Scientists at the University of Yorkâ€™s Stockholm Environment Institute have claimed that long-term exposure to ozone air pollution is linked to 1 million premature deaths per year due to respiratory diseases.
The conclusion has been drawn from a study of results of a US analysis of the association of long-term ozone exposure and respiratory mortality in 670,000 adults, published in the journal Environmental Health Perspectives.
Conducted in 2010, the study suggests that air pollution contributed to around 1 million premature respiratory deaths globally â€“ approximately one in five of all respiratory deaths.
This is a substantially larger number of study participants and observed deaths than a previous estimate from 2003, on which previous global ozone health impact calculations have been based, researchers claimed.
Ozone is formed in the atmosphere from emissions of pollutants such as nitrogen oxides from vehicles, organic compounds from solvent use, and methane from agriculture.
Once formed, ozone can stay in the atmosphere for weeks and travel long distances from emission sources, across countries and continents.
Studies have linked exposure to ground-level ozone to conditions such as lung inflammation, decreased lung function and an increase in asthma attacks.
According to the researchers, the study suggested that the largest number of ozone-attributable respiratory deaths annually is in Asia, accounting for around 79% of the total 1 million global estimated deaths.
India accounted for around 400,000, and China for 270,000. Africa, Europe and North America each had between 50,000 and 60,000 ozone-attributable deaths, with fewer in Latin America and Oceania.
Chris Malley, Researcher at the University of Yorkâ€™s Stockholm Environment Institute and lead author of the study, said: â€œThis study highlights that exposure to ozone may make a substantially greater contribution to the global burden of disease than previously thought.
â€œThere is a degree of uncertainty in these estimates because the concentration-response function we used is based on analysis from the United States. We donâ€™t know whether the relationship is the same in other regions, such as in India and China, where the prevalence of other risk factors for respiratory diseases varies considerably.
â€œWe also estimated peopleâ€™s ozone exposure using a global atmospheric chemistry transport model, which means that we could not account for differences in ozone exposure at small geographic scales.â€
SEIâ€™s Policy Director Johan CI Kuylenstierna, co-author of the study, said: â€œOur colleagues from countries such as Ghana, Peru, Nigeria and Bangladesh have highlighted the importance of air pollution impacts on health as a motivation for reducing emissions.
â€œThe key in reducing ozone exposure lies in addressing the sources of pollution, given that many people, particularly in the poorest and most vulnerable populations, cannot easily relocate.
â€œTo reduce ozone pollution, you need to control emissions of different precursors from many different sources. This includes emissions from road transport, household energy use, as well as methane emissions from agriculture.
â€œDue to the long-range transport of ozone, it is important to realise that action is needed on local, national, regional and global scales. That means that regional cooperation is needed to solve the problem.â€