Editing Cosmic ray (section)

===Role in ambient radiation===
Cosmic rays constitute a fraction of the annual radiation exposure of human beings on the Earth, averaging 0.39{{nbsp}}mSv out of a total of 3{{nbsp}}mSv per year (13% of total background) for the Earth's population. However, the background radiation from cosmic rays increases with altitude, from 0.3{{nbsp}}mSv per year for sea-level areas to 1.0{{nbsp}}mSv per year for higher-altitude cities, raising cosmic radiation exposure to a quarter of total background radiation exposure for populations of said cities. Airline crews flying long-distance high-altitude routes can be exposed to 2.2{{nbsp}}mSv of extra radiation each year due to cosmic rays, nearly doubling their total exposure to ionizing radiation.

{| class="wikitable" style="text-align:center"
|- style="background:#ececec;"
|+ Average annual radiation exposure ([[millisievert]]s)
|-
! colspan="2" |Radiation
! colspan="2" |[[UNSCEAR]]<ref>UNSCEAR [http://www.unscear.org/docs/reports/2008/09-86753_Report_2008_Annex_B.pdf "Sources and Effects of Ionizing Radiation"] page 339 retrieved 29 June 2011</ref><ref>[[:ja:放射線医学総合研究所|Japan NIRS]] [http://www.aec.go.jp/jicst/NC/iinkai/teirei/siryo2010/siryo59/siryo1.pdf UNSCEAR 2008 report] page 8 retrieved 29 June 2011</ref>
! Princeton<ref>Princeton.edu [http://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm "Background radiation"] {{Webarchive|url=https://web.archive.org/web/20110609095603/http://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm|date=9 June 2011}} retrieved 29 June 2011</ref>
! Wa State<ref>Washington state Dept. of Health [http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs10bkvsman.htm "Background radiation"] {{webarchive|url=https://web.archive.org/web/20120502102254/http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs10bkvsman.htm |date=2 May 2012 }} retrieved 29 June 2011</ref>
! MEXT<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 29 June 2011</ref>
! rowspan="2" | Remark
|-
! Type !! Source !! World<br /> average !! Typical range !! US !! US !! Japan
|-
| rowspan="5" | Natural || Air || 1.26 || 0.2–10.0<sup>a</sup> || 2.29 || 2.00 || 0.40 || <small>Primarily from radon,</small> <sup>(a)</sup><small>depends on indoor accumulation of radon gas.</small>
|-
| Internal || 0.29 || 0.2–1.0<sup>b</sup> || 0.16 || 0.40 || 0.40 || <small>Mainly from radioisotopes in food ([[potassium-40|<sup>40</sup>K]], <sup>14</sup>C, etc.)</small> <sup>(b)</sup><small>depends on diet.</small>
|-
| Terrestrial || 0.48 || 0.3–1.0<sup>c</sup> || 0.19 || 0.29 || 0.40 || <sup>(c)</sup><small>Depends on soil composition and building material of structures.</small>
|- style="background:orange;"
| Cosmic || 0.39 || 0.3–1.0<sup>d</sup> || 0.31 || 0.26 || 0.30 || <sup>(d)</sup><small>Generally increases with elevation.</small>
|-
| '''Subtotal''' || 2.40 || 1.0–13.0 || 2.95 || 2.95 || 1.50 ||
|-
| rowspan="4" | Artificial || Medical || 0.60 || 0.03–2.0 || 3.00 || 0.53 || 2.30 ||
|-
| Fallout || 0.007 || 0–1+ || – || – || 0.01 || <small>Peaked in 1963 (prior to the [[Partial Test Ban Treaty]]) with [[Chernobyl nuclear accident|a spike in 1986]]; still high near nuclear test and accident sites.<br />For the United States, fallout is incorporated into other categories.</small>
|-
| Others || 0.0052 || 0–20 || 0.25 || 0.13 || 0.001|| <small>Average annual occupational exposure is 0.7 mSv; mining workers have higher exposure. <br />Populations near nuclear plants have an additional ≈0.02 mSv of exposure annually.</small>
|-
| '''Subtotal''' || 0.6 || 0 to tens || 3.25 || 0.66 || 2.311 ||
|-
| colspan="2" | '''Total''' || 3.00 || 0 to tens || 6.20 || 3.61 || 3.81 ||
|}
<small>Figures are for the time before the [[Fukushima Daiichi nuclear disaster]]. Human-made values by UNSCEAR are from the Japanese National Institute of Radiological Sciences, which summarized the UNSCEAR data.</small>