Pollutant particles of small size are produced and resuspended every day as a result of traffic. These particles, identified as particulate matter (PM₁₀, PM_2.5), can affect human health when inhaled, mostly the respiratory and cardiopulmonary systems. Some of these particles are ferromagnetic (s.l.) and their magnetic properties indicate their sources, composition and size. Coimbra is an inland city situated in the center of Portugal at a distance of 40 km from the coast. Coimbra has a total area of 320 km² and a population of about 168.000. Motor vehicle traffic is the main source of air pollutant in the city. The main goal of this research is to assess pollution levels in the urban area of Coimbra using the magnetic properties of microscopic pollutant particles on Nerium oleander leaves.