Editing Background radiation

{{Short description|Measure of ionizing radiation in the environment}}
{{For|background radiation from space|cosmic background radiation}}
{{Use dmy dates|date=April 2019}}

'''Background radiation''' is a measure of the level of [[ionizing radiation]] present in the environment at a particular location which is {{em|not}} due to deliberate introduction of radiation sources.

Background radiation originates from a variety of sources, both natural and artificial. These include both [[cosmic radiation]] and [[environmental radioactivity]] from [[naturally occurring radioactive material]]s (such as [[radon]] and [[radium]]), as well as man-made medical [[X-ray|X-rays]], [[Nuclear fallout|fallout]] from [[nuclear weapons testing]] and [[nuclear accident]]s.

==Definition==
Background radiation is defined by the [[International Atomic Energy Agency]] as "Dose or the dose rate (or an observed measure related to the dose or dose rate) attributable to all sources other than the one(s) specified.<ref name="IAEA Safety Glossary 2007">{{cite book|title = IAEA Safety Glossary: Terminology Used in Nuclear Safety and Radiation Protection |date = 2007|author = International Atomic Energy Agency|isbn = 9789201007070}}</ref> A distinction is thus made between the dose which is already in a location, which is defined here as being "background", and the dose due to a deliberately introduced and specified source. This is important where radiation measurements are taken of a specified radiation source, where the existing background may affect this measurement. An example would be measurement of radioactive contamination in a gamma radiation background, which could increase the total reading above that expected from the contamination alone.

However, if no radiation source is specified as being of concern, then the total radiation dose measurement at a location is generally called the '''background radiation''', and this is usually the case where an ambient dose rate is measured for environmental purposes.

==Background dose rate examples==

Background radiation varies with location and time, and the following table gives examples:

{| class="wikitable" style="text-align:center"
|- style="background:#ececec;"
|+ Average annual human exposure to ionizing radiation in [[millisievert]]s (mSv) per year
|-
! Radiation source !! World<ref name="UNSCEAR2008">{{cite book |author=United Nations Scientific Committee on the Effects of Atomic Radiation|title=Sources and effects of ionizing radiation |date=2008 |publication-date=2010 |publisher=United Nations |location=New York |isbn=978-92-1-142274-0 |url=http://www.unscear.org/unscear/en/publications/2008_1.html |access-date=9 November 2012|page=4}}</ref>
! US<ref name="NCRP106">{{cite book|title=Ionizing radiation exposure of the population of the United States|year=2009|publisher=National Council on Radiation Protection and Measurements|location=Bethesda, Md.|isbn=978-0-929600-98-7|id=NCRP No. 160|url=http://www.ncrppublications.org/Reports/160|access-date=9 November 2012|archive-date=2 February 2014|archive-url=https://web.archive.org/web/20140202092721/http://www.ncrppublications.org/Reports/160|url-status=dead}}</ref>
! Japan<ref>Ministry of Education, Culture, Sports, Science, and Technology of Japan [http://www.kankyo-hoshano.go.jp/04/04-1.html "Radiation in environment"] {{Webarchive|url=https://web.archive.org/web/20110322231148/http://www.kankyo-hoshano.go.jp/04/04-1.html |date=22 March 2011 }} retrieved 2011-6-29</ref>
! Remark
|-
| Inhalation of air || 1.26 || 2.28 || 0.40 || <small>mainly from [[radon]], depends on indoor accumulation</small>
|-
| Ingestion of food & water || 0.29 || 0.28 || 0.40 || <small>([[potassium-40]], [[carbon-14]], etc.)</small>
|-
| Terrestrial background radiation from ground || 0.48 || 0.21 || 0.40 || <small>depends on soil and building material</small>
|-
| Cosmic radiation from space || 0.39 || 0.33 || 0.30 || <small>depends on altitude</small>
|- style="border-bottom: 3px solid grey;"
| '''sub total (natural)''' || 2.40 || 3.10 || 1.50 || <small>sizeable population groups receive 10–20&nbsp;mSv</small>
|-
| Medical || 0.60 || 3.00 || 2.30 || <small>worldwide figure excludes [[radiotherapy]]; <br />US figure is mostly [[CT scan]]s and [[nuclear medicine]].</small>
|-
| Consumer items || – || 0.13 || || <small>cigarettes, air travel, building materials, etc.</small>
|-
| Atmospheric nuclear testing || 0.005 || – || 0.01 || <small>peak of 0.11&nbsp;mSv in 1963 and declining since; higher near sites</small>
|-
| Occupational exposure || 0.005 || 0.005 || 0.01 || <small>worldwide average to workers only is 0.7&nbsp;mSv, mostly due to radon in mines;<ref name=UNSCEAR2008 /> <br />US is mostly due to medical and aviation workers.<ref name=NCRP106 /></small>
|-
| Chernobyl accident || 0.002 || – || 0.01 || <small>peak of 0.04&nbsp;mSv in 1986 and declining since; higher near site</small>
|-
| Nuclear fuel cycle || 0.0002 || || 0.001|| <small>up to 0.02&nbsp;mSv near sites; excludes occupational exposure</small>
|-
| Other || – || 0.003 || || <small>Industrial, security, medical, educational, and research</small>
|- style="border-bottom: 3px solid grey;"
| '''sub total (artificial)''' || 0.61 || 3.14 || 2.33 ||
|-
| '''Total''' || 3.01 || 6.24 || 3.83 || '''millisieverts per year'''
|}

==Natural background radiation==
[[File:Atomic Testing Museum weather display cropped.jpg|thumb|The weather station outside of the [[Atomic Testing Museum]] on a hot summer day. Displayed background [[Gamma ray|gamma radiation]] level is 9.8&nbsp;[[μR/h]] (0.82&nbsp;mSv/a) This is very close to the world average background radiation of 0.87&nbsp;mSv/a from cosmic and terrestrial sources.]]
[[File:Cloud chambers played an important role of particle detectors.jpg |thumb|upright|[[Cloud chamber]]s used by early researchers first detected cosmic rays and other background radiation.  They can be used to visualize the background radiation]]
Radioactive material is found throughout nature. Detectable amounts occur naturally in [[soil]], rocks, water, air, and vegetation, from which it is inhaled and ingested into the body. In addition to this ''internal exposure'', humans also receive ''external exposure'' from radioactive materials that remain outside the body and from cosmic radiation from space. The worldwide average natural [[effective radiation dose|dose]] to humans is about {{convert|2.4|mSv|mrem|abbr=on|lk=on}} per year.<ref name=UNSCEAR2008 /> This is four times the worldwide average artificial radiation exposure, which in 2008 amounted to about {{convert|0.6|mSv|mrem|lk=on}} per year. In some developed countries, like the US and Japan, artificial exposure is, on average, greater than the natural exposure, due to greater access to [[medical imaging]]. In Europe, average natural background exposure by country ranges from under {{cvt|2|mSv|mrem}} annually in the United Kingdom to more than {{cvt|7|mSv|mrem}} annually for some groups of people in Finland.<ref name=RadMapEurope>{{cite web|url=http://www.world-nuclear.org/info/Safety-and-Security/Radiation-and-Health/Naturally-Occurring-Radioactive-Materials-NORM/|title=Naturally-Occurring Radioactive Materials (NORM)|date=March 2019|website=World Nuclear Association|access-date=26 August 2014|archive-date=20 January 2016|archive-url=https://web.archive.org/web/20160120074033/http://www.world-nuclear.org/info/Safety-and-Security/Radiation-and-Health/Naturally-Occurring-Radioactive-Materials-NORM/|url-status=dead}}</ref>

