Uniform Size Classification and Concentration Unit Terminology for Microplastics

Description

Plastic trash and its breakdown products are found in many terrestrial and aquatic habitats including fresh, estuarine, and marine waters. Plastics constitute a complex and diverse group of substances that vary in size, shape, color, composition, source and age, along with other physical or chemical factors. The purpose of this document is to describe and recommend a uniform size classification and concentration unit terminology for plastics and apply it to the parallel effort to develop an environmental risk assessment (ERA) framework and eventual monitoring plan for environmental plastics in the tidal Potomac River. It is understood that classification of plastics is very complex and continuously evolving, and reconsideration of terminology will be necessary as the science advances. Creating bounds for size classifications is expected to be a useful tool for determining which size of plastics are most likely to cause an adverse physiological responses at different levels of biological organization. A systematic nomenclature is not meant to exclude or draw conclusions about smaller plastic particles that were not quantified in a particular study; it is only meant as a tool to classify and compare studies when appropriate data exist.