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Frequently Asked Questions
Radon and Indoor Air Program
- For Florida Information: 850-245-4288 or 800-543-8279
Florida Department of Health
Bureau of Environmental Health, Radon Program
4052 Bald Cypress Way, Bin A08
Tallahassee, FL 32399-7017
*Note: This page contains materials in the Portable Document Format (PDF). The free Adobe Reader may be required to view these files.
What is radon?
Radon is a colorless, odorless, tasteless, invisible and chemically inert gas that comes from the decay of radium in the soil. Radium is a decay product of uranium. Uranium is present in almost all rocks and soil and material derived from rocks.
Where does radon come from?
Radon is constantly being generated by the radium in rocks, soil, water and materials derived from rocks and soils. The radon generated in rocks or water usually stays trapped in that material unless the rocks are fractured or the water is mixed with the air. Radon-222 is the decay product of radium-226. Radon-222 and its parent, radium-226, are part of the long decay chain for uranium-238. Since uranium is essentially everywhere in the earth's crust, radium-226 and radon-222 are present in almost all rock and all soil types.
The amount of radon soil can produce depends on local geology and can vary from house to house. Radon levels in the soil range from a few hundred to several thousand pCi/L (picoCuries per Liter). The amount of radon that escapes from the soil to enter the house depends on the suction created within the house, soil porosity, soil moisture, and the weather.
What is the average level of Radon found in homes in the U.S.?
Based on a national residential radon survey completed in 1991, the average indoor radon level in the United States is about 1.3 picoCuries per liter (pCi/L). The average outdoor level is about 0.4 pCi/L.
What is the extent of radon problems in Florida?
The department collects radon test reports from state certified radon testing companies. About 1 in 5 radon tests made in Florida are found to be elevated. Locally the number of homes reporting elevated radon varies from a high of 7 out of 10 to a low of 1 out of 100. Elevated radon levels have been reported from all regions of the state. Ultimately the only way to tell if your home has a radon problem is to test for it.
What does pCi/L mean?
PicoCuries per liter (pCi/L) is a unit for measuring radioactive concentrations. The curie (Ci) unit is the activity of 1 gram of pure radium-226. Pico is a scientific notation denoting a factor of 10-12.
One pCi is one trillionth of a Curie, 0.037 disintegrations per second, or 2.22 disintegrations per minute. Therefore, at 4 pCi/L (picoCuries per liter, the EPA's recommended action level), there will be approximately 12,672 radioactive disintegration events in one liter of air during a 24-hour period.
Why is 4 pCi/L the recommended action level for Radon?
EPA recommended this action level in 1986 for several reasons. First, at lower levels (< 2 pCi/L) measurement devices’ false negative errors increased threefold, and false positive errors increased twofold. Secondly, mitigation research indicates that elevated levels can be reduced to less than 4 pCi/L 95% of the time. Research shows that 2 pCi/L can be achieved 70% of the time. Further, today’s mitigation technology can reduce radon levels to between 2 and 4 pCi/L most of the time. Finally, cost benefit analysis performed in 1986 indicate that an action level of 4 pCi/L results in a cost of about $700,000 per lung cancer death saved. If the action level was set at 3 pCi/L, the cost would be $1.7 million, and if set at 2 pCi/L, the cost would be $2.4 million per lung cancer death saved. EPA states that 4 pCi/L is a recommended action level, yet homeowners can further reduce their potential lung cancer risk by mitigating homes that are below 4 pCi/L.
Does Radon break down and disappear from a building?
Radon does decay (break-down); however, the ability for any given patch of land to produce a radon problem in a building placed on it is effectively constant during your life time.
Radon 222 is a radioactive element in the Uranium 238 decay chain. The 'parent' element to radon is Radium 236. While radon has a half-life of 3.8 days and thus decays out rather quickly, Radium 226 has a half-life of 1620 years. Any radon in the ground is continually being replenished by the decay of the radium in the soil. With a half life of 1620 years, the amount of radium and the rate of radon production during an individual's life, or the design life expectancy of your average building, is effectively constant. Radon is constantly generated and available to enter and accumulate in buildings at high concentrations.
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Health Effects and Evidence
What are the symptoms and health risks associated with radon exposure?
