The struggle to contain radioactive releases at Japan’s Fukushima Daiichi nuclear plant has focused the world’s attention on the hazards of radiation. However, even without such incidents, you are subject to harmful radiation every day.
Low-level background radiation bathes the earth. Cosmic rays are penetrating subatomic particles. According to NASA, about 100 of these particles bombard every square meter of the planet at sea level every second – and will pass through you if you are in their path. The number of powerful cosmic rays increases rapidly with altitude.
Additional radiation originates from radioactive materials at the earth’s surface. The amount varies by location. Finally, tiny amounts of radioactive forms of potassium, carbon, and other materials that make up your body get into your cells through food or other means.
The good news is that life evolved with this background radiation. Effective repair mechanisms offer protection from radiation within each cell. Every second your body is fixing the damage.
For the average American, radiation from manmade sources roughly doubles annual exposure from the natural background level. The biggest contributor to routine radiation is diagnostic medical imaging tests. The President’s Cancer Panel concluded that Americans receive 48% of their total radiation exposure from medical imaging and other medical sources, as opposed to only 15% in the early 1980s. CT scans alone account for 24% of the total.
What is the risk from this doubling of natural radiation dosages?