In 2023, microplastics were found in the clouds over Mount Fuji, Japan’s highest peak. (Shutterstock)
First, a bit on how they get there. Spinning tyres are a major source, sending showers of the tiny flakes into the air (from the synthetic fibres that give tyres added traction).
Synthetic clothes, when processed, and when washed and dried, release microplastics and nanoplastics too.
For years, until countries began to ban them in 2015, microbeads were added to cosmetics, detergents and a range of chemicals and pharmaceuticals. Sea turbulence sprays these into the air. They are small and light, and drift upwards easily (they can also be inhaled).
In 2023, scientists from Waseda University found microplastics in the clouds above Mount Fuji, Japan’s highest mountain.
Scientists are now finding that the airborne flakes could impact weather.
The tiny manmade pollutants act as ice-nucleating particles, with potential impacts on rainfall and storm patterns, researchers from Pennsylvania State University demonstrated, in a paper published in the journal Environmental Science and Technology: Air, in November.
The researchers studied the freezing activity of four different types of microplastics — PVC (polyvinyl chloride), PET (polyethylene terephthalate), LDPE (low-density polyethylene) and PP (polypropylene) — by suspending these particles in small droplets of water, and slowly cooling them.
They found that the droplets with microplastics froze at temperatures that were 5 to 10 degrees higher.
Any kind of particle, from dust to pollen, can aid the formation of ice. This is partly how natural events such as dust storms and volcanic eruptions alter weather. But microplastics don’t belong in the air; and they’re now in it all the time. More or less everywhere.
The result could be delayed rainfall and large dumps of rain when it does occur.
“In a polluted environment with many aerosol particles, the available moisture becomes distributed among more nuclei, forming smaller droplets. This delays rainfall, because droplets only rain once they become large enough,” says Miriam Freedman, a professor of chemistry at Pennsylvania State, who is also affiliated with the university’s department of meteorology and atmospheric science.
With more aerosols in the air, “you collect more total water in the cloud before the droplets are large enough to fall and, as a result, you get heavier rainfall when it comes,” she adds.
This new factor could hamper climate modelling, since research into the effects of microplastics on weather is still in its early stages — and we are only beginning to estimate the volume of microplastics and nanoplastics in the air as well.
Studies have shown that extents can range from 0.01 particles per cubic metre over the western Pacific Ocean, to several thousand particles per cubic metre in polluted cities such as London and Beijing.
Though there are currently far fewer microplastics than other manmade aerosols in the air, the plastic flakes are typically lighter and can therefore travel farther, and stay aloft longer.
“It’s why their impact on climate has become a trending topic in the atmospheric community,” Freedman says.
E-Paper
