Microplastics catch a ride in the atmosphere

The first study to model microplastic transport in the atmosphere suggests that decades worth of legacy plastic pollution is cycling around the planet. The study suggests this movement of microplastics between land and sea via the atmosphere explains the presence of microplastics in remote places (Proc. Natl. Acad. Sci. U.S.A. 2021, DOI: 10.1073/pnas.2020719118).

Study leader Janice Brahney, a Utah State University biogeochemist, drew on her group’s database detailing microplastics deposited in remote areas across the western US. Cornell University atmospheric chemist Natalie Mahowald used a computer model to predict where those plastics might have come from. The team estimates that 84% of microplastic in the study region comes from roads. These particles can be in dust thrown up by cars or can be emitted directly from tire and brake wear and tear. About 5% of plastic in the database comes from agricultural dust.

The oceans are also a major source. Breaking waves and bursting bubbles propel microplastics into the air, accounting for about 11% of microplastics in the study. And there is a net atmospheric transport of this legacy plastic pollution from the oceans to land. Brahney said this finding was somewhat surprising but makes sense, given that plastic trash has been accumulating in marine environments for about 70 years.

“Plastic is spiraling through our environment,” Brahney says. She and Mahowald now hope to test their conclusions using data about microplastics deposited elsewhere in the world, though such data are currently scant.