Smoking Modifies the Association Between Radon Exposure and Incident Ischemic Stroke: The REGARDS Study.

BACKGROUND: Exposure to radon has been linked to lung cancer and other lung diseases. Although biologically plausible, research of residential radon exposure in relation to stroke risk is scarce. METHODS: Study participants were from the REGARDS (Reasons for Geographic and Racial Differences in Stroke) cohort (n=30 239), which consisted of male and female non-Hispanic Black and White adults aged 45 and older. After excluding participants with baseline stroke and transient ischemic attack, and missing information on exposure and outcome of interest, the final sample size was 26 950. The primary outcome was time to the first ischemic stroke through September 30, 2020. County-level radon measures from Lawrence Berkeley National Laboratory were linked to each participant based on their geocoded residential history. We used Cox proportional hazards regression models with a time-dependent exposure to estimate hazard ratios and 95% CIs for the association. RESULTS: After controlling for potential confounding factors including demographic, lifestyle, clinical variables, and PM2.5, radon exposure was significantly associated with incident ischemic stroke among never-smokers (hazard ratio, 1.39 [95% CI, 1.01-1.90]) but not ever-smokers. The results were generally consistent in the sensitivity analysis when using radon measures from state/Environmental Protection Agency residential radon survey. CONCLUSIONS: Findings from this study suggest that the association between residential radon exposure and incidence of ischemic stroke varies by smoking status and may be prominent in never-smokers. Further studies incorporating indoor-radon measures are needed to confirm these findings.

Juxtaposition of intensive agriculture, vulnerable aquifers, and mixed chemical/microbial exposures in private-well tapwater in northeast Iowa.

In the United States and globally, contaminant exposure in unregulated private-well point-of-use tapwater (TW) is a recognized public-health data gap and an obstacle to both risk-management and homeowner decision making. To help address the lack of data on broad contaminant exposures in private-well TW from hydrologically-vulnerable (alluvial, karst) aquifers in agriculturally-intensive landscapes, samples were collected in 2018-2019 from 47 northeast Iowa farms and analyzed for 35 inorganics, 437 unique organics, 5 in vitro bioassays, and 11 microbial assays. Twenty-six inorganics and 51 organics, dominated by pesticides and related transformation products (35 herbicide-, 5 insecticide-, and 2 fungicide-related), were observed in TW. Heterotrophic bacteria detections were near ubiquitous (94 % of the samples), with detection of total coliform bacteria in 28 % of the samples and growth on at least one putative-pathogen selective media across all TW samples. Health-based hazard index screening levels were exceeded frequently in private-well TW and attributed primarily to inorganics (nitrate, uranium). Results support incorporation of residential treatment systems to protect against contaminant exposure and the need for increased monitoring of rural private-well homes. Continued assessment of unmonitored and unregulated private-supply TW is needed to model contaminant exposures and human-health risks.

Prevalence of neonicotinoid insecticides in paired private-well tap water and human urine samples in a region of intense agriculture overlying vulnerable aquifers in eastern Iowa.

A pilot study among farming households in eastern Iowa was conducted to assess human exposure to neonicotinoids (NEOs). The study was in a region with intense crop and livestock production and where groundwater is vulnerable to surface-applied contaminants. In addition to paired outdoor (hydrant) water and indoor (tap) water samples from private wells, urine samples were collected from 47 adult male pesticide applicators along with the completions of dietary and occupational surveys. Estimated Daily Intake (EDI) were then calculated to examine exposures for different aged family members. NEOs were detected in 53% of outdoor and 55% of indoor samples, with two or more NEOs in 13% of samples. Clothianidin was the most frequently detected NEO in water samples. Human exposure was ubiquitous in urine samples. A median of 10 different NEOs and/or metabolites were detected in urine, with clothianidin, nitenpyram, thiamethoxam, 6-chloronicotinic acid, and thiacloprid amide detected in every urine samples analyzed. Dinotefuran, imidaclothiz, acetamiprid-N-desmethyl, and N-desmethyl thiamethoxam were found in ≥70% of urine samples. Observed water intake for study participants and EDIs were below the chronic reference doses (CRfD) and acceptable daily intake (ADI) standards for all NEOs indicating minimal risk from ingestion of tap water. The study results indicate that while the consumption of private well tap water provides a human exposure pathway, the companion urine results provide evidence that diet and/or other exposure pathways (e.g., occupational, house dust) may contribute to exposure more than water contamination. Further biomonitoring research is needed to better understand the scale of human exposure from different sources.

