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PubMed2004

Respiration-based measurement of lung deposition of a fluorescent dextrane aerosol in a marmoset monkey.

A technique for measurement of respiration-based lung deposition of an aerosol was investigated and subsequently applied in a pilot study with a marmoset monkey. The technique consisted of an aerosol exposure system for a marmoset using a face mask and a previously constructed monkey chair, a method for recovery of fluorescent dextrane from lung material, and respiration measurement of the marmoset by whole-body plethysmography. In the pilot study, a ketamine-anesthetized marmoset was exposed for 20 min to an FITC-dextrane aerosol atmosphere (200 microg/L air, particle size 1.5 microm mass median aerodynamic diameter [MMAD]). It was found that 3.4% of the inhaled aerosol was deposited in the lungs; the aerosol was distributed over the lung lobes with an higher concentration at the distal side.

Administration, Inhalation↗
PubMed1984

Biokinetics of inhaled 239PuO2 in the beagle dog: effect of aerosol particle size.

This study was designed to measure the effect of aerosol particle size on the deposition, retention, excretion and translocation of 239Pu inhaled as the dioxide by Beagle dogs. To address these questions, young adult male and female Beagle dogs received single brief inhalation exposures to one of three monodisperse aerosols of 239PuO2 having sizes of 0.72, 1.4 or 2.8 microns activity median aerodynamic diameter (AMAD). Periodic collections of urine and faeces were made for each dog until sacrifice at times ranging from 4 hours to 2 years after exposure. The results indicate long term retention of a substantial percentage of the initial pulmonary burden (IPB), and that the retention was affected by particle size. The percentage of the initial pulmonary lung burden retained in the long term component and its effective half time (TE) were 90 per cent with TE = 680 days for the 0.72 micron AMAD aerosol, 68 per cent with TE = 1400 days for the 1.4 microns AMAD aerosol and 82 per cent with TE = 1800 days for the 2.8 microns AMAD aerosol. The major route of elimination of 239Pu from lung was via the faeces, but significant amounts were also translocated to thoracic lymph nodes (approximately 15 per cent IPB by 2 years). Small amounts were translocated to liver (0.2 per cent IPB) and skeleton (0.1 per cent IPB) by 2 years after exposure. The average alpha-radiation dose to the lung was projected to be twice as large for the 2.8 microns AMAD group as for the 0.72 micron AMAD group at 10 years after exposure.

Aerosols↗
PubMed2001

Parametric study of selective removal of atmospheric aerosol by coagulation, condensation and gravitational settling.

This work studies the scavenging efficiencies of aerosol particles after a given mechanism of removal (coagulation, heterogeneous nucleation and gravitational settling) as a function of time. It also analyses the health impact of the aerosol before and after the above dynamic mechanisms by comparing the respirable dust fractions. The well-known equations of scavenging are applied to three atmospheric environments (clear, hazy and urban) that represent the aerosol PSDs in the countryside, industry and the city, respectively. From this study it is inferred that respirable dust is hardly scavenged and when compared with the initial volume of respirable aerosol, roughly 10% remains after 18 h of gravitational settling. Therefore, gravitational settling is the main removal mechanism of respirable aerosol compared to condensation and coagulation and is almost six times better than rainout.

Aerosols↗
PubMed2002

Evaluation of the SureSpot direct-reading instrument for the determination of polymeric MDI aerosols.

Recent studies in our laboratories have focused on the reliability of direct-reading instruments for the determination of airborne isocyanate concentrations. The evaluation of airborne isocyanates is complicated because these substances exist as diisocyanate monomers and polyisocyanate oligomers, both in the vapor and aerosol phases. The studies showed that a number of direct-reading instruments, including the SureSpot test kit, do not allow an accurate determination of isocyanates in the aerosol phase. Using a test chamber, concentrations of various commercial polymeric methylenediphenyl diisocyanates (PMDI) were generated in the aerosol phase to examine the correlation between the SureSpot monitor and two laboratory methods. The results obtained with the SureSpot and laboratory methods correlated poorly. More precisely, the results indicated that the SureSpot direct-reading instrument had a distinctive response to each commercial PMDI and, in addition, it was not accurate for the determination of total PMDI in the aerosol phase. It seemed that the analytical response of the SureSpot is based on a calibration curve only reliable for MDI and not for the determination of PMDIs in the aerosol phase. Further investigation also indicated that the calibration provided by the manufacturer could not be converted into a linear curve over the suggested MDI concentrations range. An appropriate calibration procedure was developed in our laboratories for the SureSpot to accurately determine all commercial PMDIs without great variability.

