Human Health Risk Assessment of PAHs from Anzali Wetland

Anzali Wetland, as an internationally protected area under the Ramsar Convention, has been exposed to increasing concentrations of PAHs due to various factors such as transportation bridges, military facilities, urban sewage systems, gas stations, fishing boats, tourism, and fishing activities. PAHs emissions pose significant health risks to local populations who depend heavily on the wetland ecosystem, leading to the transfer and accumulation of pollutants in biological tissues through the food chain and dermal contact with sediments. Accordingly, the concentration of 16 priority PAH compounds, as identified by USEPA, was assessed in sediments from two regions: the central-northern area with high PAH emissions and the southern area of the wetland with lower emissions. PAH compounds in sediment samples were extracted using a Soxhlet apparatus. The extracted samples were then analyzed using column chromatography and gas spectrometry to identify and quantify the 16 PAH compounds present. To compare PAH concentrations between the northern-central and southern regions of Anzali Wetland, PERMANOVA was performed. Human health risks associated with PAH ingestion and dermal exposure were assessed using ILCR approach and TEQBaP. The findings indicated that the total PAH concentration in sediments from the northern and central regions ranged from 2168.87 to 11403.56 ng/g dry weight, with an average of 6897.60 ng/g dry weight. In contrast, the total PAH concentration in the southern region was between 48.02 and 276.03 ng/g dry weight, averaging a dry weight of 132 ng/g. PERMANOVA results indicated a significant difference in PAH concentrations between different wetland regions (Pseudo-F=127.05, p=0.001). Furthermore, TEQBaP levels in the northern-central region (166.43) were considerably higher than in the southern region (26.67). Based on ILCRingestion assessments, the cancer risk due to sediment ingestion in the wetland was evaluated as negligible at 7×10⁻⁷. However, ILCRdermal values obtained in the wetland at 1×10⁻³ indicate a high carcinogenic risk from dermal exposure to PAH compounds in these sediments. Given that Anzali Wetland is classified as contaminated and the total incremental cancer risk is estimated at 1×10⁻³, this indicates a high carcinogenic risk for local residents. The elevated cancer risk in Anzali Wetland-particularly in the northern-central region, which constitutes a large portion of the wetland-is strongly associated with high concentrations of petroleum derivatives and methylation. Among the 16 PAH compounds measured, naphthalene exhibited the highest concentrations in more polluted locations. To mitigate pollution impacts, replacing asphalt with permeable pavement in areas surrounding the wetland is recommended, as this can help reduce runoff during rainfall. Additionally, reducing traffic by relocating parking areas farther away is advised to prevent pollutants from entering the wetland environment.