Fused Aluminosilicate Particles Research Articles

Particle transport from the lower respiratory tract

ABSTRACT Particle transport of monodisperse fused aluminosilicate particles and cobalt oxide particles was studied in beagle dogs for 1000 d after inhalation. Particle transport to the larynx and s...

Determination of specific surface area by krypton adsorption, comparison of three different methods of determining surface area, and evaluation of different specific surface area standards

A method for the measurement of the specific surface area of powder samples weighing between 1 and 50 mg is described. The method is based on 85Kr adsorption. A ratio test demonstrated that the method gives self-consistent data for samples of less than 10 mg. A cross-check, using 50-mg samples of uranium dioxide, demonstrated agreement to ±5% with results obtained using nitrogen as adsorbate and a vacuum microbalance. The suitability of materials as specific surface area standards is discussed. All the oxides studied gave c values between 50 and 300 for adsorption of nitrogen, and Type 2 isotherms, indicating applicability of the Brunauer, Emmett, and Teller (BET) method of calculating nitrogen-specific surface area. Samples of titanium dioxide and aluminum oxide were found to be uniform with respect to specific surface area. However, the values obtained for titanium dioxide standards were influenced by the temperature to which samples were heated prior to the determination of adsorption properties. Specific surface areas of three standard powder samples of different specific surface areas were measured by a vacuum microbalance, a flowing gas thermal conductimetric method, and a 85Kr adsorption technique. Values obtained were found to be independent of both the method employed and the operator. Data for successive determinations on samples of fused aluminosilicate particles demonstrated a precision of ±2% for 5-mg samples, but an accuracy of only ±20%. Cell design and blank corrections are discussed.

Deposition and clearance of particles inhaled by beagle dogs previously exposed to SO2.

The effect of preexisting pulmonary disease on the deposition and retention of inhaled relatively insoluble radiolabeled particles was studied. Two dogs were exposed to 500 ppm sulfur dioxide 2 h/day, 5 days/week for 16 weeks and two dogs were sham-exposed to filtered air for the same period. Dogs exposed to sulfur dioxide developed chronic bronchitis during this exposure period. After the bronchitis had been established for 10 weeks, all 4 dogs were exposed by inhalation to 1.7 micron aerodynamic diameter 134Cs-labeled fused aluminosilicate particles (FAP) and the exposures to SO2 were discontinued. The bronchitis resolved within 4 weeks after SO2 was discontinued. Dogs were periodically whole-body counted and excreta were periodically collected and counted over a 385-day period following the 134Cs exposure. Deposition of the [134Cs]FAP in the pulmonary region averaged 42% for control dogs and 16% for dogs exposed to SO2; deposition in extrapulmonary regions of the respiratory tract averaged 58% for control dogs and 84% for dogs exposed to SO2. Although deposition patterns were different, early and long-term clearance pathways and rates were the same for all dogs, as indicated by analysis of whole body, excreta, and tissues for their burdens of 134Cs.

Performance of a TSI Aerodynamic Particle Sizer

Calibration curves of the aerodynamic particle sizer (APS) under different sets of operating conditions (i.e., pressure drop across the nozzle, flow rate, and ambient pressure) were obtained. Materials used included oleic acid (OA), dioctyl phthalate (DOP), polystyrene latex (PSL), and fused aluminosilicate particles (FAP). The effect of particle density on the calibration was not found to be significant among test aerosols (in the density range from 0.89 to 2.3 g/cm3). Calibration curves obtained at reduced ambient pressure were different from the manufacturer's curve, indicating that recalibration of the APS is required if other than standard operating conditions are used. However, all the curves can be consolidated into a unique curve that relates the Stokes number at the nozzle exit to the normalized particle velocity (particle velocity divided by gas velocity). Methods for calculating gas velocity, particle velocity, and other pertinent parameters for the APS were developed and the results are presen...

