What is Radon? Radon is a gaseous radioactive element having the symbol Rn, the atomic number 86, an atomic weight of 222, a melting point of -71ºC, a boiling point of -62ºC, and (depending on the source, there are between 20 and 25 isotopes of radon – 20 cited in the chemical summary, 25 listed in the table of isotopes); it is an extremely toxic, colorless gas; it can be condensed to a transparent liquid and to an opaque, glowing solid; it is derived from the radioactive decay of radium and is used in cancer treatment, as a tracer in leak detection, and in radiography. (From the word radium, the substance from which it is derived.) Sources: Condensed Chemical Dictionary, and Handbook of Chemistry and Physics, 69th ed., CRC Press, Boca Raton, FL, 1988.
Where does radon come from? Radon-222 is the radioactive decay product of radium-226, which is found at low concentrations in almost all rock and soil. As radon is generated in rock and soil it creeps up to the outside air. Although outdoor concentrations of radon are typically low, about 0.4 picocuries per liter (pCi/l) of air, it can seep into buildings through foundation cracks or openings and build up to much higher concentrations indoors.
Who discovered radon was a problem in our homes? Radon itself was first discovered by scientists around 1900. It wasn’t until 1984 when a nuclear plant worker in Pennsylvania set off the radiation detectors leaving the plant that the medical community nationwide became aware of radon in our homes. Investigation revealed the radiation was from radon in the workers home!
The average national indoor radon concentration is about 1.3 pCi/l of air. It is not uncommon for indoor radon levels to be found in the range of 5 – 50 pCi/l, and they have been found as high as 2,000 pCi/l.
- Around Chicagoland we’ve found levels in excess of 150pCi/l.
The concentration of radon measured in a house depends on many factors, including the design of the house, the heating and ventilation systems, local geology and soil conditions, and the weather.
Radon is the second leading cause of lung cancer. There is no safe level of radon–any exposure poses some risk of cancer. In two 1999 reports, the National Academy of Sciences (NAS) concluded after an exhaustive review that radon in indoor air is the second leading cause of lung cancer in the U.S. after cigarette smoking. The NAS estimated that 15,000-22,000 Americans die every year from radon-related lung cancer. That’s 10% of all lung cancer deaths annually.
The alpha radiation from radon and its decay products cause damage to sensitive lung tissue. Most of the radiation dose is not actually from radon itself, but rather from radon’s chain of short-lived solid decay products that are inhaled and lodge in the airways of the lungs. These radionuclides decay quickly, producing other radionuclides that continue damaging the lung tissue. Those particles that are retained long enough release radiation damaging surrounding lung tissues. It is this damage that causes lung cancer.
Smokers, former smokers, & second-hand smokers are at increased risk. Radon decay products also cling to tobacco leaves, which are sticky, during the growing season, and enter the lungs when tobacco is smoked.
Smoke in indoor environments also is very effective at picking up radon decay products from the air and making them available for inhalation. It is likely that radon decay products contribute significantly to the risk of lung cancer from cigarette smoke
What about children…are they at increased risk? Children have been reported to have greater risk than adults for certain types of cancer from radiation, but there is currently no conclusive data on whether children are a greater risk than adults from radon.
Minimizing radon exposure should start as early as possible.
How do we know radon is a carcinogen? The World Health Organization (WHO), the National Academy of Sciences, the US Department of Health and Human Services, as well as the US 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.
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., there are no large extrapolations involved in estimating radon risks in homes.
What are the chances of dying from lung cancer caused by radon? Radon exposure significantly increases your risk of dying from lung cancer, but just as not everyone who smokes will get lung cancer, not everyone exposed to high levels of radon will get lung cancer. The following is the “EPA Assessment of Risks from Radon in Homes” an updated chart of the lifetime risk of lung cancer death per person from radon exposure in homes. The full text of the updated risk assessment, “EPA Assessment of Risks from Radon in Homes” (EPA 402-R-03-003) is available as a downloadable Adobe Acrobat file.
Can a medical test tell what someone’s exposure has been or how much damage has been done? Several decay products can be detected in urine, blood, and lung and bone tissue. However, these tests are not generally available through typical medical facilities. Also, they cannot be used to determine accurate exposure levels, since most radon decay products deliver their dose and decay within a few hours. Finally, these tests cannot be used to predict whether a person’s exposure will cause harmful health effects, since everyone’s response to exposure is different.
The best way to assess exposure to radon is by measuring concentrations of radon (or radon decay products) in the air you breathe at home.