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.

The purpose of this study was to evaluate the performance of scanning mobility particle sizers in the characterization of nanoaerosols. A sampling chamber was constructed from aluminum and tempered glass, had a volume of 4.6 cubic feet, and was designed for the introduction of aerosols and dilution air, maintenance of aerosol concentration, and continuous exhaust of chamber air. Penetration and aerosol distribution tests were conducted within the chamber. An aerosol generation and measurement system comprised of nitrogen gas, BGI 3 jet Collison Nebulizer, diffusion dryer, aerosol charge neutralizer, mixing chamber, critical orifice, hygrometer, condensation particle counter, scanning mobility particle sizer, air sampling pump, air sampling cassettes, and a vacuum pump was assembled. A BGI 3 jet Collison Nebulizer was used to generate the nanoparticle aerosols. The two types of nanoparticle aerosols utilized in the experiment were salt (NaCl) and polystyrene latex (PSL) spheres. Relative humidity and temperature measurements were obtained within the chamber. Real-time, direct-reading particle measurement instruments including a condensation particle counter (CPC) (TSI, Model 3007), and three scanning mobility particle sizer (SMPS) instruments (Particle Measuring Systems, Nano-ID NPS500; TSI, NanoScan SMPS Nanoparticle Sizer Model 3910) were used for particle measurements. For each test run, two air samples were collected on membrane filters for electron microscopy (EM) analysis. Eight trials were conducted using NaCl nanoaerosols, and twelve trials were conducted using PSL spheres. The selected particle sizes for the experiments were 57 nm, 92 nm, 147 nm, and 220 nm. For the NaCl nanoaerosol suspensions, the SMPS lines of fit were log-normally distributed and predominantly parallel. The geometric standard deviation (GSD) of these distributions was approximately 1.7, which confirms that the distributions were approximately the same. In these experiments, instrument 3 identified a higher percentage of NaCl particles within the size range intervals of the selected NaCl size parameter, and the count median diameters (CMDs) for the instrument 3 measurements were closer to the selected NaCl size parameter more often than the other instruments. This suggests that instrument 3 was more responsive than the other instruments to the selected size range and the selected NaCl size parameters. The electron microscopy (EM) lines of fit for the NaCl experiments were predominantly parallel with the SMPS lines of fit, suggesting that the log-normally distributions are similar. The GSD of EM distributions was approximately 1.8, which confirms that the distributions were approximately the same as the SMPS distributions. Results from the regression plots demonstrated that the main effects and interaction were statistically significant with a p<0.0001. The coefficient of determination, R2, for the regression lines was 0.87. The post-hoc Tukey HSD results identified a significant difference between the instrument 3 dataset, and the datasets for instruments 1 and 2. For the PSL nanoaerosol suspensions, the SMPS lines of fit were log-normally distributed and predominantly parallel. The GSD of these distributions was approximately 1.3, which confirms that the distributions were approximately the same. In these experiments, instrument 2 identified a higher percentage of PSL particles within the size range intervals of the selected PSL size parameter, and instrument 2 CMDs were closer to the selected PSL size parameter more often than the other instruments. This suggests that instrument 2 was more responsive than the other instruments to the selected size range and the selected PSL size parameters. Results from the regression plots demonstrated that the main effects and interaction were statistically significant with a p<0.01. The coefficient of determination, R2, for the regression lines was 0.44. The post-hoc Tukey HSD test identified a significant difference between the instrument 3 dataset and the instrument 1 dataset. Potential sources of variability include solution water background contamination, surfactants in the PSL solution, and agglomeration. The performance of all the scanning mobility particle sizers compared in these experiments was acceptable for research and field applications, but caution should be taken when comparing the measurements of SMPS, especially SMPS from different manufacturers.

Agriculture workers can be exposed to hazardous concentrations of airborne contaminants such as, particulate matter (PM), carbon dioxide (CO2), and volatile organic compounds (VOCs). Exposure to these contaminants has been associated with a high prevalence of acute and chronic respiratory symptoms: coughing, wheezing, shortness of breath, and phlegm, as well as a reduction in lung function. Commercial low-cost indoor air quality (IAQ) monitors have the ability to detect many of the contaminants commonly found in agriculture. Limited research has been conducted on the performance of low-cost monitors in different occupational settings. Therefore, the purpose of this study was to evaluate whether the Foobot (Airboxlab, San Francisco, CA, USA), a low-cost (IAQ) monitor, is sufficiently robust to operate in agricultural environments and provide useful and accurate information to farmers. Foobots were deployed at two sites, a tractor repair shop (“Shop”) for 43 days and a finishing room in a swine production building (“Barn”) for 40 days, where they monitored PM2.5, CO2, and VOCs. Reference direct-reading monitors to compare Foobot readings were collocated with the Foobots. Paired sample results were compared over 19 days at the shop and 21 days at the barn. At neither of the two sites did the Foobots meet the National Institute for Occupational Safety and Health (NIOSH) acceptable bias criterion of ± 10% when compared to the reference monitors. Linear regression results indicate that a strong linear relationship does not exist (R2< 0.66) between the Foobots and reference monitors. A significant difference (P< 0.031) was found between contaminant concentrations reported by each Foobot but the difference was not found to be substantial. The Foobot CO2 and VOC concentrations were highly correlated (R2=0.99). However, a strong linear relationship between the Foobot CO2 concentrations and the reference CO2 concentrations was not found at the shop (R2 = 0.02) or barn (R2 = 0.61). After 40 days in the barn, the Foobots were reporting that damage had occurred to the sensors and were no longer functioning. In addition, the PM sensors in the three Foobots in the barn were contaminated after the study. Therefore, it was concluded that the Foobots were unable to supply farmers with accurate information and were not durable enough for agricultural environments. Future research will investigate the use of other low-cost monitors in agriculture.

No description available.