Radon Levels Inside the Caves of Bohol Island, Philippines

Radon concentration in various workplaces, including tourist caves, remains higher than the recommended action level by the International Commission on Radiological Protection, which may pose a significant health risk. However, there has been no endeavor to investigate radon concentration in Philippine caves. This work investigated radon concentration inside Hinagdanan Cave, Batungay Cave, and Princess Manan-aw Cave using a passive radon detector. Radiation dose assessment and health risk estimation were also performed using the determined radon levels. The radon concentration inside these caves was above the safety limit (300 Bq/m3) and action limit (1000 Bq/m3) recommended by the World Health Organization and International Atomic Energy Agency, respectively. The dose assessment and evaluation do not exceed the annual dose limit prescribed by the Philippine Nuclear Research Institute. Lastly, the results of the lung cancer risk estimation exceed the recommended limit of 130 - 270 lung cancer cases per million people per year by the International Commission on Radiological Protection, except for Hinagdanan Cave. Radon mitigation must still be prioritized since the safety and action limit is exceeded, and administrative controls must be put in place to control radon exposure.