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

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.

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.

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.

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.

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.