A systematic review of radon concentrations and its lung cancer burden in Iran over two decades (2024-2000)

The second most common cause of lung cancer after smoking is radon which is a naturally occurring radioactive gas. Although the levels of radon have been recorded in some parts of Iran, the general health effect of radon remains unclear. A systematic review that was conducted in this study determined the level of indoor radon in Iranian provinces and approximated the burden of lung cancer as a result of this exposure using an accepted risk assessment model. An extensive search in both national and international databases revealed that 263 records were found, 45 of which were included in the study based on the PRISMA guidelines. The data were taken out of 60 cities in 18 provinces organized into nine geographic zones. Systematic evaluation was done on key modifying factors which included season, building materials, floor level, ventilation, and building age. Data on radon exposure were augmented with provincial lung cancer disability-adjusted life years (DALYs) of the Global Burden of Disease (GBD) study. The uncertainty in exposure and the exposure-response coefficient was also taken into consideration using Monte Carlo simulations. The radon-attributable lung cancer morbidity was estimated to be approximately 19,400 DALYs/year, which was equivalent to the population attributable fraction (PAF) of 10.6 (95 % CI: 8.1-13.3 %). The provincial PAFs were between 0.9 % and 44.3 % with the greatest burden observed in Tehran, Mazandaran and Khorasan-e-Razavi. In some regions, radon was responsible for more than 25 % (95 % CI: 20.1-31.2 %) of the lung cancer burden. These findings point to the existence of serious regional differences and the necessity of the immediate attention to radon monitoring, mitigation, and Governmental policies to prevent cancers and improve the safety of buildings in Iran.