"The average American now receives more than five times as much radiation from medical procedures as in the early 1980s. The medical sector now accounts for almost half of an average person's dose.
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Background radiation from the ground, outer space and people's own bodies remained steady at 3.11 mSv. Meanwhile, the rise of nuclear medicine imaging techniques - especially computed X-ray tomography (CT) scans - meant that doses from medicine went from 0.53 mSv to 3.00 mSv.
Radiation emissions from nuclear power, nuclear research and uranium activities were included in an industrial category which accounted for 0.003 mSv per year - less than 0.1% of overall exposure."
http://www.world-nuclear-news.org/RS_Medicine_pushes_up_radiation_exposures_0903092.aspx