Tiny airborne plastic particles are spreading to all corners of the planet, penetrating deep into the human body and causing concern among researchers about this relatively new topic.
Studies are shedding light on the origins, transport mechanisms and effects of these pollutant microplastics, which are too small to be seen with the naked eye.
They have been found in the skies over Mount Fuji, in European rain, in Arctic ice, and within the human body. These byproducts of human activity can also promote extreme weather conditions.
“Marine microplastic pollution has attracted so much attention that the ocean has been considered the final destination for microplastics, but recent studies indicate that airborne plastic pollution is spreading at an alarming rate,” said Hiroshi Okochi, Waseda University professor of environmental chemistry.
Okochi leads a research team that has been studying airborne microplastics since 2017 and was the first to show that pollutants make their way into cloud water.
According to studies on how plastic waste is harming marine life and the marine environment, plastic waste flowing into the ocean turns into “marine microplastics”, which have a particle size of 5 millimeters or less.
In contrast, few studies are available on “airborne microplastics”, most of which measure less than 2.5 micrometres (0.0025 millimetres).
A study published in 2016 found plastic in the form of fibers in rainwater in Paris, which showed that plastic particles were floating in the air.
In 2023 Okouchi’s team published a study showing that the water in the clouds covering the top of Mount Fuji contained 6.7 pieces of microplastics per liter.
Airborne microplastics travel in different ways at different altitudes.
In the free troposphere, an atmospheric layer extending from 2,000 to 2,500 meters in height, substances are transported intercontinentally over long distances by the prevailing westerly winds and other air currents. They are rarely influenced by things on the ground.
Okochi’s team said the microplastic particles found atop 3,776-meter-high Mount Fuji, where clouds can form, were transported far from their sources.
Possible cause of torrential rain
According to one theory, when large-scale atmospheric depressions form and generate upward air currents, land-based and marine microplastics are swirled upward by wind and sea spray and carried high into the sky.
Once in the free troposphere, strong winds push microplastics to higher levels and at enormous speeds, polluting the layer.
A team of scientists from Germany and Switzerland reported that they found more than 10,000 pieces of microplastic per liter of ice in the Arctic. He said such microplastics can travel long distances in the air and accumulate with snow.
Microplastics can also induce cloud formation.
Clouds form naturally when dust acts as a nucleus for the condensation of water vapor. Specific elements of plastic products, such as polyethylene and polypropylene, naturally repel water.
Microplastics, however, change chemical structure and gain hydrophilicity, or attraction to water, when disintegrated by ultraviolet rays.
Okochi said this likely facilitated cloud formation through vapor condensation.
Some experts say microplastics could cause sudden torrential rains and other extreme weather events.
Studies have also found that microplastics, when broken down by ultraviolet rays, emit greenhouse gases such as methane and carbon dioxide.
plastic entering the lungs
Although plastic has been found in various areas of the human body, it is not yet known what effects airborne substances have on health.
Airborne microplastic particles 1 micrometer (0.001 mm) or less in size are thought to be able to reach the alveoli of the lungs.
A study conducted in Britain said that microplastics were found in 11 out of 13 lung tissue samples from patients who had undergone lung surgery. The highest levels were found in the lowest regions of the lungs.
A human being breathes more than 20,000 times a day, which is 600 million to 700 million times in a lifetime.
There is no standard way to measure airborne microplastics, so the estimated amounts ingested by humans vary wildly from one research article to another.
Okochi said he hopes to develop a unified method to measure the size, type, shape and concentrations of airborne plastics so that researchers around the world can use it in their observations.
“We essentially inhale airborne microplastics without knowing because the pollution they are creating is invisible,” Okochi said. “There is clearly very little information about their potential impact on health and the environment, which has just begun to be discussed. There should be more fact-finding studies on this matter.”
hope on forest division
Airborne microplastics come from a variety of sources, including road dust, tire friction, artificial turf, and clothing.
Effective measures to reduce risk include avoiding the use of synthetic fiber clothing and washing clothes in mesh laundry bags to prevent clothes from rubbing together.
In the bigger picture, society can consider whether some plastic products are really necessary in the immediate environment or whether they can be replaced with non-plastic materials.
Absorption by forests is gaining attention as a promising solution for airborne plastics that are too small to appear.
A group of researchers including Okouchi and scientists from Japan Women’s University discovered that “Konara” absorbs airborne plastic through “epicuticular wax”, a coating layer on the surface of the oak leaf that protects the tissue from ultraviolet rays and external enemies.
The forests of Konara in Japan can absorb an estimated 420 trillion pieces of airborne microplastics a year, Okouchi said.
His team is now studying the use of fast-growing Paulownia trees to fight airborne microplastics.
There is hope that this tree variety can solve other environmental problems. Trees absorb large amounts of carbon dioxide and can be used to absorb radioactive materials in the soil in Fukushima Prefecture, the site of the 2011 nuclear disaster.
“Planting roadside trees can help reduce human-induced breathing problems,” Okochi said. “We hope to further extend the potential of this new emissions reduction measure by using fast-growing Paulownia trees to reduce the risk of human exposure.”
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