Last August, scientists delivered the chilling news that microplastics suspended in the Earth's atmosphere were being deposited in remote areas of the Arctic and Europe. Now researchers report similar microplastic accumulation in iconic American protected areas including the Grand Canyon and Joshua Tree. 

Publishing their results today in Science, the researchers estimate total yearly plastics deposition over their study area to be the equivalent of 123 to 300 million discarded water bottles.

The study is the first to calculate rates of microplastic pollution from the atmosphere onto American protected areas and adds to a growing body of research suggesting that microplastics are traveling long distances in the atmosphere. Microplastic pollution can harm wildlife health, and the researchers expressed concern about potential impacts to ecosystem stability in fragile and unique protected areas of the U.S. 

Janice Brahney, an assistant professor at Utah State University and lead scientist on the new report, made the discovery while analyzing atmospheric dust—particles that get swept up into the atmosphere and then settle out again. 

Examining the dust under a microscope, she found something she did not expect. "Scrolling around these samples, I started to see all these colorful pieces," Brahney told EHN. "Nearly every single sample had plastic in it."