James B. D'Arcy

Experimental Measurements of the Independent Effects of Dilution Ratio and Filter Temperature on Diesel Exhaust Particulate Samples

A dilution mini-tunnel is described that collects diesel exhaust particulate samples with independent control of dilution ratio and sample filter temperature. The small dilution system requires no pumps or blowers and offers much flexibility in controlling the dilution process. Experiments were conducted with the dilution system to establish individual effects of filter temperature and dilution ratio on particulate samples collected by filtration from the exhaust of an automotive diesel engine. Exhaust particulate aerosol was generated with a single-cylinder test engine operating at constant load and speed. Increasing filter temperature from 35-100 degrees C while maintaining a constant 10.8:1 dilution ratio decreased particulate mass by about 13%. Increasing the dilution ratio from 5:1 to 100:1 at a constant filter temperature of 52 degrees C decreased particulate mass by about 26%. These changes were attributed to variations in the soluble portion of the particulate sample. Supplemental information is appended on dilution system development, residence time and filter material effects on particulate mass, and dilution ratio calculation.

Physical and Chemical Characterization of Airborne Particles from Welding Operations in Automotive Plants

Airborne particles were characterized from six welding operations in three automotive plants, including resistance spot welding, metal inert gas (MIG) welding and tungsten inert gas (TIG) welding of aluminum and resistance spot welding, MIG welding and weld-through sealer of galvanized steel. Particle levels were measured throughout the process area to select a sampling location, followed by intensive particle sampling over one working shift. Temporal trends were measured, and particles were collected on filters to characterize their size and chemistry. In all cases, the particles fell into a bimodal size distribution with very large particles >20 μm in diameter, possibly emitted as spatter or metal expulsions, and very small particles about 1 μm in diameter, possibly formed from condensation of vaporized metal. The mass median aerodynamic diameter was about 1 μm, with only about 7% of the particle mass present as ultrafine particles <100 nm. About half the mass of aluminum welding particles could be accounted for by chemical analysis, with the remainder possibly present as oxygen. Predominant species were organic carbon, elemental carbon, iron, and aluminum. More than 80% of the particle mass could be accounted for from steel welding, primarily present as iron, organic carbon, zinc, and copper. Particle concentrations and elemental concentrations were compared with allowable concentrations as recommended by the Occupational Safety and Health Administration and the American Conference of Governmental Industrial Hygienists. In all cases, workplace levels were at least 11 times lower than recommended levels.

Characterization of Fine Particles from Machining in Automotive Plants

Sampling of the full range of particle sizes was carried out on 16 processes in six different General Motors plants over a period of 2.5 years. This article deals with particle characterization from five of the processes that relate to machining, specifically, wet machining with water-based fluids from old and new technology processes, grinding with straight oils from old and new technology processes, and dry machining. The concentrations measured by different instruments were in reasonable agreement, although the light-scattering instrument generally produced higher values than filters. Of the processes studied, the old technology grinding using straight oils generated the highest particle concentrations. The new technology controls (enclosed, vented machines) were highly effective but more so for large particles than small particles. The particle size distribution was shifted to smaller particles with enclosed processes. Dry machining generated the largest particles of all processes studied.

Size Characteristics of Machining Fluid Aerosols in an Industrial Metalworking Environment

Abstract In an industrial metalworking environment, workplace aerosols are produced continuously during normal operations as machining fluids flood the cutting or grinding tools at the machined surfaces. Since aqueous, synthetic fluids and soluble oils have replaced straight oils for the most part, the physical characteristics of the machining fluid aerosols should be determined to facilitate the assessment and control of potential health hazards in an industrial metalworking environment. The size distributions and mass concentrations of machining fluid aerosols in an automotive transmission manufacturing plant were determined by cascade impactors, real-time aerosol monitors, and a new area respirable impactor. The aerosols sampled at six sampling sites within the plant were found to be polydispersed with large droplets greater than 8 μm in aerodynamic mass median diameter and fine particles in the 0.1–1 μm size range. The large aerosols were formed from the direct spraying of machining fluids or from emi...

