The importance of contamination control in airborne fibers and microplastic sampling: Experiences from indoor and outdoor air sampling in Aveiro, Portugal.

Airborne microplastics and microfibers are released from daily materials, contaminating both indoor and outdoor air. Sampling in Aveiro, Portugal, revealed concentrations of 6 fibers m-3, with more synthetic fibers found in outdoor than indoor (8.5% vs. 4.1%, n = 6), with variations in fiber characteristics between sampling periods. Suspected microplastics (<10 μm) also followed this trend (12 vs. 5 particles m-3). Synthetic fibers presented peculiar characteristics, with larger median sizes of 513 μm and 90% of lighter colors. Nonetheless, numerous fibers and suspected microplastics were found in field blanks, possibly from sampling contamination, reducing the reliability of results. Few previous works have reported field blanks so far, raising concerns about the quality of their results as well. Thus, quality assurance measures should be more strictly applied when working with airborne fibers and microplastics, while more research should focus on the factors involved in the variation of concentrations and characteristics of airborne fibers.