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Endocrine Disruptors and Intersex Fish in Minnesota Lakes

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Endocrine disrupting chemicals were identified in all of the 11 Minnesota lakes studied by the U.S. Geological Survey, St. Cloud State University and the Minnesota Pollution Control Agency. Female characteristics were observed in male fish in most of the lakes studied. USGS scientists Jeffrey Writer talks to us about what's going on. 




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[Intro Music]

Jennifer LaVista:  Hello and welcome to the USGS CoreCast. I'm Jennifer LaVista. Endocrine disrupting chemicals are usually associated with waste water treatment plant discharges, which feed into rivers and streams. However, now these chemicals have been identified in 11 Minnesota lakes. All of which contain male fish that display female characteristics or intersex. To help us understand what's going on. I'm here with the USGS Scientist, Jeff Writer. Jeff thanks for joining us.

Jeff Writer:  It's my pleasure to be here.

Jennifer LaVista:  Now first can you briefly tell me a little bit about these lakes? Where are they located?

Jeff Writer:  These lakes are located in, they're pretty broad ranged across Minnesota. We selected both urban lakes, agricultural lakes, as well as lakes that we felt were fairly remote and wouldn't be heavily impacted from anthropogenic sources.

Jennifer LaVista:  So they're spread all across the state?

Jeff Writer:  That's correct.

Jennifer LaVista:  What sort of chemicals did you guys find in these lakes?01:00Jeff Writer:  Well we'd looked at a wide range of compounds and these were specifically looking at endocrine disruption, we targeted specific classes including the steroidal hormones, which include estrogen and testosterone that are released by all vertebrates. Additionally we'd looked at bisphenol A, which is a plasticizer and is found in a huge array of common consumer products, plastics. It can be found in various types of lotions, etc. 

We also looked at classic compounds called alkylphenols and those are commonly found in cleaning products. I think in all we ended up looking at over a hundred different elements.

Jennifer LaVista:  And were the levels of these elements pretty high?

Jeff Writer:  No they're all very, very low. Even though we're saying these at very, very low concentrations, they can elicit a response in an aquatic organism.

Jennifer LaVista:  So are you finding more of these chemicals in urban and agricultural areas?

Jeff Writer:  That was what we initially thought we would find and to some extent that was true. We did find generally higher concentrations of these compounds in the urban areas and then in some instances in some of the agricultural lakes.02:07But what really surprised us is we did find in some of these lakes that are up near the northern border of Minnesota. We found concentrations of these compounds that you wouldn't necessarily expect. So one of the key findings of the study is that there's no such thing as a pristine lake anymore pretty much anywhere you go. I mean it's, that even though these are low concentrations we have people that are visiting these lakes. We have agricultural activities that are going on nearby and because of that we tend to carry these products that we use all the time into these remote settings.

Jennifer LaVista:  So let's talk a little bit about the fish. I understand that female characteristics were present in both resident fish and fish that were placed in the lake for 21 days. Should residents who may fish or swim in these waters be concerned about this?

Jeff Writer:  Um, no. These concentrations we're finding are, have parts per chilling concentrations. So they are very, very low concentrations and the mechanism of assimilation that these fish are getting exposed, they were totally different than what a swimmer is going to be exposed to.03:10So the concern is not really from a human health perspective at this point. 

Jennifer LaVista:  So what percent of these male fish in these lakes showed signs of intersex?

Jeff Writer:  Well it was really a small proportion, probably less than about 10% depending on each lake. But still we felt that it was significant when you see these levels of intersex. Now whether or not that is coming from natural sources because you know it is a characteristic of fish that they had time, you can't have intersex. So it's hard to really draw the direct relationship between we see these compounds and we have intersex in these lakes.

Jennifer LaVista:  So right now it's a possibility but there's further studies needed to find out if there's a correlation?

Jeff Writer:  Absolutely and that's one of the things that we're doing this summer. We've decided to focus on one of the lakes that we studied in this initial study and that's solvent-like. And what we're doing is we're trying to look more closely at what's going on, not only looking temporarily so over different points of time. We're going to sample in the summer, in the fall, and then the winter.04:08But we're also going to look at different spatial locations within this lake so, and see if we can isolate some of the potential sources.

Jennifer LaVista:  Now Jeff is there anything else you would like to add?

Jeff Writer:  You know, I think if people are interested in this and they want to take a look at some of the work we've done here at the USGS to get a better idea of not only our work in Minnesota but our work around the country in trying to understand exposure and aquatic effects and potential human health effects of these trace level compounds, they should go the USGS Toxics Hydrology website and there is links through all sorts of different studies that our organization is doing.

Jennifer LaVista:  Excellent. Thanks so much for shedding some light on this subject.

Jeff Writer:  Thank you Jennifer.

Jennifer LaVista:  And thanks to all of you for listening. CoreCast is a product of the US Geological Survey Department of the Interior. I'm Jennifer LaVista.

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