Respiratory tract retention of relatively insoluble particles in rodents

Rats and hamsters inhaled monodisperse fused aluminosilicate particles (FAP) labelled with strontium-85 (CMD 1.25 and 1.21 μm, respectively). Respiratory tract retention was followed by external γ-ray counting and analysis of sacrificed animals for up to 15 months after exposure. Only 2% of the nasal deposit remained at an hour after administration, and less than 0.1% was retained for more than 2 days. Less than 1% of the deposit on the trachea and main bronchi was retained for more than a week. About 10% of the initial pulmonary deposit was retained at a year, far less than for FAP in man. In rats the average pulmonary clearance rate fell from 2.2 × 10 −2 per day, at 10 days after exposure to 4 × 10 −3 per day at a year following exposure, and in hamsters from 1.1 × 10 −2 per day to 5 × 10 −3 per day. The contributions of dissolution and particle transport to lymph nodes were estimated to be about 5 × 10 −4 per day and 10 −5 per day, respectively, and therefore pulmonary clearance was dominated by the transport of particles to the gastro-intestinal tract. Clearance of plutonium dioxide particles in the same rodent strains (initial pulmonary deposits approximately 1 kBq) was initially very similar, but after a few months became slower, presumably because of lung damage from the plutonium.

Long-term retention of particles in the human respiratory tract

Twelve healthy non-smoking male volunteers inhaled monodisperse 1 and 4 μm diameter fused aluminosilicate particles labelled with strontium-85 and yttrium-88, respectively. Retention was followed for at least a year (372–533 days). Approximately 7% of the initial lung deposit of 1 μm particles and 40% of that of the 4 μm particles were associated with a distinct rapid clearance phase. These figures correspond closely to the calculated tracheo-bronchial deposits, indicating insignificant rapid pulmonary clearance. Retention of the remaining material ( R( t)) generally followed a two-component exponential function, the phases having half-times of the order of tens of days and several hundred days, respectively. At 350 days after inhalation, R( t) averaged 46 ± 11% ( x ± SD) for the 1 μm particles and 55 ± 11% for the 4 μm particles. Retention of the 1 μm particles by each subject was correlated with that of 4 μm particles. Estimated lung dissolution rates based on urinary excretion were 7 × 10 −4 and 2 × 10 −4 per day for the 1 and 4 μm particles, respectively. The estimated rate of clearance of particles from the pulmonary region to the gastro-intestinal tract fell from an initial value of 4 × 10 −3 per day to about 1 × 10 −3 per day at and beyond 200 days after inhalation.

Pulmonary clearance of monodisperse fused aluminosilicate particles in rodents

Pulmonary clearance of monodisperse fused aluminosilicate particles in rodents

Retention of monodisperse or polydisperse aluminosilicate particles inhaled by dogs, rats, and mice

This study compared long-term retention of 134Cs-labeled fused aluminosilicate particles inhaled by three animal species. Dogs, rats, and mice were briefly exposed to 0.7-, 1.5-, or 2.8-μm activity median aerodynamic diameter (AMAD) monodisperse particles or a polydisperse aerosol with 1.5 to 2.0 μm AMAD and geometric standard deviation of 1.5 to 2.0. Tissues and excreta were collected for up to 850 days after exposure to determine retention and clearance patterns of the inhaled particles. Simulation models were developed for each animal species and aerosol. Solubilization was the dominant factor in long-term lung clearance for most of the particles inhaled by dogs; mechanical clearance was dominant in rats and mice. After accounting for solubility, physical clearance from the lung to the gastrointestinal tract and to lung-associated lymph nodes (LALNs) was independent of particle size within the size range investigated. Rats and mice demonstrated a rapid clearance from the pulmonary region, with most of the mechanically cleared particles going to the gastrointestinal tract; significant translocation to the LALNs occurred for only a few days. The dogs cleared deposited particles at a slower rate, with most of the long-term clearance going to LALNs. A small portion of the initial deposit was retained in the upper respiratory tract of all three species. Results from the data for dogs were used to make long-term predictions for chronic inhalation of particles by humans.

