But the average is 3 millisieverts (mSv) per year. How much of this so-called background radiation you are exposed to depends on many factors, including altitude and home ventilation. We're exposed to small doses of ionizing radiation from natural sources all the time - in particular, cosmic radiation, mainly from the sun, and radon, a radioactive gas that comes from the natural breakdown of uranium in soil, rock, water, and building materials. Ionizing radiation can damage DNA, and although your cells repair most of the damage, they sometimes do the job imperfectly, leaving small areas of "misrepair." The result is DNA mutations that may contribute to cancer years down the road. The radiation you get from x-ray, CT, and nuclear imaging is ionizing radiation - high-energy wavelengths or particles that penetrate tissue to reveal the body's internal organs and structures. But are we courting future public health problems? Exposure to ionizing radiation on the rise The benefits of these tests, when they're appropriate, far outweigh any radiation-associated cancer risks, and the risk from a single CT scan or nuclear imaging test is quite small. CT scanning and nuclear imaging have revolutionized diagnosis and treatment, almost eliminating the need for once-common exploratory surgeries and many other invasive and potentially risky procedures. Over 80 million CT scans are performed in the United States each year, compared with just three million in 1980. But many experts are concerned about an explosion in the use of higher radiation–dose tests, such as CT and nuclear imaging. For most women, there's very little risk from routine x-ray imaging such as mammography or dental x-rays. Patients want to know if radiation from mammograms, bone density tests, computed tomography (CT) scans, and so forth will increase their risk of developing cancer. There's always questions about radiation exposure from medical imaging.
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