Fine particle pollution thresholds: when is it time to worry?
Not a freezing winter or scorching summer goes by without a peak in fine particles. Though they are odourless and invisible, they still pollute the air we breathe and affect human health. When is it time to say enough is enough? When should we be implementing measures to protect ourselves?
December 1952. The Great Smog of London caused 12,000 deaths and allowed scientists to make a connection between pollution peaks and mortality. “This tragic event got things moving. In the years that followed, the scientific community began taking an interest in the issue and the first public policies to combat air pollution emerged”, explains Francelyne Marano, professor emeritus at Paris Cité university, and former president of the specialist commission on environmental risks on the Haut Conseil de la Santé Publique. Seventy years on, air quality objectives, thresholds and limits have all emerged, and our understanding of how fine particle pollution affects us has progressed.
WHO thresholds: quality objectives
On the basis of corroborated scientific and medical data, the World Health Organization (WHO) has established two thresholds for fine particles: a daily threshold of 25 micrograms per cubic metre (µg/m³) on average over 24 hours and an annual threshold of 10 µg/m³ on average over one year. “These thresholds, which are designed to limit long-term and short-term exposure to fine particles, are not legally binding for countries, but serve as benchmarks to guide decision-makers as they strive to reduce air pollution”, says Francelyne Marano. In 2021, the WHO revised its air quality standards for fine particle pollution (PM2.5 and PM10), cutting them to an annual average of 5 mg/m3 for PM2.5 and 15 µg/m3 for PM10. Why this change? There is growing scientific evidence of the health risks associated with concentration levels of PM2.5 and PM10 pollutants. “The thresholds have been revised mainly following studies linking pollution with cancer. And not only lung cancer, but breast cancer as well, for example,” points out Francelyne Marano.
Stop focusing on pollution peaks
“Epidemiological studies have shown that although the danger of pollution peaks should not be minimised, background pollution is the most significant factor in terms of morbidity and mortality”, states Francelyne Marano. Prolonged exposure to high levels of fine particle pollution – even when pollution does not reach peak levels – is associated with an increased risk of cardiovascular diseases, respiratory disorders, cancers, developmental issues in children, neurodegenerative diseases and premature death. According to the Energy Policy Institute at the university of Chicago, if WHO standards were permanently respected, global life expectancy could be increased by 2.3 years. So it is important to take both daily thresholds and prolonged exposure to fine particles into account when assessing the health risks caused by air pollution.
Ne pas se focaliser sur les pics de pollution
“Les études épidémiologiques ont démontré que, même s’il ne faut pas minimiser le danger des pics, la pollution de fond est le facteur le plus important en termes de morbidité et de mortalité”, affirme Francelyne Marano. Une exposition prolongée à des niveaux élevés de pollution aux particules fines -même en l’absence de pics de pollution – est associée à un risque accru de maladies cardiovasculaires, de pathologies respiratoires, de cancers, de problèmes de développement chez les enfants, de maladies neuro-dégénératives et de décès prématuré. Selon l’Institut de politique énergétique de l’université de Chicago, se conformer en permanence aux normes de l’OMS pourrait même accroître l’espérance de vie mondiale de 2,3 années. Il est donc important de prendre en compte à la fois les seuils journaliers et l’exposition prolongée aux particules fines lors de l’évaluation des risques pour la santé liés à la pollution de l’air.
Protéger les populations de la pollution aux particules fines, ce n’est donc pas prendre des mesures ponctuelles au moment des pics de pollution, mais bien conduire des politiques publiques pour réduire le niveau d’exposition tout au long de l’année. Autrement dit : encourager les mobilités douces, développer des zones à faibles émissions qui restreignent la circulation des véhicules polluants ou encore mener des campagnes de sensibilisation. C’est aussi une urgence pour les acteurs de l’industrie automobile qui ont un rôle à jouer, en concevant des véhicules propres limitant la pollution aux particules fines et donc les risques sanitaires pour les habitants des zones urbaines. Pour y parvenir, il faudra aller au-delà de la simple électrification. Désormais, à chacun de prendre ses responsabilités !
Comment se protéger de la pollution aux particules fines ?
- S’informer sur les niveaux de pollution près de chez soi.
- Vivre loin des axes routiers très fréquentés.
- Privilégier le vélo et les transports en commun pour ses déplacements. Ou a minima, équiper son véhicule de filtres à particules.
- Avoir une bonne hygiène de vie et consommer des aliments antioxydants (prunes, artichauts, framboises, etc.).
- Éviter de sortir et de pratiquer un sport lors des pics de pollution.
Related articles
Not a freezing winter or scorching summer goes by without a peak in fine particles. Though they are odourless and invisible, they still pollute the air we breathe and affect human health. When is it time to say enough is enough? When should we be implementing measures to protect ourselves?
When they are inhaled daily, brake wear particles can exacerbate pulmonary and respiratory diseases in the most vulnerable people. Scientists have also found other risks. We shed some light on this still relatively unknown danger.