THE LONG-TERM CLEARANCE KINETICS OF INSOLUBLE PARTICLES FROM THE HUMAN LUNG

Abstract Seven volunteers inhaled monodisperse 1.2 and 3.9 μm dia. (1.9 and 6.1 μm equivalent aerodynamic diameter) fused aluminosilicate particles labelled with 85Sr and 88Y respectively. Lung retention has been followed for over 200 days. Approximately 8% of 1.2 μm and 40% of 3.9 μm particles cleared within 6 days. It was calculated that these fractions were deposited within the conducting airways and therefore no rapid alveolar clearance was observed. Overall retention of the remaining material showed half-times averaging 320 days, with considerable intersubject variation but little effect of particle size. Two-component exponential functions represented retention more satisfactorily. Approximately 4% of 1.2 μm and 11% of 3.9 μm particles retained at 6 days cleared with a half-time of about 20 days, the rest with half-times of 330 and 420 days respectively. Estimated lung dissolution rates were 1 × 10-3 and 5 × 10-4 d-1 for 1.2 and 3.9 μ m particles, indicating that for both sizes mechanical clearance shows a slow phase with a half-time of about 600 days.

Toxicity of 90 Y in Relatively Insoluble Fused Aluminosilicate Particles When Inhaled by Mice

LUNDGREN, D. L., HAHN, F. F., AND MCCLELLAN, R. O. Toxicity of 90Y in Relatively Insoluble Fused Aluminosilicate Particles When Inhaled by Mice. Radiat. Res. 88, 510-523 (1981). A life span study in mice of the toxicity of a short-half-lived (64.2 hr) #-emitting radionuclide, 90Y, inhaled in insoluble fused aluminosilicate particles was conducted. Mice were exposed to achieve initial lung burdens between 1 and 140 MCi of 90Y with each microcurie of 90Y deposited in lung delivering an absorbed lung dose of 150 rad. The cumulative survival rates of mice in groups with initial lung burdens of 1 to 10 eCi (1100 ? 380 rad to lungs) and 11 to 20 ACi (2300 ? 400 rad to lungs) were not significantly different from that of control mice. Initial lung burdens of more than 20 MCi (>3000 rad to lungs) resulted in radiation pneumonitis and a significant shortening of the life span. The incidences of all lung tumors and other lesions in mice exposed to 90Y in fused aluminosilicate particles were similar to those of the control mice, except pulmonary adenomas, found more frequently in groups of mice with initial lung burdens of 1 to 10 and 11 to 20 jACi. The early occurring biological effects observed in mice in this study were similar to those observed in beagle dogs exposed to 90Y in the same form.

Physical properties of electrical mobility classified aerosols

Systematic investigation of physical properties of electrical mobility classified aerosols is reported. Physical properties such as size distributions, mobility distributions, and the ratio of singly to doubly charged fractions were determined theoretically and experimentally. Fused aluminosilicate particles with well-defined physical characteristics were generated in an electrostatic classifier. The classified monodisperse aerosols were collected on copper electron microscope grids by an electrostatic precipitator and examined in a transmission electron microscope. The size distribution and singly to doubly charged ratio were determined directly from the electron micrographs, and the mobility distribution was deduced. The theoretical and experimental results agreed to within ± 10%. If the doubly charged fraction is substantial, corrections should be made. Both the effective mean diameter and the geometric standard deviation are functions of the ratio of singly to doubly charged fractions and can be accurately calculated. Based on these results the physical properties can be theoretically predicted. This is useful in many applications of classified aerosols.

Fraction of Energy Absorbed from β-Emitting Particles in the Rat Lung

Forty-four male Fischer-344 rats were exposed, nose only, to a relatively insoluble aerosol of /sup 144/Ce-labeled fused aluminosilicate particles. Fractional ..beta.. energy absorption was measured 7 to 9 days after exposure for 28 rats (ages 12 to 25 weeks and body weights of 183 to 337 g); lung burdens were 13 to 82 nCi. An additional group of 16 rats was exposed when 12 weeks old and maintained for 6 months prior to analysis; body weights and lung burdens 6 months after exposure ranged from 276 to 368 g and 16 to 46 nCi, respectively. Lungs were carefully removed, inflated, and frozen by immersion in liquid nitrogen. The energy spectrum from each lung was measured in a 4..pi.. ..beta.. spectrometer, keeping the lung frozen throughout this procedure. Over the range of lung sizes in this study (0.88 to 1.66 g) the mean fractional energy absorption and standard deviation were 0.23 +- 0.078, respectively. Results agreed well with theory, indicating that calculated values for fractional energy absorption in the lung can be used for a range of lung sizes and ..beta.. energies. Calculated values for fractional energy absorption as a function of ..beta.. energy are included for several lung sizes betweenmore » 0.5 and 10 g.« less

