Microplastic co-exposure elevates cadmium accumulation in mouse tissue after rice consumption: Mechanisms and health implications

Rice cadmium (Cd) and microplastics are prevalent contaminants, posing a co-exposure threat to humans by means of dietary intake. To assess whether co-exposure of microplastics affects the bioavailability of rice Cd, mice were exposed to Cd-contaminated rice with microplastic co-exposure. We found that polyethylene (PE), polystyrene (PS), polypropylene (PP), and polyamide (PA) microplastic co-exposure via diet consumption (2 μg g) caused 1.17-1.38-fold higher Cd accumulation in tissue of mice fed by Cd-rice. For mice with co-exposure of PE microplastics, the higher rice-Cd bioavailability corresponded to colonization of Lactobacillus reuteri (38.9 % vs 17.5 %) in the gut compared to control mice, which caused higher production of gut metabolites particularly peptides, likely causing a 'side effect' of elevating Cd solubility in the intestinal lumen. In addition, abundance of sphingosine 1-phosphate in the gut of mice was reduced under PE microplastic exposure, which may reduce intracellular calcium ions (Ca) in enterocytes and form a weaker competition in pumping of intracellular Ca and Cd across the basolateral membrane of enterocytes, leading to higher Cd transport efficiency. The results suggest elevated Cd exposure risk from rice consumption with microplastic co-exposure at environmentally relevant low concentrations.