Environmental release of and exposure to antibiotics may have consequences for human health and aquatic life. Low levels of human antibiotics (HAs) and veterinary antibiotics (VAs) occur in surface waters across the United States, each with distinct transport routes. HAs and their by-products are released in wastewater treatment plant (WWTP) outflows, while VAs are associated with runoff from soils receiving manure application, and occasionally from failures in concentrated animal feeding operation (CAFO) wastewater containment. To date, we have a limited understanding of how antibiotic concentrations vary by land-use type. Little information is available about how releases vary in rural streams, where livestock production is a critical economic sector and VA use is substantial. It is also unclear if antibiotic and wastewater nutrient concentrations remain linked after release.
This study compared spatial and temporal variation in antibiotics in streams Nebraska and Ohio. We used polar organic chemical integrative samplers (POCIS) to measure and estimate time weighted average antibiotic concentrations in streams adjacent to three land-use types: WWTP, CAFO, and row-crop agriculture. Highest concentrations of antibiotics were associated with WWTP effluent, though many of the same antibiotics were found in ag-influenced streams. The most frequently detected antibiotics differed between Nebraska and Ohio streams, with erythromycin and lincomycin consistently detected in Ohio and monensin consistently detected in Nebraska. Sulfa- based antibiotics and thiabendazole were consistently detected at sites in both states. There was no correlation between measured nutrients and antibiotic concentrations, suggesting differences in environmental pathways. Understanding the quantity and distribution of antibiotics, and linkages with contaminants such as nutrients will be crucial to mitigating antibiotic-resistance and minimizing untended ecological consequences.