Study: Rain and snow can transport chemicals to Minnesota's lakes, rivers

Houseboats on Lake Kabetogama.
Houseboats dock in a chain of islands on Kabetogama Lake in Voyageurs National Park. A new study found that many of the chemicals found in lakes can also be found in rain and snow.
Evan Frost | MPR News 2016

A new study offers an explanation to the mystery of why pharmaceuticals and other chemicals are found in remote Minnesota lakes, far from developed land that would create contaminated runoff.

"These chemicals such as antibiotics, and anti-corrosives and endocrine active chemicals were being found in lakes where we might not expect them because there was no surrounding development," said Mark Ferrey, a Minnesota Pollution Control Agency scientist who, in search of an answer, collected snow, rain and air samples at three locations in the Twin Cities and had them tested for 126 chemicals.

Ferrey found 17, including DEET, cocaine, antibiotics, an anti-corrosion chemical, an x-ray contrast chemical and the pain reliever naproxen.

Ferrey calls this study a proof of concept. He hopes to do a larger study with more samples in the future. But this research raises a lot of questions.

"Just the fact that we found a number of these in air and precipitation is significant," said Ferrey. "Because some of these, number one, haven't been detected in air and precipitation before and it does explain how we might be detecting these chemicals in remote surface water."

Previous studies have found chemicals in precipitation. For example, pesticides and flame retardant chemicals have been found in Arctic snow. But this study confirms for the first time rain and snow are transporting some of the pharmaceuticals and chemicals researchers have been finding in Minnesota lakes and rivers.

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These chemicals are also getting into water through wastewater treatment plants and septic systems. Ferrey says evaporation might lift them from water into the atmosphere. Another source might be bio-solid sludge from wastewater treatment plants that is spread on farm fields. Other studies have shown fine dust from that sludge can travel for miles on the wind.

The chemicals found in rain and snow are at very low levels, mostly parts per trillion.

"Just because they're at very low concentrations doesn't mean that it's just a curiosity," said Ferrey. "We should probably be concerned about the effects some of these chemicals are having."

"Even at these nanogram per liter, part per trillion level concentrations, these chemicals can have very observable effects on fish and wildlife in our lakes and rivers," he said.

Scientists have found that very small amounts of some of the chemicals can affect fish reproduction or cause genetic changes. Ferrey says more work is needed to fully understand the long term effects.

The study is published in the journal Science of the Total Environment.