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.

An easy method for processing and identification of natural and synthetic microfibers and microplastics in indoor and outdoor air.

Microplastics and microfibers can contaminate every matrix, including in the atmosphere, thus leading to incidental inhalation. However, concentrations of airborne synthetic particle in indoor and outdoor environments are not well understood due to the complexities of sampling, sample processing and identification. This work aims at producing a simple protocol to determine the concentrations of airborne microplastics and fibers. This is accomplished by removing organic matter using hydrogen peroxide (H2O2), followed by removal of mineral matter by density separation with sodium iodide (NaI). Finally, identification of fibers into synthetic or natural under the stereomicroscope can be achieved following a diagram produced by systematically observing the most common textile fibers. This method produces a recovery rate of 94.4 % for spiked samples and has been proven suitable for environmental samples. •Fibers and microplastics in air are easier to identify after carbonaceous matter removal;•No loss of microfiber is expected from the solutions used;•Recovery rates of spiked samples is 94.4 %.