Chong S. Kim

Deposition Characteristics of Aerosol Particles in Sequentially Bifurcating Airway Models

Local deposition efficiencies and deposition patterns of aerosol particles were studied experimentally in sequential double bifurcation tube models with two different branching geometries: one with in-plane (model A) and another with 90 out-of-plane bifurcation (model B). The dimensions of the model were similar to those of 3rd-5th generation human bronchial airways. Monodispersed oil particles (2.9-6.7 mu m diameter range) tagged with uranine were generated as test aerosols and were drawn through the model at flow rates in the Reynolds number (Re) of 283-4718. Both symmetric (1:1) and asymmetric (1:2, 1:3, and 1:0) flow patterns were used at the first bifurcation. Results showed that deposition efficiencies (DE) in each bifurcation increased with increasing Stokes number (Stk), ranging from ∼1% at Stk=0.02 to ∼40% at Stk=0.2, and could be fitted well with modified logistic functions. With symmetric flow conditions, DE was some what smaller in the second than the first bifurcation in both models. DE was g...

Lung function and inflammatory responses in healthy young adults exposed to 0.06 ppm ozone for 6.6 hours.

RATIONALEnExposure to ozone causes a decrease in spirometric lung function and an increase in airway inflammation in healthy young adults at concentrations as low as 0.08 ppm, close to the National Ambient Air Quality Standard for ground level ozone.nnnOBJECTIVESnTo test whether airway effects occur below the current ozone standard and if they are more pronounced in potentially susceptible individuals, such as those deficient in the antioxidant gene glutathione S-transferase mu 1 (GSTM1).nnnMETHODSnPulmonary function and subjective symptoms were measured in 59 healthy young adults (19-35 yr) immediately before and after exposure to 0.0 (clean air, CA) and 0.06 ppm ozone for 6.6 hours in a chamber while undergoing intermittent moderate exercise. The polymorphonuclear neutrophil (PMN) influx was measured in 24 subjects 16 to 18 hours postexposure.nnnMEASUREMENTS AND MAIN RESULTSnSubjects experienced a significantly greater (P = 0.008) change in FEV(1) (± SE) immediately after exposure to 0.06 ppm ozone compared with CA (-1.71 ± 0.50% vs. -0.002 ± 0.46%). The decrement in FVC was also greater (P = 0.02) after ozone versus CA (-2.32 ± 0.41% vs. -1.13 ± 0.34%). Similarly, changes in %PMN were greater after ozone (54.0 ± 4.6%) than CA (38.3 ± 3.7%) exposure (P < 0.001). Symptom scores were not different between ozone versus CA. There were no significant differences in changes in FEV(1), FVC, and %PMN between subjects with GSTM1-positive and GSTM1-null genotypes.nnnCONCLUSIONSnExposure of healthy young adults to 0.06 ppm ozone for 6.6 hours causes a significant decrement of FEV(1) and an increase in neutrophilic inflammation in the airways. GSTM1 genotype alone appears to have no significant role in modifying the effects.

Fine particle concentrators for inhalation exposures—effect of particle size and composition

This paper presents the development and evaluation of ambient fine particle concentrators for conducting animal and human exposure studies. These systems utilize the technology of virtual impactors to concentrate particles in the range 0.15--2.5 μm. Ambient particles are first drawn at 5000 1m -1 through a preselective inlet that removes particles above 2.5 μm. Subsequently, the remaining aerosol is drawn through a series of virtual impactors, which increase particle concentration by a factor of about 10 and 30, for human and animal exposures, respectively. Results from the experimental characterization of the concentrators showed that the concentration enrichment process occurs without any distortion in the size distribution and chemical composition of the sampled ambient aerosols. Furthermore, labile constituents of fine particles, such as volatile ammonium nitrate are preserved during this process.

Particle deposition in bifurcating airway models with varying airway geometry

Abstract Local deposition efficiencies and deposition patterns of aerosol particles were studied experimentally in single bifurcation tube models with varying geometry. The diameter ratio (DR) of the daughter to parent tube was varied from 0.64 to 1.0 and a local obstruction was also imposed in some of the models. Monodispersed oil particles (size range =3–7 μm dia.) tagged with uranine were generated as test aerosols and were drawn through the model at flow rates corresponding to Reynolds number (Re) of 283–3397. It was found that deposition of particles took place mainly on and in the immediate vicinity of the bifurcation ridge for Stokes number (Stk) ≥0.03 regardless of tube geometries used. Deposition efficiency (DE) in the bifurcation region increased with increasing Stk but did not change with branching angles between 30° and 45°. The diameter ratio showed only a minor effect on DE. The results suggest that Stk may be the single most important factor for particle deposition in the bifurcating airways in the inertial regime.

Generation of Radiolabeled "Soot-Like" Ultrafine Aerosols Suitable for Use in Human Inhalation Studies

We have developed a method for radiolabeling ultrafine carbon particle aggregates with technetium-99m. The carbon aggregate aerosol was chosen to mimic the physical properties of urban combustion or soot-like particulate. The radioisotope is a short lived (t1/2 = 6.02 h) gamma emitter commonly used in human studies where scintigraphic methods are employed. Primary carbon parti cles, the aggregation of which is controlled by concentration and time, were produced by arcing between graphite electrodes under an argon atmosphere. Radiolabeling of particles was accomplished by applying a pertechnetate solution onto the tips of electrodes prior to arcing. The activity median diameter of experimental aerosols could be varied from 50 to 150 nm. The specific activity of aerosols increased with the amount of activity applied to the electrodes and decreased with time of generator operation. In-vitro leaching of the radioisotope from particles into solution was also measured. Leaching appeared to increase with the specific activity of the aerosol but was not affected by particle size.

