Two years ago, when the numbers were crunched, the American people received almost as much radiation from diagnostic imaging procedures as they did from natural background sources. Almost half of the medical exposure came from 67 million computed tomographic (CT) scans, and another quarter came from 18 million cardiac nuclear studies.
The current numbers represent a sevenfold increase in radiation exposure since the early 1980s, when only three million CT scans were performed. Part of the increase reflects a growth of 30 million people in the United States over the past quarter century, and the other part stems from the tremendous increase in the use of CT scans as the most remarkable advance in radiology since the discovery of x-rays more than a century ago.
The current estimates were contained in a new report, No. 160, from the National Council on Radiation Protection and Measurements (NCRP). For those who want the whole poop, the report can be ordered as soft or hard copy from the NCRP at http://www.ncrppublications.org .
Until the current study, estimates of total ionizing radiation always attributed two thirds or more from radiation in soil and rocks, from radon gas that emanates from soil and seeps into homes and other buildings, from cosmic radiation from the sun, and from the human body’s own traces of natural radiation.
Part of the comparison gets a bit confusing, because all of us have a lifetime of exposure from natural sources. Those who live at higher altitudes get more cosmic radiation, and those who live in some parts of the country get more from the soil beneath their homes. By contrast, 67 million CT scans means about one scan for each five persons. Some others get no exposure from medical procedures in most years of their lives.
Besides the two major sources of population exposure, the NCRP report also comments on exposure from occupational sources and consumer products. Consumer products account for only 2% of the total. But within that category, cigarette smoke causes 36%, and commercial airline flights cause 24%.
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