Scientists have detected microplastics—small pieces of plastic measuring less than 5 millimeters—in some of the most untouched parts of our planet, including the Mariana Trench, the snow atop Mt. Everest, and the mountain clouds in China and Japan. These tiny plastics have also been found in human brains, sea turtles, and plant roots. Recent studies indicate that microplastics present in the atmosphere may even be influencing our weather and climate.
Scientists have detected microplastics—small pieces of plastic measuring less than 5 millimeters—in some of the most untouched parts of our planet, including the Mariana Trench, the snow atop Mt. Everest, and the mountain clouds in China and Japan. These tiny plastics have also been found in human brains, sea turtles, and plant roots. Recent studies indicate that microplastics in the atmosphere may even be influencing our weather and climate.
A study shared in the journal Environmental Science and Technology: Air revealed that microplastics serve as ice nucleating particles, tiny aerosols that help create ice crystals in clouds.
This suggests that microplastics may alter precipitation patterns, affect weather predictions, influence climate models, and even impact aviation safety by altering the way clouds form ice, as explained by Miriam Freedman, a chemistry professor at Penn State and one of the lead authors of the research.
“Over the last twenty years, researchers studying microplastics have found them almost everywhere. This discovery adds another piece to the puzzle,” Freedman remarked. “It’s crucial we enhance our understanding of how they interact with the climate system, as our findings indicate that microplastics can initiate cloud formation.”
In laboratory experiments, the team investigated how four types of microplastics—low-density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)—behaved as freezing agents. They introduced these plastics into small water droplets and gradually cooled them to see how they influenced ice development.
The researchers observed that the freezing point for droplets containing microplastics was around 5-10 degrees Celsius higher than that of droplets without any microplastics. Typically, an intact atmospheric droplet freezes at approximately -38 degrees Celsius, according to Heidi Busse, a graduate student at Penn State and the study’s main author. Any imperfection in the droplet—be it dust, bacteria, or microplastics—can provide a nucleus for ice to form. Even a tiny structure can prompt the droplet to freeze at warmer temperatures.
The implications of this finding for weather and climate are still being explored, according to Freedman, who speculated that microplastics may already be having observable effects. She mentioned that mixed-phase clouds—like fluffy cumulus, wide stratus, and dark nimbus—contain both liquid water and ice. These cloud types are ubiquitous in our atmosphere, including those characteristic “anvil” shapes formed during thunderstorms.
Generally, clouds help cool the Earth by reflecting sunlight, but certain clouds at specific altitudes can create a warming effect by trapping heat emitted from the Earth’s surface. Freedman pointed out that the balance of liquid water and ice within these clouds plays a critical role in determining their overall cooling or warming impact. If microplastics are indeed influencing mixed-phase cloud formation, they likely affect the climate as well, although accurately modeling their full impact is highly complex.
The researchers also discovered that environmental aging—natural photochemical reactions that aerosol particles undergo over time—can significantly alter how these particles interact with atmospheric gases and vapors. By simulating aging, the team exposed microplastics to light, ozone, and acids to test whether these conditions modified their ice-forming capabilities.
The study revealed that all plastics evaluated were capable of forming ice, although aging generally diminished the ice formation ability of LDPE, PP, and PET. In contrast, the ice-forming capacity of PVC increased due to slight changes on its surface during aging.
The next phase of research will focus on a variety of common plastic additives, like plasticizers, to better understand how everyday plastics might influence the Earth’s atmosphere.
Additional authors of the study include Devaka Ariyasena and Jessica Orris, fellow graduate students from Penn State. This research received support from the U.S. National Science Foundation, facilitated by the Materials Characterization Lab at Penn State.
