Radon is believed to cause an increased risk of lung cancer and it is therefore of interest to identify houses with high levels of indoor radon. It is important to know how many houses that have high levels and the location of these houses. Furthermore, it is of interest to know about low-radon houses where there is no cause for alarm.
Radon and childhood cancer (June 2008)
To read about the new study about radon and childhood cancer, please go to the Danish version of this page (click on the Danish flag).
In Danish: Hvis du vil læse om den nye undersøgelse om radon og børnekræft, så skal du skifte til den danske udgave af denne side (klik på Dannebrog). |
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National survey of radon
A survey of radon in Danish dwellings has been carried out by Risø National
Laboratory, National Institute of Radiation Hygiene (SIS), and the Geological Survey of Denmark and Greenland (GEUS). The report (published in 2001) is in Danish, but includes a 10-page summary in English.
Summary
The concentration of radon-222 has been measured in 3019 single-family houses and 101 multi-family houses (apartments) with the so-called alpha-track technique (CR-39). On this basis, a map has been created which shows the percentage of single-family houses in each of the 275 municipalities with levels above 200 Bq/m3, i.e. the action level recommended by the Danish building authorities for simple radon remediation.
Key statistics
The average radon level (arithmetic mean) is 77 Bq/m3 for single-family houses and 18 Bq/m3 for multi-family houses. For Denmark as a whole, 4.6% of the single-family houses are above 200 Bq/m3. This corresponds to 65000 houses. In certain parts of the country, e.g. northern Jutland, less than 1% are above 200 Bq/m3. In other places, e.g. certain parts of Funen and Bornholm, the value is above 10%.
Factors
The relation between radon and various factors has been investigated with regression analysis. The three most important factors are type of basement, province and soil type. The analysis confirms that the soil below the houses is the most important source of radon in Danish single-family houses.
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Reduction of indoor radon
Studies in many countries have shown that the best way to prevent radon entry from the soil is to use a so-called sub-slab ventilation system. A fan draws air from below the slab. This creates a flow of air from the house towards the soil. The graph shows the effectiveness of such a system as tested in the so-called Radon-95 project.
The indoor radon concentrations decreases when the fan is switched on. Before remediation, the house had an annual average radon concentration of about 1000 Bq/m3. After remediation the level was about 50 Bq/m3.
The Danish Environmental Assessment Institute has carried out a cost-benefit analysis of radon reduction in Danish houses. |
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Laboratory techniques
We conduct measurements of radon-222 in soil, water and building materials as described in the document:
Radon-222 in soil, water and building materials: Presentation of laboratory measurement methods in use at Risø (pdf)
Radon in houses and the risk of childhood cancer
In 2001, an epidemiological study was initiated to investigate if radon in houses is a significant cause of childhood cancer. Denmark has about 150 such cases every year, and the main cause is unknown. The study is partly motivated by results from the abovementioned radon survey that showed that there is a considerable variability in radon levels from house to house, and that a significant part of this variability can be explained by factors relating to house construction and geology. The epidemiological study uses a database from the Danish Cancer Register with 2400 leukemia and other cancers diagnosed from 1968 to 1994 among Danish children. Included in the study are also about 6700 matched control children. The main task for Risø is to assign radon concentrations to 23000 addresses where the children lived from conception to diagnosis on the basis of the available house and soil information obtained from the Building and Dwelling Register and GEUS. A statistical prediction model is under development for the purpose. The model will be tested against 700 (independent) addresses with known radon concentrations. The project is lead by the Danish Cancer Society, and other participants are: the National Institute of Radiation Hygiene, the National Survey and Cadastre (KMS), and GEUS. The project is financed by the Danish Research Centre for Environmental Health (ISMF).
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Radon as a tracer for soil-gas entry into houses on contaminated soil
Radon can be used as a tracer for soil-gas entry into houses located on contaminated soil. This is possible because the concentration of radon in the soil is typically 1000-10000 times higher than the concentration in outdoor air. In a study from 2001 we demonstrate the technique for a house located next to a contaminated dry-cleaning property. During the investigation, vacuum extraction was used to remove chlorinated solvents (perchloroethylene, PCE) from the unsaturated zone. The study shows that the vacuum extraction influences the radon concentration in and below the house. Based on the measured radon concentration in the exhaust air from the vacuum system and a typical radon emanation rate for Danish soil, it is estimated that the soil vapor extraction system ventilates about 10000 m3 of soil. |
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Publications
PowerPoint presentations
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