Inhaled “dose

Ground radiation is from deposited radioactive particles. The deposition rate from a radioactive cloud without rain (dry deposition) is so low that the ground radiation dose is about the same as the inhalation dose. A heavy rain, however, may wash out enough particles from the plume to make ground radiation the dominant contributor to the total dose in a limited area. Rain will also attenuate radiation by leaching the radioactivity to be shielded by the soil and by moving it to streams for further removal. 

Personal exposure Predictions of exposure of occupants to airborne contaminants for risk assessment, inhaled doses, or time-integrated concentration values. 

With given contaminant source and sink schedules and outdoor concentrations, concentration evolutions over time can be determined for the individual zones on the basis of the calculated airflow rate values per time step. Further postprocessing allows the determination of accumulated values such as air change rate or concentration histograms (see the later example) or inhaled dose values. 

Maximum concentrations, integrated exposure values, inhaled dose values... 

Inhaled doses of trichloroethylene are metabolized extensively in humans. The percentage of the dose metabolized has been reported to be between 40% and 75% of the retained dose (Bartonicek 1962 Ertle et al. 1972 Fernandez et al. 1977 Kimmerle and Eben 1973a, 1973b Monster et al. 1976, 1979 Muller et al. 1972, 1974, 1975 Nomiyama and Nomiyama 1971, 1974a, 1974b, 1977 Ogata etal. 1971 Satoetal. 

Soucek and Vlachova 1960 Vesterberg and Astrand 1976). None of these studies provided evidence of saturation of trichloroethylene metabolism in humans. The data of Nomiyama and Nomiyama (1977) and of Ikeda (1977) indicated that the liver s capacity for metabolizing inhaled doses of trichloroethylene is... 

Doses of chlorpyrifos in human volunteers were also estimated using physical measurements. Air sampling was conducted in order to estimate the inhalation dose to each volunteer. Dislodgeable residues were also measured throughout the study to estimate the dermal contribution to total dose. Finally, hand rinses were conducted on each volunteer immediately following the 4-hr activity period to assess the potential contribution to total dose from hand exposure and to estimate an oral dose to a crawling child. 

By dividing the amount of absorbed chlorpyrifos by the individual body weights, the inhalation dose for the adult volunteers was estimated. Table 1 gives the individual inhalation doses. The mean inhalation dose for the adult volunteers was 0.59 mg/kg. 

Table 1 Liquid Turf Study Adult Inhalation Dose of Chlorpyrifos Based on Air Monitoring Data...

Volunteer Inhalation dose (Pg/kg) Dermal dose (Pg/kg) Dermal (hands) dose (Pg/kg) Total dose (Pg/kg)... 

Egan, M.J. and W. Nixon, A Model of Aerosol Deposition in the Lung for Use in Inhalation Dose Assessments, Radiat. Prot. Dosim. 11 5-17 (1985)... 

In a well-controlled and conducted study with human volunteers, Jakubowski et al. (1987) reported that an average of 52% of the inhaled dose of acrylonitrile (5 or 10 mg/m ) is absorbed by the lungs. Similar results were reported by Rogaczewska and Piotrowski (1968), who found that 46% of inhaled acrylonitrile is retained by the lungs of humans. 

Systemic toxicity of inhaled corticosteroids is minimal with low to moderate inhaled doses, but the risk of systemic effects increases with high doses. Local adverse effects include dose-dependent oropharyngeal candidiasis and dys-phonia, which can be reduced by the use of a spacer device. The ability of spacer devices to enhance lung delivery is inconsistent and should not be relied on. 

ICt50 Inhalation dose of a chemical agent (vapor or aerosol) that produces a given, defined level of incapacitation in 50 percent of the exposed subjects. 

Metabolism in the rat is qualitatively similar to that in humans. Four male and four female Wistar rats were exposed individually to 14C-labeled HFC134a at 10,000 ppm for 1 h (Ellis et al. 1993). Atmospheres were monitored with a gas chromatograph. After exposure, urine and feces were collected at 6 h intervals up to 24 h and every 24 h for up to 5 d thereafter. Approximately 1% of the inhaled dose was recovered in urine, feces, and expired air of that 1%, approximately two-thirds was exhaled within 1 h postexposure as unchanged HFC-134a. Exhaled C02 was the primary metabolite and accounted for approximately 0.22% and 0.27% of the inhaled dose in males and females, respectively. Excretion in the urine and feces occurred within 24 h and accounted for 0.09% and 0.04% of the inhaled dose, respectively. The only metabolite identified in urine was trifluoroacetic acid. At sacrifice, 5 d postexposure, radioactivity was uniformly distributed among tissues and accounted for 0.14-0.15% of the inhaled dose. The average total metabolized dose in male and female rats was 0.37% of the inhaled dose. 

HCFC-141b is a poor substrate for cytochrome P-450 2E1, and the level of metabolism is low (Harris and Anders 1991). Pharmacokinetic data indicate that <6% of the inhaled dose was metabolized, and the rest was excreted unchanged (Loizou et al. 1996). 

Pulmonary dynamics, the dimension and geometry of the respiratory tract and the structure of the lungs, together with the solubility and chemical reactivity of the inhalants greatly influence the magnitude of penetration, retention, and absorption of inhaled gases, vapors (Dahl, 1990), and aerosols (Raabe, 1982 Phalen, 1984). The quantity of an inhalant effectively retained in the pulmonary system constitutes the inhaled dose that causes pharmacotoxic responses. 

The inhalation route for administering drugs into the pulmonary system for treatment of respiratory diseases eliminates many bioavailability problems such as plasma binding and first-pass metabolism, which are encountered in parenteral or oral administration. Consequently, a small inhalation dose is adequate for achieving... 

While irritancy resulting from the above reflex reaction is one cause of altered respiratory parameters during exposure, there are many others. These include other types of reflex response, such as bronchoconstriction, the narcotic effects of many solvents, the development of toxic signs as exposure progresses, or simply a voluntary reduction in respiratory rate by the test animal due to the unpleasant nature of the inhaled atmosphere. The extent to which these affect breathing patterns and hence inhaled dose can only be assessed by actual measurement. 

The inhalation dose of krypton Kr 81m is the equivalent of 5 mCi. Express this dose in terms of megabecquerels. 

The following sections provide an overview of the application of the IPL for the study of drug absorption. Examples are provided to illustrate the use of the IPL to study drug permeability, absorption profiles, transport mechanisms and the effects of inhaled dose formulation on drug disposition. 

First, the procedure now used by the EPA for inhalation data differs from what we have described above, in that the ten-fold factor for interspecies extrapolation (animal-to-human) is dropped in favor of a specific model that describes the well-known physiological differences between animals and humans that affect the relative rates of movement of a given administered dose of a chemical in the respiratory tracts of animals and humans. These physiological models provide fairly accurate predictions of the relative doses of chemicals delivered into the respiratory regions of animals and humans who have received identical administered (inhaled) doses. The estimate of delivered dose offers a well-accepted scientific approach to at least part of the problem of interspecies differences. Details of the delivered dose calculations are beyond the scope of this book (see references in Sources and recommended reading). 

In addition, the model also demonstrated that as the concentration of chloroform rises due to increases in chloroform vapor, the absorbed inhalation dose increases faster and becomes larger than the absorbed dermal dose. 

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