Title: Source Attribution of Societal Impacts of PM2.5 Pollution from Regional to Hemispheric Scales
Abstract: Chronic exposure to ambient PM2.5 concentrations is one of the leading worldwide mortality risk factor, which has seen an increase over the last decade. Sensitivity analysis is an essential approach in attributing societal impacts to emissions sources in any geographic scale. Source attribution of the societal impacts of PM2.5 pollution offers great potential for informing policy development and implementations. This thesis employs adjoint sensitivity analysis, integrating demographic, epidemiological, and economic data, in a full-complexity approach to link the sources of emissions to societal impacts. This study uses the adjoint of U.S. EPA’s Community Multiscale Air Quality (CMAQ) model (CMAQ-ADJ) to provide location-specific source attribution of the societal burden of PM2.5 pollution. CMAQ-ADJ model is extended from the regional to the hemispheric platform, including boundary transport of the societal impacts and updates to the chemical representation. The monetized health impacts of coal phase-out regulation in Ontario were retrospectively assessed, as well as those for planned phase-out across Canada. We also evaluate the transboundary impact of US coal-fired electricity generation and its emission control measures over the same period, and find the benefits from U.S. emission reductions to be larger than those from Ontario coal phase-out. Using hemispheric CMAQ-ADJ, location-specific premature avoided deaths and monetized health impacts are attributed to the emissions over Northern Hemisphere. Further exploring country-level inequalities in PM2.5 exposure, we employed hemispheric CMAQ adjoint to quantify inter-national air pollution health inequalities. A single SES parameter (country-level income) is used to estimate location-specific health inequalities for countries. As expected, low-income countries with high levels of PM2.5 concentrations indicated larger inequality sensitivities (e.g., India). However, the results demonstrate that air pollution health inequality could be integrated as a secondary health endpoint in air quality policies. The findings of this study indicate that considerable spatial and temporal variability is observed in sensitivities of primary and precursor PM2.5 emissions. Adjoint sensitivity analysis, specifically, is compatible with resolving the spatial variability of these sensitivities. Such location-specific and sector-specific source impacts can be useful to draw a roadmap to establish emission control strategies and to provide policy priorities for regional and global emission reduction efforts.