Estimated number of deaths attributable to NO2, PM10, and PM2.5 pollution in the Municipality of Milan in 2019.

Background: there is growing evidence that exposure to environmental pollutants affects health, including mortality, chronic diseases, and acute diseases. The World Health Organisation has recently revised downwards the safety thresholds for exposure to environmental pollutants. The City of Milan (CoM) has particularly high levels of pollution; this is due both to the presence of various emission sources and to climatic and orographic conditions.

Objectives: to describe the health effects of exposure to pollutants, measured by deaths due to environmental exposure to NO2, PM10, and PM2.5 in 2019.

Design: observational study. Using a pollutant concentration estimation model, annual mean values of NO2, PM10, and PM2.5 were estimated for the CoM in 2019. The number of deaths attributable to each exposure was estimated using risk functions available in the literature; the values recommended by the new World Health Organisation guidelines were used as counterfactual exposure limits.

Setting and participants: the population assisted by the Agency for Health Protection of Milan and resident in the CoM on 01.01.2019, aged 30 years or older. The place of residence was georeferenced and the population was followed up until 31.12.2019. Deaths and their causes were obtained from the Causes of Death Registry.

Main outcome measures: deaths attributable to exposure from non-accidental causes, cardiovascular diseases, respiratory diseases, and lung cancer were estimated.

Results: in 2019, the estimated annual average level of NO2 was 36.6 µg/m3, that of PM10 was 24.9 µg/m3, and that of PM2.5 was 22.4 µg/m3, with levels varying across the city area. Concerning exposure to NO2, in 2019 10% of deaths for natural causes were estimated to be attributable to annual mean levels of NO2 above 10 µg/m3. As regard PM2.5, 13% of deaths for natural causes and 18% of deaths from lung cancer were attributable to an annual mean level above 5 µg/m3. The impact of exposure to particulate matter on mortality does not seem to be the same in all the areas of the CoM.

Conclusions: the health impact of exposure to airborne particulate matter in the CoM population is high. It is important that citizens, policy-makers, and stakeholders address this issue, because of its impact on both health and healthcare costs.