Field evaluation and health assessment of air cleaners in removing radon decay products in domestic environments

The United States Environmental Protection Agency suggested in 1988 that the possibility for high radon concentration exists in some houses. The inhalation and deposition of radon decay products in human lungs are recognized as producing a significant health risk. Air cleaners are one of the mitigative methods that remove radon decay products rather than radon itself. Currently, there are still uncertainties about the health benefit of air cleaners. Therefore, a better understanding of how air cleaners influence the behavior of radon decay products is needed.In this study, field evaluations of two types of air cleaners were conducted in three single-family houses. The measurements included radon concentration, particle number concentration, and concentration and size distribution of radon decay products. The influence on the behavior of radon decay products by various indoor particles both with and without the air cleaning systems was investigated. A room model was used to calculate the changes in the aerosol parameters caused by the operation of the air cleaners. Using the James dosimetric models (1989 and 1990), the changes in the hourly bronchial dose rate per Bq m$\sp{-3}$ radon for men, women, and children can be estimated for various domestic environments.The size distribution of radon decay products was bimodal under typical conditions. With particles produced from candle burning and vacuuming, an increase (20%) in the activity of radon decay products in the 1.5$-$50 nm size range was observed. Aerosols generated from cigarette smoldering and cooking are larger particles which shifted most of radon decay products to the "attached" mode. With the air filtration system operating, the size distribution of radon decay products has a major mode in the "unattached" fraction. During the particle generation period, the changes in the size distribution of radon decay products both with and without the air cleaners were very similar, with respect to the $\sp{218}$Po "unattached" fraction and the size range of the "attached" mode.The reductions in PAEC per Bq m$\sp{-3}$ radon varied from 30% to 85% with the air filtration system and 25%$-$40% with the electronic air cleaner in use. The reductions in the hourly dose rate per Bq m$\sp{-3}$ radon varied from 20% to 50% with the air filtration system and 10% to 25% for the electronic air cleaner. Both air cleaners, in a few cases, did increase the hourly dose rate. From this study, it is suggested that the air filtration system can be used when radon concentration is below 666 Bq m$\sp{-3}$ in the house. If radon concentration is below 450 Bq m$\sp{-3}$ indoors, the electronic air cleaner is recommended for use to reduce the radon risk.U of I OnlyETDs are only available to UIUC Users without author permissio