The role of plastics in the accumulation and release of trace elements in the environment
Plastics are an emerging class of environmental contaminants whose impacts are not yet fully understood. Trace elements, another class of environmental contaminant and commonly associated with plastics, have been widely researched and are known to be toxic to organisms. However, the combined impacts of these two contaminants on the environment remain unclear. Here, we reviewed the current knowledge of the types and concentrations of trace elements associated with plastics, the role of plastics in creating new exposure routes, the processes involved in the release of trace elements from plastics, and the transport of plastics through environmental compartments. Trace elements inherent in plastics, due to addition during manufacture for formation or functional properties, are typically present at higher concentra?tions than those that are acquired from the environment, and consequently are likely to have greater impacts. Trace elements are continuously released into environmental matrices from plastics but may be released at higher concentrations when exposed to rapid changes in environmental conditions (pH, ionic strength, redox potential, salinity, UV levels). Plastics potentially provide additional exposure routes for organisms to trace elements. For example, exposure to trace elements may occur when organisms ingest plastics, use them for shelter and nest building or as a surface to attach onto. Further research to improve our understanding of this complex contaminant should focus on environmentally relevant studies on trace element release and their effects.