There are no immediate symptoms associated with radon. However, chronic exposure to elevated radon levels has been demonstrated to cause an increased incidence of lung cancer in humans. The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States, estimated to cause about 21,000 deaths each year. Radon is also the leading cause of lung cancer among non-smokers. Major scientific organizations continue to estimate that approximately 12% of lung cancers annually in the United States are attributable to radon. When radon and its decay products are inhaled into your lungs, they emit particles full of energy called alpha particles. These alpha particles can strike the sensitive lining of the lungs (bronchi). When this happens, the cells and their DNA in your lungs are damaged, increasing your risk of developing lung cancer. Most of the alpha particle radiation comes from radon decay products. Lung cancer is the only health effect which has been definitively linked with radon exposure. Lung cancer usually occurs after prolonged exposure (10-25 years). Smokers are at higher risk of developing radon-induced lung cancer, so prevention is the best defense. People should not smoke and also reduce the amount of radon they breathe.
What are the health effects associated with radon?
The Surgeon General has warned that radon is the second leading cause of lung cancer, and the leading cause of lung cancer among non-smokers in the United States. Lung cancer is a disease that has a very poor survival rate. When radon and its decay products are inhaled into your lungs they emit particles full of energy called alpha particles. These alpha particles can strike the sensitive lining of the lungs (bronchi). When this happens, the cells and their DNA in your lungs are damaged, increasing your risk of developing lung cancer. Most of the alpha particle radiation comes from radon decay products. Lung cancer is the only health effect which has been definitively linked with radon exposure. Lung cancer would usually occur after prolonged exposure (10-25 years). Note that radon is the leading cause of lung cancer among non-smokers.
Is there any evidence on the health effects associated with radon?
The World Health Organization (WHO), the National Academy of Sciences, the US Department of Health and Human Services, as well as EPA, have classified radon as a known human carcinogen, because of the wealth of biological and epidemiological evidence and data showing the connection between exposure to radon and lung cancer in humans. 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 the 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 U.S. EPA estimates that radon causes about 21,000 lung cancer deaths per year.
There have been many studies conducted by many different organizations in many nations around the world to examine the relationship of radon exposure and human lung cancer. The largest and most recent of these was an international study, led by the National Cancer Institute (NCI), which examined the data on 68,000 underground miners who were exposed to a wide range of radon levels. The studies of miners are very useful because the subjects are humans, not rats, as in many cancer research studies. These miners are dying of lung cancer at 5 times the rate expected for the general population. Over many years scientists around the world have conducted exhaustive research to verify the cause-effect relationship between radon exposure and the observed increased lung cancer deaths in these miners and to eliminate other possible causes. In addition, there is an overlap between radon exposures received by miners who got lung cancer and the exposures people would receive over their lifetime in a home at EPA's action level of 4 pCi/L, i.e., the lung cancer risk in miners has been documented at exposure levels comparable to those which occur in homes/residences. The scientific experts agree that the occupational miner data is a very solid base from which to estimate risk of lung cancer deaths annually. While residential radon epidemiology studies will improve what we know about radon, they will not supersede the occupational data.
Are there any residential epidemiology studies finding increased risk of lung cancer due to radon?
Yes, several residential epidemiology studies have found an increased risk of lung cancer due to residential exposures (i.e. Sweden, New Jersey, Iowa) These studies are also just pieces of a much bigger puzzle that is being put together. The National Academy of Sciences' Biological Effects of Ionizing Radiation (BEIR VI) Report examines in detail the available studies of radon and lung cancer in homes, as well as the studies of underground miners.
Why are residential epidemiology studies of radon so complicated?
There are many factors that must be considered when designing a residential radon epidemiology study. It is very expensive and often impossible to design a study that takes all the pertinent factors into consideration. These factors include:
■Mobility: people move a lot over their lifetime; it is virtually impossible to go back and test every home where an individual has lived;
■Housing Stock Changes: over time, older homes are often destroyed or remodeled, thus radon measurements will be non-existent or highly varied; a home's radon level may change, over time if new ventilation systems are installed, the occupancy patterns are substantially different, or the home's foundation shifts or cracks appear.
■Inaccurate Histories: often a majority of the lung cancer cases (individuals) being studied are deceased or too sick to be interviewed by researchers. This requires reliance on second-hand information which may not be as accurate. These inaccuracies primarily affect:
■Residence History: a child or other relative may not be aware of all residences occupied by the patient - particularly if the occupancy is distant in time or of relatively short duration. Even if the surrogate respondent is aware of a residence they may not have enough additional information to allow researchers to locate the home.
■Smoking History: smoking history historically has reliability problems. Individuals may under-estimate the amount they smoke. Conversely, relatives or friends may over-estimate smoking history.
■Other: complicating factors other than variations in smoking habits include an individual's: genetics, lifestyle, exposure to other carcinogens, and home heating, venting and air conditioning preferences.
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Sources of Radon Entry Routes
How does radon get into a building?