The [[International Atomic Energy Agency]] states:
:"Exposure to radiation from natural sources is an inescapable feature of everyday life in both working and public environments. This exposure is in most cases of little or no concern to society, but in certain situations the introduction of health protection measures needs to be considered, for example when working with uranium and thorium ores and other Naturally Occurring Radioactive Material ([[NORM]]). These situations have become the focus of greater attention by the Agency in recent years."<ref>{{cite web |url = http://www-ns.iaea.org/tech-areas/rw-ppss/exposure-to-natural-radiation.asp?s=3 |publisher = IAEA |website = Nuclear Safety & Security |title = Exposure to radiation from natural sources |archive-url = https://web.archive.org/web/20160209112421/http://www-ns.iaea.org/tech-areas/rw-ppss/exposure-to-natural-radiation.asp?s=3 |archive-date = 9 February 2016 |access-date = 4 January 2016 |url-status = live }}</ref>

===Terrestrial sources===
{{Main|Environmental radioactivity}}
'''Terrestrial background radiation''', for the purpose of the table above, only includes sources that remain external to the body. The major [[radionuclide]]s of concern are [[potassium]], [[uranium]] and [[thorium]] and their decay products, some of which, like [[radium]] and [[radon]] are intensely radioactive but occur in low concentrations. Most of these sources have been decreasing, due to [[radioactive decay]] since the formation of the Earth, because there is no significant amount currently transported to the Earth. Thus, the present activity on Earth from [[uranium-238]] is only half as much as it originally was because of its 4.5&nbsp;[[1000000000 (number)|billion]] year half-life, and [[potassium-40]] (half-life 1.25 billion years) is only at about 8% of original activity. But during the time that humans have existed the amount of radiation has decreased very little.

Many shorter half-life (and thus more intensely radioactive) isotopes have not decayed out of the terrestrial environment because of their on-going natural production. Examples of these are [[radium]]-226 (decay product of thorium-230 in decay chain of uranium-238) and [[radon-222]] (a decay product of [[radium]]-226 in said chain).

Thorium and uranium (and their daughters) primarily undergo [[alpha decay|alpha]] and [[beta decay]], and are not easily detectable. However, many of their [[daughter product]]s are strong gamma emitters. [[Thorium-232]] is detectable via a 239&nbsp;keV peak from [[lead-212]], 511, 583 and 2614&nbsp;keV from [[thallium-208]], and 911 and 969&nbsp;keV from [[actinium-228]]. Uranium-238 manifests as 609, 1120, and 1764&nbsp;keV peaks of bismuth-214 (''cf.'' the same peak for atmospheric radon). Potassium-40 is detectable directly via its 1461&nbsp;keV gamma peak.<ref name="DetNuc"/>

The level over the sea and other large bodies of water tends to be about a tenth of the terrestrial background. Conversely, coastal areas (and areas by the side of fresh water) may have an additional contribution from dispersed sediment.<ref name="DetNuc"/>

===Airborne sources===
The biggest source of natural background radiation is airborne [[radon]], a radioactive gas that emanates from the ground. Radon and its [[isotope]]s, parent [[radionuclide]]s, and [[decay product]]s all contribute to an average inhaled dose of 1.26&nbsp;[[Sievert#Common SI usage|mSv/a]] (millisievert [[wikt:per annum|per year]]). Radon is unevenly distributed and varies with weather, such that much higher doses apply to many areas of the world, where it represents a [[Health effects of radon|significant health hazard]]. Concentrations over 500 times the world average have been found inside buildings in Scandinavia, the United States, Iran, and the Czech Republic.<ref name="UNSCEAR2006E">{{cite book|author=United Nations Scientific Committee on the Effects of Atomic Radiation|title=Effects of Ionizing Radiation |date=2006 |publication-date=2008 |publisher=United Nations|location=New York|isbn=978-92-1-142263-4|volume=II|chapter=Annex E: Sources-to-effects assessment for radon in homes and workplaces|chapter-url=http://www.unscear.org/docs/reports/2006/09-81160_Report_Annex_E_2006_Web.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.unscear.org/docs/reports/2006/09-81160_Report_Annex_E_2006_Web.pdf |archive-date=2022-10-09 |url-status=live|access-date=2 December 2012}}</ref> Radon is a decay product of uranium, which is relatively common in the Earth's crust, but more concentrated in ore-bearing rocks scattered around the world. Radon seeps out of these [[ores]] into the atmosphere or into ground water or infiltrates into buildings. It can be inhaled into the lungs, along with its [[decay product]]s, where they will reside for a period of time after exposure.

Although radon is naturally occurring, exposure can be enhanced or diminished by human activity, notably house construction. A poorly sealed dwelling floor, or poor basement ventilation, in an otherwise well insulated house can result in the accumulation of radon within the dwelling, exposing its residents to high concentrations. The widespread construction of well insulated and sealed homes in the northern industrialized world has led to radon becoming the primary source of background radiation in some localities in northern North America and Europe.{{citation needed|date=December 2012}} Basement sealing and suction ventilation reduce exposure. Some building materials, for example [[lightweight concrete]] with [[alum shale]], [[phosphogypsum]] and Italian [[tuff]], may emanate radon if they contain [[radium]] and are porous to gas.<ref name=UNSCEAR2006E />

