Residential radon exposure and adult acute leukaemia

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.

Overview of radon gas in groundwater around the world: Health effects and treatment technologies

The natural radioactive decay of uranium in rocks and soils gives rise to the presence of radon in groundwater. The existence of radon in groundwater at activity levels way higher than the reference limits set by US-EPA and WHO was widely covered in literature. The exposure to elevated levels of radon in ground and drinking water have been reported in literature to cause adverse health impacts. The aim of the present paper is to give an overview of radon gas in groundwater followed by the safe limits suggested by international organizations and agencies such as US-EPA and WHO. The paper also discusses the health effects associated with the exposure to radon levels and the estimation of the annual effective dose through ingestion and inhalation. This is followed by the radon levels around the world as well as the corresponding annual effective doses reported in literature. The determination techniques of radon levels in water covered in literature such as liquid scintillation counting, gamma-ray spectrometry and emanometry were also discussed and reviewed in the present work. Next, the paper sheds light on the most frequently used treatment techniques such as aeration, adsorption, filtration as well as biological techniques and evaluates their efficiency in mitigating radon levels in water. The paper also highlights the main precautions and future mitigation plans for radon in groundwater as well as delved onto future research perspectives of radon. It was found out that the type of rock played a key role in determining the radon levels. For instance, granitic rock types were reported to contribute to the elevation in the groundwater radon levels due to their characteristic permeability as a result of the formed fractures as well as their natural incorporation of high levels of uranium. Some of the reported radon levels in groundwater in literature were way higher than the guidelines set by the World Health Organization (WHO) for drinking water and US-EPA alternative higher maximum contaminant level. This review paper could be of importance to researchers working on the evaluation as well as the treatment of radon gas in water as it will provide a critical and state of the art review on radon gas in groundwater.

A Study on Geographic Correlation between Indoor Radon Exposure and Leukemia Incidence in Canada

ABSTRACT

In Canada, leukemia is diagnosed at a rate of 15 cases per 100,000 persons and accounts for about 3% of all new primary cancers. In this study, geographical correlation between residential radon exposure and leukemia incidence was investigated at a provincial level with more accurate long-term radon measurement data in 21,330 homes and 10-y (2000-2009) age standardized incidence rates per 100,000 population for various subtypes of leukemia. The analyses showed that the incidence rate of non-Hodgkin lymphoma is statistically significantly correlated with average indoor radon (222Rn) concentration for Canadian females (p = 0.01210) but not for males. At a provincial level, the association between average indoor radon level and chronic lymphocytic leukemia incidence rate is statistically significant (p = 0.0167), and the correlation is somewhat stronger for females (p = 0.0043). No correlation was found between indoor radon exposure and any other subtypes of leukemia evaluated in this study.

Challenging the concept of de novo acute myeloid leukemia: Environmental and occupational leukemogens hiding in our midst

Myeloid neoplasms like acute myeloid leukemia (AML) originate from genomic disruption, usually in a multi-step fashion. Hematopoietic stem/progenitor cell acquisition of abnormalities in vital cellular processes, when coupled with intrinsic factors such as germline predisposition or extrinsic factors such as the marrow microenvironment or environmental agents, can lead to requisite pre-leukemic clonal selection, expansion and evolution. Several of these entities have been invoked as "leukemogens." The known leukemogens are numerous and are found in the therapeutic, occupational and ambient environments, however they are often difficult to implicate for individual patients. Patients treated with particular chemotherapeutic agents or radiotherapy accept a calculated risk of therapy-related AML. Occupational exposures to benzene, dioxins, formaldehyde, electromagnetic and particle radiation have been associated with an increased risk of AML. Although regulatory agencies have established acceptable exposure limits in the workplace, accidental exposures and even ambient exposures to leukemogens are possible. It is plausible that inescapable exposure to non-anthropogenic ambient leukemogens may be responsible for many cases of non-inherited de novo AML. In this review, we discuss the current understanding of leukemogens as they relate to AML, assess to what extent the term "de novo" leukemia is meaningful, and describe the potential to identify and characterize new leukemogens.

