Researchers have detected multiple antibiotics in Brazil's Piracicaba River, accumulating in water, sediment, and fish, especially in the dry season. A banned drug, chloramphenicol, was found in lambari fish sold for consumption. Experiments with the aquatic plant Salvinia auriculata showed it can remove some antibiotics but may alter fish exposure.
Researchers from the Center for Nuclear Energy in Agriculture at the University of São Paulo (CENA-USP) analyzed the Piracicaba River in São Paulo state, Brazil, near the Santa Maria da Serra dam and Barra Bonita reservoir. Samples of water, sediment, and fish revealed 12 antibiotics from groups including tetracyclines, fluoroquinolones, sulfonamides, and phenols. Concentrations were below detection limits in the rainy season but detectable in the dry season, when lower water volumes concentrate pollutants from sewage, wastewater, aquaculture, pig farming, and agricultural runoff. Levels reached nanograms per liter in water and micrograms per kilogram in sediment, with some exceeding global comparisons due to organic-rich sediments that store and potentially release compounds over time, according to lead researcher Patrícia Alexandre Evangelista, whose work was supported by FAPESP and published in Environmental Sciences Europe in 2025. The study found chloramphenicol, banned for livestock in Brazil due to toxicity risks, in lambari fish (Astyanax sp.) at tens of micrograms per kilogram during the dry season. Lambari are commonly consumed locally, raising exposure concerns. Enrofloxacin, used in animal husbandry and human medicine, was also prominent. Controlled experiments tested Salvinia auriculata, a floating aquatic plant, for phytoremediation. It removed over 95% of enrofloxacin from water with high biomass, reducing its half-life to 2-3 days, and 30-45% of chloramphenicol, with half-lives of 16-20 days. Antibiotics accumulated mainly in plant roots. However, the plant sometimes increased fish absorption rates, possibly by altering antibiotic forms. Chloramphenicol persisted in fish over 90 days, causing DNA damage like micronuclei in blood cells, which the plant mitigated. Enrofloxacin had quicker elimination (21 days) and less accumulation. Evangelista noted, 'This shows that using plants as 'sponges' for contaminants is not a trivial matter. The presence of the macrophyte changes the entire system.' Supervisor Valdemar Luiz Tornisielo added that the findings highlight antibiotic pollution's complexity and potential for low-cost natural solutions, though plant biomass management is crucial to prevent re-release. Radiolabeled compounds were supplied by the International Atomic Energy Agency.
