Understanding Human Health Impacts Following Microplastic Exposure Necessitates Standardized Protocols

Abstract

Microplastics (MPs; 1 µm to 5 mm) are a persistent and pervasive environmental pollutant of emergent and increasing concern. Human exposure to MPs through food, water, and air has been documented and thus motivates the need for a better understanding of the biological implications of MP exposure. These impacts are dependent on the properties of MPs, including size, morphology, and chemistry, as well as the dose and route of exposure. This overview offers a perspective on the current methods used to assess the bioactivity of MPs. First, we discuss methods associated with MP bioactivity research with an emphasis on the variety of assays, exposure conditions, and reference MP particles that have been used. Next, we review the challenges presented by common instrumentation and laboratory materials, the lack of standardized reference materials, and the limited understanding of MP dosimetry. Finally, we propose solutions that can help increase the applicability and impact of future studies while reducing redundancy in the field. The excellent protocols published in this issue are intended to contribute toward standardizing the field so that the MP knowledge base grows from a reliable foundation. © 2024 Wiley Periodicals LLC.

Keywords: bioavailability; dosimetry; exposure; microplastics; reference materials.

Figure 1.. Schematic of commercial microsphere compared to environmental microplastic.

Commercial microspheres usually have varying surface charge, contaminants from the production processes, and/or surfactants and additive chemicals, which can be absent or in addition to other acquired factors from the environment that are usually found on environmental MPs, such as surface oxidation, adsorbed environmental toxins, and/or an ecocorona with microbial colonization.

Figure 2.. Example of best approaches for reference MP production.

The morphology of particle of interest for examination in toxicological studies will determine the best approach for in house production. This is not an exhaustive example of approaches for reference MP production, but stages the workflow for cryogenic milling or slicing for particles and fibers, respectively. The polymer type will determine the feedstock for each approach and size(s) of particles is dependent on feedstock.