Stephen V. Teague

Sidestream Cigarette Smoke Generation and Exposure System for Environmental Tobacco Smoke Studies

AbstractPrevious studies of the effects of environmental tobacco smoke have used artificial systems for generating aged and diluted sidestream cigarette smoke. Generally these systems have been designed for large chambers, which require expensive smoking machines, use large air flows, and are labor-intensive. We present a new method for producing sidestream smoke and describe an exposure system for smaller chambers that collects, ages, and dilutes smoke to simulate environmentally relevant conditions. Furthermore, our system is relatively inexpensive, maintains consistent levels of total suspended particulates (TSP) and carbon mon-oxide that can be set at a variety of concentrations, and significantly reduces the manual component of exposure studies.

Reduced Lung Cell Proliferation Following Short-Term Exposure to Ultrafine Soot and Iron Particles in Neonatal Rats: Key to Impaired Lung Growth?

Particulate matter (PM) has been associated with a variety of negative health outcomes in children involving the respiratory system and early development. However, the precise mechanisms to explain how exposure to airborne particles may cause adverse effects in children are unknown. To study their influence on early postnatal development, a simple, laminar diffusion flame was used to generate an aerosol of soot and iron particles in the size range of 10 to 50 nm. Exposure of 10-day-old rat pups to soot and iron particles was for 6 h/day for 3 days. The lungs were examined following a single injection of bromodeoxyuridine (BrdU) 2 h prior to necropsy. Neonatal rats exposed to these particles demonstrated no effect on the rate of cell proliferation within terminal bronchioles or the general lung parenchyma. In contrast, within those regions arising immediately beyond the terminal bronchioles (defined as the proximal alveolar region), the rate of cell proliferation was significantly reduced compared with filtered air controls. These findings strongly suggest exposure to airborne particles during early neonatal life has significant direct effects on lung growth by altering cell division within critical sites of the respiratory tract during periods of rapid postnatal development. Such effects may result in altered growth in the respiratory system that may be associated with lifelong consequences.

An aerosolized fluorescent microsphere technique for evaluating particle deposition in the avian respiratory tract

Abstract The objective of this study was to examine the feasibility of using aerosolized fluorescent microspheres to examine particle distribution in the respiratory tract of birds following aerosol exposure. Adult domestic pigeons (Columbia livia domestica; n = 5 birds per microsphere size) were exposed to aerosolized monodispersed populations of various sized carboxylate microspheres (0.5, 1.0, 2.0, 3.0, 6.0, and 10.0 μm) for 30 min. For aerosol-exposure purposes, the birds were anesthetized with injectable anesthetics, intubated, and placed on positive-pressure ventilation using a mechanical ventilator. Immediately following aerosol exposure, the birds were euthanatized, and carcasses were preserved via intravenous infusion of modified paraformaldehyde/gluteraldehyde fixative (pH = 7.2 and 340 mOsm). Initial evaluation of microsphere distribution in air sacs (cranial and caudal thoracic and abdominal) and at the level of the ostia was performed using a stereoscopic microscope with an epifluorescent module. More detailed examination of the distribution of microspheres within the respiratory tract was achieved using a confocal scanning laser microscope with a krypton argon laser and a scanning electron microscope. The results from this study revealed that positive-pressure ventilation resulted in distribution of smaller sized fluorescent microspheres (sizes 1.0, 2.0, and 3.0 μm) throughout the pigeons respiratory tracts, and these microspheres were in highest concentration in the secondary bronchi and ostia for all of the examined air sacs. The larger sized beads (6.0 and 10.0) were confined to the upper airway (trachea and primary bronchi). The results from this study allow for a better understanding of particle deposition following positive-pressure ventilation and aerosol exposure in birds.

Effect of inhaled dimethylselenide in the Fischer 344 male rat

In this project, a total of 60 adult Fischer 344 male rats were exposed to dimethylselenide (DMSe) vapor at 1607, 4499, or 8034 ppm for 1 h (20 rats/group). In addition, 26 unexposed rats were used as controls. The exposed rats were observed frequently during the 7 d following exposure and appeared normal. The animals were sacrificed at either 1 or 7 d after inhalation and the major tissues were grossly examined and weighed. Selenium levels were found to be elevated only in the lung at d 1. At d 1, significant changes in organ weights were an increase in the lung weight at exposure levels of 1607 and 8034 ppm of DMSe and in liver weight at 4499 and 8034 ppm. At d 1, significant changes in the lung were an increase in protein at 1607 and 8034 ppm of DMSe, and an increase in RNA and a reduction in DNA at 4499 ppm DMSe. The only change in the liver was a reduction in DNA at 4499 ppm. At 7 d, the protein content and RNA content of spleen were increased. Lung, liver, kidney, spleen, thymus, lymph nodes, pancreas, and adrenal gland were examined microscopically and found to be normal. All of these observed responses were minor and did not severely impact the health of the rats. Overall, the data indicate that the inhalation of DMSe for 1 h has relatively low toxicity in rats even at high concentrations.