Most indoor radon comes into the building from the soil or rock beneath it. Radon and other gases rise through the soil and get trapped under the building. The trapped gases build up under the house. Air pressure inside homes is usually lower than the pressure in the soil. Therefore, the home acts as a vacuum cleaner suctioning radon and other gases from under the building, forcing gases through floors and walls and into the building. Most of the gas moves through cracks and other openings. Once inside, the radon can become trapped and concentrated. Openings, which commonly allow easy flow of the gases in, include the following: cracks in floors and walls; gaps in suspended floors; openings around sump pumps and drains; cavities in walls; joints in construction materials; gaps around utility penetrations (pipes and wires); and crawl spaces that open directly into the building.
As almost all soils have traces of radium, so do all earthen building materials such as concrete and stone. It is possible to build radon into the building under the right conditions. For most Florida structures, building materials contribute less radon to the indoor air than the outdoor air ambient radon level does. More recent developments in housing construction has created radon problems due solely to radon released from building materials. Residences built entirely of concrete and with fresh air entry less than a two thirds the recommended amount for healthy indoor air, have been found to have building material related radon problems. Because of this phenomenon, Floridians have found elevated radon levels through all floors of high rise multi-family buildings.
Radon may also be dissolved in water, particularly well water. Radon gets released as it aerates inside the house (in the shower, faucets, washing machines). However, the water needs to have at least 10,000 picoCuries per liter to generate 1 pCi/l in the air. Therefore, the more radon there is in the water, the more it can contribute to the indoor radon level.
Trace amounts of uranium are sometimes incorporated into materials used in construction. These include, but are not limited to concrete, brick, granite, and drywall. Though these materials have the potential to produce radon, they are rarely the main cause of an elevated radon level in a building.
While radon problems may be more common in some geographic areas, any home may have an elevated radon level. New and old homes, well-sealed and drafty homes, and homes with or without basements can have a problem.
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Who can test a building for radon?
Florida Certified radon measurement businesses can test your home for radon. Homeowners may also test their house using over-the-counter (OTC) radon proficient devices available at local home improvement stores or through the internet. The OTC kits are simple to use and are relatively inexpensive (around $20 for short term tests and around $50 for long term tests). To purchase a do-it-yourself kit, check with your local home improvement hardware store or discount department store. Frequently they display radon test kits with the lead test kits, smoke alarms and carbon monoxide detectors. Reliable radon test kits are listed with the National Radon Proficiency Program or the National Radon Safety Board. Additionally, any test kit purchased and deployed needs to be returned to the laboratory for analysis. If you cannot find test kits available locally, search and purchase one online.
Another option is to hire a state certified radon testing company. Anyone offering professional radon services must have a Florida Department of Health Radon Certification. See a complete list of Radon Measurement Businesses by County Need more options? Consider looking at businesses that have 'statewide' as their service area. Some companies have specialists and technicians in several areas or travel to different parts of the state as part of their normal business.
Where can I find a list of certified Radon Companies or Inspectors?
A complete list of Radon Measurement Businesses by County can be found at our Florida certified radon measurement business list. If you decide you want more options, consider looking at businesses that have 'statewide' as their service area. Some of those companies have specialists and technicians in several areas or travel to different parts of the state as part of their normal business.
My home was recently tested for radon by a person that is not listed on your website as being "certified". Could they be certified if they are not on your list? Can I report them if they are not certified?
Every person hired to test or fix radon problems must be certified by the Florida Department of Health. Please report any violations to 1-800-543-8279. It is possible that the person may be a new specialist who has not been added to our website, so please ask us and we will be glad to check our database.
Is it hard to test for radon? How long does it take to test for Radon?
Testing by a Florida Certified radon measurement businesses is easy. Test kits have easy to follow directions. Testing is as simple as opening a package, placing a radon detector in your home in a designated area, and, after the prescribed number of days, sealing the detector back in the package and mailing it to a lab. The whole process only takes a few minutes of your time! If you conduct the test as specified you should obtain accurate results.
Do I still need to test my home if I don't live in an area designated as a high radon zone?
Yes. The only way to know for sure if you have a radon problem, and to protect your family from radon, is to test your home. Various federal and state agencies have conducted radon surveys through the United States. In addition, the EPA has broken the state down into three zones according to their potential for high indoor radon levels, with Zone 1 having the highest radon potential. Homes in Zones 1 and 2 have a statistically higher chance of having elevated levels of radon. However, elevated levels of radon have been found in homes in many counties designated as low radon potentials (zone 3).
Do I need to test if my neighbors have tested their homes for radon and they don't have high levels?
