Radioactivity respiratory

DISTRIBUTION The distribution of 14C-pyridostigmine was studied by Birtley et al. Ten per cent of the i.m. dose was present in the alimentary tract within 1 h after injection and 0.3% of the dose is secreted in the bile. A high concentration of radioactivity occurred in the kidney when excretion in the urine was at its maximum level. Lower concentrations were present in the liver, intestinal contents, heart, blood, and muscle. Radioactivity was also detected in the lungs, spleen, and skin, but not in the brain, thymus gland, intestinal wall, or body fat. The detection of radioactive respiratory C02 suggested that to a small extent pyridostigmine may be metabolized by another route. The serum concentration was dose-dependent and was correlated with the clinical response. A radio-immunoassay (RIA) method was developed to determine the plasma concentration time profiles and tissue distribution of PB in rat following its i.m. administration. This study found that PB had a half-hfe (tl/2) of 25... 

Respiratory protective equipment for use against airborne radioactivity... 

EH53 Respiratory protective equipment against airborne radioactivity. 

The ICRP (1994b, 1995) developed a Human Respiratory Tract Model for Radiological Protection, which contains respiratory tract deposition and clearance compartmental models for inhalation exposure that may be applied to particulate aerosols of americium compounds. The ICRP (1986, 1989) has a biokinetic model for human oral exposure that applies to americium. The National Council on Radiation Protection and Measurement (NCRP) has also developed a respiratory tract model for inhaled radionuclides (NCRP 1997). At this time, the NCRP recommends the use of the ICRP model for calculating exposures for radiation workers and the general public. Readers interested in this topic are referred to NCRP Report No. 125 Deposition, Retention and Dosimetry of Inhaled Radioactive Substances (NCRP 1997). In the appendix to the report, NCRP provides the animal testing clearance data and equations fitting the data that supported the development of the human mode for americium. 

Respiratory Tract Clearance. This portion of the model identifies the principal clearance pathways within the respiratory tract. The model was developed to predict the retention of various radioactive materials. Figure 3-4 presents the compartmental model and is linked to the deposition model (see Figure 3-2) and to reference values presented in Table 3-5. This table provides clearance rates, expressed as a fraction per day and also as half-time (Part A), and deposition fractions (Part B) for each compartment for insoluble... 

LaFuma J, Nenot JC, Morin M, et al. 1974. Respiratory carcinogenesis in rats after inhalation of radioactive aerosols of actinides and lanthanides in various physicochemical forms. In Karbe E, Park JF, eds. Experimental lung cancer Carcinogenesis and bioassays, international symposium. New York Springer, 443-453. 

Each liter of air normally contains a few atoms each of 218Po, 211+Pb, 211+Bi and 211+Po, which are the short-lived decay products of the radioactive noble gas radon. When inhaled, these atoms can be deposited on the lining of the respiratory tract, causing irradiation of the tissue due to further radioactive decay. This irradiation accounts for about one half of the average persons dose... 

Cuddihy, R. G. and Boecker, B. B. (1973). Controlled administration of respiratory tract burdens of inhaled radioactive aerosols in beagle dogs, Toxicol Appl. Pharmacol. 25, 597. 

Radioactivity from " C-labeled chloroform was detected in the placenta and fetuses of mice shortly after inhalation exposure (Danielsson et al. 1986). In early gestation, accumulation of radioactivity was observed in the embryonic neural tissues, while the respiratory epithelium was more involved in chloroform metabolism in the late fetal period. 

Using radioactive labeled UICC samples, the deposition and distribution of asbestiform fibers in the pulmonary cavity have been studied. For example, after thirty minutes of inhalation, the deposition of fibers in the respiratory track was shown to be proportional to the median aerodynamic particle diameter for the two UICC chrysotiles, amosite, anthophyllite, and crocidolite. The percentage of total deposited fiber in the lower respiratory tract varied inversely as the square root of the particle diameter (Morgan et al., 1975). 

Evans, J. C., R. J. Evans, A. Holmes, R. F. Hounam, D. M. Jones, A. Morgan, and M. Walsh (1973). Studies on the deposition of inhaled fibrous materials in the respiratory tract of the rat and its subsequent clearance using radioactive tracer techniques. 1 UICC Crocidolite Asbestos. Environ. Res. 6 180-201. 

Respiratory Effects. Although the SMR for respiratory diseases was 1.31 among workers at a thorium refinery (Polednak et al. 1983), the increase may have been attributable in part to smoking Exposure level estimates for inhalation intakes ranged from 0.003-0.192 nCi/m (0.001-0.007 Bq/m ) for a period of 1 -33 years. Because the workers were exposed to other toxic compounds (uranium dust) as well as other radioactive metals, toxic effects cannot necessarily be attributed to thorium. Therefore, no quantitative information from the study is reported in Table 2-1 or Figure 2-1. 

In whole-body autoradiographic studies, covalently bound radioactivity from ethylene dibromide was detected in the surface epithelia of the entire respiratory and the upper alimentary tracts of mice and rats (Brandt, 1986), in the epithelia of the oral cavity, oesophagus and forestomach of fetal mouse (Kowalski et al., 1986), and in vaginal epithelium of mice and rats (Brittebo et al., 1987). 

Immediately dangerous to life or health (IDLH) conditions pose a threat of severe exposure to contaminants, such as radioactive materials, that are likely to have adverse cumulative or delayed effects on health. Two factors are considered when establishing IDLH concentrations. The worker must be able to escape (1) without loss of life or without suffering permanent health damage within 30 minutes and (2) without severe eye or respiratory irritation or other reactions that could inhibit escape. If the concentration is above the IDLH, only highly reliable breathing apparatus is allowed. 

The lines in Fig. 7.4 are the results of theoretical calculations, using models of the respiratory tract (Yu Diu, 1982). The points are measurements with radioactive aerosols. Numerous other determinations of fractional deposition in the whole tract have been made, using non-radioactive methods to count the number of particles in the inhaled and exhaled air (Heyder et al., 1986 Schiller et al., 1988). Fractional deposition is least for particles of about 0.2 to 0.5 m diameter. Table 7.1 shows that the combined effect of sedimentation and Brownian motion is then at a minimum. 

The respiratory activity of the brain tissue was determined by measuring the rate of oxygen uptake with a Clark oxygen electrode (7). The sample of tissue (a brain half) was treated exactly as if used in a calcium efflux experiment except no radioactivity or RF power was used. Following this procedure which required about 55 minutes, the tissue was placed in the oxygen electrode cell containing 1.6 ml of the standard medium (pH 7.8) at 37°C and the rate of oxygen uptake was recorded. 

High-radiation areas must be secured carefully (i.e., level greater than 500 rad, radiation absorbed dose in 1 h at a distance of 1 m from the source) by providing proper ventilation and respiratory equipment, which monitors air contamination. It is also recommended that the radioactive material be properly stored with the required control along with posting signs such as ... 

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