The residential radon-lung cancer association in U.S. counties: a commentary

There is little doubt that underground miners exposed to radon and its progeny have increased rates of lung cancer. Residential radon exposures should carry a possibly smaller risk of increased cancer. When it became possible to collect radon data in a large number of U.S. homes and the data were aggregated by counties, the apparent association with lung cancer was a negative one, even when many other variables were taken into account. Residential radon levels are higher in suburban residences leading to a negative association with population density. Population density is strongly positively associated with lung cancer. It follows that aggregate residential radon and lung cancer rates should be negatively associated for reasons having nothing to do with the possibility of radon being carcinogenic to the lung. A second problem presented by the data is the one of sampling bias since the county lung cancer data are from the whole county population, but only a few residences are tested. Examples of other inherent associations in environmental epidemiology are cited. One strategy is to study areas of the same population density but with radon exposure gradients. This is approximated by choice of rural high radon states. Counties in such states have weak and inconsistent associations between radon and lung cancer, some of which are positive. I conclude that counties are generally inappropriate units for study of radon and lung cancer associations.     

Epidemiological associations among lung cancer,radon exposure and elevation above sea level--a reassessment of Cohen''s county level radon study

Inhalation of radon (222Rn) decay products by persons living in homes has been associated with increased risk of lung cancer. Some epidemiological studies have shown a positive association between radon exposure and lung cancer rates. However, a large U.S.-wide ecological study (Cohen 1995) has shown a clear inverse association between average county radon concentration in homes and average lung cancer rates in the county. Cohen's strong inverse association between radon and lung cancer is surprising since there is no plausible biological reason for an inverse causal relationship between the two. We plot the county average lung cancer rate vs. the elevation above sea level (altitude) and show an inverse association between county average lung cancer rate and elevation. The elevation used for each county is the altitude of the most populous place in the county. We postulate that the decrease in lung cancer rates with higher elevations is caused by the carcinogenic effect of higher absolute oxygen concentration in the inspired air at lower elevations. Stratifying Cohen's lung cancer vs. radon data into ten groups of counties with similar elevations removes some, but not all, of his inverse association between radon and lung cancer.     

Toward a more realistic appraisal of the lung cancer risk from radon: the effects of residential mobility.

OBJECTIVES: A consideration of the effects of residential mobility produces much more realistic estimates of typical individuals' radon exposures and mortality risks than those of the Environmental Protection Agency (EPA). METHODS: A model linking residential mobility, the distribution of radon in US homes, and lung cancer risk is used to simulate lifetime radon exposure, with and without mitigation of high-radon homes, for typical mobile individuals. Radon-related lung cancer mortality risks are then estimated for smokers and never-smokers. RESULTS: Most individuals residing in high-radon homes have equivalent lifelong radon exposures well below those they are currently experiencing. Consequently, actual lung cancer risks are generally well below those implied in the EPA's radon risk charts. For most people who mitigate high-radon homes, risk reduction is modest. CONCLUSIONS: Radon may indeed be responsible for as large a population risk of lung cancer as the EPA estimates. However, caution must be used in interpreting the EPA's risk assessment for individuals; in many cases, mitigation will have little effect on residents' health risks.     

Radon in homes--a possible cause of lung cancer

An earlier case-referent study [Scand j work environ & health 5 (1979) 10-15] has indicated a possible relationship between lung cancer and exposure to radon and radon daughters in dwellings. Indoor radon concentrations seem to depend on both building material and leakage of radon from the ground. This new study, in a rural area, is a further attempt to elucidate the etiology of lung cancer, taking into consideration type of house and ground conditions, as well as smoking habits. Although the choice of a rural study population helped to eliminate various confounding exposures in the urban environment, it limited the size of the study because of the rareness of lung cancer in rural populations. Long-term residents, 30 years or more in the same houses, were studied, and again an association was found between lung cancer and estimated exposure to radon and radon daughters in homes. The data also seem to indicate the possibility of a multiplicative effect between smoking and exposure to radon and radon daughters in homes, but there was also some confounding between these factors in the data.     

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.     

