Researchers at the University of York have figured out why, in some growing economies, lowering particle pollution leads to an increase in surface ozone pollution, which has detrimental effects on human health, ecosystems, and agriculture.
The researchers claim that the findings, which were published in Nature Geoscience, cast doubt on tried-and-true strategies for combating air pollution.
The primary component of “smog,” surface ozone, is produced by chemical interactions between nitrogen oxides (NOx) and volatile organic molecules (VOC). When sunlight is present, pollutants released from factories, power plants, industrial boilers, refineries, and other sources react.
The scientific world was startled to see an increase in ozone pollution in the last ten years when countries like China improved air quality by reducing particle pollution, which is released through burning coal, making steel, driving, and fires.
The study has now provided fresh insight into the connection between these two contaminants. The researchers have demonstrated that in some places, ozone and particles are tightly related, despite the fact that historically, policymakers have treated them as different issues.
Peroxy radicals, which are short-lived ozone-making components, adhere to particle pollution and stop it from continuing to produce ozone. The peroxy radicals become available for reactions as the number of particles falls, and ozone production rises.
In some densely populated parts of China and India, the study’s model of the impacts of lowering particle pollution revealed that it might result in an increase in the ozone of 20–30%. This would have a very severe effect on ecosystems and crop productivity if left unmanaged.
New approaches that take into account this interaction between contaminants are being demanded by the researchers. Targeting reductions in a wider variety of pollutants, especially (VOCs) from chemicals and fuels and NOx from combustion, will help solve the issue.
This study shows that there can be risks in focusing too narrowly on just one pollutant. There has been a dramatic improvement in particle pollution in China over recent years, but emphasis only on particles can lead to unintended consequences. Action to accelerate the reduction in emissions of NOx and VOCs is now essential.
Professor Alastair Lewis
Co-lead author of the study, Professor Mathew Evans from the Department of Chemistry at the University of York said:
“Particle pollution and ozone pollution have been viewed by policymakers around the world as separate issues, but our study emphasizes the need to look at them together. For 40 years we have thought that ozone depended only on volatile organic compounds and nitrogen oxides and it’s only now that we are putting the pieces of the puzzle together and seeing this relationship with particle pollution. The policy now needs to be adapted to this new knowledge.”
“Tackling particulate matter in the atmosphere is rightly a priority because of the serious risk it poses to human health. However, this study highlights the complex choices facing governments in how they invest to manage air pollution. Solutions are not straightforward and there can be hidden connections between different pollutants.”
The WHO estimates that exposure to outdoor air pollution causes 4.2 million premature deaths each year. Developing nations like India, China, and Africa are among those most severely impacted.
According to the modelling study, considerable reductions in particle pollution in these areas would necessitate drastic cuts in NOx and VOC emissions of up to 50% in order to maintain a healthy level of ozone contamination.
Co-lead author of the study, Professor Alastair Lewis from the National Centre for Atmospheric Science added, “this study shows that there can be risks in focusing too narrowly on just one pollutant. There has been a dramatic improvement in particle pollution in China over recent years, but emphasis only on particles can lead to unintended consequences. Action to accelerate the reduction in emissions of NOx and VOCs is now essential.”
Published in Nature Geoscience is Suppression of Surface Ozone by an Aerosol-Inhibited Photochemical Ozone Regime. The National Centre for Atmospheric Science National Capability Awards, the Air Pollution and Human Health Programme (APHH), and the Natural Environment Research Council also contributed to the study’s funding.
