Sun. Nov 29th, 2020

Millions of microplastic particles found raining down on US parks

5 min read

Plastic rain: Millions of microplastic particles are spiralling through the Earth’s atmosphere and raining down on protected wilderness areas and US national parks like the Grand Canyon

  • Over 1,000 tons of microplastic were found in US parks and wilderness  areas 
  • These plastics had entered the atmosphere and rained down on remote areas  
  • They were found in Joshua Tree, the Grand Canyon, Rocky Mountain and others 

Tiny pieces of plastic, known as microplastics, are filling the Earth’s atmosphere and have been discovered raining down on US national parks like the Grand Canyon.

Researchers from Utah State University used high-resolution equipment to discover samples of this plastic pollution that had rained down from the atmosphere. 

More than 1,000 tons of microplastics were discovered over 11 remote western US locations including protected areas – having travelled through the air like rain.

The study focused on US national parks and protected wildness areas but it is expected this type of plastic pollution could be found around the world.

Rocky Mountain National Park had the greatest amount microplastics among the national parks and wilderness areas in the study. 

Tiny pieces of plastic, known as microplastics, are filling the Earth’s atmosphere and have been discovered raining down on US national parks like the Grand Canyon

This is a microscope image of microplastics in atmospheric particulate samples. Researchers from Utah State University used high-resolution equipment to discover samples of this plastic pollution that had rained down from the atmosphere

Janice Brahney, lead researcher from Utah State University, identified plastic and polymers’ collected over 14 months in 11 national parks and wildness areas. 

‘We were shocked at the estimated deposition rates and kept trying to figure out where our calculations went wrong,’ Brahney said. 

‘We then confirmed through 32 different particle scans that roughly 4% of the atmospheric particles analyzed from these locations were synthetic polymers’ 

In 2017 the world produced 348 million tons of plastic and its assumed this figure has only increased year on year since then, researchers say. 

Plastic is highly resilient and lasts a long time before breaking down – something that makes them useful in every day life.

The world produced 348 million metric tons of plastic in 2017 and global production shows no sign of slowing down. Pictured here, Rocky Mountain National Park, which had the greatest amount microplastics among the national parks and wilderness areas in the study

However, these same properties lead to progressive fragmentation instead of degradation in the environment and they remain as tiny particles.

These ‘microplastics’ are known to accumulate in wastewaters, rivers, and oceans – this research shows that they also accumulate in the atmosphere.

‘Several studies have attempted to quantify the global plastic cycle but were unaware of the atmospheric limb,’ Brahney said. 

‘Our data show the plastic cycle is reminiscent of the global water cycle, having atmospheric, oceanic, and terrestrial lifetimes.’

For the study the team looked at the source and life history of wet and dry microplastic deposits found in these parks.

Cities and large population areas were the initial source of plastics associated with the wet plastics – they also came from plastics in the surface water and soils. 

In contrast, dry deposits of plastics showed that they’d come from further away and were linked with atmospheric patterns – they rained down on the ground. 

This suggests the particles of plastic were small enough that they could travel across whole continents to reach their wilderness destinations. 

Most of the plastics deposited in both wet and dry samples were microfibers sourced from both clothing and industrial materials. 

About 30 per cent of the microplastics were brightly coloured microbeads that came from industrial paints and coatings.

Other particles were fragments of larger pieces of plastic, the team discovered.

Emerging research pinpoints atmospheric deposition as a mode of microplastic transfer to the western United States. Mapping microplastic pools (water, land, organisms) and fluxes (arrows) will guide the process the plastics go through in the ecosystem cycle

‘This result, combined with the size distribution of identified plastics, and the relationship to global-scale climate patterns, suggest that plastic emission sources have extended well beyond our population centers and, through their longevity, spiral through the Earth system,’ the authors wrote. 

This study shows the source, transport and fate of plastics on the Earth surface and how they contaminate places thousands of miles from where they originate.

‘Examination of weekly wet and monthly dry samples from 11 sites allowed the authors to estimate that more than 1000 tons of microplastics are deposited onto protected lands in the western U.S. each year,’ the team found.

The team say this is equivalent to more than 123 million plastic water bottles.  

Discovering surprising amounts of microplastics was an unintended result of Brahney doing a pilot study on a new type of field equipment.

‘I designed the samplers and was running a pilot study when I found the plastics,’ Brahney said. 

USU Assistant Professor Janice Brahney has discovered that “microplastics,” besides being known to accumulate in wastewaters, rivers, and ultimately the worlds’ oceans, also accumulate in the atmosphere

‘It was a wonderfully serendipitous moment of finding something amazing and having just the right people at the right time contribute their skills and knowledge to aspects of the project that were not my expertise.’ 

The ubiquity of microplastics in the atmosphere has unknown consequences for health but size ranges found in these parks were well within that which accumulate in lung tissue. 

The ongoing deposit of plastic in wilderness areas and national parks has the potential to influence these ecosystems, the team say. 

‘This ubiquity of microplastics in the atmosphere and the subsequent deposition to remote terrestrial and aquatic environments raise widespread ecological and societal concerns,’ Brahney said. 

‘Identifying the key mechanisms of plastic emission to the atmosphere is a first step in developing global-scale solutions.’ 


Urban flooding is causing microplastics to be flushed into our oceans even faster than thought, according to scientists looking at pollution in rivers.

Waterways in Greater Manchester are now so heavily contaminated by microplastics that particles are found in every sample – including even the smallest streams.

This pollution is a major contributor to contamination in the oceans, researchers found as part of the first detailed catchment-wide study anywhere in the world.

This debris – including microbeads and microfibres – are toxic to ecosystems.

Scientists tested 40 sites around Manchester and found every waterway contained these small toxic particles.

Microplastics are very small pieces of plastic debris including microbeads, microfibres and plastic fragments.

It has long been known they enter river systems from multiple sources including industrial effluent, storm water drains and domestic wastewater.

However, although around 90 per cent of microplastic contamination in the oceans is thought to originate from land, not much is known about their movements.

Most rivers examined had around 517,000 plastic particles per square metre, according to researchers from the University of Manchester who carried out the detailed study.

Following a period of major flooding, the researchers re-sampled at all of the sites.

They found levels of contamination had fallen at the majority of them, and the flooding had removed about 70 per cent of the microplastics stored on the river beds.

This demonstrates that flood events can transfer large quantities of microplastics from urban river to the oceans.

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