Radon protection
Under radon protection refers to measures the concentration of radon to reduce in buildings.
The chemical element radon is a natural, very heavy and radioactive noble gas that is created during the spontaneous radioactive decay of uranium . As a result, radon enters the soil air in areas with uranium ore deposits. The concentrations are different. In addition to the sources, the air permeability of the subsurface also plays a decisive role. For this reason, the radon pollution in an area can fluctuate considerably locally, so that conclusions cannot be drawn directly from the overview maps about the pollution of a property.
Occurrence and effects of radon
Radon can penetrate into rooms in contact with the ground primarily through joints and leaks. Depending on the amount of radon entering and depending on the air exchange, the indoor air can be significantly polluted. Radon dosimeters (filtering off the decay products and evaluating the energy of the alpha particles ) or time-resolved measuring devices are used to determine the radon concentration in a room . Because the radon concentration is subject to large fluctuations over time, measurements over a period of less than a month have little informative value. Measurements over a period of three months to one year are recommended.
The Radiation Protection Commission of the Federal Environment Ministry reported in a report dated May 12, 2005, in which all existing health studies on radon were evaluated, that in the "range from 100 to 200 Bq / m³ there is a statistically significant increase in the lung cancer rate from radon". The World Health Organization ( WHO) sets the critical level of harmful effects of radon at 100 Bq / m³.
A study by the Swiss Tropical and Public Health Institute (Swiss TPH) as part of the Swiss National Cohort Study shows that radon in living areas also increases the risk of developing malignant skin cancer ( malignant melanoma ).
Situation in Germany
In Germany that is radon exposure relatively well studied. The concentration of 100 Bq / m³ in buildings is only exceeded in a few regions. These include, for example, the Ore Mountains , the Thuringian Forest , the Bavarian Forest , the Eifel , the Black Forest , the Fichtel Mountains , the Harz Mountains and parts of the Alpine foothills .
Situation in Switzerland
In Switzerland radon exposure has been well studied in buildings. All measurement campaigns by the Federal Office of Public Health and the cantons have been completed. However, the database is constantly being expanded in that the measuring points recognized by the BAG (private laboratories) record their measurements in a central database.
Switzerland is one of the countries most affected by radon. The areas with the highest radon levels are in the cantons of Ticino , Uri , in regions of Graubünden and in the Neuchâtel Jura. Individual buildings with over 1000 Bq / m³ can be found in these areas. In almost the entire area of Switzerland, without radon protection in buildings, values of over 300 Bq / m³ must be expected (medium to high pollution).
Until the end of 2017, a legal limit of 1000 Bq / m³ and a target value of 400 Bq / m³ for new buildings and renovations (Radiation Protection Ordinance) applied in Switzerland. However, the building standard SIA 180 "Thermal insulation, moisture protection and indoor climate in buildings", version 2014 (SIA standards are recognized rules of technology in Switzerland ), requires the following:
- The radon concentration should be as low as possible, but certainly below 300 Bq / m 3 ;
- Walls of living spaces in contact with the ground must be radon-tight;
- Radon prevention measures must be taken into account when planning new buildings.
The Radiation Protection Ordinance will introduce a reference value of 300 Bq / m 3 from January 1, 2018 , which will replace the previous limit values.
Protective measures
Air purification
Noble gases are chemically inert , they hardly react with other elements . That makes it practically impossible to filter or sorb radon from the air . On the other hand, the radioactive by-products are also particles, some of which, however, are too small to be effectively captured by a commercially available air cleaner with HEPA and activated carbon filters . Only when the radioactive particles bind to other aerosols was it possible to determine a reduction in the indoor air pollution with radioactive dusts. A significant reduction in the exposure to radon and its secondary products can not be achieved by filtering room air .
seal
In new buildings, the radon protection is usually implemented with a radon-tight design of the floor slab and walls in contact with the ground in the form of a white or black tub . It is important to ensure a good seal, especially when pipelines (water, sewage, electricity, geothermal probes, district heating, fiber optics) are passed through. Subsequent sealing of existing buildings leads in the best case to a moderate reduction in radon concentration.
The first "radon-tight" cellars in Germany were built as a pilot project in 1993 in the Erzgebirge as prefabricated cellars .
Controlled removal of radon
With drainage pipes (holes pointing downwards) around or under a building, radon can be collected and usually carried away with a fan. Radon can also be ventilated out of basements and hollow floors with a fan. However, it must be ensured that sufficient outside air can flow in - if this ventilation creates a negative pressure in the room, this will increasingly suck in floor air containing radon.
With a high level of air permeability of the entire subsurface, there is the possibility of selective suction, a so-called "radon well". These are shafts filled with rubble, from which soil air is sucked in via a pipe with a fan and discharged into the open air. With such a well, several buildings can be greatly relieved of radon under favorable conditions.
Ventilate buildings with positive pressure
As a rule, a few pascals of excess pressure are enough to keep a building almost radon-free. This can be achieved with a separate fan that feeds air into the room or with a ventilation system. With the ventilation system, it must be ensured that the exhaust air volume is slightly smaller than the supply air volume in every operating state.
Other sources of radioactivity, building material radioactivity
The average radium content of building materials, binders and other additives is listed in an expert report by the Federal Office for Radiation Protection. The activity of the corresponding building materials is calculated according to the Leningrad empirical formula.
See also
literature
- Live healthier, but how? Practical tips for everyday life. Ed. Federal Office for Radiation Protection Salzgitter [u. a.] 2006. pp. 36-39.
- Radon, the invisible danger. In: Stiftung Warentest 2007, issue 10.
Web links
- Radon. An inert gas pollutes living. Federal Ministry for the Environment, Nature Conservation and Nuclear Safety
- Radon remediation measures for existing buildings (Switzerland, Baden-Württemberg, Bavaria, Austria, South Tyrol)
Individual evidence
- ↑ Radon - a noble gas pollutes living p. 3. (PDF; 1.2 MB)
- ↑ Radon - a noble gas pollutes living , p. 5. (PDF; 1.2 MB)
- ^ Danielle Vienneau et al .: Effects of Radon and UV Exposure on Skin Cancer Mortality in Switzerland. In: Environmental Health Perspectives. June 2017, accessed October 8, 2017 .
- ↑ Helmholtz Center Munich, Local and Environmental Dosimetry: Radon
- ↑ Radon Atlas Germany (not freely accessible)
- ↑ Competence Center Radon of the Institute for Building Hygiene. Retrieved November 30, 2016 .
- ↑ SR 814.501 Radiation Protection Ordinance (StSV). Swiss Confederation, accessed on October 14, 2015 .
- ^ Y. Yasuoka, T. Ishikawa, S. Tokonami, H. Takahashi, A. Sorimachi: Radon mitigation using an air cleaner . In: Journal of Radioanalytical and Nuclear Chemistry . tape 279 , no. 3 , March 1, 2009, ISSN 0236-5731 , p. 885–891 , doi : 10.1007 / s10967-008-7379-0 ( springer.com [accessed October 19, 2017]).
- ↑ a b c Swiss Radon Manual. (No longer available online.) Federal Office of Public Health, 2000, archived from the original on September 2, 2016 ; accessed on October 30, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c Radon Handbook Germany. Federal Office for Radiation Protection, 2010, accessed on October 30, 2016 .
- ↑ Natural radionuclides in building materials . Documentation from the German Federal Office for Radiation Protection. July 2005.
- ^ Leningrad empirical formula
