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PubMed1992

Site characterization for radon supply potential: a progress review.

"Radon-resistant" house foundations were developed by 1981, but additional construction costs made it undesirable to require them unless necessary. The survey methods used then were labor-intensive and cost so much that it was impractical to identify "radon-prone" areas by nationwide surveys. A cheaper method was required to show where radon-resistant foundations were needed. Information available in 1981 suggested that unusual soil conditions were needed to produce high radon concentrations in houses. If these conditions could be identified, elevated radon concentration levels could be predicted from soil measurements at a lower cost than a radon-in-housing survey. Recent radon surveys show that near-surface bedrock or clay soils, which cover most of the continent, are radon-prone. The measurement methods cannot be used in these soils. The cost of radon surveys has been greatly reduced over the past 10 y. Radon-prone areas can now be identified by radon surveys at a lower cost than soil measurements, and the cost of radon-resistant foundations has been reduced. These developments have removed most of the financial incentive for developing soil-based site classification methods. The priority task now is to encourage the adoption of radon-resistant foundations in radon-prone areas.

Air Pollutants, Radioactive↗
PubMed2001

Quality control of mitigation methods for unusually high indoor radon concentrations.

The present study's objective was to control the quality of different mitigation methods for unusually high indoor radon (222Rn) concentrations of up to 274,000 Bq m(-3) in a village (Umhausen, 2,600 inhabitants) in western Tyrol, Austria. Five years after mitigation, five different remedial actions were examined on their quality by means of measuring indoor radon concentrations with charcoal liquid scintillation radon detectors and with a continuously recording AlphaGuard detector. Mitigation method in house 1--a mechanical intake and outlet ventilation system with heat exchanger in the basement, combined with a soil depressurization system--was characterized by long-term stability. With most favorable air pressure (+100 Pa) in the basement, mean basement radon concentrations in the winter were reduced from 200,000 Bq m(-3) to 3,000 Bq m(-3) by this method 5 y after mitigation. Acting against experts' instructions, the inhabitants had switched off the ventilation system most of the time to minimize power consumption although it had been proven that ventilation reduced mean basement radon concentration by a factor of about 3 in the winter and about 15 in the summer. Mitigation method in house 2-soil depressurization with two fans and loops of drainage tubes to withdraw radon from the region below the floor and outside the basement walls, and from soil below that part of the house with no basement-had been the most successful remedial measure until the winter of 1999 (i.e., 6 y after mitigation), when micro-cracks opened and consequently mean basement radon concentration increased from 250 Bq m(-3) to 1,500 Bq m(-3). Measures to block these microcracks and to minimize soil drying are being developed. Five years after mitigation, the remedial method used in house 3--a multilayer floor construction, where a fan was used to suck radon from a layer between bottom slab and floor-reduced winter mean radon concentration from 25,000 Bq m(-3) to 1,200 Bq m(-3), with the ventilation on and the basement door open. Mitigation method in house 4--a basement sealing technique--was unsuccessful with almost identical radon concentrations during all the five years since mitigation had started. Mitigation method in house 5--a waterproof basement technique especially for future homes--reduced mean basement radon concentration below 300 Bq m(-3) and mean ground floor radon concentration below 200 Bq m(-3), which is the Austrian action level for newly constructed buildings. These findings indicate that even in areas with extremely high radon concentrations, effective mitigation of indoor radon can be achieved provided that house-specific long-term, stable mitigation techniques are applied.

Air Pollution, Indoor↗
PubMed2005

Final results of the Austrian Radon Project.

