Environment: Increased risk of mortality in Rome and Milan due to high temperatures and pollution

By 2050 the mortality risk in Rome and Milan will respectively rise by 8% and 6% due to a combination of rising temperatures caused by climate change and the concentration of pollutants in the air, such as ozone and PM10. This is what emerges from a study by 11 ENEA researchers from four different laboratories[1] published by Science Direct.

“We selected Rome and Milan for our study due to their different population and climatic, socio-economic and pollution conditions. Rome has mild temperatures, low humidity and high ozone levels, while Milan, which is located in one of the most polluted areas in Europe, the Po Valley, is exposed to colder temperatures, has higher humidity and more moderate winds, along with high PM10 levels. These are all conditions that can have a significant impact on health and mortality risk. In fact, atmospheric particulate matter is recognised as a carcinogenic agent and is the leading environmental cause of mortality: according to the WHO, the number of deaths from air pollution has doubled from 1990 to 2019, reaching 4.5 million, 92% of which are due to atmospheric particulate matter and 8% to ozone”, explained Maurizio Gualtieri, researcher at ENEA's Atmospheric Pollution Laboratory.

According to the ENEA study, performed using the CRESCO supercomputer, in the coming decades the city of Rome could reach 591 deaths per year during the summer months (8% more than in previous decades) due to high temperatures and a concentration of tropospheric ozone (O₃) above the limit value for damage to human health (70 μg/m3). The photochemistry of the atmosphere could therefore play an important role in increasing summer mortality, as secondary tropospheric ozone peaks in the warmer months. In Lombardy's capital city, on the other hand, it is estimated that mortality will be higher during the winter (1,787 deaths out of a total of 1,977, or 90%) due to the colder climate, higher concentrations of PM10 (above the daily threshold of 50 μg/m³ set by the EU air quality directive) because of higher emissions from combustion and stagnant atmospheric conditions due to the geomorphology and location of Milan.

While global warming could create conditions that would seem beneficial locally, such as less severe winters and increased food production, overall the effects on a planetary scale are quite negative as they involve alterations to natural ecosystems, extreme weather events and impacts on human health such as those studied by ENEA researchers.

Exposure to high and low temperatures is one of the most worrying stress factors because it causes an increase in mortality, particularly among the most vulnerable, such as those older than 85, and in general leads to an array of health effects ranging from heat/cold stress, heat stroke and dehydration to the onset or worsening of respiratory and cardiovascular diseases. According to the study, in Rome in 2050 the number of deaths due to higher temperatures (mainly in summer) among the over 85s is estimated to reach 312 cases out of 1,398 annually (22%), while in Milan the total is equal to 971 cases attributable to lower temperatures (mainly in winter) out of 1,057 (92%).

To conduct this study, the ENEA team developed a calculation model integrating climate and air quality simulations (FARM) at a regional level with a spatial resolution of 20 km². This is a very high level of spatial detail that has made it possible to realistically assess mortality at the metropolitan area level in Italy through statistical models of environmental epidemiology used by ENEA researchers. For years the agency has boasted excellent expertise in climate change models, atmospheric pollutant dispersion and environmental epidemiology, and for some time now these three modelling tools have been used in increasing integration for the analysis and assessment of impacts on human health and ecosystems, as this study also demonstrates.

“We have thus obtained a better understanding of the combined effects of climate and air pollution on human health by 2050, using as references two IPCC scenarios that assume a global average temperature increase by 2100 ranging between 0.4 and 0.8°C in the most 'sustainable' scenario (RCP2.6) and 3.3 - 4.9°C in the least sustainable ‘business-as-usual’ scenario (RCP8.5)", explained Melania Michetti, ENEA researcher in the Models and Technologies for the Reduction of Anthropogenic Impacts and Natural Risks division.

“In addition to the improved spatial definition, we made a further advance with the analysis of delayed human health effects for each city and per exposure variable, i.e. temperature, ozone and particulate matter. A strength of the model was that it was possible to calculate up to how many days after the occurrence of a weather or pollution event the exposed population would suffer consequences. For both cities, the result is up to 20 days for temperature and up to 3 days for ozone and PM10.[2] This methodology, which is quite versatile and could be applied to all Italian cities for specific time horizons and future emission scenarios, can be extended to the assessment of other pollutants or temperature indicators”, Michetti concluded.

The results of the study therefore highlight the urgent need to adopt more strict and integrated policies on air quality and combating climate change, with the containment of the global average temperature increase to below 1.5°C by 2100, which would make it possible to reduce the number of deaths by 8 times in Rome and 1.4 times in Milan compared to the period 2004-2015,[3] without forgetting that the steady decline in the birth rate and the increase in longevity typical of western countries could favour a greater vulnerability of the Italian population to future environmental and climatic stressors.

For more information:

Melania Michetti, ENEA - Models and Technologies for the Reduction of Anthropogenic Impacts and Natural Risks division, 

Climate change and air pollution: Translating their interplay into present and future mortality risk for Rome and Milan municipalities - ScienceDirect

From single to multivariable exposure models to translate climatic and air pollution effects into mortality risk. A customized application to the city of Rome, Italy - ScienceDirect

[1] The ENEA laboratories involved in the study are: “Models and Technologies for the Reduction of Human Impacts and Natural Hazards”, “Climate Modelling and Impacts”, “Air Pollution” and “Health and Environment”.

[2] In detail, in Rome health effects persist for up to 15 days for temperature, up to 3 days for ozone and up to 2 days for PM10. In Milan, the result is up to 20 days for temperature and up to 2 days for ozone and PM10.

[3] From 2004 to 2015, the total number of deaths from natural causes was 299,493 in Rome and 155,734 in Milan, with annual averages of 24,958 and 12,978 respectively. Considering the resident populations (Rome 2,724,893; Milan 1,304,003), the historical mortality levels appear similar: on average each year about 1,000 people die from natural causes per 100,000 inhabitants in both Milan and Rome. In both cities, the current (historical) mortality burden is higher for cold temperatures (>80%) than for warm temperatures, and the over-85s are the population group most vulnerable to the combined effects of air pollution and climate change. The two cities show comparable annual average values for temperature (Rome 16.02°C; Milan 13.48°C) and O₃ (Rome 71.18 μg/m3; Milan 72.16 μg/m3), with the exception of PM10 (Rome 26.68 μg/m3; Milan 39.1