What is Radon?
Radon is a naturally occurring, invisible, odorless gas that comes from deposits of uranium in soil, rock, and water. It is harmlessly dispersed in outdoor air, but when trapped in buildings, can be harmful, especially at elevated levels. Radon is a radioactive decay product of radium, which is itself a decay product of uranium. Uranium and radium are both common elements in soil.

Where is radon found?
The primary source of high levels of radon in homes is the surrounding soil. Radon has been found in elevated levels in homes in every state, and the U.S. Environmental Protection Agency (EPA) estimates that as many as one in 15 homes across the U.S. have elevated radon levels. 

How does radon get into my house?
Warm air rises. When this happens in your home, it creates a vacuum in the lower areas of the house. Nature hates a vacuum, so something must rush in to fill it. In the case of your home, air seeps in from the soil around and under the house, and some air is sucked in through openings (cracks, doors, windows) on the lower levels. Radon gas enters the same way air and other soil gases enter the home; through cracks in the foundation floor or walls, hollow-block walls, and openings around floor drains, pipes and sump pumps.

What are the health effects of radon?
Exposure to radon is the second leading cause of lung cancer in the U.S. Radon can be inhaled into the lungs, where it undergoes radioactive decay. As it decays, radon releases tiny bursts of energy called alpha particles, which can harm sensitive lung tissue by damaging the DNA. This damaged DNA can lead to lung cancer.

How is radon measured?
Radon is measured in picocuries per liter of air (pCi/L), a measurement of radioactivity. The U.S. EPA and the Centers for Disease Control and Prevention recommend that homes with radon levels 4.0 pCi/L, or greater, be fixed.

How do I find out if my house has elevated levels of radon?
Radon testing can identify if elevated radon levels exist. The EPA has established protocols for this testing and a number of test methods may be employed based upon initial findings. Generally, a simple canister test can reveal if your house has elevated readings. If readings are above acceptable limits, further verification and/or testing is recommended.

Can my house be fixed if it has elevated radon levels?
A variety of methods can be used to reduce radon in homes. Sealing cracks and other openings in the foundation is a basic part of most approaches to radon reduction, however, sealing by itself may not be sufficient to reduce radon levels consistently. In other instances, depressurization systems employing pipe vents (natural-draft and/or fans) may be applied. Other options may be available base on your home's construction and level of reduction required.

If I don't have a basement, can I still have a radon problem?
Radon can seep in from soil anywhere around or under a home, regardless of whether your home has a basement, crawl space, or is built slab-on-grade. The U.S. EPA and Surgeon General recommend radon testing for all types of homes.

My neighbors have tested their home and don't have high levels so why should I test?
Radon levels can vary considerably from house to house, even on the same street. It is nearly impossible to predict the exact nature of geologic soil deposits and the extent to which soil gasses will seep into and be retained by a specific house. The only way to know whether radon exists in elevated levels in your home, and to protect your family from radon, is to test.

Is there proof that radon is a serious health problem?
The science on radon has been formidable over the years, but never before have we had such overwhelming scientific consensus that exposure to elevated levels of radon causes lung cancer in humans. In February of 1998, the National Academy of Sciences (NAS) presented the findings of their Biological Effects of Ionizing Radiation (BEIR) VI Report: "The Health Effects of Exposure to Indoor Radon." This new report by NAS is the most definitive accumulation of scientific data on indoor radon. The report confirms that radon is the second leading cause of lung cancer in the U.S. and that it is a serious public health problem. The study fully supports the U.S. EPA estimates stating that radon causes between 15,000 and 22,000 lung cancer deaths per year.The average person receives a higher radiation dose from radon at home than from all other natural or man-made sources combined.

Outdoor radon levels in the U.S. range from 0.02 to 0.75 pCi/L (picoCuries per liter), averaging 0.4 pCi/L. But most buildings draw from the ground concentrated radon gas. Because radon is eight times heavier than air, elevated radon levels then build up in basements and on lower floors. While the U.S. Congress has set the natural concentration outdoors as the target radon level for homes, approximately two thirds of homes exceed the average outdoor level of 0.4 pCi/L. A half of homes have a radon level above 0.67 pCi/L (the median level). The average (mean) radon level in US homes is 1.25 pCi/L, or three times higher than the level outdoors.

Nearly 8 million US homes, or 1 out of every 15, have radon levels above the EPA's 4 pCi/L action limit and nearly 1 out of 6 exceed the EPA's 2 pCi/L consider action limit. You should always try to reduce radon to a practical minimum. 

• What are "picoCuries"?
  
  The concentration of radon gas is not measured directly, but rather by the radioactivity it produces. It is expressed in picoCuries per liter of air, or "pCi/L". A Curie is a unit of radioactivity equivalent to 1 gram of radium and the prefix "pico" means a trillionth. In Canada, radon concentration is expressed in Becquerels per cubic meter (Bq/m3). One Becquerel means one radioactive disintegration per second and 4 pCi/L equals to 148 Bq/m3. In an average basement, 38 million atoms will undergo radioactive decay each hour.

• How safe is the 4 pCi/L radon "action" limit?
  
  Although the 4 pCi/L level has become a benchmark for real estate transactions, it still carries considerable risks - equivalent to getting a chest x-ray or smoking 10 cigarettes each day. (EPA)
  
  Assuming the highest level in today's mines - 30 pCi/L, the average person receives at 4 pCi/L in his home during the course of 12 years the same radiation exposure as if he/she worked for 5 years in a uranium mine.
  
  When relaxing at home, we breathe in radon. It is soluble in blood, circulates through the body organs and is exhaled by the lungs or skin until equilibrium is established between the ambient and internal levels. But radon decay products, radioactive solid particles, much smaller than household dust, float in the air and get trapped in our lungs, trachea, and bronchi. At 4 pCi/L each liter of air contains 70,000 radon atoms, but less than 1% of the inhaled atoms get trapped and we thus accumulate in our airways about 600,000 radioactive particles every hour.
  
  At the levels common in homes, radon is 1,000 times more lethal than the safety limits on any other toxin or carcinogen. The risk to the average person of radon-caused lung cancer death due to exposure to 4 pCi/L radon level at home is 2.4 percent. If there are four people in your family, the chances that someone becomes a victim of radon are four times higher.
  
  According to the National Academy of Sciences report on the Biological Effects of Ionizing Radiation (BEIR VI, 1998), residential radon levels at or below 4 pCi/L cause 70% of the radon-attributed deaths.
  
  The latest and most substantial epidemiological study ever on the link between residential radon and lung cancer was published in May 2000. This 5-year study, led by the University of Iowa, proves that radon even at the low levels found in homes causes lung cancer and that the risk is proportional to the radon level. The study shows that cumulative exposure of adult women to radon over 15 years at the EPA "action level" of 4 pCi/L increases the lung cancer risk by 50%.

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