Retention in the lungs

PNEUMOCONIOSIS A group of lung diseases of a chronic fibrotic character due to the inhalation and retention in the lungs of a variety of industrial dusts. The main diseases are asbestosis, silicosis, coalworkers pneumoconiosis and mixed-dust pneumoconiosis less common pneumoconioses are associated with talc, clay or aluminium. 

Human and animal studies have shown that long-term retention in the lungs of large quantities of inhaled insoluble uranium particles (e.g., carnotite dust [4% uranium as uranium dioxide and triuranium octaoxide, 80-90% quartz, and <10% feldspar]) can lead to serious respiratory effects. However, animals exposed to... 

Radioactive Strontium. The Department of Energy (DOE) has established derived air concentrations (DAC) for workplace exposure to radiation at DOE facilities. The DAC ranges from 0.000000002 pCi/mL (2xl0"9 pCi/mL of air) for 100-day retention in the lung to 0.000000008 p Ci/mL (8xl0 9 p Ci/mL of air) for retention less than 10 days. The Nuclear Regulatory Commission established an annual intake limit of 20 pCi for on-the-job exposure to 90Sr in air. 

The rates or percentages of absorption of inhaled zinc in animals are not available however, studies provide data on zinc retention in the lungs. Zinc retention values were 19.8%, 11.5%, and 4.7% in the lungs of guinea pigs, rats, and rabbits, respectively, after inhalation exposure (nose-only) to 3.5-9.1 mg zinc/m as zinc oxide aerosol for 2-3 hours (Gordon et al. 1992). The aerosol had a mass... 

CN has been shown to increase lung sphingomyelin and decrease phosphatidylcholine and ethanolamine in rats (Kumar et al., 1995). Based on the increased bacterial retention in the lung in mice exposed to CN, the authors concluded that CN might increase susceptibility to infection. This may be attributed to the immunotoxic effects of CN through altered, T-cell-mediated macrophage functions (Kumar et al., 1992). 

Pneumoconiosis is the term applied to interstitial lung disease resulting from chronic exposure to airborne mineral dust, its inhalation and deposition and the tissue reaction of the host to its presence. Pneumoconiosis due to coal dust - and coal mine dust - is known as coal worker s pneumoconiosis (CWP). Nevertheless, the inhalation and retention in the lung of dust composed predominantly of carbon - often termed anthracosis - is seen in many individuals, particularly those who smoke or live in a city or industrial environment. Microscopically, this material is recognized as dense black particles, mostly 1-2 pm in size, within macrophages adjacent to terminal or proximal... 

This is illustrated in Figure 12 with the results of simulation modeling of the deposition and retention in the lungs of inhaled relatively insoluble particles. Both the shape of the build-up curves and the differences among species should be noted. The lung burdens always slowly increase over a period of months to ultimately reach lung burdens that are at equilibrium with the concentration of particles in the air. This equilibrium relation varies among the several species commonly used for inhalation toxicity studies and hiunans. 

Mitchel RE. Aerosol retention in the lungs as a function of respiration rate and particle size. Ph.D. dissertation. Ohio State University, 1971. 

Figure 1 Particle retention in the lungs after a bolus inhalation of iron oxide particles of 3.5-pm-aerodynamic diameter Inhalation started from functional residual capacity, tidal volume 600 cm, volumetric lung depth of the aerosol bolus, VL = 50 mL.

On the other hand, measurement of the kinetics of particle retention in the lungs is necessarily required as a quantitative approach to estimate the Ifactional contribution of each clearance pathway investigated. Experimentally, there are two approaches to measure the kinetics of particle retention after identical exposures to the test particles ... 

Figure 7 Series of gamma-camera scintigrams of particle retention in the lungs obtained from an individual dog taken at different days after inhalation of 00304 particles by (upper) a dorsal and a (lower) right lateral view. At sacrifice, particle accumulation observed in the scintigrams was confirmed to be taken up in tracheobronchial lymph nodes.

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