Investigation of the extent of contamination of heavy metals in cabin air filters using health risk and environmental indices assessment

The aim of this research was to quantitatively assess the levels of heavy metals contamination in dust collected from cabin air filters (CAF) of passenger vehicles across three urban zones in Neyshabur, Iran, characterized by varying traffic densities. For this purpose, 30 samples were taken from oil change service centers and the total concentration of heavy elements was measured by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The results demonstrate significant variability in heavy metal concentrations across both traffic zones and vehicle types, with geo-accumulation index (I ~ geo~) values for lead (Pb) reaching up to 7.4 across all zones, indicating very severe enrichment. The health risk assessment was conducted as a screening-level, scenario-based evaluation under hypothetical ingestion, inhalation, and dermal exposure conditions rather than as a direct estimate of actual exposure among vehicle occupants. Under these hypothetical exposure scenarios, the calculated Hazard Index (HI) for non-carcinogenic risks remains below the safety threshold (HI < 1) for all elements and population groups, with Pb being the main contributor to the estimated non-carcinogenic effects. This trend is particularly pronounced in children, with HI values reaching up to 0.11, substantially higher than those observed in adults. These finding highlights child’s greater susceptibility, likely due to their distinct physiological characteristics and behavioral patterns. Furthermore, the target cancer risk (TR) values for cadmium (Cd) and nickel (Ni) fall within the range of 10⁻⁶ to 10⁻⁵, showcasing a low to moderate carcinogenic risk. While these values remain below immediate action levels, they necessitate ongoing monitoring and preventive measures, especially for chronically exposed populations such as urban drivers.