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# Man-Made Sources

Although all living things are exposed to natural background radiation, exposure to man-made radiation sources differs for the following groups:
        - Members of the Public
        - Occupationally Exposed Individuals (Workers)

## Members of the Public

In general, the following man-made sources expose the public to radiation (the significant radioactive isotopes are indicated in parentheses):
        - Medical Sources (by far, the most significant man-made source)	           - Diagnostic  x-rays
          - Nuclear medicine procedures (iodine-131, cesium-137, and others) 
        - Consumer Products	           - Building and road construction materials
          - Combustible fuels, including gas and coal
          - X-ray security systems
          - Televisions
          - Fluorescent lamp starters
          - Smoke detectors (americium)
          - Luminous watches (tritium)
          - Lantern mantles (thorium)
          - Tobacco (polonium-210)
          - Ophthalmic glass used in eyeglasses
          - Some ceramics 

To a lesser degree, the public is also exposed to radiation from the nuclear fuel cycle, from uranium mining and milling to disposal of used (spent) fuel. In addition, the public receives some minimal exposure from the transportation of radioactive materials and fallout from nuclear weapons testing and reactor accidents (such as Chernobyl). For that reason, the U.S. Nuclear Regulatory Commission (NRC) requires its licensees to limit the maximum radiation exposure to individual members of the public to 100 mrem (1 mSv) per year. The related NRC regulations and radiation exposure limits are contained in Title 10, Part 20, of the *Code of Federal Regulations* (10 CFR Part 20).

## Occupationally Exposed Individuals

In general, occupationally exposed individuals work in the following areas:
        - Fuel cycle facilities
        - Industrial radiography
        - Radiology  departments (medical)
        - Nuclear medicine departments
        - Radiation oncology departments
        - Nuclear power plants
        - Government and university research laboratories

Such individuals are exposed to varying amounts of radiation, depending on their specific jobs and the sources with which they work (including cobalt-60, cesium-137, americium-241, and other isotopes). For that reason, the NRC requires its licensees to limit occupational exposure to adults working with radioactive material to 5,000 mrem (50 mSv) per year. The related NRC regulations and radiation exposure limits are contained in 10 CFR Part 20. Toward that end, employers carefully monitor the exposure of these individuals using instruments called dosimeters.

Page Last Reviewed/Updated Friday, March 20, 2020

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Page Last Reviewed/Updated Friday, March 20, 2020