The challenge is that there still isn\u2019t one standard way to measure how much microplastic falls from the atmosphere, which helps explain why estimates vary so widely. A lot of the instruments researchers use to measure particles in the atmosphere weren\u2019t designed specifically to collect microplastics.<\/p>\n
\u201cThey\u2019re aerodynamically designed for spherical particles of a certain density and to filter out size based on those properties,\u201d Brahney says. But plastics come in different shapes and have lower densities. \u201cThey\u2019re not calibrated for microplastics. So we don\u2019t really know how effective they are at pulling in what\u2019s exactly in the atmosphere.\u201d<\/p>\n
Brahney used a deposition sampler in her research, which relies on gravity to collect particles as they fall. But that method has limitations too. Wind can create what she calls a \u201csampler shadow effect\u201d, where some plastic particles are pushed away from the sampler. \u201cSo it usually underestimates what\u2019s being deposited,\u201d she says.<\/p>\n
Researchers also measure different things. The concentration of plastic floating in the air isn\u2019t the same as the amount deposited on the ground, and Brahney says the two can\u2019t easily be converted.<\/p>\n
How Do Microplastics Get Into the Air?<\/p>\n