Radiation exposure is slightly higher at higher elevations-thus the exposure in Denver averages 400 millirems per year. The average exposure in the United States, from natural sources of radiation (mostly cosmic radiation and radon), is 300 millirems per year at sea level. Average Natural Background: 300 Millirems In 1957, the occupational limit was lowered to a maximum of 5,000 millirems per year. The occupational limit became 15,000 millirems per year around 1950. This amount is beyond the average 300+ millirems of natural sources of radiation and any medical radiation a person has received.Ģ5,000 millirems per year level was the federal occupational limit during World War II and until about 1950 for radiation workers and soldiers exposed to radiation. The highest recommended limit for radiation exposures is for astronauts-25,000 millirems per Space Shuttle mission, principally from cosmic rays. Masse is a past president of the Health Physics Society and served in 1987-89 as chairman of the National Academy of Sciences panel which reviewed the exposure of soldiers to radiation from atmospheric testing in the 1940s and 1950s. The source of this information is Francis Masse, director of the MIT Radiation Protection Office. amounts from diagnostic research (low levels from radioactive tracer elements). amounts from medical treatment (very high radiation to a limited part of the body), and 5. common sources of additional radiation 4. amounts of natural background radiation 3.
the radiation exposures to the whole body which are the established federal standard for various activities (Note: The first federal standard for fetuses of pregnant radiation workers went into effect Jan. Editor's Note: The information below compares 1.
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