DOMESTIC RADON EXPOSURE AND CHILDHOOD LEUKAEMIA AND LYMPHOMA: A POPULATION-BASED STUDY IN CANADA

Indoor radon exposure: A systematic review of radon-induced health risks and evidence quality using GRADE approach

Background

Radon (Rn) is a radioactive gas with well-established carcinogenic properties. It is a significant contributor to natural background ionizing radiation exposure, accounting for over 50 % of human exposure. Prolonged exposure to radon gas has been conclusively linked to various health issues such as lung cancer, leukemia, and Chronic Obstructive Pulmonary Diseases (COPD). Despite this, there is a scarcity of comprehensive studies examining the quality of evidence establishing an association between indoor radon exposure and these health problems.

Objective

We performed a systematic review of peer-reviewed research articles to explore the current evidence on the potential association between residential radon exposure and human health, specifically focusing on lung cancer, COPD, and leukemia.

Methods

A comprehensive search was conducted on PubMed and Google Scholar using MeSH terms and keywords (residential radon, radon AND lung cancer, radon AND COPD, radon AND leukemia). The inclusion criteria focused on studies that analyzed the link between residential radon exposure and lung cancer, leukemia and COPD. We searched for peer-reviewed studies published from 2010 to 2024. Studies carried out in occupational settings were not considered. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework to select relevant studies. Reviewers independently collected data, resolving disagreements through discussion. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to evaluate evidence quality, and the study was registered with PROSPERO, CRD42024550735.

Results

The evidence indicating an associative or causal link between indoor radon and lung cancer was found to be of high quality or conclusive, particularly with stronger support from case-control studies. The findings for COPD and leukemia were inconclusive, indicating that additional research is necessary to establish a definitive link between residential radon exposure and these health outcomes. These associations was deemed moderate or inconclusive primarily due to methodological shortcomings, conflicting findings and the prevalence of weak study designs and poor exposure data. The existing evidence on the potential connection between residential radon exposure and the risk of COPD and leukemia is currently limited. In order to definitively confirm or disprove this association, more studies are needed. Further research is crucial to elucidate these relationships and to guide the development of effective public health interventions.

Conclusion

The review found that the association between radon exposure and lung cancer was consistent with existing scientific knowledge. However, the evidence for association between indoor radon exposure and COPD was inconclusive. Additionally, evidence linking indoor radon exposure to leukemia was uncertain. Future research should use more robust study designs (cohort and case control studies) and directly measure long-term radon levels to investigate the potential association between residential radon exposure and COPD and leukemia.

Domestic radon exposure and childhood cancer risk by site and sex in 727 counties in the United States, 2001-2018

BACKGROUND

Childhood cancer has few established risk factors and environmental influences are underexplored. This ecologic study investigated the association between domestic radon exposure and childhood cancer risk in a large sample of United States (U.S.) counties.

METHODS

Monthly ZIP code-level basement radon estimates from a geographic machine learning model were aggregated annually to counties, analyzed as continuous and dichotomized (cut point: 74 Bq/cubic meter (Bq/m3) or 2.0 picocuries/L (pCi/L)) versions, and lagged by one year. Annual county-level counts of sex- and site-specific (all, leukemia, brain and central nervous system [CNS], and other sites) incident cancer diagnoses among those 0-19 years from 2001 to 2018 were obtained from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program database. Sex- and site-specific counts were modeled as zero-inflated Poisson distributions in a Bayesian spatiotemporal framework and sequentially adjusted for random and fixed confounder effects.

RESULTS

In 727 counties across 14 states, the average population aged 0-19 years was 41,599 people at baseline. Results from fully adjusted spatiotemporal statistical models indicated 1.05 (95% credible interval, CrI: 1.00, 1.09) times higher relative risks (RRs) of leukemia among both sexes and a RR of 1.06 (95%CrI: 1.00, 1.12) in males from a 50 Bq/m3 (1.35 pCi/L) increase in radon concentration the year prior. For radon exposures ≥74 Bq/m3 (2.00 pCi/L) the year prior, RRs were 1.08 (95%CrI: 1.02, 1.15) for both sexes and 1.12 (95%CrI: 1.04, 1.22) for females. No associations were found with other cancer sites or sexes from prior year radon exposures.

CONCLUSIONS

County-level childhood leukemia risk in both sexes were associated with average radon levels below U.S. Environmental Protection Agency guidelines recommending mitigation (148 Bq/m3 or 4.00 pCi/L). These findings warrant further investigation using population-based and individual-level study designs.

