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 Background
radiation
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In our daily life, we are exposed to various types of naturally occurring
radiation from cosmic rays, from radioactive substances in the earth, and
from naturally occurring radiation in our bodies. This is commonly referred
to as background radiation. The combined annual dose from these sources
is thought to range from 0.001 to 0.003 sievert (or from 1 to 3 millisievert [mSv]).
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Figure. Annual background radiation
doses in the United States |
In addition,
the same level of radiation is thought to be received annually
from radon, but the
amount varies considerably depending on the geographic area
and the type of building.
The radiation dose from chest radiography is a fraction of
the annual naturally occurring background radiation dose,1
and the dose from fluoroscopy of the stomach is, at most,
0.05 Sv on the skin of the back.
Shown in the figure at left are the average annual radiation
doses received per capita in the United States2 from naturally occurring and manmade sources of radioactivity. The total
yearly dose is approximately 0.0036 Sv (3.6 mSv). |
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References about this subject
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1United Nations Scientific
Committee on the Effects of Atomic Radiation. Annex
E: Medical radiation exposures. In Sources and
Effects of Ionizing Radiation, p 249, 1993. New
York, UN. |
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2US National Council on Radiation
Protection and Measurements, NCRP Report No. 93,
pp 53-55, 1987. Bethesda, Maryland, USA, NCRP. |
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