While a team of researchers from the US Geological Survey (USGS) investigated rainwater samples for nitrogen pollution, they found something they did not expect – plastic.

In a recent report, aptly titled "It's Raining Plastic," the team said plastics were identified in over 90 percent of the rainwater samples they took at eight different locations, most of which are between Denver and Boulder, Colorado.

Although it would not be surprising for microplastics to contaminate most sample sites, some of these sites are removed. One of them, called CO98, is located in the Rocky Mountains at 3,159 meters altitude.

Not an easy place to leave plastic.

"Samples from urban areas have seen more plastic fibers than from remote mountain areas," the team said in the report.

"The frequent observation of plastic fibers in washout samples from the remote CO98 site at Loch Vale in Rocky Mountain National Park suggests, however, that the deposition of plastic in humid environments is ubiquitous, not just an urban condition."

The team mainly found plastic strands – they look suspiciously like microfibers made of synthetic materials, such as many items of clothing. There were also a number of colors – the most common being blue, but also red, silver, purple and green were found.

Rainwater Plastic Rockies(Wetherbee et al., Open File Report, US Geological Survey, 2019)

The plastic parts are small – visible only at least 20x magnification – but that does not mean that this is not important.

People consume at least 70,000 microplastic particles per year (probably much more), and our oceans are currently exposed to millions of tons of material.

"I think the most important result we can share with the American public is that there is more plastic than you think," said one of the researchers and USGS research scholar Gregory Wetherbee The guard,

"It's in the rain, it's in the snow, it's now part of our environment."

Rainwater Plastic Rockies Monster(Wetherbee et al., Open File Report, US Geological Survey, 2019)

This is not the first paper dealing with microplastic that occurs in unexpected environments. An article published in Nature's geosciences Earlier this year, microplastics found in the French Pyrenees, estimating that microplastic could travel up to 95 kilometers (60 miles) through the atmosphere.

Unlike in this study, the researchers in this USGS report were unable to figure out how or why the plastic got into these areas – after all, they tried to study nitrogen pollution.

"This study was not designed to collect and analyze samples for plastic particles, and the results are unexpected and useful," explains the team.

"Plastics are raining and better methods of sampling, identifying and quantifying plastic deposits and assessing potential environmental impacts are needed."

The report was published by USGS and can be found here.