Predictors of Indoor Radon Concentrations in Pennsylvania, 1989–2013

Background

Radon is the second-leading cause of lung cancer worldwide. Most indoor exposure occurs by diffusion of soil gas. Radon is also found in well water, natural gas, and ambient air. Pennsylvania has high indoor radon concentrations; buildings are often tested during real estate transactions, with results reported to the Department of Environmental Protection (PADEP).

Objectives

We evaluated predictors of indoor radon concentrations.

Methods

Using first-floor and basement indoor radon results reported to the PADEP between 1987 and 2013, we evaluated associations of radon concentrations (natural log transformed) with geology, water source, building characteristics, season, weather, community socioeconomic status, community type, and unconventional natural gas development measures based on drilled and producing wells.

Results

Primary analysis included 866,735 first measurements by building, with the large majority from homes. The geologic rock layer on which the building sat was strongly associated with radon concentration (e.g., Axemann Formation, median = 365 Bq/m³, IQR = 167–679 vs. Stockton Formation, median = 93 Bq/m³, IQR = 52–178). In adjusted analysis, buildings using well water had 21% higher concentrations (β = 0.191, 95% CI: 0.184, 0.198). Buildings in cities (vs. townships) had lower concentrations (β = –0.323, 95% CI: –0.333, –0.314). When we included multiple tests per building, concentrations declined with repeated measurements over time. Between 2005 and 2013, 7,469 unconventional wells were drilled in Pennsylvania. Basement radon concentrations fluctuated between 1987 and 2003, but began an upward trend from 2004 to 2012 in all county categories (p < 0.001), with higher levels in counties having ≥ 100 drilled wells versus counties with none, and with highest levels in the Reading Prong.

Conclusions

Geologic unit, well water, community, weather, and unconventional natural gas development were associated with indoor radon concentrations. Future studies should include direct environmental measurement of radon, as well as building features unavailable for this analysis.

Citation

Casey JA, Ogburn EL, Rasmussen SG, Irving JK, Pollak J, Locke PA, Schwartz BS. 2015. Predictors of indoor radon concentrations in Pennsylvania, 1989–2013. Environ Health Perspect 123:1130–1137; http://dx.doi.org/10.1289/ehp.1409014     

Mortality of a residential cohort exposed to radon from industrially contaminated soil

A historical cohort mortality study was conducted in three neighborhoods of Essex County, New Jersey, to investigate the mortality patterns of persons who had inhabited 45 homes documented to be contaminated by radon gas emanating from radium processing waste. Residency history and vital status were collected for 752 persons, comprising 91% of the subjects enumerated who had resided in the index homes for at least one year during the years 1923-1983. Standardized mortality ratios (SMR) were used to compare the death rates of the study group with the death rates of the United States and New Jersey. While there were no statistically significant excesses of lung cancer for the cohort or its subgroups, an elevated mortality rate for lung cancer was found for white males in the comparison of lung cancer mortality rates in the United States (SMR = 1.5, 95% confidence interval (CI) 0.7-2.7) and New Jersey (SMR = 1.7, 95% CI 0.8-3.2). No excess of lung cancer was observed in females or nonwhites. The small size of the cohort and the inability to collect smoking histories or complete occupational data limited the study. Nevertheless, the degree of excess lung cancer among white males was in agreement with both the attributable and relative risk estimates per unit of exposure derived for radon from mining studies.     

Indoor radon levels in the northeastern U.S.: effects of energy-efficiency in homes

The expectation of elevated 222Rn levels in modern homes that have low air interchange rates with the out-of-doors caused us to survey both solar and conventional homes in northeastern New York State. The solar homes as a group have three times the 222Rn levels of the conventional homes, and specific problems exist that are introduced or exaggerated by modern construction. For example the highest two levels of radon in the solar homes give radiation doses over 30 yr that are known to produce lung cancer in 1% of uranium miners. Summer readings in more than half of the cases are different from winter ones by a factor of two or more, so that year-round measurements are necessary for precise dosimetry. The track etching technique is ideally suited for such measurements.     

Optimistic biases in public perceptions of the risk from radon.

