This study aimed to verify whether Saharan dust reached south-eastern Poland in spring 2025 and to assess its influence on the chemical composition and oxidative potential of particulate matter. Using an ultra-sensitive Dekati instrument, aerosols were measured across fifteen size fractions (6 nm–10 µm), enabling the detection of particulate matter even in the finest particles—a feature not previously documented for Saharan dust. Electron paramagnetic resonance spectroscopy was used to quantitatively determine and identify radicals associated with different PM fractions. The analysis revealed a high content of ultrafine particulate matter (<1 µm), which may pose a potential risk to human health. The chemical composition of the particulate matter confirmed the long-range transport of Saharan dust over SE Poland at the beginning of March 2025. EPR measurements indicated a relatively large amount of pollutants that exhibited magnetic properties, which were not detected in the control samples. The use of advanced measurement instrumentation enabled the detection of ultrafine fractions and the identification of free radicals associated with Saharan dust, providing new insight into its oxidative potential and chemical reactivity.