The average
person is exposed to 170
millirems of
radiation per
year. 50% of that comes from
natural sources (
cosmic rays,
solar radiation, upper
atmosphere radiation, and natural radioactivity), while the other 50% from
artificial sources (mostly from
medical exams).
Radiation is measured in RADs (Radiation Absorbed Dose), REMs (Roentgen Equivalent Man), Gy (gray), Sv (sievert), or Bq (becquerel).
Radiation statistics (mostly from http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html ):
A person would get one millirem of radiation from:
You increase your dose by a millirem by:
The risk of one millirem of radiation dose is a 1 in 8 million risk of dying of cancer if large dose effects extrapolate linearly to zero dose.
The loss in life expectancy from a 1 millirem dose is about 1.2 minutes, which is equivalent to:
Typical annual exposure levels in millirem:
5 statutory limit on radiation from operating
a nuclear power plant
25 internal exposure from radioactive
material ingested into the body
45 cosmic rays
75 diagnostic medical exposure (x-rays)
60 external radiation from radioactive
ores, etc
120 natural radiation sources (combined)
200 average total exposure in the U.S.
500 average occupational dose for radiologists
1250 natural exposure in mountainous regions of Brazil
5000 maximum permissible occupational exposure (5 rem)
Consequences of radiation exposure in rem (not millirem!)
rem Effect
0-25 No observable effect
25-100 Slight blood changes
100-200 Significant temporary reduction in blood
platelets and white blood cells
200-500 Severe blood damage, nausea, hair loss,
hemorrhage, death in many cases
>600 Death in less than two months for over 80%
of people