The Rhine, which flows from the Alps to the North Sea, is one of Europe's great rivers, flowing past cities ranging from Basel in Switzerland and Cologne in Germany to Strasbourg in France. The majestic waterway has been an important transportation artery since the days of the Roman Empire, and in medieval times, lords built their castles along it.
Sadly, though, the Rhine also has earned another distinction, as one of the most polluted rivers on the planet.
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As a new study published in Scientific Reports reveals, the Rhine's waters have one of the highest concentrations of microplastics – that is, particles smaller than 5 millimeters in diameter - ever measured.
Researchers from the University of Basel sampled 11 locations along the 500-mile stretch from Basel to Rotterdam in the Netherlands. They discovered an astonishing 892,777 particles per square kilometer of the river. The single highest concentration was found at Rees, in Germany, where the concentration was 3.9 million pieces per square kilometer.
The Rhine's microplastics concentration was more than four times as high as the most polluted Swiss lakes, Lake Geneva and Lake Maggiore, and 10 times as high as Lake Ontario in North America.
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Microplastics, which are found in most of the world's bodies of water, are formed from fragmentation of larger plastic debris and also by intermediate-stage products in plastic production. They're a health hazard to aquatic creatures who ingest them, and the extent of the risk that they pose to humans is still unclear.
"The Rhine's microplastics concentrations are thus among the highest so far studied worldwide," Basel biology professor Patricia Holm said in a press release.
Holm estimated that the Rhine's daily load of plastics amounts to 191 million plastic particles, and that just includes its surface. Over the course of a year, that adds up to about 10 tons of plastic waste. " Each one of these billions of plastic items can be ingested by organisms and have negative effects on their health," she said.