Radiation exposure from radon is indirect. Radon has a short half-life (4 days) and decays into other solid particulate [[Decay chain#Radium series|radium-series]] radioactive nuclides. These radioactive particles are inhaled and remain lodged in the lungs, causing continued exposure. Radon is thus assumed to be the second leading cause of [[lung cancer]] after [[tobacco smoking|smoking]], and accounts for 15,000 to 22,000 cancer deaths per year in the US alone.<ref>{{cite web| url = http://www.cancer.gov/cancertopics/factsheet/Risk/radon| title = Radon and Cancer: Questions and Answers – National Cancer Institute (USA)| date = 6 December 2011}}</ref>{{better source needed|date=December 2012}}<!--Radon may also dissolve in groundwater and be ingested, producing a dose to the stomach and the foetus. But this section is about air, inhalation only--> However, the discussion about the opposite experimental results is still going on.<ref>{{cite journal |last=Fornalski |first=K. W. |author2=Adams, R. |author3=Allison, W. |author4=Corrice, L. E. |author5=Cuttler, J. M. |author6=Davey, Ch. |author7=Dobrzyński, L. |author8=Esposito, V. J. |author9=Feinendegen, L. E. |author10=Gomez, L. S. |author11=Lewis, P. |author12=Mahn, J. |author13=Miller, M. L. |author14=Pennington, Ch. W. |author15=Sacks, B. |author16=Sutou, S. |author17=Welsh, J. S. |pmid=26223888 |title=The assumption of radon-induced cancer risk |year=2015 |journal=Cancer Causes & Control |doi=10.1007/s10552-015-0638-9 |issue=26 |volume=10 |pages=1517–18|s2cid=15952263 }}</ref>

About 100,000&nbsp;Bq/m<sup>3</sup> of radon was found in [[Health effects of radon#Accumulation in dwellings|Stanley Watras's]] basement in 1984.<ref>{{cite conference |url=http://wpb-radon.com/Radon_research_papers/1995%20Nashville,%20TN/1995_14_Indoor%20Radon%20Concentration%20Data--Geographic%20and%20Geologic%20Distribution,%20Captial%20District,%20NY.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://wpb-radon.com/Radon_research_papers/1995%20Nashville,%20TN/1995_14_Indoor%20Radon%20Concentration%20Data--Geographic%20and%20Geologic%20Distribution,%20Captial%20District,%20NY.pdf |archive-date=2022-10-09 |url-status=live |title=Indoor Radon Concentration Data: Its Geographic and Geologic Distribution, an Example from the Capital District, NY |first1=John J. |last1=Thomas |first2=Barbara R. |last2=Thomas |first3=Helen M. |last3=Overeynder |date= 27–30 September 1995  |conference=International Radon Symposium |conference-url=http://internationalradonsymposium.org/ |publisher=American Association of Radon Scientists and Technologists |location=Nashville, TN |access-date=2012-11-28}}</ref><ref>{{cite book|last1=Upfal |first1=Mark J. |last2=Johnson |first2=Christine |title=Occupational, industrial, and environmental toxicology|year=2003|publisher=Mosby|location=St Louis, Missouri|isbn=9780323013406|chapter-url=http://toxicology.ws/Greenberg/Chapter%2065%20-%20Residential%20Radon.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://toxicology.ws/Greenberg/Chapter%2065%20-%20Residential%20Radon.pdf |archive-date=2022-10-09 |url-status=live|edition=2nd|chapter=65 Residential Radon|editor1-first=Michael I. |editor1-last=Greenberg |editor2-first=Richard J. |editor2-last=Hamilton |editor3-first=Scott D. |editor3-last=Phillips |editor4-first=Gayla J. |editor4-last=McCluskey|access-date=28 November 2012}}</ref> He and his neighbours in [[Boyertown, Pennsylvania]], United States may hold the record for the most radioactive dwellings in the world. International radiation protection organizations estimate that a [[committed dose]] may be calculated by multiplying the [[equilibrium equivalent concentration]] (EEC) of radon by a factor of 8 to 9 {{sfrac|nSv·m<sup>3</sup>|Bq·h}} and the EEC of [[thoron]] by a factor of 40 {{sfrac|nSv·m<sup>3</sup>|Bq·h}}.<ref name=UNSCEAR2008 /><!-- The 8 is from ICRP, noted by UNSCEAR along with their own value of 9-->

Most of the atmospheric background is caused by radon and its decay products. The [[gamma spectroscopy|gamma spectrum]] shows prominent peaks at 609, 1120, and 1764&nbsp;[[keV]], belonging to [[bismuth-214]], a radon decay product. The atmospheric background varies greatly with wind direction and meteorological conditions. Radon also can be released from the ground in bursts and then form "radon clouds" capable of traveling tens of kilometers.<ref name="DetNuc">Gary W. Philips, David J. Nagel, Timothy Coffey – [http://large.stanford.edu/courses/2011/ph241/keller1/docs/phillips.pdf A Primer on the Detection of Nuclear and Radiological Weapons], Center for Technology and National Security Policy, National Defense University, May 2005</ref>

===Cosmic radiation===
{{Main|Cosmic ray}}
[[Image:Sievert-sigle.png|thumb|upright=1.3|Estimate of the maximum dose of radiation received at an altitude of 12 km 20 January 2005, following a violent solar flare. The doses are expressed in microsieverts per hour.]]
The Earth and all living things on it are constantly bombarded by radiation from outer space. This radiation primarily consists of positively charged ions from [[proton]]s to [[iron]] and larger [[atomic nucleus|nuclei]] derived from outside the [[Solar System]]. This radiation interacts with atoms in the atmosphere to create an [[air shower (physics)|air shower]] of secondary radiation, including [[X-ray]]s, [[muon]]s, [[proton]]s, [[alpha particle]]s, [[pion]]s, [[electron]]s, and [[neutron]]s. The immediate dose from cosmic radiation is largely from muons, neutrons, and electrons, and this dose varies in different parts of the world based largely on the [[geomagnetic field]] and altitude. For example, the city of [[Denver]] in the United States (at 1650 meters elevation) receives a cosmic ray dose roughly twice that of a location at sea level.<ref>{{cite web
 | url =http://www.units.miamioh.edu/ehso/radiationtraining/backgroundradiation/index.htm
 | title =Background Radiation & Other Sources of Exposure 
 | website =Radiation Safety Training
 | publisher =[[Miami University]]
 | access-date =30 September 2016
 }}</ref> This radiation is much more intense in the upper [[troposphere]], around 10&nbsp;km altitude, and is thus of particular concern for [[airline]] crews and frequent passengers, who spend many hours per year in this environment. During their flights airline crews typically get an additional occupational dose between {{cvt|2.2|mSv|mrem}} per year <ref>{{cite web|title=Radiation Exposure During Commercial Airline Flights|access-date=2011-03-17|url=http://www.hps.org/publicinformation/ate/faqs/commercialflights.html}}</ref> and 2.19 mSv/year,<ref>{{cite web|url=http://www.hps.org/publicinformation/ate/faqs/commercialflights.html|title=Radiation exposure during commercial airline flights|author=Health Physics Society|access-date=2013-01-24}}</ref> according to various studies.<ref>{{cite web
 | url =https://www.faa.gov/data_research/research/med_humanfacs/aeromedical/radiobiology/
 | title =Radiobiology Research Team
 | website =Federal Aviation Administration
 | access-date =23 January 2022}}</ref>

Similarly, cosmic rays cause higher background exposure in [[astronaut]]s than in humans on the surface of Earth. Astronauts in low [[orbit]]s, such as in the [[International Space Station]] or the [[Space Shuttle]], are partially shielded by the [[magnetic field]] of the Earth, but also suffer from the [[Van Allen radiation belt]] which accumulates cosmic rays and results from the Earth's magnetic field. Outside low Earth orbit, as experienced by the [[Apollo program|Apollo]] astronauts who traveled to the [[Moon]], this background radiation is much more intense, and represents a considerable obstacle to potential future long term human exploration of the [[moon landing|Moon]] or [[Human mission to Mars|Mars]].