Aerosols↗
PubMed2003

Development of a continuous aerosol mass concentration measurement device.

A dynamic aerosol mass concentration measurement device has been developed for personal sampling. Its principle consists in sampling the aerosol on a filter and monitoring the change of pressure drop over time (Delta P). Ensuring that the linearity of the Delta P = f(mass of particles per unit area of filter) relationship has been well established, the change of concentration can be deduced. The response of the system was validated in the laboratory with a 3.5 microm alumina aerosol (mass median diameter) generated inside a 1-m(3) ventilated enclosure. As the theory predicted that the mass sensitivity of the system would vary inversely with the square of the particle diameter, only sufficiently fine aerosols were able to be measured. The system was tested in the field in a mechanical workshop in the vicinity of an arc-welding station. The aerosol produced by welding is indeed particularly well-adapted due to the sub-micronic size of the particles. The device developed, despite this limitation, has numerous advantages over other techniques: robustness, compactness, reliability of calibration, and ease of use.

Aerosols↗
PubMed2000

Tropospheric sulfate aerosol formation via ion-ion recombination.

We propose a source of aerosols in the lower atmosphere associated with the creation, growth, and recombination of ubiquitous cosmogenically generated ions. This particle source should be favorable in the relatively clean, stable marine boundary layer, providing a uniform, continuous fine particle generator in the presence of dimethylsulfide emissions. Through this mechanism, new sulfate aerosols can be formed at sulfuric acid vapor partial pressures well below the supersaturations required for homogeneous binary nucleation of sulfuric acid/water solutions, which is consistent with numerous observations of new particle formation under sub-saturated conditions. The evolving aerosols in turn control the acid vapor concentration and thus modulate the sizes of the precursor ions and the rate of new particle formation. A simple model representing this nonlinear coupled system predicts that the physical and chemical processes connecting ions, vapors, and aerosols effectively constrain the particle population to a relatively narrow range of values. This self-limiting behavior may explain in part the apparent stability of the marine sulfate aerosol, with mean concentrations of the order of several hundred per cubic centimeter.

Aerosols↗
PubMed2003

Simultaneous sampling of gas- and aerosol-phase TDI with a triple filter system.

A new triple filter system sampler/model is proposed for the precise and accurate simultaneous sampling and determination of gas- and aerosol-phase 2,4-toluene diisocyanate (TDI). The system consists of two front Teflon filters for sampling aerosol-phase TDI and a final coated glass fiber filter to collect gas-phase TDI. The aerosol-phase TDI is collected on the first Teflon filter, while the second Teflon filter is used to estimate gaseous TDI adsorbed by the first. According to the gas adsorption test of two Teflon filters in series, the TDI gas adsorption fraction of the two filters is almost the same. Results of the evaporation test using pure TDI aerosols collected on the Teflon filter show that significant evaporation of the compound does not occur during sampling. These two findings allow the use of a model to estimate accurate gas- and aerosol-phase TDI concentrations. The comparison test with an annular denuder shows that the triple filter system can minimize the TDI sampling bias between the dual filter and the annular denuder systems.

Aerosols↗
PubMed2003

The Southeastern Aerosol Research and Characterization Study: part 1--Overview.

This paper presents an overview of a major, long-term program for tropospheric gas and aerosol research in the southeastern United States. Building on three existing ozone (O3)-focused research sites begun in mid-1992, the Southeastern Aerosol Research and Characterization Study (SEARCH) was initiated in mid-1998 as a 7-year observation and research program with a broader focus including aerosols and an expanded geographical coverage in the Southeast. The monitoring network comprises four urban-rural (or urban-suburban) site pairs at locations along the coast of the Gulf of Mexico and inland, including two moderately sized and two major urban areas (Pensacola, FL; Gulfport, MS; Atlanta, GA; and Birmingham, AL). The sites are equipped with an extensive suite of instruments for measuring particulate matter (PM), gases relevant to secondary O3 and the production of secondary aerosol particles, and surface meteorology. The measurements taken to date have added substantially to the knowledge about the temporal behavior and geographic variability of tropospheric aerosols in the Southeast. Details are presented in four papers to follow.

