Hoof it through the national parks of the western United States—Joshua Tree, the Grand Canyon, Bryce Canyon—and breathe deep the pristine air. These are unspoiled lands, collectively a great American conservation story.
Yet an invisible menace is actually blowing through the air and falling via raindrops: Microplastic particles, tiny chunks (by definition, less than 5 millimeters long) of fragmented plastic bottles and microfibers that fray from clothes, all pollutants that get caught up in Earth’s atmospheric systems and deposited in the wilderness.