Date of Degree
PhD (Doctor of Philosophy)
Occupational and Environmental Health
Thomas M. Peters
This work strived to increase knowledge of assessing airborne nanoparticles in the workplace by characterizing nanoparticle concentrations in a workplace using direct-reading instruments, evaluating a DC2000CE diffusion charger, and the creation of a personal diffusion battery (pDB).
Direct-reading instruments were used with aerosol mapping and task monitoring to evaluate airborne nanoparticle concentrations in an apparel company that produces waterproof jackets composed of polytetrafluoroethylene membrane laminated fabric. Jacket production required that sewn seams be sealed with waterproof tape applied with hot air (600°C). Particle number concentrations were greater in the sewing and sealing areas than the office area while respirable mass was negligible throughout the facility. The breathing zone particle number concentrations of the workers who sealed the sewn seams were highly variable and significantly greater when sealing seams than when conducting other tasks (p<0.0001). The effectiveness of the canopy hoods used to ventilate sealing operations was poor. These measurements support the idea that work places were hot processes are conducted may have substantially greater concentrations of airborne nanoparticles than background measurements even with control measures in place.
Laboratory tests were conducted to evaluate a commercially available diffusion charger, the DC2000CE, that measures nanoparticle surface area concentration. The surface area concentrations of unimodal and multimodal polydispersed aerosols measured by the DC2000CE were less than the surface area concentrations measured by the reference instruments. The differences in results were attributed to a difference of measuring active versus geometric surface area concentration and the design of the DC2000CE. The maximum measurable active surface area concentration (2,500 mm2 m-3) was found to be greater than the manufacturer stated maximum (1000 mm2 m-3). Moving or vibrating a DC2000CE while taking measurements can cause the appearance of increased surface area concentration results. The DC2000CE has limitations that must be acknowledged when using the DC2000CE to measure airborne nanoparticle surface area concentrations in a workplace.
A four stage pDB (3.2 kg) composed of a screen-type diffusion battery, solenoid valve system, and an electronic controller was developed. The pDB was combined with a CPC and a data inversion was created that could be used to solve for the number median diameter, geometric standard deviation, and particle number concentration of a unimodal distribution. The pDB+CPC with inversion was evaluated using unimodal propylene torch exhaust and incense exhaust. For particle number concentration of particles with diameters less than 100 nm, the pDB+CPC with inversion results were between 86% to 109% of reference instrument results when the inversion did not solve to an inversion constraint and between 6% to 198% for results that solved to an inversion constraint. When coupled with a direct-reading instrument, the pDB with an inversion was able to measure the size distribution of particles with a NMD smaller than 290 nm.
Copyright 2010 Donna Jean Holzer Vosburgh
Vosburgh, Donna Jean Holzer. "Use of direct-reading instruments for measuring airborne nanoparticles in the workplace." dissertation, University of Iowa, 2010.