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PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

This Public Health Statement is the summary chapter from the Toxicological Profile for Radon. It is one 

in a series of Public Health Statements about hazardous substances and their health effects. A shorter 

version, the ToxFAQsTM, is also available. This information is important because this substance may 

harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you 

are exposed, personal traits and habits, and whether other chemicals are present. For more information, 

call the ATSDR Information Center at 1-800-232-4636. 

This public health statement tells you about radon and the effects of exposure to it. 

The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the 

nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term 

federal clean-up activities. Radon has been found in at least 34 of the 1,699 current or former NPL sites. 

Although the total number of NPL sites evaluated for this substance is not known, the possibility exists 

that the number of sites at which radon is found may increase in the future as more sites are evaluated. 

This information is important because these sites may be sources of exposure and exposure to this 

substance may harm you. 

When a substance is released from a large area, such as an industrial plant, or from a container, such as a 

drum or bottle, it enters the environment. This release does not always lead to exposure. You are 

exposed to a substance only when you come in contact with it. You may be exposed by breathing, eating, 

or drinking the substance, or by skin contact. External exposure to radiation may occur from natural or 

man-made sources. Naturally occurring sources of radiation are cosmic radiation from space or 

radioactive materials in soil or building materials. Man-made sources of radioactive materials are found 

in consumer products, industrial equipment, atom bomb fallout, and to a smaller extent from hospital 

waste and nuclear reactors. 

If you are exposed to radon many factors will determine whether you will be harmed. These factors 

include the dose (how much), the duration (how long), and how you come in contact with it. You must 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

also consider any other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, and 

state of health. 

1.1 WHAT IS RADON? 

Radioactive gas Radon (Rn) is a naturally occurring colorless, odorless, tasteless radioactive 

gas that occurs in different forms with the same atomic number but different 

atomic mass, called isotopes. 

As radon undergoes radioactive decay, radiation is released predominantly 

by high-energy alpha particle emissions, which are the source of health 

concerns. 

Radon is measured in terms of its activity (curies or becquerels). Both the 

curie (Ci) and the becquerel (Bq) tell us how much a radioactive material 

decays every second (1 Ci = 37 billion Bq = 37 billion decays per second). 

Natural product 

of the 

environment 

Radon isotopes are formed naturally through the radioactive decay of 

uranium or thorium. 

Uranium and thorium (solids) are found in rocks, soil, air, and water. 

Uranium and thorium decay to other elements such as radium (a solid), 

which in turn decays into radon gas. 

Uranium and thorium have been present since the earth was formed and 

have very long half-lives (4.5 billion years for uranium and 14 billion years for 

thorium). The half-life is the time it takes for half of the atoms of a 

radionuclide to undergo radioactive decay and change it into a different 

isotope. Uranium, thorium, radium, and thus radon, will continue to exist 

indefinitely at about the same levels as they do now. 

Radon has no commercial uses. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

Exists in various 

forms called 

isotopes and 

decays to other 

radioactive 

isotopes 

The most common radon isotope is radon-222 (222Rn), which is part of the 

uranium decay chain. 

An atom of 222Rn gives off an alpha particle (which is the size of a helium 

atom without electrons), transforming into an atom of polonium-218 (218Po), 

which later gives off an alpha particle of its own, transforming into an atom of 

radioactive lead (214Pb). This process is called radioactive decay and radon 

decay products are called radon progeny or radon daughters. The final step 

in the radioactive decay of radon progeny results in the formation of an atom 

of stable lead which is not radioactive. 

The half-life of 222Rn is 3.82 days. Some of the radon decay products have 

the following half-lives: 218Po is 3.05 minutes; 214Pb is 26.8 minutes; and 

210Pb is 22.3 years. 

1.2 WHAT HAPPENS TO RADON WHEN IT ENTERS THE ENVIRONMENT?
 

Moves to air, 

groundwater, 

and surface 

water 

Radon gas in the rocks and soil can move to air, groundwater, and surface 

water. 