The glutathione-S-transferase mu 1 (GSTM1) null genotype and increased neutrophil response to low-level ozone (0.06 ppm)

associated with IFN-g therapy at doses up to 200 mg/m; she shows slow clinical improvement characterized by weight gain and absence of fever and diarrhea. We have described a case of composite heterozygousmutations of IL12RB1 gene encoding for the b1 subunit of IL-12 receptor that is associated with disseminated M genavense infection. In a recent survey of 141 patients with IL-12Rb1 deficiency, isolated BCG infection has been observed in most patients (43 subjects of 102 index cases), environmental mycobacteria were observed in 6 patients, and the remaining patients had infections caused byMycobacterium tuberculosis (2 patients), other intracellular pathogens (mostly Salmonella, but also Klebsiella and Nocardia species), or combinations of the above-described pathogens. Infection by M genavense was reported in a single patient with IL-12Rb1 deficit, suggesting that this pathogen is a rare cause of MSMD. In addition, IL-12Rb1 deficiency has incomplete clinical penetrance because 8 of 29 known genetically affected siblings investigated in the survey did not develop MSMD-related infections. This observation suggests that environmental factors, including the route of infection (eg, subcutaneous injection of BCG), or the use of immunosuppressant drugs can facilitate the development of disseminated infections as observed in our patient who was receiving an immunosuppressive drug for the treatment of autoimmune hepatitis. Likewise, M genavense infection was reported in patients receiving immunosuppressive therapy after transplantation or in patients with AIDS. Development of lymphopenia is not usually observed in patients with IL-12Rb1 deficiency, although the patient that we describe has shown a profound lymphopenia that might be related to a defect of lymphocyte generation in bone marrow or to intestinal lymphangiectasia. In conclusion, our observation suggests that development of disseminated mycobacterial infection in patients receiving immunosuppressive treatment could constitute a presenting phenotype of MSMD. Laura Tassone, PhD Anna Cristina C. Carvalho, MD, PhD Alessandra Calabresi, MD Enrico Tortoli, MD Alessandra Apostoli, MD Omar Scomodon, PhD Cecilia Spina, PhD Donatella Vairo, PhD Vincenzo Villanacci, MD Alberto Matteelli, MD* Raffaele Badolato, MD, PhD*

Monodisperse and polydisperse aerosol deposition in a packed bed

Although polydisperse aerosols in ambient and occupational settings have been associated with adverse health effects, researchers have mostly used monodisperse aerosols to investigate particle deposition in the human lung. The objective of this work was to determine whether the deposition of a series of monodisperse aerosols is reasonable to simulate the deposition of a polydisperse aerosol. A packed bed was used as an approximate surrogate to the human lung. Polydisperse and monodisperse sebacate aerosols were generated by nebulizers and a Monodisperse Aerosol Generator (MAGE), respectively. A Harvard respirator pump inhaled and exhaled aerosol through the packed bed. Complete size distributions of inhaled and exhaled aerosol were measured by an Aerodynamic Particle Sizer (APS) and a Scanning Mobility Particle Sizer (SMPS). The deposition for discrete sections of polydisperse aerosols was compared with the deposition of monodisperse aerosols. Also, the total deposition of a polydisperse aerosol was compared with the deposition of a series of monodisperse aerosols that formed the same size distribution as the polydisperse aerosol. Experiments were run with and without a charge neutralizer. With the neutralizer, no difference in deposition occurred between the discrete sections of polydisperse and monodisperse aerosols. Thus, total deposition was the same for both a polydisperse and a series of monodisperse aerosols, indicating that a series of monodisperse aerosols is reasonable to represent a polydisperse aerosol. Without a charge neutralizer, discrete sections of polydisperse aerosols with particle diameters of 3 w m or greater deposited no differently than they did with a neutralizer. However, for particle diameters of 1 w m or less, deposition of discrete sections of polydisperse aerosols was greater than that of monodisperse aerosols. Thus, total deposition was greater for polydisperse aerosols than for a series of monodisperse aerosols, indicating the need to condition aerosol with a neutralizer after the nebulization of a sebacate/alcohol solution.

A polydisperse aerosol inhalation system designed for human studies

Abstract A polydisperse aerosol inhalation system has been developed to measure particle deposition in the lungs of human subjects. Nebulizers are used to generate aerosols with mass median aerodynamic diameters from 0.3 to 3 μm , and geometric standard deviations of 1.8–2.0. Inspired aerosol is drawn from a holding bag, passes through a sliding valve and a pneumotachograph, and enters a heated mouthpiece. Exhaled aerosol passes from the mouthpiece and pneumotachograph, through a second sliding valve and is collected in a heated sample bag. Inhalation and exhalation valves trigger automatically with change in flow direction through the pneumotachograph. Complete size distributions of inhaled and exhaled aerosol are measured by an aerodynamic particle sizer and a scanning mobility particle sizer. Fractional particle deposition of a test aerosol in the lung is determined by comparing inhaled and exhaled aerosol size fractions. Total deposition is determined from the sum of the fractional depositions. This new system precludes the need for monodisperse aerosol series to simulate polydisperse aerosol data, thus substantially reducing both study length and subject exposure.