Bioaccessibility of Metals and Metalloids in Microplastics: In Vitro Digestive Simulation Under Fed Conditions

Introduction: Microplastics, including low-density polyethylene (LDPE), have become a
significant environmental concern due to their persistence in ecosystems and their potential to
release hazardous metals and metalloids during digestion. This study aimed to evaluate the
bioaccessibility of eight elements (As, Br, Cd, Cr, Pb, Sn, Sb, and Zn) from LDPE
microplastics, specifically the certified reference material ERM®-EC680m (low-density
polyethylene).
Methods: The Versantvoort method was employed, which simulates human digestion using
digestive fluids (saliva, gastric juice, duodenal fluid, and bile). This method allows for the
assessment of element release during both the gastric and gastrointestinal phases, with pH
control and constant agitation at 37ºC.
Results: A mass study was performed using four different sample amounts (0.2, 0.4, 1, and 2 g)
to evaluate the effect of sample mass on bioaccessibility. Bioaccessibility values ranged from
1% to 10%, with some elements showing values below 1%. A trend was observed where
bioaccessibility decreased as sample mass increased. The effect of particle size was also studied,
dividing the samples into three size intervals: 0.25–0.5 mm, 0.5–0.84 mm, and >0.84 mm.
Bioaccessibility values again ranged from 1% to 10%, with no significant effect based on
particle size. Three distinct release patterns were observed between the gastric and
gastrointestinal phases: 1) elements predominantly solubilized in the gastric phase (As, Cr, Zn,
Cd), 2) elements solubilized mainly in the gastrointestinal phase (Br, Sb, Sn), and 3) elements
showing reduced bioaccessibility due to precipitation in the gastrointestinal phase (Pb).
Conclusions: These findings emphasize the complexity of metal release from microplastics,
influenced by digestive conditions and metal speciation, and highlight the need for regulation of
polymeric materials to prevent human exposure.