Survey data were obtained from a random sample of 657 homeowners in New Jersey and also from 141 homeowners who had already monitored their homes for radon. People who had not tested tended to believe that they were less at risk than their neighbors, and they interpreted ambiguous predictors of home radon levels in ways that supported their beliefs of below-average risk. Residents who had already tested their homes were relatively accurate about the probability of health effects. In both groups less than half of those who knew that radon can cause lung cancer were willing to admit that it would be serious if they suffered health effects from this source. The optimistic biases of the public may hamper attempts to encourage home radon monitoring and to promote appropriate mitigation measures in homes with elevated radon concentrations.     

Should radon be reduced in homes? A cost-effect analysis

BACKGROUND: Radon is a radioactive gas that may leak into buildings from the ground. Radon exposure is a risk factor for lung cancer. An intervention against radon exposure in homes may consist of locating homes with high radon exposure (above 200 Bq m(-3)) and improving these, and protecting future houses. The purpose of this paper is to calculate the costs and the effects of this intervention. METHODS: We performed a cost-effect analysis from the perspective of the society, followed by an uncertainty and sensitivity analysis. The distribution of radon levels in Norwegian homes is lognormal with mean = 74.5 Bq m(-3), and 7.6% above 200 Bq m(-3). RESULTS: The preventable attributable fraction of radon on lung cancer was 3.8% (95% uncertainty interval: 0.6%, 8.3%). In cumulative present values the intervention would cost $238 (145, 310) million and save 892 (133, 1981) lives; each life saved costs $0.27 (0.09, 0.9) million. The cost-effect ratio was sensitive to the radon risk, the radon exposure distribution, and the latency period of lung cancer. Together these three parameters explained 90% of the variation in the cost-effect ratio. CONCLUSIONS: The uncertainty in the estimated cost per life is large, mainly due to uncertainty in the risk of lung cancer from radon. Based on estimates from road construction, the Norwegian society has been willing to pay $1 million to save a life. This is above the upper uncertainty limit of the cost per life. The intervention against radon in homes, therefore, seems justifiable.     

Radon and lung cancer risk: taking stock at the millenium

Radon is a well-established human carcinogen for which extensive data are available, extending into the range of exposures experienced by the general population. Mounting epidemiologic evidence on radon and lung cancer risk, now available from more than 20 different studies of underground miners and complementary laboratory findings, indicates that risks are linear in exposure without threshold. Radon is also a ubiquitous indoor air pollutant in homes, and risk projections imply that radon is the second leading cause of lung cancer after smoking. Recommended control strategies in the United States and other countries, which include testing of most homes and mitigation of those exceeding guideline levels, have been controversial. Further research is needed, drawing on molecular and cellular approaches and continuing the follow-up of the underground miner cohorts, and scientists should work toward constructing mechanistically based models that combine epidemiologic and experimental data to yield risk estimates with enhanced certainty.     

The effectiveness of mitigation for reducing radon risk in single-family Minnesota homes

ABSTRACT: Increased lung cancer incidence has been linked with long-term exposure to elevated residential radon. Experimental studies have shown that soil ventilation can be effective in reducing radon concentrations in single-family homes. Most radon mitigation systems in the U.S. are installed by private contractors. The long-term effectiveness of these systems is not well known, since few state radon programs regulate or independently confirm post-mitigation radon concentrations. The effectiveness of soil ventilation systems in Minnesota was measured for 140 randomly selected clients of six professional mitigators. Homeowners reported pre-mitigation radon screening concentrations that averaged 380 Bq m (10.3 pCi L). Long term post-mitigation radon measurements on the two lowest floors show that, even years after mitigation, 97% of these homes have concentrations below the 150 Bq m U.S. Environmental Protection Agency action level. The average post-mitigation radon in the houses was 30 Bq m, an average observed reduction of >90%. If that reduction was maintained over the lifetime of the 1.2 million Minnesotans who currently reside in single-family homes with living space radon above the EPA action level, approximately 50,000 lives could be extended for nearly two decades by preventing radon-related lung cancers.     

Radon mitigation survey among New York State residents living in high radon homes.

