DOI: 10.25549/usctheses-c127-654664
title: Investigation of physico-chemical characteristics of size-segregated particulate matter in a metropolitan environment and their impact on air quality in southern California

description: Numerous epidemiological studies have associated the adverse respiratory and cardiovascular effects to atmospheric particulate matter (PM) exposure. There is ample literature providing evidence of adverse effects for all inhalable particle size ranges, however the biological mechanisms responsible for the toxicity of PM are still uncertain. Due to the lack of data about how different PM components act in a complex mixture, it is not possible to precisely quantify the contributions from the main sources and components to the effects on human health. Thus, PM in health impact assessments is usually regarded as a uniform pollutant, regardless of the contribution from different sources, and assuming the same effect on morality. This is probably not a correct assumption, but is a pragmatic compromise while waiting for sufficient knowledge that will allow the use of indicators other than particle mass. As a result linking the toxicity of PM with several of its chemical components has been the focus of considerable research over the past decade. The associations between health endpoints with the hundreds of potentially toxic chemical species and PM characteristics may be daunting and not cost efficient. Therefore it is desirable to focus on the casualty of the few critical chemical components that current science supports as potentially the most harmful to human health. Such information will allow for more effective regulatory control strategies, more targeted air quality standards, and as a result, reductions in population exposure to the most harmful types of airborne PM. ❧ The current particulate matter emission standards are based on PM mass only. However, the prevailing scientific opinion contends that PM mass is a surrogate measure of other physical and chemical properties of PM that are the actual causes of the observed health effects. In this study we focus on the PM components that are not currently regulated, while there is ample evidence that they can cause hazardous health outcomes. The effect of the new after-treatment technologies on the composition of the remaining organic compounds, including the semi-volatile organic carbon (SVOC) fraction, is studied. While the association of adverse health effects with SVOC compounds has been reasonably well documented, the exact mechanisms by which SVOC compounds inflict health effects remain largely unknown. Therefore a new technology is developed that makes it possible to conduct toxicity and inhalation exposure studies separately to PM and vapor phase SVOC to investigate the degree to which health effects attributable to these pollutants are affected by their phases. In addition, in regards of PM₁₀ standards, coarse PM emissions are usually from hard to control sources like windblown soil and dust, brake lining abrasion, tire wear and bioaerosols, therefore control of fine PM emissions is easier to achieve in order to meet PM₁₀ standards. Coarse and fine PM have substantially different sources and sinks, and as a result different chemical composition, which would lead to potentially different health outcomes. Moreover, the available CPM mass concentration data is much more limited compared to ambient PM₂.₅ mass concentration data and hence significantly less is quantitatively known about the characteristics of CPM. In order to study the physical, chemical and toxicological characteristics of CPM in Los Angeles Basin, 10 distinct measurement sites were employed to sample the CPM for an entire year, in order to provide a much needed database of coarse PM characteristics in the Los Angeles basin, providing the seasonal and spatial variations over a variety of urban and semi-rural areas during one year of sampling period.