Indoor radon exposure and active and passive smoking in relation to the occurrence of lung cancer

Exposure to indoor radon and radon daughters is currently attracting great interest as a possible cause of lung cancer. This concern is supported by several studies, most of them relatively small in numbers or weak in the assessment of exposure. This study encompasses 177 persons with lung cancer and 677 noncancer referents, all deceased and with 30 years or more of residency in the same house in an area with radon-leaking alum shale deposits in the central part of southern Sweden. Exposure categories based on building material, type of house, and ground conditions were created, but measurements of the indoor radon daughter concentration were also made for 142 cases and 264 referents. Active and passive smoking was ascertained through questionnaires sent to the next-of-kin. Overall, the lung cancer risk was approximately twofold with regard to the categories of assumed radon daughter exposure for the rural sector of the population but not for the same categories of the urban sector, possibly because of less precise exposure assessment and influence from other factors. Occasional and passive smokers, as well as passive smokers alone, had a particularly increased risk of lung cancer in association with the increased exposure categories.     

Residential radon and risk of lung cancer in an Italian alpine area

To evaluate whether residential radon exposure explains the excess mortality for lung cancer in an Italian alpine valley with high natural radioactivity, the authors conducted a population-based case-control study on 138 deceased cases and 291 sex- and year-of-birth-matched controls. Year-long alpha-track measurements of radon were performed in the most recent residence, and information about occupational history and lifetime smoking habits was obtained. The authors adjusted for smoking, and radon was associated with lung cancer risk among men: compared with a radon level of < 40 becquerels (Bq) per cubic meter (m3), the odds ratios for 40-76 Bq/m3, 77-139 Bq/m3, 140-199 Bq/m3, and 200+ Bq/m3 were 2.1, 2.0, 2.7, and 1.4, respectively. The association between radon and lung cancer, as determined with a multiplicative model, was found only among male smokers.     

Residential Radon and Risk of Lung Cancer in an Italian Alpine Area

To evaluate whether residential radon exposure explains the excess mortality for lung cancer in an Italian alpine valley with high natural radioactivity, the authors conducted a population-based case-control study on 138 deceased cases and 291 sex- and year-of-birth-matched controls. Year-long alpha-track measurements of radon were performed in the most recent residence, and information about occupational history and lifetime smoking habits was obtained. The authors adjusted for smoking, and radon was associated with lung cancer risk among men: compared with a radon level of < 40 becquerels (Bq) per cubic meter (m³), the odds ratios for 40–76 Bq/m³, 77–139 Bq/m³, 140–199 Bq/m³, and 200+ Bq/m³ were 2.1, 2.0, 2.7, and 1.4, respectively. The association between radon and lung cancer, as determined with a multiplicative model, was found only among male smokers.     

Residential radon and risk of lung cancer in Eastern Germany

BACKGROUND: There is suggestive evidence that residential radon increases lung cancer risk. To elucidate this association further, we conducted a case-control study in Thuringia and Saxony in Eastern Germany during 1990-1997. METHODS: Histologically confirmed lung cancer patients from hospitals and a random sample of population controls matched on age, sex and geographical area were personally interviewed with respect to residential history, smoking, and other risk factors. One-year radon measurements were performed in houses occupied during the 5-35 years prior to the interview. The final analysis included a total of 1,192 cases and 1,640 controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression. RESULTS: Measurements covered on average 72% of the exposure time window, with mean radon concentrations of 76 Bq/m3 among the cases and 74 Bq/m3 among the controls. The smoking- and asbestos-adjusted ORs for categories of radon (50-80, 80-140 and >140 Bq/m*3, compared with 0-50 Bq/m3) were 0.95 (CI = 0.77 to 1.18), 1.13 (CI = 0.86 to1.50) and 1.30 (CI = 0.88 to 1.93). The excess relative risk per 100 Bq/m? was 0.08 (CI = -0.03 to 0.20) for all subjects and 0.09 (CI = -0.06 to 0.27) for subjects with complete measurements for all 30 years. CONCLUSIONS: Our data indicate a small increase in lung cancer risk as a result of residential radon that is consistent with the findings of previous indoor radon and miner studies.     

