Release of Micro- and Nanosized Particles from Plastic Articles during Mechanical Dishwashing

Dishwashers are a potential source of plastics into wastewater, which can then end up in the environment through effluents and biosolids. This study, for the first time, determined the release of plastic particles from the mechanical dishwashing of plastic containers and utensils. The selected PP, PE, PS, PET, and nylon-6 articles were mechanically washed using a domestic dishwasher, and the wastewater was analyzed. Particles in samples were characterized for morphology and elemental composition by SEM, particle size by FlowSync, and plastic mass concentration by Pyr-GCMS. Our study demonstrated that micro- and nanoparticles are released from the mechanical dishwashing of commonly used everyday plastic articles, with an approximate release load of up to ∼920,000 particles per cycle (full load), equating to ∼33 million particles per household per year. The particle size ranges released were different between each plastic article, with PE, PP, and PS plastic articles releasing greater amounts in the larger particle size range (>2.7 μm), whereas PET and nylon-6, released relatively consistent amounts across the 4 size ranges (0.01–0.3, 0.3–1, 1–2.7, and >2.7 μm). Our estimations suggest that if the average mechanical dishwasher wash contains one article of 1000 cm2 (the size of an average 1 L container) in area for each of the 5 plastics detected (∑5 plastics), then the release of particles from dishwashers would equate to less than 6 mg/year/person or 43 particles/cm2 washed, globally. This study serves as a first look to understand the release of micro- and nanoparticles from plastic articles during dishwasher use and suggests that the source contribution from dishwashers is relatively low.