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Radium and radon in the environment

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Predicted fraction of U.S. homes have radon concentrations exceeding the EPA's recommended action level of 4 pCi/L
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Radiumandradonare important contributors toenvironmental radioactivity.Radon occurs naturally as a result of decay ofradioactiveelements in soil and it can accumulate in houses built on areas where such decay occurs. Radon is a major cause of cancer; it is estimated to contribute to ~2% of all cancer related deaths in Europe.[1]

Radium, like radon, is radioactive and is found in small quantities in nature and is hazardous to life if radiation exceeds 20-50 mSv/year. Radium is a decay product ofuraniumandthorium.[2]Radium may also be released into the environment by human activity, for example, in improperly discarded products painted withradioluminescentpaint.

Radium[edit]

In the oil and gas industries[edit]

Residues from theoilandgasindustry often containradiumand its daughters. The sulfate scale from an oil well can be very radium rich. The water inside an oil field is often very rich instrontium,bariumandradiumwhile seawater is very rich insulfateso if water from an oil well is discharged into the sea or mixed with seawater the radium is likely to be brought out of solution by the barium/strontium sulfate which acts as acarrierprecipitate.[3]

Radioluminescent (glow in the dark) products[edit]

Local contamination from radium-basedradioluminescentpaints having been improperly disposed of is not unknown.[4]

In radioactive quackery[edit]

Eben Byerswas a wealthy American socialite whose death in 1932 from using aradioactive quackeryproduct calledRadithoris a prominent example of a death caused by radium. Radithor contained ~1 μCi (40 kBq) of226Ra and 1 μCi of228Ra per bottle. Radithor was taken by mouth and radium, being acalciummimic, has a very longbiological halflifeinbone.[5]

Radon[edit]

Radonin air forms a part of thebackground radiation,which can be observed in acloud chamber

Most of the dose is due to the decay of thepolonium(218Po) andlead(214Pb) daughters of222Rn. By controlling exposure to the daughters the radioactive dose to theskinandlungscan be reduced by at least 90%. This can be done by wearing a dust mask, and wearing a suit to cover the entire body. Note that exposure tosmokeat the same time asradonand radon daughters will increase the harmful effect of the radon. Inuranium minersradon has been found to be morecarcinogenicinsmokersthan in non-smokers.[3]

Uranium series
The radium or uranium series.

Occurrence[edit]

Radon concentration in open air varies between 1 and 100 Bq m−3.[6]Radon can be found in somespring watersandhot springs.[7]The towns ofMisasa,Japan,andBad Kreuznach,Germanyboast radium-rich springs which emit radon, as doesRadium Springs, New Mexico.

Radon exhausts naturally from the ground, particularly in certain regions, especially but not only regions withgraniticsoils. Not all granitic regions are prone to high emissions of radon, for instance while the rock whichAberdeenis on is very radium rich the rock lacks the cracks required for the radon to migrate. In other nearby areas of Scotland (to the north of Aberdeen) and inCornwall/Devonthe radon is very much able to leave the rock.

Radon is a decay product ofradiumwhich in turn is a decay product of uranium. Maps of average radon levels in houses are available, to assist in planning mitigation measures.[8]

While high uranium in thesoil/rockunder a house does not always lead to a high radon level in air, a positive correlation between the uranium content of the soil and the radon level in air can be seen.

In air[edit]

Radon harmsindoor air qualityin many homes. (See "Radon in Houses" below.)

Radon (222Rn) released into the air decays to210Pband other radioisotopes and the levels of210Pb can be measured. It is important to note that the rate of deposition of this radioisotope is very dependent on the season. Here is a graph of the deposition rate observed inJapan.[9]

Lead-210 deposition rate as a function of time as observed in Japan

In groundwater[edit]

Well water can be very rich in radon; the use of this water inside a house is another route allowing radon to enter the house. The radon can enter the air and then be a source of exposure to the humans, or the water can be consumed by humans which is a different exposure route.[10]

Radon in rainwater[edit]

Rainwater can be highly radioactive due to high levels of radon and its decay progenies214Bi and214Pb; the concentrations of theseradioisotopescan be high enough to seriously disruptradiation monitoringat nuclear power plants.[11]The highest levels of radon in rainwater occurs during thunderstorms, and it is hypothesized that radon is concentrated in thunderstorms on account of the atom's positive electrical charge.[12]Estimates of the age of rain drops have been obtained from measuring the isotopic abundance of radon's short-lived decay progeny in rainwater.[13]

In the oil and gas industries[edit]

Water, oil and gas from a well often containradon.The radon decays to form solid radioisotopes which form coatings on the inside of pipework. In an oil processing plant the area of the plant wherepropaneis processed is often one of the more contaminated areas of the plant as radon has a similar boiling point to propane.[14]

In mines[edit]

Because uranium minerals emitradongas, and their harmful and highly radioactivedecay products,uranium mining is considerably more dangerous than other (already dangerous)hard rock mining,requiring adequate ventilation systems if the mines are notopen pit.In the 1950s, a significant number of American uranium miners wereNavajo,as many uranium deposits were discovered on Navajoreservations.A statistically significant subset of these miners later developedsmall-cell lung cancer,a type of cancer usually not associated with smoking, after exposure to uranium ore andradon-222,a natural decay product of uranium.[15]The radon, which is produced by the uranium, and not the uranium itself has been shown to be the cancer causing agent.[16]Some survivors and their descendants received compensation under theRadiation Exposure Compensation Actin 1990.

