The top radiation source Americans should be worrying about isn't airport scanners or microwaves—it's medical tests. The US leads the world in the amount of radiation its population gets from medical scans, and the average American's dose has grown more than sixfold in recent decades. Patients are being given far too many imaging tests, warn experts who fear that in a few decades up to 2% of all US cancers may be the result of radiation from CT scans being given now, AP reports.
CT scans are particularly dangerous because of the high doses involved: One study found that US heart attack patients get the radiation equivalent of 850 chest X-rays during the first few days their hospital stay. Based on studies of Japanese atomic bomb survivors, scientists estimate that cancer risk rises after being exposed to 50 to 150 millisieverts of radiation; a chest CT scan exposes patients to 10 to 20 millisieverts, versus less than 0.1 for a regular chest x-ray.