Mechanism of induction of asthmatic attacks initiated by the inhalation of particles generated by airbag system deployment

OBJECTIVE We have previously demonstrated that inhalation of the dust produced by dual frontal airbag deployment can result in significant bronchospasm in approximately 40% of mild to moderate asthmatics. This study was performed to determine the cause of the asthmatic response. DESIGN Controlled laboratory study. MATERIALS AND METHODS Asthmatics who were previously tested for their response to airbag effluents were exposed for twenty minutes to either 1) airbag effluents from airbag systems in which the airbag was insulated from the hot deployment module; 2) non-sulfur containing airbag effluents; 3) sodium chloride aerosol; or 4) sodium carbonate-bicarbonate aerosol (pH 10). Pre-exposure, post-exposure, and 2 hour post exposure pulmonary spirometry and mechanics were measured. Subjects filled out symptoms questionnaires before exposure, 2, 4, 8, 12, and 19 minutes into the exposure, immediately post-exposure, and 2 hours post-exposure. MEASUREMENTS AND MAIN RESULTS Prevention of the pyrolysis of the passenger-side bag as it rested on the hot module after deployment did not diminish the asthmatic response. Removal of sulfur-containing oxidants from the airbag pyrotechnic chemistry, which may have led to sulfite production, similarly did not alleviate the asthmatic response to the airbag effluents. Lastly, when asthmatics were exposed to sodium chloride and sodium carbonate-bicarbonate aerosols at approximately the same concentration (approximately 220 mg/m3) as the airbag aerosol concentration that occurred in the in-car tests, they had responses similar to those produced by the airbag exposures. CONCLUSIONS We conclude that the amount of soluble particulate contained in the aerosol discharged into the passenger compartment by dual frontal airbag deployment is largely the cause of the observed evoked asthmatic attacks. The alkaline pH of the airbag and carbonate aerosols may have added an additional degree of provocation.

THE USE OF A TRANSPORTABLE FOURIER TRANSFORM INFRARED (FTIR) SPECTROMETER FOR THE DIRECT MEASUREMENT OF SOLVENTS IN BREATH AND AMBIENT AIR—I: METHANOL

A transportable Fourier transform infrared (FTIR) spectrometer has been tested for analysis of methanol vapor in alveolar and ambient air. The instrument has been found to be accurate and precise for both uses. The regions used for methanol and CO2 quantification are in the vicinity of 950-1100 cm-1 and 2000-2100 cm-1, respectively. The results of a standard addition experiment show a correlation coefficient of 0.97-0.99 for methanol in alveolar or ambient air at the 30-200 ppm concentration level. For CO2 analysis in 23 alveolar air samples at the 6.1-7.6% concentration level, the mean difference in results between a nondispersive infrared (NDIR) spectrometer and the FTIR was -0.092% with a standard deviation of 0.273% (p greater than 0.1). Methanol concentrations in alveolar air paralleled simultaneous measurements of methanol concentration in blood. Overall, these preliminary results suggest that FTIR spectroscopy is a practical and efficient approach for simultaneous biological and area monitoring of human exposure to organic solvents.

High-Solids Paint Overspray Aerosols in a Spray Painting Booth: Particle Size Analysis and Scrubber Efficiency

Particle size distributions of high-solids acrylic-enamel paint overspray aerosols were determined isokinetically in a downdraft spray painting booth in which a 7-stage cascade impactor was used. Three different industrial paint atomizers were used in this study, and the paint aerosols were characterized before and after a paint booth scrubber. The mass median aerodynamic diameter (MMAD) of a metallic basecoat and an acrylic clearcoat paint aerosol from air-atomized spray guns ranged from 4-12 µm and was dependent on atomization pressure. The clearcoat paint aerosols also were generated from rotary atomizers and had MMADs, which ranged from 20-35 µm depending on rotational speed. When the paint booth was operated under controlled conditions simulating those in a plant, the collection efficiency of paint overspray aerosols by a paint scrubber was found to be size dependent and decreased sharply for particles smaller than 2 µm to as low as 64% for clearcoat paint particles of 0.6 µm. Based on the performanc...