Yes. Radon levels can vary greatly 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 can 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.
How can I find out if houses or buildings in my area have reported having elevated levels of Radon?
The only way to know if a particular structure has elevated radon levels is to test it. Radon problems are found throughout Florida and no area is immune to it. The Department of Health does provide zip code based statistics of radon levels in buildings in Florida. You may visit our Radon Data by Zip Code page, to view information on radon testing results for other zip codes. This data is taken from reports submitted by state certified radon testing companies, and may not be up to date (for the latest information call 1-800-543-8279). As such, it is not based on any scientific sampling methodology but sampling driven solely by those willing to pay for professional radon testing. This data cannot be used to predict radon levels in untested properties.
As a Realtor, I have been told by home inspectors that my county has elevated radon levels. How can I addresses this with my clients?
Radon is found everywhere, and the only way to know the levels in any particular building is to test that structure. Florida Statute 404.056(5) requires the following notification about radon in real estate transactions: "RADON GAS: Radon is a naturally occurring radioactive gas that, when it has accumulated in a building in sufficient quantities, may present health risks to persons who are exposed to it over time. Levels of radon that exceed federal and state guidelines have been found in buildings in Florida. Additional information regarding radon and radon testing may be obtained from your county health department." Radon is like any other issue encountered in a real estate transaction, and elevated levels can be reduced. To further discuss radon measurement in real estate transactions or for any other issues please call 1-800-543-8279.
What do I do if my test results are greater than 4 pCi/L?
For real estate transactions: follow mitigation guidance as outlined in the US EPA Homebuyers and Sellers Guide to Radon.
For short term test:
■If your results are below 4 pCi/L, continue testing your home every 2 years.
■If your results were twice the EPA Action level or greater, it is suggested that you perform another radon test in the same area and for the same duration, and then average the results of the 2 tests.
■If the average of these two tests is below 4 pCi/L, then retest your home every 2 years.
■If the average is above 4 pCi/L, consult with a certified mitigator regarding your next step.
■If the result is above 4 pCi/l but less than 8 pCi/l, choose between either a short term or a long term follow-up test. A long term test would be preferred. A long term test lasts over 91 days and provides a better representation of the long term average radon concentration in your home. It takes into account variations in radon concentration that naturally occur over time.
■If the follow up test result is over 4 pCi/L, consult with a certified mitigator regarding your next step.
Long term test:
■If the result is less than 4 pCi/L, continue testing your home every 2 years.
■If the result is greater than 4 pCi/L, it is suggested that you perform another short term test in the same area and average the results.
■If the results of both tests or the average of both tests are greater than 4 pCi/L, consult with a certified mitigator regarding your next step.
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Can a radon problem be fixed?
Yes. The solution is simple and relatively inexpensive. However, the best solution depends on the size and nature of the radon risk. If radon levels are low, ventilation and sealing of cracks on the floor may solve the problem. Other situations may require active mitigation systems. The "standard" active mitigation system, that usually involves soil depressurization, costs about $1200 to $2000 installed. Other systems may cost over $3000.
How do I determine if I need mitigation?
The only way to know if a home or building has high radon levels is to test it following the appropriate testing protocols. This applies to buildings with a mitigation system, buildings built radon resistant or buildings that have never been tested. Test buildings that have low levels at least every five years to make sure something in the building has not changed that would require radon mitigation. The same applies to buildings built radon resistant. Radon resistance does not guarantee that no radon problem will ever occur. It significantly decreases the chances and makes it easier to correct. Buildings with installed mitigation systems should be tested at least every other year. This is to ensure that the mitigation system is working appropriately and does not need to be adjusted.
■If the home does not have a mitigation system:
■Test for radon
■If the results are > 4 pCi/l retest and install a mitigation system by a certified mitigation professional
■If the home was built using radon resistant techniques:
■Test for radon to verify if radon concentrations are less than 4 pCi/l
■If the results are > 4 pCi/l consider hiring a state certified mitigation professional
■If the home has an installed mitigation system:
■Test for radon to verify if radon concentrations are less than 4 pCi/l
■If the results are > 4 pCi/l consider hiring a state certified mitigation professional
How do I select a radon mitigation contractor?
Select a mitigation business as you would select any other contractor:
■Go to our website to determine who is certified to provide mitigation services
■Get various estimates
■Ask mitigation contractor for references and proof of current state certification
■Ask mitigation contractor to explain the work to be done
■Does the contractor charges any fees in addition to the cost of mitigation
■Does the estimate include the installation of a warning device to inform you if the radon reduction system is not working correctly?
