Spatial mapping and risk assessment of microplastic contamination in drinking water catchments from north of the Persian Gulf.

Microplastics (MPs) are emerging contaminants in drinking water that raise global concerns due to their health risks and long-term environmental persistence. These tiny plastic particles can accumulate within human bodies and ecosystems, making it essential to understand their presence and behavior in water sources, especially in drinking water. In Khuzestan Province, which is of strategic importance in the Gulf region. This study assesses the concentration and types of MPs entering and leaving these 11 treatment plants. In untreated water, particle size analysis revealed that 50% of MPs were measured under 101 µm, with fibers being the most common type (47%), followed by fragments and pellets. Although treatment processes reduced overall MP concentrations, fibers remained the dominant residual type, making up 71% of the MPs in treated water. The main polymers identified were polyethylene (PE) and polypropylene (PP), with PE accounting for up to 75% of MPs in some areas. In terms of color, black/gray MPs were most prevalent (45%), followed by blue, red/pink, yellow/orange, and white/clear particles. While most treatment plants achieved significant reductions in MP levels, some were less effective, likely due to differences in treatment technologies. Notably, the S10 plant in Bandar Mahshahr had especially high inlet MP levels, possibly due to the region's high industrial and human activities. Estimated daily intake (EDI) for adults was approximately 0.00482 MPs per kg of body weight per day, with children having a higher intake of around 0.01866 MPs per kg per day. These findings highlight the need to enhance treatment technologies, control upstream MP sources, and establish routine monitoring to protect water quality in Khuzestan and the wider Gulf region.