Residential radon and lung cancer risk in a high-exposure area of Gansu Province, China

In the general population, evaluation of lung cancer risk from radon in houses is hampered by low levels of exposure and by dosimetric uncertainties due to residential mobility. To address these limitations, the authors conducted a case-control study in a predominantly rural area of China with low mobility and high radon levels. Included were all lung cancer cases diagnosed between January 1994 and April 1998, aged 30-75 years, and residing in two prefectures. Randomly selected, population-based controls were matched on age, sex, and prefecture. Radon detectors were placed in all houses occupied for 2 or more years during the 5-30 years prior to enrollment. Measurements covered 77% of the possible exposure time. Mean radon concentrations were 230.4 Bq/m(3) for cases (n = 768) and 222.2 Bq/m(3) for controls (n = 1,659). Lung cancer risk increased with increasing radon level (p < 0.001). When a linear model was used, the excess odds ratios at 100 Bq/m(3) were 0.19 (95% confidence interval: 0.05, 0.47) for all subjects and 0.31 (95% confidence interval: 0.10, 0.81) for subjects for whom coverage of the exposure interval was 100%. Adjusting for exposure uncertainties increased estimates by 50%. Results support increased lung cancer risks with indoor radon exposures that may equal or exceed extrapolations based on miner data.     

Residential radon and lung cancer among never-smokers in Sweden.

In this study, we attempted to reduce existing uncertainty about the relative risk of lung cancer from residential radon exposure among never-smokers. Comprehensive measurements of domestic radon were performed for 258 never-smoking lung cancer cases and 487 never-smoking controls from five Swedish case-control studies. With additional never-smokers from a previous case-control study of lung cancer and residential radon exposure in Sweden, a total of 436 never-smoking lung cancer cases diagnosed in Sweden between 1980 and 1995 and 1,649 never-smoking controls were included. The relative risks (with 95% confidence intervals in parentheses) of lung cancer in relation to categories of time-weighted average domestic radon concentration during three decades, delimited by cutpoints at 50, 80, and 140 Bq m(-3), were 1.08 (0.8--1.5), 1.18 (0.9--1.6), and 1.44 (1.0--2.1), respectively, with average radon concentrations below 50 Bq m(-3) used as reference category and with adjustment for other risk factors. The data suggested that among never-smokers residential radon exposure may be more harmful for those exposed to environmental tobacco smoke. Overall, an excess relative risk of 10% per 100 Bq m(-3) average radon concentration was estimated, which is similar to the summary effect estimate for all subjects in the main residential radon studies to date.     

Study of lung cancer and residential radon in the Czech Republic

Epidemiological evidence of lung cancer risk from radon is based mainly on studies of men employed underground in mines where exposures are relatively high in comparison to indoor exposure. Risk from residential radon can be estimated from occupational studies. Nevertheless, as such extrapolations depend on a number of assumptions, direct estimation of the risk is needed. The present study of lung cancer mortality was designed as a follow-up of a population (N = 12,004) in a radon prone area of the Czech Republic covering the period 1960-1999. Information on vital status and causes of death were obtained mostly from local authorities and from the national population registry. Exposure estimates were based on one year measurements of radon progeny in most houses of the study area (74%). Exposures outside the area (16%) were based on country radon mapping. Mean concentration of 509 Bq/m3 is higher than the country estimate by a factor of 5. By 1999, a total of 210 lung cancers were observed, somewhat more than the nationally expected number (O/E = 1.10) in comparison to generally low numbers corresponding to cancers other than lung (O/E = 0.81). The excess relative risk per standard radon concentration (100 Bq/m3) was 0.087 (90% CI: 0.017-0.208). This value is consistent with risk coefficients derived in other indoor studies. The present follow-up demonstrated that increased incidence of lung cancer depends linearly on exposure in terms of average radon concentration in the course of previous 5-34 years. Adjustment for smoking did not substantially change this estimate, although the risk coefficient for non-smokers (0.130) was higher in comparison to that for ever smokers (0.069), but not statistically different.     