Does protracted radon exposure play a role in the development of dementia?

Radon is a ubiquitous radioactive gas that decays into a series of solid radioactive decay products. Radon, and its decay products, enter the human body primarily through inhalation and can be delivered to various tissues including the brain through systemic circulation. It can also reach the brain by neuronal pathways via the olfactory system. While ionizing radiation has been suggested as a risk factor of dementia for decades, studies exploring the possible role of radon exposure in the development of Alzheimer's Diseases (AD) and other dementias are sparse. We systematically reviewed the literature and found several lines of evidence suggesting that radon decay products (RDPs) disproportionally deposit in the brain of AD patients with selective accumulation within the protein fractions. Ecologic study findings also indicate a significant positive correlation between geographic-level radon distribution and AD mortality in the US. Additionally, pathologic studies of radon shed light on the potential pathways of radon decay product induced proinflammation and oxidative stress that may result in the development of dementia. In summary, there are plausible underlying biological mechanisms linking radon exposure to the risk of dementia. Since randomized clinical trials on radon exposure are not feasible, well-designed individual-level epidemiologic studies are urgently needed to elucidate the possible association between radon (i.e., RDPs) exposure and the onset of dementia.

Telehealth Utilization Is Associated with Lower Risk of Discontinuation of Buprenorphine: a Retrospective Cohort Study of US Veterans.

OBJECTIVE: Treatment for opioid use disorder (OUD) may include a combination of pharmacotherapies (such as buprenorphine) with counseling services if clinically indicated. Medication management or engagement with in-person counseling services may be hindered by logistical and financial barriers. Telehealth may provide an alternative mechanism for continued engagement. This study aimed to evaluate the association between telehealth encounters and time to discontinuation of buprenorphine treatment when compared to traditional in-person visits and to evaluate potential effect modification by rural-urban designation and in-person and telehealth combination treatment. METHODS: A retrospective cohort study of Veterans diagnosed with OUD and treated with buprenorphine across all facilities within the Veterans Health Administration (VHA) between 2008 and 2017. Exposures were telehealth and in-person encounters for substance use disorder (SUD) and mental health, treated as time-varying covariates. The primary outcome was treatment discontinuation, evaluated as 14 days of absence of medication from initiation through 1 year. RESULTS: Compared to in-person encounters, treatment discontinuation was lower for telehealth for SUD (aHR: 0.69; 95%CI: 0.60, 0.78) and mental health (aHR: 0.69; 95%CI: 0.62, 0.76). There was no evidence of effect modification by rural-urban designation. Risk of treatment discontinuation appeared to be lower among those with telehealth only compared to in-person only for both SUD (aHR: 0.48, 95%CI: 0.37, 0.62) and for mental health (aHR: 0.46; 95%CI: 0.33, 0.65). CONCLUSIONS: As telehealth demonstrated improved treatment retention compared to in-person visits, it may be a suitable option for engagement for patients in OUD management. Efforts to expand services may improve treatment retention and health outcomes for VHA and other health care systems.

Occurrence of neonicotinoids and sulfoxaflor in major aquifer groups in Iowa.

