Abstract
Background: South Africa's rich mining history has left a lasting legacy of abandoned mine tailings, particularly in the Gauteng province. These tailings, often located near residential areas, pose significant health risks due to their potential to release harmful substances into the environment. One such substance of grave concern is radon, a naturally occurring radioactive gas that is produced by the decay of uranium found in rocks and soil. It can seep into buildings through cracks or other openings, leading to elevated indoor concentrations. Radon gas is colorless, tasteless, and odorless nature, making it undetectable without specialized detection methods. These characteristics make it a potential silent threat to human health. Exposure to high levels of radon has been linked to various health problems, most notably lung cancer. The World Health Organization (WHO) has classified radon as the second leading cause of lung cancer deaths globally. While lung cancer is the most significant health risk associated with radon, studies have also suggested potential links to leukaemia and chronic obstructive pulmonary disease (COPD).
South Africa's unique geological conditions and mining history make it particularly vulnerable to radon exposure. The presence of abandoned mine tailings, often situated near residential areas, increases the risk of elevated indoor radon levels. Additionally, the country's climate and building practices may influence radon concentrations in homes. Despite the potential health risks associated with radon exposure, limited research has been conducted on this issue in South Africa, particularly in the context of gold mine tailings. The aim of this study was to address this knowledge gap by quantifying radon concentration levels in residential houses near gold mine tailings, investigating the relationship between indoor radon exposure and the risk of lung cancer, identifying factors associated with high radon concentrations and lung cancer prevalence, and exploring the potential link between radon exposure and other health problems such as COPD and leukaemia. By addressing these research questions, this study will contribute to a better understanding of the health risks associated with radon exposure in South Africa and inform public health interventions to protect vulnerable populations.
Methods: This cross-sectional study investigated the potential health risks associated with indoor radon exposure in residential areas near gold mine tailings in Gauteng, South Africa. A comparative approach was employed, involving two groups: an exposed group residing within 0.1-2 km of gold mine tailings in Riverlea and an unexposed group residing in Orlando East, >
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2 km away from the tailings. A random sampling method was used to select participants from both groups, with a total sample size of 472 residents. The study focused on ground-level dwellings with direct earth contact, as these are more likely to be exposed to elevated radon levels. The data collection process included the administration of interviewer-administered structured questionnaires to participants. The questionnaires addressed socio-demographic characteristics, housing conditions, occupational and smoking histories, and health status. Additionally, indoor radon concentrations were measured using AlphaE radon monitors. Ethical approval was obtained from the University of Johannesburg's Research Ethics Committee, and informed consent was obtained from participants. The SPSS and STATA data analysis tools were used. Significance was determined by a confidence interval (CI) of 95% and a p-value of <0.05. Descriptive statistics were used to characterize the study population and compare demographic and socioeconomic factors between the two groups. Indoor radon concentrations were compared between exposed and unexposed groups. Bivariate and multivariate logistic regression analyses were employed to assess the association between indoor radon exposure and self-reported health outcomes, controlling for potential confounding factors such as smoking habits and occupational history. The effect modification of these factors on the relationship between radon exposure and health outcomes was also investigated. The annual effective dose due to inhaled radon was estimated using the UNSCEAR model. Radon map was created using GIS software to visualize radon levels across the study region and identify areas with potential elevated exposure risks.
Results: Of the 472 potential participants, 141 (29.9%) were unavailable or declined to participate, resulting in a 70.1% participation rate. The study included 331 individuals, with 166 from Riverlea and 165 from Orlando East. Most participants were female (60.4%), and the age distribution differed between the groups. In Orlando East, 42.4% of participants were aged 60–69, compared to 27.1% in Riverlea. The majority of dwellings in both communities were over 41 years old, with a slightly higher proportion of older dwellings in Orlando East (84.2%) compared to Riverlea (80.1%). Brick houses were the dominant dwelling type. Orlando East had a higher prevalence of metal roofing (92.1%) while Riverlea had a prevalence of asbestos roofing (77.7%). Concrete slabs were the predominant foundation type in both communities (Riverlea: 94.5%, Orlando East: 99.4%, respectively). Dwellings in Riverlea displayed a lower prevalence of cracks or openings in the foundation or floor (47.2%) compared to Orlando East (61.8%). Ventilation practices differed, with Riverlea residents opening windows and doors more frequently. A higher percentage of Riverlea residents spent more than 21 hours indoors
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per day. Prior radon testing was minimal in both communities. Dwellings near gold mine tailings had significantly higher average indoor radon concentrations (103.30 Bq/m3) compared to the control group (65.19 Bq/m3). Residential dwellings proximal to gold mine tailings were three times more likely to have indoor radon concentration beyond the WHO reference level of 100 Bq/m3. Furthermore, exposed group had estimated annual effective doses of 2.60 mSv/y compared to 1.64 mSv/y for the control group. Logistic regression analysis revealed a significant association between dwelling location and lung cancer risk (crude OR = 0.063, adjusted OR = 0.048), but no significant association between indoor radon exposure and lung cancer risk. In addition to indoor radon exposure, other confounding variables associated with increased risk of lung cancer, leukaemia and COPD were analysed in univariate and multivariate logistic regression. Active and passive smoking were not significantly associated with lung cancer risk. Occupational exposure to carcinogens emerged as a significant risk factor for lung cancer (OR = 7.545). For leukaemia, a significant association was observed between indoor radon exposure and the risk of leukaemia (OR = 1.067, adjusted OR = 1.071). Passive smoking was marginally associated with an increased risk of leukaemia (adjusted OR = 1.293), but occupational exposures was not significantly associated with increased risk of leukaemia. For COPD, no significant association was observed between indoor radon exposure and COPD risk. Active and passive smoking were not significantly associated with COPD risk. However, occupational exposure was significantly associated with an increased risk of COPD (OR = 1.243).
Conclusion: This study highlighted a concerning association between proximity to gold mine tailings and elevated indoor radon levels. Furthermore, this study found a positive association between residing proximal gold mine tailings and self-reported lung cancer risk. Public health interventions prioritizing residential dwellings near gold mine tailings are crucial. Educational campaigns and financial assistance for radon mitigation systems in high-risk dwellings are recommended. Residents near gold mine tailings are encouraged to ensure continuous natural ventilation through frequent opening of windows and doors. In regions impacted by gold mine tailings, it is crucial to implement efficient indoor radon mitigation measures and promote public consciousness about the health hazards linked to indoor radon exposure. There is a need to motivate affected residents to adopt proactive steps to lower indoor radon concentrations, including enhancing ventilation practices. Future research should focus on conducting long-term radon measurements to accurately capture radon level variations over time. Additionally, incorporating objective health assessments, such as medical records and diagnostic tests, in
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future studies will provide a more comprehensive understanding of the health risks associated with indoor radon exposure and help inform effective public health interventions. Lastly, longitudinal study designs, like cohort and case-control studies, should be employed to establish a definitive causal relationship between indoor radon exposure and other health outcomes, particularly for population residing proximal radioactive sites such as gold mine tailings.