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Radon Gas and Radon Daughters Pose Potential Environmental Hazard

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Radon Gas and Radon Daughters Pose Potential Environmental Hazard @ snm I. @ I W V W bill 1 Polonium-218 and Polonium-214 Radon Progeny Linked to Lung Cancer RADON GAS AND RADON DAUGHTERS POSE POTENTIAL ENVIRONMENTAL HAZARD David R. Brill, MD, chairman of the begun (1). Meanwhile, the media got alpha-emitter, but has a half-life of American College ofNuclear Physi wind of the events and, before long, only 3.8 days. It occurs naturally and cians (ACNP) Committee on Environ radon became a household word, not is part of the decay scheme of urani mentaiRadiation, has beenfollowing only in southeastern Pennsylvania, um-238, whose ultimate daughter is the renewed interest in radonfor the but throughout North America. lead-206. Along the way, numerous past several months. Dr. Brill also ColebrookdaleTownshiplies atop alpha and beta particles are released contributed apreviousarticle on envi a geologic formation known as the from 13 intermediate radionuclides. ronmental radiation to Newsline. The “ReadingProng.―This is a mass of (See the principal decay scheme of the article provided an in-depth look at black shale that parallels the Appa uranium series on pages 1096—1097.) low-level radioactive wastemanage lachian Mountains, beginning south Exposure to radon has been be ment, and waspublished in January east ofReading and running northeast lieved for years to be associated with 1985 when Newsline wasfirst incor past Allentown, Pennsylvania, to an increasedoccurrenceoflungcancer porated into The Journal of Nuclear area north of Trenton, New Jersey. in uranium miners. The carcinogenic Medicine to provide readers with Related rock formations surround it, hazard is not posed by the radon itself, timely information on socioeconomic extending into northern Maryland but by several of its short-lived daugh and governmental issues related to and New Jersey, downstate New York, ters, most notably polonium-2l8 and nuclear medicine. and southwestern Connecticut. polonium-2l4, alpha emitters with Black shale is a sedimentary rock half-lives of3.05 minutes and 1.64 x D uring construction of the that often contains higher-than-average l0@ seconds, respectively. Unlike Limericknuclearpowerplant concentrationsof naturalradioactivity, radon, these agentsare quite reactive. by the Philadelphia Electric including radium-226, the parent of combining readily with other chem Company in 1984, unusually high radon-222 . The source of the radon, icals and adhering to bronchial mu quantities of radioactivity @rediscov obviously, was the bedrock. cosa (2). eredduringroutinebackgroundmon Environmental radon is not limited itoring in the hair of a construction Uranium-238 Decay Scheme to the ReadingProng area.Many engineer, Stanley J. Watras. Detailed Radon is a noble gas, behaving other regions with shale bedrock questioning 1@iledto yield an explana physically, chemically, and biologi show similar tendencies. In addition, tion, but subsequent analysis proved cally like xenon and krypton. It is an (continued on page 1096) that the radioactivity was caused by daughter products ofradon-222. Mon itoring of the man's home in Cole brookdale Township, Berks County, Units of Measure for Radon Gas, Pennsylvania, revealed extraordinarily RadonProgeny,andExposure high levels of radon gas in the base Concentration(pCi/I)radonofpicoCuries per liter ment and kitchen. gasConcentration The Pennsylvania Department of (WL)radon ofworking levels Environmental Resources (PA-DER) progenyExposure was notified and carried out tests in (WLM)radontoworking level months other homes in the neighborhood. progenyCumulative Radon gas, at lower levels, was found yearto exposureworking level months per in a number of homes, but others radon progeny(WLM/y) were not affected at all. Immediate and intensive efforts to correct the 1 WL = 200 pCi/I 1 WLM = 1 WL x 170 hours problem in the involved houses were Volume 28 •Number 7 •July 1987 1095 @ snm Newsline (continued from page 1095) low radioactivity tend to be less than granite and phosphate formations may in more severely affected locations, Principal DecayScheme also have high levels of radioactivity. significant concentrations can some of the UraniumSeries Within the United States (US) and times be found in “low-riskregions.