Aerosols↗
PubMed2004

Characterization of carbon nanoparticles in ambient aerosols by scanning electron microscopy and model calculations.

Size-selected aerosol samples were analyzed by scanning electron microscopy (SEM) to explore (1) the relative concentration of individual and aggregated carbon nanoparticles (C-NPs) and (2) the combustion behavior of C-NP agglomerates. SEM analysis of low-coverage aerosol deposits showed that most of the C-NP matter is present in the form of chain-type agglomerates. The individual C-NPs in the agglomerates are remarkably similar in diameter (40+/-5 nm) and appear to be very tightly bound to the neighboring NPs. Comparison with literature data suggests that the agglomerates originated from diesel exhaust. After gently removing the water-soluble compounds from relatively thick layers of aerosol matter, the residues were exposed to increasing temperatures, for 1 hr at each step, followed by SEM analysis of the same sample area. C-NP agglomerates were found to disappear rapidly at temperatures exceeding approximately 470 degrees C. This observation constitutes the first direct visualization of the combustion of what appears to be the most important fraction of elemental carbon in ambient aerosol matter. The experimental studies were complemented by simple model calculations that aimed at assessing the size-dependent mass fraction of individual C-NPs in ambient aerosol matter. The results suggest that the mass fraction decreases from 20+/-10% at particle diameters of approximately 30-40 nm to less than 0.1% above 300 nm.

Aerosols↗
PubMed1980

Effects of sulfate aerosols in combination with ozone on elimination of tracer particles inhaled by rats.

Several inhaled atmospheres were tested for effects on the rat respiratory defense system. Materials studied included ozone and aerosols of ammonium sulfate, ferric sulfate, and sulfuric acid; relative humidity was also a controlled experimental variable. Each sulfate was studied alone as a submicrometer aerosol at a concentration of 3.5 mg/m3 in air and combined with ozone at 0.8 ppm. Results were compared with those for sham-exposed animals and for rats exposed to ozone alone. Air pollutant exposures, inside stainless steel chambers, were one time only for 4 h. The end points for evaluation of effects were measurements of early and late rates of clearance of radiolabeled insoluble tracer particles. Tracer particles were inhaled before air pollutant exposures and particle clearance was followed for about 2 wk. Ozone alone slowed the early (0-50 h after exposure) particle clearance and stimulated clearance during the later phase (2-17 d). High humidity usually amplified these effects of ozone as well as many of the other atmospheres studied. Sulfate aerosols alone tended to produce relatively small effects on early or late clearance. Combinations of ozone and aerosols resulted in effects that were similar to those of ozone alone. The data do not support the hypotheses that sulfate aerosols synergize with ozone in altering respiratory tract clearance, sulfuric acid being a probable exception. These data alone cannot be used to predict the overall health effects of the materials studied.

Aerosols↗
PubMed1981

Effects of brief and intermediate exposures to sulfate submicron aerosols and sulfate injections and cardiopulmonary function of dogs and tracheal mucous velocity of sheep.

Pulmonary mechanics of anesthetized dogs were not changed or were minimally altered by breathing the following compounds as submicron aerosols in concentrations up to 17.3 mg/m3 for 7.5 min: (1) sodium chloride (as a control), (2) sodium sulfate, (3) ammonium sulfate, (4) zinc sulfate, (5) zinc ammonium sulfate, (6) ammonium bisulfate, (7) aluminum sulfate, (8) manganese sulfate, (9) nickel sulfate, (10) copper sulfate, (11) ferrous sulfate, and (12) ferric sulfate. Submicron aerosols of these compounds in concentrations of 4.1-8.8 mg/m3, administered for 4 h to anesthetized dogs, did not affect mechanics of breathing, hemodynamics, and arterial blood gases. In conscious sheep, tracheal mucous velocity was not altered by exposure to the submicron aerosols of the sulfate compounds. None of these compounds, injected iv in a dose of 1 mg, had adverse effects on mechanics of breathing, pulmonary and systemic hemodynamics, or arterial blood gases. In 100-mg injections, zinc sulfate and zinc ammonium sulfate produced a fall in cardiac output, systemic hypotension, hypoxemia, and metabolic acidosis. Copper sulfate at this dose produced pulmonary hypertension, a fall in cardiac output, hypoxemia, respiratory acidosis, and a decrease of specific total respiratory conductance. It is concluded that submicron aerosols of sulfate salts do not have adverse cardiopulmonary effects when administered in high concentrations for up to 4 h. However, prolonged exposure to high concentrations of zinc sulfate, zinc ammonium sulfate, and copper sulfate aerosols should be carefully monitored because of the possibility that lower levels of these compounds in the bloodstream for long time period might have adverse cardiopulmonary effects.

