Air pollution in Venice and in its mainland: a first assessment of air quality control policies

This article provides, for the first time, direct information on the levels and trends of nitrogen oxides and particulate matter measured by a recently installed air-quality monitoring station in the city of Venice (Italy). High levels of air pollution affect human health and built cultural heritage with corrosion, loss of material due to chemical attack, and soiling: this is particularly dangerous in a World Heritage city like Venice. The pollution levels measured in the historical city are compared to those of a background station in the city of Venice and of urban and background stations in the mainland, also investigating climate factors which might affect pollution in all stations. The first results of the investigation are that the NO₂, as well as the PM₁₀, annual average levels in Venice definitely exceeded the limit values set by EU directives. This is an astonishing and unexpected result in a car free city. To contrast the poor air quality, the Venice Municipality decreed in spring 2019 to limit traffic in one of the most overcrowded Venice canals. To investigate the usefulness of the implemented policy we performed a comparative study in which Generalized Additive Models are employed to model the potential reduction in measured nitrogen dioxide in the urban station as compared to the background station. This is done for stations in the historical city of Venice and in the mainland, to give a stronger indication of whether detected changes can be attributable to the traffic policy and no other exogenous factors. The policy is found to have a minor impact in the reduction of measured nitrogen dioxide.