Atmospheric fine particulate matter (PM_2.5) is a critical indicator of air quality, with substantial implications for human health. Understanding the emission sources and chemical composition of PM_2.5 is crucial for mitigating possible adverse health effects. This study spans five diverse cities on three continents from north and south hemisphere: Stockholm (Sweden), Kyoto (Japan), Limeira, Ribeirão Preto, and Cáceres (Brazil). Our objective was to assess PM_2.5 chemical composition and regional and long-range transport influences to identify the main sources of particulate air pollution at these cities during the winter/dry seasons. All studied cities but Kyoto exhibited PM_2.5 levels above World Health Organization (WHO) guidelines, with the Brazilian cities experiencing the highest fine particle pollution levels, implying increased adverse health risks. We observed significant variations in concentrations of polycyclic aromatic compounds (PACs), monosaccharide anhydrides (MAs), and inorganic elements. Limeira exhibited the highest levels of total PACs (median level of 12.4 ng m⁻³), while Cáceres displayed high variability of PACs, most likely due to episodic regional wildfire events. MA concentrations were significantly higher in Limeira and Ribeirão Preto and together with elevated levels of retene and potassium (K) they suggested a substantial influence of biomass burning. Backward air mass trajectory analysis suggested widespread Amazon and Savanna wildfires along with local fires as main contributors for these sites. All source identification approaches highlighted differences among the cities, with Stockholm and Kyoto showing influence of sources related to traffic emissions, waste burning, and long-range transport, and Brazilian cities traffic, industrial, biogenic, and more evident biomass burning. This cross-continental study provides valuable insights into PM_2.5 composition and emission sources, emphasizing the impact of different emissions on air quality. Our findings underscore the importance of local strategies to mitigate air pollution and protect public health, especially in regions where PM_2.5 levels consistently exceed recommended guidelines.