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Meet the Millirem

The millirem is a unit of absorbed radiation dose.

A person would get this amount of radiation from
  • Three days of living in Atlanta
  • Two days of living in Denver
  • About seven hours in some spots in the Espirito Santo State of Brazil.
You increase your dose by a millirem by:
  • an average year of TV watching
  • a year of wearing a luminous dial watch
  • a coast-to-coast airline flight
  • a year living next door to a normally operating nuclear power plant
What is the risk from such a dose?
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Reference
Cohen, Bernard
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Meet the Millirem

The millirem is a unit of absorbed radiation dose.

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, equivalent to:

  • crossing the street three times
  • three puffs on a cigarette
  • 10 extra Calories for an overweight person
What does it take to receive a radiation exposure like this?
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Reference
Cohen, Bernard
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Typical Radiation Doses in Millirem

Note: This does not include radon exposures, which may be very high.
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Reference
Nave & Nave, 3rd Ed.
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Environmental Radiation Exposure

U.S. Average Exposure

Source Exposure in mrem/yr
Cosmic rays
45
External radiation from
radioactive ores, etc.
60
Internal exposure from
radioactive material
ingested into the body
25
Diagnostic X-rays
70
Total:
200


Note: This does not include radon exposures, which may be very high.
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Reference
Bushong
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Press Overreaction to Radiation



When it became evident in the 70's and 80's that radon exposure in one's own home is probably greater than the radiation exposures which had regularly been trumpeted in headlines, we entered another awkward era in the reporting of radiation issues.
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Reference
Cohen
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Acute Radiation Exposure

Effects of Large, Whole-Body Radiation Doses

Effect Dose (rems)
No observable effect
0-25
Slight blood changes
25-100
Significant reduction in blood platelets and
white blood cells (temporary)
100-200
Severe blood damage, nausea, hair loss,
hemorrhage, death in many cases
200-500
Death in less than two months for over 80%
>600
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Reference
Nave & Nave
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Increased Cancer Risk:Bomb Victims


Atlanta Journal, Mar 20,1993 pg F1. 		The increased risk of various types of cancer has been studied extensively among the victims of the Hiroshima and Nagasaki nuclear bombs. The study of 120,000 Japanese has led to the relative risk factors shown. The risk appears to be linear with dose. The dose at 1000 meters at Hiroshima is estimated at 4 grays.
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Hiroshima and Nagasaki Radiation

The Nagasaki bomb was an "implosion" device with high explosive wrapped around the plutonium. The violent compression detonated the plutonium, but also absorbed a considerable fraction of the neutrons so that the main flux from the blast was gamma rays. The Hiroshima bomb was a uranium bomb of the gun type and, having no neutron capturing shroud, it produced a much higher neutron flux. There were 140,000 fatalities within four months in Hiroshima and 70,000 in Nagasaki.

A 1986 study estimated the neutron dose at 1000 meters from ground zero Hiroshima was 1% of total dose but 15-20% of radiation sickness. New studies of concrete with an accelerator mass spectrometer which measured the chlorine-36 isotope indicate a neutron flux 10 times higher.

The gamma doses were estimated by thermoluminescent dosimetry of roof tiles in the blast areas, but no such test existed for the neutron measurement.

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Correlation between smoking and lung cancer


John Cairns, The Cancer Problem, Scientific American 233, Nov 1975, p64 		Index

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