About Radon

• Radon - a cancer-causing, radioaktive gas
• How Radon enters a building
• Radon - a health risk
• Radon levels vary in time
• Everybody can be affected by high Radon levels
• How to reduce indoor levels
• Preventive measures for buildings under construction

Radon - a cancer-causing, radioaktive gas

We are all permanently exposed to natural radioactivity. This is the radioactive radiation which comes from space (cosmic radiation) and from the natural radioactive elements that can be found in our environment (terrestrial radiation). The human being is fully adapted to this natural level of radiation, so in most cases natural radioactivity doesn't pose a health risk.

This is completely different as far as the naturally occuring gas Radon is concerned. Radon is radioactive and it is continually produced from the natural decay of uranium that is found in nearly all soils. Some amounts of Radon gas are present everywhere in the soil, water and air. Particularly high Radon levels occur in regions where the soil or rock is rich in uranium. It can enter the indoor air where it accumulates in poorly ventilated areas.

There are two main reasons, why Radon has become a health concern in our days:

• Currently, much emphasis is put on isolating buildings to save energy. Unfortunately, these sealings also reduce the exchange of indoor and outdoor air. Radon can therefore build up to high levels!
• In contrast to former generations, people nowadays spend roughly 80% of the lifetime indoors. The exposure time to indoor Radon has risen dramatically!

Out of these reasons Radon not only makes the largest contribution to the dose of natural radiation received by the human being (see picture on the top) but it even is considered the second leading cause for lung cancer after smoking. Approximately 5-15% of all lung cancer cases are due to high Radon levels!

How Radon enters a building

Because Radon is a gas, a fraction of the Radon produced in the soil can find its way into a building through cracks in the foundation, loose-fitting pipe penetrations, sump openings, crawl spaces, and the like..

During colder seasons when windows are closed and heaters are on the difference in temperature between the indoor air and the outdoor air causes a thermal stack effect. Warm air rises in a house and creates a vacuum in the lower portions of the building. This suction on the lower level, such as a basement, draws Radon gas from the soil into the building.

The concentration of Radon and Radon daughters in the indoor air depends on:

• the amount of uranium and radium in the soil
• cracks in the walls and foundation of the building
• loose-fitting pipe penetrations
• the impermeability between the different floors
• the existence of a concrete floor in the cellar

The concrete floor and walls in the basement slow down the movement of Radon from the soil into the building. However, cracks in the floor, wall slab joints, and openings around plumbing and electrical conduits allow Radon to enter a building.

Radon - a health risk

Radon levels in the outdoor air are relatively low however, when Radon enters a house it can build up to levels which pose a signifikant health risk to the occupants. Radon is known to cause cancer in humans and therefore it is ranked as a "Group A" carcinogen by the United States Environmental Protection Agency (EPA)!

When Radon undergoes the process of radioactive decay, new particles like Polonium (Po-218 & Po-214), radioactive Lead (Pb-214 & Pb-210) and Bismuth (Bi-214) are created. These Radon decay products are also called "Radon daughters" and unlike to the Radon gas they are solid particles. The problem is, that the Radon daughters are radioactive substances, too! Most of the Radon daughters become attached to tiny dust particles (aerosols) in the indoor air. When these particles are inhaled, a fraction of them is deposited in the lungs. Inside the lung, Radon daughters emit alpha particles that are absorbed in the nearby lung tissues. The resulting radiation dose increases the risk of lung cancer.

Radon gas is chemically unreactive. It does not react with body tissues. While some inhaled Radon does dissolve in the body fluids, the resulting concentration is so low that the radiation dose from the Radon gas itself is negligible. It is the Radon decay products that cause the damaging health effects when breathed in!

The greater the amount of Radon in the air, the greater is the potential of developing lung cancer, because:
More Radon means, that also more Radon daughters will be produced which can be inhaled and retained in the lungs. The radiation dose to the lung tissue increases and so does the risk of lung cancer. The mortality rate for lung cancer is about 90%!

NOTE: High Radon levels won't provoke any immediate symptoms like headache, fatigue or sickness.

Therefore, European health authoroties strongly recommend to keep indoor Radon levels below these limits:

For houses, built before 1996: 400 Bq/m³

For houses, built after 1996: 200 Bq/m³

The Council Directive 96/29 EURATOM of 13 May 1996 also adresses the subject of Radon levels at working places. This very directive must be adopted by national Radiation Protection Directives in each country of the EU.

Radon levels vary in time

Radon levels frequently show significant daily variations. Because Radon is a gas, changes in the atmospheric pressure also affect its emission from the ground and its accumulation in the building air. But it is also the habits of the occupants which contribute a lot to the variations in Radon concentrations. When doors and windows are opened during the day, Radon is diluted with fresh air and indoor Radon levels will decrease. On the other hand during the nighttime, if doors and windows are closed Radon levels can build up again.

