Researchers from the IRD, CNRS and UGA took part in a European study of the source of hazardous fine particulate matter, which was coordinated by the Paul Scherrer Institute (PSI, Switzerland). The results are published in the journal Natural on November 18, 2020, revealed the hazardous nature of atmospheric particulates due to their oxidative potential. They suggest that this indicator should be taken into account in future air quality regulatory measures to protect the health of populations worldwide.
Air pollution is responsible for several million premature deaths annually worldwide, and is one of the top five health risk factors, in addition to high blood pressure, smoking, diabetes and obesity. To overcome this phenomenon, measures to limit emissions are applied above a certain threshold for mass concentration of fine particulate matter suspended in air. In addition to these quantitative control measures, scientists are trying to understand what makes atmospheric particulate matter so dangerous.
Oxidative stress that increases inflammatory reactions
In this study, the researchers showed that the number of fine particles was not the only determinant of health risk. They examined the sources of air pollution in Europe, combining measurements of atmospheric chemical composition, toxicology and oxidative potential.
This indicator is used by scientists to estimate health-related exposures to air pollution,
Certain fine particulates produce oxidative stress in the lungs, which can cause damage to cells and tissues of the human body.“
Gaëlle Uzu, atmospheric biogeochemist at IRD and co-author of the study
First of all, researchers at PSI in Bern exposed cells from the human respiratory tract, known as bronchial epithelial cells, to samples of atmospheric particulate matter to test their biological response. At the same time, the Institute for Environmental Geosciences (IGE – CNRS / IRD / UGA / Grenoble INP) in Grenoble measured the oxidative potential for the same dose of particulate matter exposed to cells. The two teams were able to show that fine particles with an increased oxidative potential intensify the inflammatory response of cells, suggesting that the oxidative potential is an indicator of aerosol harm.
Health risks are increasing in major European cities
In a second step, the researchers collected various samples of atmospheric particulate matter in Switzerland. They analyzed the composition of this sample using a mass spectrometry technique developed at the Paul Scherrer Institute. “The chemical profile of each sample of material obtained in this way shows where it came from“, explains Kaspar Dällenbach, atmospheric chemist at PSI and lead author of the study.
At the same time, IGE carried out its oxidative potential measurements for all samples from five Swiss cities. Combining all of these measurements with advanced mathematical processing, it was possible to determine the oxidative potential of each emission source and use computer models to identify areas of the highest oxidative potential in Europe throughout the year. The similarity between the predicted values and the annual series of oxidative potential data previously measured at various French sites by IGE allows validation of the model outside of Switzerland.
The result: metropolitan areas, such as Paris and the Po River valley in northern Italy, are critical areas for air pollution. Not only are people in urban areas exposed to higher amounts of fine particulate matter, but the particulates in these areas are also more hazardous to health than aerosols in rural areas.
Aerosols of human origin are more oxidative
This study shows that although most fine particles are composed of inorganic (or “secondary”) minerals and aerosols, such as ammonium nitrate and ammonium sulfate used in agriculture, the oxidative potential of fine particulate matter is mainly due to organic (or “anthropogenic”)) aerosols from wood fires and metal emissions (especially those from brake and tire wear associated with road traffic).
Therefore, to reduce air pollution, the authors suggest that steps should be taken not only to regulate the number of fine particles, but also to take into account the various particulate sources and their oxidative potential.
“One of the main problems of this study is to predict health-related exposures to air pollution at the continental level, especially in the Global South where accelerated urban development will urgently require monitoring emissions to protect population health.“, said Gaëlle Uzu.