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At least one pharmaceutical chemical was detected in all 59 streams sampled

Pharmaceuticals are widespread in small streams in the Southeast, according to a new study by the U.S. Geological Survey. In 2014, the USGS sampled 59 small streams in portions of Alabama, Georgia, North Carolina, South Carolina and Virginia for 108 different pharmaceutical compounds and detected one or more pharmaceuticals in all 59 streams. The average number of pharmaceuticals detected in the streams was six.

Previous research indicated that wastewater treatment facility discharges were the most likely source for pharmaceutical chemicals in surface water. However, the findings in this study, reported in the journal Environmental Science and Technology Letters, indicate other sources as well – only 17 of the 59 streams have any reported wastewater discharges.

“The widespread occurrence of pharmaceuticals in these small streams irrespective of wastewater discharges indicates the need for approaches for preventing pharmaceutical contamination that extend beyond effluent treatment,” said Paul Bradley, a USGS research hydrologist and the lead author of the study. “Sources of pharmaceuticals to these small streams likely include aging sewer infrastructure and leakage from septic systems.”

A map showing the study area with colored circles showing concentrations
Cumulative median concentrations of pharmaceutical chemicals detected during the sampling conducted in June of 2014 in 59 small streams. The four urban study areas are shown in boxes, with details in the study.

The most common pharmaceutical chemicals detected are:

  • Metformin: Used to treat Type II diabetes, this chemical was detected in 89 percent of samples
  • Lidocaine: Used as a pain reliever, this chemical was detected in 38 percent of samples
  • Acetaminophen: Used as a pain reliever, this chemical was detected in 36 percent of samples
  • Carbamazepine: Used to treat seizures, this chemical was detected in 28 percent of samples
  • Fexofenadine: Used as an anti-histamine, this chemical was detected in 23 percent of samples
  • Tramadol: An opioid pain reliever, this chemical was detected in 22 percent of samples

Although much uncertainty remains as to how pharmaceuticals affect aquatic organisms, some adverse effects have been documented. Antibiotic/antibacterial contaminants – detected in at least 20 percent of streams – can affect aquatic microbial communities, altering the base of the food web. Antihistamines, frequently detected in this study, affect neurotransmitters for many aquatic insects. And metformin, nearly ubiquitous in the streams studied, can affect the reproductive health of fish. 

The chemicals with the highest concentrations are those listed above, but none exceeded human health benchmarks. In addition to the individual chemicals listed, the two groups of compounds most frequently detected were nicotine-related compounds (71 percent of samples) and caffeine-related compounds (detected in 49 percent of samples).

This study is one of several regional stream-quality assessments by the USGS National Water Quality Assessment (NAWQA) Project. Findings will provide the public and policy-makers with information regarding which human and natural factors are the most critical in affecting stream quality. Regions studied include the Midwest (2013), Southeast (2014) and the Pacific Northwest (2015), and planning is underway for studies in the Northeast (2016) and California (2017).

Support for this work was provided by the USGS National Water Quality Program's NAWQA Project. Additional support was provided by the USGS Toxic Substances Hydrology Program.

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