Delivered like dust by the wind and rain, researchers estimate that more than 1,000 tons of plastic microparticles - roughly the equivalent of 120-300 million plastic water bottles - falls upon National Parks and protected wilderness areas in the western United States each year. The results show that atmospheric transport is an important mechanism in the global distribution of microplastic pollution, including to remote locations, and they underscore the importance of reducing pollution from such materials, which here were small enough to accumulate in lung tissue. Though microplastics are found nearly everywhere on Earth, the sources and processes behind their ubiquitous distribution, or the "global plastic cycle," remain vaguely understood. Initially overlooked, recent studies have suggested that long-range atmospheric transport plays an important role in carrying microplastic pollution vast distances and to remote locations. Interested in its reach to conservation locations, Janice Brahney and colleagues evaluated the transport and accumulation of microplastics in eleven remote and protected areas across the western U.S. By comparing the size and shape of the particles deposited during wet and dry weather, Brahney et al. were able to identify atmospheric transport processes and deposition patterns, including that plastics deposited dry were smaller in size and traveled farther, "reminiscent of the global dust cycle but distinctly human in origin." The authors suggest that sensitive mountain ecosystems with simple food webs and shallow soils could be particularly sensitive to microplastic deposition. "A key insight from the new work is that fundamental tools for studying global dust transport can be applied to microplastics. Like dust, most particles measured were within the size range typical of global transport," write Chelsea Rochman and Timothy Hoellein in a related Perspective. "However, microplastics are less dense than soil and therefore might travel longer distances than natural dust particles."
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Journal
Science