Co-exposure to micro(nano)plastics and metals in animals: state of the art, trends, and gaps in ecotoxicology

Studies on the effects of micro- and nanoplastics and metals have been widely explored in the field of ecotoxicology. However, interactions between these contaminants can result in adverse effects that differ from those observed under single-contaminant exposures. Considering the complexity of environmental scenarios in which multiple contaminants can occur simultaneously, this review aims to assess the state of the art of research investigating the co-exposure and combined exposure of micro- and nanoplastics and metals in animals. The systematic review of the literature indicates that this research field is relatively recent but has grown exponentially in recent years. Existing studies involve a broad network of collaboration between researchers from different countries. However, despite recent advances, there are still important gaps that need to be overcome, including limitations related to experimental design, the diversity of model species, and the combinations of contaminants investigated. In addition, there is an uneven distribution of scientific production among countries, with European and Asian nations leading research in this area. Thus, expanding the diversity of model organisms, contaminant combinations, and experimental approaches is essential to advance understanding of the ecological risks associated with combined exposure to micro- and nanoplastics and metals.