This microscope image shows plastic materials in rainwater samples collected near 21st and Broadway in Denver. The particles, naked to the human eye, are seen here at 40X magnification.

(USGS)

At a Glance

The research team wasn't surprised to find plastics in the rainwater samples in the cities.They were shocked, however, to find microplastics at higher altitudes in remote, pristine locations.Microplastics have been found in animals, drinking water, the deepest trenches of the oceans and the coldest reaches of the Arctic.

A team of researchers studying the nitrogen content of Rocky Mountain rainwater were shocked to find that collected water samples from high up on the mountains were teeming with microplastics.

"I thought maybe I should look at (the samples) under a microscope. And when I did, I was a little shocked by the amount of plastic that I saw in them … ," lead author Gregory Wetherbee, a research chemist with the U.S. Geological Survey, told CPR News.

Wetherbee noted that microplastics, which are less than 5 millimeters long, were the "furthest thing from my mind when we first started this project."

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The team used rainwater collection sites throughout Colorado, from Arvada, a Denver suburb, to sites at altitudes of 10,000 feet in Rocky Mountain National Park.

Wetherbee said the team wasn't surprised to find plastics in the rainwater samples in the cities, but they were shocked to find them at higher altitudes in remote, pristine locations.

"That made me realize that what we had here was something that was quite significant because the question is how do those plastics get into that remote area?" Wetherbee said.

The ultimate conclusion made by the researchers, and the title of their research paper by the USGS: "It is Raining Plastics."

The findings were similar to another study conducted recently in France, where researchers in a remote area of the Pyrenees.

Every day, an average of fall on the square meter collectors at a remote weather station in the mountains, according to the study published in Nature Geoscience.

Both studies suggest that microplastics, which have been found in animals, in , in the and in the , can also be carried long distances through the air.

The USGS team noted that it's unclear how microplastics have accumulated and assimilated into the environment, but the findings are an important wake-up call.

"I think the most important result that we can share with the American public is that there’s ," Wetherbee told the Guardian. "It’s in the rain, it’s in the snow. It’s a part of our environment now."