Decreasing trends in air pollution in the metropolitan area of Rome: an analysis of 15 years (1999-2013).

Urban air pollution is associated with a wide range of acute and chronic health effects. The objective of the present study was to examine trends (1999-2013) of air pollutant concentrations in the urban area of Rome and to assess the relationship between the concentrations of these pollutants. A statistically significant decreasing trend over time of NO2, PM10, benzene CO concentrations was observed. In particular, the most relevant decreases were found for benzene and for CO. Analysis of the correlation between pollutants showed that Pearson's correlation coefficients of pollutants were positive. Time trend analysis showed a significant improvement of air quality in Rome in the last years that may be attributable to improvements in car, truck and bus motor technologies and to the application of Green Infrastructure planning.