The thesis deals with the contamination of the workspace with a liquid aerosol, which is generated by scattering and evaporation of the cooling fluid. Cooling fluid are primarily intended to lubricate, cool and clean the tool and the workpiece, but the unwanted side effect is the formation of a liquid aerosol that holds in the air of the workspace. In such a contaminated work environment, the operator is exposed to a certain dose of a liquid aerosol that causes dermatological and respiratory problems. The topic of the thesis was to find out the number of particles of liquid aerosol that arises under varying working conditions and its dispersion in space. This amount was determined by image analysis using a high-speed camera.

<p>Aerosols are solid or liquid particles that span in size from a few nanometers to tens of micrometers. They are important in both outdoor and indoor environments due to their impact on climate and human health. Many aerosol processes of interest to the environment, health, and filtration are strongly size-dependent. Aerosol particle size distributions (PSDs) provide a basis to better understand outdoor and indoor air pollution sources, evaluate human exposure to air pollution, and aerosol deposition in the human respiratory tract and filters in building ventilation systems. Monitoring the temporal evolution of aerosol PSDs enable for characterization of dynamic aerosol transport and transformation processes, such as direct emissions, nucleation, condensation, coagulation, resuspension, deposition, and filtration. This thesis presents three studies on the PSDs of: (i.) urban aerosols in cities around the world in order to identify geographical trends in the shape and magnitude of PSDs and to frame future research needs for PSD observations at a global-scale, (ii.) synthesized salt particles from a novel thermal aerosol generator to evaluate its suitability for air filter testing, and (iii.) indoor biological particulate matter (<i>bio</i>PM) to characterize transient inhalation exposures of infants and adults to resuspended <i>bio</i>PM from carpet dust induced by crawling and walking.</p> <p>First, this thesis presents the current state-of-knowledge of urban aerosol PSDs by critically analyzing <i>n</i>=793 urban aerosol PSD observations made between 1998 to 2017 in <i>n</i>=125 cities in <i>n</i>=51 countries across the following regions of the world: Africa (AF), Central, South, and Southeast Asia (CSSA), East Asia (EA), Europe (EU), Latin America (LA), North America, Australia, and New Zealand (NAAN), and West Asia (WA). Prominent geographical variations in the shape and magnitude of urban aerosol number and mass PSDs were identified and significant variations in number PSDs were found between cities in EU and NAAN with those in CSSA and EA. Most PSD observations published in the literature are short-term, with only 14% providing data for longer than six months. There is a paucity of PSDs measured in AF, CSSA, LA, and WA, demonstrating the need for long-term aerosol measurements across wide size ranges in many cities around the globe. Inter-region variations in PSDs have important implications for population exposure, driving large differences in the urban aerosol inhaled deposited dose rate received in each region of the human respiratory system. Similarly, inter-region variations in the shape of PSDs impact the penetration of urban aerosols through filters in building ventilation systems, which serve as an important interface between the outdoor and indoor atmospheres. The results of this critical review demonstrate that global initiatives are urgently needed to develop infrastructure for routine and long-term monitoring of urban aerosol PSDs spanning the nucleation to coarse modes.</p> <p>Second, this thesis evaluates a newly designed commercially available thermal aerosol generator for ageing air filters in building heating, ventilation, and air-conditioning (HVAC) systems. The physical characteristics of the synthesized salt aerosol (NaCl and KCl) under different generator operational conditions were evaluated. The shape of the number and mass PSD output of the thermal aerosol generator are similar to those found in outdoor (urban) and indoor air and can be modulated by varying the rate at which the salt stick is fed into the flame. The morphology of the NaCl and KCl particles varied with size, with compact spherical or cubic structures observed below 100 nm and agglomerates observed above 100 nm. The thermal aerosol generator is a cost-effective technique for rapid ageing of HVAC filters with a PSD that more accurately represents, compared to conventional loading dusts, what filters encounter in real HVAC installations.</p> <p>Lastly, this thesis characterizes infant and adult inhalation exposures and respiratory tract deposited dose rates of resuspended <i>bio</i>PM from carpets. Chamber experiments were conducted with a robotic crawling infant and an adult performing a walking sequence. Breathing zone (BZ) size distributions of resuspended fluorescent biological aerosol particles (FBAPs), a <i>bio</i>PM proxy, were monitored in real-time. FBAP exposures were highly transient during periods of locomotion. Both crawling and walking delivered a significant number of resuspended FBAPs to the BZ, with concentrations ranging from 0.5-2 cm^-3. Infants and adults are primarily exposed to a unimodal FBAP size distribution between 2 and 6 μm, with infants receiving greater exposures to super-10 μm FBAPs. In just one minute of crawling or walking, 10²-10³ resuspended FBAPs can deposit in the respiratory tract, with an infant receiving much of their respiratory tract deposited dose in their lower airways. Per kg body mass, an infant will receive nearly four times greater respiratory tract deposited dose of resuspended FBAPs compared to an adult.</p>

<p>  </p> <p>Secondary organic aerosols (SOA) play an important role in the Earth’s radiative budget due to their potential to either warm or cool the atmosphere through light absorption or light scattering, respectively, and to cool or warm the lower atmosphere by acting as cloud condensation nuclei. SOA are air-suspended liquid and semi-solid droplets that form through multiphase chemical processes. Atmospheric photochemical oxidation of volatile organic compounds (VOCs) in the presence of air pollutants, such as NO_x (NO + NO₂) and the OH radical, promote formation of low volatility organic products that eventually condense to form SOA. To better understand the sources and sinks, formation, and fate of SOA, laboratory studies investigating oxidation of a biogenic VOC as well as anthropogenic emissions of SOA precursors were conducted. The first study (<em>Chapter 3</em>) investigated the OH-initiated oxidation of β-ocimene, a biogenic volatile organic compound (BVOC) released from vegetation, including forests, agricultural landscapes, and grasslands emitted during the daytime. The oxidation of BVOCs in the presence of NO_x leads to the formation of functionalized organic nitrate (RONO₂) compounds and isomers that easily condense to form SOA. To understand their atmospheric fate, the RONO₂ hydrolysis rate constants were quantified and found to be highly pH dependent. The findings of this study provide key insights into the formation and fate of organic nitrates and NO_x cycling in forested environments from daytime monoterpenes that were not previously included in atmospheric models. </p> <p>The second study (<em>Chapters 4 and 5</em>) investigated condensed waste emissions generated during Cured-In-Place-Pipe (CIPP) installations. This installation process is the most popular, least expensive, and most frequently used technology that cures leaking sanitary and stormwater sewers. Waste plumes discharged during pipe manufacture are complex multi-phase mixtures of volatile and semi-volatile organic compounds (VOC and SVOC, respectively), primary organic aerosols and SOA, fine debris of partially cured resin, and direct emission of nanoplastic particles that are all blown into the atmospheric environment at significant concentrations at worksites. This work unveiled a direct emission source of airborne nanoplastic particles as well as substantial concentrations of hazardous compounds and SOA precursors that were previously unrecognized. </p>