Radon causes approximately 21,000 deaths annually from lung cancer, making it the second most important cause of lung cancer after smoking. However, the extent of public knowledge about radon is unclear. We systematically reviewed the epidemiologic literature in order to assay the public's understanding about radon and specifically, whether radon is known to cause lung cancer. Radon knowledge has most often been gauged via telephone and in-person responses to the question, "Have you heard about radon?" Our review of 20 such studies reveals that although many individuals have "heard about" radon, many segments of the population, particularly individuals younger than thirty and those with less education, do not know what radon is. Of those who have heard about radon, the majority of respondents in many studies did not know that radon causes lung cancer. Conversely, misinformation about radon is common; approximately 50% of respondents in many studies reported the erroneous belief that radon causes headaches. This suggests that the public has confused the effects of radon with those of carbon monoxide. Rates of radon testing and mitigation are correpondingly low and appear to reflect cognitive defense mechanisms by which individuals believe that their risks from radon are lower than the risks faced by others. Our review suggests that public information materials about radon require revision. Specifically, these should emphasize that radon causes lung cancer and that household carbon monoxide detectors do not detect it. Radon education provided by realtors at the time of residential home sales may be a promising venue to increase radon testing and remediation.

Aim: Environmental risk factors for chronic lymphocytic leukemia (CLL) have not been consistently identified. An etiologic role for ionizing radiation in CLL is controversial. Because most of the ionizing radiation to which individuals are exposed comes from radon at home, we examined CLL incidence rates in relation to residential radon levels. Methods: We used population-based rates for CLL for US states from 2007 to 2011 and measurements of residential radon made by the US Environmental Protection Agency. Results: Incidence rates for CLL were significantly correlated with residential radon levels among whites (both genders together and each gender separately; p < 0.005) and among blacks (p < 0.05). Conclusion: We speculate that radon increases CLL risk and that the mechanisms may be similar to those by which radon causes lung cancer.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with an unknown cause and invariably fatal outcome. We sought to evaluate a correlation between motor neuron disease (MND) mortality rates and residential radon levels that was previously reported for counties in the United Kingdom. We examined the relationships between age-adjusted MND mortality rates in U.S. states with residential radon levels, well water use, and other variables using structural equation modeling. We observed a significant correlation between MND mortality rates and radon levels. However, in structural equation models, radon did not have a significant, direct effect on MND mortality rates. Conversely, MND mortality rates were significantly and directly predicted by race and by the percentage of the population of each state using well water (p < 0.001 and p = 0.022). We observed similar, significant effects for well water use and MND mortality for males and females separately (p < 0.05). In conclusion, we hypothesize that the association of MND mortality rates with well water use reflects contamination of wells with Legionella, a bacterium common in well water that is known to cause neurologic disease. A Legionella hypothesis is a biologically plausible cause of ALS and suggests new avenues for etiologic research.

Ovarian cancer is the fifth leading cause of female cancer mortality in the U.S. and accounts for five percent of all cancer deaths among women. No environmental risk factors for ovarian cancer have been confirmed. We previously reported that ovarian cancer incidence rates at the state level were significantly correlated with the extent of pulp and paper manufacturing. We evaluated that association using county-level data and advanced geospatial methods. Specifically, we investigated the relationship of spatial patterns of ovarian cancer incidence rates with toxic emissions from pulp and paper facilities using data from the Environmental Protection Agency’s Toxic Release Inventory (TRI). Geospatial analysis identified clusters of counties with high ovarian cancer incidence rates in south-central Iowa, Wisconsin, New York, Pennsylvania, Alabama, and Georgia. A bivariate local indicator of spatial autocorrelation (LISA) analysis confirmed that counties with high ovarian cancer rates were associated with counties with large numbers of pulp and paper mills. Regression analysis of state level data indicated a positive correlation between ovarian cancer and water pollutant emissions. A similar relationship was identified from the analysis of county-level data. These data support a possible role of water-borne pollutants from pulp and paper mills in the etiology of ovarian cancer.

Aim: We previously reported that incidence rates for chronic lymphocytic leukemia (CLL) among US states are significantly correlated with levels of residential radon (RR). Because these correlations could be influenced by confounding and/or misclassification among large geographic units, we reinvestigated them using smaller geographic units that better reflect exposure and disease at the individual level. Methods: We examined the relationships between CLL and RR per county in 478 counties with publicly-available data. Results: After adjustment for ultraviolet radiation, a possible risk factor for CLL, county rates for CLL and RR were significantly correlated among males and females both together and separately (p < 0.0001). Conclusion: CLL is significantly associated with RR at the county level.