What is Radon Gas?
Radon is a colorless, odorless and tasteless gas that occurs naturally in almost all soils and enters into homes even through solid concrete walls.
Radon has come to world's wide attention as a very significant contaminant for indoor air quality and it has been estimated that long-term exposure to radon gas is the second most frequent cause lung cancer after smoking.
Since radon gas is invisible, without odour, and without taste one can only detect radon gas using special detection kits. The concentration of radon gas is not measured directly but rather by the radioactivity radon gas produces. In US radon's radiactivity is measured in picoCuries per liter of air (pCi/L) where a picoCurie is a trillionth part of a Curie, the unit of radioactivity equivalent to 1 gram of radium. In other contries using the metric system, radon's radiactivity is measured in Becquerels per cubic meter (Bq/m3) and one becquerel corresponds to the transformation (disintegration) of one atomic nucleus per second. To transform from one unit to the other use this formula: 1 pCi/L = 37 Bq/m3
Becquerel per liter (Bq/L) is used for measuring radon gas concentrations in water.
Why Care About Radon Gases?
It has been estimated that more 21,000 people die from radon induced lung cancer, in US alone. Radon gas is an invisible health risk for you and your family!
Here is Eddie's story about radon gas exposure:
The main danger from indoor radon gas exposure is an increased risk of lung cancer. The World Health Organization estimates that the risk of lung cancer increases by 16% for each additional 100Bq/m3 (~3 pCi/l) increase in radon gas levels.
Once in the air, radon gas starts to disintegrate. The products of radon gas disintegration (radon daughters or radon progeny) usualy become electrically charged and can attach to various particles from the air we breathe. Once in the lungs the progeny will continue to decay by emitting alpha particles which can damage the DNA of cells and creating the basis for a potential cancer.
How Radon Gases Enter Your Home
In modern houses, airtight to be energy efficient, radon can get trapped and accumulate more easily than in older homes to levels far above of those found in outdoor air.
Radon gas can enter in your home from the soil through construction joints, tiny cracks or pores in hollow-block walls, floor drains, sump pumps, cracks in concrete floors and walls. Radon levels are generally highest in basements and ground floor rooms that are in contact with the soil, except when you have a forced air heating and/or air conditioning systems found to move farely quickly radon gas on all levels of the home. Another source of radon indoors may be the gases released by well water during showering and other household activities.
Since it is a single-atom gas, radon gas can penetrate many common materials like leather, low density plastic, paper, most paints, and building materials like wood paneling, concrete block, mortar, gypsum board, tar paper, and most insulations.
Here is a list of potential radon entry ways into your home:
- Floor-wall joints
- Mortar joints
- Cracks in concrete slabs
- Pores and cracks in concrete blocks
- Exposed soil, as found in a sump
- Drain tiles, if drained to an open sump
- Loose fitting pipe penetrations
- Open tops of block walls
- Building materials such as granite coutertops and some rocks
- Water from radon contaminated wells
A Bit Of Science - Radon Gases Decay
Radon gas is a chemical element with the symbol Rn and atomic number 86.
Radon originates from Uranium 238, a radioactive element. Almost anywhere in the world you can find some radioactive Uranium 238 in the soil. Radioactive means that the element or atom occasionally loses part of itself and changes into a different element. During this radioactive decay the element releases energy and causes varying amounts of damage to whatever surrounds it. The average amount of time it takes before half of the element has decayed or changed is know as the elements half life. Uranium 238 has a 4.5 billion year half life. See the half lives listed below. The next element, Thorium 234 has only 24 days before half of it is gone.
The following is the decay series from Uranium 238 to Radium 226 (all are solid particles).
| Element | Half life |
|---|---|
| Uranium 238 | 4.5 billion years |
| Thorium 234 | 24 days |
| Protactinium 234 | 1 minute |
| Uranium 234 | 250,000 yrs |
| Thorium 230 | 80,000 yrs |
| Radium 226 | 1,620 yrs |
The next element after Radium 226 is RADON. See the decay series listed below. Radon is the only noble gas in the final decay chain. Noble gases have no charge (non-reactive) which means radon can freely move through the soil. Radon’s half life is about 4 days, which is just enough time to float through the soil, get into our homes and decay into a series of short lived charged particles that can get inhaled in the lungs and damage the DNA of lung cells.
| Element | Half life |
|---|---|
| Radon 222 | 3.8 days |
| Polonium 218 | 3 minutes |
| Lead 214 | 27 minutes |
| Bismuth 214 | 19 minutes |
| Polonium 214 | 0.0016 seconds |
| Lead 210 | 22 years |
| Bismuth 210 | 5 days |
| Polonium 21 | 128 days |
| Lead 206 | Stable |
Facts About Radon Gases
- Radon is a colorless, odorless and tasteless gas that occurs naturally in almost all soils and may be found in any home
- The estimated average of natural outdoor level of radon gas across US is 0.4 piC/L
- Radon is the heaviest known gas, 9 times denser than the air.
- Since it is a single-atom gas, radon gas can penetrate many common materials and building materials
- Radon gas finds its way through fractured bedrock closer to your home foundation and then through the foundation cracks and windows seams into your basement
- Radon gas is an invisible health risk for you and your family
- Radon gas can only be detected with special detection kits
- More 21,000 people die from radon induced lung cancer, in USA alone
- Radon gas gets moved to all levels of your home quite rapidly by the forced air central air conditioning system
- Another pathway for getting radon gas into your home and subsequently into your lungs is from water
- Once in the air radon gas starts to disintegrate
- The products of radon gas disintegration (radon daughters or radon progeny) can can attach to various particles from the air we breathe
- Once in the lungs the radon gas progeny continue to decay by emitting alpha particles which can damage the DNA of cells
- Radon gas levels in a house can differ dramatically from the radon levels in the next house
- Low reading of radon levels in your neighbor’s home is not good enough assurance for you and your family
- It took a long time to establish the cause of the sickness killing the miners as radiation from radon gas decay
- Geological surveys concerning the level of radon gas and radioactivity are available in some countries
- Very good books about radon gas, some of them for controversy lovers, are available
Radon's Effects on Health
The history of radon's effects on health goes back in time hundreds of years to the mountain sickenss affecting miners. However, it took a long time to establish the cause of the sickness killing the miners as radiation from radon gas decay.
