Looking Skyward For Microplastics

Looking Skyward For Microplastics

Microplastics are a hot topic these days. Spawned by everything from plastic bags to laundered clothing, the volume of tiny particles that pollute our oceans has exploded in recent years.

What you probably didn’t know, until now, is that about 1,100 tons of the stuff are floating above the Western U.S. alone, according to new modeling published recently in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) and written about by Matt Simon for Wired. Another big surprise: Much of it isn’t coming from the big urban areas.

Modeling shows that more than 80 percent of the airborne microplastics out west are coming from the roads outside of large cities.

Here’s how that happens: When a car rolls down a road, its tires shed rubber, as well as synthetic rubbers and a slew of other chemical additives, which are technically microplastics. While cities generate a massive amount of microplastics through traffic, it doesn’t seem to get high into the atmosphere. Researchers believe that’s because buildings block the wind from propelling those particles and people drive slower in metro areas, so there’s less agitation of the tire particles that are shed during commutes. Outside of large cities, the higher speeds and more open space for wind is better for propelling microplastics into the atmosphere.

The model assumes that microplastic particles, which are smaller than 5 millimeters, can stay airborne for nearly a week.

Another newfound fact is that more than 10 percent of airborne microplastics out west could be coming in from the ocean, and there may now be more microplastics blowing out of the ocean than there is going into it.

According to Simon. the sad reality is that these plastics have so thoroughly saturated the environment that, in a sense, they’ve homogenized. Particles from synthetic clothing and from degrading bottles and packaging seem to be moving between the air, land, and sea with such regularity — and enough intermixing — that it’s hard to pinpoint the source of a particular polymer. But bit by bit, researchers are developing a clearer picture of how these particles are cycling all over the planet.

“A major driver appears to be the atmospheric transport detailed in this new research,” Simon said. “As I’ve said before, plastic rain is the new acid rain.”

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