The figure on the right shows daily variations of Radon levels over one week in a cellar of a house with very high Radon concentrations.

In addition to the daily variations, Radon levels in a building also show seasonal variations. In contrast to the summertime, indoor Radon concentrations are significantly higher during the winter months because:

• Due heating of the rooms, warm air ascends in the house and creates a state of negative pressure in the lowest floor. This thermal stack effect causes the suction of Radon gas from the soil into the building.
• The frozen ground makes it more difficult for the Radon gas to escape into the atmosphere. It will find an easier way for migration through the cellar of a house.
• Homes and working places are less aerated during the colder season.

The resulting seasonal change in indoor Radon concentrations is also called the "Radon wave" as shown in the figure on the right (Click on image to enlarge view).

Everybody can be affected by high Radon levels

Practical experiences frequently showed, that even neighbouring houses may have very different Radon levels. The reasons are:

• Varying composition of the soil below the houses
• Different methods of construction of the buildings
• Different habits (aeration habits) of the occupants

Due to these facts it is impossible to make any serious predictions for a single building concerning the radon level. Precise radon measurements are the only means to assure, that a home or working place is Radon safe.

Where is a good location for a Radon measurement

It is recommended that you test the rooms in your home, where you spend most of your time (sleeping room, living room...). As highest Radon levels can be expected in the basement, a measurement in this room is very significant for the Radon situation in your home.

How long should you test for Radon

Considering the fact that Radon levels vary significantly during the year, only long term measurements are advisable. We recommend to test the rooms in summertime as well as during the winter period. The Kodalpha Radon Dosimeters are intended for a measuring time of about three months, whereas the Ramon 2.2 Radon detector will deliver reliable results after two weeks.

How to reduce indoor Radon levels

Generally speaking, to avoid a state of low pressure inside the house, which may lead to the suction of Radon gas from the soil into the building.

The main reasons for low pressure inside a building are:

• windows which are opened at the lee side of the house
• mechanical exhaust devices in kitchens, bathrooms...
• drawing chimneys
• insufficient air supply to burners for oil, gas or wood

Indoor Radon can be reduced to safe levels by means of appropriate techniques which in many cases are simple and inexpensive to accomplish. Of course, the method for Radon reduction (also called: Radon mitigation) is dependent on the degree of Radon that was found through precise measurements.

By frequently aerating the rooms, indoor radon concentrations will be diluted or replaced by fresh air. But this method only leads to a momentary reduction of the Radon levels and care has to be taken to guarantee a sufficient exchange of the indoor air. In order to achieve a permanent reduction and to prevent a loss of energy during the cold seasons, other Radon mitigation methods are necessary.

Simple constructional Radon mitigation methods

The level of the indoor Radon concentration depends mainly upon the ease at which Radon can migrate into the house and move within the house as well as on the amount of suction force exerted by the building on the soil beneath.

A reduction of the Radon level can be achieved by:

• Sealing cracks and joints in the floor and walls which are in contact to the soil.
• Sealing of openings around plumbing and electrical conduits through which Radon can enter the building.
• Sealing of walls between occupied and unoccupied rooms.
• Sealing with concrete of exposed earthen floors in basement areas.

Radon remediation

Sealing is not a reliable reduction method when a building is affected by high Radon levels. Only professional Radon remediation taking into consideration also the constructional factors of the house will be applicable in such cases.

According to experience, such systems are based on the following concepts:

• Excellent results are achieved by means of ventilation systems which are connected to a heat exchanger. In this way indoor air is continually replaced by outdoor air which is very low in Radon. The heat exchanger keeps the loss of energy reasonably low. The efficiency of such a plant is shown on the figure on the right. Disadvantage: It isn't always possible to install such systems in finished houses.
• Low pressure in basement areas is compensated by the permanent supply of outdoor air with a fan. This avoids the suction of Radon and other soil gases into the house (thermal stack effect).
• Active Soil Depressurization mechanically creates a suction on the soil beneath the foundation. Through a tube, which is inserted in the basement floor Radon is vacuumed out of the soil and exhausted through the roof.

Any such systems have to be installed by professional contractors, who possess the necessary technical knowledge.

Preventive measures for builduings under construction

A prediction of precise radon levels which may occur in a future building is not possible. On the other hand the constructor can consult local authorities and gain information about the radon potential in the region. Radon measurements in neighbouring houses may also give information about radon levels, that can be expected.

Especially in areas with a known high Radon potential it is recommended to consider a Radon mitigation system at the planning of a new house. This will be the best way for a reliable Radon reduction, technical wise as well as from the financial point of view.

A very good mitigation method is a drainage system which permanently removes Radon gas from the soil beneath the building's foundation. The drainage tubes can be connected to a fan if necessary or simply left open if enough Radon is removed through natural airflows.