## 3 Results and Discussion
It is notable that the results of the studies conducted by [PERSON] and [PERSON] [86] in the Silesian Voivodeship confirm the persistence of high B[a]P concentrations in this region, with annual averages ranging from 6.2 to 7.1 ng\(\cdot\)m\({}^{-3}\) between 2018 and 2021. Significantly, average B[a]P concentrations can exceed 28 ng\(\cdot\)m\({}^{-3}\) during the heating season (from October to the  
Figure 2: Annual average and maximum concentrations of PM\({}_{10}\) (\(\upmu\)g\(\cdot\)m\({}^{-3}\)) measured in the period 2018–2022. end of March). These concentrations significantly exceed the regulatory limits established by the EU (1 ng\(\cdot\)m\({}^{-3}\)) and the WHO (0.12 ng\(\cdot\)m\({}^{-3}\)). Table 1 shows the annual average concentrations of PM-bound \(\sum\)7 PAHs. The highest concentrations were consistently recorded in Upper Silesia, Cracow, and Lodz. Although levels decreased over the study period, they remained very high. In 2018, the maximum concentration of PAHs was observed in Cracow, reaching 101.58 ng\(\cdot\)m\({}^{-3}\). Szczecin also exhibited a high annual average concentration of total PAHs in the same year, at 18.50 ng\(\cdot\)m\({}^{-3}\), which was 2.7 to 3.5 times higher than in subsequent years. Benzo[a]pyrene constitutes between 12% and 25% of the total \(\sum\)7 PAH concentration. The high concentrations of PAHs in urban areas of Poland, including less urbanised regions, are primarily attributed to communal and household emission sources. In 2021, total PAH emissions amounted to 260.51 Mg, 206.53 Mg (79.28%) of which originated from household fuel combustion [87]. Exceedances of permissible levels of B[a]P and its congeners are mainly caused by the combustion of solid fuels in household boilers, particularly coal and wood [86; 88; 89; 90; 91]. Of the analysed metals, Pb and Ni were the most abundant in PM\({}_{10}\) at the monitored stations. Their annual mean concentrations in the eight agglomerations between 2018 and 2022 ranged from 3.19 to 27.85 ng\(\cdot\)m\({}^{-3}\) for Pb and from 0.61 to 4.27 ng\(\cdot\)m\({}^{-3}\) for Ni. Lower concentrations were recorded for As (0.45 \(\div\) 2.66 ng\(\cdot\)m\({}^{-3}\)) while Cd was the least abundant metal in PM\({}_{10}\), with concentrations ranging from 0.10 to 1.00 ng\(\cdot\)m\({}^{-3}\) (Table S3). To better understand these differences, it is important to consider national emission inventories. In 2021, the annual emissions of Pb, Ni, As, and Cd in Poland amounted to 279.90 Mg, 77.41 Mg, 14.95 Mg, and 10.96 Mg, respectively. While industrial processes were the main source of Pb, Cd and As emissions-accounting for 55%, 39% and 36% of total emissions, respectively--the dominant source of nickel was fuel combustion in the energy sector, accounting for 43% of national Ni emissions [87]. The diverse emission sources, meteorological conditions, and urban characteristics of the individual agglomerations contribute to the observed regional differences in heavy metal concentration levels. The highest average annual concentrations of Pb, Cd, and Ni were recorded in the Upper Silesia Agglomeration (Pb: 27.85 ng\(\cdot\)m\({}^{-3}\); Cd: 1.00 ng\(\cdot\)m\({}^{-3}\); Ni: 4.27 ng\(\cdot\)m\({}^{-3}\)). This is a consequence of the large number of industrial facilities in the area, including coal-fired power stations, steel mills, coking plants, and other industrial plants. Numerous studies confirm that emissions from the combustion of fossil fuels, metallurgy, and metal ore processing are the main sources of these elements in PM\({}_{10}\) in this region [92; 93; 94]. However, of particular significance is the fact that the highest maximum daily average lead concentration in the period 2018-2022 was not recorded in the Upper Silesia Agglomeration but in Wroclaw in 2021, at 106.02 ng\(\cdot\)m\({}^{-3}\). This is over 26% higher than the maximum lead concentration recorded in Upper Silesia in the same year (83.80 ng\(\cdot\)m\({}^{-3}\)). Despite the area's lack of heavy industries, such high concentrations