Effects of Chronic Pulmonary Irradiation on Peripheral Lymphocytes and Their Function in the Dog

Beagle dogs were exposed by inhalation to /sup 144/Ce in fused aluminosilicate particles, a relatively insoluble, inert carrier material. The radioactive particles deposited in the deep lung resulted in chronic irradiation of the pulmonary and adjacent thoracic tissues. Dogs exposed to high levels of /sup 144/Ce in fused aluminosilicate particles received more than 25,000 rad to lung by 3 yr after exposure. They developed a severe and persistent lymphopenia, and their remaining peripheral lymphocytes showed a decreased ability to respond to plant mitogens in vitro. The lymphopenia and the functional defect in the remaining lymphocytes suggested that an immunologic suppression existed in these dogs. Many lymphocytes were being killed in vivo by the radiation but another population was present that was viable in vivo but died when placed in vitro, accounting for at least part of the reduction in response to plant mitogens. No plasma factor was found that could account for the reduced lymphocyte transformation. The /sup 144/Ce-exposed dogs developed a high incidence of primary pulmonary hemangiosarcomas between 1 and 5 yr after exposure. This suggests that carcinogenesis after intrapulmonary deposition of radionuclides may result from a combination of the direct carcinogenic effect and the immunosuppressive effect of themore » irradiation.« less

Radiation-Induced Pulmonary Fibrosis: Study of Changes in Collagen Constituents in Different Lung Regions of Beagle Dogs after Inhalation of Beta-Emitting Radionuclides

Pulmonary collagen turnover (synthesis, degradation, and accumulation) was studied in 40 dogs injured by inhalation exposure to ${}^{90}{\rm Y}$ ( $T_{{\textstyle\frac{1}{2}}}{\rm eff}$ 2.6 days, Ē = 0.9 MeV), ${}^{91}{\rm Y}$ (50 days, 0.59 MeV), ${}^{144}{\rm Ce}$ (170 days, 1.29 MeV), or90 Sr (370 days, 1.13 MeV) in fused aluminosilicate particles. Cerium-144 and90 Sr in fused particles produced more uniform patterns of pulmonary damage than did ${}^{90}{\rm Y}$ or ${}^{91}{\rm Y}$ in fused particles. Fibrosis was more severe in the intermediate than in the peripheral or hilar regions of the lungs of dogs exposed to ${}^{90}{\rm Y}$ in fused particles. That observation was consistent with the relatively greater radiation dose delivered to the peribronchiolar region during the early clearance of ${}^{90}{\rm Y}$. Collagen synthesis and degradation responses in the peripheral and hilar regions of animals exposed to ${}^{91}{\rm Y}$ and in the intermediate area of90 Sr indicated the presence of previously...

Estimation of particle size distribution parameters in animal lungs

A constant of specific solubility of 2·5 × 10 −8 g cm −2day −1 was determined for fused aluminosilicate particles, by observing in vivo retention kinetics after intravenous injection into rats. Studies over the past years in this laboratory, in which dogs and rats have inhaled labeled aerosols of these particles, have shown retention half-lives in the lung of 460 and 285 days, respectively. By applying these values for solubility and half-life to Mercer's theory of dissolution from the deep lung, the initial distribution of particles deposited in the pulmonary regions of dogs and rats following inhalation was calculated. From an inhaled aerosol with a mass median diameter, D m, of 1·0 μm and σ o = 1·7, a distribution described by D m = 0·51 μm and σ o's ranging from 1·16–1·48 was estimated to have been deposited in the Beagle dog lung. and a D m =< 0·32 μm and σ o's ranging from 1·18–1·29 was similarly calculated for rats.