The Austrian Radon Project started in 1992 and ended in 2001. The Austrian Radon Project had two aims: firstly, finding areas of enhanced indoor radon concentration for future radon mitigations, and, secondly, defining areas with elevated radon risk where radon safe construction is necessary for new houses. The project was based on systematic indoor measurements in randomly selected houses using different types of detectors. Successful intercomparison tests were made in a radon chamber, but simultaneous measurements by different detectors normally used in homes deviated sometimes up to a factor of two. We have to assume that this results from manipulations of the detectors by the inhabitants. The mean radon concentration in Austrian homes was found to be 99 Bq m(-3). A radon potential was derived from the results of the measurements and the information received from questionnaires. This radon potential was defined as an expected radon concentration in a standard situation and characterizes the radon risk from ground sources with all the influences of different living situations eliminated. A mean radon potential was computed for every municipality and the information is displayed as a map. The uncertainty and the reliability of the classification of municipalities according to the radon potential are discussed in more detail and compared with results from Switzerland.

Air Pollutants, Radioactive↗
PubMed2005

Numerical simulations of radon as an in situ partitioning tracer for quantifying NAPL contamination using push-pull tests.

Presented here is a reanalysis of results previously presented by [Davis, B.M., Istok, J.D., Semprini, L., 2002. Push-pull partitioning tracer tests using radon-222 to quantify non-aqueous phase liquid contamination. J. Contam. Hydrol. 58, 129-146] of push-pull tests using radon as a naturally occurring partitioning tracer for evaluating NAPL contamination. In a push-pull test where radon-free water and bromide are injected, the presence of NAPL is manifested in greater dispersion of the radon breakthrough curve (BTC) relative to the bromide BTC during the extraction phase as a result of radon partitioning into the NAPL. Laboratory push-pull tests in a dense or DNAPL-contaminated physical aquifer model (PAM) indicated that the previously used modeling approach resulted in an overestimation of the DNAPL (trichloroethene) saturation (S(n)). The numerical simulations presented here investigated the influence of (1) initial radon concentrations, which vary as a function of S(n), and (2) heterogeneity in S(n) distribution within the radius of influence of the push-pull test. The simulations showed that these factors influence radon BTCs and resulting estimates of S(n). A revised method of interpreting radon BTCs is presented here, which takes into account initial radon concentrations and uses non-normalized radon BTCs. This revised method produces greater radon BTC sensitivity at small values of S(n) and was used to re-analyze the results from the PAM push-pull tests reported by Davis et al. The re-analysis resulted in a more accurate estimate of S(n) (1.8%) compared with the previously estimated value (7.4%). The revised method was then applied to results from a push-pull test conducted in a light or LNAPL-contaminated aquifer at a field site, resulting in a more accurate estimate of S(n) (4.1%) compared with a previously estimated value (13.6%). The revised method improves upon the efficacy of the radon push-pull test to estimate NAPL saturations. A limitation of the revised method is that 'background' radon concentrations from a non-contaminated well in the NAPL-contaminated aquifer are needed to accurately estimate NAPL saturation. The method has potential as a means of monitoring the progress of NAPL remediation.

Computer Simulation↗
PubMed1995

Lung cancer in radon-exposed miners and estimation of risk from indoor exposure.

BACKGROUND: Radioactive radon is an inert gas that can migrate from soils and rocks and accumulate in enclosed areas, such as homes and underground mines. Studies of miners show that exposure to radon decay products causes lung cancer. Consequently, it is of public health interest to estimate accurately the consequences of daily, low-level exposure in homes to this known carcinogen. Epidemiologic studies of residential radon exposure are burdened by an inability to estimate exposure accurately, low total exposure, and subsequent small excess risks. As a result, the studies have been inconclusive to date. Estimates of the hazard posed by residential radon have been based on analyses of data on miners, with recent estimates based on a pooling of four occupational cohort studies of miners, including 360 lung cancer deaths. PURPOSE: To more fully describe the lung cancer risk in radon-exposed miners, we pooled original data from 11 studies of radon-exposed underground miners, conducted a comprehensive analysis, and developed models for estimating radon-associated lung cancer risk. METHODS: We pooled original data from 11 cohort studies of radon-exposed underground miners, including 65,000 men and more than 2700 lung cancer deaths, and fit various relative risk (RR) regression models. RESULTS: The RR relationship for cumulative radon progeny exposure was consistently linear in the range of miner exposures, suggesting that exposures at lower levels, such as in homes, would carry some risk. The exposure-response trend for never-smokers was threefold the trend for smokers, indicating a greater RR for exposure in never-smokers. The RR from exposure diminished with time since the exposure occurred. For equal total exposure, exposures of long duration (and low rate) were more harmful than exposures of short duration (and high rate). CONCLUSIONS: In the miners, about 40% of all lung cancer deaths may be due to radon progeny exposure, 70% of lung cancer deaths in never-smokers, and 39% of lung cancer deaths in smokers. In the United States, 10% of all lung cancer deaths might be due to indoor radon exposure, 11% of lung cancer deaths in smokers, and 30% of lung cancer deaths in never-smokers. This risk model estimates that reducing radon in all homes exceeding the U. S. Environmental Protection Agency's recommended action level may reduce lung cancer deaths about 2%-4%. These estimates should be interpreted with caution, because concomitant exposures of miners to agents such as arsenic or diesel exhaust may modify the radon effect and, when considered together with other differences between homes and mines, might reduce the generalizability of findings in miners.