Cosmic rays also cause [[Nuclear transmutation|elemental transmutation]] in the atmosphere, in which secondary radiation generated by the cosmic rays combines with [[atomic nuclei]] in the atmosphere to generate different [[nuclide]]s. Many so-called [[cosmogenic nuclide]]s can be produced, but probably the most notable is [[carbon-14]], which is produced by interactions with [[nitrogen]] atoms. These cosmogenic nuclides eventually reach the Earth's surface and can be incorporated into living organisms. The production of these nuclides varies slightly with short-term variations in solar cosmic ray flux, but is considered practically constant over long scales of thousands to millions of years. The constant production, incorporation into organisms and relatively short [[half-life]] of carbon-14 are the principles used in [[radiocarbon dating]] of ancient biological materials, such as wooden artifacts or human remains.

The cosmic radiation at sea level usually manifests as 511&nbsp;keV gamma rays from annihilation of [[positron]]s created by nuclear reactions of high energy particles and gamma rays. At higher altitudes there is also the contribution of continuous [[bremsstrahlung]] spectrum.<ref name="DetNuc"/>

===Food and water===
Two of the essential elements that make up the human body, namely potassium and carbon, have radioactive isotopes that add significantly to our background radiation dose. An average human contains about 17 milligrams of [[potassium-40]] (<sup>40</sup>K) and about 24 nanograms (10<sup>−9</sup>&nbsp;g) of [[carbon-14]] (<sup>14</sup>C),<ref>{{Cite web |title=Radioactive Human Body |url=https://sciencedemonstrations.fas.harvard.edu/presentations/radioactive-human-body |access-date=2022-10-12 |website=sciencedemonstrations.fas.harvard.edu |language=en}}</ref> (half-life 5,730 years). Excluding internal contamination by external radioactive material, these two are the largest components of internal radiation exposure from biologically functional components of the human body. About 4,000 nuclei of <sup>40</sup>K <ref>{{cite web |url = http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page102829&pageContentId=icb.pagecontent270775&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent270775 |title = Radioactive human body&nbsp;– Harvard University Natural Science Lecture Demonstrations |archive-url=https://web.archive.org/web/20150612194741/http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page102829&pageContentId=icb.pagecontent270775&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent270775 |archive-date=12 June 2015 |url-status=dead}}</ref> decay per second, and a similar number of <sup>14</sup>C. The energy of [[beta particle]]s produced by <sup>40</sup>K is about 10 times that from the beta particles from <sup>14</sup>C decay.

<sup>14</sup>C is present in the human body at a level of about 3700 Bq (0.1&nbsp;μCi) with a [[biological half-life]] of 40 days.<ref>{{cite web|url = http://www.ead.anl.gov/pub/doc/carbon14.pdf|title = Carbon 14|work = Human Health Fact Sheet|date = August 2005|publisher = Argonne National Lab|archive-url = https://web.archive.org/web/20080227103725/http://www.ead.anl.gov/pub/doc/carbon14.pdf|archive-date = 27 February 2008|access-date = 4 April 2011|url-status = live}}</ref> This means there are about 3700 beta particles per second produced by the decay of <sup>14</sup>C. However, a <sup>14</sup>C atom is in the genetic information of about half the cells, while potassium is not a component of [[DNA]]. The decay of a <sup>14</sup>C atom inside DNA in one person happens about 50 times per second, changing a carbon atom to one of [[nitrogen]].<ref>{{cite book |last=Asimov |first=Isaac |author-link=Isaac Asimov |title=Only A Trillion |orig-year=1957 |edition=Revised and updated |year=1976 |publisher=ACE books |location=New York |pages=37–39 |chapter=The Explosions Within Us |isbn= 978-1-157-09468-5 }}</ref>

The global average internal dose from radionuclides other than radon and its decay products is 0.29&nbsp;mSv/a, of which 0.17&nbsp;mSv/a comes from <sup>40</sup>K, 0.12&nbsp;mSv/a comes from the uranium and thorium series, and 12&nbsp;μSv/a comes from <sup>14</sup>C.<ref name=UNSCEAR2008 />

===Areas with high natural background radiation===
Some areas have greater dosage than the country-wide averages.<ref>[http://www.taishitsu.or.jp/radiation/index-e.html Annual terrestrial radiation doses in the world] {{webarchive|url=https://web.archive.org/web/20070623020422/http://www.taishitsu.or.jp/radiation/index-e.html |date=23 June 2007 }}</ref> In the world in general, exceptionally high natural background locales include [[Ramsar, Mazandaran|Ramsar]] in Iran, [[Guarapari]] in Brazil, [[Karunagappalli]] in India,<ref>{{cite journal |pmid=10564957 |year=1999 |last1=Nair |first1=MK |last2=Nambi |first2=KS |last3=Amma |first3=NS |last4=Gangadharan |first4=P |last5= Jayalekshmi |first5= P |last6=Jayadevan |first6=S |last7=Cherian |first7=V |last8=Reghuram |first8=KN |title=Population study in the high natural background radiation area in Kerala, India |volume=152 |issue=6 Suppl |pages=S145–48 |journal=Radiation Research |doi=10.2307/3580134|bibcode=1999RadR..152S.145N |jstor=3580134 }}</ref> [[Arkaroola]] in Australia<ref>{{cite web|url=http://www.abc.net.au/catalyst/stories/s692473.htm|title=Extreme Slime|work=Catalyst|publisher=ABC|date=3 October 2002|archive-url=https://web.archive.org/web/20030415055740/http://www.abc.net.au/catalyst/stories/s692473.htm|archive-date=15 April 2003|access-date=2 March 2009|url-status=live}}</ref> and [[Yangjiang]] in China.<ref>{{cite journal| last =Zhang| first =SP| title =Mechanism study of adaptive response in high background radiation area of Yangjiang in China| pmid=21092626 | volume=44| issue =9| year=2010| journal=Zhonghua Yu Fang Yi Xue Za Zhi| pages=815–19}}</ref>

