Potentially harmful chemicals and pharmaceuticals are widespread in Minnesota streams, state scientists found in a new study.
The study by the Minnesota Pollution Control Agency also shows fish have genetic changes when exposed to the mix of chemicals.
In the most comprehensive study of chemicals in Minnesota, the agency's scientists collected water samples from 25 sewage treatment plants across Minnesota. They also sampled water upstream and downstream from the treatment plants for 78 chemicals.
Among the substances scientists most often found are the antibiotic sulfamethoxazole and carbamazepine, a drug used to treat attentional deficit hyperactivity disorder, agency scientist Mark Ferrey said. They also found the antibiotic trimethoprim and anti-depressant compounds.
Other commonly found chemicals include components of detergent, bisphenol A, which is found in plastics, and contraceptive hormones.
Scientists found chemicals at more than 90 percent of the locations they sampled and chemical traces at all locations. Researchers expected to find the chemicals flowing out of sewage treatment plants, but were somewhat surprised to also find the chemicals upstream from treatment plants.
Ferrey said that indicates other sources, such as septic systems, or agricultural runoff. He said the compounds are all found at very low concentrations, measured in parts per billion or parts per trillion.
"But just because these concentrations are very, very low doesn't mean they can't have effects," Ferrey said. "More and more results are coming out that show that these compounds can have pretty profound hormonal effects or estrogenic effects even at those concentrations."
Many of these chemicals act like hormones so they can cause physical changes in fish or other aquatic life.
The study also examined how fish respond to the chemicals at the genetic level. St. Thomas University scientist Dalma Martinovic found hundreds of fish genes are turned on or off by exposure to the water contaminated with chemicals.
"One of the ones that really pops up are the immune responses," Martinovic said. "We are seeing the immune system mounting higher or lower responses. And that's what I'm seeing quite consistently across all of the samples."
More research is needed to know exactly how the genetic change affects fish. The DNA analysis also found every sample of wastewater caused an estrogen like response in fish cells.
The next step for scientists would be a more detailed study of the fish immune system.
"So instead of going after a specific question you have in your head you go in and look at the effects and then work backwards," Martinovic said. "What it allows you to do is blindly probe and identify what the problem is without having this preconceived notion what the problem might be."
The research confirms earlier studies showing chemicals that mimic hormones in the body are widespread in Minnesota rivers and lakes. But Ferrey said the study only reveals very basic scientific data and leaves many unanswered questions.
"We don't know exactly what the effect is of that stuff in our water. We don't know if it's causing problems in fish and wildlife," he said. "We certainly don't know if these things pose any risk to human health. Really what we're doing now is observing the effect of our society on our environment and our surface water."
Ferrey wants his next research to focus on discovering specific sources of hormone like chemicals in water. Septic systems and agricultural runoff are two important areas to study, but he also hopes to learn if these chemicals are part of the water cycle, falling with the rain and snow.
He said more research is needed to understand the effect of chemicals and pharmaceuticals on aquatic life.