By Dr. Mercola
Radon exposure is the number two cause of lung cancer in the U.S., second only to cigarette smoking. It is the number one cause of lung cancer among non-smokers.
It’s estimated between 15,000 to 22,000 people die each year from radon-related lung cancer. A majority of those deaths occur among people who also smoke cigarettes.
Of the 11,000 lung cancer deaths among non-smokers, an estimated 20 to 25 percent are radon-related. 
Radon in your home can originate from a number of sources, including:
Outside air that seeps into your home through cracks in the foundation, walls and floors
Smoke detectors installed in your home
Certain clocks and watches
Radon gas can be deadly and is present in nearly all the air we breathe. I strongly encourage you to investigate how much of this gas you and your family are exposed to, and take the necessary steps to remediate the problem if the levels in your home are excessive.
What is Radon?
Radon is a radioactive gas which comes from the normal breakdown of uranium in rocks, soil and water throughout the world.
You can’t smell, taste or see radon in the air. But it’s in the environment both outside and indoors, and is unique in that it is an indoor air contaminant from a natural source.
Concern about levels of radon in homes and businesses is the result of extensive research that has proved exposure to the gas causes lung cancer in underground miners who work with uranium.
How Radon Causes Disease
Radon has a half-life of three and a half to four days. In other words, half of a given amount of radon takes over three days, but less than four, to decay.
The breakdown products of radon, also known as radon progeny or the daughter products of radon, are a series of solid elements including lead-214, polonium-214 and polonium-218. These elements give off alpha particles of radiation. Alpha particles, unlike gamma radiation, cannot deeply penetrate the tissues of your body, but they do contain sufficient energy to permanently change the structure of your DNA.
If the breakdown elements of this gas reach your lungs, these alpha particles can damage the cells lining your lungs and increase your risk of developing lung cancer, especially with chronic, long-term exposure.
Lung Cancer in Miners
Radon is a very well-studied carcinogen. The scientific community has learned how inhaling radon delivers radiation to the lungs, and how the particles from the radon progeny can damage human cells.
The link between working in underground mines and high death rates was recognized in the mid-1500s, before radon was even identified as an element.
In the early 20th century, scientists linked lung cancer in miners with the high levels of radon found in mines in Czechoslovakia and Germany. In the 1950's, researchers determined it was radon’s breakdown elements and not the gas itself that caused cancer.
In the United States, increased incidence of lung cancer in Mormon and Native American miners was of particular interest since these groups normally have low rates of the disease overall.
Subsequent epidemiologic studies in the 1950’s and 1960’s confirmed the direct connection between radon exposure and lung cancer in miners.
Radon exposure in cigarette smokers is particularly dangerous, because radon breakdown elements attach to the particles in cigarette smoke and lodge in the lungs. The combination of the two carcinogens creates a much greater risk for lung cancer than either factor by itself.
Radon and Non Lung-Related Cancers
There is some evidence radon is linked to cancers outside the lung as well.
One study conducted in Denmark from 1968 to 1994 suggests a statistically significant link between radon exposure and acute childhood lymphoblastic leukemia.
Another more recent study by the University of Texas Medical Branch concluded radon exposure may be a significant risk factor for pancreatic cancer in African Americans, American Indians, and Asian Americans.
How Much Radon is Safe?
Radon levels inside most homes are normally significantly lower than in uranium mines. However, it has been discovered that the range of levels of exposure found in heavily contaminated homes can be the equivalent of levels found in mines, and may actually exceed the established standards permitted for underground miners!
The EPA has developed guidelines for maximum tolerable levels of radon in homes by extrapolating data from high occupational exposures in the mining industry to the much lower residential exposures.
Radon is measured in picocuries per liter of air, or pCi/L. A measurement of 0.4 pCi/L is a typical level of radon in outdoor air and 1.3 pCi/L is the average level for indoor air.
According to the EPA, an average annual indoor level at or above 4 pCi/L is unacceptable. Regularly inhaling that amount of radon inside your home or office carries about the same risk for lung cancer as smoking half a pack of cigarettes a day ...
At the end of this article I will give you some guidelines for how to measure and minimize the radon levels inside your home.
Sources of Radon Exposure
You and your family are exposed to radon in your home, at the office, at school, in commercial buildings -- inside every structure you enter.
Radon in the outside air disperses before it reaches high levels of concentration, but in tightly sealed or poorly ventilated indoor spaces, even low levels of radon can accumulate and pose a significant health hazard.
The radon gas emitted by soil and rock can seep into buildings through gaps in the foundation, construction joints, and through cracks in floors and walls. Since radon levels are highest in rooms closest to the ground, if you spend a lot of time in basement rooms at home, work or school, your risk for exposure could be greater.
Soil radon levels vary widely across the United States and depend on the geology of the area. Regions of the Mid-Atlantic States and the upper Midwest have higher radon levels than those found in the southeast and west into Texas, and along most of the west coast.
In 1998, the EPA estimated that as many as eight million U.S. homes have elevated radon levels. To find out what the natural radon levels are in your area, check out the EPA’s radon map at this link.
Keep in mind that elevated radon levels have been found in almost every state, so be careful not to make assumptions about the safety of your own home based on this map. You will still need to measure the radon levels in your home or office to determine whether or not you may be exposing yourself and your family to dangerous levels.
