Microplastic particles (diameter < 5mm) have been measured in the remotest parts of the earth but how they get there is not well established.  It is often assumed that a major route for microplastics to enter the marine environment is via rivers, either as small particles or from the breakdown of larger plastic pieces once in seawater.  The possibility that microplastics are transported to the oceans through the atmosphere is a more recent idea.  If correct, atmospheric transport presents a more credible way for microplastics to reach remote areas, rather than the much slower route of river input and subsequent transport by ocean currents.  Initial calculations indicate that the riverine and atmospheric routes may be of similar magnitude; but there are many uncertainties mostly due to lack of measurements of microplastics in air over the open oceans.  However, if the atmospheric route is significant then there are substantial implications for policies aimed at reducing plastics entering the marine environment and also for the upcoming UN Treaty on Plastic Pollution.

microplastics,atmospheric transport,policy implications