Critical Aspects of Sustainability (CAS): Micro- and Nanoplastics (MNP)


This Dear Colleague Letter (DCL) encourages the submission of proposals that tackle some of the fundamental scientific questions underlying micro- and nanoplastic characterization, behavior, and reactivity in the environment (including animal and human health), as well as their elimination from land and water systems.

In the environment, plastics eventually break down as a result of mechanical weathering and/or photodegradation, forming micro- and nanoplastics - plastic fragments <5 millimeters and <100 nanometers, respectively, in diameter. Microplastics have also been manufactured for use in personal care products, though this usage was banned by the United States in 2015. Current water treatment cannot completely remove micro- and nanoplastics. Micro- and nanoplastics have been measured in polar sea ice as well as in fresh and saltwater fish.1

The degradation pathways of micro- and nanoplastics through photochemistry, ingestion, or microbial interactions are incompletely understood. Additionally, micro- and nanoplastics may adsorb and concentrate hazardous pollutants or acquire coatings of biofilms that affect their fate. Nanosized plastic particles may have very different properties than the larger microplastic particles in terms of environmental fate, aggregation, and sedimentation, and thus individual and ensemble characterization may be needed.2 Nanoplastics may cross the blood-brain and gut-blood barrier and present unique health concerns.3 Due to their small size and the complex sampling environments, reproducible analytical techniques are needed to understand the structure-property relationships of micro- and nanoplastic particles as well as their behavior in their environment.

Sustainable solutions to the plastic waste problem require creative approaches from many scientific disciplines, to reduce the burden and harmful effects of micro- and nanoplastics and ensure our ability to track their fate in the environment.

Several Directorates/Offices/Divisions participate in this DCL and welcome the submission of proposals on this topic, though each division will only accept proposals of a certain type, as described in the corresponding sections below. All questions regarding proposals should be addressed to the cognizant Program Officers to whom submission is contemplated.

Proposals involving international collaboration are welcome when the collaboration enhances the proposed research. The NSF funds the U.S. side of international collaborations.

After any solicitation or NSF Proposal & Award Policies & Procedures Guide (PAPPG)4 specific requirements, titles should include the prefix "CAS-MNP: ".