During the past few decades, epidemiological studies have consistently linked the exposure to particulate matter (PM) in ambient air to various negative health effects resulting in an increase in mortality and morbidity. Traditionally, these studies have focused in exposures to mass concentration of PM with a diameter ≤10 and ≤2.5 µm (PM10 and PM2.5, respectively), due to the availability of measurement techniques and their inclusion in the legislation which make them being extensively measured across Europe. However, negative health effects are expected to be enhanced with decreasing particle size since nose and bronchioles are inefficient at filtering ultrafine particles (UFP, PM ≤ 0.1 µm). Moreover, depending on their source, UFP may affect differently to human health. No previous study has yet tried to tackle the fundamental issue of identifying associations between the different sources contributing to UFP. Although the growing literature is pointing towards UFP as main culprit of human health impairment, there are currently no legal ambient standards for UFP. Therefore, further information on the effects of UFP is needed in order to provide regulatory authorities with sufficient evidence of which component from the mixture of PM involves more risk to human health.
This investigation should not focus on a single city or area, since different meteorological conditions, pollutant emissions and other parameters may influence divergently the sources of UFP. This requires an international collaboration, which will be the core of this study (and led by the applicant): institutions from the United Kingdom, Spain, Switzerland and Finland will join efforts and knowledge to quantify the health effects of primary and secondary UFP.
The main objectives of the Health Up (Differentiated health impacts of primary and secondary ultrafine particles) are:

• To uncover the differences in the sources of UFP in the cities of London (UK), Barcelona (Spain), Zurich (Switzerland) and Helsinki (Finland), which have different meteorological conditions and emissions, based on long time-series of size-segregated UFP data.
• To determine the health impacts (with mortality and hospital admissions as outcomes) of the exposure to PM10, PM2.5, BC, UFP and differentiated primary and secondary UFP in different size-range in London, Barcelona, Zurich and Helsinki.

The results of this work will:
- serve as indication to the corresponding authorities of which air pollutants should be included in future EU legislation about air quality
- add insight to the growing body of literature on the health effects of UFP
- and tackle an important issue not being evaluated yet: the health effects of UFP according to their source

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.
Health ¹UP₂ is led by King’s College London but is a collaborative project with the following centres: Institute for Environmental Assessment and Water Research (IDAEA-CSIC, Spain), Barcelona Institute for Global Health (ISGlobal, Spain), University of Birmingham (UK), Swiss Federal Laboratories for Material Science and Technology (Switzerland) and University of Helsinki (Finland).