Aerosols↗
PubMed1986

Inhalation toxicity of lithium combustion aerosols in rats.

Studies of the acute inhalation toxicity of lithium combustion aerosols were undertaken to aid in evaluating the health hazards associated with the proposed use of lithium metal in fusion reactors. A system was developed to generate lithium combustion aerosols by sweeping vapor from molten lithium metal into a controlled air atmosphere. Male and female F344/Lov rats, 9-12 wk of age, were exposed once for 4 h to concentrations of 2600, 2300, 1400, or 620 mg/m3 of aerosol (MMAD = 0.69 micrometer, sigma g = 1.45) that was approximately 80% lithium carbonate and 20% lithium hydroxide to determine the acute toxic effects. Fourteen-day LC50 values (with 95% confidence limits) of 1700 (1300-2000) mg/m3 for the male rats and 2000 (1700-2400) mg/m3 for the female rate were calculated. Clinical signs of anorexia, dehydration, respiratory difficulty, and perioral and perinasal encrustation were observed. Body weights were decreased the first day after exposure in relation to the exposure concentration. In animals observed for an additional 2 wk, body weights, organ weights, and clinical signs began to return to preexposure values. Histopathologic examination of the respiratory tracts from the animals revealed ulcerative or necrotic laryngitis, focal to segmental ulcerative rhinitis often accompanied by areas of squamous metaplasia, and, in some cases, a suppurative bronchopneumonia or aspiration pneumonia, probably secondary to the laryngeal lesions. The results of these studies indicate the moderate acute toxicity of lithium carbonate aerosols and will aid in the risk analysis of accidental releases of lithium combustion aerosols.

Aerosols↗
PubMedDate not supplied

Mechanistic understanding of aerosol emissions from a brazing operation.

Welding operations produce gaseous and aerosol by-products that can have adverse health effects. A laboratory furnace study was conducted to aid understanding of the chemical and aerosol behavior of a widely used, self-fluxing brazing alloy (89% Cu, 6% Ag, 5% P) that is also used with a supplemental fluxing compound to prevent oxidation at the molten metal surface. The results indicate that the aerosols generated by the alloy are transient (produced over a short duration of time) and are associated with mass transfer of phosphorus species from the molten metal surface to the surrounding gas. In contrast, when the alloy was used in conjunction with the supplemental fluxing compound, a relatively nontransient, submicron-size aerosol was generated that was several orders of magnitude higher in concentration. Thermodynamic equilibrium analysis suggests that fluoride (a major constituent in the fluxing compound) played a significant role in reacting with the brazing alloy metals to form gas phase metal fluoride compounds that had high vapor pressures when compared with their elemental or oxide forms. As these metal-fluoride vapors cooled, submicron-size particles were formed mainly through nucleation and condensation growth processes. In addition, the equilibrium results revealed the potential formation of severe pulmonary irritants (HF and BF3) from heating the supplemental fluxing compound. These results demonstrated the importance of fluxing compounds in the formation of brazing fumes, and suggest that fluxing compounds could be selected that serve their metallurgical intention and suppress the formation of aerosols.

Aerosols↗
PubMedDate not supplied

Characterization of metalworking fluid aerosols in bearing grinding operations.

