Sorption of PAHs onto microplastics in Romanian surface waters and sediments: Environmental toxicity and human health risk with emphasis on pediatric exposure

Microplastics (MPs) are emerging vectors for hydrophobic organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), in aquatic environments. Due to their high surface area and sorption potential, MPs can enhance the environmental persistence and bioavailability of toxic compounds, posing potential risks to both aquatic organisms and human health. This study investigates the distribution, sorption behavior, and effects on pollutant transport, distribution, and exposure pathways of PAHs-contaminated microplastics in two major Romanian rivers: the Prahova and Ialomita. PAHs concentrations were quantified in surface water, sediments, and microplastic particles collected from both rivers. Results revealed PAHs levels in surface waters ranging from below the limit of quantification (LOQ) to 0.0187 µg/L in the Prahova River and < LOQ to 0.0176 µg/L in the Ialomita River. Sediment concentrations varied from < LOQ to 397 µg/kg dry weight (d.w.) in the Prahova and 449-875 µg/kg d.w. in the Ialomita. Significantly elevated PAHs concentrations were detected on microplastics, with maximum values of 38.9 ng/g d.w. and 49.7 ng/g d.w., respectively. Ecotoxicological risk assessment, based on environmental quality criteria and known toxicological thresholds, indicated low to moderate ecological risks for aquatic organisms. However, health risk modeling revealed that while adult exposure remained within safe margins, children exhibited a higher non-carcinogenic risk due to increased susceptibility and intake rates. These findings highlight the role of microplastics in modifying the toxicokinetics and exposure pathways of PAHs in freshwater systems and underscore the importance of targeted monitoring and mitigation strategies to protect vulnerable populations and maintain aquatic ecosystem health.