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Characteristics of Radon-222
Fate and Transport
Monitoring in the Environment
Measurement
Measurement Methods
Control and Prevention
Harmful Effects
Absorption, Distribution and Organic Sites of Toxicity
Radon Dose
Radon Biomarkers
Risk Assessment
Molecular Action and Genetic Effects
Radon for Skeptics
Radon for Children
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Characteristics of Radon-222
ORIGIN OF RADON
- released by radioactive decay of radium-226 (T 1/2 = 1620 years)
- radium-226 is produced though the radioactive decay of uranium-238
- uranium-238 (T 1/2 = 4.51 billion yrs) comprises 4 ppm of the earth’s crust
- radon-222 is a non-reactive noble gas and itself is not a health hazard
PHYSICAL CHARACTERISTICS OF RADON
- an odorless, tasteless, invisible gas that mixes with air
- chemically inert and essentially non-reactive
- heaviest noble gas with highest melting and boiling point
- highly soluble in non-polar solvents
- moderately soluble in cold water
- able to diffuse through rock and soil
- decays by alpha particle emission (T 1/2 = 3.8 days)
PRODUCTS OF RADIOACTIVE DECAY OF RADON
- decay products are solids and are called daughters or progeny
- the ratio of progeny to radon gas ranges from 0.2 - 0.8 (average 0.4)
- radon progeny are short-lived ( 0.2 milli seconds to 26.8 minutes)
- seven decay steps from radon-222 produce stable lead-206
- chemically active and charged radon progeny can attach to air particles
- radon daughters polonium-218, 214 and 210 are alpha particle emitters
- alpha particles, when inspired, can potentially cause physical cellular damage
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