This was one of the key insights shared by Loyola University Chicago biologist Tim Hoellein during a scientific seminar held at CEAB-CSIC on March 6. Hoellein is an expert in the dynamics and impacts of aquatic waste, primarily working in the Great Lakes region of North America, and collaborates with the center’s continental ecology team.
During the session, the researcher revealed that microplastics have been found in the digestive systems of fish preserved in museums since the 1950s, demonstrating that this contamination has been present for decades, since the early production and consumption of plastic. Hoellein explained, “We have found microplastics in every fish species we analyzed, both in contemporary specimens and in older ones that had been preserved. They have been ingesting them for a long time, which confirms that this type of pollution has existed in our rivers and lakes for decades and continues to increase.”
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In urban rivers and lakes, about 75% of waste consists of plastics, whether macro, meso, or microplastics. Their retention or movement in ecosystems varies greatly, depending not only on the specific characteristics of each piece of waste—such as shape, size, density, and composition—but also on the characteristics of the natural environment where they end up. “Predicting their movement and impacts is difficult,” the expert noted, “but we know some retention patterns. For example, plastics that break down into strips, such as plastic bags or wet wipes, often get caught in vegetation; finer sediments retain more microplastics; and when water levels are lower, retention increases until the flow rises again.” The biologist’s team has also confirmed, through experiments, that some plastics travel rapidly, as if on a conveyor belt, until they reach large lakes or the ocean.
Regarding the origin of this pollution, Hoellein emphasized that it is not always obvious. “Most microplastics come from synthetic clothing,” he explained. It is estimated that for every 6 kilograms of polyester clothing washed, around 4 grams of plastic microfibers are released into wastewater, eventually polluting nature, as treatment plants cannot capture such small particles.
Hoellein pointed out that we are still far from fully understanding the impacts of plastics on ecosystems and human health due to their slow degradation and the relatively short time they have been studied. “These plastics contain and release chemicals, fecal bacteria, and antibiotic-resistant microorganisms, which could pose significant public health risks.” He also highlighted, “The carbon in plastics becomes carbon in rivers. This means it must be accounted for in carbon cycle models. It may seem like a small proportion now, but since plastics persist for so long and accumulate, the impact could become significant.” These areas, along with the processes of plastic retention and transport, are key research topics at CEAB-CSIC.
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The seminar also featured some lighthearted moments when Hoellein asked the audience about the most unusual plastic waste they had found in rivers, receiving surprising responses such as a full set of dentures, alongside expressions of frustration over the continued presence of condoms, wet wipes, and other waste that should never be flushed down toilets.
The session ended on an optimistic note: the researcher emphasized that both individual and community actions are making a difference. As an example, he highlighted the collaboration between his research team and organizations like Friends of the Chicago River and Kayak for Conservation, which remove waste from rivers, support scientific research, and raise awareness about the importance of protecting the natural environment.
L'entrada “We have found plastics inside fish from the 1950s” ha aparegut primer a CEAB.