A Study of the Relationship Among Radon, Thoron and Radioactive Aerosol Particle Distribution in PM2.5 Risk Areas in Kanchanaburi Province, Thailand

Tha Maka is the district with the highest incidence of cancer patients in Kanchanaburi province and is classified as a high-risk area for PM2.5 exposure due to the presence of many sugar factories. Most of the population is in agricultural occupation, leading to the annual burning of sugarcane and rice stubble to start new plantings, which is another cause of air pollution. This study aimed to investigate the correlation among radon, thoron, and airborne particles potentially implicated in lung cancer etiology, which focused on monitoring the concentrations of radon, thoron, and their progeny, as well as analyzing the distribution of particle sizes categorized into 10, 2.5, 1, 0.5, and less than 0.5 μm to assess possible health impacts or lung cancer risk factors. The findings indicated that indoor radon concentrations ranged from 13 to 81 Bq m−3, with a mean of 26.1 ± 11.9 Bq m−3, while indoor thoron concentrations varied from 2 to 52 Bq m−3, averaging 15.7 ± 10.8 Bq m−3. These levels are below the radiation dose limit recommended by the World Health Organization and the International Commission on Radiological Protection (ICRP). The total annual inhalation dose ranged from 0.44 to 2.02 mSv y−1, which is within the usual limits. The average annual effective doses from attached progeny were 0.83 mSv y−1 for radon and 0.57 mSv y−1 for thoron, both of which are regarded to be low. Consequently, based on all the findings, it may be assumed that radon, thoron, and their progeny may not be the primary contributors to lung cancer in the region. Nonetheless, while the mean value falls below the recommended thresholds established by the ICRP or WHO, it is indisputable that in certain regions, representing roughly 6.6% of the total area, the value surpasses the global average documented by the UNSCEAR. Furthermore, the aerosol particle size predominantly observed was less than 1 μm for radon and 0.5 μm for thoron, which is a significant factor that may influence the incidence of respiratory disorders. Nevertheless, as this study was conducted during the non-burning period, future research must be conducted during the burning season, using supplementary factors to acquire more thorough data.