A critical review on the interactions of microplastics with heavy metals: Mechanism and their combined effect on organisms and humans

Although individual toxicity of microplastics (MPs) to organism has been widely studied, limited knowledge is available on the interactions between heavy metals and MPs, as well as potential biological impacts from their combinations. The interaction between MPs and heavy metals may alter their environmental behaviors, bioavailability and potential toxicity, leading to ecological risks. In this paper, an overview of different sources of heavy metals on MPs is provided. Then the recent achievements in adsorption isotherms, adsorption kinetics and interaction mechanism between MPs and heavy metals are discussed. Besides, the factors that influence the adsorption of heavy metals on MPs such as polymer properties, chemical properties of heavy metals, and other environmental factors are also considered. Furthermore, potential combined toxic effects from MPs and heavy metals on organisms and human health are further summarized. • Interactions between microplastics (MPs) and heavy metals (HMs) are complex. • Combined toxicity on organisms mainly includes synergistic and antagonistic effects. • Knowledge regarding co-exposure effect of MPs and HMs to humans is still limited.