The radon is higher in vacant houses
The health effects of radon in residential buildings
Radon is a natural radioactive noble gas, which arises during the spontaneous radioactive decay in the soil of uranium 238 via thorium, protactinium, uranium 234, thorium and radium 226 [2, p.72] and escapes into the air. It can occur practically everywhere in different concentrations , but also in mineral building materials. The radon concentration in buildings can arise from different sources, mainly from the natural radon outgassing of the soil. [2, p. 71] [5, p. 158].
Radon in the residential building
The concentration is always slightly higher inside the house than outside, where it is between 8 and 23 Bq / m3 Air and the values increase from north to south. 
On average, the radioactivity in the home is 15% higher than in the open air. Especially when a lot of pumice stone, chemical gypsum, slag and / or granite were used for the walls or ceilings [3, p.12]. In studies of almost 6000 apartments in 1984, 40 Bq / m were found in 50% of the living spaces3, in 10% higher 80 Bq / m3, 1% more than 220 Bq / m3 and in 10 apartments more than 500 Bq / m3 measured. At that time, the International Commission on Radiation Protection recommended limit values for indoor air for old buildings with 200 and for new buildings with 100 Bq / m3 as admissible.
In 1991 the Bavarian Ministry of the Environment carried out an investigation in Neunburg vorm Wald in Upper Palatinate in winter, when there is less ventilation than in summer, with average values of 415 Bq / m3 in 50% of the examined apartments. The values were particularly high in older buildings with the building materials, wood, clay and natural stone with "natural" cellar floors. 
Radon health effects
The study by the Karolinska Institute in Stockholm on radon and lung cancer included 4,200 people, 1,350 of whom had lung cancer. Radon concentrations were measured in 9000 current and former homes. The result was based on the activity of radon with 50 Bq / m3 at 140 to 400 Bq / m3 a cancer rate around 1.3 times and over 500 Bq / m3 found to be 1.8 times. 
The Federal Office for Radiation Protection (BfS) was involved in a Europe-wide epidemiological study on lung cancer and radon in common rooms, funded by the European Commission and published in 2005. "Radon causes around 20,000 lung cancer deaths annually (corresponds to around 9% of all lung cancer cases, analogous statement also in Focus) in the European Union, of which around 3,000 are in Germany.
It has been observed that people living in rooms with radon concentrations between 100 and 200 Bq / m3 People who live in room air have a 20 percent higher risk of lung cancer than people who live in rooms with values below 100 Bq / m3 Life. This means that there is a statistically significant increased risk of lung cancer even below radon concentrations of 200 Bq / m3 before. "
The average indoor pollution is around 50 Bq / m3, of which about 3/4 comes from the building materials used.  Strongly increased radon concentrations in common rooms depend on the geological conditions (building ground) and on other factors (tightness of the foundation or foundation slab, basement, ventilation habits and so on.). It can only be reliably determined by measurement.
Even with simple measures such as wall sealing or additional ventilation, the radon concentration in common rooms can be reduced considerably. 
Higher radon concentration through thermal insulation
In Sweden, an increase in the dose from 110 mrem to 380 mrem was found in highly insulated dwellings. (All radioactive radiation - whether natural or artificial - is hostile to life. [Prof. Fritz-Niggli] Therefore, an air change of 2 to 3 is recommended [3 p. 17] Especially in poorly ventilated rooms, such as during holidays or vacant houses with closed doors and windows, the radioactivity increases rapidly and reaches high levels.  This article is about how indoor air pollution by radon gases is measured and what first measures you can take yourself.
Selected building materials are listed in Table 1. There is a wide range of fluctuations, with sand, limestone and natural gypsum containing smaller amounts of radioactive substances. But the location is also decisive, for example on the heather soils of the Lechfeld south of Augsburg 3-12 μR / hour or in the Fichtelgebirge, Bad Berneck 15.8-18.9 μR / hour or on the clay soils northwest of Dachau 13, 4-22.7 μR / hour measured.
Table 1: Natural radioactive substances in building materials [Nanocurie / kg] [3 pages 9-10]
|Construction sand, construction gravel||0,1-1,1||0,1-0,8|
As far as we know today, radon is the second most common cause of lung cancer after smoking and by far the most significant single environmental factor influencing human health. [1, 4] The combined effects of radon and smoking are particularly dangerous. [1, 2] The tobacco plants accumulate in addition to the other cancer toxins, radium, radon and their decay products.
