Improving air quality and health in Northern Italy: limits and perspectives

A better air quality has led to a significant reduction of premature deaths over the past decade in Europe, as emissions of many pollutants declined considerably in the EU-27 Member States: SOx emissions by 76%, NOx by 42%, NMVOCs by 29% and PM2.5 by 29%. The present paper reports an in-depth analysis of the reasons why the regions of the Po valley, Northern Italy, still have difficulties to comply with EU air quality standards, in particular for PM10 and NO2, in spite of strong emission reductions carried out through careful Air Quality Plans put in practice during the last 2 decades. The analysis includes a consistent comparison of emission inventories for different European regions in Italy, Germany and Poland, the measured air quality trends and PM source apportionment in these areas, and, most of all, a thorough investigation of meteorological parameters influencing atmospheric pollutant dispersion and transport. The study reports that in the colder seasons, wind speed, PBL height and atmospheric pressure occurring in the Po basin are three to five times less efficient in diluting and dispersing pollutant if compared to regions north of the Alps. Due to the extremely disadvantageous orographic and climatic configuration of the Po Valley, only radical emission reductions could bring air quality into EU limit values with a questionable cost-benefit ratio of due policies. Provided that air quality standards (particularly for PM10 and PM2.5) aim at protecting people from adverse health effects arising from air pollution, it is however necessary to also consider the toxicity of atmospheric particulate in addition to PM10/PM2.5 mass concentration as a limit value. Based on existing toxicological studies and reports, a discussion is reported about PM toxicity factor depending on toxicity scores for source-specific aerosols and PM composition determined by Source Apportionment. Provided that PM components profiles are strongly different across Europe, the obtained PM toxicity factors range from 0.3 (for areas where the main PM contribution is referable to sea salts or inorganic matter) to 3.5 (where Elemental and Organic Carbon prevail), suggesting that, even at the same mass concentration, the effects of PM10/2.5 on human health are significantly variable and limit values should take into account differential toxicity. Modern PM Source Apportionment techniques, along with reliable toxicity and epidemiological analyses, represent the right tools to overcome the shortcomings of the current regulation standard and build a new consistent health metric for ambient PM in the future, helping policy makers impose effective air quality measures to protect people health.