Adult↗
PubMed1997

Lung cancer risk from residential radon: meta-analysis of eight epidemiologic studies.

BACKGROUND: Studies of underground miners exposed to radioactive radon and its decay products have found that exposure increases risk of lung cancer. Consequently, when radon was found to accumulate in houses, there was concern about the public health impact from exposure to a known carcinogen. Estimates on the basis of studies of underground miners suggest that indoor radon may account for 6000-36,000 lung cancer deaths each year in the United States. Because of differences between working in underground mines and living in houses, estimates are subject to major uncertainties. Numerous case-control studies were launched to assess directly the lung cancer risk from indoor radon. Some studies report positive or weakly positive findings, while others report no increased risk. Thus, the potential hazard from indoor radon remains answered only indirectly through miner studies, experimental animal studies, and cellular studies. PURPOSE: To provide more information on the risk of lung cancer from indoor radon, we conducted a meta-analysis of all case-control studies that included at least 200 case subjects each and that used long-term indoor radon measurements. METHODS: Eight studies were available and included a total of 4263 lung cancer case subjects and 6612 control subjects. From the published results of each study, confounder-adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) for categories of radon concentration were obtained, and weighted linear regression analyses were performed. RESULTS: The combined trend in the RR was significantly different from zero (two-sided P = .03), and an estimated RR of 1.14 (95% CI = 1.0-1.3) at 150 Bq/m3 was found. An influence analysis indicated that no single study dominated the combined results. The exposure-response trend was similar to model-based extrapolations from miners and to RRs computed directly from miners with low cumulative exposures. However, there were significant differences in the study-specific estimates of the exposure response (two-sided P < .001), which were not explained by study differences in percent of the defined exposure interval covered by radon measurements, mean number of residences per subject, and other factors. CONCLUSIONS: Meta-analyses are valuable for identifying differences among studies and for summarizing results, but they should be interpreted cautiously when expected RRs are low as with indoor radon exposure, when there is study heterogeneity and where there is the potential for confounding and exposure misclassification. Nonetheless, the results of this meta-analysis suggest that the risk from indoor radon is not likely to be markedly greater than that predicted from miners and indicate that the negative exposure response reported in some ecologic studies is likely due to model misspecification or uncontrolled confounding and can be rejected. IMPLICATIONS: Until ongoing case-control studies of indoor radon are completed and the data are pooled and analyzed, the studies of underground miners remain the best source of data to use to assess risk from indoor radon. This meta-analysis provides support for their general validity.

Air Pollution, Indoor↗
PubMed1994

Radon and health--an update.

