Air pollution is the largest environmental cause of death. Now, a study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, has estimated which sources contribute most to the mortality associated with two air pollutants - PM2.5 and NO2 - in 857 European cities.
The results of this research, which have been published in The Lancet Public Health, show great variability between the different cities studied, suggesting that, given that each one has its own particularities and its own sources of air pollution, strategies to improve air quality should be adapted to each local context.
Contributors to PM2.5 mortality
Pooling the data for the 857 cities, the figures show that the largest contributor to PM2.5 mortality is emissions from residential sources, with an average contribution across all cities of 22.7%. In second place is the agricultural sector, which accounts on average for 18% of PM2.5 mortality, followed by industry (13.8%), transport (13.5%), the energy sector (10%), natural sources (8.8%) and shipping (5.5%).
Contribution to PM2,5-related mortality
Mean contribution (857 cities)
Total estimated deaths
Residential
22.7%
48,433
Agriculture
18%
33,780
Industry
13.8%
29,977
Transport
13.5%
26,679
Energy
10%
19,424
Natural sources
8.8%
15,339
Shipping
5.5%
10,116
Other sources
3.4%
9,429
Aviation
0.4%
1,000
"If we look at NO2 and PM2.5 combined, traffic remains the largest contributor to both poor air quality and associated mortality. However, if we look exclusively at the PM2.5-related mortality, we see a significant contribution from the residential sector and agriculture," notes Sasha Khomenko, ISGlobal researcher and first author of the study.
"Although we have not broken down the specific sources of emissions for each sector in our study, we do know from the scientific literature that most of the particulate matter generated at the household level is mainly due to biomass and coal burning for heating and, to a lesser extent, fossil fuel-based systems for heat and hot water generation and gas cookers," Khomenko explains. "We know that rising fossil fuel prices and climate change mitigation policies have led to an increase in biofuel use. However, the fact that they are products of natural origin does not mean that they are not harmful to health," she adds.
"As far as agriculture is concerned, intensive livestock farming is known to be a major source of particulate matter, which is generated mainly from ammonia in animal slurry and also through the use of certain fertilisers. It is a source of pollution that spreads from its place of origin and moves to nearby cities", she says.
PM2.5 particles are the air pollutant with the greatest negative impact on mortality in European cities. The team stresses that more research is needed to determine which components of PM2.5 particles are most harmful to health, so that more precise mitigation measures can be designed.
Contributors to NO2 mortality
In terms of NO2 mortality, there is one very prominent contributor, which is the transport sector, with an average contribution across all cities of 48.5%. Other sectors with a considerable contribution are industry with an average of 15%, the energy sector with 14.7%, housing (10.3%) and shipping (9.7%).
Contribution to NO2-related mortality
Mean contribution (857 cities)
Total estimated deaths
Transport
48.5%
43,540
Industry
15%
13,073
Energy
14.7%
14,111
Residential
10.3%
11,105
Shipping
9.7%
9,020
Aviation
1.4%
1,991
Other sources
0.4%
396
Agriculture
0%
18
NO2 is a gas that is generated in combustion processes, mainly from motor vehicles, but also in industrial or power generation facilities.
"Bolder measures are required to drastically reduce pollution and deaths associated with traffic, which remains the main source of emissions. And, at the same time, implement policies to mitigate the other sources of both NO2 and PM2.5 emissions, such as regulating emissions from industry and shipping, and limiting biomass burning in households and emissions from agriculture and livestock", says Mark Nieuwenhuijsen, director of ISGlobal's Urban Planning, Environment and Health Initiative.
“To reduce air pollution we need multisectoral holistic action and solutions, for example with task forces across the current silos (e.g. urban planning, transport engineering, housing, environment, health, education, agriculture, business) at city, national and EU levels”, Nieuwenhuijsen adds.
Methodology
The study focused on 857 European cities that appear in the Urban Audit 2018 dataset. Baseline NO2 and PM2.5 emissions data, relating to 2015, were obtained from the regional Copernicus Atmosphere Monitoring Service inventory and classified into 12 sectors using a standard nomenclature system (GNFR). In addition, population and mortality figures for the 857 cities were obtained from public databases, also for the year 2015.
