Background: Epidemiologic evidence on the association between short-term exposure to ultrafine particles and mortality is weak, due to the lack of routine measurements of these particles and standardized multicenter studies. We investigated the relationship between ultrafine particles and particulate matter (PM) and daily mortality in eight European urban areas.
Methods: We collected daily data on nonaccidental and cardiorespiratory mortality, particle number concentrations (as proxy for ultrafine particle number concentration), fine and coarse PM, gases and meteorologic parameters in eight urban areas of Finland, Sweden, Denmark, Germany, Italy, Spain, and Greece, between 1999 and 2013. We applied city-specific time-series Poisson regression models and pooled them with random-effects meta-analysis.
Results: We estimated a weak, delayed association between particle number concentration and nonaccidental mortality, with mortality increasing by approximately 0.35% per 10,000 particles/cm3 increases in particle number concentration occurring 5 to 7 days before death. A similar pattern was found for cause-specific mortality. Estimates decreased after adjustment for fine particles (PM2.5) or nitrogen dioxide (NO2). The stronger association found between particle number concentration and mortality in the warmer season (1.14% increase) became null after adjustment for other pollutants.
Conclusions: We found weak evidence of an association between daily ultrafine particles and mortality. Further studies are required with standardized protocols for ultrafine particle data collection in multiple European cities over extended study periods.
From the aDepartment of Epidemiology, Lazio Region Health Service, Rome, Italy; bInstitute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; cHelmholtz Zentrum München–German Research Center for Environmental Health, Institute of Epidemiology II, Neuherberg, Germany; dUniversity of Augsburg, Environmental Science Center, Augsburg, Germany; eDepartment of Hygiene, Epidemiology and Medical Statistics, National and Kapodistrian University of Athens, Athens, Greece; fDepartment of Public Health, Center for Epidemiology and Screening, University of Copenhagen, Copenhagen, Denmark; gStockholm County Council, Centre for Occupational and Environmental Medicine, Stockholm, Sweden; hItalian National Institute for Environmental Protection and Research, Rome, Italy; iNCSR Demokritos, Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety, Environmental Radioactivity Laboratory, Athens, Greece; jIUF-Leibniz Research Institute for Environmental Medicine at the University of Düsseldorf, Düsseldorf, Germany; kMedical Faculty, University of Düsseldorf, Düsseldorf, Germany; lINSERM-Aging and Chronic Diseases, Epidemiological and Public Health Approaches (VIMA), Villejuif, France; mBarcelona Institute for Global Health - Campus MAR (ISGlobal), Barcelona, Spain; nDepartment of Environmental Science, Faculty of Science and Technology, Aarhus University, Roskilde, Copenhagen; oDepartment of Public Health, University of Helsinki, Helsinki, Finland; pDepartment of Health Protection, Living Environment and Health Unit, National Institute for Health and Welfare (THL), Kuopio, Finland; qInstitute of Environmental Assessment and Water Research, Barcelona, Spain; and rInstitute for Energy and Environmental Technology IUTA e.V., Air Quality & Sustainable Nanotechnology Unit, Duisburg, Germany.
Submitted 4 December 2015; accepted 21 November 2016.
Noemi Perez was supported by Generalitat de Catalunya 2014 SGR33.
The authors report no conflicts of interest.
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Correspondence: Massimo Stafoggia, Department of Epidemiology of the Lazio Region Health Service, Via Cristoforo Colombo 112, 00147, Rome, Italy. E-mail: email@example.com.