A cornucopia of man-made chemicals — including cocaine, DEET, synthetic estrogen, antibiotics, antidepressants and plastics derivatives — are finding their way into even isolated Minnesota lakes, an indication that some contamination is becoming the norm for virtually all the state's waters.
Scientists studied 50 lakes across Minnesota chosen at random and tested them for 127 compounds. All but three tested positive, with varying concentrations of one or more chemical. The insect repellent DEET was found in 76 percent of the lakes, and cocaine, in a finding that stunned the researchers, was found in 32 percent.
"That was astonishing," said Mark Ferrey, lead researcher for the new report, which was released Monday by the Minnesota Pollution Control Agency (PCA) and is the most comprehensive to date in a series of studies examining chemical contamination in Minnesota lakes and rivers.
"We need to look in the mirror," he said. "No matter what we use, it finds its way into the environment."
Far less understood, however, is the impact the contaminants are having on aquatic life and humans, Ferrey said. A growing number of studies are finding that some chemicals — in particular those that resemble hormones — can have a powerful biological effect on fish, mussels and other species even at tiny concentrations. They are not toxic, but can disrupt reproduction and even change genetics through several generations of animals.
One experiment in a lake in Canada found that two years after synthetic estrogen was introduced at a concentration of five parts per trillion, the fathead minnow population crashed and the trout population began to decline. Five parts per trillion is the equivalent of adding five drops to 15 or 20 swimming pools, Ferrey said.
Identifying and tracking the chemicals and their impact on natural ecosystems are new areas of research. In Minnesota, the work began with a study designed to find if and how chemicals are being released through wastewater treatment systems into streams and rivers. Ferrey and others found the compounds downstream from treatment plants, where they expected to find them. But they were also found upstream as well.
A 2008 study of 11 lakes in Minnesota showed that pharmaceuticals, personal care products and other chemicals were widespread at low concentration, even in lakes with minimal shoreline development, raising puzzling questions about their origin. But wherever researchers found the chemicals, they often found problems in fish and other animals. Altogether, they have now found chemicals — from personal care products to anti-corrosives to drugs — in a total of 200 locations.
Some of the chemicals might come from septic systems that contaminate groundwater. But, Ferrey said, it's increasingly clear that some of them are finding their way to remote places by air. Cocaine is a case in point.
Ferrey said he couldn't believe the analyses when cocaine turned up in nearly one-third of the lakes tested, some of which had little development or human use. But cocaine is as widely used in the United States as many legal drugs. An estimated 2.4 percent of the population uses it at least occasionally, and 157 tons of it are smoked or snorted every year, according to a recent United Nations report. Ferrey said small amounts escape into the air and hitch a ride on dust particles, which eventually fall into Minnesota lakes.
Cocaine was the third most common chemical found, following DEET and Bisphenol A, a chemical from plastic that is of increasing concern for its possible health impacts on both animals and people.
Carcinogen of concern
Ferrey was also surprised to find carbadox, an antibiotic used in swine. It turned up in 28 percent of the lakes, including some in the Twin Cities and other places that had no connection to feedlots or pig farms. Carbadox is of particular concern for people: It's a carcinogen that has been banned in Europe and Canada, he said, and U.S. regulations require pig farmers to stop feeding it to the animals 40 days before slaughter.
Slowing the release of chemicals into the environment could be a simple matter of not dumping them down the drain, Ferrey said. He's far more careful now than he used to be, he added.
But much of the contamination comes from human waste, streets, roofs and runoff from farm fields; many of the chemicals make it through the wastewater treatment system. And fixing that is far more daunting: New water treatment technologies such as reverse osmosis can cost millions of dollars per plant, he said.
But the research, and the understanding it provides, is accelerating rapidly, Ferrey said.
"Ten years ago, these studies weren't there. And now they are," he said.
Josephine Marcotty • 612-673-7394
