Antibiotic-mediated adsorption and combined biotoxicity of microplastics and chromium species in the dynamic stomach model.

BACKGROUND: Microplastics (MPs) can adsorb and accumulate chromium and antibiotics in environments, releasing these pollutants in the human stomach and inducing potential health risks. Although simple static gastrointestinal models have been adopted to preliminarily evaluate the bioaccessibility of chromium-loaded MPs (Cr-MPs) by maintaining constant digestive parameters, they cannot faithfully replicate the fluid mechanics and dynamic physiological variations of real human gastric digestion. Moreover, current research lacks systematic exploration of antibiotic-modulated chromium adsorption on MPs and their combined toxicological effects during stomach digestion.

RESULTS: A self-developed dynamic stomach model coupled with HPLC-ICPMS was adopted to explore chromium adsorption by three typical antibiotics-affected MPs and the gastric release and toxicity of Cr-MPs. Chromium species adsorption on PVC MPs is mainly physical, and antibiotics significantly promote chromium adsorption on MPs via multiple interfacial interactions. During gastric digestion, Cr(VI) on MPs was rapidly reduced to Cr(III) within 15 min, and antibiotic intervention reduced chromium release rate but increased total release amount. Both Cr(III) and Cr(VI) posed no non-carcinogenic hazards, while antibiotics elevated children's Cr(VI) carcinogenic risks from acceptable to significant levels.

SIGNIFICANCE: This work systematically investigates the adsorption mechanism of chromium by MPs in the environment, the release and speciation transformation of chromium during gastric digestion, and the effects of antibiotics on the aforementioned processes. It supplies a reference for exploring the interactions between MPs, antibiotics, and metals in the human digestive system, offering scientific support for the accurate assessment of human health risks posed by MPs-bound heavy metal pollutants.