Characterization of airborne microplastics and exposure assessment in the Mahshahr special economic zone, Northern Persian Gulf

Atmospheric microplastics (MPs), due to their diminutive size and potential health impacts, have become one of the biggest environmental and health challenges facing humanity. These particles can be easily inhaled, allowing them to bypass the body's initial respiratory defenses and enter the lung alveoli. Once lodged in the alveoli, these particles can cause various negative health effects, potentially leading to respiratory issues and other systemic health problems. This study marks the first quantification of atmospheric microplastics' spatial and temporal distribution in Bandar Mahshahr, Khuzestan, Iran. Measurements were conducted over twelve periods of 24-h sampling across two months of the year at three different sites: residential, high-traffic, and industrial areas. The concentration of MPs in the indoor and outdoor air varied across the three sampling sites: it ranged from 0.16 to 1.11 particles/m³, with mean values of 0.47 ± 0.06, 0.78 ± 0.07, and 0.85 ± 0.09 particles/m³ for residential, high-traffic, and industrial areas, respectively. Industrial areas had the highest MP levels, followed by high-traffic and residential sites. Indoor air also contained significant MP concentrations. Regarding their color, and shape, the majority of MPs were identified as black-gray fibers (69.2–81.6 %) with sizes mostly below 500 μm, though larger particles (>1000 μm) were also present. Moreover, Raman spectroscopic analysis revealed that the most prevalent types of plastics were polyethylene (PE), polystyrene (PS), polypropylene (PP), and nylon. The abundance of microplastics in present study can be attributed to the primary production of plastics by petrochemical industries located in the area. Our results can be attributed to the primary production of plastics by petrochemical industries located in the area. The inhalation risk assessment showed a significant disparity in MP inhalation exposure across different age groups, with newborns and infants facing the highest (0.44 MP/kg body weight/day, followed by infants at 0.23 MP/kg body weight/day, and adults at 0.07 MP/kg body weight/day). This study contributes to a better understanding of MP behavior in the atmosphere and emphasizes the need for further research to assess the potential health risks associated with MP exposure.