Microplastics have been found everywhere from the oceans’ depths to the Antarctic ice, and now new research has detected it in an alarming new location — clouds hanging atop two Japanese mountains. From a report: The clouds around Japan’s Mount Fuji and Mount Oyama contain concerning levels of the tiny plastic bits, and highlight how the pollution can be spread long distances, contaminating the planet’s crops and water via “plastic rainfall.” The plastic was so concentrated in the samples researchers collected that it is thought to be causing clouds to form while giving off greenhouse gasses.

“If the issue of ‘plastic air pollution’ is not addressed proactively, climate change and ecological risks may become a reality, causing irreversible and serious environmental damage in the future,” the study’s lead author, Hiroshi Okochi, a professor at Waseda University, said in a statement. The peer-reviewed paper was published in Environmental Chemistry Letters, and the authors believe it is the first to check clouds for microplastics. The pollution is made up of plastic particles smaller than five millimeters that are released from larger pieces of plastic during degradation. They are also intentionally added to some products, or discharged in industrial effluent. Tires are thought to be among the main sources, as are plastic beads used in personal care products. Recent research has found them to be widely accumulating across the globe — as much as 10m tons are estimated to end up in the oceans annually.