A statewide assessment of neonicotinoids in groundwater was conducted among a sample of public water supply wells in Iowa from October 2017 to August 2018. Samples from all the state's major aquifer groups were initially collected from 118 wells in 69 counties. Subsets of 55 untreated samples and 45 paired pre- and post-treatment samples were then collected in summer 2018, post-planting season for primarily corn and soybeans, to assess seasonal differences and the efficacy of treatment. Samples prepared using solid phase extraction were analyzed using LC/MS/MS for six neonicotinoids: acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, thiamethoxam, and a sulfoximine (i.e., sulfoxaflor). Clothianidin was the most frequently detected (34%, max: 13.4 ng/L), followed by thiamethoxam (14.4%, max: 20.6 ng/L), imidacloprid (13%, max: 2.3 ng/L), and dinotefuran (0.1%, max: 1.4 ng/L). Alluvial aquifers (unadjusted odds ratio (UOR) = 14.1; 95% CI (5.4-36.9), p=<0.0001), wells with confining layers <15 m (UOR = 13.5, 95% CI (4.8-38.4), p=<0.0001), and less than 19.4 m in depth (UOR = 20.0; 95% CI (6.5-58.0), p=<0.0001) had the greatest risk for contamination. In vulnerable aquifers, neonicotinoids were detected in 62% of winter and 46% of summer samples, with winter samples over 3 times (UOR = 3.2; 95% CI (1.2-8.8), p = 0.02) more likely to have at least two neonicotinoids detected. In 55 public water supply systems, the median concentrations of clothianidin (p = 0.6), imidacloprid (p = 0.7), and thiamethoxam (p = 0.7) were unchanged following treatment. These results suggest that neonicotinoid contamination may be present year-round in treated drinking water from vulnerable groundwater sources and represent a source of human exposure.

A critical review on the potential impacts of neonicotinoid insecticide use: current knowledge of environmental fate, toxicity, and implications for human health.

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.

The unintended impact of smoking-risk information on concerns about radon: A randomized controlled trial.

OBJECTIVE: Health communications are often viewed by people with varying levels of risk. This project examined, in the context of radon risk messages, whether information relevant to high-risk individuals can have an unintended influence on lower-risk individuals. Two studies assessed whether information about lung cancer risk from smoking reduced concerns about lung cancer risk from radon among nonsmokers. METHOD: American nonsmokers viewed radon messages that varied in what they communicated about smoking's effect on lung cancer risk. Study 1 used a 4-arm factorial, randomized, controlled design in which smoking information was included or excluded from messages assembled from 2 existing radon pamphlets. Study 2 used a 3-arm parallel, randomized, controlled design in which a new radon message excluded smoking information, described smoking as a lung cancer risk, or also described smoking's synergistic effect with radon. RESULTS: In Study 1, the inclusion of smoking information reduced nonsmokers' (n = 462) concern-related reactions to possible radon exposure. In Study 2, nonsmokers' (n = 583) concern-related reactions were reduced in both smoking-information conditions; intentions to test their home for radon and perceived importance of testing were reduced in the synergistic condition. CONCLUSION: People reading health-risk information contextualize their risk relative to the risk of others. For people at midlevel risk, concern and related reactions prompted by a health message may be dampened when the message includes information about others who are more at risk. In the case of radon and smoking risks, the inclusion of smoking information can reduce the impact that radon messages have on nonsmokers. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Comparative survey of outdoor, residential and workplace radon concentrations.

This study investigated radon concentrations in above-ground (i.e. first floor) workplace in Missouri and compared them with above-ground radon concentrations in nearby homes and outdoor locations. This study also examined the potential utility of using home and outdoor radon concentrations to predict the radon concentration at a nearby workplace (e.g. county agencies and schools). Even though workplace radon concentrations were not statistically different from home radon concentrations, the radon concentration at a particular home, or outdoor location, was a poor predictor of the radon concentration at a nearby workplace. Overall, 9.6 and 9.9 % of homes and workplace, respectively, exhibited radon concentrations of ≥148 Bq m(-3). Because of the percentage of workplace with elevated radon concentrations, the results suggest that additional surveys of workplace radon concentrations are needed, especially in areas of high radon potential, to assess the contribution of workplace radon exposure to an individual's overall radon exposure.

Unsuspected exposure to beryllium: potential implications for sarcoidosis diagnoses.

Exposure to Beryllium (Be) can cause sensitization (BeS) and chronic beryllium disease (CBD) in some individuals.  Even relatively low exposures may be sufficient to generate an asymptomatic, or in some cases a symptomatic, immune response. Since the clinical presentation of CBD is similar to that of sarcoidosis, it is helpful to have information on exposure to beryllium in order to reduce misdiagnosis. The purpose of this pilot study is to explore the occurrence of Be surface deposits at worksites with little or no previous reported use of commercially available Be products.  The workplaces chosen for this study represent a convenience sample of businesses in eastern Iowa. One hundred thirty-six surface dust samples were collected from 27 businesses for analysis of Be. The results were then divided into categories by the amount of detected Be according to U.S. Department of Energy guidelines as described in 10 CFR 850.30 and 10 CFR 850.31. Overall, at least one of the samples at 78% of the work sites tested contained deposited Be above the analytical limit of quantitation (0.035 µg beryllium per sample).  Beryllium was detected in 46% of the samples collected. Twelve percent of the samples exceeded 0.2 µg/100 cm² and 4% of the samples exceeded a Be concentration of 3 µg/100 cm². The findings from this study suggest that there may be a wider range and greater number of work environments that have the potential for Be exposure than has been documented previously.  These findings could have implications for the accurate diagnosis of sarcoidosis.

