Panel 1
Massimiliano BULTRINI, Simona BUSCEMI, Giorgio CATTANI, Alessandra GAETA, Federica NOBILE (Dipartimento di Epidemiologia del Servizio Sanitario Regionale-Regione Lazio ASL Roma 1), Maria Antonietta REATINI, Massimo STAFOGGIA (Dipartimento di Epidemiologia del Servizio Sanitario Regionale-Regione Lazio ASL Roma 1)
Estimates of the population-weighted annual average exposure (Population Weighted Exposure, PWE) to PM2.5 have been developed at the municipal level using an integrated approach combining measurements and statistical models. The data, covering the period 2016–2022, enable comparison of PWE across all municipalities and provide a comprehensive overview of average exposure at the national level.
In 2022, 100% of the population was exposed to levels exceeding the WHO guideline value of 5 µg/m³. The national average PWE was 14 µg/m³ (range: 6–25 µg/m³).
Between 2016 and 2022, the national average decreased from 15 µg/m³ in 2016 to 14 µg/m³ in 2022, representing a 7% reduction.
The most widely accepted health estimates attribute a significant portion of premature deaths and reductions in life expectancy to exposure to ambient air pollutants (WHO, 2016; EEA, 2022; WHO, 2021).
Assessing population exposure and its spatial and temporal variability in outdoor environments is a critical step for epidemiological studies examining the relationship between air pollution exposure and health outcomes (Caplin et al., 2019).
This indicator provides an estimate of the population-weighted annual average exposure (Population Weighted Exposure, PWE) to PM2.5 aggregated at the municipal level, allowing comparison across cities and providing a comprehensive overview of average exposure at the national scale. It reflects chronic population exposure and is useful for long-term health effect estimations.
Exposure values are compared with reference levels (guidelines and interim targets) recently updated by the World Health Organization (WHO, 2021).
To estimate the average population exposure to major airborne pollutants, assess exposure levels in comparison with WHO reference values, and evaluate temporal trends in exposure.
Legislative Decree No. 155 of 13 August 2010 and subsequent amendments, implementing Directive 2008/50/EC and Directive 2004/107/EC.
WHO (2021), Global Air Quality Guidelines. Particulate matter (PM10, PM2.5), ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide. Geneva, World Health Organization, 2021.
“A Clean Air Programme for Europe.” Brussels, 18 December 2013 COM (2013) 918 final.
“Europe that Protects: Clean Air for All.” Brussels, 17 May 2018 COM (2018) 330 final.
“Pathway to a Healthy Planet for All — EU Action Plan: Towards Zero Pollution for Air, Water, and Soil.” Brussels, 12 May 2021 COM (2021) 400 final.
In its revision of the Guidelines, WHO produced numerical risk estimates for a range of health effects associated with a 10 µg/m³ increase in the annual average concentration of various pollutants. WHO does not define a threshold below which no risk exists but identifies an annual average exposure lower bound for PM2.5 at 5 µg/m³, termed the “Air Quality Guideline level.” This level represents the lowest concentration at which increases in total mortality, cardiopulmonary mortality, and lung cancer mortality have been observed, with a 95% confidence interval.
WHO has also defined “interim targets,” higher reference levels to be progressively achieved through air quality improvement policies. The interim targets for PM2.5 proposed by WHO are 10 µg/m³ (IT 4), 15 µg/m³ (IT 3), 25 µg/m³ (IT 2), and 35 µg/m³ (IT 1).
EU clean air programs have established that the medium- to long-term goal is to align with WHO air quality guidelines, which are more stringent than the EU air quality directive standards and based on what is considered necessary to protect human health.
The EU Clean Air Package and the Zero Pollution Action Plan aim to reduce premature deaths attributable to air pollution by more than half by 2030 compared to 2005 levels.
Panel 2
Caplin A., Ghandehari M., Lim C., Glimcher P., Thurston G.(2019), Advancing environmental exposure assessment science to benefit society. Nature communication (2019) 10:1236. https://doi.org/10.1038/s41467-019-09155-4.
EEA (2022), Health Risk Assessment of Air Pollution and the Impact of the New WHO Guidelines. Eionet Report – ETC/ATNI 2022/10.
EUROSTAT (2022), Sustainable development in the European Union — Monitoring report on progress towards the SDGs in an EU context - 2022 edition. (DOI): 10.2785/313289.
Stafoggia M, Bellander T, Bucci S et al. Estimation of daily PM10 and PM2,5 concentrations in Italy, 2013-2015, using a spatiotemporal land-use random-forest model. Environ Int 2019;124:170-79.
Stafoggia M, Cattani G, Ancona C, Ranzi A. La valutazione dell’esposizione della popolazione italiana all’inquinamento atmosferico nel periodo 2016-2019 per lo studio della relazione tra inquinamento atmosferico e COVID-19. Epidemiol Prev. 2020 Sep-Dec;44(5-6 Suppl 2):161-168. Italian. doi: 10.19191/EP20.5-6.S2.115. PMID: 33412807.
WHO (2016), Ambient air pollution: A global assessment of exposure and burden of disease. Geneva, World Health Organization, 2016.
WHO (2021), Global Air Quality Guidelines. Particulate matter (PM10, PM2,5 ), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Geneva, World Health Organization, 2021.
The population considered is that distributed within the 2011 permanent census sections, which represent the most recent available territorial basis. The 2021 territorial bases are currently undergoing validation and will incorporate updates related to municipal demographics and territorial changes since the 2011 permanent census.
