Results for several NIR data sets are presented, showing that MDPS selects reliable updated NAR models that either outperform or rival prediction errors from total recalibrations that necessitate laboratory analysis of samples to obtain the corresponding calibration sample reference values. 16 16. Aerosol Metrology, Advanced X-ray Techniques, Chromatography-Mass, Environment, Food/Proteomics, Sample Spectrometry, Archaeometry  
_16.1. Magnetic Nanoparticles an Indicator of Health Risks Related to Anthropogenic Airborne Particulate Matter_  
**C. Martinez-Boubeta 1,*, K. Simeonidis 2, D. Sarigiannis 2, M. Kermenidou 2 and LI. Balcells 3**  
1. Ecoresources P.C., Giannitson-Santaroza Str. 15-17, 54627 Thessaloniki, Greece  
2. Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece  
3. Institut de Ciencia de Materials de Barcelona, CSIC, 08193 Bellaterra, Spain  
* Correspondence: oboubeta@gmail.com  
A large body of literature has consistently shown an association between particulate matter (PM) pollution and rises in the numbers of deaths from cardiopulmonary disease, especially among older people and those with comorbidities [1]. Very recently, the possibility of airborne magnetic nanoparticles to enter the brain directly by crossing the olfactory unit has been demonstrated, suggesting a potential hazard for the health of the aging human due to urban air pollution [2]. This work combines magnetic and microscopic chemical methods in order to provide insights into the impact of daily and seasonal life patterns on atmospheric pollution level in Thessaloniki, the second largest city of Greece. The amount of magnetically-responding dust collected in pumped-air filters was at least 0.5% wt., although it shows seasonal maxima during autumn months (0.8% wt.) when an increase in commuting occurs, reaching levels 50% higher in downtown than in suburban areas [3]. In combination with high-resolution transmission electron imaging and elemental analysis, it was possible to conclude that Fe\({}_{3}\)O\({}_{4}\) and similar ferrites--some of them including heavy metals--with nuclei sizes of approximately 15 nm, are the dominant magnetic phases. Importantly, nasal cytologic samples collected from residents of these areas showed exactly the same magnetic behavior, thus, verifying the critical role of nanosized magnetic particles into the evaluation of air pollution threats. In this framework, we end by exploring whether seasonal variations of PM have positive causal effects on coronavirus mortality. Our results underscore that it is possible, if not likely, that pollution nanoparticles Granger causes COVID-19 death rates (\(p<0.05\)). This project has received funding from the EU-H2020 research and innovation programme under grant agreement No 654360 having benefitted from the access provided by ICMAB-CSIC and Universitat Autonoma de Barcelona in Bellaterra-Barcelona within the framework of the NFFA-Europe Transnational Access Activity. ## References  
* Seaton et al. 1995 Seaton, A.; Godden, D.; MacNee, W.; Donaldson, K. Particulate air pollution and acute health effects. _Lancet_**1995**, _345_, 176-178. * Maher et al. 2016 Maher, B.A. ; Ahmed, I.A.M. ; Karloukovski, V.; MacLaren, D.A. ; Foulds, P.G. ; Allsop, D.; Mann, D.M.A. ; Torres-Jardon, R.; Calderon-Garcidouenas, L. Magnetic pollution nanoparticles in the human brain. _Proc. Natl. Acad. Sci. USA_**2016**, _113_, 10797-10801. * Kermenidou et al. 2021 Kermenidou, M.; Balcells, L.; Martinez-Boubeta, C.; Chatziavramidis, A.; Konstantinidis, I.; Samaras, T.; Sarigiannis, D.; Simeonidis, K. Magnetic nanoparticles: An indicator of health risks related to anthropogenic airborne particulate matter. _Environ. Pollut._**2021**, _271_, 116309.