Indoor radon and lung cancer in France

BACKGROUND: Several case-control studies have indicated an increased risk of lung cancer linked to indoor radon exposure; others have not supported this hypothesis, partly because of a lack of statistical power. As part of a large European project, a hospital-based case-control study was carried out in 4 areas in France with relatively high radon levels. METHODS: Radon concentrations were measured in dwellings that had been occupied by the study subjects during the 5- to 30-year period before the interview. Measurements of radon concentrations were performed during a 6-month period using 2 Kodalpha LR 115 detectors (Dosirad, France), 1 in the living room and 1 in the bedroom. We examined lung cancer risk in relation to indoor radon exposure after adjustment for age, sex, region, cigarette smoking, and occupational exposure. RESULTS: We included in the analysis 486 cases and 984 controls with radon measures in at least 1 dwelling. When lung cancer risk was examined in relation to the time-weighted average radon concentration during the 5- to 30-year period, the estimated relative risks (with 95% confidence intervals) were: 0.85 (0.59-1.22), 1.19 (0.81-1.77), 1.04 (0.64-1.67), and 1.11 (0.59-2.09) for categories 50-100, 100-200, 200-400, and 400+ becquerels per cubic meter (Bq/m), respectively (reference <50 Bq/m). The estimated relative risk per 100 Bq/m was 1.04 (0.99-1.11) for all subjects and 1.07 (1.00-1.14) for subjects with complete measurements. CONCLUSIONS: Our results support the presence of a small excess lung cancer risk associated with indoor radon exposure after precise adjustment on smoking. They are in agreement with results from some other indoor radon case-control studies and with extrapolations from studies of underground miners.     

Residential radon exposure and lung cancer in Swedish women.

A case-control study was undertaken to investigate the role of residential radon exposure for lung cancer. The study included 210 women with lung cancer diagnosed from 1983-1986 in the county of Stockholm and 191 hospital and 209 population controls. Interviews provided information on lifetime residences and smoking. Radon concentrations measured in 1,573 residences of the study subjects showed a lognormal distribution with arithmetic and geometric means of 127.7 and 96.0 Bq m-3, respectively. Lung cancer risks tended to increase with estimated radon exposure, reaching a relative risk of 1.7 (95% confidence interval: 1.0-2.9) in women having an average radon level exceeding 150 Bq m-3 (4 pCi L-1). Stronger associations were suggested in younger persons and risk estimates appeared to be within the same range as those projected for miners. However, further studies are needed to clarify the level of risk associated with exposure to residential radon.     

A case-referent study of lung cancer and incense smoke, smoking, and residential radon in Chinese men

Background: Burning incense generates large amounts of air pollutants, many of which are confirmed or suspected human lung carcinogens.Objectives: We conducted a population-based case-referent study to examine the effect of incense smoke exposure on lung cancer risk among Chinese males and explored the joint effect of cigarette smoking and exposure to residential radon.Methods: We recruited 1,208 male lung cancer incident cases and 1,069 community referents from 2004 to 2006 and estimated their lifetime exposures to incense smoke and other residential indoor air pollutants based on self-reported information collected during interviews. We performed unconditional multivariable logistic regression analysis to estimate the odds ratio (OR) for lung cancer associated with exposure to incense smoke after adjusting for possible confounders. We conducted stratified analyses by smoking status and exposures to incense burning and residential radon and explored the potential additive-scale interactions.Results: We observed an association between incense exposure and lung cancer that was limited primarily to smokers. Cigarette smoking and high cumulative incense exposure at home appeared to have a synergistic effect on lung cancer (compared with never-smokers who never used incense, the OR for lung cancer for smokers who used incense ≥ 60 day-years = 5.00; 95% confidence interval: 3.34, 7.51). Power was limited, but we also found preliminary evidence suggesting that radon exposure may increase risk among smokers using incense.Conclusion: Our study suggests that exposure to incense smoke in the home may increase the risk of lung cancer among smokers and that exposure to radon may further increase risk.     

