Deposition of {open_quotes}unattached{close_quotes} radon daughters in models of human nasal and oral airways

Conference · Thu Dec 31 04:00:00 EST 1992

OSTI ID:45161

Strong, J C ^[1]; Swift, D L ^[2]

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1. National Radiobiological Protection Board, Chilton, Didcot (United Kingdom)
2. Johns Hopkins Univ., Baltimore, MD (United States)

In order to estimate accurately an effective dose equivalent for exposures to radon daughters, knowledge of their deposition in the lung is required. However, the nose and mouth are effective filters for removing aerosol particles, especially in the range of sizes of {open_quotes}unattached{close_quotes} radon daughters. Therefore, it is equally important to have reliable data on deposition in this region of the respiratory tract. We will describe our work in studying nasal and oral deposition of {open_quotes}unattached{close_quotes} radon daughters in casts of these airways. Several hollow casts of adult and child nasal and oral airways were fabricated at The John Hopkins University from layers of Perspect{trademark} (an acrylic plastic). The shapes of the airway passages were obtained from nuclear magnetic resonance sectional images of healthy subjects. The casts were exposed to radon gas and daughters produced by flushing filtered air through a commercially available {sup 226}Ra source. The gas stream was drawn through a 1.4-L cylindrical tube to allow measurable growth of {sup 218}Po activity before it was passed through casts of both nasal passages or the oral cavity. The deposition of {open_quotes}unattached{close_quotes} {sup 218}Po was measured by comparing the activity collected on filters mounted in series and in parallel with a cast. Measurements were made at various flow rates (Q; 4 to 20 L min{sup -1}). The diffusion coefficient (D) of {sup 218}Po was measured each time the flow rate was changed, by replacing the cast with a stainless steel gauze screen and measuring the activity penetrating the screen. The measured diffusion coefficient ranged from 0.02 to 0.05 cm{sup 2} s{sup -1} and was found to vary with the residence time of {sup 218}Po in the growth tube. The deposition efficiency ({eta}) of {sup 218}Po measured in these casts ranged from 50 to 70%, and was similar to values we found previously, using casts of nasal and oral airways from cadavers.

• OSTI ID: 45161
• Report Number(s): CONF-901010--Pt.1
• Country of Publication: United States
• Language: English

Related Subjects

56 BIOLOGY AND MEDICINE
APPLIED STUDIES
BIOLOGICAL MODELS
DAUGHTER PRODUCTS
DEPOSITION
DOSE EQUIVALENTS
FLOW RATE
NOSE
ORAL CAVITY
POLONIUM 218
RADON
SPATIAL DOSE DISTRIBUTIONS