Radon facts

That sentence is from the U.S. Surgeon General's 2005 health advisory, which EPA reprints in its Citizen's Guide. The advisory goes on to say that the threat is completely preventable, and that radon can be detected with a simple test and fixed through well-established venting techniques.

Some facts about radon are simply interesting. They also explain why radon behaves the way it does in a house.

Interesting facts about radon and the miners who revealed the risk

WHO says an increased rate of lung cancer was first seen in uranium miners exposed to very high concentrations of radon, and that studies in Europe, North America and China have since confirmed that even low concentrations, such as those commonly found in homes, also pose health risks. EPA's Health Risk of Radon page describes two 2005 studies that combined data from earlier residential studies, one North American and one European, which confirmed the risks predicted by the miner studies.

EPA also points out that we know more about radon risks than about risks from most other cancer-causing substances, because estimates of radon risk are based on studies of cancer in humans. EPA's Health Risk of Radon page points readers to the Iowa Radon Lung Cancer Study, on radon-related lung cancer in women, among that research; the Iowa radon report shows the state's zone and testing data.

An area's zone is a prediction from EPA's Map of Radon Zones, and EPA says the map should not be used to determine if individual homes need to be tested. Look up any county on the radon zone map, or open the state and county radon reports for predicted potential and reported testing data side by side.

EPA's Citizen's Guide translates radon levels into lifetime lung cancer risk for groups of 1,000 people. It is the clearest radon statistic EPA publishes, and it shows two things at once: risk rises with the level, and smoking multiplies it.

EPA notes that a former smoker's risk may be lower than a current smoker's, and higher than that of someone who never smoked. It also says not everyone exposed to elevated radon will develop lung cancer, and the time between exposure and the disease may be many years. WHO says no other cancer risks or health effects have been established to date. The radon and lung cancer guide goes further into the evidence.

The single biggest fact about radon risk is how much smoking changes it. NCI says exposure to the combination of radon gas and cigarette smoke creates a greater risk of lung cancer than exposure to either factor alone, and that the majority of radon-related cancer deaths occur among smokers. Yet radon matters to people who have never smoked too: NCI says more than 10 percent of radon-related cancer deaths occur among nonsmokers.

CDC's advice follows from that: if you smoke, quitting is still the best way to reduce your risk of lung cancer. The radon and lung cancer guide has the full breakdown.

Radon can come in with water as well as through the foundation, but the two routes are not equal. CDC says high radon levels in the water supply are more likely when its source is groundwater, such as a private well, and that most public water supplies are sourced from surface water (lakes, rivers, and reservoirs).

That is why EPA's myth list says it is important to first test the air in the home for radon. If the air shows a problem and the home is on a private well, the radon in water guide covers testing the water next.

Today's radon advice rests on a few landmark reports. Each date below is from the agency that published or reprints the work.

January is still the month for radon awareness: CDC observes Radon Awareness Week in January. The Surgeon General's advisory also gave the reason indoor air matters so much: a study it cites found Americans spend between 85 and 95 percent of their time indoors. See National Radon Action Month.

Radon gets into homes from the ground, so the facts about where it collects follow from that. NCI says basement and first floors typically have the highest radon levels because of their closeness to the ground, and that radon levels can be higher in homes that are well insulated, tightly sealed, and/or built on soil rich in the elements uranium, thorium, and radium. ATSDR adds that concrete construction materials or cracks in the basement or foundation of a home may allow higher levels of radon and radon progeny inside the home.

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1. 1Cracks in solid floors
2. 2Construction joints
3. 3Cracks in walls
4. 4Gaps in suspended floors
5. 5Gaps around service pipes
6. 6Cavities inside walls
7. 7The water supply

None of these facts tells you the level in a particular house. EPA says homes next to each other can have different indoor radon levels, which is why the radon in homes guide and EPA both end in the same place: test.

Testing is the only way to know the radon level in a specific building. EPA and the Surgeon General recommend testing all homes below the third floor, and EPA also recommends testing in schools. EPA's Citizen's Guide says millions of Americans have already tested their homes. EPA gives three steps for a homeowner:

1. 1

   Take a short-term test

   Place it in the lowest lived-in level of the home, at least 20 inches above the floor. EPA says all radon tests should run for a minimum of 48 hours, and for a short test of less than four days, windows and outside doors should be closed at least 12 hours before it starts.

2. 2

   Follow up a result at or above 4 pCi/L

   Take a long-term test for a better picture of your year-round average, or a second short-term test if you need results quickly.

3. 3

   Decide on a fix

   Fix the home if a long-term result is at or above 4 pCi/L, or consider fixing if the average of two short-term tests is. The radon level interpreter walks a result through EPA's guidance.

EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. EPA's Citizen's Guide says most homes today can be reduced to 2 pCi/L or below, and that hundreds of thousands of homeowners have already fixed radon problems in their homes. The method primarily used is a vent pipe system and fan that pulls radon from beneath the house and vents it outside.

WHO says passive systems of mitigation can reduce indoor radon levels by more than 50%, and that adding radon ventilation fans can reduce levels even further. EPA recommends a contractor trained to fix radon problems, because lowering high levels requires technical knowledge and special skills. See how systems work in the radon mitigation guide, and find providers in the radon professionals directory.

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1. 1Soil gas drawn from beneath the slab
2. 2Suction point through the slab
3. 3Vent pipe
4. 4Fan, outside the living space
5. 5Discharge above the roofline

EPA's Citizen's Guide carries its own list of radon myths, each answered with a fact. The most common ones are below, in EPA's terms. The radon scam guide takes the doubts about radon further.

Radon fact or fiction: six claims checked

Soil gas

Gas in the ground beneath and around a building. EPA says radon from soil gas is the main cause of radon problems, and that building materials rarely cause them by themselves.

For radon information about your own area, EPA's Home Buyer's and Seller's Guide says that if you have a radon-related question, you should contact your state radon office; the state radon programs page lists them. EPA's consumer booklets are the fullest fact sheets it publishes: A Citizen's Guide to Radon, the Home Buyer's and Seller's Guide to Radon, and the Consumer's Guide to Radon Reduction.