There are several sources of naturally occurring radiation that everyone is exposed to, including radiation from the Earth's crust like uranium and thorium, cosmic rays and solar flares, inhaled radon, and ingested radioactivity. Cosmic radiation exposure varies depending on altitude and latitude. Terrestrial radiation also varies based on location, altitude, and local soil composition. Radon gas is the largest source of natural radiation, as it can accumulate in homes and irradiate lung tissue with alpha particles. In addition to natural sources, there is radiation exposure from artificially produced sources like medical x-rays, which contribute the largest man-made amount of radiation to the average annual dose for the U.S. population.

1. Sources of
Radiation
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2. Objectives
List at least three different sources
of naturally occurring radiation
Estimate your radiation dose from
natural and artificially produced
radiations
Explain how radiation varies on
earth
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3. Principal Components of
Background Radiation
Everyone is exposed
External sources
Solar and cosmic rays
Soils, rocks, building
materials
Inhaled sources
Radon
Ingested sources
Foodstuffs
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4. Solar Flares
High energy protons and electrons
streaming from the sun and hit the
earth’s outer atmosphere
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5. Cosmic
Radiation
High energy particles
Protons
Electrons
Muons
Heavy particles
(Z<26)
Interact with earth’s
atmosphere
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6. Radiation From the
Earth
Naturally occurring radionuclides
present in rocks, soils, plants,
water, air, and building material
Major nuclides include
Uranium (U)
Thorium (Th)
Radium (Ra)
Radon
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7. Inhaled Radioactivity
Primarily radon and progeny,
from
Buildings
Smoking
Rocks, soils
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8. Ingested Radioactivity
Naturally occurring
radionuclides are
present in food
40
K is a major contributor
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9. Variations in Dose
Northeaster, Eastern Central, and Far Western
Areas, Range 35 to 75 mrem/yr
Average:46 mrem/yr
Colorado
Plateau ,
Range 75 to
140 mrem/yr
Average: 90
mrem/yr
Atlantic and
gulf coastal
plain, Range
15 to 35
mrem/yr
Average:23
mrem/yr
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10. Artificially Produced &
Enhanced Radiation
X-rays
Nuclear medicine
Televisions
Nuclear power plants
Smoke detectors
Radium dials
Nuclear waste
Air travel
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11. Where Your Dose Comes From
4%
3% 1% Contributors to Dose
Radon, 55%
Cosmic, 8%
11%
Terrestrial, 8%
Internal, 11%
Medical X-rays, 11%
11%
Nuclear Medicine, 4%
55%
Consumer Products, 3%
Other, <1%
8%
8%
Occupational 0.3%
Fallout, <0.3%
Nuclear Fuel Cycle, 0.1%
Miscellaneous 0.1%
Contribution of various sources to the total
U.S. average effective dose equivalent
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12. U.S. Annual Average Dose
Annual average total effective doses to the U.S.
Population
Natural background,
2 mSv
200 mrem
radon
Natural background,
1 mSv
100 mrem
other
Medical diagnostic,
0.39 mSv
39 mrem
x-rays
Nuclear medicine
0.14 mSv
14 mrem
Consumer Products
0.12 mSv
12 mrem
Rounded Total
3.6 mSv
360 mrem
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13. Summary
Everyone is exposed to radiation
from
Natural sources
Enhanced natural sources
Artificially produced sources
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14. Summary, cont’d
Natural background radiation
comes
Earth’s crust
Cosmic rays and solar flares
Inhaled
Ingested radioactivity
Cosmic rays vary with altitude and
position relative to equator
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15. Summary, continued
Terrestrial radiation varies with
locality, altitude, and soils
Radon and its progeny result in
irradiation of lung tissue with alpha
particles - this is the largest
source of natural radiation
Diagnostic radiation is the largest
man-made source of radiation
contribution to U.S. population
dose
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