This study investigated the bioaccumulation of PTEs in the 22 districts of the Tehran metropolis using the lichen Anaptychia setifera collected from Kalpoosh unpolluted area in Semnan province and exposed for 4 months in the study area using the lichen transplant technique. The concentrations of eight potentially toxic elements in the lichen were quantified using ICP-OES analysis. PCA was used to detect common sources of PTEs, and distribution maps were produced using QGIS. A statistically significant difference in the toxic elements was observed among the different stations in the Tehran metropolis. The CF index results indicate severe pollution (CF ≥ 3) for all eight studied toxic elements in the atmosphere of the Tehran metropolis. The values of the PLI index in the monitoring stations were calculated in the range of 14–31, confirming very high pollution (PLI ≥ 2.5) in the study area. The results showed a significant accumulation of all investigated toxic elements. Toxic elements such as Fe, Al, and Cr were primarily derived from natural geogenic sources, whereas Co, Cu, Ni, Pb, and Zn originated from anthropogenic sources, predominantly vehicular traffic, as depicted by the distribution patterns of these toxic elements, with peaks near sites with heavy traffic. Overall, the entire study area exhibited severe pollution levels.
