Gary G. Schwartz

Importance: Few environmental risk factors for ovarian cancer have been discovered. Women exposed to ionizing radiation from the atomic bomb during World War II experienced an increased risk of ovarian cancer. Today, the largest source of ionizing radiation is radon gas in the home, but whether ionizing radiation is associated with increased risk of ovarian cancer more broadly is unknown. Objective: To evaluate whether higher home radon levels are associated with increased risk of ovarian cancer. Design, Setting, and Participants: This prospective cohort study included 127 547 women from the Women’s Health Initiative, including 40 clinical centers across the US, with outcomes followed up for 31 years (1993-2024). Postmenopausal women aged 50 to 79 years were enrolled in an observational study or 1 or more randomized clinical trials. All cases of ovarian cancer were physician adjudicated. Exposure: Radon measurements from the 1993 US Geological Survey, classified into low (4 pCi/L), were linked with the geocoded home addresses of participants at baseline (1993-1998). Main Outcomes and Measures: Hazard ratios (HRs) for ovarian cancer, adjusted for covariates with 95% CIs. Results: Among the 127 547 women (mean [SD] age, 63.1 [7.2] years) with available radon zone values, 1645 incident ovarian cancers and 1048 ovarian cancer deaths were observed over a mean (SD) follow-up of 17.7 (8.4) years. After adjustment for covariates, the HR for all ovarian cancers for women living in the medium radon zone compared with women living in the low radon zone was not significantly higher (HR, 1.13 [95% CI, 1.00-1.29]). However, the HR was significantly higher for women living in the high radon zone compared with those living in the low radon zone (HR, 1.31 [95% CI, 1.11-1.54]). Similar findings were observed for the most common histologic type, serous ovarian cancer, for which the HR in the medium zone was 1.06 (95% CI, 0.88-1.27) and the HR in the high zone was 1.38 (95% CI, 1.09-1.74). Ovarian cancer mortality also was significantly higher in the high radon zone compared with the low radon zone (HR, 1.31 [95% CI, 1.07-1.60]). Sensitivity analyses using 3 alternate radon measures produced similar results. Conclusions and Relevance: In this large, prospective cohort of postmenopausal women, the risks of ovarian cancer incidence and mortality were significantly higher for women living in homes in the high radon zone. Residential radon is a ubiquitous and modifiable risk factor. This is the first epidemiologic study of radon and ovarian cancer among postmenopausal women to date, and its findings suggest a potential target for mitigating cancer risk.

Little is known about the role of radon in the epidemiology of stroke among women. We therefore examined the association between home radon exposure and risk of stroke among middle-aged and older women in the United States. We conducted a prospective cohort study of postmenopausal women aged 50-79 years at baseline (1993-1998) in the Women's Health Initiative. We measured exposures as 2-day, indoor, lowest living-level average radon concentrations in picocuries per liter (pCi/L) as estimated in 1993 by the US Geological Survey and reviewed by the Association of American State Geologists under the Indoor Radon Abatement Act. We used Cox proportional hazards models to estimate risk of incident, neurologist-adjudicated stroke during follow-up through 2020 as a hazard ratio and 95% CI, adjusting for study design and participant demographic, social, behavioral, and clinical characteristics. Among 158,910 women without stroke at baseline (mean age 63.2 years; 83% white), 6,979 incident strokes were identified over follow-up (mean 13.4 years). Incidence rates were 333, 343, and 349 strokes per 100,000 woman-years at radon concentrations of 4 pCi/L, respectively. Compared with women living at concentrations 4 pCi/L had higher covariate-adjusted risks of incident stroke: hazard ratio (95% CI) 1.06 (0.99-1.13) and 1.14 (1.05-1.22). Using nonlinear spline functions to model radon, stroke risk was significantly elevated at concentrations ranging from 2 to 4 pCi/L (p = 0.0004), that is, below the United States Environmental Protection Agency Radon Action Level for mitigation (4 pCi/L). Associations were slightly stronger for ischemic (especially cardioembolic, small vessel occlusive, and large artery atherosclerotic) than hemorrhagic stroke, but otherwise robust in sensitivity analyses. Radon exposure is associated with moderately increased stroke risk among middle-aged and older women in the United States, suggesting that promulgation of a lower Radon Action Level may help reduce the domestic impact of cerebrovascular disease on public health.