Health Effects of Radon Exposure

Radon is a naturally occurring radioactive material that is formed as the decay product of uranium and thorium, and is estimated to contribute to approximately half of the average annual natural background radiation. When inhaled, it damages the lungs during radioactive decay and affects the human body. Through many epidemiological studies regarding occupational exposure among miners and residential exposure among the general population, radon has been scientifically proven to cause lung cancer, and radon exposure is the second most common cause of lung cancer after cigarette smoking. However, it is unclear whether radon exposure causes diseases other than lung cancer. Media reports have often dealt with radon exposure in relation to health problems, although public attention has been limited to a one-off period. However, recently in Korea, social interest and concern about radon exposure and its health effects have increased greatly due to mass media reports of high concentrations of radon being released from various close-to-life products, such as mattresses and beauty masks. Accordingly, this review article is intended to provide comprehensive scientific information regarding the health effects of radon exposure.

γ-H2AX/53BP1/pKAP-1 foci and their linear tracks induced by in vitro exposure to radon and its progeny in human peripheral blood lymphocytes

The biodosimetric information is critical for evaluating the human health hazards caused by radon and its progeny. Here, we demonstrated that the formation of phosphorylated histone variant H2AX (γ-H2AX), p53-binding protein 1 (53BP1) and phosphorylated KRAB-associated protein 1 (pKAP-1) foci and their linear tracks in human peripheral blood lymphocytes (HPBLs) in vitro exposed to radon and its progeny were dependent on the cumulative absorbed dose of radon exposure but was unrelated to the concentration of radon. Among them, γ-H2AX foci and its linear tracks were the most sensitive indicators with the lowest estimable cumulative absorbed dose of 1.74 mGy from their linear dose-response curves and sustained for 12 h after termination of radon exposure. In addition, three types of foci showed an overdispersed non-Poisson distribution in HPBLs. The ratios of pKAP-1/γ-H2AX foci co-localization, 53BP1/γ-H2AX foci co-localization and 53BP1/pKAP-1 foci co-localization were significantly increased in HPBLs exposed to radon while they were unrelated to the cumulative dose of radon exposure, suggesting that γ-H2AX, pKAP-1 and 53BP1 play an important role in the repair of heterochromatic double-strand breaks. Altogether, our findings provide an experimental basis for estimating the biological dose of internal α-particle irradiation from radon and its progeny exposure in humans.

Establishment of a γ-H2AX foci-based assay to determine biological dose of radon to red bone marrow in rats

The biodosimetric information is critical for assessment of cancer risk in populations exposed to high radon. However, no tools are available for biological dose estimation following radon exposure. Here, we established a γ-H2AX foci-based assay to determine biological dose to red bone marrow (RBM) in radon-inhaled rats. After 1–3 h of in vitro radon exposure, a specific pattern of γ-H2AX foci, linear tracks with individual p-ATM and p-DNA-PKcs foci, was observed, and the yield of γ-H2AX foci and its linear tracks displayed a linear dose-response manner in both rat peripheral blood lymphocytes (PBLs) and bone-marrow lymphocytes (BMLs). When the cumulative doses of radon inhaled by rats reached 14, 30 and 60 working level months (WLM), the yields of three types of foci markedly increased in both PBLs and BMLs, and γ-H2AX foci-based dose estimates to RBM were 0.97, 2.06 and 3.94 mGy, respectively. Notably, BMLs displayed a more profound increase of three types of foci than PBLs, and the absorbed dose ratio between BMLs and PBLs was similar between rats exposed to 30 and 60 WLM of radon. Taken together, γ-H2AX foci quantitation in PBLs is able to estimate RBM-absorbed doses with the dose-response curve of γ-H2AX foci after in vitro radon exposure and the ratio of RBM- to PBL-absorbed doses in rats following radon exposure.

Health effects of radon: a review of the literature

PURPOSE

Radon is natural radioactive noble gas that can be found in soil, water, outdoor and indoor air. Exposure to radon accounts for more that 50% of the annual effective dose of natural radioactivity. The purpose of the current review is to summarize recent literature and evaluate the weight of evidence on the adverse health effects of radon.

CONCLUSIONS

Radon is an established human lung carcinogen based on human epidemiological data supported by experimental evidence of mutagenesis studies in cell culture and laboratory animals. Extrapolation from cohort studies on miners suggested that radon is the second leading cause of lung cancer death after tobacco smoke. The majority of studies on the relationship between radon and other types of cancers showed weak or no association. Low levels of radon can be found in drinking water; however, radon released during water usage adds small quantities to indoor radon concentration. Studies showed that the risk of stomach cancer and other gastrointestinal malignancies from radon in drinking water is small. Studies of the genetic and cytogenetic effects of indoor radon yielded equivocal results; while radon exposure in miners induces gene mutations and chromosomal aberrations. Numerous in vitro cytogenetic studies demonstrated that radon induces different types of genetic and cytogenetic damage that is likely to play a role in radon lung carcinogenesis.