Canadian individual risks of radon-induced lung cancer for different exposure profiles

BACKGROUND: Indoor radon has been determined to be the second leading cause of lung cancer after tobacco smoking. There is an increasing need among radiation practitioners to have numerical values of lung cancer risks for men and women, ever-smokers and never-smokers exposed to radon in homes. This study evaluates individual risks for the Canadian population exposed to radon in homes at different radon concentrations and for different periods of their lives. METHODS: Based on the risk model developed recently by U.S. Environmental Protection Agency (EPA), individual risks of radon-induced lung cancers are calculated with Canadian age-specific rates for overall and lung cancer mortalities (1996-2000) as well as the Canadian smoking prevalence data in 2002. RESULTS: Convenient tables of lifetime relative risks are constructed for lifetime exposures and short exposures between any two age intervals from 0 to 110, and for various radon concentrations found in homes from 50 to 1000 Bq/m3. CONCLUSIONS: The risk of developing lung cancer from residential radon exposure increases with radon concentration and exposure duration. For short exposure periods, such as 10 or 20 years, risks are higher in middle age groups (30-50) compared especially to the later years. Individuals could lower their risks significantly by reducing radon levels earlier in life. The tables could help radiation protection practitioners to better communicate indoor radon risk to members of the public.     

A cost-effectiveness analysis of lowering residential radon levels in Sweden—Results from a modelling study

PurposeResidential exposure to radon is considered as the second leading cause of lung cancer after smoking. The purpose of this study was to conduct a cost-effectiveness analysis of reducing the indoor radon levels in Sweden from the current reference level of 200 Bq/m³ to the WHO suggested reference level of maximum 100 Bq/m³.MethodsWe constructed a decision-analytic cost-effectiveness model using input data from published literature and administrative records. The model compared the increase in economic costs to the health benefits of lower indoor radon-levels in a Swedish policy context. We estimated the cost per life-year and quality adjusted life year (QALY) gained and assessed the robustness of the results using both deterministic and probabilistic sensitivity analysis.ResultsIncluding (excluding) costs of added life years the cost per QALY for existing homes was €130,000 (€99,000). For new homes the cost per QALY including (excluding) costs of added life years was €39,000 (€25,000).ConclusionsThe results indicate that it is not cost-effective to reduce indoor radon levels from 200 Bq/m³ to a maximum of 100 Bq/m³ in existing homes, whereas it is cost-effective for new homes.     

Effects of radon mitigation vs smoking cessation in reducing radon-related risk of lung cancer.

OBJECTIVES: The purpose of this paper is to provide smokers with information on the relative benefits of mitigating radon and quitting smoking in reducing radon-related lung cancer risk. METHODS: The standard radon risk model, linked with models characterizing residential radon exposure and patterns of moving to new homes, was used to estimate the risk reduction produced by remediating high-radon homes, quitting smoking, or both. RESULTS: Quitting smoking reduces lung cancer risk from radon more than does reduction of radon exposure itself. CONCLUSIONS: Smokers should understand that, in addition to producing other health benefits, quitting smoking dominates strategies to deal with the problem posed by radon.     

Characteristics of the German uranium miners cohort study

To evaluate the risk of cancer associated with low and high levels of radon exposure one of the largest single cohort studies on uranium miners is being conducted in Germany including 58,721 men who were employed for at least 6 mo between 1946 and 1989 at the former Wismut uranium company in Eastern Germany. Information on job history, smoking, dust, and arsenic was collected from the original payrolls and the medical records. Exposure to radon and its progeny was estimated by using a detailed job-exposure matrix. The first mortality follow-up determining the vital status as of 31 December 1998 has been started. The cohort includes 49,342 exposed miners who have worked underground or in processing/milling facilities and 9,379 never-exposed workers. Miners who had been exposed for the first time between 1946 and 1954 (n = 19,865), the years with the poorest working conditions, show higher mean cumulative radon exposures (709 working level months, WLM) and a longer duration of exposure (mean = 13 y) than those with the first exposure between 1955 to 1970 (121 WLM and 11 y, n = 14,155) or after 1970 (10 WLM and 6 y, n = 15,322), respectively. Information on smoking is available for 38% of the cohort, demonstrating that most miners were heavy smokers. In the first mortality follow-up a total of about 15,000 deceased men including about 2,200 lung cancer deaths are expected. The main strengths of the study are its size and the large group of workers having received low exposures over relatively long periods of time.     

