A lot of different chemicals end up in our rivers and streams.
Researchers are finding these mixtures of chemicals are more complex than we thought, and it could hurt fish and other creatures.
Dana Kolpin is a research hydrologist with the U.S. Geological Survey and an author of the new study in the journal Environmental Science & Technology.
He and his team tested 38 streams and rivers across the country for 719 chemicals. They found as many as 161 different chemicals in one waterway (the Chicago Sanitary and Ship Canal).
“Many of these compounds we’re finding actually are by design meant to have a biological effect, whether it’s a pesticide or a pharmaceutical,” says Kolpin. So, he says that warrants more study to find out what the impacts could be on wildlife, and possibly on people.
Kolpin says many of the rivers and streams they tested had a mixture of numerous chemicals.
“There’s a number of areas that do have a kind of a high impact from a variety of sources, for example, wastewater treatment plants are certainly a big source of contaminants to the environment,” Kaplan says. “In terms of this set of 38 streams, we found that half had at least 70 or more compounds in that single water sample."
The most common compounds were pesticides and pharmaceuticals: compounds that are meant to be biologically active. From the study:
The 10 most-frequently detected anthropogenic-organics included eight pesticides (desulfinylfipronil, AMPA, chlorpyrifos, dieldrin, metolachlor, atrazine, CIAT, glyphosate) and two pharmaceuticals (caffeine, metformin) with detection frequencies ranging 66−84% of all sites.
Kolpin says not every chemical found in the streams is necessarily harmful on its own. But he says it gets complicated when you have mixtures.
"We just never know when you mix things together what kind of unintended consequences there could be from having two compounds, or multiple compounds or this whole soup of compounds together," he says.
That’s what researchers hope to study next.
“This national study was a pilot study to really, really dive into this chemical mixture topic in more detail. Now, the toxics program within the U.S. Geological Survey has devoted a whole project specifically to contaminant mixtures," he says. "So really, it shows this was a very important area of research for us.”