Your Annual Radiation Dose

by Wm. Robert Johnston
last updated 25 June 2002

Radiation is all around us as a part of our natural environment. It may be measured in units of millirems (mrem). The average annual radiation dose for Americans is estimated at 360 mrem per person. Many people receive more than this, but this is not dangerous. The normal permissible limit is 5,000 mrem for those who work around radiation, and even this is far below what will cause signs of illness. Recent research is leading to the conclusion that annual radiation doses of hundreds of mrem actually reduce the risk of cancer.

This worksheet is revised and updated from one by the American Nuclear Society printed in 1980.

Common sources of radiationYour annual dose (mrem)
YOURadioactive elements in your body39
WHERE YOU LIVECosmic radiation at sea level (depends on your elevation above sea-level -- use table 1; U.S. average = 27 mrem)___
Ground (use table 2; U.S. average = 26 mrem)___
Radon (use table 2; U.S. average = 200 mrem)___
House construction -- for stone or concrete add 7 mrem___
WHAT YOU EAT, DRINK, AND BREATHECosmogenic radiation (Carbon-14)1
Drinking water5
Fallout from nuclear weapons testing0.1
HOW YOU LIVENatural gas use in home -- 5 mrem___
Eyeglasses with glass lenses -- 1 mrem___
Pacemaker -- 160 mrem___
Jet plane travel: total hours traveled in past year _____ x 0.4 mrem/hour___
TV viewing or computer use (except flat screens): average hours per day _____ x 0.15 mrem/hour___
Smoke detectors (U.S. average)0.01
WHERE YOU WORKExposure at work -- U.S. average = 1.1 mrem (for jobs around radiation see table 3)___
MEDICALNumber of chest x-rays ____ x 5 mrem___
Number of x-rays of extremities ____ x 1 mrem___
Number of dental x-rays ____ x 10 mrem___
Total for other x-rays or radiopharmaceutical examinations (see table 4)

(Total U.S. average, medical = 60 mrem)

HOW CLOSE YOU ARE TO A COAL POWER PLANT OR NUCLEAR POWER PLANTAt site boundary: average hours/day ____ x 0.2 mrem/hour___
1.5 km away: average hours/day ____ x 0.02 mrem/hour___
8 km away: average hours/day ____ x 0.002 mrem/hour___
over 8 km away0
Coal-burning plants (U.S. average)0.2

Compare your dose to the U.S. annual average of 360 mrem.

Your chances of dying of cancer are increased by 10% if you accumulate 250,000 mrem--or if you smoke 4 packs of cigarettes per day for fifty years.

Table 1: Cosmic radiation and elevation (above sea level)

elevation (meters)annual dose (mrem)

Table 2: Radiation from ground and radon

locationannual dose from ground (mrem)annual dose from radon
U.S. average28200
Atlantic coast16100
Rocky Mountains40
Central U.S.20
South Texas20100
areas with monazite sands500

Table 3: Average annual doses for nuclear-related occupations

occupationannual dose (mrem)
medical radiologist320
nuclear power plant worker760
nuclear industry380
Dept. of Defense nuclear-related180
Dept. of Energy nuclear-related300
universities nuclear-related210

Table 4: Typical doses for some medical procedures (whole body dose)

proceduredose (mrem)
head or neck x-ray15
cervical spine x-ray22
lumber spine x-ray130
pelvis x-ray44
hip x-ray83
upper GI series245
lower GI series405
barium enema54
bone scan440
thyroid treatment with radioiodine7000
CAT scan800

Table 5: Biological effects of radiation

Increase of 1% in chances of developing cancer25,000 mrem
Radiation sickness100,000 mrem within 48 hours or less
50% chance of death from radiation sickness450,000 mrem within 24 hours or less

Note: Dosage figures from man-made sources are approximate; some may be outdated, given that many of these figures are declining over time as technology improves. For example, the dose associated with a particular type of x-ray is decreasing as more sensitive films permit use of a smaller x-ray dosage.

© 2002 by Wm. Robert Johnston.
Last modified 25 June 2002.
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