Currently the level of radon in the air of mines is normally controlled bylaw.In a working mine, the radon level can be controlled byventilation,sealing off old workings and controlling the water in the mine. The level in a mine can go up when a mine is abandoned, it can reach a level which is able to cause theskinto becomered(a mildradiation burn). The radon levels in some of the mines can reach 400 to 700 kBq m−3.[17]

A common unit of exposure of lung tissue toalpha emittersis theworking levelmonth (WLM), this is where the humanlungshave been exposed for 170 hours (a typical month worth of work for a miner) to air which has 3.7 kBq of222Rn (in equilibrium with its decay products). This is air which has the alpha dose rate of 1working level(WL). It is estimated that the average person (general public) is subject to 0.2 WLM per year, which works out at about 15 to 20 WLM in a lifetime. According to the NRC 1 WLM is a 5 to 10 mSv lung dose (0.5 to 1.0rem), while theOrganisation for Economic Co-operation and Development(OECD) consider that 1 WLM is equal to a lung dose of 5.5 mSv, theInternational Commission on Radiological Protection(ICRP) consider 1 WLM to be a 5 mSv lung dose for professional workers (and 4 mSv lung dose for the general public). Lastly theUnited Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) consider that the exposure of the lungs to 1 Bq of222Rn (in equilibrium with its decay products) for one year will cause a dose of 61 μSv.[18]

In humans a relationship betweenlung cancerand radon has been shown to exist (beyond all reasonable doubt) for exposures of 100 WLM and above. By using the data from several studies it has been possible to show that an increased risk can be caused by a dose as low as 15 to 20 WLM. Sadly these studies have been difficult as the random errors in the data are very large. It is likely that the miners are also subject to other effects which can harm their lungs while at work (for example dust anddieselfumes).[citation needed]

In houses[edit]

The fact that radon is present in indoor air has been known since at least the 1950s and research into its effects on human health started in the early 1970s.[19]The danger of radon exposure indwellingsreceived more widespread public awareness after 1984, as a result of a case ofStanley Watras,an employee at theLimerick nuclear power plantinPennsylvania.[20]Mr. Watras set off theradiationalarms (seeGeiger counter) on his wayintowork for two weeks straight while authorities searched for the source of thecontamination.They were shocked to find that the source was astonishingly high levels of radon in hisbasementand it was not related to the nuclear plant. The risks associated with living in his house were estimated to be equivalent tosmoking135 packs ofcigarettesevery day.[21]

Depending how houses are built and ventilated, radon may accumulate in basements and dwellings. TheEuropean Unionrecommends thatmitigationshould be taken starting from concentrations of 400Bq/m3for old houses, and 200 Bq/m3for new ones.[22]

TheNational Council on Radiation Protection and Measurements(NCRP) recommends action for any house with a concentration higher than 8pCi/L (300 Bq/m3).

TheUnited States Environmental Protection Agencyrecommends action for any house with a concentration higher than 148 Bq/m3(given as 4pCi/L). Nearly one in 15 homes in the U.S. has a high level of indoor radon according to their statistics. The U.S. Surgeon General and EPA recommend all homes be tested for radon. Since 1985, millions of homes have been tested for radon in the U.S.[22]

By adding a crawl space under the ground floor, which is subject to forced ventilation the radon level in the house can be lowered.[23]

References[edit]

