A newly published study advances our knowledge of how microplastics may age in the environment and whether they stick to other contaminants as they do so. Microplastics (MPs) are tiny plastic pieces that measure less than 5 millimeters (about 0.2 inches) in length. The study looked at the aging of MPs made of three common polymer chemicals—polyethylene, polyethylene terephthalate and polypropylene—to see if they changed as they aged and how that affected nearby contaminants.