Air pollution : a new indicator to measure health impact

IRD Press Release - November 18, 2020

Researchers from IRD, CNRS and UGA participated in a European study on sources of fine particles harmful to health, coordinated by the Paul Scherrer Institute (PSI, Switzerland). Their results, published in the journal Nature on November 18, 2020, reveal the harmful nature of fine particles in the atmosphere through their oxidizing potential. They suggest that this indicator should be taken into account in the future in air quality control measures for the health of people around the world.

Air pollution is responsible for several million premature deaths worldwide each year and is one of the five major health risk factors, alongside high blood pressure, smoking, diabetes and obesity. To combat this phenomenon, measures to restrict emissions are taken above a certain mass concentration threshold of fine particles present in the air. To complement these quantitative control measures, scientists are seeking to understand what makes airborne particles so dangerous.

Oxidative stress that intensifies the inflammatory reaction

In this study, the researchers pointed out that the amount of fine dust is not the only decisive factor when it comes to health risks. They looked at the sources responsible for air pollution in Europe, and combined measurements of atmospheric chemistry, toxicology and oxidative potential.
This indicator is used by scientists to estimate health exposure to air pollution : "certain fine particles generate oxidative stress in the lungs, which can lead to damage to cells and tissues of the human body," explains Gaëlle Uzu, an atmospheric biogeochemist at the IRD, co-author of the study.

As a first step, researchers at PSI in Bern exposed human respiratory tract cells, called bronchial epithelial cells, to samples of atmospheric particles to test their biological response [[When cells are subjected to stress, they emit a signal substance for the immune system, which triggers inflammatory reactions in the body] . In parallel, the Institute for Environmental Geosciences (IGE - CNRS/IRD/UGA/Grenoble INP) in Grenoble measured the oxidizing potential for the same doses of particles exposed to the cells. The two teams were able to show that fine particles with increased oxidizing potential intensify the inflammatory response of cells, suggesting that oxidizing potential is an indicator of the harmfulness of aerosols.

An increased health risk in European metropolises

In a second step, the researchers collected various samples of atmospheric particles in Switzerland. Using a mass spectrometry technique developed at the Paul Scherrer Institute, they analyzed their composition. "The chemical profile of each sample of material obtained in this way indicates the source from which it came," says Kaspar Dällenbach, an atmospheric chemist at PSI and the first author of the study.

At the same time, the IGE carried out measurements of their oxidizing potential on all the samples from five Swiss cities. By combining all these measurements with advanced mathematical processing, it was possible to determine the oxidizing potential of all emission sources and to use a computer model to identify the areas with the highest oxidizing potential throughout the year in Europe. The model could be validated beyond the Swiss territory thanks to the concordance between the predicted values and the annual series of oxidizing potential data already measured on different French sites by the IGE.

As a result, metropolitan areas, such as Paris or the Po river valley in northern Italy, are critical regions in terms of air pollution. Not only are people in urban areas exposed to more fine particles, but particles from these areas are more harmful to health than aerosols from rural areas.

Human-made aerosols more oxidizing

This study shows that while most fine dust is made up of minerals and inorganic aerosols (known as secondary) such as ammonium nitrate and ammonium sulphate used in agriculture, the oxidising potential of fine particles is mainly due to organic aerosols (known as anthropogenic), which come from wood fires, or metal emissions (linked to wear and tear of brakes and tires in road traffic in particular).

Thus, in order to reduce air pollution, the authors suggest that it is necessary not only to act on the regulation of the quantity of fine dust, but also to take into account the different sources of particles and their oxidizing potential.

"One of the challenges of this research is the prediction of health exposure to air pollution on a continental scale, particularly in southern countries where the acceleration of urbanization will very soon make it necessary to control emissions in order to preserve the health of populations", underlines Gaëlle Uzu.

Local Scientific Contact

Gaëlle Uzu, atmospheric biogeochemist at the IRD, within the Institut des Géosciences de l’Environnement (IGE - CNRS/IRD/Grenoble INP/UGA), a laboratory member of the Observatoire des Sciences de l’Univers de Grenoble / gaelle.uzu ird.fr.

References

K. R. Daellenbach, G. Uzu, J. Jiang, L.-E. Cassagnes, Z. Leni, A. Vlachou, G. Stefenelli, F. Canonaco, S. Weber, A. Segers, J. J. Kuenen, M. Schaap, O. Favez, A. Albinet, S. Aksoyoglu, J. Dommen, U. Baltensperger, M. Geiser, I. El Haddad, J.- L. Jaffrezo, A. S. H. Prévôt, Sources and chemistry of the harmful components in particulate air pollution, Nature, 18 November 2020. DOI : 10.1038/s41586-020-2902-8

Z. Leni, L.-E. Cassagnes, K.R. Daellenbach, I. El Haddad, A. Vlachou, G. Uzu, A.S.H. Prévôt, J.-L. Jaffrezo, N. Baumlin, M. Salathe, U. Baltensperger, J. Dommen, M. Geiser. Oxidative stress-induced inflammation in susceptible airways by anthropogenic aerosol->https://doi.org/10.1371/journal.pone.0233425]. PLOS ONE, 18. November, 2020. DOI :10.1371/journal.pone.0233425

This press release was published by the IRD.