Editing Radon (section)

===Accumulation in buildings===
Measurement of radon levels in the first decades of its discovery was mainly done to determine the presence of radium and uranium in geological surveys. In 1956, most likely the first indoor survey of radon decay products was performed in Sweden,<ref>{{Cite thesis |last=Bengt |first=Hultqvist |title=Studies on naturally occurring ionizing radiations with special reference to radiation doses in swedish houses of various types |date=1956 |publisher=Stockholm College |page=125}}</ref> with the intent of estimating the public exposure to radon and its decay products. From 1975 up until 1984, small studies in Sweden, Austria, the United States and Norway aimed to measure radon indoors and in metropolitan areas.<ref name="George-2008" />
[[File:Radon Lognormal distribution.gif|thumb|upright=1.75|Typical [[Log-normal distribution|log-normal]] radon distribution in dwellings]]
[[File:US homes over recommended radon levels.gif|thumb|upright=1.35|Predicted fraction of U.S. homes having concentrations of radon exceeding the EPA's recommended action level of 4&nbsp;pCi/L]]

High concentrations of radon in homes were discovered by chance in 1984 after the stringent radiation testing conducted at the new [[Limerick Generating Station]] nuclear power plant in Montgomery County, Pennsylvania, United States revealed that [[Stanley Watras]], a construction engineer at the plant, was contaminated by radioactive substances even though the reactor had never been fueled and Watras had been decontaminated each evening. It was determined that radon levels in his home's basement were in excess of 100,000&nbsp;Bq/m<sup>3</sup> (2.7&nbsp;nCi/L); he was told that living in the home was the equivalent of smoking 135 packs of cigarettes a day, and he and his family had increased their risk of developing lung cancer by 13 or 14 percent.<ref name="lung">LaFavore, Michael. "Radon: The Quiet Killer." ''[[Funk & Wagnalls]] 1987 Science Yearbook.'' New York: Funk & Wagnalls, Inc., 1986. {{ISBN|0-7172-1517-2}}. 217–21.</ref> The incident dramatized the fact that radon levels in particular dwellings can occasionally be [[Order of magnitude|orders of magnitude]] higher than typical.<ref>{{cite web |date=April 22, 1997 |title=Nuclear reaction: why do citizens fear nuclear power? |url=https://www.pbs.org/wgbh/pages/frontline/shows/reaction/etc/script.html |website=www.pbs.org}}</ref> Since the incident in Pennsylvania, millions of short-term radon measurements have been taken in homes in the United States. Outside the United States, radon measurements are typically performed over the long term.<ref name="George-2008" />

In the United States, typical domestic exposures are of approximately 100&nbsp;Bq/m<sup>3</sup> (2.7&nbsp;pCi/L) indoors. Some level of radon will be found in all buildings. Radon mostly enters a building directly from the soil through the lowest level in the building that is in contact with the ground. High levels of radon in the water supply can also increase indoor radon air levels. Typical entry points of radon into buildings are cracks in solid foundations and walls, construction joints, gaps in suspended floors and around service pipes, cavities inside walls, and the water supply.<ref name="guide" /> Radon concentrations in the same place may differ by double/half over one hour, and the concentration in one room of a building may be significantly different from the concentration in an adjoining room.<ref name="USPHS90" />

