Source: Raceforwater / CC BY-SA 4.0While looking at the impact of microplastics on U.K. waterways over the course of several years, researchers from the University of Manchester discovered that flash floods had carried a significant amount of microplastics from U.K. rivers and streams to the ocean.

Detailing their findings in the journal Nature Geoscience, researchers were originally studying the levels of tiny plastic fragments and beads in Britain’s rivers and streams. Yet, when flash floods struck Ireland, England and parts of Wales in 2015-2016, researchers saw firsthand how the microplastics, which had settled in riverbed sediment, were carried out to sea.

At first, the team had regularly taken samples from a number of sites throughout Manchester where they found microplastics in every stream and river tested, including the discovery of roughly a half-million particles per square meter in the sediment of the River Tame — a record for the most reported worldwide.

After the flooding, however, the rivers and streams lost an estimated 70 percent (or roughly 43 billion particles) of the microplastics, with much of it (approximately 17 billion particles) making its way out to sea and the rest of it ending up on land surrounding the rivers.

According to researchers, these findings suggest that the amount of microplastics in rivers, streams and oceans is likely being underreported and, consequently, that humans are likely ingesting more microplastics than originally suspected.

To read more on the findings, go to the journal Nature Geoscience.