Acute exposure of humans to low levels of ozone are known to cause decreases in FVC and increases in SRaw. These alterations in lung function do not, however, elucidate the potential for acute small airway responses. In this study we employed a test of aerosol dispersion to examine the potential effects of ozone on small airways in humans. Twenty-two healthy nonsmoking male volunteers were exposed to 0.4 ppm ozone for 1 h while exercising at 20 L/min/m2 body surface area. Before and immediately after exposure, tests of spirometry (FVC, FEV1, and FEF25-75) and plethysmography (Raw and SRaw) were performed. Subjects also performed an aerosol dispersion test before and after exposure. Each test involved a subject inhaling five to seven breaths of a 300-ml bolus of a 0.5 micron triphenyl phosphate aerosol injected into a 2-L tidal volume. The bolus was injected into the tidal breath at three different depths: at Depth A the bolus was injected after 1.6 L of clean air were inhaled from FRC, at Depth B after 1.2 L, and at Depth C after 1.2 L but with inhalation beginning from RV. The primary measure of bolus dispersion was the expired half-width (HW). Secondary measures were the ratio (expressed as percent) of peak exhaled aerosol concentration to peak inhaled concentration (PR), shift in the median bolus volume between inspiration and expiration (VS), and percent of total aerosol recovered (RC). Changes in pulmonary function after ozone exposure were consistent with previous findings.(ABSTRACT TRUNCATED AT 250 WORDS)
Operating parameters and performance characteristics are described for a dry-powder Fe2O3 aerosol disperser used for periods up to 23 h with minimal operator attention. Aerosol mass concentration fluctuations in a 3 m3 dynamic-flow chamber were determined over 23-h periods for the aerosol generator with and without electronic feedback circuits. From the data presented in this paper and from observations made during 2 weeks of continuous operation, this ``rust duster'' was found to be capable of continuously dispersing Fe2O3 powder into 1.5 m3 of air per minute to produce aerosols having median concentrations from about 0.7 to 3.0 mg m−3. Over most of this concentration range, with or without the feedback control circuit, the mass concentration of Fe2O3 aerosol was kept within the ±50% variability limit originally set as acceptable for chronic animal exposure conditions.
An instrument is described that counts automatically according to size aerosol particles of certain specific chemical compositions. The technique employed depends on converting to current pulses the ions produced from airborne particles passing through the combustion zone of a flame. Because the amplitude of the current pulse resulting from an ionized particle passing through a flame is dependent on both the mass and the ionization potential of the particle, the FIPAPA can aid in submicron aerosol particle identification when used in combination with instruments employing other sensing zone types. By use of electronic pulse-height circuits, these current pulses are subsequently counted in six ranges of magnitude. The minimum size particle detectable was found to be 0.15 p. diam for KOH and 0.25 p. diam for NaC!.
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