Study of the scavenger and vector roles of microplastics for polyhalocarbazoles under simulated gastric fluid conditions

Microplastics entering the digestive system of living organisms can serve as a carrier of hydrophobic organic pollutants (HOPs), increasing their exposure levels and the health risks they pose to both humans and animals. The desorption kinetics of six polyhalocarbazoles (PHCZs) from 5 mm and 0.15 mm polypropylene (PP) and polyvinyl chloride (PVC) microplastic particles were assessed using a combined microplastics and food system, representing the gastric system of vertebrates and invertebrates. Results showed that the chemical transfer of PHCZs is biphasic and reversible, with rapid exchange occurring within 2-48 h, followed by a period of slow transfer, which continues for weeks to months. The desorption capacity of PHCZs loaded on 0.15 mm microplastic particles was greater than that of 5 mm particles. The bioavailability percentage of PHCZ congeners for PP (24.2%-65.3%) and PVC (43.5%-57.2%) in the vertebrate fluid system were all lower than those in the invertebrate system (34.2%-70.7% for PP and 56.3%-72.7% for PVC, respectively). These findings indicate that physiological conditions, such as polarity, ingestion fluid, and microplastic affect the desorption of PHCZs from microplastics. In addition, desorption from PP was inhibited by the presence of foodstuff loaded with PHCZs due to competition, while desorption from PVC was not significantly affected by the presence of PHCZs contaminant food. Microplastics could provide a cleaning function in gastric fluid systems containing contaminated foodstuff, especially PP, which was capable of competitive adsorption of PHCZs from food. Few investigations have focused on the adverse effects of microplastic ingestion on human health, particularly in their role as vectors for HOPs, compared to other routes of exposure and transport. Therefore, these findings provide valuable insight into the health risks associated with dietary intake of microplastics and HOPs.