The impact of declining smoking on radon-related lung cancer in the United States

Objectives. We examined the effect of current patterns of smoking rates on future radon-related lung cancer.Methods. We combined the model developed by the National Academy of Science''s Committee on Health Risks of Exposure to Radon (the BEIR VI committee) for radon risk assessment with a forecasting model of US adult smoking prevalence to estimate proportional decline in radon-related deaths during the present century with and without mitigation of high-radon houses.Results. By 2025, the reduction in radon mortality from smoking reduction (15 percentage points) will surpass the maximum expected reduction from remediation (12 percentage points).Conclusions. Although still a genuine source of public health concern, radon-induced lung cancer is likely to decline substantially, driven by reductions in smoking rates. Smoking decline will reduce radon deaths more that remediation of high-radon houses, a fact that policymakers should consider as they contemplate the future of cancer control.The Environmental Protection Agency (EPA) estimates that radon in the home is responsible for over 21 000 lung cancer deaths annually among Americans, making radon the major cause of lung cancer after tobacco use. The agency considers radon a major public health problem and, since 1986, has mounted an aggressive campaign urging the public to test their homes for radon and take remedial actions when airborne concentrations of radon exceed 4 picocuries per liter of air (4 pCi/L).¹For its most current risk assessment, the EPA employed the BEIR VI model, developed by the Committee on Health Risks of Exposure to Radon (the BEIR VI committee) of the National Academy of Sciences (NAS).² The BEIR VI model''s calculation of radon-related risk (as was the case for its predecessor, BEIR IV) was estimated from data on miners, who are subject to much higher levels of radon than is the average population and have shown a significant correlation between lung cancer risk and radon exposure. Although the extrapolation of the results from miners to the much less exposed general public initially caused controversy, the BEIR VI implications of risk have been validated by recent case–control studies at the population level.^3–5 The BEIR VI model is thus broadly accepted as a valid predictor of the radon-related risk for typical individuals.The available data suggest a strong interaction effect between radon exposure and smoking status in the determination of lung cancer risk, which means that smokers are at a much higher risk of dying from radon-induced lung cancer than are nonsmokers. This interaction is recognized in the BEIR VI model, which postulates a superadditive (but less than multiplicative) interaction between smoking and radon. To appreciate the magnitude of this interaction, consider the fact that the background lung cancer risk ratio between ever and never smokers is 13 to 1.⁶ A multiplicative interaction between radon and smoking would imply that, at the same level of radon exposure, the ratio of radon-induced excess risk between ever and never smokers would be the same as the ratio of background lung cancer risks between those 2 groups (i.e., 13 to 1). On the other hand, an additive relationship between radon and smoking would imply that radon would add the same extra risk to ever and never smokers exposed to the same dosage, making the excess risks ratio between the 2 groups equal 1 to 1. Using the BEIR VI model, the EPA calculates that, at a radon level of 4 pCi/L, the lifetime risk of radon-induced lung cancer death is 62 per 1000 for ever smokers and 7 per 1000 for never smokers, yielding an excess risk ratio of 8.86 to 1 between the 2 groups.¹ As 8.86 falls between 1 and 13, the BEIR VI model implies that radon adds more risk to ever smokers than to never smokers, but that excess risk is less than proportional to the lung cancer background risk of those 2 groups, suggesting a submultiplicative (but superadditive) relationship between smoking and radon. The BEIR VI model does not distinguish between current and former smokers.Given this implied superadditive interaction, the number of future radon deaths will heavily depend on population smoking rates. As smoking rates in the United States have been falling for several decades and are expected to continue declining, the overall magnitude of the radon death toll is likely to decline as well. The question we try to address is what is the magnitude of this expected decline?We extend the EPA''s analysis by examining the sensitivity of radon-related lung cancer in the United States to future smoking rates. We estimate the proportional decline in the number of lung cancer deaths caused by radon for the period 2006 through 2100, assuming a likely scenario for smoking rates. We do not forecast specific numbers of radon-induced lung cancer deaths because these numbers will depend on many factors likely to change over such a long period of time. Instead, we concentrate on the relative impact of the smoking decline on the overall radon death toll and also examine the benefits of remediating houses with high radon levels given the results of our analysis. Following the EPA''s approach, in our computations, we employ the BEIR VI model, thereby assuming a submultiplicative relationship between smoking and radon. In the remaining sections of the report, we discuss the assumptions, models, and data employed in our analysis, our findings, and the implications of the results for both the magnitude of radon-related risk to the population and the effectiveness of housing remediation in reducing such risk.     

