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Sweat-induced aggregation of nanoplastics with different sizes and functionalities: Implications for global and body-region variability in dermal penetration risks
Summary
This study measured how sweat composition (pH, electrolyte concentration) affects aggregation kinetics of polystyrene nanoplastics of different surface charges (20–50 nm), finding that acidic sweat accelerates aggregation for negatively charged particles while alkaline sweat drives aggregation of positively charged ones — with implications for skin penetration risk.
Sweat-induced aggregation influences dermal penetration risks of nanoplastics. This study investigated the aggregation kinetics of unmodified (PS20 and PS50), amino-modified (APS50), and carboxyl-modified (CPS50) polystyrene nanoplastics (20-50 nm) in sweat standards and evaluated penetration risks using global sweat data. Negatively charged PS20, PS50, and CPS50 aggregated fastest (1.06-3.51 nm/s) in acidic sweat, while positively charged APS50 aggregated most rapidly (3.30 nm/s) in alkaline sweat. Elevated particle and sweat concentrations promoted aggregation. APS50 and CPS50 exhibited the highest heteroaggregation rates in acidic sweat at a 1:1 ratio. Urea and lactic acid stabilized PS50 and APS50, respectively, while L-histidine and inorganic constituents enhanced aggregation. Dermal penetration potential ranked CPS50 > APS50 > PS20 > PS50. Sweat-induced aggregation reduced stratum corneum penetration but not entry through hair follicles or sweat glands. Penetration probability (0-53.91 %) and flux (3.11 × 10 to 9.31 × 10 particle·s·m) for PS50 varied globally, with higher values observed in Europe, South America, and Oceania. APS50 displayed higher critical diffusion concentrations (50-115 mM), indicating greater penetration potential. Both PS50 and APS50 posed the highest penetration risks in the calf region. These findings underscore the role of sweat-induced nanoplastic aggregation in modulating dermal penetration risks across global regions and body areas.