Plastic pollution isn’t just fouling the world’s oceans. It is also in the air we breathe, traveling on the wind and drifting down from the skies, according to a new study. More than 1,000 tons of tiny fragments rain down each year on national parks and wilderness areas in the American West alone, equivalent to between 123 million and 300 million plastic bottles worth.
“There’s no nook or cranny on the surface of the earth that won’t have microplastics,” said Janice Brahney, a Utah State University scientist who is lead author on the new study. “It’s really unnerving to think about it.”
While the troublesome presence of plastics in landfills, in the oceans and in freshwater environments like the Great Lakes is well known, research into airborne particles is more recent. Previous papers have described finding airborne microplastics in, among other places, Europe, China and in the Arctic.
The new paper, published Thursday in the journal Science, reports finding plastic in remote parts of the United States; the researchers collected samples from 11 national parks and wilderness areas.
They found tiny bits of plastic in 98 percent of the 339 samples they collected; plastics accounted for 4 percent of the dust particles that were tested.
Finding so much plastic in supposedly pristine areas “was a very surprising result,” Dr. Brahney said; she and her colleagues returned to their calculations again and again, she said, assuming they were wrong. But they weren’t.
The collections were made under both dry conditions and during periods of rain and snow, which helped Dr. Brahney and co-authors, Margaret Hallerud and Eric Heim of Utah State, Maura Hahnenberger of Salt Lake Community College and Suja Sukumaran of Thermo Fisher Scientific, determine the probable origins of the particles. Larger particles came down with rain and snow, while smaller ones showed up under dry conditions.
The researchers concluded that the particles deposited in wet weather were likely to have originated from relatively near by, with the plastic bits swept into the air by storms from urban centers, and then falling again with the rain and snow. The smaller, lighter particles, they suggested, had, in contrast, been carried extremely long distances on currents high in the atmosphere and had become part of the cycles of global dust transport. The dry deposits constituted more than 75 percent of the plastic that was tested.
The microfibers the researchers collected were consistent with the kinds of textiles used in making clothing and in producing carpeting and industrial coatings, as well as outdoor gear like tents and waterproof clothing. That means “emissions from park users may contribute to the observed deposition rates, particularly in national parks with high visitation rates,” though the researchers concluded that those sources did not produce a large portion of the overall samples.
Chelsea M. Rochman, an assistant professor of ecology at the University of Toronto who co-authored an accompanying commentary to the new study, said in an interview that the paper was not the first to show microplastics in atmospheric deposition, or even the atmospheric deposition of microplastics to remote places. But she added that the researchers seemed to be the first to ask through their research, “the basic science question: why and how is this happening.”
The commentary stated that the idea of “plastic in rain” is the kind of discovery that can “strain one’s imagination.”
Dr. Brahney added that the phenomenon could contribute to environmental disruption of microbial communities and cause broader ecological damage. Humans could be at risk, as well, she said; The presence of so many fine particles in the air means “we’re breathing it, too.” The health effects of taking in plastic particles is not well known, though the sizes of the particles detected are consistent with the size of those that accumulate in lung tissue, she said.
Particulate pollution, which includes dust, soot, and other airborne threats, has been linked to heart attacks, strokes and respiratory disease; the World Health Organization estimates that small particulate pollution caused 4.2 million premature deaths worldwide in 2016.
Previous studies of workplace exposure to high levels of inhaled plastic particles linked them to lung disease and tissue damage. The concentrations of plastics in the outdoor environment are lower, but could contribute to the effects of particulates.
Stephanie Wright, a lecturer in environmental toxicology at King’s College London who has studied the impact of inhaled microplastics on health, said that in the atmosphere, “these concentrations are still trace amounts in comparison to other prominent particles” such as the black carbon found in everyday soot. “Until we have a robust understanding of our exposure, it’s difficult to infer health effects,” she said.
Joana C. Prata, a Ph.D. student in Biology and Ecology of Global Change at the University of Aveiro in Portugal who has also studied health risks of airborne plastics, said that the newly discussed airborne plastics could already be contributing to the negative health effects of pollution, and that “adverse effects of chronic exposure to low concentrations of airborne microplastics cannot be excluded.”
Dr. Rochman, the author of the commentary, said that the new research and our growing awareness of the amounts of plastic falling all around us led to the question of “What do you do with that?”
The paper provided an answer, of sorts, but not an easy one. “The consequences to ecosystems are not yet well understood but are inescapable in the immediate future. If the potential dangers posed by environmental microplastics are to be mitigated,” the authors wrote, what will be required is nothing less than “the engagement of the global community.”