Residential exposure to radon has been considered an important environmental risk factor for lung cancer. Since 1986, U.S. EPA has recommended that all dwellings below the third floor be tested for the presence of radon and be mitigated to reduce indoor radon in homes with levels exceeding 148 Bq m(-3). In order to evaluate the effectiveness of New York State Department of Health's efforts to increase public awareness about radon risk and to promote radon testing and mitigation in compliance with EPA's guideline, a statewide radon mitigation survey was conducted between September 1995 and January 1996 among New York State residents whose homes had radon levels equal to or greater than 148 Bq m(-3) on the first floor (or above) living areas. The survey found that about 60% of 1,113 participants had taken actions for radon mitigation. The percentage of respondents who took actions to reduce radon levels in their homes increased with increasing education level as well as household income level. The method of installing a powered system to provide more ventilation was a more effective mitigation method than opening widows/doors or sealing cracks/openings in the basement. Mitigation performed by contractors was more effective in reducing radon levels than mitigation performed by residents. The reasons for performing radon mitigation given by the majority of respondents were those strongly related to radon health risk. High home radon level was an important motivational factor to stimulate radon mitigation. On the other hand, the cost of radon mitigation was a major barrier in decision making for performing radon mitigation and for selecting mitigation measures. Thus, public educational campaigns that focus on increasing awareness and knowledge about radon health risks and development of less expensive radon mitigation methods may help in promoting radon mitigation.     

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.     

210Po implanted in glass surfaces by long term exposure to indoor radon

Recent epidemiologic investigations of the relationship between residential radon gas exposure and lung cancer relied on contemporary radon gas measurements to estimate past radon gas exposures. Significant uncertainties in these exposure estimates can arise from year-to-year variation of indoor radon concentrations and subject mobility. Surface implanted 210Po has shown potential for improving retrospective radon gas exposure estimates. However, in previous studies, the ability of implanted 210Po activity to reconstruct cumulative radon gas exposure was not tested because glass was not available from homes with known radon-gas concentration histories. In this study, we tested the validity of the retrospective radon gas reconstruction using implanted 210Po surface activity by measuring glass surfaces from homes whose annual-average radon gas concentrations had been measured almost every year during two decades. Regression analysis showed a higher correlation between measured surface activity and cumulative radon gas exposure in these homes (R2>0.8) than was observed in homes where only contemporary radon gas measurements were available. The regression slope (0.57 ky m(-1)) was consistent with our earlier retrospective results. Surface activity measurements were as reliable for retrospective radon gas exposure reconstruction as yearlong gas measurements. Both methods produced estimates that were within 25% of the long-term average radon gas concentrations in a home. Surface measurements can be used for home screening tests because they can provide rapid, reliable estimates of past radon gas concentrations. Implanted 210Po measurements are also useful in retrospective epidemiologic studies that include participants who may have been exposed to highly variable radon concentrations in previously occupied or structurally modified homes.     

Radon awareness and mitigation in Vermont: a public health survey

Radon exposure is associated with an increased incidence of lung cancer, and elevated levels may be found in as many as 1 out of 15 homes. The U.S. EPA recommends testing homes for radon and mitigating over the advisory level of 4 picocuries per liter (4 pCi L(-1), or 148 Bq m(-3)). A sample population from a list of Vermont residents who had tested their residence for radon through the Vermont Department of Health and who had elevated levels were mailed a survey to assess demographic characteristics, knowledge about radon, mitigation rates, types of mitigation, as well as barriers to mitigation. The response rate was 63%. Forty-three percent of respondents mitigated. Roughly half were not completely knowledgeable of radon based upon the ability to associate radon exposure with lung cancer risk. Reasons not to mitigate radon levels in homes were cost and lack of concern over elevated levels. A multivariate logistic regression analysis revealed factors associated with mitigating: an education level of college or higher (p = 0.02), concern that a high radon level would affect real estate value (p = 0.04), and home age less than 10 y (p = 0.05). In summary, less than half of Vermonters with elevated radon levels participating in the Department of Health program mitigated. We identify factors associated with radon mitigation that may lead to improved radon education and mitigation practice.     

