Periodic Reporting for period 2 - nPETS (NANOPARTICLE EMISSIONS FROM THE TRANSPORT SECTOR: HEALTH AND POLICY IMPACTS)
Reporting period: 2022-12-01 to 2024-11-30
An ultrafine particle or a nanoparticle can be defined as a particle with a diameter smaller than 100 nm. Ultrafine particles originate primarily from the transport sector, industrial activities and combustion processes for domestic heating. They can also form in the atmosphere as secondary particles. The nPETS project represented a critical step toward understanding and mitigating the risks associated with transport-generated nanoparticle emissions. By mapping emissions, assessing their toxicity, and suggesting mitigation strategies, the project aimed not only to improve public health but also to address a regulatory gap within the EU.
The nPETS project developed advanced air quality assessment tools to evaluate urban-scale nanoparticle emissions and support effective air quality management. In 2021, the estimated mean annual exposure to nanoparticles in Stockholm was 2150 particles/cm³. Reducing this exposure for the city's population is expected to save 1690 quality adjusted life years, saving € 507M annually in health costs. The dominant source is exhaust emissions from road traffic (90 %). Followed by sea traffic 9 %, Aviation and non-exhaust emission from road traffic contribute less than 1 % each. Scenario modelling in all nPETS core cities (Stockholm, Barcelona, Leeds and Thessaloniki) provided evidence that an effective way of improving citizen health is a combined effect of a rapid renewal of vehicle fleets and an early introduction of strict low emission zones.
The nPETS project developed advanced air quality assessment tools to evaluate urban-scale nanoparticle emissions and support effective air quality management. In 2021, the estimated mean annual exposure to nanoparticles in Stockholm was 2150 particles/cm³. Reducing this exposure for the city's population is expected to save 1690 quality adjusted life years, saving € 507M annually in health costs. The dominant source is exhaust emissions from road traffic (90 %). Followed by sea traffic 9 %, Aviation and non-exhaust emission from road traffic contribute less than 1 % each. Scenario modelling in all nPETS core cities (Stockholm, Barcelona, Leeds and Thessaloniki) provided evidence that an effective way of improving citizen health is a combined effect of a rapid renewal of vehicle fleets and an early introduction of strict low emission zones.
With state-of-the-art particle instruments, the nPETS consortium monitored and sampled the ultrafine transport-generated particles from shipping, road, rail, and aviation in the field and controlled laboratory environments. This includes aged and fresh aerosols and primary and secondary components. Characterisation of the emissions includes linking their sizes, chemical compositions, and morphologies to their specific emission sources. All quantification and monitoring have been performed with the same type of instruments to ensure comparable measurement results. The characterisation also includes toxicology studies based on sampled particles from filters, in situ cell exposure with an Air Liquid Interface system that can mimic the interactions of airborne particles with lung cells and a zebrafish embryo model.
Ultrafine particle emissions have been identified in all field studies, i.e. street canyons, urban backgrounds, harbours, airports, and train stations. The 2021 Air Quality Guidelines from the WHO include both recommended low and high limit values. Most measured ultrafine particle number concentration levels are above the high-level limit, and all are above the low-level limit. The cleanest environments were urban background sites and subways, while airports and road sites including road tunnels were the most polluted environments. Further, at all sites we observed secondary particle formations and at some locations they were dominating. Toxic effects were linked to car and ship emissions and were higher in the cold season than in the warm season. Chemical analyses followed by correlation and source apportionment analyses identified PAHs and combustion processes as the main drivers of the observed toxic effects.
All studied non-exhaust sources—including mechanical brakes, clutches, tire-to-road interactions, railway wheel-to-rail contacts, and electric power systems for trains—were found to produce ultrafine particle emissions. Gaseous emissions from brake wear were identified as an unexpected source of secondary particulate matter.
