Plastic-on-Plastic: Underestimated Contamination Risks in Micro- and Nanoplastic Research

Micro- and nanoplastics (MNPs) are detected in nearly every environmental and biological sample, yet most experiments evaluating their presence and effects take place in laboratories already contaminated with MNPs. Pipette tips, plastic tubes, culture plates, filters, water systems and indoor air all shed MNPs, and, as a result, the lab itself becomes an unaccounted exposure source. At low environmentally relevant doses, this hidden background can reach or even exceed the intended experimental concentrations. This can bias exposure estimates and experimental readouts. This review synthesizes evidence on laboratory plastic contamination in MNP research. Here, we outline the major sources, airborne fibres, purified water and storage containers, plastic consumables and media preparation. We then use these data to construct scenarios of cumulative contamination for typical biological and environmental workflows, highlighting conditions under which laboratory-derived particles can approach or exceed nominal experimental doses. Finally, we analyse how this background inflates and underestimates experimental doses, generates unintended mixed-polymer exposures, and interferes with particle identification and dose–response analysis.