Decay products of 222Rn, such as 218Po and 214Pb, are solids that can attach 

to particles in the air and be transported this way in the atmosphere. They 

can be deposited on land or water by settling or by rain. 

Radon will undergo radioactive decay in the environment. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

1.3 HOW MIGHT I BE EXPOSED TO RADON AND RADON PROGENY?
 

Air Since radon progeny are often attached to dust, you are exposed to them 

primarily by breathing them in. They are present in nearly all air. Depending 

on the size of the particles, the radioactive particulates can deposit in your 

lungs and impart a radiation dose to the lung tissue. 

Background levels of radon in outdoor air are generally quite low, but can 

vary based on location and the underlying soil geology. 

In indoor locations, such as homes, schools, or office buildings, levels of 

radon and radon progeny are generally higher than outdoor levels and may 

be particularly high in some buildings, especially in newer construction that 

is more energy-efficient. 

Cracks in the foundation or basement of your home may allow increased 

amounts of radon to move into your home. Also, radon is heavier than 

ambient air, and therefore, the concentrations of radon are generally higher 

in the lower levels or basement of the homes. 

Water You may be exposed to radon and radon progeny by coming into contact 

with radon-contaminated surface or groundwater or by drinking water from 

wells that contain radon. 

Radon in water can become airborne; it is estimated that 1/1,000th of the 

radon in water may become airborne during indoor activities that use water. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

1.4 HOW CAN RADON AND RADON PROGENY ENTER AND LEAVE MY BODY? 

When they are 

inhaled or 

swallowed 

Radon and its radioactive progeny can enter your body when you breathe 

them in or swallow them. 

Most of the inhaled radon gas is breathed out again. 

Some of the radon progeny, both unattached and, attached to particles, 

may remain in your lungs and undergo radioactive decay. The radiation 

released during this process passes into lung tissue and can cause lung 

damage. 

Some of the radon that you swallow with drinking water passes through the 

walls of your stomach and intestine. 

After radon enters your blood stream most of the radon quickly moves to 

the lungs where you breathe most of it out. 

Radon that is not breathed out goes to other organs and fat tissue where it 

may remain and undergo decay. 

1.5 HOW CAN RADON AND RADON PROGENY AFFECT MY HEALTH? 

Scientists use many tests to protect the public from harmful effects of toxic chemicals and to find ways 

for treating persons who have been harmed. 

Lung cancer Many scientists believe that long-term exposure to elevated levels of radon 

and radon progeny in air increases your chance of getting lung cancer. 

The greater your exposure to radon, the greater your chance of developing 

lung cancer. 

Smoking cigarettes greatly increases your chance of developing lung 

cancer if you are exposed to radon and radon progeny at the same levels 

as people who do not smoke. Because tobacco is naturally sticky, many of 

the radon decay products actually stick to tobacco products. Therefore, 

when tobacco is smoked or otherwise used, these radon products may also 

enter your system. Breathing in other substances that cause lung cancer 

may also increase your chance of developing lung cancer from exposure to 

radon progeny. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

1.6 HOW CAN RADON AND RADON PROGENY AFFECT CHILDREN? 

This section discusses potential health effects in humans from exposures during the period from 

conception to maturity at 18 years of age. 

Differences 

between children 

and adults 

Smaller lungs and faster breathing rates in children may result in higher 

estimated radiation doses to the lungs of children relative to adults. 

However, limited information from children employed as miners in China do 

not provide evidence of increased susceptibility to the effects of exposure to 

radon. 

1.7 HOW CAN FAMILIES REDUCE THE RISK OF EXPOSURE TO RADON AND RADON 

PROGENY? 

Reduce indoor 

exposure levels 

Indoor radon levels can be reduced by methods that include the sealing of 

surfaces between the ground and the building and installation of ventilation 

systems that route air from materials under the building to outdoor air. 

Certified radon mitigation experts can be located by contacting your state 

health or environmental program. 