BACKGROUND: The National Radiological Protection Board (NRPB) estimated in 1990 that radon causes 5 per cent of lung cancer in the United Kingdom. The estimate was not based on direct evidence. Since then a number of epidemiological studies have been reported. In addition, various policies have been formulated and some implemented, including the mounting of public campaigns to reduce radon in houses in parts of the United Kingdom. METHODS: A review of the scientific literature, policy documents and results of the campaigns has been undertaken. RESULTS: New data on miners support previous evidence that radon, at the levels found in mines, does cause lung cancer. The one study to add to the two previous case control studies looking at domestic radon tips the scales slightly towards radon being incriminated in homes as well. The effect of smoking, a multiplicative or additive risk with radon, is still unclear. Radon can be calculated to cause up to 383 lung cancer deaths per year in the five currently designated 'radon affected' areas. Approximately 287 of these deaths will be in cigarette smokers, and the most effective way for smokers exposed to radon to reduce their lung cancer risk is to stop smoking. CONCLUSION: Evidence of the risk from residential radon is still insufficient to justify the current NRPB advice. If it were, a much more effective radon campaign would be needed. Such a campaign would concentrate on reducing lung cancer in people by tackling both radon exposure and cigarette smoking, rather than simply reducing radon in houses.

Cohort Studies↗
PubMed1998

Indoor radon.

The naturally radioactive but chemically inert gas, radon, is formed from the radioactive decay of radium which is part of the uranium series. Radon gas, which has a half life of 3.8 days, must escape from soil particles through air-filled pores in order to enter the atmosphere following the decay of radium. The concentration of radon in the atmosphere varies, depending on the place, time, height above the ground and meteorological conditions. It is thus an inescapable source of radiation exposure, both at home and at work. The potential hazards posed by exposure to radiation from indoor radon gas and its daughter products are of great concern worldwide. Noting of an excessive lung cancer risk among several groups of underground miners exposed to radon and its daughter products, studies on radon concentrations in the workplace and in dwellings have been conducted in many countries. The results have shown that the distribution of radon concentrations are approximately lognormal from which population weighted; the arithmetic mean of radon concentration of 40 Bq.m-3 has been adopted worldwide for dwellings and workplaces. The principal methods for reducing a high indoor radon concentration are: reducing the radon supply by reversing the pressure difference between the building and the soil; raising the resistance of the foundations to soil gas entry; removing the radon sources such as water or underlying soil; diluting the concentration by increasing the ventilation rate; and reducing the concentration of radon progeny by filtering and increasing the circulation of indoor air. Buildings which have a radon concentration higher than 200 Bq.m-3 should be investigated by the national authorities concerned; meanwhile, householders should be advised to take simple temporary precautions, such as increasing ventilation, until a permanent remedy can be effected.

Air Pollution, Indoor↗
PubMed1987

Radiation doses from radon in buildings.

Not until about 1970 was it possible to estimate the magnitude of the correlation between additional lung cancer frequency and radon daughter exposure in miners. In addition, it has been realised that high levels of radon daughters in homes may be found in all countries and therefore the interest in radon in buildings has rapidly increased during the last 10 years. Radon gas enters the house from underground, from building materials and in some cases from tap water. Indoor radon daughter concentrations vary between countries and regions. The absorbed dose in the basal cells of the bronchial epithelium based on an average of the population in Canada, U.S.A. and West Germany can be estimated to be about 1 mGy a-1 (average radon daughter concentration about 25 Bq m-3) for Great Britain about half of that value and for the Nordic countries about double this value. 300-3000 lung cancer cases (most probable 1100) may occur in the future in the Swedish population of 8.4 million from radon daughter exposure indoors today. This estimation is made by the National Institute of Radiation Protection. A lower estimate of 100-1000 lung cancer cases is made by the Swedish Cancer Committee. Efforts to decrease the exposure from radon daughters indoors have been made in some countries by establishing limits or recommendations for the radon or radon daughter concentration indoors. Measuring methods for finding houses with high radon daughter concentrations and effective building techniques in order to decrease the radon daughter concentrations in both existing and for planned buildings are available.

Air Pollutants↗
PubMed1991

Dose to red bone marrow from natural radon and thoron exposure.