DNA synthesis in pulmonary alveolar macrophages and type II cells: Effects of ozone exposure and treatment with α‐difluoromethylornithine

An increase in the number of pulmonary alveolar macrophages (AM) can be induced by a number of toxic insults to the lung, including ozone, an important photochemical oxidant air pollutant. This increase could arise from an influx of monocytes from the vascular or interstitial compartments, or from proliferation of AM in situ. While proliferation of alveolar type II cells after oxidant exposure has been well documented, it is not clear whether AM are also capable of this response. Rats were exposed to air or to 0.12, 0.25, or 0.50 ppm ozone for 1, 2, 3, 7, or 14 d, 20 h/d. The labeling index in both AM and type II cells increased about 10-fold after 2 d of exposure to 0.25 and 0.50 ppm of ozone, but returned to control levels by the end of 1 wk of exposure. These changes closely paralleled the temporal and dose-response characteristics of changes in total lung DNA synthesis. alpha-Difluoromethylornithine (DFMO) administered to rats during a 2-d exposure to 0.50 ppm ozone did not inhibit the ozone-induced increase in labeling index in AM or type II cells, although evidence of inhibition of lung ornithine decarboxylase activity was obtained, and the ozone-induced increase in total lung DNA synthesis was inhibited by 23%. These results suggest that, like type II cells, AM are capable of entering the cell cycle and synthesizing new DNA in situ in response to short-term exposure to environmentally relevant doses of ozone, and that the ozone-induced stimulation of DNA synthesis in these cell types was refractory to inhibition by DFMO.

Breath monitoring of inhalation and dermal methanol exposure

Abstract A fundamental assumption of monitoring breath for a toxicant is that the concentration of the toxicant in breath is proportional to the concentration in blood. The present study was designed, in part, to assess the conditions under which measurement of methanol in breath would be useful for estimating the blood concentration of methanol following inhalation or dermal exposures to methanol. Paid volunteer subjects underwent controlled inhalation exposure to methanol vapor at various concentrations for 8 hours, or dermal exposures (without inhalation exposure) to methanol for varying periods of time. Blood and end-expiratory air were analyzed for methanol from samples obtained prior to exposures, and at various times during and after exposures. The results demonstrate that blood and breath concentrations of methanol are disproportional for varying periods of time during and following cessation of methanol exposure, depending on the route of exposure (dermal versus inhalation). In settings where the...

Inhaled particle retention in rats receiving low exposures of diesel exhaust

To study the effects of a low concentration exposure on the retention and clearance of submicron particles from the lungs, we exposed male Fisher 344 rats to diesel exhaust diluted to 50 micrograms diesel exhaust particles (DP)/m3, 20 h/d, 7 d/wk for 52 wk. Lung burdens (amount of DP in lungs) and the alveolar macrophage burdens were measured up to 52 wk postexposure. By 1 yr postexposure at least 80% of the DP was eliminated from the lungs and similarly cleared from the lavaged pool of macrophages. The DP remaining in the lungs was observed in alveolar, parabronchial and paravascular maculae. In contrast to previous high concentration exposure studies, only trace amounts of particles were observed in the mediastinal lymph nodes. To study the concentration dependence of particle retention, rats were exposed to equivalent exposures of 18 d x mg DP/m3 delivered at 5700 micrograms/m3 for 3 d, 1600 micrograms/m3 for 12 d, 250 micrograms/m3 for 72 d, or 50 micrograms/m3 for 365 d. Higher lung and macrophage burdens were initially achieved with the brief, high concentration exposures. During the postexposure period, animals exposed to the higher concentrations cleared more of the lung burden. Exposure to lower concentrations resulted in higher long-term lung burdens. These results are consistent with a model of lung clearance in which the macrophage burden and the duration of exposure are both important to the formation of the maculae. In a brief high concentration exposure, the macrophage burden rises rapidly, but then declines rapidly. However, in longer low concentration exposures, the macrophage burden will not reach the same peak, but stays at intermediate levels during the exposure and stimulates a steady development of the lung maculae from particle-laden macrophages leaving the active pool of pulmonary phagocytes.