Investigation of parameters affecting the presence of airborne indoor particles and the resulting exposures
Creators: name: He, Ruikang
Publisher: name: No Publisher Supplied
Year: 2023

description: Adverse health effects caused by exposure to indoor airborne particulate matter (PM) drive the need to understand the behavior of indoor PM and be able to measure the presence of and exposure to indoor PM. The overall goal of this dissertation was to improve our understanding of factors affecting indoor particle concentrations and related human exposures. To achieve this goal, the work presented in this dissertation used various tools, including consumer-grade and professional-grade air quality monitors. Consumer-grade air quality monitors provide an easier and more affordable way to simultaneously measure particle concentrations in multiple locations, providing new capabilities to investigate PM. In contrast, professional-grade air quality monitors provide more accurate and robust particle concentration readings. The goal of the dissertation was accomplished through the following aims. Aim 1: Compare the performance of two consumer-grade monitors (Foobot and AirVisual Node) with a professional-grade instrument DustTrak DRX (TSI Inc.). The devices were compared in two laboratory environments and one residential apartment when measuring five types of aerosols (0.72 and 2.00 µm polystyrene latex (PSL) spheres, Arizona Road Dust (ARD), nanosilver-based surface cleaner, and particles created by a cooking event). The low-cost monitors were highly correlated with the DustTrak DRX for most aerosol types (r &gt; 0.78), except when measuring nanosilver spray, where the r value decreased to 0.55. AirVisual showed lower precision errors than Foobot for most types of aerosols. Both consumer monitors showed high accuracy and precision when measuring temperature and humidity compared to the professional-grade IAQ Meter (TSI Inc.). AirVisual showed high accuracy and precision when measuring CO2 compared to the IAQ meter, while Foobot didn't report accurate CO2 concentrations.Aim 2: Investigate the effect of heatwaves on indoor PM2.5 levels and analyze modifying factors. Heatwaves are known to result in negative health effects, and the increase in temperature and air pollution plays an important role in the increasing mortality and morbidity during heatwaves. However, the effect of high outdoor temperatures on indoor air quality is largely unknown. Thus, we hypothesized that heatwaves (i.e., high outdoor temperatures) increase indoor PM2.5 levels. Here, we examined the PM2.5 levels in apartments of the low-income elderly population using consumer-grade air quality monitors (AirVisual selected from Aim 1) from July to September 2017. We found that the average hourly indoor PM2.5 levels varied substantially among apartments, and apartments with smokers showed much higher indoor PM2.5 levels than apartments with non-smokers. Days with high temperatures (heatwave days) showed statistically significantly higher PM2.5 levels than non-heatwave days for both smokers’ and non-smokers’ apartments. During heatwave days, average hourly PM2.5 levels increased by 33.4 μg/m3 in smokers’ units and 5.0 μg/m3 in non-smokers’ units compared to non-heatwave days. Moreover, we separated the data into an active period (6:00 a.m. to 10:00 p.m.) and the rest period (10:00 p.m. to the next day 6:00 a.m.) and found that the PM2.5 during heatwaves was statistically significantly higher than during non-heatwave days for both periods.Aim 3: Quantify the resuspension of particles from the nanotechnology-based sprays and determine factors that affect the resuspension of such particles. The release, deposition, and resuspension of particles from nano-enabled consumer products are becoming an important indoor particle source. However, there was a lack of data on the resuspension of particles from such sprays. We hypothesized that settled particles from nanotechnology-based consumer sprays could be resuspended by human walking and that the resuspension could be affected by the spray type, flooring type, and resuspension force. To achieve this goal, we investigated particle concentrations during the spraying and resuspension of nanotechnology-based consumer sprays using professional-grade air quality monitors. We also examined the effect of product type, flooring material, and resuspension force on particle resuspension. The measured resuspension rates ranged from 10−4 to 5 × 10−1 h−1, depending on the product (seven products were investigated), flooring material (e.g., carpet and vinyl), and resuspension force (e.g., a walking adult and a moving child; the latter was simulated by a robotic sampler). The resuspension rate from the carpet was statistically significantly higher than that from vinyl flooring, while the resuspension rate caused by the adult was statistically significantly higher than that by the robot.Aim 4: Estimate personal exposures and area exposure of adults and children to the releases and resuspended particles from nano-enabled consumer sprays and estimate factors affecting the exposures. Indoor exposures are often estimated using stationary samplers; however, they might not accurately predict personal exposures. The latter should be measured using personal samplers. We hypothesized that personal exposures due to spraying and resuspension of nanotechnology-based consumer sprays differ from exposure estimates based on stationary samplers and that exposure of children to said particles is higher than that of adults. The investigated factors affecting exposures included the spray type, flooring material type, resuspension force, and measurement heights. A robotic sampler was used to simulate the movement of young children. The results showed that children could be exposed to higher particle mass concentrations than adults during spraying and resuspension of consumer sprays. The resuspension from the carpet led to higher exposure of both adults and children than resuspension from vinyl. Compared to particle resuspension by the robot, walking by an adult led to higher exposure to resuspended particles for adults and children.