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Whitening of nanoplastics through atmospheric irradiation and oxidation
Summary
Tiny colored plastic particles from products like 3D printer filaments can get into the air we breathe, and this study found that sunlight and ozone actually fade their color over several days, though how much depends on the type of plastic. This matters because these fading plastics don't just disappear; they stick around in the atmosphere and may affect climate patterns, and understanding how they break down helps scientists figure out what we're actually being exposed to as these particles linger in the air around us.
Plastic particles with dimensions in the nanometer range, called nanoplastics, have recently been detected in the atmosphere, where they have direct and indirect effects on climate through their interactions with radiation and clouds. The direct effect of colorful nanoplastics will depend on the rate and extent of their whitening, which can be expected to occur under the influence of sunlight and oxidants but remains unexplored. Here, colorful nanoplastics were generated using the heated nozzle of a 3D printer, extruding red and yellow filaments of acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG). Size distributions were measured using a scanning mobility particle sizer. Filter-collected nanoplastics were characterized in terms of absorbance and colorimetry as a function of time exposed to simulated sunlight and 50-ppb gas-phase ozone. Red and yellow nanoplastics generated from ABS under the influence of irradiation exhibited the most rapid and significant whitening, with little difference between colors in rate and extent, reaching an asymptote at about 30% of the initial absorbance after 4 d. On the other hand, these nanoplastics from ABS under the influence of oxidation exhibited the least whitening, reaching about 80%. Whitening of red and yellow nanoplastics from PETG evolved similarly upon irradiation and oxidation, reaching about 50% of the initial absorbance after 4 d of aging by either mechanism. These results demonstrate that atmospheric whitening is likely significant, dictated more by the matrix material than the colorant, with important implications on the fate and impact of colorful nanoplastics on radiative forcing.Copyright © 2025 American Association for Aerosol Research