LAUSR

R identifying the ubiquitous presence of microplastics in the environment has accelerated further research to investigate their environmental behavior and fate. Whether a primary microplastic (manufactured microbeads, fibers, pellets) or secondary microplastic (larger plastic debris breaking into smaller fragments), their fate in the environment is influenced significantly by the extent and nature of chemical and physical alteration under environmental conditions. Investigating and quantifying the nature and extent of this chemical and physical change is fundamental to more accurately describe the ultimate environmental fate and behavior of microplastics in the environment. However, this is an area that is often overlooked in microplastics research, or it is approached in a nonstandardized way. For example, a Web of Science search of the term “microplastic*” in 2019 returned 291 papers from three journals publishing the highest number of microplastics papers. Of these 291 papers, 77 described experiments performed in the laboratory with microplastics produced, purchased, or collected by the authors, and only five papers (approximately 6.5%) compared degraded and nondegraded samples to assess the effect of weathering on experimental outcomes. Degradation, weathering, and aging are used interchangeably to describe the transformation of flexible, hydrophobic, and transparent plastics into brittle, hydrophilic, and opaque plastics (Figure 1). The degree to which weathering occurs, affecting plastic properties, is related to the chemistry of the plastic and the intensity, time, and manner of exposure to environmental agents. Different environments include air, water, soil, inside biological systems, and sunlight as key contributors to weathering and breakdown, leading to conformational changes in primary and secondary microplastics. Different microplastic properties undergo modifications in different environmental situations, and can include the following. Leaching of Plastic Additives. Plastic polymers have chemical additives included to enhance their properties, for example, to last longer, to burn slowly, to be more flexible, or to degrade slower or faster. Certain additives are of environmental concern. The additives are slowly released by the plastics during their useful life and this continues once discarded to the environment. The chemicals diffuse through