Hidden Antibiotics in Brazilian River Spark Food Safety Concerns, But Aquatic Plant Offers Hope
Antibiotics are accumulating in a major Brazilian river, particularly during the dry season, raising concerns about potential human exposure through the food chain. A recent study has identified residues of various antibiotics in the Piracicaba River, and even detected a banned substance in fish sold for consumption. However, researchers are as well exploring the potential of a common aquatic plant, Salvinia auriculata, to mitigate this contamination.
Antibiotic Contamination in the Piracicaba River
Researchers at the Center for Nuclear Energy in Agriculture at the University of São Paulo (CENA-USP) have identified multiple classes of antibiotics in the Piracicaba River, a vital waterway in the state of São Paulo, Brazil. The findings, published in Environmental Sciences Europe, reveal that these substances not only persist in the water but also accumulate in fish populations. The study, led by Patrícia Alexandre Evangelista and supported by FAPESP, combined environmental monitoring, bioaccumulation studies, genetic damage analyses, and phytoremediation experiments to understand the extent of the problem and potential solutions.
Seasonal Patterns and Pollution Sources
Sampling conducted near the Santa Maria da Serra dam, close to the Barra Bonita reservoir, revealed a clear seasonal pattern. Antibiotic concentrations were generally low during the rainy season, but increased significantly during the dry season when water volume decreased and pollutants became more concentrated. Sources of contamination include treated urban sewage, domestic effluents, aquaculture, pig farming, and agricultural runoff. Researchers analyzed water, sediment, and fish samples for 12 commonly used antibiotics – tetracyclines, fluoroquinolones, sulfonamides, and phenols.
Banned Antibiotic Detected in Fish
A particularly concerning finding was the detection of chloramphenicol in lambari fish (Astyanax sp.) collected from local fishermen. Chloramphenicol is banned for use in livestock in Brazil due to its potential toxicity, raising concerns about human exposure through consumption of contaminated fish. The substance was only detected during the dry season, at levels of tens of micrograms per kilogram.
Salvinia auriculata: A Potential Solution?
The research team investigated whether Salvinia auriculata, a floating plant often considered invasive, could help reduce antibiotic contamination. In controlled experiments, the plant demonstrated a high efficiency in removing enrofloxacin, with over 95% removal from water within a few days when using higher plant biomass. The half-life of enrofloxacin dropped to approximately two to three days. Removal of chloramphenicol was slower, ranging from 30% to 45% removal with half-lives of 16 to 20 days.
Complex Interactions and Genetic Damage
Interestingly, the presence of Salvinia auriculata altered how fish absorbed antibiotics. Whereas the plant reduced antibiotic levels in the water, it sometimes increased the rate of absorption by fish, potentially due to changes in the chemical form of the antibiotics. The study also examined genetic damage in fish, finding that chloramphenicol significantly increased DNA damage, but this damage was reduced when Salvinia auriculata was present. However, the plant did not significantly reduce the genetic effects of enrofloxacin.
Limitations and Future Directions
Researchers emphasize that Salvinia auriculata is not a simple solution. Proper management of the plant after it absorbs contaminants is crucial to prevent re-release of antibiotics into the environment. Despite these limitations, aquatic plants offer a potentially low-cost, nature-based approach to reducing pollution, particularly in areas where advanced treatment methods are not feasible. Further research is needed to fully understand the complex interactions between antibiotics, aquatic plants, and aquatic organisms.
“The study shows that the problem is real, measurable, and complex. And any strategy to address it must consider not only the removal of the contaminant, but also its biological and ecological effects,” says Evangelista.