Radon exposure and potential health effects other than lung cancer: a systematic review and meta-analysis

Context and objective

To date, lung cancer is the only well-established health effect associated with radon exposure in humans. To summarize available evidence on other potential health effects of radon exposure, we performed a comprehensive qualitative and quantitative synthesis of the available literature on radon exposure and health effects other than lung cancer, in both occupational and general populations.

Method

Eligible studies published from January 1990 to March 2023, in English and French languages, were identified in PubMed, ScienceDirect, Scopus, ScieLo and HAL. In the meta-analysis, we estimated average weighted standardized incidence ratios (metaSIR), standardized mortality ratios (metaSMR), and risk ratio (metaRR) per 100 unit (Bq/m3 or Working level Month) increase in radon exposure concentration by combining estimates from the eligible studies using the random-effect inverse variance method. DerSimonian & Laird estimator was used to estimate the between-study variance. For each health outcome, analyses were performed separately for mine workers, children, and adults in the general population.

Results

A total of 129 studies were included in the systematic review and 40 distinct studies in the meta-analysis. For most of these health outcomes, the results of the meta-analyses showed no statistically significant association, and heterogeneity was only present among occupational studies, especially between those included in the metaSIR or metaSMR analyses. However, the estimated exposure-risk associations were positive and close to the statistical significance threshold for: lymphohematological cancer incidence in children (metaRR = 1.01; 95%CI: 1.00-1.03; p = 0.08); malignant melanoma mortality among adults in the general population (metaRR = 1.10; 95%CI: 0.99-1.21; p = 0.07); liver cancer mortality among mine workers (metaRR = 1.04; 95%CI: 1.00-1.10; p = 0.06); intestine and rectal cancer mortality combined among mine workers (metaRR = 1.02; 95%CI: 1.00-1.04; p = 0.06).

Conclusion

Although none of the exposure-risk associations estimated in the meta-analyses reached statistical significance, the hypothesis that radon may have other health effects apart from lung cancer could not be ruled-out and call for additional research. Larger and well-designed studies are needed to further investigate this question.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023474542, ID: CRD42023474542.

Assessment of contamination level of radon (222Rn) in drinking water around Tulsishyam geothermal area and Savarkundla fault in Saurashtra, India

This study aimed to estimate radon concentrations in groundwater and surface water to evaluate radon (222Rn) contamination in drinking water within the Amreli region of Saurashtra, Gujarat, India. Water samples from 84 sites, covering about 3000 km2, were analyzed using the RAD7 device from Durridge Instruments. Samples were collected in 250 ml radon-tight bottles. Radon concentrations ranged from 0.1 to 13.6 Bq/L, averaging 4.52 Bq/L. At three sites (P9, P29, P35), radon levels exceeded the USEPA limit of 11.1 Bq/L. P9 and P29 are near the Tulsishyam geothermal area, while P35 is close to the Savarkundla fault. Geothermal fluids in Tulsishyam may facilitate radon migration, and swarm-type earthquakes near Savarkundla could also contribute to radon migration. Concurrently, physicochemical parameters like Potential of Hydrogen (pH) and Total Dissolved Solid (TDS) were measured, with no significant correlation found between radon levels and these parameters. Samples were taken from tube wells with depths ranging from 105 to 750 feet, averaging 359 feet. A strong and significant correlation (0.83) was observed between radon concentration and water depth. Health risks from radon exposure were assessed by estimating annual effective dose rates for different age groups through ingestion and inhalation. In some instances, the annual effective dose rate surpassed the WHO-recommended value of 100 µSv/year. However, in most instances, the presence of radon in the water does not indicate a significant radiological risk.

Environmental radon, fracking wells, and lymphoma in dogs

BACKGROUND

Multicentric lymphoma (ML) in dogs resembles non-Hodgkin lymphoma (NHL) in humans. Human NHL is associated with multiple environmental exposures, including to radon and volatile organic compounds (VOCs).

HYPOTHESIS/OBJECTIVES

The objective of this study was to determine whether ML in dogs was associated with environmental radon or proximity to horizontal oil and drilling (fracking), a source of VOC pollution.

METHODS

We identified dogs from the Golden Retriever Lifetime Study that developed ML (n = 52) along with matched controls (n = 104). Dog home addresses were categorized by Environmental Protection Agency radon zone and average residential radon by county, as well as by distance from fracking and associated wastewater wells.

RESULTS

We found no significant differences in county level radon measurements. Individual household radon measurements were not available. There was no difference in residential proximity to active fracking wells between dogs with ML and unaffected dogs. While dogs with ML lived closer to wastewater wells (123 vs 206 km; P = .01), there was no difference in the percentage of cases vs controls that lived in close proximity (20 km) to a fracking well (11.5% for cases, 6.7% for controls; OR 1.81, 95% CI 0.55 to 5.22; P = .36), or a wastewater well (6.7% for cases, 4.4% for controls; P > .99).

