Rio study reveals microplastic contamination threatens marine life and food security

Across Rio de Janeiro's waterways—from the enclosed Lagoa Rodrigo de Freitas to the open beaches and islands of Guanabara Bay—a contamination is spreading that no one can see. Microplastics and the chemical compounds they shed as they break down are accumulating in the sediment, the water, and the bodies of the fish, shrimp, mussels, and sea urchins that feed the city. A new study led by biologist Raquel de Almeida F. Neves at the Federal University of the State of Rio de Janeiro has mapped the scope of this threat across multiple points along the coast, revealing not just an ecological problem but a public health one: the seafood people eat is contaminated.

Neves and her team, funded by Rio de Janeiro's research foundation FAPERJ, collected samples from strategic locations—the lagoon, the bay's islands and beaches, the open ocean shoreline, and estuaries in southern Bahia. They gathered sediment from the seafloor, water samples, and living organisms: the creatures that matter most to local fishers and dinner tables. The goal was to identify and measure the specific toxins that leach from degrading plastic—bisfenols, phthalates, and others—and to trace how these substances move through the food chain. "We collected water, sediment, and organisms simultaneously," Neves explained, "which lets us understand the complete cycle of contamination and its impact on the fish and shellfish people actually consume." The team then ran chemical tests in the lab, using advanced techniques like gas chromatography and mass spectrometry to identify what was there, and toxicity tests to measure what it actually does.

The laboratory work was rigorous. Researchers reproduced marine conditions in controlled settings and exposed various species to different concentrations of the pollutants, measuring both immediate and long-term effects. They calculated critical thresholds—the concentrations at which half the organisms showed toxic effects or died. They also tracked molecular and behavioral changes in the animals, looking for damage at multiple biological levels. Shrimp and fish proved most vulnerable, which matters because these are the species that sustain both the local fishing economy and the protein intake of people who depend on them.

The study produced concrete outputs: environmental and biological indicators that can be used to monitor plastic pollution going forward; detailed maps showing which coastal areas are most contaminated; risk assessments for both marine life and human consumption; and proposed biomarkers to track the health of fish stocks. But Neves was clear that the research was not meant to stay in the laboratory. The team conducted public lectures in cultural spaces across Rio, ran educational programs in public schools, and worked directly with artisanal fishers—the people most affected by both the contamination and the solutions. "Our goal is that this research leads to concrete actions for preservation," she said. "The engagement of fishers and dialogue with schools are fundamental to raising awareness."

What emerges from the data is a picture of a city whose relationship with its own coast has become complicated. The people who fish these waters for their living, and the people who buy and eat what they catch, are now consuming organisms that have accumulated plastic-derived toxins. The contamination is not visible—it does not change the color or smell of the shrimp or the fish—but it is there. The research provides the evidence base for monitoring and for policy, but it also raises a question that sits beneath all the science: what happens when the food that sustains a community becomes a vector for harm?