Americans are exposed to much more ionizing radiation (the potentially harmful type) than they were 30 years ago. Greater use of medical imaging such as CT scans accounts for almost all the increase. The tests can reveal serious health threats, of course, but they come with risks.

Radiation experts recommend that the public receive less than one millisievert a year beyond natural background radiation (3.1 mSv), not counting medical tests. As shown, common sources such as airport scanners fall far below that recommendation, suggesting that anxiety about certain technologies is unwarranted.

Among medical tests, CT scans are the greatest concern. Studies indicate as many as one third are prescribed unnecessarily. The average exposure for one scan is 7.1 mSv, according to David Schauer, executive director of the National Council on Radiation Protection and Measurements. “There is growing consensus that CT manufacturers should reduce CT scans to less than 1 mSv,” he says, adding that at a February meeting, companies indicated new technology could make that possible.


Also, see this Web exclusive on how much radiation we get from common sources.