In the most comprehensive study of a variety of chemical compounds coming from municipal sewage plants, the Minnesota Pollution Control Agency confirmed widespread, but low concentrations of water contamination from human medications and antibiotics.
The study examined 25 of Minnesota's 500 municipal wastewater treatment plants, MPCA researcher Mark Ferrey said.
"Whereas before we've looked at maybe one, two, three different wastewater treatment plants, this is the first time we've looked at 25," Ferrey said. "It probably is one of the largest studies like this in the country."
The study reinforced what earlier researchers learned, that pharmaceutical compounds used by people are very common in rivers and lakes across the state.
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Researchers also found another class of chemical compounds in their water samples -- endocrine disruptors proven to alter fish reproduction.
The compounds researchers found most often include carbamazapine, a drug used to treat attention deficit disorder. They also found various antibiotics and diphenhydramine, a common antihistamine.
Ferrey said most of the compounds are found in very small amounts, measured in parts per trillion.
"We just don't know what the long-term effect is going to be on our environment."
"Some of these compounds can have effects at these vanishingly low concentrations," he said. "But for the vast majority of these compounds, we really don't know what effect they're likely to have on the environment."
That's because the environmental effects of most of the pharmaceuticals have not been adequately studied.
Technology exists to remove those compounds during the wastewater treatment process, but because it's so expensive, it's rarely used.
Minnesota Wastewater Operators Association President Bob VanMoer said research on pharmaceutical and endocrine active compounds is still in the infancy stage. But he suspects it will be an expensive problem for cities.
"I think it's something that's going to be a big issue in the future, especially when we start finding some of these things that force us into an extremely expensive treatment system to take care of this," said VanMoer, who is the wastewater plant superintendent in Marshall, Minn.
But wastewater treatment plants aren't the only source. Some of the compounds were found upstream from treatment plants. That means they were introduced from another source.
Researchers say the compounds might also come from septic systems and animal feedlots. But they haven't done enough research to pinpoint those sources.
Ferrey said much more research is needed before anyone can say how serious a problem chemical compounds are in surface water.
He also said it's clear the chemicals are well below levels toxic to humans.
"However, it isn't as though we shouldn't be concerned at all, because we just don't know what the long-term effect is going to be on our environment," Ferrey said. "And that's what we need to be focused on, is the long term."
This summer, Minnesota researchers will begin trying to learn more about how the chemicals in wastewater affect fish and other aquatic life. They'll expose fish to the chemicals in streams and document the effects.