Remote wilderness areas and national parks in the western United States are getting a dusting of plastic every year, perhaps 1000 tons or more, according to a new study. Up to one-quarter of the microscopic pieces of plastic—which come from carpets, clothing, and even spray paint—may originate in storms passing over nearby cities, whereas the rest likely comes from farther flung locations. The findings, the first to tease apart geographic origins, add to mounting evidence that such microplastic pollution is common worldwide. “We created something that won’t go away,” says Janice Brahney, a biogeochemist at Utah State University and lead...