Human health impacts of high altitude emissions

Abstract

Millions of deaths worldwide are attributed annually to exposure degraded surface air quality and UV-induced skin cancer. However, the focus has been on surface emissions, and the contribution of high altitude emissions to these issues is rarely examined. In this thesis, potential links are investigated between high altitude emissions and damages or benefits to human health via photochemical effects. Changes in population exposure to fine particulate matter, ozone and UV-B radiation resulting from current and future high altitude emissions are calculated, applying epidemiologically-derived impact functions to estimate resultant mortality and morbidity. A stratospheric extension is developed for the widely-used tropospheric model GEOS-Chem, which has been shown to accurately model tropospheric conditions and used in simulations of remote and urban pollution. This extended model, the GEOS-Chem UCX, can propagate a stratospheric perturbation through to a tropospheric impact, including shortwave UV fluxes, long-lived species, stratospheric water chemistry and high altitude aerosols. This model is employed to estimate the impacts of reversing 1 K of global warming using stratospheric sulfate aerosol injection. In total, it is projected that 85,000 additional premature mortalities would occur in 2040 due to particulate matter exposure, but that reduced ozone loading would prevent 64,000 mortalities worldwide. Aerosol injection also results in a 5.7% reduction in the global ozone column and a 3.0% increase in surface UV-B, which could cause 3,700 additional melanoma mortalities per year. By comparison, surface air quality and UV-B impacts due to aviation emissions are found to have resulted in 16,000 premature mortalities globally in 2006, of which 450 occurred in North America. Ozone exposure contributes 43% of this total. The increase in tropospheric ozone due to aviation emissions is found to have prevented 390 skin cancer mortalities in 2006. This thesis quantifies the photochemical mechanisms connecting future and proposed high altitude emissions schemes to human health impacts and provides an estimate of mortality and morbidity attributable to aviation and sulfate aerosol injection.