We already knew that microplastic pollution can be found everywhere from our bottled water to the remotest corners of the world so it should really be no surprise to hear that it rains down on us. What might be surprising, however, is the quantity that falls.
A shocking revelation
Utah State University Assistant Professor Janice Brahney and her team identified samples of microplastics and other particulates collected over 14 months in 11 national parks and wilderness areas. What they discovered is that more than 1000 tons of the stuff rains down just in the western U.S. every year.
"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 remote locations were synthetic polymers."
In 2017 alone, there was a global production of 348 million metric tons of plastic. This is dangerous as the same things that make plastic so convenient, its high resilience and longevity, are the same things that ensure it comes back to haunt us. More specifically it comes back as microplastics, tiny particles of plastic that accumulate in wastewaters, rivers, oceans - and as Brahney's team discovered- in the atmosphere.
The atmospheric limb
"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."
The research looked at the source and life history of both wet (rain) and dry microplastics. Wet deposition of these microplastics was found to largely come from cities while dry deposition showed indicators of long-range transport. This alarmingly revealed that microplastics are small enough to be entrained in the atmosphere for cross-continental transport.
"This ubiquity of microplastics in the atmosphere and the subsequent deposition to remote terrestrial and aquatic environments raise widespread ecological and societal concerns," Brahney added. "Identifying the key mechanisms of plastic emission to the atmosphere is a first step in developing global-scale solutions."