ABSTRACT
An exposure methodology was developed for the determination of the absorption rate of unattached radon progeny deposited in the human respiratory tract to blood. Twenty-one volunteers were exposed in a radon chamber during well-controlled aerosol and radon progeny conditions, with predominantly unattached radon daughters. Special efforts were made to restrict the dose to the volunteers to an absolute maximum of 0.08 mSv. Measurements of radon gas and radon progeny in blood samples of these volunteers indicated absorption half times of 20 min to 60 min. Former determinations, mainly performed with much larger aerosol particles of diameters between 100 nm and 1,000 nm, implied absorption half times around 10 h. This indicates that the absorption of radon decay products from ciliated airways into blood is dependent upon particle size and particle composition.
Subject(s)
Environmental Monitoring/methods , Radiometry/methods , Radon Daughters , Radon/pharmacokinetics , Respiratory System/metabolism , Absorption , Administration, Inhalation , Aerosols , Calibration , Dose-Response Relationship, Radiation , Humans , Sensitivity and SpecificityABSTRACT
Seven nose breathing and seven mouth breathing volunteers were exposed to atmospheres enriched with unattached radon progeny (218Po, 214Pb and 214Bi). The activity of these radionuclides deposited in the respiratory tract was measured in vivo after the exposures. The results of these measurements are in agreement with predictions calculated with the ICRP Publication 66 Human Respiratory Tract Model. Temporal analysis of the activity deposited in the heads of the volunteers leads to the conclusion that a significant amount of the deposited activity associated with particle diameters of about 1 nm is not subject to a fast transport to the gastrointestinal tract as generally reported for larger aerosol particles.
