Air is a natural resource that is part of local and global ecosystem services. The latest burden estimates reflect the impressive role air pollution, and principally particles lower than 10 and 2.5 um (PM10 or PM2.5), plays in cardiorespiratory illness and premature deaths. Also, air pollution and climate change are closely related. While technological progresses have reduced emissions from motor exhausts, traffic non-exhaust (brake, tyre and pavement wear, and road dust resuspension), together with cooking emissions, have emerged as major, but overlooked, contributors to air pollution in urban areas, posing obvious research and policy challenges. SOPRO aims to: i) provide scientific support on the peculiarities of Portuguese and Brazilian urban areas causing the PM2.5/PM10 target values to be widely surpassed, accurately determine source contributions, and identify those responsible for the exceedances, ii) link physico-chemical properties of emissions to health risks, and iii) propose source-oriented mitigation strategies. SOPRO addresses the urgent need for research on integrated assessment of air quality requested by the Portuguese strategy for air (ENAR2020), fitting 3 RIS3 priority areas and 4 societal challenges related to Climate Action, Health and Wellbeing, and Transports. Recognising the need to further characterise traffic particulate emissions, a concerted strategy will be followed to obtain exhaust and non-exhaust source profiles: i) samples of tyre and brake wear; ii) wear particles from different pavements and tyres generated in a road simulator; ii) exhaust emissions on a chassis dynamometer from diverse vehicle categories representing the South European and Brazilian fleets; iii) measurements in road tunnels; iv) samples from road dust resuspension. Moreover, the fumes from commercial kitchens representing a variety of Latin cuisine styles will be collected. To obtain chemical fingerprints of sources, a vast array of cutting edge analytical techniques will be applied to samples. A toxicological screening of particles in relation to their physico-chemical properties will constitute another breakthrough. Chemical transport models will be applied to forecast primary and secondary pollutants in São Paulo and selected regions in Portugal by incorporating the new emission profiles and updated inventories, and considering different emission and climate change scenarios, and air pollution control policies. SOPRO is a joint initiative of UAVR/CESAM and USP, both with broad experience in atmospheric sciences, but received the support of well-known centres of excellence: ARPA Formulário Portugal 2020 Página 28 de 96 501461108 :: UNIVERSIDADE DE AVEIRO Lombardia and University of Florence (Italy), IDAEA and CIEMAT (Spain), VTI (Sweden), KIT (Germany) and UERJ (Brazil). Thus, SOPRO will benefit from complementary sampling and analytical capabilities of supporting partners, generating a transcontinental and multidisciplinary project of atmospheric scientists, transport engineers, chemists, toxicologists and modellers.