Ecorc’Air: A Citizen Science Project for the Biomonitoring of Vehicular Air Pollution in Paris, France

For several decades now, air pollution has been a key concern for experts, public authorities and city dwellers, who are the first to be affected. Airborne particulate matter (PM) is indeed well known to cause adverse health effects. However, urban air quality stations are too sparse to provide a detailed picture of the distribution of pollution. Since PM is also deposited on the surfaces of urban tree, tree bark can then act as an alternative passive trap. Its magnetic properties make it possible to measure the amount of metal particles deposited on them and to estimate the pollution caused by motorized traffic around the trees. Here we present the citizen science project Ecorc’Air, in which volunteers collect fragments of plane tree bark, which are then sent to laboratories and used for a range of analyses. Since its launch in 2016, the project has led to the production of annual maps showing detailed concentrations of metal particles in Paris with fine spatial resolution. The concentration of fine metal particles decreases as the distance between trees and the road increases, with parked cars potentially acting as barriers to protect pedestrians from PM. There is a growing interest and involvement of city dwellers, especially those involved in local associations, to act in favor of environmental research, a trend also observed in other European cities. Municipalities can also provide support by considering citizen science as an additional source of data for quantifying air quality and a means of communicating with their residents on environmental issues.