Characteristics of Radon-222

Fate and Transport

Monitoring in the Environment


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

Methods of Monitoring Radon-222 in the Environment


- concentrations vary with soil type, meteorologic conditions and diurnally
- average ambient outdoor radon levels are about 0.2 - 0.7 pCi/L
- outdoor radon is a small health hazard (700 lung cancer deaths/year, US)


- highest concentrations in ground water compared to surface water
- radon gas emanating from a residential water source produces radon progeny
- inhaling/ingesting waterborne radon progeny is a very small health hazard


- concentrations vary with underlying or surrounding rock or soil type
- occupational radon levels are highest for miners(uranium, iron and fluorospar)
- residential radon levels are highest in basements and ground floor rooms
- building type, construction, level of repair and ventilation effect levels
- average radon level in homes is about 1.25 pCi/L
- radon remediation recommended at residential levels above 4.0 pCi/L
- indoor radon is a significant health hazard(3 - 32,00 lung cancer deaths/ year)


1) Charcoal canister and liquid scintillation detectors contain small quantities of activated charcoal. Radon and its decay products are absorbed onto the charcoal and are measured by counting with a sodium iodide detector or a liquid scintillation counter.

2) Alpha track detectors contain a small sheet of plastic that is exposed for a period of one (1) to twelve (12) months. Alpha particles etch the plastic as they strike it. These marks are then chemically treated and counted in the laboratory to determine the radon concentration.

3) Electret ion detectors contain an electrostatically charged Teflon disk. Ions generated by the decay of radon strike and reduce the surface voltage of the disk. By measuring the voltage reduction, the radon concentration can be calculated.

4) Continuous monitors are active devices that need power to function. They require operation by trained testers and work by continuously measuring and recording the amount of radon in the home.

5) Obtain testing devices at retail outlets (hardware stores...), mail order or by hiring and EPA qualified or State certified radon tester. At the end of the test period, the test kit is mailed to a laboratory for analysis. Results are mailed back within a few weeks.


1) Short-term (2 days to 3 months):
- location - lowest level of dwelling that is commonly used, at least 20 inches above the floor (but not kitchen or bathroom because of humidity and ventilation fans)
- conditions - doors and windows closed 12 hours prior and during test period ( 2-3 day tests should not be conducted during severe storms or high winds)
- device - all types
- limitations - radon levels vary day to day and season to season
- advantages - quick results (high levels require follow-up testing)

2) Long-term (longer than 3 months)
- location - lowest level of dwelling that is commonly used, at least 20 inches above the floor (but not kitchen or bathroom because of humidity and ventilation fans)
- device - alpha track detector, electret ion detector or continuous monitor
- limitations - results delayed by up to 1 year
- advantages - more likely to indicate accurate average radiation level and exposure

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