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about 16 times that in tissue. The mean dose equivalent muSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 microns, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly, the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miner and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq/m3 and an equilibrium equivalent thoron concentration of 0.3 Bq/m3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 muSv, respectively. For a 10-year-old child, the radon and thoron derived annual dose are 70 and 40 muSv, and for a 40-year-old adult 90 and 30 muSv, respectively. The above values exhibit wide range limits due principally to uncertainties in the accumulation of 210Pb in bone, and 210Po in marrow. These data indicate that at the average UK exposure, the alpha-particle dose to active marrow is dominated by that derived from inhaled radon and thoron compared with dietary intake. In infants the dose is dominated by thoron daughters. At the UK radon Action Limit of 200 Bq/m3, the radon and associated thoron derived dose is similar to that from all low LET sources. This work shows that the dose to red bone marrow from radon and thoron is significant, and that the possibility of leukaemia induced by these radiation sources warrants further investigation.

Adipose Tissue↗
PubMed1999

Intercomparison of retrospective radon detectors.

We performed both a laboratory and a field intercomparison of two novel glass-based retrospective radon detectors previously used in major radon case-control studies performed in Missouri and Iowa. The new detectors estimate retrospective residential radon exposure from the accumulation of a long-lived radon decay product, (210)Pb, in glass. The detectors use track registration material in direct contact with glass surfaces to measure the alpha-emission of a (210)Pb-decay product, (210)Po. The detector's track density generation rate (tracks per square centimeter per hour) is proportional to the surface alpha-activity. In the absence of other strong sources of alpha-emission in the glass, the implanted surface alpha-activity should be proportional to the accumulated (210)Po, and hence to the cumulative radon gas exposure. The goals of the intercomparison were to a) perform collocated measurements using two different glass-based retrospective radon detectors in a controlled laboratory environment to compare their relative response to implanted polonium in the absence of environmental variation, b) perform collocated measurements using two different retrospective radon progeny detectors in a variety of residential settings to compare their detection of glass-implanted polonium activities, and c) examine the correlation between track density rates and contemporary radon gas concentrations. The laboratory results suggested that the materials and methods used by the studies produced similar track densities in detectors exposed to the same implanted (210)Po activity. The field phase of the intercomparison found excellent agreement between the track density rates for the two types of retrospective detectors. The correlation between the track density rates and direct contemporary radon concentration measurements was relatively high, considering that no adjustments were performed to account for either the residential depositional environment or glass surface type. Preliminary comparisons of the models used to translate track rate densities to average long-term radon concentrations differ between the two studies. Further calibration of the retrospective detectors' models for interpretation of track rate density may allow the pooling of studies that use glass-based retrospective radon detectors to determine historic residential radon exposures.

Carcinogens, Environmental↗
PubMed2001

Mapping the geogenic radon potential in Germany.

Mapping the geogenic radon potential in Germany is a research project initiated by the German Federal Ministry for the Environment, Conservation and Reactor Safety. The project was aimed to develop a standard methodology for the estimation of a geogenic radon potential and to apply this method to map the region of Germany as an overview for planning purposes. The regionalisation results from a distance-weighted interpolation of the site-specific values of radon concentration in soil gas and in situ gas permeability of soils on a regular grid considering the corresponding geological units. The map of Germany in a scale of 1:2 million is based on the radon concentration in soil gas as an estimator of the geogenic radon potential assuming the 'worst case' of uniform highest permeability. The distribution is subdivided into categories of low (< 10 kBq/m3), medium (10-100 kBq/m3), increased (100-500 kBq/m3) and high (> 500 kBq/m3) radon concentration. High values occur especially in regions with granites and basement rocks of Paleozoic age, and are proven by measurements in 0.03% of the total area. Many of these regions are also known for their enhanced indoor values. The class with increased values takes a portion of 7.86% and likewise occurs mainly in regions with outcrops of folded and metamorphic basement, but also of some Meso- and Cenozoic sediments with increased uranium contents and/or higher emanation coefficients. For 67.3% of the country, the radon concentration is classified as 'medium', and an assignment to specific geological units cannot be made at the map scale considered. Low radon contents, where protective measures against radon are usually not considered, are found in the geologically rather homogeneous part of northern Germany with unconsolidated Cenozoic sediments, covering approximately 25% of the total country. It is of course not possible to predict the indoor radon concentration of single houses from these maps, because construction type and structural fabric of houses are essentially governing the extent to which subsoil radon potential affects the indoor concentration. Besides this, in places with site-specific geochemical, structural and soil-physical properties, local radon anomalies may occur which were not recorded in the course of the wide-meshed screening study.

