Project:
Plastic Extraction from Dryer Lint (PEDL): A low-tech, mass-based approach to quantify plastic microfibers in complex dryer lint

Authors:
James Farnan, MC Cicenia, Troy Langknecht, Sarah M. Davis, Dounia El Khatib, Robert M. Burgess, Kay T. Ho

QAPP:
J-ACESD-0034382-QP-1-0

Abstract:
Clothes laundering is considered a significant source of environmental microfibers (MFs). Most research has focused on MF releases to water during clothes laundering despite recent studies demonstrating that more MF production occurs during tumble drying. Studies that have focused on dryer emissions have typically used garments of a single material, e.g., pure polyester. Real dryer lint is more likely to exist as a complex matrix of animal (fur, hair, wool), cellulosic (cotton, rayon, lyocell), and synthetic (polyester, acrylic, nylon) materials. This study describes a low-tech method to isolate plastic MFs from real dryer lint samples, which is needed to characterize microplastics from this source. The proposed method involves an initial 24-hour digestion in 18 M H2SO4 sulfuric acid, followed by a 24-hour digestion in 7.5% bleach. After each digestion step, the digestates are filtered over 30 µm PCTE filters. The mass accumulated after the bleach digestion represents the mass of synthetic MFs in the original sample. The proposed method effectively removes >93% of cellulosic fibers and >95% of animal-based fibers while leaving plastic MFs relatively unaffected. The 9M H2SO4 did dissolve nylon fibers, which are common in textiles and likely to be present in dryer lint. However, nylon fibers account for a relatively small proportion of synthetic fiber production compared to polyester and are not expected to significantly impact the mass-based quantification. Recoveries of spiked MFs were >90%, demonstrating that this method does not result in substantial losses during the two filtration steps. Finally, Raman spectroscopy confirmed natural (e.g., cellulosic and animal)  MFs present in real lint samples were effectively removed during the digestion, comprising 1% of the digested lint sample compared to 35% in undigested lint samples. Conversely, synthetic MF accounted for >85% of the digested lint sample compared to 30% in undigested samples. The PEDL method will be useful in future investigations quantifying MF releases from domestic dryer lints to the environment.

Description:
The data contained in this .csv was used in validation studies outlined in the "Method Validation" and "Statistical Analyses" sections of the manuscript. The data were used to generate Figure 4, and Tables S3, S4, and S5.


Glossary:

sample: the sample identification, with form "treatment""replicate" (i.e., digest2 = digested sample, replicate 2; undig1 = digested sample replicate 1). Naming was made more straightforward in paper text, so digest2, digest3, digest5 are the same as digest1, digest2, and digest3, respectively.

slide_label: the label of the glass slide to which the fibers were attached

tape_num: the tape identification on the glass slide (up to five pieces of tape were put on each slide)

particle_num: the fiber number indicated on the tape

color: the color class assigned to each particle as observed under a stereomicroscope

laser_power: the laser power used to collect the spectra

hit: the library hit for the particle

library: the library from which the hit was pulled

hqi: hit quality index. hqi<0.6 were marked as unknown

notes: comments regarding the analysis

class: assigned class for binning