# The Relationship between Radon and Geology: Sources, Transport and Indoor Accumulation
## 3 Health Risks Associated with Radon Exposure  
The World Health Organization (WHO) recognizes radon as a leading cause of lung cancer worldwide, and exposure to radon is a significant public health concern [140]. While there are several sources of radon exposure, indoor radon is the most concerning due to the potential for high concentrations in confined spaces [141]. It is estimated that up to 14% of lung cancer deaths worldwide are caused by radon exposure, highlighting the importance of addressing this issue for public health [142]. The WHO recommends that national authorities implement policies and programs to reduce exposure to radon in indoor environments, including testing and mitigation strategies [143]. Education and awareness campaigns are also important to increase public knowledge and promote action to reduce exposure [144]. Currently, the literature identifies the following potential impacts on human health resulting from exposure to radon:  
* The relationship between radon exposure and lung cancer is well established [145]. When radon is inhaled, its radioactive particles can deposit in the lining of the lungs [146]. As radon and its radioactive descendants, such as \({}^{218}\)Po and \({}^{214}\)Po, decay, they emit radiation that can damage the DNA of lung cells and lead to the formation of tumours [147]. Epidemiological studies have shown that radon exposure is the second leading cause of lung cancer, after smoking [148]. Smokers exposed to radon have an even greater risk of developing lung cancer [140]. The study by [PERSON] et al. (1994) provides a comprehensive analysis of the risk of lung cancer associated with residential radon exposure [149]. This study was conducted in Sweden and included 586 women and 774 men, aged between 35 and 74 years, who were diagnosed with lung cancer between 1980 and 1984. For comparison purposes, 1380 female controls and 1467 male controls were studied. The levels of radon measured in the residences of the study participants followed a log-normal distribution, with geometric and arithmetic means of 1.6 and 2.9 pCi/L, respectively. The results showed that the risk of lung cancer increased in relation to both estimated cumulative and time-weighted radon exposure. Compared with time-weighted average radon concentrations of up to 1.4 pCi/L, the relative risk was 1.3 (95 percent confidence interval, 1.1 to 1.6) for average radon concentrations of 3.8 to 10.8 pCi/L, and it increased to 1.8 (95 percent confidence interval, 1.1 to 2.9) at concentrations exceeding 10.8 pCi/L. An important aspect of this study was the interaction between radon exposure and smoking in relation to lung cancer. The interaction exceeded additivity and approached a multiplicative effect, suggesting that smoking may increase the risk of lung cancer associated with radon exposure. The study by [PERSON] et al. (2005) was a collaborative analysis of individual data from 13 case-control studies on residential radon and lung cancer, encompassing nine European countries [150]. The sample included 7148 cases of lung cancer and 14,208 controls. The findings showed that the average measured radon concentration in the residences of the control group was 97 Bq\(\cdot\)m\({}^{-3}\), with 11% measuring over 200 Bq\(\cdot\)m\({}^{-3}\) and 4% measuring over 400 Bq\(\cdot\)m\({}^{-3}\). For the lung cancer cases, the average concentration was 104 Bq\(\cdot\)m\({}^{-3}\). The research found a significant correlation between radon exposure and lung cancer risk. The risk of lung cancer increased by 8.4% (with a 95% confidence interval between 3.0% and 15.8%) for each 100 Bq m\({}^{-3}\) increase in measured radon concentration. This corresponds to an increase of 16% (5% to 31%) per 100 Bq m\({}^{-3}\) increase in usual radon, i.e., after correction for the dilution caused by random uncertainties in measuring radon concentrations.