Table 2.

Summary of studies on the release of micro- and nano-plastics from personal protective equipment, particularly face masks and wipes.

Type of PPE	Sample collection	Experimental setup	QA/QC	Filter and pore size	Quantification and characterization	Abundance	Characteristics	Reference
Medical surgical face masks, disposal medical face masks, normal disposal face masks and N95 face masks; 18 brands from China (New and used)	Masks worn by students and staffs for one day prior to the experiment	Mask + 200 mL of deionized water on a rotary shaker at 120 rpm for 24 h	1.Three replicates 2.Equipment and lab utensils were pre-washed with DI water and covered with aluminum foil 3.Cotton masks and laboratory coats, and clean gloves were worn 4.Prefiltering of water used for experiment 5.Blanks were used and particles found in them were subtracted	Millipore mixed cellulose filter; 0.8 µm	VI and Raman spectroscopy	Used masks: 183.00 ± 78.42 particles/piece New masks: 1246.62 ± 403.50 particles/piece	Fiber and fragment; PP and PET; Green, orange, blue, pink, transparent, yellow, black, grey, and purple; 100 – 500 µm dominant, with range between < 100 and > 2000 µm	Chen et al. (2021a)
Sixteen surgical three-layer masks from Italy	Purchased by GLF S.A.S (Italy)	1.Ear strip and nose bridge were removed 2.A kitchen chopper was used for mechanical solicitation 3.5 mL of each samples inspected for microplastics 4.2 mL of each samples were treated with 30% H2O2	1.Beaker was washed with Milli-Q water for 5 times 2.Polystyrene yellow-green, fluorescent microspheres (0.1–1 µm) were used as reference reagents	–	VI, and flow cytometry	0.3 ± 0.1 × 105 items m2 of fabric, overall, 2.6 ± 0.5 × 103 items per mask	PP microplastics > 100 µm: 0.08–100 µm: 7.6 ± 4.6 × 108 – 3.9 ± 1.1 × 1012 items per mask	Morgana et al. (2021)
Seven disposable surgical masks from Italy (New); Three-layer mask	Purchased online platform	1.UV light exposition by soaking in artificial seawater (ASTM D1141–98) under stirring for 10 hrs at 65ºC; 18 times	1.Infrared spectra of nose strip and three layers of masks was taken prior to the analysis	Sieve: 500 µm stainless steel Whatman nitrocellulose filter; 0.45 µm	VI, SEM, and FTIR-ATR	No. of fibers mean: 117,400 ± 42,345 (mass loss of 0.07%)	Fiber and aggregate; 25–500 µm; PP	Saliu et al. (2021)
Disposable surgical mask from China (New masks)	Purchased from drug sales office	1.New mask in 3 L of ultrapure water under stirring for 24 h 2.Pre-washed masks in detergent solution (DS) sodium dodecyl benzone sulfonate and 75% alcohol disinfectant (DI) 3.Placed at the roof for aging of masks	1.Experiments were repeated three times 2.All glass instruments were cleaned with ultrapure water and alcohol 3.Cotton clothes all throughout experiments 4.Glassware pre-cleaned with 30% ethanol solution, rinsed with ultrapure water, then heat treated at 400 °C to remove organic impurities 5.Filters were cleaned with ultrapure water	Nitrocellulose membrane; 0.45 µm	VI, SEM, and micro-FTIR	1.Without DS and DI: 116,600 items per mask (mass loss: 0.47%) 2.-With detergent: 168,800 items per mask (mass loss: 1.14%) 3.With disinfectant: 147,000 items per mask (mass loss: 0.85%) 4.Microplastics release from aged masks: 6.0 × 108 – 6.4 × 108 items per mask	< 0.5–3.8 mm; 80% < 1 mm, Fiber; PP	Shen et al. (2021)
Ecoparksg disposable masks (Canada)	Purchased from Fisher Scientific	1.Exposed to UV light (254 nm) for 1–48 h in a UV chamber 2.Outer, inner, and middle layer placed in 50 mL of water with sand (20 g) for 300 rpm and 25 ℃ for 36 h	1.Control samples wrapped in aluminum foil without UV exposure 2.Control experiments without mask in sand 3.Triplicates for each layer	–	SEM, FTIR-ATR, AFM, and in laser in-situ scattering & transmissometry analyzer	Without sand abrasion: 1.5 million microplastics per mask With sand abrasion: 16 million microplastics per mask	Fiber fragments, middle layer released greater microplastics; 10 – 250 µm; UV weathering: 30 – 100 µm	Wang et al. (2021)
