It’s getting harder and harder to avoid plastics.

In a study published in Environmental Chemistry Letters last month, scientists in Japan documented how they collected water from clouds at the top of both Mount Fuji and Mount Oyama to perform a first-of-its kind study on airborne microplastics in clouds. The team observed concentrations of microplastic between 6.7 and 13.9 pieces per liter of cloud water.

In two separate studies out of St. Louis, Missouri, researchers found large amounts of microplastics in the water and sediment of a cave that has been closed to humans for decades.

“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 lead author of the cloud study, Hiroshi Okochi of Waseda University, said in a statement.

(Clouds: Yale360GizmodoAl JazeeraFuturism. Cave: STLPRViceFuturism)