To estimate the contribution of each emission source to the concentration of pollutants in the atmosphere, the researchers used the Screening for High Emission Reduction Potentials for Air quality (SHERPA) tool developed by the European Comission’s Joint Research Centre (JRC). This tool applies the principles of chemical transport models in a simplified way. These models take into account factors such as meteorology or chemical transformations to simulate the concentration of pollutants in the atmosphere. The research team divided the surface area of the European cities studied into 36 km2 grids. Using SHERPA, they estimated the changes in atmospheric concentrations of PM2.5 and NO2 that would occur if emissions were reduced in each of the grids on the map and calculated the relative contribution of each of the pollution sources.
Finally, a comparative risk assessment was carried out to estimate the mortality that could be prevented under different scenarios of reduced pollutant concentrations associated with each of the emission sources.
It should be noted that, due to the spatial resolution of the study, estimates made for smaller cities may be less precise than those for larger cities.
Data of the 857 cities
The different source contribution to NO2 and PM2.5 associated mortality are available on this embargoed version of the ISGlobal Ranking website (please, note that when the embargo lifts all data will be transferred to isglobalranking.org)
Examples of European cities
Contributors to NO2-related mortality (%)
City
Transport
Industry
Energy
Residential
Agriculture
Shipping
Aviation
Other
Amsterdam
35.03
8.70
7.86
8.22
0.00
31.61
7.47
1.10
Barcelona
47.96
14.97
6.59
11.50
0.00
16.47
2.33
0.19
Berlin
36.24
10.66
33.85
12.91
0.00
1.39
4.70
0.26
Brussels
62.07
7.65
6.58
15.08
0.00
5.68
2.69
0.25
Bucarest
50.10
6.82
28.57
13.68
0.04
0.45
0.21
0.13
Lisbon
28.56
26.79
2.33
4.03
0.01
22.03
16.13
0.12
London
59.55
7.39
8.93
16.08
0.00
3.50
4.12
0.43
Madrid
71.04
7.35
2.27
13.46
0.01
0.40
5.32
0.15
Paris
45.91
4.10
11.46
31.86
0.00
1.21
4.52
0.94
Prague
46.70
12.06
15.50
22.64
0.01
0.41
1.86
0.84
Rome
56.21
5.61
1.48
28.07
0.01
3.71
4.59
0.32
Stockholm
51.71
3.03
17.64
4.57
0.00
21.08
1.18
0.79
Warsaw
30.97
4.00
46.88
15.28
0.02
0.41
1.96
0.47
Contributors to PM2.5-related mortality (%)
City
Transport
Industry
Energy
Residential
Agriculture
Shipping
Aviation
Natural sources
Other
External
Amsterdam
15.35
14.03
6.55
13.72
21.18
12.87
1.95
4.45
8.03
1.87
Barcelona
12.97
16.46
3.96
26.77
11.78
11.86
0.55
6.35
5.22
4.08
Berlin
13.51
13.63
17.30
15.02
24.73
1.14
0.92
2.90
5.89
4.95
Brussels
20.51
15.18
5.06
23.01
21.74
4.81
0.67
3.54
4.74
0.73
Bucarest
10.06
17.42
13.42
35.77
9.14
0.83
0.06
6.99
4.31
2.00
Lisbon
4.88
36.39
3.33
9.58
4.97
10.03
8.57
17.17
3.63
1.47
London
24.00
7.68
5.77
17.58
20.73
4.50
1.51
5.92
10.39
1.93
Madrid
13.01
21.07
2.94
25.73
5.02
1.98
0.61
23.47
6.17
0.00
Paris
15.75
11.79
8.02
26.65
15.21
1.55
1.62
3.86
14.82
0.73
Prague
10.50
9.11
13.52
34.29
21.39
0.26
0.22
2.45
2.84
5.41
Rome
15.60
8.94
4.47
30.03
10.46
5.74
0.97
11.02
7.21
5.56
Stockholm
15.69
7.33
8.22
28.02
8.63
6.22
0.32
3.77
6.88
14.93
Warsaw
5.84
12.13
18.28
39.54
15.83
0.09
0.16
1.50
2.87
3.75
Reference
Sasha Khomenko, Enrico Pisoni, Philippe Thunis, Bertrand Bessagnet, Marta Cirach, Tamara Iungman, Evelise Pereira Barboza, Haneen Khreis, Natalie Mueller, Cathryn Tonne, Kees de Hoogh, Gerard Hoek, Sourangsu Chowdhury, Jos Lelieveld, Mark Nieuwenhuijsen. Spatial and sector-specific contributions of emissions to ambient air pollution and mortality in European cities: a health impact assessment, The Lancet Public Health, 2023. doi:10.1016/S2468-2667(23)00106-8
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