Study of Nebulization Delivery of Aerosolized Fluorescent Microspheres to the Avian Respiratory Tract

SUMMARY. This study investigated the delivery of an aerosol of monodisperse microspheres to the respiratory tract of birds following aerosol exposure. Adult domestic pigeons (Columbia livia domestica, n  =  5 birds per timed treatment) were exposed to an aerosol of fluorescent 1.0-µm diameter carboxylate microspheres for 0.5, 1, 2, or 4 hr. During the aerosolization period, the birds were free-standing in a plexiglass treatment chamber and the aerosol was delivered using a commercial nebulizer. Immediately following aerosol exposure, the birds were euthanatized and the carcasses were intravenously infused with a modified paraformaldehyde/gluteraldehyde fixative. Evaluation of microsphere distribution was performed using a stereoscopic microscope with an epifluorescent module. The results from this study revealed that the amount of aerosolized particles delivered using a commercial nebulizer was proportional to exposure periods. Aerosol exposure periods of 0.5 hr or 1 hr did not result in a readily observable distribution of 1.0 µm fluorescent microspheres to the cranial thoracic, caudal thoracic, or abdominal air sac membranes. This was partly attributed to the relatively low concentration of the individual monodisperse microspheres in the aerosolized suspension. The 2- and 4-hr exposure periods resulted in readily observable deposition of the 1.0 µm fluorescent microspheres in the cranial thoracic, caudal thoracic, or abdominal air sac membranes, with the 4-hr exposure period resulting in the greatest number of particles on the membrane surfaces. For each of the exposure periods, there was individual animal variation regarding the distribution and relative number of spheres deposited. This study demonstrates the widespread deposition of particles that had an aerodynamic equivalent diameter of approximately 1 µm and provides a better understanding of particle deposition efficiency within the respiratory system following aerosol exposure in birds. RESUMEN. Estudio de la aplicación por nebulización en aerosol de microesferas fluorescentes en el tracto respiratorio de las aves. En este estudio se investigó la entrega de un aerosol de microesferas monodispersas en el tracto respiratorio de las aves después de la exposición a un aerosol. Palomas domésticas adultas (Columba livia domestica, n  =  5 aves por tiempo de tratamiento) fueron expuestos a un aerosol de microesferas de carboxilato fluorescentes de un diámetro de una 1.0 micra por diferentes tiempos de exposición: 30 minutos, una hora, dos horas, o cuatro horas. Durante el período de aerosolización, las aves se alojaron en una cámara de tratamientos de plexiglass y el aerosol se entregó mediante un nebulizador comercial. Inmediatamente después de la exposición a los aerosoles, se practicó la eutanasia de las aves y los cadáveres fueron infundidos por vía intravenosa con una solución fijadora modificada de paraformaldehído/glutaraldehído. La evaluación de la distribución de microesferas se realizó utilizando un microscopio estereoscópico con un módulo de epifluorescencia. Los resultados de este estudio revelaron que la cantidad de partículas de aerosol administradas utilizando un nebulizador comercial era proporcional a los periodos de exposición. Los períodos de exposición a los aerosoles de 30 minutos o de una hora no proporcionaron una distribución fácilmente observable de las microesferas fluorescentes de 1.0 micra en las membranas de los sacos aéreos torácicos craneales, torácicos caudales, o abdominales. Esto se atribuyó en parte a la concentración relativamente baja de microesferas monodispersas individuales en la suspensión de aerosol. Los periodos de dos y cuatro horas de exposición dieron lugar a la deposición fácilmente observable de las microesferas fluorescentes en las membranas de los sacos aéreos torácicos craneales, torácicos caudales o abdominales, y el período de exposición de 4 horas dio por resultado el mayor número de partículas en las superficies de las membranas. Para cada uno de los períodos de exposición, hubo una variación para cada animal en individual, con relación a la distribución y al número relativo de las esferas depositadas. Este estudio demuestra la deposición generalizada de partículas que tenían un diámetro aerodinámico de aproximadamente una micra, y proporciona un mejor entendimiento de la eficiencia en la deposición de partículas dentro del sistema respiratorio después de la exposición a aerosoles en las aves.