The distribution of radon concentrations will generally differ from room to room, and the readings are averaged according to regulatory protocols. Indoor radon concentration is usually assumed to follow a [[log-normal distribution]] on a given territory.<ref>Numerous references, see, for instance, [http://www.geology.cz/extranet/vav/geochemie-zp/radon/sympozia/2006/radon-2006-258-265.pdf Analysis And Modelling Of Indoor Radon Distributions Using Extreme Values Theory] or [http://www.geology.cz/extranet/vav/geochemie-zp/radon/sympozia/2006/radon-2006-252-257.pdf Indoor Radon in Hungary (Lognormal Mysticism)] for a discussion.</ref> Thus, the [[geometric mean]] is generally used for estimating the "average" radon concentration in an area.<ref>{{cite web |title=Data Collection and Statistical Computations |url=http://aprg.utoledo.edu/radon/datacoll.html |url-status=dead |archive-url=http://arquivo.pt/wayback/20160519081621/http://aprg.utoledo.edu/radon/datacoll.html |archive-date=2016-05-19 |access-date=2023-09-23 |website=University of Toledo}}</ref> The mean concentration ranges from less than 10&nbsp;Bq/m<sup>3</sup> to over 100&nbsp;Bq/m<sup>3</sup> in some European countries.<ref>{{citation |access-date=17 August 2013 |url=http://www.unscear.org/docs/reports/2006/09-81160_Report_Annex_E_2006_Web.pdf |publisher=United Nations |date=2008 |work=Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (2006) |volume=2 |pages=209–210 |title=Annex E: Sources to effects assessment for radon in homes and workplaces}}</ref>

Some of the highest radon hazard in the US is found in [[Iowa]] and in the [[Appalachian Mountains|Appalachian Mountain]] areas in southeastern Pennsylvania.<ref>{{cite web |last1=Price |first1=Phillip N. |last2=Nero |first2=A. |last3=Revzan |first3=K. |last4=Apte |first4=M. |last5=Gelman |first5=A. |last6=Boscardin |first6=W. John |title=Predicted County Median Concentration |publisher=Lawrence Berkeley National Laboratory |url=http://eetd.lbl.gov/IEP/high-radon/USgm.htm |access-date=2008-02-12 |archive-url=https://web.archive.org/web/20071231195400/http://eetd.lbl.gov/IEP/high-radon/USgm.htm <!--Added by H3llBot--> |archive-date= 2007-12-31}}</ref> Iowa has the highest average radon concentrations in the US due to significant [[glaciation]] that ground the granitic rocks from the [[Canadian Shield]] and deposited it as soils making up the rich Iowa farmland.<ref>{{cite web |url=http://www.cheec.uiowa.edu/misc/radon.html |title=The Iowa Radon Lung Cancer Study |author=Field, R. William |publisher=Department of Occupational and Environmental Health, University of Iowa |date = 2003}}</ref> Many cities within the state, such as [[Iowa City]], have passed requirements for radon-resistant construction in new homes. The second highest readings in Ireland were found in office buildings in the Irish town of [[Mallow, County Cork]], prompting local fears regarding lung cancer.<ref>{{Cite news |url=https://www.rte.ie/news/2007/0920/93731-radon/ |title=Record radon levels found at Mallow office |date=2007-09-20 |work=RTE.ie |access-date=2018-09-09 |language=en}}</ref>
[[File:Stanowisko pomiaru radonu glebowego wf pw.jpg|thumb|left|A fixed-location device to measure soil concentrations of radon at the [[Warsaw University of Technology]]]]
Since radon is a colorless, odorless gas, the only way to know how much is present in the air or water is to perform tests. In the US, radon test kits are available to the public at retail stores, such as hardware stores, for home use, and testing is available through licensed professionals, who are often [[home inspector]]s. Efforts to reduce indoor radon levels are called [[radon mitigation]]. In the US, the EPA recommends all houses be tested for radon. In the UK, under the Housing Health & Safety Rating System, property owners have an obligation to evaluate potential risks and hazards to health and safety in a residential property.<ref>{{Cite web|last=Featherstone|first=Sarah|date=10 March 2021|title=Dangers Of Radon Gas - Test & Guide For Landlords 2021|url=https://thebla.co.uk/dangers-of-radon-gas-test-guide-for-landlords-2021/|access-date=2021-05-16|language=en-GB}}</ref> Alpha-radiation monitoring over the long term is a method of testing for radon that is more common in countries outside the United States.<ref name="George-2008" />