributes the largest natural radiation exposure to humans. The background radiation exposure may vary according to the location because of differing radionuclide concentrations in rock, soil, water, and an increase of cosmic radiation with altitude. The food we eat, the water we drink, and the air we breath contains radioactive material.