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Radon is an international problem. With few exceptions, most countries have regions where homes have elevated levels of radon gas in indoor air. International and national cancer research agencies, radiological protection agencies, scientific committees, and the World Health Organization, of course, combine their effort to develop international standards and monitoring programs. It is vital that you and I know of the potential risks and that we are given the appropriate advice on what we can do about it.
One major natural source of radioactive radiation is radon (Rn). Radon is a naturally occurring colorless, odorless, tasteless and invisible gas, released as a by-product of the radioactive decay of radium, a highly radioactive metal found in most soils and rocks. Some of the gas seeps from the ground and diffuses into the air while some enters the ground water. Because it is heavier than air, it tends to linger close to the surface, and high levels can occur in mine shafts, caves, tunnels and buildings. The amount is measured in Becquerels per cubic meter of air (Bqm3, one Bq is one decay per second), named after the 1903 Nobel Prize winner for physics, Antoine Henri Becquerel.
No radon level is safe. The health risk is greatest, however, when the radon is abundant in the air. Its concentration depends largely on regional geological conditions. The health authorities of many countries have agreed that remedial actions should be taken when a radon concentration level, Action Level, of around 200Bqm3 is exceeded. The level does vary between countries, though. The US, for example, established an Action Level of 148Bqm3. When scientists tested work places, public buildings and private homes and applied this level, they concluded that most test sites were well below this established low-risk level. Occupations, such as mine workers and cave tour guides in areas with high radium content in the soil, however, are exposed to levels sometimes well above 1000Bqm3. Private homes are also like 'caves' in that respect. Some homes in certain regions in Europe and North America, especially homes with cellars, have shown excessive levels.
Tests in the US showed that nearly one in 15 homes has elevated radon levels. The figures for the UK are equally stunning: the National Radiological Protection board estimates that between 2.000 and 3,000 people die form radon-induced illnesses every year and up to 100,000 live in homes with elevated radon levels. In the UK, radon makes up about 48% of the radiation dose a person receives. Every region and every country has different levels, though.
Australia is blessed with one of the lowest levels in the world. According to a study conducted by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), radon contributes only 9% to the radiation dose a person receives. The average home has a level of approximately 11 Bqm3, well below the global average of 40 Bqm3. The study, however, also found that the levels vary greatly and that around 2,000 - 3,000 homes may be above the Action Level and in need of intervention measures.
The difference between levels in Australian homes and those of the US and Europe is probably because of different soil types and different construction methods of buildings. Cellars and basements, which aren't easily made gas proof, are common in the US and Europe. The Australian study also showed that multi-storey buildings have higher levels of radon. This again may explain the differences, as the majority of Australians live in single-story homes.
Usually a home has a slightly lower air pressure than the external air, thus drawing in air, including radon. The gas enters the house via cracks in concrete slabs, cracks and joints in cellar walls, cavities inside walls, gaps along water pipes and electric wires, and gaps in suspended floors and joints. Although rarely, some building materials themselves may be the source of radon: rock walls, decorative rock fireplaces, and foundations or concrete that contain natural materials.
The concentration also depends on the season. In winter the windows remain shut for long periods if not for most of the time and radon levels can, therefore, accumulate to high levels. Stairways or draughty rooms will distribute the gas to other rooms. Test have shown that during the quiet time of late at night and in the early morning, the concentration levels are highest - less air movement. Important is also the moisture content of the soil beneath your home. Wet soil impedes the movement of radon, whereas dry and porous soil lets the gas seep to the surface almost unhindered.
Radon in homes
How radon enters homes
Radon Gas
How radon enters your home
A - cracks and gaps in floors
B- cavities between brick walls
C - pores and cracks in walls
D - construction joints
E - along loose fitting pipes and wires
F - building material
G - water supply
The radon health risks to mine workers has been recognized by scientists for more than fifty years. After testing thousands of underground workers, a definite link between radon and lung cancer is now well established. A study of tourist caves in Australia and New Zealand found that a large percentage of tours may experience short-term and excessive radon concentrations levels. Not until twenty years ago, however, have scientists established that indoor air in certain regions may also contain sufficient radon to be a health hazard. Today, the World Health Organization and the health departments of most countries have declared radon a known human cancer-causing substance (carcinogen). But more importantly, we also know how to reduce or prevent the risk.
We all benefit from radioactivity when X-rays reveal hidden diseases, or let me be more positive, when X-rays show that everything is alright.
So what is all the fuss about? What can the gas do to me?
Radon breaks down relatively fast. In just under four days (half-life), half of it will have changed into radiation and into very fine metal products called daughters. The daughters, or progeny as they are also called, attach easily to dust particles and can enter the lungs while we breathe, or enter your body via the stomach when we ingest contaminated water. There the substance will break down again and produces further radiation and more daughters. It is the daughters that cause most damage, because they can lodge themselves deep into the fine airways of the lungs.
The radiation emitted by the decaying process of radon is called ionizing radiation. What is ionizing radiation? All the molecules in the cells of lung tissue are home to negatively charged electrons, which provide a balance to the positive center of the molecule. When the emitted energy from a radioactive substance strikes a molecule, one or more electrons may dislodge causing an electric imbalance. The molecule becomes positively charged, or in other words, it has become a positive ion. The reverse may become true when too many of the marauding electrons attach to a molecule, thus causing a negative charge, or a negative ion.
Cells in lung tissues, that contain such ions, may become damaged. The cells die or regenerate abnormally, resulting in scarring and thickening of lung tissue. Your lung can still function properly after the loss of many cells and with modified cells. As a matter of fact, radon radiation doesn't appear to result in short-term health effects such as breathing difficulties and coughing. In the extreme and over time, however, the repair process can become rather disorganized and the cells may become cancerous. The studies involving mine workers showed that serious symptoms generally don't become apparent for several years.
The risk of developing lung cancer at home depends on many factors: the time someone spends at home, the concentration level, the amount of radiation received (dose), age, health status, etc. After all the tests and studies that have been conducted so far, one risk factor is number one - tobacco smoke. Scientists believe that combining smoking with radon exposure increases the risk by ten to twenty times when compared to non-smokers. Inconclusive evidence also points to children as being a risk group.
Lung cancer is difficult to treat. Presently, surgery and chemotherapy are the preferred options. Prevention, however, has become the number one weapon in combating lung cancer. In addition to the stop smoking campaigns, countries with radon problems begin to inform their citizens about the health hazard. While searching for the presence of radon in the body is difficult if not impossible, radon testing in homes is easy and not expensive.
Health effects of radon exposure
The main source of radon that is of concern to our non-occupational life is the ground beneath our home, and to a lesser extent ground/well water and building materials made from natural earth and rock. Soil made up of granite rock, some volcanic rock, organic-rich shales, phosphate minerals or pitchblende is known to release radon.
The gas may dissolve into the ground water and may be released into the indoor air when the water is stirred or sprayed, as during taking a shower or washing dishes. The present knowledge is that radon may also cause negative health effects when you drink contaminated water. Because of the short life of radon, however, water is only be a problem when you have your own bore water or use a well. Town water is usually stored and treated before it goes onto the long journey into your home. This is generally enough to reduce the risk to negligible levels.
Radon in water contributes only a small amount towards concentration levels. Of more concern is the accumulation of radon gas in your home. Normally the gas disappears into thin air, so to speak. In the home, however, the gas can become trapped and increase to levels that may be hazardous.