Air Pollutants, Radioactive↗
PubMed2003

Spatial indoor radon distribution in Mexico City.

We present a spatial analysis of residential radon concentrations in the Mexico City Metropolitan Area, which we intend to use to assign radon exposure in an ongoing case-control study. As part of a probabilistic household survey, carried out between May and June 1999, 501 dwellings were selected for indoor placement of solid state nuclear track detectors (LR 115) in a cup array over a period of approximately 90 days. As part of the sampling design, the city was grid partitioned into nine zones and a sample of dwellings was selected in each zone. All zones were simultaneously surveyed. The stratified sampling design allowed us to obtain radon geometric means, adjusted for household characteristics, week of detector placement and number of days of measurement for these zones. Additionally, adjusted geometric means were estimated for the 100 census tracts surveyed and this information was used to obtain a more detailed spatial distribution of residential radon levels through kriging interpolation and surface contouring. Radon levels depended on the room of placement, the floor level and the ventilation habits but not on building materials. Regarding the city zone, the highest adjusted geometric mean was found in the southwest (136 Bqm(-3)), where 46% of the households had an estimated radon level in excess of 200 Bqm(-3). In the rest of the city, the geometric mean concentration ranged between 41 and 98 Bqm(-3). A more detailed spatial distribution showed that, in general, most of the eastern and middle zones of the city had estimated radon geometric means below 74 Bqm(-3), while the western ones had geometric means above this concentration. Very high geometric means, exceeding 111 Bqm(-3) and even reaching 288 Bqm(-3), are estimated for some areas located in the southern and western zones of Mexico City. The obtained spatial distribution shows that the areas with very high estimated residential radon concentrations are close to inactive volcanic mountains. We believe that the geo-statistical techniques, we have used, offer reasonably good estimates of the average spatial residential radon distribution in Mexico City under average ventilation in homes. The use of this indirect approach for radon exposure measurement in epidemiological studies is an inexpensive alternative to direct radon exposure measurement but may be subject to non-differential misclassification error. The effect of such error on the detection of a real increase in lung cancer risk from indoor radon remains to be determined.

Air Pollution, Indoor↗
PubMed1996

Genetic, cytogenetic, and carcinogenic effects of radon: a review.

Radon exposure has been linked to lung carcinogenesis in both human and animal studies. Studies of smoking and nonsmoking uranium miners indicate that radon alone is a risk factor for lung cancer at the levels encountered by these miners, although the possibility exists that other substances in the mine environment affect the radon-induced response. The relevance of data from mines to the lower-exposure home environment is often questioned; still, a recent study of miners exposed to relatively low radon concentrations demonstrated a statistically significant increase for lung and laryngeal cancer deaths. In two major series of experiments with rats, the primary carcinogenic effect found was respiratory tract tumors, and evidence for an inverse exposure-rate effect was also noted. Although this inverse dose-rate effect also has been described in underground miner studies, it may not similarly apply to radon in the home environment. This observation is due to the fact that, below a certain exposure, cells are hit once or not at all, and one would not expect any dose-rate effect, either normal or inverse. Because some chromosome aberrations persist in cycling cells as stable events, cytogenetic studies with radon are being performed to help complete the understanding of the events leading to radon-induced neoplasia. Radon has been found to induce 13 times as much cytogenetic damage (as measured by the occurrence of micronuclei) than a similar dose of 60Co. A wide variety of mutation systems have demonstrated alpha-particle mutagenesis; recent investigations have focused on the molecular basis of alpha-induced mutagenesis. Gene mutations are induced by radon in a linear and dose-dependent fashion, and with a high biological effect relative to low-LET irradiation. Studies of the hprt locus show that approximately half of the alpha-induced mutations arise by complete deletion of the gene; the remaining mutations are split between partial deletions, rearrangements, and events not detectable by Southern blot or PCR exon analysis. Although other mutation systems do not show the same spectra as observed in the hprt gene (suggesting that the gene environment affects response), DNA deletions or multilocus lesions of various size appear to be predominant after radon exposure. As data emerge regarding radon-induced changes at the chromosomal and molecular level, the mechanisms involved in radon carcinogenesis are being clarified. This information should increase the understanding of risk at the low exposure levels typically found in the home.