A comparison of winter short-term and annual average radon measurements in basements of a radon-prone region and evaluation of further radon testing indicators.

The primary objective of this study was to investigate the temporal variability between basement winter short-term (7 to 10 d) and basement annual radon measurements. Other objectives were to test the short-term measurement's diagnostic performance at two reference levels and to evaluate its ability to predict annual average basement radon concentrations. Electret ion chamber (short-term) and alpha track (annual) radon measurements were obtained by trained personnel in Iowa residences. Overall, the geometric mean of the short-term radon concentrations (199 Bq m) was slightly greater than the geometric mean of the annual radon concentrations (181 Bq m). Short-term tests correctly predicted annual radon concentrations to be above the 148 Bq m action level 88% of the time and above a 74 Bq m level 98% of the time. The short-term and annual radon concentrations were strongly correlated (r = 0.87, p < 0.0001). The foundation wall material of the basement was the only significant factor to have an impact on the absolute difference between the short-term and annual measurements. The findings from this study provide evidence of a substantially lower likelihood of obtaining a false negative result from a single short-term test in a region with high indoor radon potential when the reference level is lowered to 74 Bq m.

Utility of death certificate data in predicting cancer incidence.

BACKGROUND: Studies often rely on death certificates to identify cancer occurrence. This research assessed the death certificate's ability to reflect cancer incidence and factors that influence agreement with cancer registry data. METHODS: This study compared death certificates to cancer incidence data for an occupational cohort of 1,795 deceased workers who were registered by the Iowa Cancer Registry (ICR) between 1973 and 2005. Logistic regression models examined the effects of factors such as survival time, age at diagnosis, and gender on the odds of agreement between death certificate and incidence data. RESULTS: Death certificates under-reported cancer incidence by 10-100%, depending on site. A 1-year increase in survival decreased the odds of agreement between death certificate and ICR data by 18%. Younger and female workers had increased odds of agreement. CONCLUSIONS: Death certificates can be useful predictors of cancer incidence, particularly for diseases with shorter survival and among subjects diagnosed earlier in life.

Occupational and environmental causes of lung cancer.

Because tobacco smoking is a potent carcinogen, secondary causes of lung cancer are often diminished in perceived importance. The goal of this review is to describe the occurrence and recent findings of the 27 agents currently listed by the International Agency for Research on Cancer (IARC) as lung carcinogens. The IARC's updated assessments of lung carcinogens provide a long-overdue resource for consensus opinions on the carcinogenic potential of various agents. Supplementary new information, with a focus on analytic epidemiologic studies that has become available since IARC's most recent evaluation, are also discussed.

Prevalence of beryllium sensitization among Department of Defense conventional munitions workers at low risk for exposure.

OBJECTIVE: To estimate the prevalence of beryllium sensitization among former and current Department of Defense workers from a conventional munitions facility. METHODS: Participants were screened by using Beryllium Lymphocyte Proliferation Test. Those sensitized were offered clinical evaluation for chronic beryllium disease. RESULTS: Eight (1.5%) of 524 screened workers were found sensitized to beryllium. Although the confidence interval was wide, the results suggested a possibly higher risk of sensitization among workers exposed to beryllium by occasional resurfacing of copper-2% beryllium alloy tools compared with workers with the lowest potential exposure (odds ratio = 2.6; 95% confidence interval, 0.23-29.9). CONCLUSIONS: The findings from this study suggest that Department of Defense workers with low overall exposure to beryllium had a low prevalence of beryllium sensitization. Sensitization rates might be higher where higher beryllium exposures presumably occurred, although this study lacked sufficient power to confirm this.

