The Historical Drivers in the Human Health Burden from Exposure to Surface Ozone

Abstract: Tropospheric ozone is the third most important greenhouse gas within the atmosphere and the growth in its concentrations over the industrial period have contributed to the increase in global mean surface temperatures. In addition, ozone at ground-level is a major air pollutant, with elevated concentrations having detrimental long-term effects on human health via respiratory disease. In the troposphere the ozone budget is controlled by chemical production and loss, stratosphere-troposphere exchange of ozone and is removed by deposition at the surface. Ozone concentrations at the surface have increased throughout the 1850 to 2014 period, mainly due to increases in anthropogenic precursor emissions. This increase will have had a large impact on the health of the world population from long-term exposure to ozone concentrations. Here we use results from chemistry-climate models to quantify the impact on surface ozone concentrations and human health over the period 1850 to 2014 in different scenarios that were conducted as part of the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). Sensitivity scenarios were used to explore the impact from fixing different drivers of ozone formation at pre-industrial values. We estimate the change in the relative risk of the mortality burden from long-term exposure to ambient surface ozone concentrations in the different scenarios. We find that the global peak season surface ozone concentrations have increased by 40 to 60% from 1850 to 2014 in three different models, with present day values all being above the WHO air quality guideline value. A coincident increase occurs in the risk of mortality from respiratory disease due to the increase in the long-term exposure to surface ozone concentrations. The increase in surface ozone concentrations and mortality risk is largely driven by increases in anthropogenic NOx and global methane concentrations over the industrial period. Smaller influences on surface ozone concentrations occur from changes in other anthropogenic ozone precursor emissions, anthropogenic aerosols, transport from the stratosphere and historical climate change. These results show the importance of certain drivers in the human health risk from the long-term exposure to air pollution, which can be used to inform future policy directions. 

Biography: Steven joined the Met Office in January 2016 to work on aspects of air quality and climate. Prior to this Steven undertook his PhD at the University of Leeds, investigating the impact of changing anthropogenic emissions on European atmospheric aerosols and climate over the second half of the 20th Century. He has also obtained Masters of Research in environmental science from Lancaster University. Steven has also spent time within the environmental consultancy sector working on local air quality management and also other environmental science issues.