Variation of radon levels in U.S. homes correlated with house characteristics, location, and socioeconomic factors

Residential radon exposure and hypertensive disorders of pregnancy in Massachusetts, USA: A cohort study

BACKGROUND

Exposure to ionizing radiation has been associated with hypertension, but the relationship between residential radon exposure and hypertensive disorders of pregnancy (HDP) has not been examined.

METHODS

We used the Massachusetts Birth Registry of Vital Records from 2001 to 2015 including women with a singleton pregnancy without prior hypertension. The binary outcome (HDP) included gestational hypertension and pre-eclampsia cases and was assessed using birth certificate data. We obtained 141,665 basement radon measurements from Spruce Environmental Technologies, Inc. and modeled the monthly zip code basement radon level. We used a logistic regression model adjusted for sociodemographic covariates, maternal comorbidities, PM_2.5, season, temperature, and relative humidity. We examined effect modification by maternal age, race, and maternal education as an indicator of socio-economic status.

RESULTS

Of 975,528 women, 3.7% (36,530) of them developed HDP. Zip code level radon ranged from 22 to 333 mBq/m³. An interquartile range (IQR) increase in zip code radon level throughout pregnancy was associated with a 15% increase in the odds of HDP (95% CI 13% to 18%). In women less than 20 years old, an IQR increase in zip code level radon was associated with 38% increase in the odds of HDP (95% CI 24% to 50%), while the effect was smaller in older women. There was no effect modification by maternal race or education.

CONCLUSIONS

In this cohort, higher levels of residential radon are associated with increased odds of HDP. After stratifying by age, this effect was stronger in participants younger than 20 years old. Since the burden of hypertensive disorders of pregnancy is increasing and affects women's future cardiovascular health, identification of modifiable risk factors is of great importance.

Spatial and Temporal Variations of Indoor Airborne Radon Decay Product Dose Rate and Surface-Deposited Radon Decay Products in Homes

The temporal variations of the airborne radon decay product dose rate and deposited radon decay product activities, as well as the within-house and house-to-house variations of radon concentrations, were evaluated through repeated field measurements. Long-term average radon and surface-deposited radon decay product concentrations were measured in 76 rooms of 38 houses. Temporal variation of radon, as well as airborne and surface-deposited radon decay products, were measured in 11 of the 38 houses during two different seasons. Environmental factors that have the potential to influence airborne dose rate and deposited radon decay products were also studied. Airborne dose rates were calculated from the unattached and attached potential alpha energy concentrations using two dosimetric models. For one model, the observed dose variations were 103%, 74%, 58%, and 60% for the total, house-to-house, within-house, and within-room temporal variations, respectively. For the other model, the dose variations were 100%, 66%, 61%, and 46%, respectively. Surface-deposited Po showed variations of 79%, 57%, 42%, and 48%, respectively. These substantial radon decay product concentration variations suggest that multiple locations and time-integrated measurements are needed to make an accurate assessment of the chronic radon-related doses in homes. Smoking was the environmental factor that had the largest temporal and spatial effect on airborne radon decay product dose rates.

Variation with socioeconomic status of indoor radon levels in Great Britain: The less affluent have less radon

We demonstrate a strong correlation between domestic radon levels and socio-economic status (SES) in Great Britain, so that radon levels in homes of people with lower SES are, on average, only about two thirds of those of the more affluent. This trend is apparent using small area measures of SES and also using individual social classes. The reasons for these differences are not known with certainty, but may be connected with greater underpressure in warmer and better-sealed dwellings. There is also a variation of indoor radon levels with the design of the house (detached, terraced, etc.). In part this is probably an effect of SES, but it appears to have other causes as well. Data from other countries are also reviewed, and broadly similar effects seen in the United States for SES, and in other European countries for detached vs other types of housing. Because of correlations with smoking, this tendency for the lower SES groups to experience lower radon levels may underlie the negative association between radon levels and lung cancer rates in a well-known ecological study based on US Counties. Those conducting epidemiological studies of radon should be alert for this effect and control adequately for SES.

Risk-reduction strategies to expand radon care planning with vulnerable groups

OBJECTIVES

Radon is the second leading cause of lung cancer in the United States and the leading cause of lung cancer among nonsmokers. Residential radon is the cause of approximately 21,000 U.S. lung cancer deaths each year. Dangerous levels of radon are just as likely to be found in low-rise apartments and townhomes as single-family homes in the same area. The preferred radon mitigation strategy can be expensive and requires structural modifications to the home. The public health nurse (PHN) needs a collection of low-cost alternatives when working with low-income families or families who rent their homes.

