Inhalability and Personal Sampler Performance for Aerosols at Ultra-Low Windspeeds.

Inhalability is the efficiency with which people inhale airborne particles through the nose or mouth during breathing. Most previous studies used to set criteria for this were based on high-speed wind tunnels, using breathing mannequins to measure aspiration efficiency as a function of particle size. However, it has been shown that ultra-low windspeeds (between 0.05 and 0.5 m/s) are the most representative of modern workplaces. Bearing that in mind, studies performed in completely calm air have indicated that inhalability is greater in environments with essentially no air movements, casting doubt on the applicability of the current convention at ultra-low windspeeds as well. However, there is a lack of information for human inhalability at these windspeeds of interest. The hypothesis of this research was that inhalability at ultra-low windspeeds is more similar to calm air than fast moving air, on the basis that convective inertial forces will not completely overcome the effects of gravity, resulting in altered particle trajectories. In order to test this, entirely new facilities were necessary – including a heated, breathing mannequin and a novel wind tunnel that combined the principles and modes of operation of both conventional wind tunnels and calm air chambers. Flow visualizations were performed that indicated expired air was a potentially influential factor for air patterns around a breathing mannequin; body heat was not shown to be important. Experiments to directly assess inhalability – as well as the sampling efficiency of personal samplers commonly used to quantify such exposures – were carried out for particle sizes between 7 and 90 μm, at three different windspeeds covering the ultra-low range. Several different breathing patterns were also examined to assess the influence of breathing flowrate and mode (i.e., nose versus mouth). Results showed that aspiration efficiency, for both the mannequin and the personal samplers, was dependent on windspeed, with the greatest values at the lowest windspeed. At 0.10 m/s, inhalability was more similar to a proposed calm air criterion while exposures above 0.25 m/s were still described well by the current convention, indicating the need for dual criteria with which to define inhalability based on windspeed.Ph.D.Industrial HealthUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/63762/1/dsleeth_1.pd

Estimation of the Human Extrathoracic Deposition Fraction of Inhaled Particles Using a Polyurethane Foam Collection Substrate in an IOM Sampler

Extrathoracic deposition of inhaled particles (i.e., in the head and throat) is an important exposure route for many hazardous materials. Current best practices for exposure assessment of aerosols in the workplace involve particle size selective sampling methods based on particle penetration into the human respiratory tract (i.e., inhalable or respirable sampling). However, the International Organization for Standardization (ISO) has recently adopted particle deposition sampling conventions (ISO 13138), including conventions for extrathoracic (ET) deposition into the anterior nasal passage (ET1) and the posterior nasal and oral passages (ET2). For this study, polyurethane foam was used as a collection substrate inside an inhalable aerosol sampler to provide an estimate of extrathoracic particle deposition. Aerosols of fused aluminum oxide (five sizes, 4.9 µm–44.3 µm) were used as a test dust in a low speed (0.2 m/s) wind tunnel. Samplers were placed on a rotating mannequin inside the wind tunnel to simulate orientation-averaged personal sampling. Collection efficiency data for the foam insert matched well to the extrathoracic deposition convention for the particle sizes tested. The concept of using a foam insert to match a particle deposition sampling convention was explored in this study and shows promise for future use as a sampling device

The Thermodynamics of Indoor Air Pollution: A Pilot Study Emulating Traditional Kenyan Homesteads

This study examined the addition of natural ventilation (i.e., windows) in traditional Kenyan homesteads and other similar dwellings in developing countries. There is a particular need for the reduction of indoor air pollution in Kenya and other countries where traditional cooking relies on unrefined biomass fuels. For the purposes of this study, a cardboard tower equipped with thermocouples and an 80-watt heat source was constructed. As the recreation of smoke was deemed unfeasible, temperature differentials were measured within the tower and examined how varying temperature conditions might contribute to the accumulation of smoke indoors. Two scenarios were tested: windows-open and windows-closed. In the windows-open scenario, decreased temperature differentials were consistently observed throughout the sampling process with an average of 4.8 °C less than with the windows-closed (p = \u3c 0.0001). As existing research on smoke movement and temperature demonstrates, a decreased temperature differential will contribute to smoke stratification and an increased exposure to indoor air pollution. This study suggests that additional natural ventilation in isolation does not necessarily improve indoor air quality among households that use traditional cooking practices similar to Kenya’s. Rather, alternative interventions should be designed, including the placement of an exterior stove that is shielded from the elements but accessible to those indoors

Aerosol Measurement Degradation in Low-Cost Particle Sensors Using Laboratory Calibration and Field Validation

Increasing concern over air pollution has led to the development of low-cost sensors suitable for wide-scale deployment and use by citizen scientists. This project investigated the AirU low-cost particle sensor using two methods: (1) a comparison of pre- and post-deployment calibration equations for 24 devices following use in a field study, and (2) an in-home comparison between 3 AirUs and a reference instrument, the GRIMM 1.109. While differences (and therefore some sensor degradation) were found in the pre- and post-calibration equation comparison, absolute value changes were small and unlikely to affect the quality of results. Comparison tests found that while the AirU did tend to underestimate minimum and overestimate maximum concentrations of particulate matter, ~88% of results fell within ±1 μg/m3 of the GRIMM. While these tests confirm that low-cost sensors such as the AirU do experience some sensor degradation over multiple months of use, they remain a valuable tool for exposure assessment studies. Further work is needed to examine AirU performance in different environments for a comprehensive survey of capability, as well as to determine the source of sensor degradation

Laboratory evaluation of a low-cost, real-time, aerosol multi-sensor

<p>Exposure to occupational aerosols are a known hazard in many industry sectors and can be a risk factor for several respiratory diseases. In this study, a laboratory evaluation of low-cost aerosol sensors, the Dylos DC1700 and a modified Dylos known as the Utah Modified Dylos Sensor (UMDS), was performed to assess the sensors’ efficiency in sampling respirable and inhalable dust at high concentrations, which are most common in occupational settings. Dust concentrations were measured in a low-speed wind tunnel with 3 UMDSs, collocated with an aerosol spectrometer (Grimm 1.109) and gravimetric respirable and inhalable samplers. A total of 10 tests consisting of 5 different concentrations and 2 test aerosols, Arizona road dust and aluminum oxide, were conducted. For the Arizona road dust, total particle count was strongly related between the spectrometer and the UMDS with a coefficient of determination (R²) between 0.86–0.92. Particle count concentrations measured with the UMDS were converted to mass and also were related with gravimetrically collected inhalable and respirable dust. The UMDS small bin (i.e., all particles) compared to the inhalable sampler yielded an R² of 0.86–0.92, and the large bin subtracted from the small bin (i.e., only the smallest particles) compared to the respirable sampler yielded an R² of 0.93–0.997. Tests with the aluminum oxide demonstrated a substantially lower relationship across all comparisons. Furthermore, assessment of intra-instrument variability was consistent for all instruments, but inter-instrument variability indicated that each instrument requires its own calibration equation to yield accurate exposure estimates. Overall, it appears that the UMDS can be used as a low-cost tool to estimate respirable and inhalable concentrations found in many workplaces. Future studies will focus on deployment of a UMDS network in an occupational setting.</p