The highest level of purely natural radiation ever recorded on the Earth's surface was 90&nbsp;μGy/h on a Brazilian black beach (''areia preta'' in Portuguese) composed of [[monazite]].<ref>{{cite book|last=United Nations Scientific Committee on the Effects of Atomic Radiation|author-link=United Nations Scientific Committee on the Effects of Atomic Radiation|title=Sources and Effects of Ionizing Radiation|year=2000|publisher=United Nations|chapter-url=http://www.unscear.org/unscear/publications/2000_1.html|access-date=11 November 2012|page=121|volume=1|chapter=Annex B}}</ref> This rate would convert to 0.8 Gy/a for year-round continuous exposure, but in fact the levels vary seasonally and are much lower in the nearest residences. The record measurement has not been duplicated and is omitted from UNSCEAR's latest reports. Nearby tourist beaches in [[Guarapari]] and [[Cumuruxatiba]] were later evaluated at 14 and 15&nbsp;μGy/h.<ref>{{cite journal|last=Freitas|first=AC|author2=Alencar, AS|title=Gamma dose rates and distribution of natural radionuclides in sand beaches – Ilha Grande, Southeastern Brazil|journal=Journal of Environmental Radioactivity|year=2004|volume=75|issue=2|pages=211–23|doi=10.1016/j.jenvrad.2004.01.002|pmid=15172728|bibcode=2004JEnvR..75..211F |url=http://www.sr2.uerj.br/ceads/artigos_e_livros/Freitas_Antonio-2004-2.pdf|access-date=2 December 2012|issn=0265-931X|url-status=dead|archive-url=https://web.archive.org/web/20140221144543/http://www.sr2.uerj.br/ceads/artigos_e_livros/Freitas_Antonio-2004-2.pdf|archive-date=21 February 2014}}</ref><ref>{{cite conference |url=http://library.sinap.ac.cn/db/hedianwencui201103/%E5%85%A8%E6%96%87/41109077.pdf |title=Natural Radioactivity in Extreme South of Bahia, Brazil Using Gamma-Ray Spectrometry |first=Danilo C. |last=Vasconcelos |date=27 September – 2 October 2009 |conference=International Nuclear Atlantic Conference |conference-url=http://www.inac2011.com.br/ |publisher=Associação Brasileira de Energia Nuclear |location=Rio de Janeiro |isbn=978-85-99141-03-8 |access-date=2 December 2012 |display-authors=etal |archive-date=21 February 2014 |archive-url=https://web.archive.org/web/20140221213504/http://library.sinap.ac.cn/db/hedianwencui201103/%E5%85%A8%E6%96%87/41109077.pdf |url-status=dead }}</ref> Note that the values quoted here are in [[Gray (unit)|Grays]]. To convert to Sieverts (Sv) a radiation weighting factor is required; these weighting factors vary from 1 (beta & gamma) to 20 (alpha particles).

The highest background radiation in an inhabited area is found in [[Ramsar, Mazandaran|Ramsar]], primarily due to the use of local naturally radioactive limestone as a building material. The 1000 most exposed residents receive an average external [[effective radiation dose]] of {{cvt|6|mSv|mrem}} per year, six times the [[ICRP]] recommended limit for exposure to the public from artificial sources.<ref name=HNBR2009 /> They additionally receive a substantial internal dose from radon. Record radiation levels were found in a house where the effective dose due to ambient radiation fields was {{cvt|131|mSv|rem}} per year, and the internal [[committed dose]] from [[radon]] was {{cvt|72|mSv|rem}} per year.<ref name=HNBR2009>{{cite journal|last=Hendry|first=Jolyon H|author2=Simon, Steven L|author3=Wojcik, Andrzej|author4=Sohrabi, Mehdi|author5=Burkart, Werner|author6=Cardis, Elisabeth|author7=Laurier, Dominique|author8=Tirmarche, Margot|author9=Hayata, Isamu|title=Human exposure to high natural background radiation: what can it teach us about radiation risks?|journal=Journal of Radiological Protection|date=1 June 2009|volume=29|issue=2A|pages=A29–A42|doi=10.1088/0952-4746/29/2A/S03|pmid=19454802|pmc=4030667|url=http://cricket.biol.sc.edu/papers/natural/Hendry%20et%20al%202009.pdf|access-date=1 December 2012|bibcode=2009JRP....29...29H|archive-url=https://web.archive.org/web/20131021233519/http://cricket.biol.sc.edu/papers/natural/Hendry%20et%20al%202009.pdf|archive-date=21 October 2013|url-status=dead}}</ref> This unique case is over 80 times higher than the world average natural human exposure to radiation.

Epidemiological studies are underway to identify health effects associated with the high radiation levels in Ramsar. It is much too early to draw unambiguous statistically significant conclusions.<ref name=HNBR2009 /> While so far support for beneficial effects of chronic radiation (like longer lifespan) has been observed in few places only,<ref name=HNBR2009/> a protective and adaptive effect is suggested by at least one study whose authors nonetheless caution that data from Ramsar are not yet sufficiently strong to relax existing regulatory dose limits.<ref>{{cite journal|last=Ghiassi-nejad|first=M|author2=Mortazavi, SM|author3= Cameron, JR|author4= Niroomand-rad, A|author5= Karam, PA|title=Very high background radiation areas of Ramsar, Iran: preliminary biological studies|journal=Health Physics|date=January 2002|volume=82|issue=1|pmid=11769138|url=http://www.probeinternational.org/Ramsar.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.probeinternational.org/Ramsar.pdf |archive-date=2022-10-09 |url-status=live|access-date=11 November 2012|quote=Our preliminary studies seem to indicate the presence of adaptive response in the cells of some Ramsar residents, but we do not claim to have seen hormetic effects in any of those studied. Given the apparent lack of ill effects among observed populations of these high dose rate areas, these data suggest that current dose limits may be overly conservative. However, the available data do not seem sufficient to cause national or international advisory bodies to change their current conservative radiation protection recommendations;|pages=87–93 [92]|doi=10.1097/00004032-200201000-00011|bibcode=2002HeaPh..82...87G|s2cid=26685238}}</ref> However, the recent statistical analyses discussed that there is no correlation between the risk of negative health effects and elevated level of natural background radiation.<ref>{{cite journal |last=Dobrzyński |first=L. |author2=Fornalski, K.W. |author3=Feinendegen, L.E. |pmid=26674931 |title=Cancer Mortality Among People Living in Areas With Various Levels of Natural Background Radiation |year=2015 |journal=Dose-Response |doi=10.1177/1559325815592391 |issue=3 |volume=13 |pages=1–10 |pmc=4674188}}</ref>

