A newcomer has recently been detected in the atmosphere: tiny “nanoplastic” particles. Like any airborne small particle, they can remain in the atmosphere for a week or more, where they have the potential to have direct effects on climate by absorbing or reflecting light, or indirect effects through changes in cloud formation or cloud properties.
Consumer plastics come in all colors, owing to additives such as dyes, pigments, and other organic or inorganic colorants. After degradation in the environment, plastic particles can be swept aloft by wind or wave breaking in the ocean. Nanoplastics can also be directly emitted by industrial processes.
How the nanoplastics hold onto their color during their atmospheric residence time determines whether their direct effect on climate is warming or cooling. While they are “colorful,” they are absorbing and therefore “warming.” But if their color fades as they are whitened through atmospheric processes, with time they would become more reflective and “cooling.”
Schematic of nanoplastic color transformations under the influence of atmospheric UV radiation or oxidation. ABS (acrylonitrile butadiene styrene) and PETG (polyethylene terephthalate glycol) plastics were used in the study. From Betz et al., Aerosol Science and Technology, 2025.
Researchers at Oklahoma State University set out to do the first experimental study of how the color of the nanoparticles is changed by irradiation and by oxidation. They made nanoplastic particles using the extruder and heated nozzle of a 3D printer, collecting the particles on a filter. The filter samples were then placed in a flow tube apparatus, where they could be exposed to radiation or to ozone. The 2B Tech Model 106-M Ozone Monitor was used to measure the ozone exposure concentration, which was at an atmospherically relevant value of 50 ppb.
The nanoparticles lost some but not all of their color, with results dependent on the type of plastic and the type of exposure. Over the 4-day exposure experiments, for the UV-irradiated ABS plastics, most of the fading happened on the first day and fading was smaller for days 2 through 4. Fading was more linear over the whole 4-day period for ABS and PETG plastics exposed to ozone, as well as for the UV-irradiated PETG plastics.
Overall, the plastic nanoparticles lost about 50% of their light-absorbing capabilities in 4 days of the experiment, with more fading owing to irradiation rather than ozone. Results depended on the type of plastic and the type of colorant in the plastic.
Nanoplastic absorbance changes (460-740 nm) under the influence of UV radiation or oxidation, as measured over four days in the experiment. Figure 5 from Betz et al., Aerosol Science and Technology, 2025.
In the real atmosphere, with residence times of one to two weeks, the findings suggest that the combined influences of irradiation and oxidation would lead to more than 50% decreases in absorptivity of nanoplastics, diminishing their warming effect. Particle size also likely makes a difference, with larger sizes such as microplastics having greater color retention. A myriad of plastics and colorants are in use worldwide. All of these factors makes it extremely difficult to incorporate the effects of plastic particulates into climate models.
With plastics seemingly ubiquitous in modern life, clearly more work is needed to understand their atmospheric, climate, and environmental effects, as well as their effects on human health.
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Whitening of Nanoplastics through Atmospheric Irradiation and Oxidation, K.L. Betz, S.M. Liyanage, M.R. Miles, J.A. Barton, S.M. Dye, and E.G. Schnitzler, Aerosol Science and Technology (2025), DOI:10.1080/02786826.2025.2478958.