Combined effects of microplastics and other contaminants on earthworms: A critical review

In the soil environment, microplastics are often present together with other contaminants. The co-exposure to microplastics and other contaminants may result in combined effects on soil organisms. This paper summarizes recent research advances in the combined effects of microplastics and heavy metals/hydrophobic organic contaminants (HOCs) on earthworms. The effects of co-exposure on earthworms are mainly in the aspects of contaminants bioaccumulation and the mortality, behavior, growth, reproduction, oxidative response, and gut microbiota of earthworms. In general, microplastics can exacerbate the adverse effects of other contaminants on earthworms, such as facilitating the accumulation of other contaminants in earthworms, inhibiting growth rates, aggravating oxidative damage, and changing gut microbiota of earthworms. Research limitations and current gaps are discussed, and future perspectives are proposed.