Air Exchange Rate Impact on Actinon, Thoron, and Radon Activity Equilibrium Factor and Inhalation Fractional Equilibrium Factor Determination in Vapor Intrusion Risk and Dose Models
Exposure to the radioactive isotopes of radon are of high concern and, when present in vapor form, may pose a significant risk to humans in an indoor air environment. Understanding the radiometric and physical properties of radon radioisotopes are important for risk assessment. Little is known of the chemical properties of radon because of the short half-lives of all of its isotopes. Indoor air screening levels (SL) based on an annual target risk or dose limit were determined for the actinon (Rn-219), thoron (Rn-220), and radon (Rn-222) decay series. The SLs are based on inhalation and submersion in gas cloud exposure routes for residential and commercial settings. The SLs are analogous to preliminary remediation goals (PRGs) and dose compliance concentrations (DCCs), where the isotope-specific values are in units of activity concentration (activity per unit volume). If the concentration of a parent isotope of radon or its progeny is found to exceed the SL, then further action to ensure cleanup of the contaminant may be necessary. In residential and commercial settings, the SLs will vary based on the air exchange rate present. In this study, a computational method in MATLAB was developed to determine the impact of the air exchange rate on the activity equilibrium factor (Aeq) and the inhalation fractional equilibrium factor (Feq). Both factors are values that reflect the equilibrium concentrations of progeny to parent in the air. These factors have a direct impact on PRGs, DCCs, excess lifetime cancer risk, and annual dose; they are analyzed in subsequent sections along with applications in vapor intrusion risk and dose models.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1607007
- Report Number(s):
- ORNL/TM-2019/1269; TRN: US2103961
- Country of Publication:
- United States
- Language:
- English
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