In this paper, we study the environmental impact of the London Congestion Charge using a Synthetic Control approach applied to the concentrations of several pollutants linked with automobile use : PM10, NOx and Ozone. We proceeded in two steps : we first applied the SCM at the city scale, basing on the Urban Audit, and showed that the LCC decreased the number of days with PM10 and Ozone concentrations above the European standards. At the city scale, we can compare the composition of the pool of cities retained to construct the counterfactual. In a second step, we adopted the pollution station scale in order to treat more refined data on air pollution. This allowed us to distinguish between within, boundary and outside LCC zone stations. We showed that the introduction of the LCC and its extension has significant impacts on PM10 concentrations, and that the latter also had an impact on NOx concentrations; however no significant impact was found within the LCC zone. With this very preliminary results, we show that the LCC had a significant impact on air quality; however both the nature of the pollutant studied and the type and locations of the stations under scrutiny matters.