Case-control study on lung cancer and residential radon in western Germany

In a 1990-1996 case-control study in western Germany, the authors investigated lung cancer risk due to exposure to residential radon. Confirmed lung cancer cases from hospitals and a random sample of community controls were interviewed by trained interviewers regarding different risk factors. For 1 year, alpha track detectors were placed in dwellings to measure radon gas concentrations. The evaluation included 1,449 cases and 2,297 controls recruited from the entire study area and a subsample of 365 cases and 595 controls from radon-prone areas of the basic study region. Rate ratios were estimated by using conditional logistic regression adjusted for smoking and for asbestos exposure. In the entire study area, no rate ratios different from 1.0 were found; in the radon-prone areas, the adjusted rate ratios for exposure in the present dwelling were 1.59 (95% confidence interval (CI): 1.08, 2.27), 1.93 (95% CI: 1.19, 3.13), and 1.93 (95% CI: 0.99, 3.77) for 50-80, 80-140, and >140 Bq/m3, respectively, compared with 0-50 Bq/m3. The excess rate ratio for an increase of 100 Bq/m3 was 0.13 (-0.12 to 0.46). An analysis based on cumulative exposure produced similar results. The results provide additional evidence that residential radon is a risk factor for lung cancer, although a risk was detected in radon-prone areas only, not in the entire study area.     

Increased lung cancer risk due to residential radon in a pooled and extended analysis of studies in Germany

Residential radon has been shown to be a risk factor for lung cancer in several studies-but with limited power in each single study. The data of two case-control studies performed during 1990-1997 in Germany and used for previous publications have been extended and pooled. Both studies have identical study designs. In total, data of 2,963 incident lung cancer cases and 4,232 population controls are analyzed here. One-year radon measurements were performed in houses occupied during the 5-35 y prior to the interview. Conditional logistic and linear relative risk regression was used for the analysis. Measurements covered on average 70% of the exposure time window, with an average radon exposure of 61 Bq m(-3). The smoking and asbestos-adjusted ORs were 0.97 [95% confidence interval (CI) 0.85 to 1.11] for 50-80 Bq m(-3), 1.06 (95% CI 0.87 to 1.30) for 80-140 Bq m(-3) and 1.40 (95% CI 1.03 to 1.89) for radon concentrations above 140 Bq m(-3), compared to the reference category <50 Bq m(-3). The linear increase in the odds ratio per 100 Bq m(-3) was 0.10 (95% CI -0.02 to 0.30) for all subjects and 0.14 (95% CI -0.03 to 0.55) for less mobile subjects who lived in only one home in the last 5-35 y. The risk coefficients generally were higher when measurement error in the radon concentrations was reduced by restricting the population. With respect to histopathology, the risk for small cell carcinoma was higher than for other subtypes. This analysis strengthens the evidence that residential radon is a relevant risk factor for lung cancer.     

