Air quality is massively improving in Paris, where I live. But Paris is big, and I am only breathing right where I am. What is the situation on my street corner?

Without giving too much away, our apartment is on the fourth floor, next to a moderately busy Parisian street corner. There is a traffic light where cars and motorcycles stop and accelerate. People smoke outside the bar downstairs. One of the biggest parks in Paris is only five minutes away.

I have installed an air quality sensor outside the window that looks onto our street corner. It measures the atmospheric particulate matter concentration. Here’s the data:

The WHO recommends the PM 2.5 concentration not to exceed 15 μg/m³ over a 24 hour window. The threshold for the yearly average concentration is set to 5 μg/m³. Current EU regulations are less stringent, setting the annual average to 20 μg/m³. At the time of writing this post each Parisian is exposed to roughly twice to three times the limit recommended by the WHO, but staying below the one recommended by the EU. This difference alone can push the mortality of a population up or down by a few percentage points.

The data in this plot updates every day. The sensor I am using (Plantower PMS7003) is not bad: it claims to have a counting efficiency of 98% for particles larger than 0.5 μm. Still, take my data with a grain of salt. Probably the pros have more sophisticated sensors, and also calibrate their equipment. That being said, the concentrations I measure are qualitatively in line with those provided by the NGO Airparif, which monitors the air quality in the greater Paris region.