New Database on Global Surface Ozone Levels Shows Regions Most Affected by Air Pollution

Published today in the scientific journal Elementa: Science of the Anthropocene, the results provide the most ambitious ground-level ozone assessment ever undertaken. The paper is one of a series of publications that are part of the larger, international Tropospheric Ozone Assessment Report (TOAR) initiative.

In the upper layer of the atmosphere, the ozone layer protects life on Earth from the sun’s ultraviolet radiation. Just above the Earth’s surface, however, in the troposphere, it is an air pollutant. Formed in chemical reactions between nitrogen oxides and volatile organic compounds emitted from cars, industry, and other sources, ozone at ground level can be harmful to human health. Possible adverse health effects include a reduction in lung function and a higher susceptibility to asthma and infections. Ozone also irritates the membranes of the eyes.

To assess the frequency of periods in which a given population is exposed to harmful ozone levels, the international group of researchers from 14 institutions led by the Universities of Leicester and Edinburgh has now quantified the occurrence of high ozone levels. With data from over 4,800 monitoring stations, the researchers were able to analyse all available global data in a uniform way for the first time. Previously, analyses of ozone trends left researchers unable to draw robust conclusions about regional trends in ozone pollution. The large number of sites now included in this more comprehensive dataset makes that possible.

The new research shows that “despite improvements in air pollution emissions in Europe and North America, ozone levels that are harmful to human health are still a cause for concern across the world and ozone is rising in East Asia,” explains Dr Zoё Fleming from the University of Leicester, an atmospheric chemist and one of the study’s lead authors.

As part of the study, the researchers identified potentially dangerous ozone levels in urban as well as non-urban areas around the globe, based on the data the TOAR team had compiled into a large open access database, which includes statistics and graphics. “The coolest thing about TOAR is that we’ve created this comprehensive, open access database with pre-calculated statistics and data quality controls, that the research community and others can use to better understand surface ozone,” says Erika von Schneidemesser, an atmospheric chemist from the Institute for Advanced Sustainability Studies (IASS) and co-author of the paper.

Air quality monitoring is crucial to quantifying current air pollution levels, evaluating the effectiveness of emissions controls, and informing the evolution of air pollution policy. Professor Ruth Doherty from the School of Geosciences at the University of Edinburgh says: “The ability to quantify for urban regions worldwide the changes in high and peak ozone levels over the last 15 years and longer is an exciting research development, that we hope will be useful to air quality managers to inform and evaluate strategies to protect human health from the adverse effects of ozone.”

However, there are still large regions of the world where such monitoring is sparse or non-existent. To effectively understand and tackle air pollution, expanded monitoring is critical, the scientists pointed out.

The new research was led by the Universities of Leicester and Edinburgh in partnership with twelve other institutions worldwide – the Institute for Advanced Sustainability Studies (IASS) and Forschungszentrum Jülich in Germany, the Universities of Colorado, North Carolina-Chapel Hill, and Maryland as well as A.S.L. and Associates in the U.S., the Stockholm Environment Institute in the UK, INERIS in France, the Chinese Academy of Meteorological Sciences and Chinese Academy of Sciences in China, the Norwegian Institute for Air Research (NILU) and the Norwegian Meteorological Institute in Norway, Chalmers University in Sweden, and the University of Witwatersrand in South Africa.

The TOAR project is headed by Dr Owen Cooper, from the Cooperative Institute for Research in Environmental Sciences, University of Colorado-Boulder, United States and supported by a large international team of volunteer experts. It is funded by the International Global Atmospheric Chemistry project (IGAC), the World Meteorological Organization (WMO), the National Oceanic and Atmospheric Administration (NOAA), and Forschungszentrum Jülich.

More information about the Tropospheric Ozone Assessment Report (TOAR) is available here.

A copy of the paper ‘Tropospheric Ozone Assessment Report: Present-day ozone distribution and trends relevant to human health’ published in Elementa: Science of the Anthropocene is available here (DOI: https://doi.org/10.1525/elementa.273)