METHOD

A review of the literature was performed to identify evidence-based methods to reduce radon risk with vulnerable populations.

RESULTS

Fourteen recommendations for radon risk reduction were categorized into four strategies. Nine additional activities for raising awareness and increasing testing were also included.

DISCUSSION

The results pair the PHN with practical interventions and the underlying rationale to develop radon careplans with vulnerable families across housing types. The PHN has both the competence and the access to help families reduce their exposure to this potent carcinogen.

Prediction of residential radon exposure of the whole Swiss population: comparison of model-based predictions with measurement-based predictions

Radon plays an important role for human exposure to natural sources of ionizing radiation. The aim of this article is to compare two approaches to estimate mean radon exposure in the Swiss population: model-based predictions at individual level and measurement-based predictions based on measurements aggregated at municipality level. A nationwide model was used to predict radon levels in each household and for each individual based on the corresponding tectonic unit, building age, building type, soil texture, degree of urbanization, and floor. Measurement-based predictions were carried out within a health impact assessment on residential radon and lung cancer. Mean measured radon levels were corrected for the average floor distribution and weighted with population size of each municipality. Model-based predictions yielded a mean radon exposure of the Swiss population of 84.1 Bq/m(3) . Measurement-based predictions yielded an average exposure of 78 Bq/m(3) . This study demonstrates that the model- and the measurement-based predictions provided similar results. The advantage of the measurement-based approach is its simplicity, which is sufficient for assessing exposure distribution in a population. The model-based approach allows predicting radon levels at specific sites, which is needed in an epidemiological study, and the results do not depend on how the measurement sites have been selected.

Radon control activities for lung cancer prevention in national comprehensive cancer control program plans, 2005-2011

Introduction

Radon is the second leading cause of lung cancer among smokers and the leading cause among nonsmokers. The US Environmental Protection Agency recommends that every home be tested for radon. Comprehensive Cancer Control (CCC) programs develop cancer coalitions that coordinate funding and resources to focus on cancer activities that are recorded in cancer plans. Radon tests, remediation, and radon mitigation techniques are relatively inexpensive, but it is unclear whether coalitions recognize radon as an important carcinogen.

Methods

We reviewed 65 cancer plans created from 2005 through 2011 for the terms “radon,” “radiation,” or “lung.” Plan activities were categorized as radon awareness, home testing, remediation, supporting radon policy activities, or policy evaluation. We also reviewed each CCC program’s most recent progress report. Cancer plan content was reviewed to assess alignment with existing radon-specific policies in each state.

Results

Twenty-seven of the plans reviewed (42%) had radon-specific terminology. Improving awareness of radon was included in all 27 plans; also included were home testing (n = 21), remediation (n = 11), support radon policy activities (n = 13), and policy evaluation (n = 1). Three plans noted current engagement in radon activities. Thirty states had radon-specific laws; most (n = 21) were related to radon professional licensure. Eleven states had cancer plan activities that aligned with existing state radon laws.

Conclusion

Although several states have radon-specific policies, approximately half of cancer coalitions may not be aware of radon as a public health issue. CCC-developed cancer coalitions and plans should prioritize tobacco control to address lung cancer but should consider addressing radon through partnership with existing radon control programs.

Householder status and residence type as correlates of radon awareness and testing behaviors

OBJECTIVES

The primary aim of this research was to assess radon awareness and testing across 2 housing types.

DESIGN AND SAMPLE

Cross-sectional prevalence study with time trends. National, probabilistic sample of 18,138 and 29,632 respondents from the 1994 and 1998 National Health Interview Surveys, respectively.

RESULTS

Odds ratio (OR) estimates confirmed that occupants of single family homes/townhomes were twice as likely to have ever heard of radon (1994: OR=2.18; confidence intervals [CI]=2.01-2.36) (1998: OR=2.26; CI=2.09-2.44) and also more likely to know if their household air had been tested for radon (1994: OR=2.04; CI=1.57-2.65) (1998: OR=1.38; CI=1.19-1.59) as occupants of apartments/condominiums. Time trend analyses revealed that radon awareness improved from 69.4% to 70.7% and home testing among those with knowledge of radon increased from 9.7% to 15.5% over the 4-year period.

CONCLUSIONS

Housing type provided fairly stable estimates of radon awareness and testing. Findings demonstrate that housing status may be a useful variable to differentiate risk for radon awareness and testing. Public health nurses should consider their client's housing type when assessing families for environmental risks.

