RADON - The Hidden Environmental Hazard

Feb 5, 2011 | The HWN Team | Insider
RADON - The Hidden Environmental Hazard

image by: Eneko Lakasta

Radon exposure is the leading cause of lung cancer in non-smokers. Instead of being worried about airport scanners and pat-downs, perhaps we ought to be paying more attention to ensuring that our homes are as safe as possible!

Every year, thousands of people die of lung cancer. The majority of lung cancer cases are linked to cigarette smoking and exposure to occupational carcinogens such as asbestos. Yet, there are non-smokers who still develop lung cancer. According to the U.S. Environmental Agency (EPA), a gas called radon is “the leading cause of lung cancer deaths among non-smokers in America and claims the lives of about 20,000 Americans each year." On a global scale, radon is estimated to cause 3 to 14% of all lung cancers.1,2

Radon (Rn) is a colorless, odorless, tasteless gas.  Sounds harmless enough. However, radon is radioactive, highly carcinogenic and occurs naturally in the environment. Radon is formed when uranium or thorium found in rocks, soil, air and water undergoes radioactive decay. The fact that we can’t see, smell, or taste it makes it even more dangerous because it can be present in dangerous levels in the environment without us being aware of it.

The main source of radon in our environment is the soil. However we primarily come in contact with radon when radon particles are released from the soil into the air and attach to dust particulates.  Radon may also be deposited in surface or ground water. Drinking water from wells and springs can easily be contaminated. The radon in the water can easily become airborne especially when we perform water-using activities indoors.

The radioactivity of radon is measured in the same way as other radioactive compounds – in units of curie (Ci) or becquerel (Bq).“ Based on a U.S. EPA national residential radon survey completed in 1991, the average indoor radon level is about 1.3 picocuries per liter (pCi/L) and the average outdoor level is about 0.4 pCi/L. Radon levels of 4 pCi/L or higher in a residence necessitates mitigation and levels above 2pCi/L should already be a warning sign.

At the international level, the World Health Organization (WHO) estimates radon outdoor levels to be between 5 and 15 Bq/m 3 and indoor radon levels of 200–400 Bq/m 3 are usually used as the reference level for mitigation.  WHO also reports that radon concentrations of 20 Bq/l to more than 100 Bq/l have been measured in water supplies of some countries

So, is there radon in my house?

Maybe. Radon potential is based on 5 factors:

  • indoor radon measurements
  • geology
  • aerial radioactivity
  • soil permeability
  • foundation type

The danger comes when radon accumulates to toxic levels. Levels are higher indoors than outdoors and may accumulate inside buildings, including our homes, offices and schools.. Because radon is heavier than air, it usually accumulates in the lower levels of a building, such as the basement or cellar. Aside from normal air exchange, cracks in the foundation or basement of buildings, drains, sumps, and pores in building materials may be the point of entry of radon from rock or soil. 

Ironically, newer buildings may actually be more prone to high radon levels because of better isolation used for energy efficiency. And, there are even reports that our beautiful granite counters may be a major source of radon in our homes – who knew? 

Radon levels differ from place to place. Several countries including the UKCanada and the U.S. have extensive information on ‘radon zones’. The U.S. EPA has come up with 3 distinct radon zones in the United States with zone 1 having the lowest radon levels whereas in Zones 2 and 3 there are literally thousands of individual homes with elevated radon levels. 3

At the international level, the WHO launched the International Radon Project (IRP) in 2005 together with key partner agencies from over 40 member countries. The ITP working groups “collect and analyze information on radon risk, radon policies, radon mitigation and prevention as well as radon risk communication. 4

Evidence has been accumulating that long-term exposure to high levels of radon and its progeny is linked to cancer.  

As radon decays radioactively, it releases radiation, mainly high-energy alpha particles. Radon that gets deposited in our body decays in our tissues and release the high-energy alpha particles which are highly carcinogenic. 5

ATSDR describes how radon enters, decays or leaves our body.

  • 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 dust, 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.

