Activity exhalation rates

The method for the exhalation rate measurements is based on the same activated charcoal/TLD combinations as the dosimeter for measurements of indoor Rn-222. Details on the method is published elsewhere. (Stranden et al, 1985.)... 

In Table I results of Rn-226 activity measurements cn geological samples are shewn together with measurements cn Rn exhalation rates from the sanples. The exhalation rates varies considerably with the moisture content of material. The exhalation rate is lew for dry samples and when the moisture content increases, the exhalation rate increases until it reaches a plateau. When the moisture content increases further, a rapid increase in radon exhalation occur. When the saturation level of moisture is reached, the exhalation rate drops dramatically. The exhalation rates given in Table I are obtained by assuming that the most probable moisture content is whithin the plateau of exhalation rate/moisture curve. (Stranden et al, 1984, Stranden et al, 1984a). 

Table I. Activity concentrations and exhalation rates from sanples...

Material No Of sanples Activity concentration of Ra-226 (Bq kg l) Exhalation rates from sanples + (Bq h l kg l)... 

Building material Ra-226 activity concentration (Bq kg-1) Range and mean Exhalation rate per unit mass and unit Ra-226 activity concentration (Bqh lkg l)/(Bqkg l) Estimated range of exhalation rate frcm typical walls (Bqh l m 2) ++... 

Based on Ra-226 activity concentration, typical wall thickness and exhalation rate measurements frcm samples and walls. (Stranden and Berteig, 1980 Stranden 1983, Stranden et al, 1984 Stranden et al, 1984a.)... 

Figure 6 displays exhalation rate curves versus time for the sample in Figure 2, with the leakage factory as the variable parameter. Large leaks make the final steady-state exhalation rate deviate less from the free exhalation rate, in accordance with Equation 4. It must be remembered, however, that the radon activity accumulating in the outer volume is dependent on y, the exhalation rate is only the strength of the radon source feeding this volume. 

Humans are exposed to natural radiation soil is a major source of external and internal exposure of radiation. The external exposure from the soil is associated with gamma radiation and internal exposure with radon inhalation. Exposures of radiation derived from soil are different in each region. The aim of this study is to evaluate radionuclides content, Rn exhalation rates, radium equivalent activity and hazard indices in soil samples around Institute de Pesquisas Energeticas e Nucleares (IPEN) facilities. 

Table 2 presents the results obtained for Rn exhalation rate, radium equivalent activities and external and internal hazard indices from soil around IPEN. 

Table 2 exhalation rate (Bq m s ), radium external and internal hazard indices equivalent activities (CRa,eg) nd ... 

All the results obtained for radon exhalation rate, radiiun equivalent activity and external and internal hazard indices indicate that the exposure around IPEN facilities due to the radioactive discharges is negligible. 

The metabolism of chloroform is well understood. Approximately 50% of an oral dose of 0.5 grams of chloroform was metabolized to carbon dioxide in humans (Fry et al. 1972). Metabolism was dose-dependent, decreasing with higher exposure. A first-pass effect was observed after oral exposure (Chiou 1975). Approximately 38% of the dose was converted in the liver, and < 17% was exhaled unchanged from the lungs before reaching the systemic circulation. On the basis of pharmacokinetic results obtained in rats and mice exposed to chloroform by inhalation, and of enzymatic studies in human tissues in vitro, in vivo metabolic rate constants (V, 3,C =15.7 mg/hour/kg, = 0.448 mg/L) were defined for humans (Corley et al. 1990). The metabolic activation of chloroform to its toxic intermediate, phosgene, was slower in humans than in rodents. 

Vinylidene fluoride is taken up rapidly via the pulmonary route in rats, but at equilibrium the mean concentration (by volume) in rats was only 23% of that in the gaseous phase. Metabolism proceeded very slowly and was saturable at exposure concentrations of about 260 mg/m Its maximum rate was 1% that of vinyl chloride and less than 20% that of vinyl fluoride there has been a report of an increase in the urinary excretion of fluoride in exposed rats. No alkylating intermediate was demonstrated after passage through a mouse-liver microsomal system. However, vinylidene fluoride inhibits mixed-function oxidase activity in vitro and, like similar halogenated compounds that are transformed to reactive metabolites, it alters rat intermediary metabolism, leading to acetone exhalation (lARC, 1986). 

Numerous measurements of 222Rn exhalation have been reported. Global continental means of 15, 16 and 25 mBq m-2 s-1 have been calculated by Israel (1951), Wilkening et al. (1972) and Turekian et al. (1977), respectively. Higher rates of emission are found in regions of recent tectonic activity, and where the uranium content of the topmost rocks or soil is enhanced. 

When healthy volunteers were exposed by inhalation to 100 or 400 ppm tetrahydrofuran in air, the percentage of expired tetrahydrofuran was 25-35%. The elimination half-life of tetrahydrofuran was 30 min in individuals exposed to 200 ppm for 3h. Some tetrahydrofuran is absorbed in the nasal cavity due to its solubility and inspiratory flow rate. Tetrahydrofuran uptake in the nasal tissue is dependent on its reaction with tissue substrates. Some tetrahydrofuran can be metabolized in the nasal cavity. Tetrahydrofuran blood concentrations were higher at 1 h postexposure than immediately after cessation of exposure. In vitro studies indicated that tetrahydrofuran was first hydroxylated by microsomal enzymes. High concentrations (lO molH ) of tetrahydrofuran inhibited the in vitro activity of rat hepatic cytochrome P450 by 80%. Tetrahydrofuran has been noted to enhance the toxic action of a number of compounds and stimulate the rapid absorption of reactive metabolites. Some of the tetrahydrofuran is excreted in the exhaled breath, while the various metabolites of tetrahydrofuran are excreted in the urine. 

Imprecise and slow control cannot be tolerated during the demands of exercise. Excess COj must be removed at a rate high enough that it doesn t poison the body. Exercise breathing control becomes active in both inhalation and exhalation directions. 

The human oral cavity is potentially coimected to the nasal cavity by way of the buccopharynx (oropharynx), pharynx, and nasopharynx [1,2]. Under those circumstances in which this potential connection is open, the air movement of an exhalation that exits from the anterior nates (nostrils) can acquire odorants from the oral cavity and move them through the nasal cavity. If these odorants, while in the nasal cavity, reach the olfactory mucosa at a flow rate and concentration [3,4] that allow penetration to olfactory receptor neurons [5] and activation of these receptors such that sufficient central nervous system (CNS) responses develop, retronasal olfaction may occur. A limitation to the present understanding of retronasal olfaction is the absence of empirical or numerical models of retronasal odorant transport in adult humans. Such models have been published for orthonasal olfaction via the anterior nares [4,6] but are not presently available for retronasal olfaction (experimental airflow and odorant uptake analysis is in progress PW Scherer, personal communication, October 2002). 

Aerotech II, whereas it was 82% following inhalation from the Spira nebulizer. The measured exhaled activity from the Spira was 48% and from the Aerotech II 57%. The differences in clearance rate might possibly be due to the larger aerosol particles produced by the Spira nebulizer. The authors conclude that liposomal formulations are generally retained within the lung longer than most soluble drugs. 

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