― Canada, such areas include western At this point, no one knows the extent Colorado, central regions of Mon ofthe problem. tana,Maine,Florida,andSaskatche Daughter products can also be wan, to name a few (2). Uranium taken into the food chain (2). Because mining regions of Germany and of their extremely short half-lives, Czechoslovakia, southwestern India, polonium-218 and polonium-2l4 are the northern coast of Brazil , and the not cause for concern in this setting; phosphate mines of the Dead Sea in however, lead-210 and polonium-2l0 Israel also have increased natural can pose a significant risk. Tobacco radioactivity. can concentrate the latter to a level of It is important to realize that release three times background. Estimates as of radon gas is not necessarily pro high as 20 rem/year to focal areas of portionate to the amount of radio bronchial mucosa have been made activity in bedrock. Other factors, from autopsy measurements on such as the porosity of regolith, or smokers (2). Protactinium soil (which may vary by a factor of Although radon itself is of little 234m 106between sand and clay), and the consequence, investigators have docu @nute)@r degreeoffracturinginbedrock(which mentedanassociationbetweenelevated determines the surface available for concentrations of daughter products exhalation of radon) play an extremely and increased rates of bronchogenic important role (3). Perturbation of carcinoma. Epidemiologic studies of the ground by earthquakes or human miners in the US and Europe, as well Uranium234 activities may enhance radon's avail as animal data, suggest a risk that @9jea@' ability to the atmosphere. In addition, increases in proportion to dose (3). the release of radon can vary accord At this point, no studies have been ing to atmospheric conditions. Snow done to measure the rates of occur cover and high barometric pressure, rence in homes with high and low for example, reduce release into air. radon levels. The US Environmental Protection Radon is Ubiquitous Agency (EPA) has used occupational It is also important to realize that and animal studies to estimate risks radon gas is ubiquitous. All soils and from environmental exposure, and to rocks contain some trace of radon develop guidelines. There was little precursors and can release radon (3). other choice, but there are obvious Although average releases in areas of and unavoidable flaws in the method. Radon-222 Polonium-218 Lead-214 Bismuth-214 1.6 x 10@ seconds 1096 The Journal of Nuclear Medicine @:@@jne There are differences in exposure mines and in some homes in the tages and drawbacks (5,6). The most levels and rates between occupation Reading Prong area, a 44% lifetime commonly used are alpha-track de ally and environmentally exposed risk of lätalbronchogenic carcinoma tectors and charcoal cannisters. The populations. Cofactors such as dust as claimed by the EPA (4)—may be former consists of a piece of plastic and very high levels of tobacco con realistic. that is exposed for several months. sumption are found in mines but not in The ambient level of radon and its Alpha particles make miniscule tracks homes (3), although it can be argued daughters in mines or buildings is in the plastic, which become micro that the thick mucus ofchronic bron designated in several ways. Picocuries scopically visible and can be counted chitis may protect the bronchial mu per liter (pCi/I) is a direct measure when the plastic is treated with acid. cosa from alpha particles. Investiga ofradongas.On theaverage,each The charcoalcannistertrapsthe radon, tors of both occupationally exposed home in the US has about 1 pCi/I of which then decays. Some of its progeny populations and experimental ani radon (3). About 8% ofall homes in give off gamma rays, which can be mals have used different methods and the US exceed the 4 pCi/l limit rec counted externally. looked at different parameters, so that ommended by the EPA (4). In places results are sometimes difficult to like Colebrookdale Township, about Problems of Radon Measurements compare. 60% of homes fall above the level. All methods are accurate and re Despite these difficulties, the EPA Radon progeny are measured in producible, but ambient levels of ra felt compelled to develop guidelines “workinglevels―(WL). At equilibri dionuclides are quite variable. Sea with a conservative standard. The um, 1WL = 200 pCi/l of radon. Mr. sonal and diurnal changes can greatly agency recommends that ambient Watras, the construction engineer at influence readings (2,3). Major levels of radon be maintained at 4 the Limerick nuclear power plant, variations from room to room can oc pCi/l or less and, for radon progeny, lived in a house that had 13.5WL (1), cur in one house. Even the placement 0.02 working levels (WL) (4). They the highest environmental level ever ofa detector in different parts of one estimate a lifetime risk for fatal bron measured! Exposure depends on am room can drastically change results. chogenic carcinoma of 2.4—9.0%at bient levels of radioactivity over time, Quality control is extremely im this level (baseline risk is 1%) (1). so the unit ofexposure is the “work portant. Since the public has become Not everyone agrees with the EPA. ing level month―(WLM). The month aware of radon, some homeowners The National Council on Radia is based on an 8-hour/day, 5-day/week have fallen victim to unscrupulous tion Protection and Measurements month, equivalent to 170hours. The companies that make money by per (NCRP) recommends a maximum of' WL and WLM units were developed forming fraudulent measurements. 8 pCi/l ofradon (1—3),and estimates for epidemiologic studies of miners. One operator, forexample, reportedly a 2 % lifetime risk of lethal lung can Finally, cumulative exposure is mea collected samples in a mayonnaise jar cer at this level.
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