Scientists are figuring out how streams get contaminated with drugs.Photo Credit: alex grichenko/iStock/Thinkstock Pharmaceuticals in surface water such as lakes and streams are a growing concern. They can cause developmental and other health issues in aquatic life. Scientists have largely considered treated wastewater that’s released into the environment as the main source. But now one team reveals in ACS’ journal Environmental Science & Technology Letters that other important factors are also contributing to the problem.

One specific diabetes drug, metformin, has been found widely in treated wastewater, in naturally occurring water bodies and even in tap water. Some research has shown that the drug can cause genetic changes in fish. Similar studies have found that other pharmaceuticals can also have various health effects on aquatic life. While treated wastewater that is introduced back into the environment is an obvious route for drugs to enter waterways, Paul M. Bradley and colleagues wanted to see whether other sources might be involved.

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The researchers tested water from 59 streams across four states in the Southeastern U.S., both close to and far away from wastewater treatment plants. The samples contained a wide range of pharmaceuticals and other active compounds, including metformin, nicotine and the anti-seizure medication carbamazepine, at varying concentrations. Their results confirmed that wastewater plants are important sources of pharmaceuticals, but they also demonstrated that these compounds are common in streams that aren’t fed by wastewater plants. This suggests that urban run-off and the below-surface movement of water could be important contributors to the flow of drugs into streams.

The authors acknowledge funding from the U.S. Geological Survey.