Radon – Invisible Threat

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Shawn Shouse
Ag Engineering Field Specialist
Iowa State University Extension and Outreach

It has been 30 years since Iowans started talking about radon gas.  Awareness has increased greatly, but the risk still exists.  So let’s have a quick reminder discussion about radon.

What’s the quick summary?

Radon is a radioactive gas in the soil that can leak into homes and cause increased risk of lung cancer.  Inexpensive tests can determine the radon level in your home.  Various methods can be used by homeowners and certified contractors to reduce radon exposure.

What is radon?

Radon is a radioactive gas.  It comes from the radioactive decay of radium which is found in small amounts in the soil.  In a long list of radioactive decay products beginning with uranium and ending with lead, radon is the only step in the process where a solid product becomes a gas.  For an average of 4 days, this radon gas is free to move about through spaces in the soil before it decays again into the next solid product, polonium.  If radon gas finds its way into an enclosed space like a home, in sufficient concentration it can have serious health effects.

What risk does it pose?

When radon gas decays, it produces radiation in the form of alpha particles.  Within the next hour or so, the following four decay products (called daughter products) further decay, producing alpha and beta particles.  These radiation particles do not cause significant damage to our bodies from the outside, but if the radon or daughter products are inhaled, the radiation dose is absorbed by delicate lung tissues, leading to increased risk of lung cancer.  Developing lung tissues in children are particularly vulnerable.  Radon gas exposure is estimated to cause approximately 20,000 lung cancer deaths in the US each year, including approximately 150 deaths in Iowa. 

How much radon is in my home?

Testing in the 1990s indicated that the average level of radon in Iowa homes increases slightly from southeast to northwest, but radon levels can vary greatly from one home to another in the same neighborhood.  The only way to know your radon level is to test within your home.  Radon gas is invisible and odorless, so using an appropriate test is the only way to measure.

How do I test for radon?

Two types of inexpensive homeowner tests are available for radon.  Short-term tests involve opening a canister of charcoal material and exposing it to the home air for 3-7 days.  The canister is then sealed and sent immediately (preferably early in the week to avoid shipping delays) to a laboratory where they analyze the charcoal for the concentration of radon daughter products.  Analysis gives an estimate of the radon concentration in the home during that short exposure time (a spot-check).  Long-term tests record physical or electrical effects of the decay particles.  These long-term kits can be left open for up to a year, with the laboratory analysis giving a long-term average radon concentration for the home over that period.  Radon test kits are available from many hardware and home stores, or by contacting your local county health department, or by calling the Iowa Department of Public Health Radon Hotline 1-800-383-5992.

How much radon is too much?

Health risks from radon exposure are cumulative.  Higher risk comes from higher concentration and longer exposure.  The US EPA has set the action guideline for radon in homes at 4 picocuries per liter (pCi/L).  Picocuries per liter is a measure of radiation intensity.

What should I do?

Don’t panic.  Radon is a long-term cumulative risk, not an immediate risk.  Test your home.  Winter testing in the lowest level of your home will likely give the highest expected reading for your home.  If your result is below the action guideline, your exposure risk is low.  If your result is between 4 and 8, you might want to do a long-term test to get a more accurate reading.  If your short-term result is above 20, or your long-term result is above 4, you may want to consider corrective actions.

How can I reduce radon in my home?

Radon gas enters a home from the surrounding soil.  Sealing openings between the soil and the house interior can help.  In extreme cases, it may be necessary to reverse the air pressure difference that helps draw air from the soil into a home.  These pressure change systems can be relatively easy to install when homes are being built, but more difficult and expensive for existing homes.  Help from a qualified and certified expert is advised for diagnosis, higher concentrations, and more difficult corrective measures.

Who can help me?

Iowa requires State certification for contractors who test for radon or make corrective measures (mitigation) and laboratories who measure radon.  The Iowa Department of Public Health maintains a list of certified radon measurement specialists, mitigations specialists, and testing laboratories.  To access these lists and many other radon resources and information, visit the department website at https://www.idph.iowa.gov/radon  or call 1-800-383-5992.  The US EPA has additional information at https://www.epa.gov/radon

Date of Publication: 
March, 2019