The concentrations and size distribution of metalworking fluid aerosols were investigated in grinding operations in the bearing manufacturing industry. Fifteen paired open- and closed-face cassette samples and five cascade impactor samples were obtained in each of three types of grinding machinery (face, microcentric, and progressive). Aerosol mass concentration as measured by open-face filter sampling ranged from 0.34 to 2.43 mg/m3. As measured by closed-face sampling the range was 0.14 to 2.01 mg/m3. For each grinding process, open-face concentration was significantly higher than the closed-face concentration (paired t-test, p <0.05). Mass median aerodynamic diameter (MMAD) ranged from 3.33 to 6.26 microm. The percentage of mass greater than 9 microm ranged from 8.0 to 45.3. The MMAD and fraction greater than 9 microm were significantly greater for the aerosol produced by the face grinder compared with the other two processes. The results indicate that (1) closed-face sampling results in a lower aerosol mass concentration, as compared with open-face sampling, with the degree of difference being somewhat dependent on grinding process; and (2) the particle size distribution and concentration of metalworking fluid aerosols may vary with the type of grinding operation sampled.

Aerosols↗
PubMed1980

Aerosol generation to simulate specific industrial fine particle effluents.

Techniques were developed for generating large quantities of fine particle metal oxide aerosols. The aerosols were generated by burning flammable solutions containing appropriate soluble compounds (nitrates, for example) of the desired elements. In the flame these compounds generally decomposed to oxides. The generated aerosol flow rates were as high as 42 m3 per minute (1500 cfm); the mass concentrations were as high as 16.8 g per m3 at STP. For most aerosols the particle concentrations were of the order of 10(9) particles per cm3. Electron microscopic pictures (SEM and TEM) of precipitated particles show that many of the larger particles (20 microm) are hollow and that the smaller particles (0.01 microm) are aggregated. Specific aerosols were generated to simulate the fine particulate effluents generated by combustion of pulverized coal (electricity generation) electric arc and basic oxygen furnaces (iron and steel production) and zinc smelters. Methods were developed to vary the sulfur dioxide concentration and the electrical resistivities of the simulants for coal combustion.

Aerosols↗
PubMed1980

Paint spray tests for respirators: aerosol characteristics.

Liquid paint is sprayed from an atomizing nozzle to form an aerosol for testing paint spray respirators. The generated aerosol conditions are dependent upon liguid properties, spray-nozzle flow conditions and droplet evaporation. A technique was developed for controlling the aerosol concentrations reliably. Particle-size distributions of lacquer and enamel have been measured. The lacquer distribution was found to be multi-modal. Aerosol concentration dradients arise when the nozzle is not properly positioned. Filter loading resistance is significantly affected by these concentration variations. With regard to selection of standard aerosol test be improved by modifying the current NIOSH criteria to include a description of the particle-size distribution, a more precise definition of the paint and paint thinner chemical compositions, and a narrower concentration range.

Aerosols↗
PubMed1980

Generatation and characterization of sodium sulfite aerosols for applications in inhalation toxicologic research.

A method has been developed for generation of submicrometer aerosols of sodium sulfite suitable for use in inhalation toxicologic research. Concentrations ranging up to about 30 mg/m3 Na2SO3 were achieved in a 0.44 m3 exposure chamber with an air flow rate of 0.20 m3/min for periods up to 16 days. The coefficient of variation of the sulfite aerosol mass concentration was about 4% during a typical exposure period. The measured mass median aerodynamic diameters (MMADar) of the generated aerosols were 1.2 (+/- 0.2SD) microns with a geometric standard deviation (sigma g) of 1.9 (+/- 0.3SD). The chamber was sampled for gas phase SO2 concentration, and aerosol samples were analyzed for particulate sulfite and sulfate. The fraction of sulfur qas sulfite in the aerosol was usually 95% and was always greater than 90%. Gas phase SO2 amounted to less than 2% of the total S(IV) present in the chamber.

Aerosols↗
PubMed1983

Respiratory tract deposition of polydisperse aerosols in humans.

Total and regional deposition of polydisperse aerosols in the human respiratory tract are studied theoretically. The size distribution of the aerosol is assumed to be lognormal. For a given mass median particle diameter, mass deposition fraction is found to vary with the geometric standard deviation of the aerosol. The departure of the deposition pattern in various regions of the respiratory system from that of a monodisperse aerosol is interpreted in terms of the average mobility effect and deposition limitation effect of the polydisperse aerosol together with the sequential filtering effect of the respiratory tract.

Aerosols↗