===Photoelectric===
Background radiation doses in the immediate vicinity of particles of high atomic number materials, within the human body, have a small enhancement due to the [[photoelectric effect]].<ref>{{cite journal |pages=603–11 |doi=10.1098/rsif.2009.0300 |pmid=19776147 |title=Enhancement of natural background gamma-radiation dose around uranium microparticles in the human body |year=2009 |last1=Pattison |first1=J. E. |last2=Hugtenburg |first2=R. P. |last3=Green |first3=S. |journal=Journal of the Royal Society Interface |volume=7 |issue=45|pmc=2842777 }}</ref>

===Neutron background===
Most of the natural neutron background is a product of cosmic rays interacting with the atmosphere. The neutron energy peaks at around 1&nbsp;MeV and rapidly drops above. At sea level, the production of neutrons is about 20 neutrons per second per kilogram of material interacting with the cosmic rays (or, about 100–300 neutrons per square meter per second). The flux is dependent on geomagnetic latitude, with a maximum near the magnetic poles. At solar minimums, due to lower solar magnetic field shielding, the flux is about twice as high vs the solar maximum. It also dramatically increases during solar flares. In the vicinity of larger heavier objects, e.g. buildings or ships, the neutron flux measures higher; this is known as "cosmic ray induced neutron signature", or "ship effect" as it was first detected with ships at sea.<ref name="DetNuc"/>

==Artificial background radiation==
[[File:Kozloduy Nuclear Power Plant - Background radiation displays.jpg|thumb|Displays showing ambient radiation fields of 0.120–0.130&nbsp;μSv/h (1.05–1.14&nbsp;mSv/a) in a nuclear power plant. This reading includes natural background from cosmic and terrestrial sources.]]

===Atmospheric nuclear testing===
[[Image:US fallout exposure.png|right|thumb|Per capita [[thyroid]] doses in the continental United States resulting from all exposure routes from all atmospheric [[nuclear testing|nuclear tests]] conducted at the [[Nevada Test Site]] from 1951 to 1962.]]

[[File:Radiocarbon bomb spike.svg|thumb|Atmospheric <sup>14</sup>C [[Bomb pulse]], [[New Zealand]]<ref>{{cite journal|url=http://cdiac.esd.ornl.gov/trends/co2/welling.html |title=Atmospheric δ<sup>14</sup>C record from Wellington |access-date=2007-06-11 |journal=Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center |year=1994 |url-status=dead |archive-url=https://web.archive.org/web/20140201222225/http://cdiac.esd.ornl.gov/trends/co2/welling.html |archive-date=1 February 2014 }}</ref> and [[Austria]].<ref>{{cite journal| url=http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html| author=Levin, I.| title=δ<sup>14</sup>C record from Vermunt| journal=Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center| year=1994| display-authors=etal| access-date=4 January 2016| archive-url=https://web.archive.org/web/20080923105819/http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html| archive-date=23 September 2008| url-status=dead}}</ref> The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of <sup>14</sup>C in the Northern Hemisphere.<ref>{{cite web | url=http://www1.phys.uu.nl/ams/Radiocarbon.htm | publisher=University of Utrecht | title= Radiocarbon dating | access-date=2008-02-19}}</ref>]]

Frequent above-ground nuclear explosions between the 1940s and 1960s scattered a substantial amount of [[radioactive contamination]]. Some of this contamination is local, rendering the immediate surroundings highly radioactive, while some of it is carried longer distances as [[nuclear fallout]]; some of this material is dispersed worldwide. The increase in background radiation due to these tests peaked in 1963 at about 0.15&nbsp;mSv per year worldwide, or about 7% of average background dose from all sources. The [[Limited Test Ban Treaty]] of 1963 prohibited above-ground tests, thus by the year 2000 the worldwide dose from these tests has decreased to only 0.005&nbsp;mSv per year.<ref name="rrjhjx">{{Cite report |url=https://www.unscear.org/unscear/en/publications/2000_1.html |title=Sources and Effects of Ionizing Radiation - UNSCEAR 2000 Report to the General Assembly, with Scientific Annexes |last=United Nations Scientific Committee on the Effects of Atomic Radiation |date=2000 |language=en |access-date=2022-09-12}}</ref>

This [[global fallout]] has caused an estimated 200,000-460,000 deaths as of 2020.<ref name="s257">{{cite web | last=Adams | first=Lilly | title=Resuming Nuclear Testing a Slap in the Face to Survivors | website=The Equation | date=May 26, 2020 | url=https://blog.ucsusa.org/lilly-adams/resuming-nuclear-testing-a-slap-in-the-face-to-survivors/ | access-date=July 16, 2024}}</ref>

===Occupational exposure===
The [[ICRP|International Commission on Radiological Protection]] recommends limiting occupational radiation exposure to 50&nbsp;mSv (5 rem) per year, and 100&nbsp;mSv (10 rem) in 5 years.<ref name="ICRP103">{{cite book|title=The 2007 Recommendations of the International Commission on Radiological Protection|journal=Annals of the ICRP|year=2007|volume=37|series=ICRP publication 103|issue=2–4|url=http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103|access-date=17 May 2012|isbn=978-0-7020-3048-2|author=ICRP}}</ref>

However, '''background radiation''' for occupational doses includes radiation that is not measured by radiation dose instruments in potential occupational exposure conditions. This includes both offsite "natural background radiation" and any medical radiation doses. This value is not typically measured or known from surveys, such that variations in the total dose to individual workers is not known. This can be a significant confounding factor in assessing radiation exposure effects in a population of workers who may have significantly different natural background and medical radiation doses. This is most significant when the occupational doses are very low.

At an [[IAEA]] conference in 2002, it was recommended that occupational doses below 1–2 mSv per year do not warrant regulatory scrutiny.<ref>{{Cite web |date=30 August 2002 |title=OCCUPATIONAL RADIATION PROTECTION: PROTECTING WORKERS AGAINST EXPOSURE TO IONIZING RADIATION |url=http://www-pub.iaea.org/MTCD/publications/PDF/Pub1145_web.pdf |archive-url=https://web.archive.org/web/20031129163031/http://www-pub.iaea.org/MTCD/publications/PDF/Pub1145_web.pdf |archive-date=2003-11-29 |url-status=live |access-date=21 October 2022 |website=International Atomic Energy Agency}}</ref>

===Nuclear accidents===
[[File:G radiation-level scale 01.png |thumb|right| Radiation level in a range of situations, from normal activities up to the nuclear accidents. Each step up the scale indicates a tenfold increase in radiation level.]]

Under normal circumstances, nuclear reactors release small amounts of radioactive gases, which cause small radiation exposures to the public. Events classified on the [[International Nuclear Event Scale]] as incidents typically do not release any additional radioactive substances into the environment. Large releases of radioactivity from nuclear reactors are extremely rare. To the present day, there were two major ''civilian'' accidents – the [[Chernobyl accident]] and the [[Fukushima I nuclear accidents]] – which caused substantial contamination. The Chernobyl accident was the only one to cause immediate deaths.