Introduction: Exposure to residential radon is a preventable cause of cancer. Prevention requires testing, but the percentage of homes that have been tested is small. One reason for the low testing rates may be that printed brochures fail to motivate people to obtain and return a radon test. Methods: We developed a radon app for smartphones that contained the same information as printed brochures. We conducted a randomized, controlled trial that compared the app to brochures in a population comprised largely of homeowners. Cognitive endpoints included radon knowledge, attitudes toward testing, perceived severity and susceptibility to radon, and response and self-efficacy. Behavioral endpoints were participants’ requests for a free radon test and the return of the test to the lab. Participants (N = 116) were residents of Grand Forks, North Dakota, a city with one of the nation’s highest radon levels. Data were analyzed by general linear models and logistic regression. Results: Participants in both conditions showed significant increases in radon knowledge (p < 0.001), perceived susceptibility (p < 0.001), and self-efficacy (p = 0.004). There was a significant interaction, with app users showing greater increases. After controlling for income, app users were three times more likely to request a free radon test. However, contrary to expectation, app users were 70% less likely to return it to the lab (p < 0.01). Conclusions: Our findings confirm the superiority of smartphones in stimulating radon test requests. We speculate that the advantage of brochures in promoting test returns may be due to their ability to serve as physical reminders.

Radon is a preventable cause of lung cancer, but the percentage of homes tested for radon is low. We previously developed a smartphone app that informs users about radon and allows them to request a free radon test. Here we conducted a randomized, controlled trial comparing the radon app versus printed brochures on radon knowledge, attitudes, and behaviors, including the proportion of participants requesting radon tests. Participants (N = 138) were undergraduates at a midwestern university. Data were analyzed by t-tests, general linear models, and logistic regression. App users showed significantly greater increases in radon knowledge (p = 0.010) and self-efficacy (p < 0.001) and requested tests three times more often than brochure recipients (41.4% vs. 13.2%, p < 0.001). However, the rate of test usage in each condition was low, similar to 3%. In conclusion, the radon app markedly outperformed brochures in increasing knowledge and requests for radon tests. Future work should focus on methods to increase test usage.

Objective: Radon exposure is a proven cause of lung cancer and is a possible cause of other diseases. Recently, several ecologic studies explored the correlation of county-wide incidence rates for non-lung cancers with residential radon levels, using radon data reported by a commercial laboratory. However, the validity of the commercial radon data, i.e., whether they are an accurate representation of the radon levels in the counties from which they were drawn, is unknown. Methods: We compared county-wide radon data from the commercial laboratory with corresponding measurements from the same counties reported previously by the Environmental Protection Agency (EPA). Matching data were available for four states, Iowa, North Dakota, Texas, and Wisconsin, and were compared by paired t-tests. Criterion validity of the commercial tests, i.e., how well the commercial data predicted the EPA data, was tested using non-parametric methods, Kendall’s tau, Lin’s concordance, and Passing–Bablok regression. Results: The commercial and EPA data pairs from the four states were significantly positively correlated, although the size of the correlations was modest (tau = 0.490, Lin = 0.600). Passing–Bablok regression indicated that the commercial radon values were significantly higher than their EPA pairs and significantly overestimated radon at low levels (p < 0.001). Conclusions: The commercial laboratory data were moderately predictive of EPA radon levels at the county level but were significantly biased upwards at low levels. The disagreement likely has several causes, including selection bias from homes that were tested voluntarily. Ecologic studies that employ radon data obtained from commercial laboratories should be interpreted with caution.

Although the etiology of Parkinson’s disease (PD) is unknown, potentially informative clues lie in its geographic distribution. PD prevalence rates within the U.S. are significantly higher in the Midwest and Northeast, a pattern that resembles the geographic distribution of acid precipitation (“acid rain”). Using linear and multivariable regression, we examined state-wide data on PD prevalence in relation to environmental factors including total precipitation, the acidity of precipitation, the use of well water, and industrial releases of sulfuric acid. In multivariate analyses, age-, race-, and gender-adjusted prevalence rates for PD were inversely correlated with well water use and positively correlated with industrial releases of sulfuric acid and with the quantity of acid precipitation (p < 0.0001). To our knowledge, this is the first report of an association between PD and acid rain. Because acid rain is known to leach metals from soils and pipes into drinking water, acid rain’s association with PD prevalence adds support for a role for metals in the etiology of PD.

Background: Exposure to radon at home is the largest cause of lung cancer after smoking, and the combination of smoking and radon increases lung cancer risk several-fold. North Dakota has some of the highest residential radon levels in the United States. Although family physicians in North Dakota commonly counsel patients about smoking cessation, little is known about their knowledge and practices concerning radon. Methods: We mailed a questionnaire to 350 North Dakota family physicians regarding radon knowledge, beliefs, their own radon testing, and radon counseling of patients. The responses were analyzed by descriptive statistics, analysis of variance, and logistic regression. Results: Sixty-one percent of the surveys were completed. Seventy percent of family physicians correctly identified radon as radioactive; 67% reported that they do not inform patients about radon; and 80% reported never discussing the combined hazards of radon and smoking. Conversely, 35% of family physicians reported that they tested their own homes for radon. Discussion: Most North Dakota family physicians are knowledgeable about radon, and more than one third have tested their own homes. However, only a minority transmit this knowledge to their patients. Future efforts should educate physicians about communicating radon risks, especially in conjunction with smoking.