Lab testing revealed significant differences in the chemical composition of ultrafine particles compared to larger particles with diameters up to 2.5 micrometers. Based on this study, it can be concluded that chemical data from coarser non-exhaust emission fractions should not be used to assess the toxicological behavior of nanoparticle emissions generated by the same sources.
The nPETS project also conducted extensive testing on five modern vehicles, all of which were confirmed to be low emitters and compliant with Euro 6 limits. However, testing of a Euro 6d diesel vehicle, including during diesel particle filter regeneration, revealed a significant impact of regeneration events, with over 95% of the total particle number emitted during these periods. Preliminary analysis further suggested a decrease in cell viability linked to regeneration particles.
Similar to the toxicology results from the nPETS field campaigns, the findings from the laboratory campaigns were also converted into toxicology scores. The greatest variation was observed in car disc brake friction materials, with results positioned between those of tailpipe exhaust emission.
A database of measurement results has been compiled and made publicly available, representing a significant and unique contribution by nPETS. In addition, regular collaboration with parallel EU funded projects (LEON-T and ULTRHAS) focusing on particle emissions has facilitated interdisciplinary engagement, resulting in the forthcoming publication of a jointly authored policy paper.
Ultrafine particle emissions have been identified in all field studies, i.e. street canyons, urban backgrounds, harbours, airports, and train stations. The 2021 Air Quality Guidelines from the WHO include both recommended low and high limit values. Most measured ultrafine particle number concentration levels are above the high-level limit, and all are above the low-level limit. The cleanest environments were urban background sites and subways, while airports and road sites including road tunnels were the most polluted environments. Further, at all sites we observed secondary particle formations and at some locations they were dominating. Toxic effects were linked to car and ship emissions and were higher in the cold season than in the warm season. Chemical analyses followed by correlation and source apportionment analyses identified PAHs and combustion processes as the main drivers of the observed toxic effects.
All studied non-exhaust sources—including mechanical brakes, clutches, tire-to-road interactions, railway wheel-to-rail contacts, and electric power systems for trains—were found to produce ultrafine particle emissions. Gaseous emissions from brake wear were identified as an unexpected source of secondary particulate matter.
Lab testing revealed significant differences in the chemical composition of ultrafine particles compared to larger particles with diameters up to 2.5 micrometers. Based on this study, it can be concluded that chemical data from coarser non-exhaust emission fractions should not be used to assess the toxicological behavior of nanoparticle emissions generated by the same sources.
The nPETS project also conducted extensive testing on five modern vehicles, all of which were confirmed to be low emitters and compliant with Euro 6 limits. However, testing of a Euro 6d diesel vehicle, including during diesel particle filter regeneration, revealed a significant impact of regeneration events, with over 95% of the total particle number emitted during these periods. Preliminary analysis further suggested a decrease in cell viability linked to regeneration particles.
Similar to the toxicology results from the nPETS field campaigns, the findings from the laboratory campaigns were also converted into toxicology scores. The greatest variation was observed in car disc brake friction materials, with results positioned between those of tailpipe exhaust emission.
A database of measurement results has been compiled and made publicly available, representing a significant and unique contribution by nPETS. In addition, regular collaboration with parallel EU funded projects (LEON-T and ULTRHAS) focusing on particle emissions has facilitated interdisciplinary engagement, resulting in the forthcoming publication of a jointly authored policy paper.
The nPETS project developed advanced air quality assessment tools to evaluate urban-scale nanoparticle emissions and support effective air quality management. The project demonstrated that a rapid renewal of vehicle fleets and the early introduction of strict low emission zones in major cities can significantly improve public health. It showed the importance of addressing exhaust and non-exhaust emissions, as well as secondary particle formation. By identifying toxicological impacts and linking emissions to specific sources, nPETS has paved the way for better regulatory standards and health protection measures across Europe. The socioeconomic impact, as illustrated in Stockholm, highlights substantial health benefits and cost savings when addressing nanoparticle pollution effectively.