Total doses from the Chernobyl accident ranged from 10 to 50 mSv over 20 years for the inhabitants of the affected areas, with most of the dose received in the first years after the disaster, and over 100 mSv for [[Liquidator (Chernobyl)|liquidators]]. There were 28 deaths from [[acute radiation syndrome]].<ref>{{cite web|url=https://www.who.int/ionizing_radiation/chernobyl/backgrounder/en/index.html|author=World Health Organization|title=Health effects of the Chernobyl accident: an overview|date=April 2006|access-date=2013-01-24}}</ref>

Total doses from the Fukushima I accidents were between 1 and 15 mSv for the inhabitants of the affected areas. Thyroid doses for children were below 50 mSv. 167 cleanup workers received doses above 100 mSv, with 6 of them receiving more than 250 mSv (the Japanese exposure limit for emergency response workers).<ref>{{cite journal|title=Fukushima's doses tallied|journal=Nature|volume=485|issue=7399|pages=423–24|author=Geoff Brumfiel|date=2012-05-23|doi=10.1038/485423a|pmid=22622542|bibcode=2012Natur.485..423B|doi-access=free}}</ref>

The average dose from the [[Three Mile Island accident]] was 0.01 mSv.<ref>{{cite web|url=https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html|title=Backgrounder on the Three Mile Island Accident|author=U.S. Nuclear Regulatory Commission|date=August 2009|access-date=2013-01-24}}</ref>

'''Non-civilian''': In addition to the civilian accidents described above, several accidents at early nuclear weapons facilities – such as the [[Windscale fire]], the contamination of the [[Techa River]] by the nuclear waste from the [[Mayak]] compound, and the [[Kyshtym disaster]] at the same compound – released substantial radioactivity into the environment. The Windscale fire resulted in thyroid doses of 5–20 mSv for adults and 10–60 mSv for children.<ref>{{cite web|url=http://karws.gso.uri.edu/Marsh/Newsgroups/Wscal-is.htm|title=Radiological Consequences of the 1957 Windscale Fire|date=1997-10-10|access-date=2013-01-24|url-status=dead|archive-url=https://web.archive.org/web/20130517075421/http://karws.gso.uri.edu/Marsh/Newsgroups/Wscal-is.htm|archive-date=17 May 2013}}</ref> The doses from the accidents at Mayak are unknown.

===Nuclear fuel cycle===
The [[Nuclear Regulatory Commission]], the [[United States Environmental Protection Agency]], and other U.S. and international agencies, require that licensees limit radiation exposure to individual members of the public to 1&nbsp;[[sievert|mSv]] (100 m[[roentgen equivalent man|rem]]) per year.

=== Energy sources ===
Per [[United Nations Economic Commission for Europe|UNECE]] life-cycle assessment, nearly all sources of energy result in some level of occupational and public exposure to [[radionuclide]]s as result of their manufacturing or operations. The following table uses man·[[Sievert]]/GW-annum:<ref>{{Cite web|title=Life Cycle Assessment of Electricity Generation Options {{!}} UNECE|url=https://unece.org/sed/documents/2021/10/reports/life-cycle-assessment-electricity-generation-options|access-date=2021-11-08|website=unece.org}}</ref>
{| class="wikitable sortable"
|+
!Source
!Public
!Occupational
|-
|Nuclear power
|0.43
|4.5
|-
|Coal (modern)
|0.7
|11
|-
|Coal (older)
|1.4
|11
|-
|Natural gas
|0.1
|0.02
|-
|Oil
|0.0003
|0.15
|-
|Geothermal
|1–20
|0.05
|-
|Solar power
|
|0.8
|-
|Wind power
|
|0.1
|-
|Biomass
|
|0.01
|}

====Coal burning====
Coal plants emit radiation in the form of radioactive [[fly ash]] which is inhaled and ingested by neighbours, and incorporated into crops. A 1978 paper from [[Oak Ridge National Laboratory]] estimated that coal-fired power plants of that time may contribute a whole-body committed dose of 19&nbsp;μSv/a to their immediate neighbours in a radius of 500 m.<ref>{{cite journal|last1=McBride|first1=J. P.|last2=Moore|first2=R. E. |last3=Witherspoon|first3=J. P.|last4=Blanco|first4=R. E.|title=Radiological impact of airborne effluents of coal and nuclear plants|journal=Science|date=8 Dec 1978|volume=202|issue=4372|pages=1045–50|url= http://www.ornl.gov/info/reports/1977/3445605115087.pdf |access-date=15 November 2012|doi=10.1126/science.202.4372.1045|pmid=17777943|bibcode=1978Sci...202.1045M|s2cid=41057679|archive-url=https://web.archive.org/web/20120927045329/http://www.ornl.gov/info/reports/1977/3445605115087.pdf |archive-date=27 September 2012|url-status=dead}}</ref> The [[United Nations Scientific Committee on the Effects of Atomic Radiation]]'s 1988 report estimated the committed dose 1&nbsp;km away to be 20&nbsp;μSv/a for older plants or 1&nbsp;μSv/a for newer plants with improved fly ash capture, but was unable to confirm these numbers by test.<ref>{{cite book|last=United Nations Scientific Committee on the Effects of Atomic Radiation|title=Sources, Effects and Risks of Ionizing Radiation|series=Radiation Research|volume=120|issue=1|pages=[https://archive.org/details/sourceseffectsri0000unit/page/187 187–88]|year=1988|publisher=United Nations|location=New York|isbn=978-92-1-142143-9|chapter-url=http://www.unscear.org/unscear/en/publications/1988.html|access-date=16 November 2012|chapter=Annex A|bibcode=1989RadR..120..187K|doi=10.2307/3577647|jstor=3577647|s2cid=7316994 |url=https://archive.org/details/sourceseffectsri0000unit/page/187}}</ref> When coal is burned, uranium, thorium and all the uranium daughters accumulated by disintegration&nbsp;– radium, radon, polonium&nbsp;– are released.<ref>{{cite journal|first1=Alex |last1=Gabbard |year=1993 |title= Coal Combustion: Nuclear Resource or Danger? |journal=Oak Ridge National Laboratory Review |volume=26 |issue=3–4 |pages=18–19 |url=http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html |url-status=dead |archive-url=https://web.archive.org/web/20070205103749/http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html |archive-date=5 February 2007  }}</ref> Radioactive materials previously buried underground in coal deposits are released as fly ash or, if fly ash is captured, may be incorporated into concrete manufactured with fly ash.