The indicator expresses an average population exposure value at the municipal level. It is known that within a single municipality there is variability in pollutant concentrations, with areas where levels may be higher than average or background values. However, assessment of exposure at local or microscale levels within individual municipalities is beyond the scope of this indicator. It should be noted, however, that within municipalities, areas with higher population density are weighted more heavily in the calculation of Population Weighted Exposure (PWE).
The exposure values obtained should not be directly compared with legal limit values; for compliance assessment, the highest value measured by individual monitoring stations must be used.
Applicazione di modelli ad alta risoluzione spazio-temporale, con l’uso di predittori spazio-temporali, dati satellitari, dati di monitoraggio della qualità dell’aria.
Data quality assessment
DEP: Dipartimento di Epidemiologia del SSR Regione Lazio - ASL RME ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale) ISTAT (Istituto Nazionale di Statistica) SNPA (Sistema Nazionale per la protezione dell’ambiente)
ISPRA - Database InfoARIA;
ISTAT - www.demo.istat.it
National
Regional
Provincial
Municipal (7,904/7,914)
2016-2022
Indicator assessment
The model uses daily average concentrations measured at monitoring stations distributed across the national territory as the response variable and a selection of spatial and temporal predictors as explanatory variables. Monitoring data are collected and archived by ISPRA in the InfoAria database, in accordance with Directive 2008/50/EC (and its national transposition, Legislative Decree No. 155/2010) and Commission Implementing Decision 2011/850/EU.
A machine learning model, specifically a random forest, was developed to relate the daily concentrations from monitoring stations to spatial predictors (population density, road network, land cover, altitude, artificial surfaces, etc.) and spatiotemporal predictors (dispersion models, meteorology) in order to estimate daily average PM2.5 levels per square kilometer across the Italian territory.
Using the daily concentrations estimated by the random forest model, the average annual exposure of the Italian population was calculated by weighting the pollutant concentration in each grid cell by the resident population within that cell.
The “national average concentration value” is calculated as the population-weighted mean of the estimated concentrations for each municipality, with weights proportional to the resident population.
Finally, the percentage distribution of the resident population exposed to different PM2.5 concentration ranges is estimated.
In 2022, 100% of the population was exposed to levels exceeding the WHO guideline value of 5 µg/m³; 87% was exposed to levels above Interim Target (IT) 4 (10 µg/m³); and 42% of the population was exposed to levels exceeding IT3 (15 µg/m³). In this latter case, the exposed population is primarily concentrated in the Po Valley area, affecting Lombardy, Veneto, Piedmont, and Emilia-Romagna (Figure 1 – Table 1). No municipality recorded Population Weighted Exposure (PWE) levels exceeding IT2 (25 µg/m³).
The national average PWE was 14 µg/m³ (range: 6–25 µg/m³) (Figure 2).
Over the seven years considered (2016–2022), there is an overall decreasing trend in Population Weighted Exposure (PWE) values, with the sole exception of 2017, when a higher average value of 16 µg/m³ was observed (Figure 2). The national average decreased from 15 µg/m³ in 2016 to 14 µg/m³ in 2022, representing a 7% reduction. However, the period analyzed is too short to reliably estimate a trend and its statistical significance, which typically becomes evident when analyzing data over a time horizon of 10 years or more.
From 2016 to 2022, 100% of the population continued to be exposed to PM2.5 concentrations exceeding the WHO guideline value. A decreasing trend is observed in the proportion of the population exposed to levels above Interim Target 3 (15 µg/m³), dropping from 52% to 42%. In all years considered, the PWE never exceeded Interim Target 1 (35 µg/m³), and in 2022 it also confirmed not exceeding Interim Target 2 (25 µg/m³), consistent with observations from the previous four years (2018–2021) (Figure 3).
Data
Figure 1: Population-weighted average exposure to PM₂.₅ at the municipal level (2022)
Analysis by ISPRA based on data from the Department of Epidemiology of the Regional Health Service of Lazio
Figure 2: Annual distribution of PWE values (municipal-level population-weighted average exposure to PM2.5)
Analysis by ISPRA based on data from the Department of Epidemiology of the Regional Health Service of Lazio
Figure 3: PM2.5 — Percentage of population exposed by exposure range and year
Analysis by ISPRA based on data from the Department of Epidemiology of the Regional Health Service of Lazio
The six PWE categories shown correspond to the WHO guideline value and the four interim targets.
Table 1 – PM2.5 Population-weighted exposure (PWE) by region
Analysis by ISPRA based on data from the Department of Epidemiology of the Regional Health Service of Lazio
PWE: population-weighted average exposure (Population Weighted Exposure)
The six PWE categories shown correspond to the WHO guideline value and the four interim targets.
The indicator aligns with those used at the European level by the European Environment Agency (EEA) and globally by the World Health Organization (WHO) to monitor exposure. Additionally, it forms the basis for exposure assessment in the development of health risk assessments and burden of disease estimates, consistent with the approaches of these two supranational organizations.
With reference to the United Nations Sustainable Development Goals (SDGs), the methodological approach is consistent with that used to calculate the indicator for monitoring progress toward Goal 11 (making cities and human settlements inclusive, safe, resilient, and sustainable), specifically target 11.6 (by 2030, substantially reduce the per capita environmental impact of cities, particularly regarding air quality and waste management).
From a methodological perspective, the exposure estimate also underpins one of the indicators used to monitor progress toward Goal 3 (ensure healthy lives and promote well-being for all at all ages), specifically target 3.9 (by 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water, and soil pollution and contamination).