Room model based Monte Carlo simulation study of the relationship between the airborne dose rate and the surface-deposited radon progeny.

The quantitative relationships between radon gas concentration, the surface-deposited activities of various radon progeny, the airborne radon progeny dose rate, and various residential environmental factors were investigated through a Monte Carlo simulation study based on the extended Jacobi room model. Airborne dose rates were calculated from the unattached and attached potential alpha-energy concentrations (PAECs) using two dosimetric models. Surface-deposited (218)Po and (214)Po were significantly correlated with radon concentration, PAECs, and airborne dose rate (p-values <0.0001) in both non-smoking and smoking environments. However, in non-smoking environments, the deposited radon progeny were not highly correlated to the attached PAEC. In multiple linear regression analysis, natural logarithm transformation was performed for airborne dose rate as a dependent variable, as well as for radon and deposited (218)Po and (214)Po as predictors. In non-smoking environments, after adjusting for the effect of radon, deposited (214)Po was a significant positive predictor for one dose model (RR 1.46, 95% CI 1.27-1.67), while deposited (218)Po was a negative predictor for the other dose model (RR 0.90, 95% CI 0.83-0.98). In smoking environments, after adjusting for radon and room size, deposited (218)Po was a significant positive predictor for one dose model (RR 1.10, 95% CI 1.02-1.19), while a significant negative predictor for the other model (RR 0.90, 95% CI 0.85-0.95). After adjusting for radon and deposited (218)Po, significant increases of 1.14 (95% CI 1.03-1.27) and 1.13 (95% CI 1.05-1.22) in the mean dose rates were found for large room sizes relative to small room sizes in the different dose models.

Recent advances in understanding the biomolecular basis of chronic beryllium disease: a review.

In this review we summarize the work conducted over the past decade that has advanced our knowledge of pulmonary diseases associated with exposure to beryllium that has provided a molecular-based understanding of the chemistry, immunopathology, and immunogenetics of beryllium toxicity. Beryllium is a strong and lightweight metal that generates and reflects neutrons, resists corrosion, is transparent to X-rays, and conducts electricity. Beryllium is one of the most toxic elements on the periodic table, eliciting in susceptible humans (a) an allergic immune response known as beryllium sensitization (BeS); (b) acute beryllium disease, an acutely toxic, pneumonitis-like lung condition resulting from exposure to high beryllium concentrations that are rarely seen in modern industry; and (c) chronic beryllium disease (CBD) following either high or very low levels of exposure. Because of its exceptional strength, stability, and heat-absorbing capability, beryllium is used in many important technologies in the modern world. In the early 1940s, beryllium was recognized as posing an occupational hazard in manufacturing and production settings. Although acute beryllium disease is now rare, beryllium is an insidious poison with a latent toxicity and the risk of developing CBD persists. Chronic beryllium disease-a systemic granulomatous lung disorder caused by a specific delayed immune response to beryllium within a few months to several decades after exposure-has been called the "unrecognized epidemic". Although not a disease in itself, BeS, the innate immune response to beryllium identified by an abnormal beryllium lymphocyte proliferation test result, is a population-based predictor of CBD. Genetic susceptibility to CBD is associated with alleles of the major histocompatibility gene, human leukocyte antigen DP (HLA-DP) containing glutamic acid at the 69th position of the beta chain (HLA-DPbeta-E69). Other genes are likely to be involved in the disease process, and research on this issue is in progress. The current Occupational Safety & Health Administration permissible exposure limit of 2 microg/m3 has failed to protect workers from BeS/CBD. As a safe exposure limit that will not lead to BeS or CBD has not yet been determined, the realization that the risk of CBD persists has led to a renaissance in research on the effects of the metal on human health. Current data support further reductions in exposure levels to help minimize the incidence of CBD. Steps that would directly impact both the power of epidemiologic studies and the cost of surveillance would be to develop and validate improved screening and diagnostic tests, and to identify more genetic factors that affect either sensitization or disease process. The major focus of this review is the recent research on the cellular and molecular basis of beryllium sensitization and disease, using a multidisciplinary approach of bioinorganic chemistry and immunology. First we present a historical background of beryllium exposure and disease, followed by occurrence of beryllium in the environment, toxicokinetics, biological effects, beryllium lung disease, and other human health effects.

