Immunological and Respiratory Effects in a Healthy Rodent Model after Inhalation of Low and Regulated Levels of Radon

Radon gas is a naturally occurring substance and contributes significantly to the public background radiation dose. It is widely accepted that radon has harmful effects, being considered the second leading cause of lung cancer after smoking; however, studies also indicate that exposure to low doses may have beneficial effects. As the debate continues, robust animal models are essential to investigate the effects of low-dose radon exposure on biological systems. In this study, we examined the temporal effects of low and regulated levels of radon (400 Bq/m3 and 1,000 Bq/m3) on the lungs of a healthy in vivo rat model using our specially designed radon chamber. Rats were housed with or without radon gas in the chamber for durations of 18 h, 90 h, 2 × 90 h, or 4 × 90 h. After exposure, a tracheotomy under anesthesia was performed, and respiratory function was assessed using a small animal ventilator. Rats were humanely euthanized, tissues were removed, and immunological and biological outcomes were evaluated. Our results demonstrate that the inhalation of radon and its decay products results in subsequent molecular activation in this system, establishing a model for low-level radon exposure in a healthy animal, and suggest that low and regulated levels of radon exposure for up to 4 weeks do not lead to biologically significant negative health outcomes. This model will facilitate further investigation into the role of radon in cancer development and its potential therapeutic applications in alleviating symptoms of inflammatory conditions.