Associations between sources of particle number and mortality in four European cities

Research output: Contribution to journalArticlepeer-review


  • Ioar Rivas
  • Laia Vicens
  • Xavier Basagaña
  • Aurelio Tobías
  • Klea Katsouyanni
  • Heather Walton
  • Christoph Hüglin
  • Andrés Alastuey
  • Markku Kulmala
  • Juha Pekkanen
  • Xavier Querol
  • Jordi Sunyer
  • Frank J. Kelly

Colleges, School and Institutes

External organisations

  • King's College London
  • Barcelona Biomedical Research Park
  • Pompeu Fabra University
  • Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP)
  • CSIC
  • Spanish Research Council (IDÆA-CSIC)
  • Imperial College London
  • Athens University
  • National Institute for Health Research
  • EMPA, Swiss Federal Laboratories for Materials Science and Technology
  • University of Helsinki
  • King Abdulaziz University
  • Finnish Institute for Health and Wellfare


Background: The evidence on the association between ultrafine (UFP) particles and mortality is still inconsistent. Moreover, health effects of specific UFP sources have not been explored. We assessed the impact of UFP sources on daily mortality in Barcelona, Helsinki, London, and Zurich.

Methods: UFP sources were previously identified and quantified for the four cities: daily contributions of photonucleation, two traffic sources (fresh traffic and urban, with size mode around 30 nm and 70 nm, respectively), and secondary aerosols were obtained from data from an urban background station. Different periods were investigated in each city: Barcelona 2013–2016, Helsinki 2009–2016, London 2010–2016, and Zurich 2011–2014. The associations between total particle number concentrations (PNC) and UFP sources and daily (natural, cardiovascular [CVD], and respiratory) mortality were investigated using city-specific generalized linear models (GLM) with quasi-Poisson regression.

Results: We found inconsistent results across cities, sources, and lags for associations with natural, CVD, and respiratory mortality. Increased risk was observed for total PNC and natural mortality in Helsinki (lag 2; 1.3% [0.07%, 2.5%]), CVD mortality in Barcelona (lag 1; 3.7% [0.17%, 7.4%]) and Zurich (lag 0; 3.8% [0.31%, 7.4%]), and respiratory mortality in London (lag 3; 2.6% [0.84%, 4.45%]) and Zurich (lag 1; 9.4% [1.0%, 17.9%]). A similar pattern of associations between health outcomes and total PNC was followed by the fresh traffic source, for which we also found the same associations and lags as for total PNC. The urban source (mostly aged traffic) was associated with respiratory mortality in Zurich (lag 1; 12.5% [1.7%, 24.2%]) and London (lag 3; 2.4% [0.90%, 4.0%]) while the secondary source was associated with respiratory mortality in Zurich (lag 1: 12.0% [0.63%, 24.5%]) and Helsinki (4.7% [0.11%, 9.5%]). Reduced risk for the photonucleation source was observed for respiratory mortality in Barcelona (lag 2, −8.6% [−14.5%, −2.4%]) and for CVD mortality in Helsinki, as this source is present only in clean atmospheres (lag 1, −1.48 [−2.75, −0.21]).

Conclusions: We found inconsistent results across cities, sources and lags for associations with natural, CVD, and respiratory mortality.

Bibliographic note

Funding Information: HW’s post was partially funded by the UK National Institute for Health Research Health Protection Research Unit on Environmental Exposures and Health at Imperial College London in partnership with Public Health England, King’s College London and the MTC Toxicology Unit, Cambridge. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health & Social Care or Public Health England. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 747882. While writing the manuscript, Dr. Rivas was funded by the postdoctoral fellowship programme Beatriu de Pinós (2018 BP 00114), funded by the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 programme of research and innovation of the European Union under the Marie Sklodowska-Curie grant agreement No 801370. Currently, Dr. Rivas is funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 886121. This work was supported by FEDER funds; projects HOUSE (CGL2016-78594-R) and CAIAC (PID2019-108990RB-I00), the Government of Catalonia (AGAUR 2017 SGR41). The authors also acknowledge the Project PI16/00118 funded by the Instituto de Salud Carlos III and co-funded by the European Regional Development Fund (ERDF) “A way to make Europe”. This work was produced using statistical data from ONS. The use of the ONS statistical data in this work does not imply the endorsement of the ONS in relation to the interpretation or analysis of the statistical data. This work uses research datasets which may not exactly reproduce National Statistics aggregates. Publisher Copyright: © 2021 The Authors


Original languageEnglish
Article number106662
Number of pages10
JournalEnvironment International
Early online date4 Jun 2021
Publication statusE-pub ahead of print - 4 Jun 2021


  • Daily mortality, Particle Number, Sources of Ultrafine Particles, Time Series, Ultrafine particles

ASJC Scopus subject areas