Incidence of leukemia, lymphoma, and multiple myeloma in Czech uranium miners: a case-cohort study

OBJECTIVE

Uranium miners are chronically exposed to low levels of radon and its progeny. We investigated whether radon exposure is associated with increased incidence of leukemia, lymphoma, or multiple myeloma in this population.

DESIGN

We conducted a retrospective case-cohort study in 23,043 uranium miners and identified a total of 177 incident cases of leukemia, lymphoma, and myeloma. Detailed information on occupational radon exposure was obtained for the cases and a randomly selected subcohort of 2,393 subjects. We used the proportional hazards model with power relative risk (RR) function to estimate and test the effects of cumulative radon exposures on incidence rates.

RESULTS

Incidence of all leukemia combined and chronic lymphocytic leukemia (CLL) alone was positively associated with cumulative radon exposure. The RR comparing high radon exposure [110 working level months (WLM) ; 80th percentile] to low radon exposure (3 WLM ; 20th percentile) was 1.75 [95% confidence interval (CI) , 1.10-2.78 ; p = 0.014] for all leukemia combined and 1.98 (95% CI, 1.10-3.59 ; p = 0.016) for CLL. Myeloid leukemia and Hodgkin lymphoma were also associated with radon, but RRs were not statistically significant. There was no apparent association of radon with either non-Hodgkin lymphoma or multiple myeloma. Exposure to radon and its progeny was associated with an increased risk of developing leukemia in underground uranium miners. CLL, not previously believed to be radiogenic, was linked to radon exposure.

Adult myeloid leukaemia and radon exposure: a Bayesian model for a case-control study with error in covariates

The possible association between radon exposure in dwellings and adult myeloid leukaemia had been explored in an Italian province by a case-control study. A total of 44 cases and 211 controls were selected from death certificates file. No association had been found in the original study (OR = 0.58 for > 185 vs 80 < or = Bq/cm). Here we reanalyse the data taking into account the measurement error of radon concentration and the presence of missing data. A Bayesian hierarchical model with error in covariates is proposed which allows appropriate imputation of missing values. The general conclusion of no evidence of association with radon does not change, but a negative association is not observed anymore (OR = 0.99 for > 185 vs 80 < or = Bq/cm). After adjusting for residential house radon and gamma radiation, and for the multilevel data structure, geological features of the soil is associated with adult myeloid leukaemia risk (OR = 2.14, 95 per cent Cr.I. 1.0-5.5).

Leukemia in childhood and adolescence and exposure to ionizing radiation in homes built from uranium-containing alum shale concrete

Concerns in Sweden about indoor radon around 1980 prompted measurements of gamma-radiation from the facades of houses to identify those constructed of uranium-containing alum shale concrete, with potentially high radon concentrations. To evaluate any possible risk of acute lymphocytic leukemia from exposure to elevated gamma-radiation in these homes, we identified the acute lymphocytic leukemia cases less than 20 years of age in Sweden during 1980-1989 as well as eight controls per case from the population registry, matching on age, gender, and county. Using the existing measurements, exposure was assessable for 312 cases and 1,418 controls from 151 properly measured municipalities. A conditional logistic odds ratio of 1.4 (95% confidence interval = 1.0-1.9) was obtained for those ever having lived in alum shale concrete houses, with the average exposure exceeding 0.10 microsieverts per hour. Comparing those who ever lived in alum shale concrete houses (divided by higher and lower annual average exposure) with those who never lived in such houses, we found a weak dose-response relation. The results suggest some risk of acute lymphocytic leukemia from indoor ionizing radiation among children and young adults.

Radon exposure and the risk of leukemia: a review of epidemiological studies

Since the 1990's, several authors estimated that radon inhalation may deliver a small amount of irradiation to the red bone marrow, and consequently may increase the risk of leukemia in humans. The objective of this review is to conduct a critical analysis of epidemiologic results currently available concerning the relationship between radon exposure and the risk of leukemia. Nineteen ecological studies, six miner cohort studies, and eight case-control studies published between 1987 and 2000 are included in this review. The limitations associated with each of these studies are discussed. The results of the ecological studies are relatively concordant and suggest an association between radon concentrations and the risk of leukemia at a geographic level. But these ecological studies present important limitations, and some are only crude analyses. Moreover, the results of the cohort and case-control studies, based on individual data, do not show any significant association between radon exposure and leukemia risk. Our conclusion is that the overall epidemiologic results currently available do not provide evidence for an association between radon exposure and leukemia.