Biology students may remember learning the water cycle, the carbon cycle or the nitrogen cycle. Now, new research suggests we may need to add “the plastic cycle” to the list of Earth’s list of biogeochemical processes, reports Damian Carrington for the Guardian.
The authors of the new paper, published this week in the journal Proceedings of the National Academy of Sciences, write “microplastic particles and fibers generated from the breakdown of mismanaged waste are now so prevalent that they cycle through the Earth in a manner akin to global biogeochemical cycles.” The authors focused on airborne microplastics, which they say “now spiral around the globe with distinct atmospheric, oceanic, cryospheric, and terrestrial residence times.”
The study’s models suggest some 1,100 tons of microplastic, defined as particles smaller than 0.2 inches, currently swirl over the western United States and many stay airborne for almost a week, reports Matt Simon for Wired. Some 84 percent of that plastic in the air comes from roads where cars and trucks kick microplastics up in their wakes, and, surprisingly, the offending stretches of asphalt tend to be located outside of major cities. Another 11 percent of the petrochemical miasma may waft in from the oceans, with dust from agricultural soils contributing the remaining five percent.
One of the major implications of these results is much of the plastic suspended in the atmosphere isn’t coming from fresh sources.
“We found a lot of legacy plastic pollution everywhere we looked; it travels in the atmosphere and it deposits all over the world,” says Janice Brahney, an environmental scientist at Utah State University and the study’s lead author, in a statement. “This plastic is not new from this year. It’s from what we’ve already dumped into the environment over several decades.”
In the ocean, as the tens of millions of tons of plastic already floating at sea break down into microscopic pieces, some of those minute particles take flight into the atmosphere via sea spray and get carried around the world by wind.
The team arrived at these figures by collecting more than 300 samples of airborne plastics at 11 sites across the American West and used those data to inform their model which then created hypothetical scenarios for how the microscopic trash reached its destination.
In addition to identifying the potential sources of the pollution raining down across the western U.S., the study also suggests these airborne plastics can travel far enough to fall on Antarctica in significant quantities.
“What humans have been doing for decades now is what I call a ‘plastification’ of the landscape and oceans.” Andreas Stohl, an atmospheric scientist at the University of Vienna who was not involved in the research, tells the Guardian. “The study confirms the global-scale nature of microplastic transport in the atmosphere and does a good job in highlighting highly relevant and concerning possibilities, but more measurement data is needed to get a better idea of the sources.”
“People should be concerned about airborne microplastics,” Stohl tells the Guardian. “Firstly, because they will inhale it and it is very likely that this will have some health impacts. And secondly, because the atmosphere is a great distributor… Eventually, we will have extremely high concentrations of plastics everywhere.”