Date of Degree
PhD (Doctor of Philosophy)
Occupational and Environmental Health
R. William Field
The primary goal of this PhD research was to obtain critical information needed to further calibrate the novel glass-based retrospective radon detectors (RRDs) by characterizing the quantitative relationship between radon gas concentrations, the surface-deposited activities of various radon progeny, the airborne dose rate, and various residential environmental factors through both actual field measurements and Monte-Carlo simulation.
Radon and radon progeny concentrations were measured, from May 2005 to May 2007, in 38 Iowa houses occupied by either smokers or nonsmokers. The investigation took into account several important indoor environmental factors, which have crucial influences on the radon progeny deposition process in homes. The long-term (3 months) surface-deposited radon progeny by species and implanted 210Po were measured using a RRD. During the 3 months, the short-term (3-7 days) airborne radon progeny by species and bimodal size fraction were measured using a recently developed active detector. Both passive and active detectors are solid state nuclear track detectors. Airborne dose rates were calculated from unattached and attached potential alpha energy concentrations (PAECs) based on both Porstendörfer's effective dose conversion factor and that of James. Correlation analysis and multiple linear regression analysis were applied to analyze both field study results and Monte-Carlo simulation study results. Temporal and spatial variations among airborne dose rates and surface-deposited radon progeny were also investigated in actual field settings. Overall, deposited radon progeny were useful in predicting airborne dose rate in addition to the radon gas concentration. The occurrence of smoking was the most crucial environmental factor influencing the deposition process. In addition, other environmental factors were identified that served as useful covariates predicting airborne dose rates by smoking status.
The results from our current study will greatly aid the future resolution of the final reanalysis of the lung cancer risks for the Iowa Radon Lung Cancer Study (IRLCS) based on radon progeny exposure estimates obtained from RRD measurements. In addition, the results of this study will be used as the basis for a large-scale pooled analysis of the Iowa and Missouri Residential Radon Studies, both of which incorporated the use of the glass-based detectors within their study designs.
Copyright 2008 Kainan Sun