UCLA

This study examined the emission and physicochemical properties of microplastics and nanoplastics (MPs/NPs) generated during shredding, which is regularly used in mechanical recycling. Waste and new polyethylene terephthalate, polypropylene, and high-density polyethylene were investigated herein for a total of six categories. This study found that particle number concentrations in both submicron and micron sizes of respirable particles were significantly higher during periods of shredding plastics compared to pre- and post-shredding background concentrations. Maximum concentrations of particles within 10 to 420 nm, across all six categories, ranged from 22,000- to 1,300,000-particles/cm3. Maximum concentrations of particles within 0.3 to 10 μm, across all six categories, ranged from 24- to 2,000-particles/cm3. Waste plastics consistently generated higher emissions than their new counterparts, which is attributed to the labels, adhesives, and increased additives incorporated into the waste plastic. Morphology varied drastically between particles and an elemental composition analysis found that the samples consisted primarily of C and O, representing the polymer material, as well as Na, Mg, Al, Si, Cu, Cl, K, Ca, Ti, Fe, Rb, and Br. The shredding of plastic has the potential to expose workers to elevated concentrations of airborne MPs/NPs, especially those between 10 to 100 nm.