According to a report from the National Academies' National Research Council, a preponderance of scientific evidence shows that even low doses of ionizing radiation, such as gamma rays and X-rays, are likely to pose some risk of adverse health effects. The 17-member panel, including Dr. Scott Davis of the Public Health Sciences Division, focused their report on low-dose, low-LET (linear energy transfer) ionizing radiation that is energetic enough to break biomolecular bonds. In living organisms, such radiation can cause DNA damage that eventually leads to cancers. However, more research is needed to determine whether low doses of radiation may also cause other health problems, such as heart disease and stroke, which are now seen with high doses of low-LET radiation.
The study committee defined low doses as those ranging from nearly zero to about 100 millisievert (mSv) — units that measure radiation energy deposited in living tissue. The radiation dose from a chest X-ray is about 0.1 mSv. In the United States, people are exposed on average to about 3 mSv of natural background radiation annually.
The committee's report develops the most up-to-date and comprehensive risk estimates for cancer and other health effects from exposure to low-level ionizing radiation. In general, the report supports previously reported risk estimates for solid cancer and leukemia, but the availability of new and more extensive data have strengthened confidence in these estimates.
People are exposed to natural background ionizing radiation from the universe, the ground and basic activities such as eating, drinking and breathing — sources that account for about 82 percent of human exposure.
Nationwide, man-made radiation comprises 18 percent of human exposure. In this overall category, medical X-rays and nuclear medicine account for about 70 percent, according to the report. Elements in consumer products — such as tobacco, tap water and building materials — account for another 16 percent. Occupational exposure, fallout and the use of nuclear fuel constitute roughly 5 percent of the man-made component nationwide.
The report was sponsored by the U.S. departments of Defense, Energy and Homeland Security, the U.S. Nuclear Regulatory Commission and the U.S. Environmental Protection Agency. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering.
Find more information and the complete report at http://national-academics.org.