Animals↗
PubMed1998

Risk of lung cancer associated with residential radon exposure in south-west England: a case-control study.

Studies of underground miners occupationally exposed to radon have consistently demonstrated an increased risk of lung cancer in both smokers and non-smokers. Radon exposure also occurs elsewhere, especially in houses, and estimates based on the findings for miners suggest that residential radon is responsible for about one in 20 lung cancers in the UK, most being caused in combination with smoking. These calculations depend, however, on several assumptions and more direct evidence on the magnitude of the risk is needed. To obtain such evidence, a case-control study was carried out in south-west England in which 982 subjects with lung cancer and 3185 control subjects were interviewed. In addition, radon concentrations were measured at the addresses at which subjects had lived during the 30-year period ending 5 years before the interview. Lung cancer risk was examined in relation to residential radon concentration after taking into account the length of time that subjects had lived at each address and adjusting for age, sex, smoking status, county of residence and social class. The relative risk of lung cancer increased by 0.08 (95% CI -0.03, 0.20) per 100 Bq m(-3) increase in the observed time-weighted residential radon concentration. When the analysis was restricted to the 484 subjects with lung cancer and the 1637 control subjects with radon measurements available for the entire 30-year period of interest, the corresponding increase was somewhat higher at 0.14 per 100 Bq m(-3) (95% CI 0.01, 0.29), although the difference between this group and the remaining subjects was not statistically significant. When the analysis was repeated taking into account uncertainties in the assessment of radon exposure, the estimated increases in relative risk per 100 Bq m(-3) were larger, at 0.12 (95% CI -0.05, 0.33) when all subjects were included and 0.24 (95% CI -0.01, 0.56) when limited to subjects with radon measurements available for all 30 years. These results are consistent with those from studies of residential radon carried out in other countries in which data on individual subjects have been collected. The combined evidence suggests that the risk of lung cancer associated with residential radon exposure is about the size that has been postulated on the basis of the studies of miners exposed to radon.

Aged↗
PubMed2002

Residential radon exposure and lung cancer: variation in risk estimates using alternative exposure scenarios.

The most direct way to derive risk estimates for residential radon progeny exposure is through epidemiologic studies that examine the association between residential radon exposure and lung cancer. However, the National Research Council concluded that the inconsistency among prior residential radon case-control studies was largely a consequence of errors in radon dosimetry. This paper examines the impact of applying various epidemiologic dosimetry models for radon exposure assessment using a common data set from the Iowa Radon Lung Cancer Study (IRLCS). The IRLCS uniquely combined enhanced dosimetric techniques, individual mobility assessment, and expert histologic review to examine the relationship between cumulative radon exposure, smoking, and lung cancer. The a priori defined IRLCS radon-exposure model produced higher odds ratios than those methodologies that did not link the subject's retrospective mobility with multiple, spatially diverse radon concentrations. In addition, the smallest measurement errors were noted for the IRLCS exposure model. Risk estimates based solely on basement radon measurements generally exhibited the lowest risk estimates and the greatest measurement error. The findings indicate that the power of an epidemiologic study to detect an excess risk from residential radon exposure is enhanced by linking spatially disparate radon concentrations with the subject's retrospective mobility.