Current data show that lung cancer is the type of cancer most commonly associated with radon exposure. Since the respiratory system is the usual point of entry of radon the lung tissues are the most likely part of the body where radon accumulates, decays, and causes the most damage. The Iowa Radon Lung Cancer Study investigated the effect of residential radon in a population-based, case-control epidemiologic study of female Iowan residents. 6

The study participants lived in the same house for at least 20 years. The results of the study indicate that long-term exposure to “ambient” levels of radon in the long run presents and important environmental hazard associated with increased lung cancer risk. And people who spend prolonged periods of time in enclosed spaces underground are more likely to be exposed to radon such as miners and workers in tunnels.

Of interest, intake of radon-contaminated water may cause damage to the tissues of the digestive system but the risk is quite low. Research has shown that your risk of lung cancer from breathing radon in air is much larger than your risk of stomach cancer from swallowing water.

Children are highly susceptible to radon toxicity, mainly because they have smaller lungs and faster respiration rates, leading to “higher estimated radiation doses to the lungs of children relative to adults.” However, radon data on children is limited. Recent studies indicate that radon exposure may play a role in the development of the blood cancer leukemia, especially in children. Radon seems to interact with traffic-generated air pollution to increase childhood leukemia risk.7

The U.S. Surgeon General, Health Canada, and UK Radon all recommend that homes be tested for radon. 

There are many ways of radon testing. The short-term test ranges from 48 hours to 90 days, whereas the long-term test last for more than 90 days. The short-term test gives faster results but the long-term test is more reliable as it measures year-round radon levels. Depending on the country, radon test kits are given out for free or at very low cost. Test kits can be purchased at home improvement stores or online in Canada, the U.S. and the UK. Professional testing is also offered by contractors and privately-run radon programs.

Resources are available for Canada and the UK.  U.S. resources include The National Environmental Health Association National Radon Proficiency Program and the National Radon Safety Board.

So, how do you mitigate your personal radon exposure?

There are many techniques that can help reduce radon levels in already existing homes or still to be constructed homes. Some of these are:8

Sealing cracks. In old or already existing structures, the basement should be checked for cracks. Sealing cracks and other openings in the foundation of a building can help reduce entry of radon gas.

Natural ventilation. Routine airing of rooms can lower radon levels, but only temporarily because the levels return to previous values after a couple of hours.

Home or room pressurization. Radon can enter a home because air pressure indoor is lower than the soil surrounding its foundation. Home pressurization “uses a fan to blow air into the basement, or living area from either upstairs or outdoors. It attempts to create enough pressure at the lowest level indoors — in a basement, for example — to prevent radon from entering into the home.”

Heat recovery ventilator, or HRV, also called an air-to-air heat exchanger. “An HRV will increase ventilation by introducing outdoor air while using the heated or cooled air being exhausted to warm or cool the incoming air. HRVs can be designed to ventilate all or part of your home, although they are more effective in reducing radon levels when used to ventilate only the basement. If properly balanced and maintained, they ensure a constant degree of ventilation throughout the year. HRVs also can improve air quality in homes that have other indoor pollutants. There could be a significant increase in the heating and cooling costs with an HRV, but not as great as ventilation without heat recovery.”

Soil suction prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe, or pipes, to the air above the home where it is quickly diluted. The type of suction used depends on the type of home foundation and is usually installed during construction. Thus, this technique is for houses still to be constructed.

The Bottom Line

When it comes to radon exposure your government agencies are right on the money! Instead of being worried about airport full body scanners and pat-downs, perhaps we ought to be paying more attention to ensuring that our homes are as safe as possible!   

Published February 05, 2011, updated June 30, 2012


  1. Radon, EPA
  2. Radon and cancer, WHO Sept 2009
  3. Map of Radon Zones, EPA
  4. Zielinski JM, World Health Organization's International Radon Project, J Toxicol Environ Health A. 2006 Apr;69(7):759-69
  5. Van Dillen T et al, Lung Cancer from Radon: A Two-Stage Model Analysis of the WISMUT Cohort, Radiat Res. 2010 Oct 5
  6. Field RW et al, Residential Radon Gas Exposure and Lung Cancer, The Iowa Radon Lung Cancer Study, Am J Epidemiol. 2000 Jun 1;151(11):1091-102
  7. Bräuner EV, Is there any interaction between domestic radon exposure and air pollution from traffic in relation to childhood leukemia risk? Cancer Causes Control. 2010 Nov;21(11):1961-4. Epub 2010 Jul 6
  8. Consumer's Guide to Radon Reduction, EPA

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