Radon and its invisible risks for health

What is radon?

Odourless, colourless and tateless, radon is a naturally occurring gas that arises from the decay of uranium. It is radioactive, and can be naturally found in rocks, soil and water, as well as in the air. When radon is in the air, it decays; this process produces radioactive particles.

As we inhale, these radon particles enter our system, where they can be deposited on the cells that line our airways. In large quantities, radon can damage our DNA and even cause lung cancer. However, this is not a cause for alarm in general. Although radon is commonly found outdoors, it is in such low concentrations that it does not cause any problems. Issues arise when radon is found indoors, where it does not dilute as effectively as it does outside. The highest radon levels can be found in locations where uranium is also present. It is often found in caves and mines, as well as in treatment facilities for water. However, radon has also been found in homes, offices and schools in ranges which could potentially cause problems: from 10 Bq/m3 to more than 10,000 Bq/m3.

What does radon do to our health?

A strong link has been found between radon and lung cancer (although no other forms of cancer have been linked to the gas). Of course, smoking is the most common cause of lung cancer. However, radon is the second most common cause, and scientists believe that it causes between 3 and 14% of all cases of lung cancer in a country.

The effect of radon on our lungs is most often seen in those who work in uranium mines. Uranium miners, who are exposed to higher concentrations of the gas than most people, have been seen to suffer lung cancer as a result. However, the effect has also been seen on people who are exposed to even a low level of radon. The results of studies, which have been carried out in various regions, are striking: the risk of lung cancer has been seen to increase by 16% per 100 Bq/m3 increase in the long term, average radon concentration. As radon exposure increases, the risk of lung cancer also shows a proportional increase.

Those most at risk from the effects of radon are smokers. Studies have shown that smokers are an estimated 25 times more likely to suffer lung cancer from radon exposure than non-smokers.

Why is there radon in our homes?

For people who don't work in a radon-heavy environment, exposure to radon is most likely to occur at home. A number of factors can affect the concentration of radon in a dwelling place. These include:

• the levels of uranium in the rocks and soil under the building
• the ease with which radon can travel from the soil into the building
• the ease with which air outside can enter. This depends on a number of things, including how the home was constructed, how airtight it is, and how the inhabitants choose to ventilate it.

Because radon enters buildings through the soil, radon levels are generally higher in subterranean sections of a building, such as basements or cellars. However, the gas can ultimately enter all parts of a building, through cracks in the floor, gaps surrounding pipes or cables, holes and small pores in wall, and drains. Even two adjacent homes can record quite different radon levels, and over the course of a day the level of radon in a home can show significant fluctuations. For this reason, measurements are carried out for a period of at least three months before anything definite can be established about the levels of radon in a particular building.

How can radon be reduced in homes?

Fortunately, there are a number of methods in place for reducing radon in existing buildings, as well as preventing the spread of radon in new developments. Due to its harmful effect on human health, the presence of radon in soil should be taken into account when new building developments are taking place. Indeed, in many countries there are now mandatory measures in place to ensure that new developments are built with radon reduction strategies in mind.

Some of the methods that have shown to effectively reduce radon include:

• increasing ventilation under the floors of buildings
• the installation of a radon sump system, which goes in the basement or under a solid floor
• improving sealing on floors and walls, to prevent radon from leaving the basement and entering the rest of the house
• improving the home's ventilation system

In severe cases, radon ventilation fans can be added, too. However, even without fans, these methods for lowering radon levels have reduced presence of the gas by more than 50%.

Can radon be found in drinking water?

Due to its presence underground, radon is more likely to be found in water sources like springs and wells. Surface water - rivers, lakes and reservoirs - have lower levels of radon. However, even in countries in which the majority of water comes from groundwater sources, which contain radon, there has been no link proven between its consumption and stomach cancer.

The risk of radon in water comes from the fact that, when it dissolves in drinking water, it is released into indoor air, and therefore results in a higher radon dose. As a result, the WHO has set guidelines for quality of drinking water, which include screening drinking water for levels of radon. Fortunately, it is easy to lower the concentration of radon in drinking water supplies, through the use of either aeration or granular activated carbon filters.

What does the WHO say about radon?

The WHO has published a series of documents outlining policy options for reducing radon exposure. It recommends that countries establish an annual national average concentration of reference level of 100 Bq/m3. If this is impossible due to the particular circumstances in the country, it recommends that radon does not exceed 300 Bq/m3. Furthermore, it recommends that building codes include guidelines on radon prevention, and that radon measurement protocols are put in place.