1.8 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED TO 

RADON AND RADON PROGENY? 

Radon decay 

products in urine 

and in lung and 

bone tissues 

Radon in human tissues is not detectable by routine medical testing. 

Some radon decay products can be detected in urine and in lung and bone 

tissue. Tests for these products are not generally available to the public 

and are of limited value since they cannot be used to accurately determine 

how much radon you were exposed to, nor can they be used to predict 

whether you will develop harmful health effects. 

1.9 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and recommendations to protect public health. Regulations 

can be enforced by law. Federal agencies that develop regulations for toxic substances include the 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

Environmental Protection Agency (EPA), the Occupational Safety and Health Administration (OSHA), 

the Food and Drug Administration (FDA), and the U.S. Nuclear Regulatory Commission (USNRC). 

Recommendations provide valuable guidelines to protect public health but cannot be enforced by law. 

Federal organizations that develop recommendations for toxic substances include the Agency for Toxic 

Substances and Disease Registry (ATSDR), the National Institute for Occupational Safety and Health 

(NIOSH), and the FDA. 

Regulations and recommendations can be expressed as “not-to-exceed” levels, that is, levels of a toxic 

substance in air, water, soil, or food that do not exceed a critical value that is usually based on levels that 

affect animals; they are then adjusted to levels that will help protect humans. Sometimes these not-toexceed levels differ among federal organizations because they used different exposure times (an 8-hour 

workday, a 24-hour day, or a work-year), different animal studies, or other factors. 

Recommendations and regulations are also updated periodically as more information becomes available. 

For the most current information, check with the federal agency or organization that provides it. 

Air EPA recommends fixing your home if measured indoor levels of radon are 

4 or more pCi per liter (pCi/L) of air EPA also notes that radon levels less 

than 4 pCi/L still pose a health risk and can be reduced in many cases. The 

EPA recommends using a certified radon mitigation specialist if indoor radon 

levels need to be reduced to ensure that appropriate methods are used to 

reduce radon levels. 

The Mine Safety and Health Administration (MSHA) has adopted an 

exposure limit of 4 Working Level Months (WLM) per year for people who 

work in mines (WLMs basically combine the concentration of radon in mine 

air with length of exposure inside the mine). 

The Nuclear Regulatory Commission published a table of allowable 

exposure to radon by workers and allowable releases of radon to the 

environment by its licensees. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov 
______________________________________________________________________________ 

PUBLIC HEALTH STATEMENT 

Radon 

CAS # 14859-67-7 

Division of Toxicology and Environmental Medicine September 2008 

Water In the 1990s, EPA introduced a proposal to limit levels of radon in drinking 

water. As of August 2008 the proposal had not been adopted as a 

regulation. 

1.10 WHERE CAN I GET MORE INFORMATION? 

If you have any more questions or concerns, please contact your community or state health or 

environmental quality department, or contact ATSDR at the address and phone number below. 

ATSDR can also tell you the location of occupational and environmental health clinics. These clinics 

specialize in recognizing, evaluating, and treating illnesses that result from exposure to hazardous 

substances. 

Toxicological profiles are also available on-line at www.atsdr.cdc.gov and on CD-ROM. You may 

request a copy of the ATSDR ToxProfilesTM CD-ROM by calling the toll-free information and technical 

assistance number at 1-800-CDCINFO (1-800-232-4636), by e-mail at cdcinfo@cdc.gov, or by writing 

to: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology and Environmental Medicine 

 1600 Clifton Road NE 

 Mailstop F-32 

 Atlanta, GA 30333

 Fax: 1-770-488-4178
 

Organizations for-profit may request copies of final Toxicological Profiles from the following: 

National Technical Information Service (NTIS) 

5285 Port Royal Road

 Springfield, VA 22161
 

Phone: 1-800-553-6847 or 1-703-605-6000
 

Web site: http://www.ntis.gov/
 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-800-232-4636 Fax: 770-488-4178 E-Mail: cdcinfo@cdc.gov