A number of studies, for example, have documented microplastics in rain falling all over the world — even in remote, unpopulated regions. For one 2020 analysis in the journal Science, researchers documented microplastics in rainwater that fell on several national parks and wilderness areas in the Western US. Most of the plastic bits were microfibers, such as those shed from polyester sweaters or carpeting on the floor of a car. The researchers estimated that more than 1,000 metric tons of plastic from the atmosphere fall on parks in the West each year, including both as rainfall and as dry dust. That’s equivalent to roughly 120 to 300 million plastic water bottles, according to the study.