Gender-Bending Chemicals in Minnesota Waters

The discovery of malformed frogs in the Minnesota River watershed in the 1990s touched off field and lab research on endocrine disrupters that is continuing to yield findings.


Minnesota, the state that made national headlines with the discovery of malformed frogs in the 1990s, has found endocrine disrupting chemicals and traces of pharmaceuticals even in some of its most remote and otherwise cleanest waters.  Armed with substantial state funding, the Minnesota Pollution Control Agency (MPCA) has released a new report and is now continuing field work to determine the aquatic range of endocrine disrupting chemicals that can mimic hormones and cause changes to the reproductive system or development of organisms.

The new study found the hormones androstenedione in 64 percent of sampled lakes and 50 percent of sampled rivers, estrone in 55 percent of the lakes and 75 percent of the rivers, and 17β-estradiol in 55 percent of the lakes and 38 percent of the rivers. “These may be of human origin, naturally occurring, or both,” MPCA observed.  Bisphenol-A was found in 45 percent of the sampled lakes and 38 percent of sampled rivers.

The report also disclosed that endocrine disrupting chemicals were found in a lake north of Grand Marais in lightly-populated Arrowhead region. No sewage plants or septic tanks, the suspected “point sources” of the chemicals, are found near Northern Light Lake. But waters from the lake contained compounds from detergents and carbamazepine, a drug used to treat attention deficit disorder.

“Concentrations of contaminants in sediments appear to be much higher than the lake water at the same locations,” the agency said. “This suggests that these chemicals are accumulating over time in the lake sediment. More study is needed to determine the how persistent these chemicals are in sediment and to understand the impact of this accumulation to aquatic ecosystems.”

The findings add to a growing body of data about gender-benders in Minnesota waters, including a U.S. Geological Survey study described in September that found 73% of male smallmouth bass sampled in the Mississippi River downstream of the Twin Cities had intersex characteristics.

The Freshwater Society of Minnesota summarizes some highlights of 15 years of research on endocrine disrupters in the state.

A Minnesota state legislator who oversees some state environmental spending, Rep. Jean Wagenius, believes the PCA should be more aggressive in taking on both endocrine disrupters and nitrates in the state’s Mississippi River Basin while dealing with phosphorus pollution in the same waterways.

Deformed frogs first publicized in Minnesota waters in 1995 were suspected of being linked to endocrine disrupters, but no conclusive link was established.

Photo credit: Minnesota Pollution Control Agency.

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