Particles smaller than 2.5 micrometres - roughly one-thirtieth of a human hair - are small enough to bypass the upper airways and settle in the alveoli. Once there, they trigger systemic inflammation whose downstream effects include cardiovascular disease, stroke and diabetes.
The numbers that matter
- WHO annual guideline (2021): 5 microgrammes/m3
- EU limit value: 25 microgrammes/m3 (under revision to 10 microgrammes/m3 by 2030)
- French annual average (2022, INSEE): 10-15 microgrammes/m3 in most urban areas, > 20 microgrammes/m3 in some hotspots
What long-term exposure does
A large European cohort (Lelieveld et al., 2019) attributed roughly 800,000 premature deaths a year on the continent to PM2.5 exposure, with cardiovascular endpoints dominating. The "life years lost" estimate is typically larger than that attributed to tobacco in the same cohorts, because air pollution affects everyone.
Sante publique France estimates 40,000 premature deaths per year in France are attributable to PM2.5, and reaching the WHO 2021 guideline would avoid ~18,000 of them annually. For comparison, road accidents cause roughly 3,500 deaths a year.
What we show on ClearSpot
Our air module combines two feeds:
- OpenAQ for real-time ground sensors (15-minute resolution, variable geographic coverage).
- Atmo France for regulatory indices (Indice ATMO, 1 km resolution).
A cell is "not clear" when PM2.5 exceeds 15 microgrammes/m3 (rolling 24 h average) or the Indice ATMO reaches 7 (on a 1-10 scale). Those thresholds are deliberately tighter than the legal EU values so that "CLEAR" on ClearSpot actually means "inside the WHO comfort zone", not "inside the legal tolerance".