Residential radon and risk of lung cancer: a combined analysis of 7 North American case-control studies

BACKGROUND: Underground miners exposed to high levels of radon have an excess risk of lung cancer. Residential exposure to radon is at much lower levels, and the risk of lung cancer with residential exposure is less clear. We conducted a systematic analysis of pooled data from all North American residential radon studies. METHODS: The pooling project included original data from 7 North American case-control studies, all of which used long-term alpha-track detectors to assess residential radon concentrations. A total of 3662 cases and 4966 controls were retained for the analysis. We used conditional likelihood regression to estimate the excess risk of lung cancer. RESULTS: Odds ratios (ORs) for lung cancer increased with residential radon concentration. The estimated OR after exposure to radon at a concentration of 100 Bq/m3 in the exposure time window 5 to 30 years before the index date was 1.11 (95% confidence interval = 1.00-1.28). This estimate is compatible with the estimate of 1.12 (1.02-1.25) predicted by downward extrapolation of the miner data. There was no evidence of heterogeneity of radon effects across studies. There was no apparent heterogeneity in the association by sex, educational level, type of respondent (proxy or self), or cigarette smoking, although there was some evidence of a decreasing radon-associated lung cancer risk with age. Analyses restricted to subsets of the data with presumed more accurate radon dosimetry resulted in increased estimates of risk. CONCLUSIONS: These results provide direct evidence of an association between residential radon and lung cancer risk, a finding predicted using miner data and consistent with results from animal and in vitro studies.     

Evaluation of radon levels in bank buildings: results of a survey on a major Italian banking group

Radon, the second cause of lung cancer after smoking, is a natural, radioactive gas, which originates from the soil and pollutes indoor air, especially in closed or underground spaces. Italian legislation recommends an action level of 500 Bq/m3 per year for occupational exposure in underground premises. OBJECTIVES: Since banks usually use various underground premises (archives, safe-deposit room), a study was made of the radon levels on such premises with the aim of identifying useful monitoring strategies. METHODS: 134 branches of a major Italian banking group were examined using 1817 nuclear track dosimeters at ground level and underground level premises. The branches were located in 7 Italian regions in the north (Piedmont, Lombardy, Veneto), centre (Lazio) and south (Campania, Apulia, Sicily). Information on measurement points was recorded in a technical sheet and statistical analysis was carried out. RESULTS: Annual underground measurements gave an average concentration of 157 Bq/m3, with 5.1% for 400 < C < 500 Bq/m3 and 2.9%for C > 500 Bq/m3. Seasonal variability was reflected in a significant decrease in concentrations between winter and spring (delta(mean)% = -47.3%) and good stability between autumn and winter (delta(mean)% = 3%); moreover quarterly concentrations account for 85% of the variability of the corresponding annual level. A multiple linear regression model (R2 = 0.33) indicated geographic location as the principal factor in radon accumulation, followed by underground level, humidity, use, lack of windows, heating and natural ventilation, and direct contact of at least one wall with ground rock; whereas the safe-deposit room structure seems to protect from radon accumulation. Moreover, the ground level measurement results were significantly associated with the corresponding underground average concentrations (p < 0.001). CONCLUSIONS: The results could be a useful tool in planning a monitoring strategy for assessment of bank worker exposure, especially for banking groups with a large number of branches.     

Glass-based radon-exposure assessment and lung cancer risk

Lung cancer risk estimation in relation to residential radon exposure remains uncertain, partly as a result of imprecision in air-based retrospective radon-exposure assessment in epidemiological studies. A recently developed methodology provides estimates for past radon concentrations and involves measurement of the surface activity of a glass object that has been in a subject's dwellings through the period for exposure assessment. Such glass measurements were performed for 110 lung cancer subjects, diagnosed 1985 to 1995, and for 231 control subjects, recruited in a case-control study of residential radon and lung cancer among never-smokers in Sweden. The relative risks (with 95% confidence intervals) of lung cancer in relation to categories of surface-based average domestic radon concentration during three decades, delimited by cutpoints at 50, 80, and 140 Bq m(-3), were 1.60 (0.8 to 3.4), 1.96 (0.9 to 4.2), and 2.20 (0.9 to 5.6), respectively, with average radon concentrations below 50 Bq m(-3) used as reference category, and with adjustment for other risk factors. These relative risks, and the excess relative risk (ERR) of 75% (-4% to 430%) per 100 Bq m(-3) obtained when using a continuous variable for surface-based average radon concentration estimates, were about twice the size of the corresponding relative risks obtained among these subjects when using air-based average radon concentration estimates. This suggests that surface-based estimates may provide a more relevant exposure proxy than air-based estimates for relating past radon exposure to lung cancer risk.