Field investigation of surface-deposited radon progeny as a possible predictor of the airborne radon progeny dose rate.

The quantitative relationships between radon gas concentration, the surface-deposited activities of various radon progeny, the airborne radon progeny dose rate, and various residential environmental factors were investigated through actual field measurements in 38 selected Iowa houses occupied by either smokers or nonsmokers. Airborne dose rate was calculated from unattached and attached potential alpha energy concentrations (PAECs) using two dosimetric models with different activity-size weighting factors. These models are labeled Pdose and Jdose, respectively. Surface-deposited 218Po and 214Po were found significantly correlated to radon, unattached PAEC, and both airborne dose rates (p < 0.0001) in nonsmoking environments. However, deposited 218Po was not significantly correlated to the above parameters in smoking environments. In multiple linear regression analysis, natural logarithm transformation was performed for airborne dose rate as the dependent variable, as well as for radon and deposited 218Po and 214Po as predictors. An interaction effect was found between deposited 214Po and an obstacle in front of the Retrospective Reconstruction Detector (RRD) in predicting dose rate (p = 0.049 and 0.058 for Pdose and Jdose, respectively) for nonsmoking environments. After adjusting for radon and deposited radon progeny effects, the presence of either cooking, usage of a fireplace, or usage of a ceiling fan significantly, or marginally significantly, reduced the Pdose to 0.65 (90% CI 0.42-0.996), 0.54 (90% CI 0.28-1.02), and 0.66 (90% CI 0.45-0.96), respectively. For Jdose, only the usage of a ceiling fan significantly reduced the dose rate to 0.57 (90% CI 0.39-0.85). In smoking environments, deposited 218Po was a significant negative predictor for Pdose (RR 0.68, 90% CI 0.55-0.84) after adjusting for long-term 222Rn and environmental factors. A significant decrease of 0.72 (90% CI 0.64-0.83) in the mean Pdose was noted, after adjusting for the radon and radon progeny effects and other environmental factors, for every 10 additional cigarettes smoked in the room. A significant increase of 1.71 in the mean Pdose was found for large room size relative to small room size (90% CI 1.08-2.79) after adjusting for the radon and radon progeny effects as well as other environmental factors. Fireplace usage was found to significantly increase the mean Pdose to 1.71 (90% CI 1.20-2.45) after adjusting for other factors.

Blind testing of commercially available short-term radon detectors.

A sample of commercially available, charcoal adsorption type, short-term radon detectors was blind tested under controlled laboratory conditions in order to obtain a "snapshot" of the accuracy and precision of the detectors. The results of the controlled exposures were then compared to a previous field study of the same type of commercially available radon detectors. Radon detectors, purchased from seven different commercial vendors, were exposed to a reference (222)Rn gas concentration at the U.S. Environmental Protection Agency's (EPA) Radon Chamber located at the Radiation and Indoor Environments National Laboratory in Las Vegas, Nevada. EPA Test 1 was performed under a controlled simulated field exposure paralleling, to the extent possible, the previous actual field exposure conditions. A second controlled exposure, EPA Test 2, was performed under a relatively steady state of (222)Rn gas concentration, at the same temperature, but a more moderate relative humidity. In the previous field setting evaluation of detectors, five out of six companies tested did not pass the accuracy guideline (all individual relative errors < or =25%) established during the EPA's former Radon Measurement Proficiency Program (EPA-RMPP). As compared to the field test, the detectors in this study generally exhibited better accuracy and precision. Not surprisingly, it appeared temporal fluctuations in radon concentrations and increased humidity had a negative influence on the accuracy and precision of detectors for some companies. The inability of three out of seven companies to meet former EPA-RMPP guidelines for accuracy, even under ideal exposure conditions (constant temperature, humidity, and radon concentration), highlights the importance of blind testing commercially available radon detectors. Furthermore, the consistent over-reporting or under-reporting trends in the overall results for all three tests suggest a potentially widespread systematic bias for the individual companies that merits further investigation. It is unknown if this one-time "snapshot" represents the overall reliability of commercially available charcoal-based radon detectors. Nonetheless, the findings suggest the need for improved vigilance to assure that the public can rely on commercially available radon detectors to make an informed decision whether or not to perform additional testing or to mitigate.