It was only in early early 1980s when scientists and officials become aware of the influence radon gas on indoor air quality and the trigger was Stanley Watras, an employee at the Limerick nuclear power plant who set off the radiation alarms on his way to work in 1984. After searched his house it was found that the radon levels in his basement were about 2,700 pCi/L and it was estimated that the risk of living there was equal to that of smoking 135 packs of cigarettes a day.
Epidemiological Studies on Radon Gas
Extensive epidemiological studies of thousands of underground miners, carried out over more than fifty (50) years world-wide, in metal, fluorspar, shale, and uranium mines in the United States, Canada, Australia, China, and Europe. These studies have consistently shown an increase in lung cancer occurrence with exposure to radon decay products, despite differences in study populations and methodologies.
The most interesting findings of these studies are (1) at equal cumulative exposures, low exposures in the range of EPA's 4 pCi/L action level over longer periods produced greater lung cancer risk than high exposures over short periods, (2) Increased lung cancer risk has been observed in miners at relatively low cumulative exposures in the range of EPA's 4 pCi/L action level (Sevc Kunz, Tomasik et al, Health Physics 54(1):27-46,1988; Mulles Wheeler et al, Proceedings of International Conference on Occupation Radiation Safety in Mining, Vol. 1, Canadian Nuclear Association; Radford and St. Clair Renard, New England Journal of Medicine310(23):1485-1494, 1984;Woodward, Roder et al, "Cancer Causes and Control" 2:213-220, 1991) and (3) nonsmoking miners exposed to radon have been observed to have an increased risk of lung cancer.
The most complete epidemiological study linking long term exposure to radon gas within homes and lung cancer was published by the University of Iowa in 2000. This 5-year study shows that the exposure of adult women to radon over 15 years at the "action limit" radon level of 4 pCi/L increases the lung cancer risk by 50 percent over exposure to the natural levels. The study also proves that even long-term exposure to low levels of radon causes lung cancer and the risk is directly proportional to the radon level.
Radon Maps
Radiation and Nuclear Safety Authorities, Radiation Protection Institutes, Health Protection Agencies, National Radiation Laboratories and Environmental Protection Agencies around the World are concerned with the risks of indoor radon pollution and outdoor level of radiation.
Here are some available geological surveys concerning the level of radon gas and radioactivity in their respective countries.
- Radon Map of United States
- Radioactivity Maps of Canada
- Radon Map of United Kingdom
- Radon Map of Denmark
- Radon Map of Germany
- Radioactivity Map of Ireland
Official Limits of Radon Levels
Most countries in the world have standards and guidelines for the acceptable level of radon concentration in indoor air. It is generally accepted that a radon gas level of 4 pCi/L or 148 Bq/m3 is a clear indication that action must be taken to mitigate the levels of radon within homes. Since the risks are high, especially for children, some will rightfully argue that no ammount of radon gas is safe. In fact, the Environment Protection Agency estimated that exposure to radon gas levels of 4 pCi/L is equivalent to getting a daily chest x-ray or smoking 10 cigarettes each day.
Radon Act 51 passed by US Congress in the 1980s sets the target radon level for indoor radon levels to 0.4 pCi/L, which is the estimated average of natural outdoor level of radon gas across USA and shortly after, the Environment Protection Agency was given the task of developing practical guidelines around radon gas mitigation.
After estimating the average cost of radon mitigation for a home at around $1200 to $2500, EPA came up with the following recommendations:
- "action limit" of 4 pCi/L - fix your home
- "consider action limit" of 2 pCi/L - consider fixing your home
The "action limit" does not imply safety, it was merely the result of a macroeconomic cost/benefit analysis for the US population at large in 1980. Since then it has been estimated that the cancer risk from radon at the "action limit" is about 1,000-times higher than the safety limits allowed for suspected carcinogens and toxins in food or drinking water.
More recently, the World Health Organization's (WHO) "Handbook on Indoor Radon: A Public Health Perspective" indicates that radon exposure is a major and growing public health threat in homes and recommends that countries adopt reference levels of the gas of 100 Bq/m3, equivalent to 2.7 pCi/L. The handbook published in 2009 was a key deliverable of WHO's International Radon Project launched in 2005, focuses on residential radon exposure from a public health point of view, and provides recommendations on reducing health risks from radon by preventing and mitigating radon exposure.
Dr. Maria Neira, Director of WHO's Public Health and Environment Department asserts that "Radon is the second most important cause of lung cancer after smoking in many countries" and "Most of radon-induced lung cancers occur from low and medium dose exposures in people's homes. Strengthened action by policy makers, and by construction and building professionals can substantially lower the health impact by preventing and reducing radon exposure."
The President's Cancer Panel issued its "Reducing Environmental Cancer Risk: What We Can Do Now" in 2010, points out the new radon risk data emerged since the existing "action level" of 4 pCi/L was set and encourages the EPA to consider lowering its current "action level" for radon exposure.
Books About Radon Gases
Here are some very good books about radon gas, some of them for controversy lovers …