What is Your Exposure Risk?
Your radon exposure risk will depend on:
The levels of radon in your indoor environments
The amount of time you spend in those environments
Naturally, your radon exposure is likely to be very high if you work in an underground mine (uranium and some other types as well) or a uranium processing facility, if you live near a uranium mine (although few facilities are still in operation), or if you come in contact with phosphate fertilizers.
You can also be exposed to radon gas through drinking water. As the radon is released from the water into the air, you can inhale it into your lungs.
The risk of exposure from water is minimal, unless you happen to use a deep, underground well sunk into rock with a high radium concentration. Water from such a well could have a high level of radon, but surface water from lakes and rivers has very low radon levels.
Radon exposure can also come from certain building materials, including:
Silicone-rich magmatic rocks, particularly granite, and especially the more exotic granites like the red, pink and purple varieties
Gypsum waste products
Another source of radon you may never have thought could harbor any danger is smoke detectors. You may not realize it, but there is more than one type of smoke detector for your home, and some are emitters of this deadly gas. There is the ionization type, the photoelectric type, and detectors which contain both types of sensing devices.
Ionization smoke detectors are less expensive and more commonly used, but they emit small amounts of radon, and also have a higher rate of false alarms than the photoelectric variety.
Certain clocks and watches can also add to the overall radon levels of your surroundings. If you own a new or relatively new watch with a luminous dial, it probably contains either Tritium, a radioactive form of hydrogen, or Promethium, a man-made radioactive element. Both elements emit small amounts of radon, and while most of it is contained in the cover of the watch, there is still a minimal risk associated with having luminous watches around.
If you happen to own a World War I vintage “glow in the dark” clock or watch, be aware that highly radioactive radium was used to make the luminous paint for the dials. Wearing such watches, and certainly repairing them, poses a significant risk of radon exposure.
How to Test Your Indoor Environments for Radon
There are a number of things that can cause indoor radon concentrations to vary. The EPA recommends you perform long-term rather than short-term measurements in order to make the most accurate assessment of consistent radon levels in your home or office.
Indoor radon concentrations can be affected by:
The type and operation of ventilation systems
All forces which affect indoor air pressure, such as window openings, window fans, driers, and fireplaces
The time of day
Different areas inside your home or other structure
If you’d like a certified technician to measure the radon levels in your home or other indoor environment, you can contact the American Association of Radon Scientists and Technologists. Testing costs from $100 to $300.
You can also obtain information on certified technicians and do-it-yourself testing from the EPA. State and regional information can be found at http://epa.gov/iaq/whereyoulive.html.
Do-it-yourself test kits for radon run between $20 and $30 and can be purchased online and at your local hardware store.
Common types of test kit detectors include charcoal canisters, alpha track devices, electret ion chambers, continuous monitors, and charcoal liquid scintillation detectors.
Test kits are placed in your home for several days, up to as long as three months, and then are mailed to a laboratory for analysis. Short-term test kits, which are often used at the time of a home sale, tend to give measurements that are above the actual level in the home. That’s why it’s a better idea to perform one of the longer tests or repeat measurements over a longer period of time.
Using a Geiger Counter to Measure Radiation
If you want to find out if items in your home are emitting radiation (for example, if you have a specific concern about your granite countertops), and in what amounts, you can use a Geiger counter.
A Geiger counter measures alpha, beta and gamma radiation. It won’t detect the presence of radon gas in your indoor air, however it can be a useful tool to locate the sources of radiation inside your home or other building.
What You Can Do To Reduce Radon Levels in Your Home
It is estimated that one in 15 homes has a radon level at or above the EPA action level of 4 pCi/L. Scientists estimate deaths from lung cancer could be reduced by two to four percent, or about 5,000 deaths, by lowering radon levels in homes exceeding the EPA’s action level.
You can reduce your own and your family’s health risk even further by lowering radon exposure in your indoor environments to levels well below EPA guidelines, and I would strongly encourage you to do so.
There are a variety of ways to reduce radon levels in your home, including:
Sealing cracks in floors and walls
Increasing ventilation through sub-slab depressurization with pipes and fans
Removing granite countertops if they are emitting high levels of radon
Replacing ionization smoke detectors with the photoelectric type
The cost of radon reduction measures depends on the size and design of your home and the specific methods needed. Costs range from $800 to $2,500, with an average cost of $1,200.
If you’re building a home or other structure, insist on building materials that are more resistant to the naturally occurring radon in the outdoor environment.
The five basic features of a radon-resistant home are:
Gravel laid below the foundation which allows radon in the soil to circulate freely underneath your house
Plastic sheeting or other vapor retarder laid over the gravel to stop soil gases from entering the structure
Vent pipe run vertically from the gravel layer up to the roof to safely vent radon from the soil outside the house
Sealing and caulking of all cracks, crevices and other openings in the concrete foundation and the walls of the structure
Electrical junction box installed in the attic for use with a vent fan, should one be needed
For more information on Radon-Resistant New Construction (RRNC), visit the EPA website at http://www.epa.gov/radon/rrnc/basic_techniques_builder.html.
 PubMed.gov, Health Phys. October 2009, Radon and leukemia in the Danish study: another source of dose
 PubMed.gov, Pancreas May 2009, Racial disparities in pancreatic cancer and radon exposure: a correlation study