The health effects of radon are described as follows. In the case of radioactive decay (half-life 3.82 days), a number of other short-lived, radioactive substances are created one after the other, which get into the air. The alpha particle (helium atomic nucleus) is emitted by radon, which is not very energetic, but has the largest cross-section of all radioactive decay products.
Outside of the human body there is hardly any risk. But in the lungs, radon and its short-lived decay products, such as the radioactive isotopes polonium, bismuth and lead, contribute to general radiation exposure.  In the air, the heavy metals accumulate on the walls or furniture as well as on the fine dust particles (aerosols) (85-90%) floating in the air. The remaining 10% form the free portion. Radon, the free and aerosol-bound heavy metals, are deposited differently in the lungs when inhaled.  Determining the radiation dose is very complicated due to the consideration of the individual factors that extend up to the length of stay or meteorological data acquisition.
Medicinal baths and mineral water with radon (medicinal water from deep wells is already 37,000 Bq per liter) are used to stimulate the body's defenses, so they are not harmful, but are used for medical treatment. Much more depends on the dose and the long-term exposure. A hobby room in the basement is therefore not a problem.
The ability to influence the lowest possible radon pollution in new buildings by selecting suitable properties is limited by the real estate market. With dense concrete slab foundations and no lounges or even living rooms in the basement or basement, countermeasures or precautions can be taken. This is already more difficult in existing buildings. But the simplest method is sufficient and regular ventilation.
The thermal insulation ordinance 95 still allowed an air change of 0.8 per hour, in the sense of energy saving in the EnEV, the air change rates vary between 0.45 and 0.6 / hour. In specialist lectures, air change rates of 0.2 to 0.3 / hour were even achieved suggested. 
If one looks at the values determined in the above-mentioned studies, it is very easy to deduce that with each reduction in the air exchange, the permanent radon concentration also increases and thus also leads to a higher risk of lung cancer. How big the increase can be is shown in the above-mentioned study by the Bavarian Ministry of the Environment. However, it should also be mentioned that with the ever decreasing prescribed ventilation rate, the spore load of molds or other germs, dust and chemical substances or mixtures of substances in living spaces increases, which, depending on the type and their interaction as a mixture of substances, also cause health consequences can.
Sufficient and regular ventilation in order to reduce the radon and other pollutant concentrations and thus maintain a very low risk is prevented by the stipulations in the Energy Saving Ordinance.
A recommendable contribution to radiation and nuclear energy from Dr. Böttiger.
Chemical & physical properties:
Element symbol: Rn
Element name: Radon
Occurrence: in the air
Group membership: VIII - noble gases
Atomic number: 86
Atomic mass: 222.0176
Boiling temperature: 211 K / -62 ° C
Melting temperature: 202 K / -71 ° C
Density at 1013 mbar: 9.23 g / l
Covalent atomic radius: 222 pm
Ion radius: ---
First ionization energy: 10.75 eV
Electron configuration: [Xe] 4f145d106s26p6
Oxidation number: 2
Number of valence electrons: 8
Number of bowls: 6
Physical state: gaseous
Type of decay: α
 Anja Schröder; Radon is the second most common cause of lung cancer, Informationsdienst Wissenschaft from April 2nd, 2005 https://idw-online.de/pages/de/news99103
 Diel, Friedhelm; Interior pollution, recognize, evaluate, renovate, contribution by the ecological research institute, Bauverlag Wiesbaden 1993, p. 71ff
 Institute for Building Biology, Healthy Living 1980, pp. 3,9-10,12,17
 Daunderer, Max; Poisons in everyday life, 1st edition, C.H. Beck`sche Reihe 1999, pp. 158-160, 168
 Schwankner, Robert J .; arcus 1986, issue 6
 Federal Health Gazette 29, No. 3, March 1986
 Rauch, Peter; The ventilation exchange in a building www.ib-rauch.de/Beratung/luften.html
Links to supplement
Radiation and radiation protection
- Information page about lung cancer from www.fid-gesundheitswissen.de
- www.ssk.de Radiation Protection Commission
- Radiation medicine Onmeda.de detailed information on various topics
- On the trail of the mechanisms of radiation effects 12.2004
- Management of radiation accidents: nuclear medicine in a worldwide network 12.2004
- Radioactive radiation
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