Minnesota scientists say it appears endocrine-disrupting chemicals and pharmaceuticals are found in even the most pristine lakes in the state.
Researchers say they're not sure why the chemical compounds are so widespread, but they say more research is needed to better understand the potential impact on wildlife and humans.
The Minnesota Pollution Control Agency sampled a dozen lakes and four rivers across the state. Some of the samples came from water close to cities and others were from lakes in remote northern forests.
Environmental Research Scientist Mark Ferrey said they looked for 110 compounds including residue from plastic bottles, household detergents and pharmaceutical drugs.
Bisphenol A, a compound found in polycarbonate plastics, was found in 82 percent of lakes, the common painkiller acetaminophen was found in 50 percent of samples, 4-octylphenol diethoxylate, a detergent ingredient was found in 36 percent of lakes and 71 percent of rivers.
"These compounds appear to be commonplace in the lakes we've studied across Minnesota," Ferrey said. "Not at high concentrations, but they're present and in lakes where we might be surprised to find out they're present."
One of the puzzles for researchers is Northern Light Lake north of Grand Marais. Endocrine-disrupting compounds are thought to come mostly from sewage treatment plants, or septic systems. Northern Light Lake has neither; it's an undeveloped lake with just a public boat ramp.
"These compounds appear to be commonplace in the lakes we've studied across Minnesota."
But Mark Ferrey said the water from Northern Light Lake contained several contaminants, including compounds from detergents, and carbamazepine a common drug used to treat attention deficit disorder.
"When we got the results back it was pretty surprising what that lake had in terms of pharmaceuticals and other compounds," Ferrey said. "It's a little baffling to understand where they are coming from. We're not talking about toxic effects. However, there are studies that show effect at very low concentration, parts-per-trillion concentrations."
Until a few years ago, researchers didn't even have the technology to easily measure these compounds in parts per trillion. One part per trillion is one-twentieth of a single drop of water in an Olympic-sized swimming pool. The testing is expensive, up to $5,000 to test a single water sample for more than 100 chemical compounds.
But laboratory research shows even at low concentrations, endocrine disrupters can cause feminine characteristics in male fish and even lead to the collapse of fish populations. Recent research also shows the antimicrobial Triclosan, which is found in antibacterial soaps, might in low concentrations inhibit the growth of some wetland plants.
Deb Swackhamer, a University of Minnesota Professor and Co-Director of the Water Resources Center, said researchers need to understand where the different compounds are coming from so they can prevent the pollution. Besides sewage treatment plants, other potential sources are septic tanks and animal feedlots.
Swackhamer said, while there are no known human effects from the chemicals, research shows the compounds affect fish at very low concentrations.
"I think the reason people are nervous about that is that these are very biologically-active compounds," Swackhamer said. "So it's not to say we can definitively say the concentrations in the environment are harmful, but we're paying a great deal of attention because these are very potent chemicals at very small concentrations."
Researchers in Minnesota and elsewhere are now starting to look at the potential genetic changes caused by endocrine-disrupting chemicals.
Using DNA micro arrays, they can then identify any genes that respond to the chemical exposure.
Swackhamer said that research could help explain how humans might be affected by long-term, low-dose chemicals in the environment.
"And once we understand the genetic response, you know if these ten genes are turned off and these ten genes are turned on, once we understand the biological significance of that then we'll be able to use those tools in humans," she said. "So I think that's the most exciting area in research right now. It's moving us ahead by quantum leaps."
Minnesota researchers say right now, they only have a snapshot of chemical contamination in the state's waters. They plan to continue testing lakes and streams, looking for trends.
The MPCA also plans to start testing groundwater next year to see if the chemicals that appear ubiquitous in surface water are also making their way into underground aquifers.