  1. ^Darby; et al. (January 29, 2005)."Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies".British Medical Journal.330(7485): 223.doi:10.1136/bmj.38308.477650.63.PMC546066.PMID15613366.
  2. ^Kirby et al. p. 3
  3. ^abKeith, S; et al. (May 2012).Toxicological Profile for Radon.Atlanta (GA): Agency for Toxic Substances and Disease Registry (US).
  4. ^"EPA REGION 2, Congressional District(s): 10, Essex, City of Orange"(PDF).New Jersey: U.S. Radium Corp. February 5, 2010. EPA ID#: NJD980654172. Archived fromthe original(PDF)on July 14, 2012.
  5. ^Vanchieri, Cori (November 7, 1990). "Radiation Therapy Pursuit Leads to Unearthing of" Hot Bones "".Journal of the National Cancer Institute.82(21): 1667.doi:10.1093/jnci/82.21.1667.
  6. ^Porstendörfer, J.; et al. (September 1994). "Daily variation of the radon concentration indoors and outdoors and the influence of meteorological parameters".Health Physics.67(3): 283–287.doi:10.1097/00004032-199409000-00011.PMID8056597.
  7. ^Bartoli, G.; et al. (1989). "Evaluation of the exposure levels to radioactivity in the hot-spring environment of the Island of Ischia during a year".Annali di Igiene: Medicina Preventiva e di Comunità.1(6): 1781–1823.PMID2484503.
  8. ^"Predicted median annual-average living-area concentration, by county".Lawrence Berkeley National Laboratory. Archived fromthe originalon 2007-12-31.Retrieved2008-02-12.
  9. ^Yamamoto, Masayoshi; et al. (September 21, 2005). "Seasonal and spatial variation of atmospheric 210Pb and 7Be deposition: features of the Japan Sea side of Japan".Journal of Environmental Radioactivity.86(1): 110–131.doi:10.1016/j.jenvrad.2005.08.001.PMID16181712.
  10. ^"Basic Information about Radon in Drinking Water".United States Environmental Protection Agency. June 30, 2014. Archived fromthe originalon 2015-02-14.RetrievedJanuary 31,2015.
  11. ^Yamazawa, H.; M. Matsuda; J. Moriizumi; T. Iida (2008).Wet Deposition of Radon Decay Products and its Relation with Long-Range Transported Radon.The Natural Radiation Environment. Vol. 1034. pp. 149–152.Bibcode:2008AIPC.1034..149Y.doi:10.1063/1.2991194.
  12. ^Greenfield, M.B.; A. Iwata; N. Ito; M. Ishigaki; K. Kubo (2006).Intense γ radiation from radon progeny accreted in/on rain during and following thunderstorms.Bulletin of the American Physical Society. Nashville, Tennessee.
  13. ^Greenfield, M. B.; N. Ito; A. Iwata; K. Kubo; M. Ishigaki; K. Komura (2008)."Determination of rain age via γ rays from accreted radon progeny".Journal of Applied Physics.104(7): 074912–074912–9.Bibcode:2008JAP...104g4912G.doi:10.1063/1.2990773.hdl:2297/14438.ISSN0021-8979.S2CID122604767.074912. Archived fromthe originalon 2013-02-23.Retrieved2011-08-23.
  14. ^"Survey & Identification of NORM Contaminated Equipment"(PDF).Enprotec / Hibbs & Todd. October 2004. Archived fromthe original(PDF)on 2006-02-20.Retrieved2006-05-28.
  15. ^Gottlieb, Leon S.; Husen, Luverne A. (April 1982). "Lung Cancer Among Navajo Uranium Miners".Chest.81(4): 449–452.doi:10.1378/chest.81.4.449.PMID6279361.
  16. ^Harley, Naomi; Foulkes, Ernest; Hilborne, Lee H.; Hudson, Arlene; Anthony, C. Ross (1999)."A Review of the Scientific Literature As It Pertains to Gulf War Illnesses: Volume 7: Depleted Uranium".RAND Corp. p. 28.
  17. ^Denman, A.R.; Eatough, J.P.; Gillmore, G.; Phillips, P.S. (December 2003). "Assessment of health risks to skin and lung of elevated radon levels in abandoned mines".Health Physics.85(6): 733–739.doi:10.1097/00004032-200312000-00018.PMID14626324.S2CID12197510.
  18. ^Hala, Jiri; Navratil, James (2003).Radioactivity, Ionizing Radiation, and Nuclear Energy.Konvoj.ISBN9788073020538.
  19. ^"Man-made Mineral Fibres and Radon".IARC Monographs on the Evaluation of Carcinogenic Risks to Humans(43). 1988.ISBN9789283212430.RetrievedJanuary 31,2015.
  20. ^Samet, J. M. (January 1992)."Indoor radon and lung cancer. Estimating the risks".Western Journal of Medicine.156(1): 25–29.PMC1003141.PMID1734594.
  21. ^"The Radon Story".The Radon Council. 2001. Archived fromthe originalon February 1, 2015.RetrievedJanuary 1,2015.
  22. ^abBoyd, David R. (2006)."Radon The Unfamiliar Killer".Healthy Environment, Healthy Canadians Series, Report No.1. Vancouver: David Suzuki Foundation.RetrievedFebruary 1,2015.{{cite journal}}:Cite journal requires|journal=(help)
  23. ^Roessler, C. E.; et al. (1996).Design and Testing of Sub-Slab Depressurization for Radon Mitigation in North Florida Houses: Part I - Performance and Durability(PDF).Research Triangle Park, NC: United States Environmental Protection Agency.
  • G.K. Gillmore, P. Phillips, A. Denman, M Sperrin and G. Pearse,Ecotoxicology and Environmental Safety,2001,49,281.
  • J.H. Lubin and J.D. Boice,Journal Natl. Cancer Inst.,1997,89,49. (Risks of indoor radon)
  • N.M. Hurley and J.H. Hurley,Environment International,1986,12,39. (Lung cancer in uranium miners as a function of radon exposure).

Further reading[edit]

  • Hala, J. and Navratil J.D.,Radioactivity, Ionizing Radiation and Nuclear Energy,Konvoj, 2003.ISBN80-7302-053-X
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