Source apportionment and health risk from airborne potentially toxic elements in Tehran (Iran): use of lichen biomonitoring data

This study investigated the sources and health effects of airborne PTEs in the Tehran metropolis (Iran) using lichen biomonitoring coupled with spatially resolved receptor modelling (PMF) and specific risk indices. Lichen samples (Anaptychia setifera) were transplanted from a clean site and exposed for 4 months across 24 monitoring stations. The PTE concentrations were determined using ICP-OES analysis. The results showed that the highest element concentrations were related to Al and Fe, with values of 2796±2059 and 1293±153, respectively. The contamination factor values indicated that the study area was heavily polluted (CF ≥ 3) for Pb, Cr, Co, Cu, Fe, Al, Ni, and Zn and unpolluted (CF<1.2) for As and Mn. The enrichment factor showed that all elements except As and Mn were significantly enriched (EF > 100%) at all monitoring stations. PMF identified human activities (such as traffic and industry) and land sources as the primary sources of PTEs in the air in Tehran. The total carcinogenic potential risk (TCR) in both age groups exceeded the maximum acceptable level of carcinogenic risk target, indicating a high risk of cancer in both groups. These findings confirm the reliability of A. setifera as a biomonitor for monitoring human exposure to PTEs.