■Did contractor review the quality of previous radon measurements results
■Does the contractor has liability insurance?
■Does the contractors guarantees a reduction in radon levels to less than 4 pCi/L, and for how long?
■Consider businesses that have 'statewide' as their service area. Some companies have specialists in several areas or travel to different parts of the state as part of their business practice
How can you find a qualified radon service professional in your area?
If you are interested in finding a qualified radon service professional to test or mitigate your home or you need to purchase a radon measurement device, contact the Florida Department of Health Radon Program at 1-800-543-8279 or at 850-245-4288. The website maintains a list of certified measurement and mitigation contractors. Many of the mitigators indicate they are willing to travel statewide to fix a radon problem.
My home was mitigated for radon by a person that is not listed on your website as being "certified". Could they be certified if they are not on your list? Can I report them if they are not certified?
Every person hired to mitigate radon problems must be certified by the Florida Department of Health. Please report any violations to 1-800-543-8279. It is possible that the person may be a new specialist who has not been added to our website, so please ask us and we will be glad to check.
What should I look for in a radon mitigation contract?
You need to find out several things in addition to the total cost of mitigation including taxes and permit fees if applicable:
■Do I need to pay a deposit?, when is the final payment due?
■How much time is needed to complete the work
■Contractor agreement to obtain necessary permit and follow building codes
■Statement that contractor carries liability insurance and is bonded and insured
■A guarantee that the contractor will be responsible for damages and clean-up after the job
■Details of warranties, guarantees, optional features, including acceptable resulting radon levels
■Are warranties transferable if you sell your home
■Description of what is expected of the homeowner before the work begins
What are some of the radon mitigation methods?
There are several mitigation methods available:
■Active slab depressurization is the most common and reliable method. Pipes are inserted through the floor slab. A fan is connected to the pipe, which then suctions radon and other gases before these enter the home.
■Sub-membrane depressurization is similar to the active slab depressurization, and is used in crawl spaces.
■Sealing cracks and other openings in the foundation may limit the flow of radon gas into the home. Yet, sealing alone may not be sufficient to reduce radon levels consistently.
■Building pressurization uses a fan to blow air into the structure to create enough pressure and prevent radon from entering a home. This method may be less energy efficient and is limited by house construction, occupant life styles and environmental variables such as the average and maximum of the outdoor humidity level and of the indoor-outdoor temperature difference. Problems may arise if uncontrolled excessive moisture is introduced.
■For radon problems in tightly constructed all concrete and high-rise buildings, controlled mechanical ventilation is appropriate.
What are some of the standard radon mitigation system requirements?
There are some basic requirements that all radon reduction systems should meet:
■A radon reduction system must be clearly and visibly labeled
■Soil suction systems must vent at least 10 feet above the ground and away from windows, doors, or other openings.
■The exhaust fan must be located in an unlivable area (in an unoccupied attic, or if outside must be a for exterior use fan).
■A warning device must be visible or audible in order to alert owner if system stops working properly.
■A follow up test must be done by an independent contractor no earlier than 24 hours after the mitigation system is installed.
We had a high radon reading that was mitigated. However we did not test again right away and now it is still high. Is there anything we can do to lower these level?
Ultimately, you want the average annual radon level to be as low as reasonably achievable, and at least below 4 pCi/l. Additional follow-up testing should be conducted after every mitigation to determine if the radon levels were sufficiently reduced or if the system has to be modified by the mitigator. Sometimes the mitigator may have to come 2 or 3 times to ensure the system achieves sufficient radon reduction.
I recently moved, and discovered that there is a Radon Reduction System installed, but it doesn't seem to be functioning. Can you explain this?. Are there any statutes in effect regarding Radon and rental units?
Radon mitigation systems can be passive (do not use power) or active. It may be likely that your system has a fan that is not functioning. The only way to know the current radon levels in your home is to test. If you determine the levels to be high contact a mitigation company to check your radon fan and the entire system. The Florida Statutes (404.056) require the following disclosure: NOTIFICATION ON REAL ESTATE DOCUMENTS.--Notification shall be provided on at least one document, form, or application executed at the time of, or prior to, contract for sale and purchase of any building or execution of a rental agreement for any building. Such notification shall contain the following language: "RADON GAS: Radon is a naturally occurring radioactive gas that, when it has accumulated in a building in sufficient quantities, may present health risks to persons who are exposed to it over time. Levels of radon that exceed federal and state guidelines have been found in buildings in Florida."
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Contact the Florida Department of Health Radon Program at 1-800-543-8279 or 850-245-4288 or visit our website