New masks China	Purchased from drug stores or on-line shops, April- June 2020	Experiment I: 1.New masks in 100 mL of Milli-Q water shaken for 3 min for 10 times 2.100 µL of leachate was placed on silicon wafer pretreated by ethanol Experiment II: 1.Nasal mucus was collected after 12 h of wearing masks using saline solution (5 mL of 0.9% NaCl); exposed for 30 s and 50 mg of mucus was collected 2.Filtered through 0.45 µm and passed through a 30% H2O2 and density separation (ZnCl2) 3.Dye Pink staining 70ºC for 2 h	1.Glass bottle previously burned at 500 °C for 4 h 2.A bottle without mask was used as a control 3.Triplicates were performed each batch of masks 4.A blank wafer was used as a control 5.Three replicates were performed for each scenario 6.Saline solution was checked under a microscopy for external contamination 7.Mucus collected from persons without wearing a mask 8.Microplastics on the filter transferred to glass vial and frozen	Aluminum oxide filter; 0.22 µm	SEM, AFM, and FTIR	Abundance: 2.8 – 6.0 × 109 per mask Mucus: 2.6 ± 0.4–10.6 ± 2.3 microplastics per mucus secretion	Middle layer releases large number of irregularly shaped particles; 5 nm to 600 µm < 1 µm particles were predominant Nasal mucus contained microplastics that can be inhaled while wearing a mask; larger than 1 mm are found and the number of particles varied with higher breathing frequency	Ma et al. (2021)
Seven common masks (Five- layer N95 respirator, surgical mask, cotton mask, non-woven mask, fashion mask, and activated carbon mask) China	–	Experiment I: Masks fixed tightly on top of the suction cup of vacuum pump -Milli-Q water was used to clean the suction cup, and the ejected microplastics were transferred onto the membrane via vacuum suction Experiment II: Microplastic inhalation risk using UV radiated, washed, disinfected masks for a period of 2 – 720 h	1.A blank test, a suction test without mask, and a test that only allows air to pass through the filter membrane were conducted. 2.Designed to reflect a realistic situation of microplastics inhalation and no contamination control measures were applied.	–	VI, LDIR, and Raman	Increase in microplastics with time exposure	Fiber and spherical type particles; 600–1800 µm	Li et al. (2021)
10 Disposable Face masks of 7 brands (new); colored plain, black	Purchased from several manufacturers in China	Masks were submerged in 1.5 L deionized water under agitation for 4 h	Procedural blanks with each batch by filtering 1.5 L of deionized water	Aluminum oxide filter; 0.1 µm	VI, SEM, and FTIR	–	Fiber; PP and PA, dye eriochrome black and congo red; < 25 µm – 2.5 mm; black, blue, and pink	Sullivan et al. (2021)
Three wet wipes	–	1.Each sample was cut into 5 cm × 5 cm pieces 2.Experiment I 3.Rubbing wipes for 10 times on gloves and rinsed with 100 mL of DI water 4.Experiment II 5.Immersing wipes in water for 1 h 6.Experiment III 7.Dried wipes at oven were rubbed and followed the steps of experiment I 8.All collected samples were treated with H2O2	1.All experiments were conducted on a clean bench and stored in glass bottles 2.Petri dishes covered with aluminium foil 3.Procedural blanks with deionized water were conducted 4.Triplicates were carried out for each wipe	Anodisc filter; 0.2 µm	VI, FESEM, and FTIR	Experiment I: 180–200 p/sheet Experiment II: 693–1066 p/sheet	Polyester; Fiber, mostly cylindrical smooth shape; 93% of fibers were more than 100 µm	Lee et al. (2021)

DI: Deionized water; VI: Visual Inspection; LDIR: Laser Direct Infrared Imaging; ATR-FTIR: Attenuated Total Reflection- Fourier-transform infrared spectroscopy; FESEM: Field Emission Scanning Electron Microscopy; AFM: Atomic Force Microscopy.