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February 5, 2020

Human-use pharmaceuticals are frequently present in many small streams, even those not receiving wastewater treatment plant discharges, reports a new study by the U.S. Geological Survey. In some streams, pharmaceuticals were detected at concentrations that could potentially be of concern for fish health.

USGS scientists analyzed three to four water samples from 444 small streams across four major regions of the U.S. as part of the USGS Regional Stream Quality Assessment. The number of compounds detected in a stream and the sum of pharmaceutical concentrations was higher in streams with more urban land use and in streams receiving wastewater treatment plant discharge.

Pharmaceuticals were commonly detected in these streams. (Those detected at 17–68% of sites) included metformin, a type-II diabetes medicine; lidocaine, acetaminophen, and tramadol, all painkillers; carbamazepine, an anti-seizure medication; and fexofenadine, an antihistamine. Nicotine was detected at 70% of sites. Two or more pharmaceuticals were detected at least once in 95% of the streams that have some urban land use in their watershed.

Because pharmaceuticals are designed to affect biological activity, their presence in streams is a potential concern for aquatic ecosystems. The potential risk to aquatic biota associated with exposure to pharmaceuticals in the streams was evaluated through comparison with concentrations at which a chemical causes different types of cellular activity, available through the U.S. Environmental Protection Agency Toxicity Forecaster [ToxCast™]. More than 60% of sites had at least one pharmaceutical compound at a concentration in at least one sample that might be of potential concern for fish.

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