Dust Generator for Inhalation Studies with Limited Amounts of Archived Particulate Matter

A novel design for a dry-aerosol generator that efficiently produces a well-dispersed dust suspension using small quantities of a PM2.5-enriched powder sample is described. The motivation to develop a highly efficient dry-aerosol particle generator was to facilitate collaborative projects that combine in vitro cell culture experiments and multiday inhalation exposures using a single batch of well-characterized particles. Premixing of the test particles with larger diameter glass beads permits delivery of aerosol concentrations from 100–1000 μ g/m3 to an exposure chamber using only milligram quantities of the test powder per hour. Examination of exposure chamber filter samples by scanning electron microscopy showed well-dispersed particles of the test powder free of glass spheres or fragments. Data are presented from experiments using coal fly ash as the test powder to illustrate the system performance.

Generation of fume aerosols of zinc oxide

Fume aerosols of zinc oxide were generated by nebulization of aqueous solutions of zinc acetate (30 milligrams zinc acetate per milliliter water), with subsequent thermal vaporization and chemical degradation to the oxide. A Retec nebulizer operated with compressed air was used to generate the zinc acetate mists which were passed through a quartz tube furnace (1150 degrees C) to dry the droplets and degrade the acetate to the oxide form. Ultrafine particles were formed in this process, demonstrating that zinc acetate was vaporized as aerosol entered the heated tube prior to thermolysis. The few larger particles probably represent those larger droplets which do not completely vaporize prior to thermolysis. Cascade impactor samples indicated a mass median aerodynamic diameter (MMADar) of 0.8 +/- 0.1 (SD) microns with geometric standard deviation (sigma g) of 2.9 +/- 0.5 (SD). About 25% of the zinc was associated with particles smaller than 0.3 microns in aerodynamic diameter, equivalent to spherical particles smaller than 0.09 microns in geometric diameter.

Chemical characterization of respirable coal-oil-mixture fly ash

Abstract This paper reports the elemental analysis of respirable (VMD = 2.6 μm) baghouse collected fly ash from the combustion of a slurry of 60% oil and 40% coal. Compared to coal fly ash, this material has high concentrations of several trace elements, with the vanadium and nickel levels contributed by the oil being particularly high. Trace elements originating from the oil are highly enriched in the respirable ash. Leaching the coal-oil-mixture particles in HCl shows that the heavy metals are generally more soluble than is typical of coal fly ash.

Aerosolization System for Experimental Inhalation Studies of Carbon-Based Nanomaterials

Assessing the human health risks associated with engineered nanomaterials is challenging because of the wide range of plausible exposure scenarios. While exposure to nanomaterials may occur through a number of pathways, inhalation is likely one of the most significant potential routes of exposure in industrial settings. An aerosolization system was developed to administer carbon nanomaterials from a dry bulk medium into airborne particles for delivery into a nose-only inhalation system. Utilization of a cannula-based feed system, diamond-coated wheel, aerosolization chamber, and krypton-85 source allows for delivery of otherwise difficult to produce respirable-sized particles. The particle size distribution (aerodynamic and actual) and morphology were characterized for different aerosolized carbon-based nanomaterials (e.g., single-walled carbon nanotubes and ultrafine carbon black). Airborne particles represented a range of size and morphological characteristics, all of which were agglomerated particles spanning in actual size from the nanosize range (<0.1 μm) to sizes greater than 5 and 10 μm for the particles largest dimension. At a mass concentration of 1000 μg/m3, the size distribution as measured by the inertial impactor ranged from 1.3 to 1.7 μm with a σg between 1.2 and 1.4 for all nanomaterial types. Because the aerodynamic size distribution is similar across different particle types, this system offers an opportunity to explore mechanisms by which different nanomaterial physicochemical characteristics impart different health effects while theoretically maintaining comparable deposition patterns in the lungs. This system utilizes relatively small amounts of dry material (<0.05 g/h), which may be beneficial when working with limited quantity or costly nanomaterials. Copyright 2012 American Association for Aerosol Research

Effect of the inhalation of zinc and dietary zinc on paraquat toxicity in the rat

Abstract A possible pharmacological effect of zinc against the pulmonary toxicant paraquat has been studied. Rats were treated with zinc either by inhalation of zinc oxide fume aerosol or consumption of zinc supplemented food. The animals were then injected with paraquat ip (30 mg/kg) and lethality monitored for 7 days. Neither zinc inhalation nor dietary zinc protected the animals against paraquat-induced lethality. In fact, exposure of rats to zinc oxide fume aerosol potentiated the lethal effects of paraquat. The mechanism of paraquat-induced lung toxicity at the cellular level does not appear to directly involve a zinc-dependent step. This distinguishes paraquat from other injurious agents which have been reported to respond to zinc.