Plastics, including microplastics (MPs) and nanoplastics (NPs), along with their associated chemicals, are being found in virtually every environmental compartment and location sampled to date, and their abundance is increasing annually. (1) In response, numerous jurisdictions and the global community are taking steps to stem ubiquitous plastic pollution. (2) These initiatives necessarily rely on sound data from which sources, temporal and geographic trends in abundance, and effects can be confidently discerned. However, plastics pose unique challenges relative to other forms of chemical pollution. Environmental plastics are comprised of a complex mixture of different polymers, sizes, shapes, surface functionalities, additive compositions, and degrees of weathering. (3) This complexity must be adequately captured to tackle issues ranging from source identification to understanding food web transfer and toxicity. However, this complexity defies reliance on existing methods of sampling and characterization that for other pollutants took decades to develop and validate. As such, there is a pressing need for well-validated methods that underpin building baseline environmental data and protocols for evaluating impacts. In response to this challenge, the complex and multifaceted topic of plastics pollution attracts scientists from diverse disciplines, ranging from analytical chemists to environmental scientists to human toxicologists and eco-toxicologists (to name a few).