They are deeply penetrating and can damage body cells. Although all cells are subject to damage, bone marrow cells and cells in the intestinal lining appear to be particularly sensitive. Fortunately, most animals can repair some radiation damage by replacing cells or increasing the activity of undamaged cells. Beta particles cannot penetrate as deeply as gamma rays, but they can also damage living cells. Beta particles can cause severe skin burns if fallout is retained on the skin, and they can damage cells in the digestive tract if fallout is ingested with food or water.
Instruments can measure the number of radiation exposure units in a given period.
Total radiation exposure over a certain period of time is often referred to as a total dose, such as 700 R over a 7-day period. After fallout is deposited, radiation levels decrease with time. Radiation levels decrease rapidly at first, and they more slowly. Distance decreases radiation dose. The further you are from the radiation source, the smaller the dose you would receive.