Test of the linear-no threshold theory: rationale for procedures

A tightly reasoned justification is presented for the procedures used in our test of the linear-no threshold theory of radiation carcinogenesis by comparing lung cancer rates with average radon exposure in U.S. counties. A key point is its dependence on ecological variables rather than on characteristics of individuals and the principal problems involve treatment of potential confounding factors (CF). The method of stratification is introduced and shown to be preferable to multiple regression for evaluating effects of confounding. Utilizing numerous available CF reduces the problem of representing a complex confounding relationship by the average value of a single CF. The requirements on a CF for affecting the results are quantified in terms of its correlations with lung cancer rates and radon levels and it is shown that the existence of an unknown confounder satisfying these requirements is highly implausible. Effects of combinations of confounding factors are treated and shown not to be important. The problem of confounding factors on the level of individuals is resolved. Consideration of plausibility of correlations is used in several applications, including treatments of uncertainty in smoking prevalence, within county differences in radon exposure between smokers and non-smokers, variations in intensity of smoking, differences between measured radon levels and actual exposures, etc. Examples are presented for all applications. The differences between our study and case-control studies, and the advantages of each for testing the linear-no threshold theory, are discussed.

Residential radon exposure and lung cancer risk: commentary on Cohen's county-based study

The large United States county-based study () in which an inverse relationship has been suggested between residential low-dose radon levels and lung cancer mortality has been reviewed. While this study has been used to evaluate the validity of the linear nonthreshold theory, the grouped nature of its data limits the usefulness of this application. Our assessment of the study's approach, including a reanalysis of its data, also indicates that the likelihood of strong, undetected confounding effects by cigarette smoking, coupled with approximations of data values and uncertainties in accuracy of data sources regarding levels of radon exposure and intensity of smoking, compromises the study's analytic power. The most clear data for estimating lung cancer risk from low levels of radon exposure continue to rest with higher-dose studies of miner populations in which projections to zero dose are consistent with estimates arising from most case-control studies regarding residential exposure.

Estimate of annual average radon concentration in the normal living area from short-term tests

Most residential radon guidelines refer to annual average radon concentration in the normal living area. However, decisions on whether a house needs mitigation are usually based on short term radon tests. Depending on where detectors are placed and when tests are performed, results of those measurements can differ significantly from the annual average radon concentration in the normal living area. We provide a practical method based on survey results in 5486 Canadian houses to estimate annual average radon levels from results of screening tests. The average ratio of radon concentration in the basement to that of the upper floors in a house is determined, and the average relative seasonal variations of radon levels in the basement and of the upper floors are identified. Based on these relative quantities, estimate factors are derived for four different combinations of detector location and the living area and tabulated for different calendar periods of radon testing. The annual average radon level can be estimated by multiplying the result of a short-term screening test with the appropriate estimate factor given in this study.

How dangerous is low level radiation?

Problems in the theoretical basis for the linear-no threshold theory of radiation carcinogenesis are reviewed, and it is shown that they very strongly suggest that the theory greatly overestimates the risk of low level radiation. A direct test of the theory, based on the radon-lung cancer relationship is described; it strongly reinforces that conclusion. However, it is shown that even if the linear-no threshold theory is valid, the public's fear of low level radiation, at least in some contexts, is grossly exaggerated.

Radon daughter exposures at the Radium Hill uranium mine and lung cancer rates among former workers, 1952-87

The aim of this historical (retrospective) cohort study was to investigate the relation between occupational exposure to radon daughters and subsequent mortality from lung cancer. Participants were former workers from the Radium Hill uranium mine, which operated in eastern South Australia from 1952 to 1961. A total of 2,574 workers were identified from mine records. Exposures to radon daughters were estimated from historical records of radon gas concentrations in the mine and from individual job histories. Exposures of underground workers were low by comparison with other mines of that period (mean 7.0 Working Level Months [WLM], median 3.0 WLM). Thirty-six percent of the cohort could not be traced beyond the end of employment at Radium Hill. Among those traced to the end of 1987, lung cancer mortality was increased relative to the Australian national population of the period (Standardized Mortality Ratio = 194, 95 percent confidence interval [CI] = 142-245). Compared with surface workers, lung cancer mortality was markedly increased in the underground workers with radon daughter exposures greater than 40 WLM (relative risk = 5.2, CI = 1.8-15.1). From the available information, we conclude that this increase is unlikely to be due to differences in smoking habits or other confounders. Taken together with the findings from other occupational studies, these results support current moves towards more stringent radiation control in the workplace, and underline the importance of research into the possible effects of domestic radon exposures.