Within the same geographic area, the highest levels are recorded in the immediate vicinity of the main roads. Indeed, along the roads, pollutants from road traffic add to the so-called “background” urban pollution that we breathe throughout the Paris metropolitan area.
The levels decrease very quickly away from the axis, particularly in the first 10 meters. The distance from the axis which is under the influence of traffic varies depending on the pollutants considered but it remains relatively restricted (200m max in an open area for nitrogen dioxide and 100 to 150m for particles and benzene). This decrease distance also depends on the topography of the axis and the presence or absence of urban developments (noise walls, landscaped embankments, buildings, etc.) which have a screening effect.
At a distance of 500 meters from the highway, the influence of the highway is generally no longer noticeable. This is even more true if there is equipment such as noise barriers. It is likely that the concentration is quite comparable in the two configurations.
It is also good to know that pollution levels vary depending on the floors. In direct proximity to a road, pollution levels are highest on the ground floor, and decrease as you go up to the upper floors. However, the decrease is not linear between the floors: the difference is significant between the RDC and 1er floor, then less and less important between 1er and 2nd floor, etc... with levels which become homogenous beyond a certain floor.
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You will find all the information relating to air quality by municipality in the broadcasts page or in the annual balance sheet page of our website.
You will find additional information about the exhibition in the documents: Pollution near traffic et What pollution throughout the day.