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Radiation Current doses of exposure to radiation are quite low for most current screening techniques, and, most often, the benefits of their use outweigh their risks. Yet there is a lot of evidence that shows that radiation from a number of sources, including medical procedures, may be contributing to the increased incidence of breast cancer observed over the past couple of decades.

What are the sources of radiation that may be sources of cancer?

The vast majority (approximately 82%) of ionizing radiation to which we are exposed comes from natural sources including the universe (cosmic rays), compounds within the earth and the air. Of the remaining 18% of ionizing radiation to which we are all exposed, the largest source (about 80%) comes from medical sources of radiation, including nuclear medicine, X-rays and other diagnostic and treatment procedures in which radiation is used. Another 5 % of man-made sources of radiation in the U.S. include occupational exposure, fallout from nuclear tests and the use of nuclear fuels as a source of energy [National Research Council, 2005].

How are people exposed to radiation?

The amount of an individual's exposure to radiation is influenced by the type of medical care a person receives, including both diagnostic and treatment sources of radiation, as well as one's occupation, and residential proximity to higher sources of natural radiation, nuclear fallout and other sources.

How might radiation influence the risk of breast cancer?

Ionizing radiation can break the bonds within molecules of biological tissues. In particular, this radiation can cause damage to DNA, eventually leading to the development of cancer, including breast cancer. Breast tissue is one of the most sensitive areas of the body (along with bone marrow) with regards to susceptibility to cancer-induction following exposure to radiation.

The risks of cancer increase as exposure increases, but the actual development of cancer does not occur for many years, sometimes decades, after the exposure(s) to radiation. Exposure of children, adolescents and young adults to a variety of types of medical and military radiation has been shown to lead to increases in breast cancer incidence, while postmenopausal women exposed to high sources of radiation do not appear to have an increased risk for breast cancer [Boice et al., 2001; Preston et al., 2002].