Editing Background radiation (section)

===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>