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

Abstract

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^-1) 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 (Ca²⁺) in enterocytes and form a weaker competition in pumping of intracellular Ca²⁺ and Cd²⁺ across the basolateral membrane of enterocytes, leading to higher Cd²⁺ transport efficiency. The results suggest elevated Cd exposure risk from rice consumption with microplastic co-exposure at environmentally relevant low concentrations.

Keywords: Cadmium; Co-exposure; Gut microbiota; Lactobacillus; Microplastics.