==Other sources of dose uptake==

===Medical===
The global average human exposure to artificial radiation is 0.6&nbsp;mSv/a, primarily from [[medical imaging]]. This medical component can range much higher, with an average of 3&nbsp;mSv per year across the USA population.<ref name=NCRP106 /> Other human contributors include smoking, air travel, radioactive building materials, historical nuclear weapons testing, nuclear power accidents and nuclear industry operation.

A typical chest x-ray delivers 20&nbsp;μSv (2 mrem) of effective dose.<ref>{{cite journal|last=Wall|first=B.F.|author2=Hart, D.|title=Revised Radiation Doses for Typical X-Ray Examinations|journal=The British Journal of Radiology|year=1997|volume=70|pages=437–439|url=http://bjr.birjournals.org/content/70/833/437.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://bjr.birjournals.org/content/70/833/437.full.pdf |archive-date=2022-10-09 |url-status=live|access-date=18 May 2012|pmid=9227222|issue=833|doi=10.1259/bjr.70.833.9227222}} (5,000 patient dose measurements from 375 hospitals)</ref> A dental x-ray delivers a dose of 5 to 10 μSv.<ref>{{cite book|last=Hart|first=D.|title=Radiation Exposure of the UK Population from Medical and Dental X-ray Examinations|year=2002|publisher=National Radiological Protection Board|isbn=978-0859514682|url=http://medicalphysicist.co.uk/nrpb_w4.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://medicalphysicist.co.uk/nrpb_w4.pdf |archive-date=2022-10-09 |url-status=live|author2=Wall, B.F.|access-date=18 May 2012|page=9}}{{Dead link|date=October 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> A [[CT scan#Scan dose|CT scan]] delivers an effective dose to the whole body ranging from 1 to 20 mSv (100 to 2000 mrem). The average American receives about 3&nbsp;mSv of diagnostic medical dose per year; countries with the lowest levels of health care receive almost none. Radiation treatment for various diseases also accounts for some dose, both in individuals and in those around them.

===Consumer items===
Cigarettes contain [[polonium-210]], originating from the decay products of radon, which stick to [[tobacco leaves]]. Heavy smoking results in a radiation dose of 160 mSv/year to localized spots at the bifurcations of segmental bronchi in the lungs from the decay of polonium-210. This dose is not readily comparable to the radiation protection limits, since the latter deal with whole body doses, while the dose from smoking is delivered to a very small portion of the body.<ref>{{cite web|url=http://hps.org/publicinformation/ate/q3137.html|title=Doses from cigarette smoking|author=Dade W. Moeller|work=Health Physics Society|access-date=2013-01-24|archive-date=2 August 2014|archive-url=https://web.archive.org/web/20140802103909/http://hps.org/publicinformation/ate/q3137.html|url-status=dead}}</ref>

==Radiation metrology==
In a radiation metrology laboratory, '''background radiation''' refers to the measured value from any incidental sources that affect an instrument when a specific radiation source sample is being measured. This background contribution, which is established as a stable value by multiple measurements, usually before and after sample measurement, is subtracted from the rate measured when the sample is being measured.

This is in accordance with the [[International Atomic Energy Agency]] definition of background as being "Dose or dose rate (or an observed measure related to the dose or dose rate) attributable to all sources other than the one(s) specified.<ref name="IAEA Safety Glossary 2007"/>

The same issue occurs with radiation protection instruments, where a reading from an instrument may be affected by the background radiation. An example of this is a [[scintillation detector]] used for surface contamination monitoring. In an elevated gamma background the scintillator material will be affected by the background gamma, which will add to the reading obtained from any contamination which is being monitored. In extreme cases it will make the instrument unusable as the background swamps the lower level of radiation from the contamination. In such instruments the background can be continually monitored in the "Ready" state, and subtracted from any reading obtained when being used in "Measuring" mode.

Regular Radiation measurement is carried out at multiple levels.  Government agencies compile radiation readings as part of environmental monitoring mandates, often making the readings available to the public and sometimes in near-real-time.  Collaborative groups and private individuals may also make real-time readings available to the public.  Instruments used for radiation measurement include the [[Geiger–Müller tube]] and the [[Scintillation detector]].  The former is usually more compact and affordable and reacts to several radiation types, while the latter is more complex and can detect specific radiation energies and types.  Readings indicate radiation levels from all sources including background, and real-time readings are in general unvalidated, but correlation between independent detectors increases confidence in measured levels.

'''List of near-real-time government radiation measurement sites, employing multiple instrument types:'''
* Europe and Canada: European Radiological Data Exchange Platform (EURDEP) [https://remap.jrc.ec.europa.eu/GammaDoseRates.aspx  Simple map of Gamma Dose Rates]
* USA: EPA Radnet [https://www.epa.gov/radnet/near-real-time-and-laboratory-data-state near-real-time and laboratory data by state]

'''List of international near-real-time collaborative/private measurement sites, employing primarily Geiger-Muller detectors:'''
* GMC map: http://www.gmcmap.com/ (mix of old-data detector stations and some near-real-time ones)
* Netc: http://www.netc.com/
* Radmon: http://www.radmon.org/
* Radiation Network: http://radiationnetwork.com/
* Radioactive@Home: http://radioactiveathome.org/map/ {{Webarchive|url=https://web.archive.org/web/20160329050624/http://radioactiveathome.org/map/ |date=29 March 2016 }}
* Safecast: [http://safecast.org/tilemap/?y=0&x=0&z=3 http://safecast.org/tilemap] (the green circles are real-time detectors)
* uRad Monitor: http://www.uradmonitor.com/

==See also==
* [[Background radiation equivalent time]] (BRET)
* [[Banana equivalent dose]]
* [[Environmental radioactivity]]
* [[Flight-time equivalent dose]]
* [[Noise (electronics)]]
* [[Low-background steel]]

==References==
{{Reflist|30em}}

==External links==
* [https://web.archive.org/web/20110521023544/http://www.rerf.or.jp/glossary_e/backgrou.htm Background radiation description] from the [[Radiation Effects Research Foundation]]
* [http://www.hps.org/publicinformation/ate/cat10.html Environmental and Background Radiation FAQ] from the [[Health Physics Society]]
* [http://www.ans.org/pi/resources/dosechart/ Radiation Dose Chart] {{Webarchive|url=https://web.archive.org/web/20180715152300/http://www.ans.org/pi/resources/dosechart/ |date=15 July 2018 }} from the [[American Nuclear Society]]
* [https://www.epa.gov/radiation/calculate-your-radiation-dose Radiation Dose Calculator] from the [[United States Environmental Protection Agency]]

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[[Category:Background radiation| ]]
[[Category:Cosmic rays]]
[[Category:Ionizing radiation]]
[[Category:Radioactivity]]