Leaching of Di(2-ethylhexyl) Phthalate from Polyvinyl Chloride Microplastics in Synthetic Freshwater, Seawater, and Fish In Vitro Digestion Fluids.

We investigated the leaching of additives from microplastics (MPs) derived from commercial polyvinyl chloride (PVC) wire insulation into synthetic freshwater, synthetic seawater, and a fish in vitro digestion system. The experiments used an MP loading of 1 mg mL-1 to meet the instrumental LOQ; therefore, the system should be interpreted as a controlled mechanistic design rather than a direct simulation of environmental MP exposure. We identified aging as a critical factor for DEHP leaching. While nonaged MPs showed no quantifiable leaching, UV-aged MPs leached DEHP instantaneously across all media. In controlled aqueous systems, elevated salinity suppressed apparent DEHP concentrations, yielding lower values in seawater (46.8 ± 3.6 μg L-1) compared to freshwater (63.1 ± 4.4 μg L-1). During in vitro digestion, ground fish food acted as a dietary sorptive matrix and reduced apparent fluid-phase DEHP concentrations. DEHP reached 50.0 ± 3.4 μg L-1 in the gastric phase and 49.8 ± 2.4 μg L-1 in the intestinal phase without added food, whereas fluids containing ground fish food showed lower concentrations of 27.9 ± 2.3 μg L-1 and 27.3 ± 2.0 μg L-1, respectively. These findings demonstrate that UV aging, salinity, and dietary matrices regulate DEHP leaching and bioaccessibility from PVC MPs.