Next Last Index Home Text Slide 25 of 42 Radioactive materials are a natural part of our air, soil, water, rocks, building materials and food.
Cosmic radiation bombards our atmosphere constantly.
Fallout from above ground nuclear testing also contributes to your background radiation exposure. Background Radiation Combined, these sources account for about 300-350 mrem per year in Iowa. Background radiation exposure is not included as part of your occupational radiation dose.