Cave radon exposure, dose, dynamics and mitigation

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dc.contributor.authorWaring, CLen_AU
dc.contributor.authorHankin, SIen_AU
dc.contributor.authorSolomon, SBen_AU
dc.contributor.authorLong, Sen_AU
dc.contributor.authorYule, Aen_AU
dc.contributor.authorBlackley, Ren_AU
dc.contributor.authorWerczynski, Sen_AU
dc.contributor.authorBaker, ACen_AU
dc.date.accessioned2022-08-29T03:07:32Zen_AU
dc.date.available2022-08-29T03:07:32Zen_AU
dc.date.issued2021-03en_AU
dc.date.statistics2022-07-26en_AU
dc.description.abstractMany caves around the world have very high concentrations of naturally occurring 222Rn that may vary dramatically with seasonal and diurnal patterns. For most caves with a variable seasonal or diurnal pattern, 222Rn concentration is driven by bi-directional convective ventilation, which responds to external temperature contrast with cave temperature. Cavers and cave workers exposed to high 222Rn have an increased risk of contracting lung cancer. The International Commission on Radiological Protection (ICRP) has re-evaluated its estimates of lung cancer risk from inhalation of radon progeny (ICRP 115) and for cave workers the risk may now (ICRP 137) be 4–6 times higher than previously recognized. Cave Guides working underground in caves with annual average 222Rn activity > 1,000 Bq m⁻3 and default ICRP assumptions (2,000 workplace hours per year, equilibrium factor F ₌ 0.4, dose conversion factor DCF ₌ 14 µSv (kBq h m⁻3)⁻1 could now receive a dose of > 20 mSv y₋1 . Using multiple gas tracers (δ13C-CO2, Rn and N2O), linked weather, source gas flux chambers, and convective air flow measurements a previous study unequivocally identified the external soil above Chifley Cave as the source of cave 222Rn. If the source of 222Rn is external to the cave, a strategy to lower cave 222Rn by passively decreasing summer pattern convective ventilation, which draws 222Rn into caves, is possible without harming the cave environment. A small net annual average temperature difference (warmer cave air) due to geothermal heat flux produces a large net annual volumetric air flow bias (2–5:1) favoring a winter ventilation pattern that flushes Rn from caves with ambient air. Rapid anthropogenic climate change over decades may heat the average annual external temperature relative to the cave temperature that is stabilized by the thermal inertia of the large rock mass. Relative external temperature increases due to climate change (Jenolan Caves, 2008–2018, 0.17°C) reduces the winter pattern air flow bias and increases Rn concentration in caves. © The Authorsen_AU
dc.identifier.citationWaring, C. L., Hankin, S. I., Solomon, S. B., Long, S., Yule, A., Blackley, R., Werczynski, S. & Baker, A. C. (2021). Cave radon exposure, dose, dynamics and mitigation. Journal of Cave & Karst Studies, 83(1), 1-19. doi:10.4311/2019ES0124en_AU
dc.identifier.issn1090-6924en_AU
dc.identifier.issue1en_AU
dc.identifier.journaltitleJournal of Cave & Karst Studiesen_AU
dc.identifier.pagination1-19en_AU
dc.identifier.urihttps://doi.org/10.4311/2019ES0124en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/13643en_AU
dc.identifier.volume83en_AU
dc.language.isoenen_AU
dc.publisherNational Speleological Societyen_AU
dc.subjectCavesen_AU
dc.subjectRadonen_AU
dc.subjectVentilationen_AU
dc.subjectNeoplasmsen_AU
dc.subjectAir flowen_AU
dc.subjectGas flowen_AU
dc.subjectNew South Walesen_AU
dc.subjectAustraliaen_AU
dc.titleCave radon exposure, dose, dynamics and mitigationen_AU
dc.typeJournal Articleen_AU
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