CONCLUSIONS AND CLINICAL IMPORTANCE

These data suggest that more proximate sources of chemical exposures need to be assessed in dogs with ML, including measurements of individual household radon and household VOC concentrations.

Environmental Pollution and Risk of Childhood Cancer: A Scoping Review of Evidence from the Last Decade

The long-term effects of environmental pollution have been of concern as several pollutants are carcinogenic, potentially inducing a variety of cancers, including childhood cancer, which is a leading cause of death around the world and, thus, is a public health issue. The present scoping review aimed to update and summarize the available literature to detect specific environmental pollutants and their association with certain types of childhood cancer. Studies published from 2013 to 2023 regarding environmental pollution and childhood cancer were retrieved from the PubMed database. A total of 174 studies were eligible for this review and were analyzed. Our search strategy brought up most of the articles that evaluated air pollution (29%) and pesticides (28%). Indoor exposure to chemicals (11%), alcohol and tobacco use during pregnancy (16%), electromagnetic fields (12%), and radon (4%) were the subjects of less research. We found a particularly high percentage of positive associations between prenatal and postnatal exposure to indoor (84%) and outdoor (79%) air pollution, as well as to pesticides (82%), and childhood cancer. Positive associations were found between leukemia and pesticides and air pollution (33% and 27%); CNS tumors and neuroblastoma and pesticides (53% and 43%); and Wilms tumor and other rare cancers were found in association with air pollution (50%). Indoor air pollution was mostly reported in studies assessing several types of cancer (26%). Further studies are needed to investigate the mechanisms underlying the potential associations between indoor/outdoor air pollution and pesticide exposure with childhood cancer risk as more preventable measures could be taken.

An overview on the relationship between residential radon and lung cancer: what we know and future research

We aim to provide an overview of the research available on indoor radon and lung cancer, with a special focus on Spanish investigations. Early studies on underground miners established the link between radon and lung cancer, which was later confirmed for the general population by residential case-control studies. Spain contributed with extensive evidence, including 5 multicentric, hospital-based, case-control studies in the last 30 years, exploring diverse aspects, such as radon's effect on never-smokers, molecular pathways linking radon exposure to lung cancer risk, survival rates, mortality burden, and occupational exposure. There is a well-established causal association between radon with lung cancer. Despite pioneering research performed in our country by the Galician Radon Laboratory, particularly on driver genes, the evidence on the potential molecular pathways which makes radon a carcinogen is sparse. Also, relevant questions on the potential association of radon exposure with the induction of other diseases are still pending.

A review of studies of childhood cancer and natural background radiation

PURPOSE

The projected existence and magnitude of carcinogenic effects of ionizing radiation at low doses and low-dose rates is perhaps the most important issue in radiation protection today. Studies of childhood cancer and natural background radiation have the potential to throw direct light on this question, into a dose range below a few tens of mSv. This paper describes the studies that have been undertaken and their context, discusses some problems that arise and summarizes the present position.

CONCLUSIONS

Many such studies have been undertaken, but most were too small to have a realistic chance of detecting the small effects expected from such low doses, based on risk projections from higher exposures. Case-control or cohort studies are to be preferred methodologically to ecological studies but can be prone to problems of registration/participation bias. Interview-based studies of the requisite size would be prohibitively expensive and would undoubtedly also run into problems of participation bias. Register-based studies can be very large and are free of participation bias. However, they need to estimate the radiation exposure of study subjects using models rather than individual measurements in the homes of those concerned. At present, no firm conclusions can be drawn from the studies that have been published to date. Further data and perhaps pooled studies offer a way forward.

Radiation-related health hazards to uranium miners

Concerns on health effects from uranium (U) mining still represent a major issue of debate. Any typology of active job in U mines is associated with exposure to U and its decay products, such as radon (Rn), thorium (Th), and radium (Ra) and its decay products with alpha-emission and gamma radiation. Health effects in U miners have been investigated in several cohort studies in the USA, Canada, Germany, the Czech Republic, and France. While public opinion is particularly addressed to pay attention to the safety of nuclear facilities, health hazard associated with mining is poorly debated. According to the many findings from cohort studies, the most significant positive dose-response relationship was found between occupational U exposure and lung cancer. Other types of tumors associated with occupational U exposure are leukemia and lymphoid cancers. Furthermore, it was found increased but not statistically significant death risk in U miners due to cancers in the liver, stomach, and kidneys. So far, there has not been found a significant association between U exposure and increased cardiovascular mortality in U miners. This review tries to address the current state of the art of these studies.