Air Pollutants, Radioactive↗
PubMed1994

Residential radon exposure and lung cancer among nonsmoking women.

BACKGROUND: Radon at sufficiently high concentrations is known to cause lung cancer among underground miners and in experimental laboratory animals. PURPOSE: Our aim was to determine whether indoor levels of radon are associated with a detectable increase in lung cancer. Nonsmoking women were selected because they offer the best opportunity to detect radon-related risk while minimizing the potentially confounding influences of cigarette smoking and occupation. METHODS: A population-based, case-control study of incident lung cancer was conducted in Missouri. A total of 538 non-smoking white women diagnosed with lung cancer between 1986 and 1992 and 1183 age-matched control subjects were identified from the Missouri Cancer Registry and from driver's license and Medicare listings, respectively. Information on lung cancer risk factors was obtained by telephone interview. Year-long radon measurements were sought in every dwelling occupied for the previous 5-30 years. RESULTS: Radon measurements covered 78% of the relevant residential period, and women reported being indoors for 84% of this time. The time-weighted average radon concentrations were exactly the same for case subjects and control subjects (1.82 pCi/L of air [pCi L-1]). Radon levels greater than 4 pCi L-1 were experienced by 6.5% of the case subjects and 6.8% of the control subjects. For all data combined, there was little evidence for a trend of lung cancer with increasing radon concentrations (two-tailed trend test, P = .99 continuous data analysis; P = .19 categorical data analysis). A positive dose-response trend was suggested for the adenocarcinoma cell type and among directly interviewed women (two-tailed trend test; P = .31 continuous data analysis; P = .04 categorical data analysis), but not for other histologies or among those who had surrogate interviews. CONCLUSIONS: The possibility of detecting a risk from indoor radon in this study was maximized by (a) including a large number of nonsmoking women with high indoor occupancy, (b) conducting a large number of radon measurements near the time of the diagnosis of cancer, and (c) controlling for known causes of lung cancer. However, an association between lung cancer and the exposure to domestic levels of radon was not convincingly demonstrated. IMPLICATIONS: The magnitude of the lung cancer risk from radon levels commonly found in U.S. dwellings appears low.

Adenocarcinoma↗
PubMed1996

Statistical analysis of real-time, environmental radon monitoring results at the Fernald Environmental Management Project.

A comprehensive real-time, environmental radon monitoring program is being conducted at the Fernald Environmental Management Project, where a large quantity of radium-bearing residues have been stored in two covered earth-bermed silos. Statistical analyses of radon measurement results were conducted to determine what impact, if any, radon emitted by the radium bearing materials contained in the silos has on the ambient radon concentration at the Fernald Environmental Management Project site. The distribution that best describes the outdoor radon monitoring data was determined before statistical analyses were conducted. Random effects associated with the selection of radon monitoring locations were accommodated by using nested and nested factorial classification models. The Fernald Environmental Management Project site was divided into four general areas according to their characteristics and functions: 1) the silo area, where the radium-bearing waste is stored; 2) the production/administration area; 3) the perimeter area, or fence-line, of the Fernald Environmental Management Project site; and 4) a background area, located approximately 13 km from the Fernald Environmental Management Project site, representing the naturally-occurring radon concentration. A total of 15 continuous, hourly readout radon monitors were installed in these 4 areas to measure the outdoor radon concentration. Measurement results from each individual monitor were found to be log-normally distributed. A series of contrast tests, which take random effects into account, were performed to compare the radon concentration between different areas of the site. These comparisons demonstrate that the radon concentrations in the production/administration area and the perimeter area are statistically equal to the natural background, whereas the silo area is significantly higher than background. The study also showed that the radon concentration in the silo area was significantly reduced after a sealant barrier was applied to the contents of the silos.

Environmental Monitoring↗