Watershed researchers estimate more than 1000 tons of microplastics (equal to more than 123 million plastic water bottles) are deposited in national parks and wilderness areas each year. Researchers used high-resolution atmospheric deposition data and identified samples of microplastics and other particulates collected over 14 months in 11 western U.S. national parks and wilderness areas. They identified plastic and polymers’ composition to identify sources of plastic emitted into the atmosphere and tracked its movement.