Predicted reduction in lung cancer risk following cessation of smoking and radon exposure

Recently there has been considerable public and regulatory concern that radon, produced by the decay of naturally occurring uranium, can accumulate in homes, offices, and schools at levels that may substantially increase the risk of lung cancer. The major cause of lung cancer is smoking, and radon appears to interact multiplicatively with smoking in causing lung cancer. Thus, the most effective way to reduce the increased risk of lung cancer resulting from radon exposure is to cease smoking. In this paper, a model for the risks associated with radon exposure that was developed by a committee of the National Academy of Sciences is used to calculate the benefits, in terms of reduction in lifetime risk of lung cancer, of ceasing to smoke, ceasing radon exposure, or ceasing both. Ceasing to smoke is considerably more beneficial than ceasing radon exposure, and thus policymakers addressing the health effects of radon should place priority on encouraging individuals to stop smoking.     

Indoor air pollutants: limited-resource households and child care facilities

This paper reports on a study of indoor air quality in homes and child care facilities in non-metropolitan counties of New York State. Specific pollutants examined were lead, radon, carbon monoxide, asbestos, and mold. Some homes had high levels of pollutants, and certain pollutants were significantly and negatively correlated with household income. High levels of pollutants also were observed in many child care facilities, which raises questions about constant exposure of children to pollutants. Recommendations are made for lowering pollutant levels in low-income households and child care facilities.     

Gastric cancer in New Mexico counties with significant deposits of uranium

Several counties in northern New Mexico display high rates of mortality from gastric cancer. Significant differences in sex-specific, age-adjusted, average annual stomach cancer mortality rates among whites from 1970-1979 were found between counties with significant deposits of uranium compared to those without significant deposits. These results remained unchanged when either socioeconomic status or Hispanic ethnicity were considered. Additional research needs to consider individual characteristics and competing risk factors for individuals with gastric cancer in these counties. A working hypothesis is that residents of counties with significant deposits of uranium are exposed to higher-than-average environmental levels of radionuclides such as radon and radon daughters, or to trace elements such as arsenic, cadmium, selenium, and lead which are commonly found in areas with uranium deposits.     

Radon,Smoking, and Lung Cancer: The Need to Refocus Radon Control Policy

Exposure to radon is the second leading cause of lung cancer, and the risk is significantly higher for smokers than for nonsmokers. More than 85% of radon-induced lung cancer deaths are among smokers. The most powerful approach for reducing the public health burden of radon is shaped by 2 overarching principles: public communication efforts that promote residential radon testing and remediation will be the most cost effective if they are primarily directed at current and former smokers; and focusing on smoking prevention and cessation is the optimal strategy for reducing radon-induced lung cancer in terms of both public health gains and economic efficiency. Tobacco control policy is the most promising route to the public health goals of radon control policy.It is estimated that 222 520 new cases of lung cancer were diagnosed and approximately 157 300 people died from this disease in the United States in 2010.1 Exposure to radon—an odorless radioactive gas that can be trapped in homes and other structures—is considered the second leading cause of lung cancer after smoking.2–5 The Environmental Protection Agency (EPA) estimates that residential radon causes approximately 21 000 lung cancer deaths in the United States each year.6,7 In response, the EPA and numerous organizations, including the National Radon Safety Board, promote wide-scale radon screening and remediation in domestic residences.8The strong synergism between radon exposure and smoking as risk factors is a critical aspect of the relationship between radon and lung cancer.2,4,9 That is, the absolute magnitude of the lung cancer risk associated with radon exposure is significantly higher for ever-smokers than for never-smokers. It is estimated that 86% of radon-related lung cancer deaths are in current and former smokers.7,10Angell recently claimed that radon research and remediation programs have “stalled” in the face of severe funding cuts over the past decade and that there has been little progress in testing and remediation in the US housing stock.11 With the recent economic downturn and the resource constraints most governmental health departments face, Angell’s concerns unfortunately will remain salient in the near term. Thus, we have argued that a concentrated policy focus on smoking prevention and cessation and on smokers as targets of both smoking cessation efforts and of radon testing and remediation programs currently provides the most powerful and cost-effective opportunity for reducing the public health burden of radon.Although some researchers have made this argument in the past, there is very little evidence in the United States of any significant radon control activities targeting smokers or of any coordinated efforts between tobacco control and radon control programs or initiatives.4,12 We have elucidated the evidence-based position that residential radon control policy will be most effective and efficient if it combines forces with tobacco prevention and control efforts. We have also offered strategic guidance about what a synergistic radon and tobacco control approach entails.