What Do 'Intersex' Fish Mean for Water Quality?
IRA FLATOW, host:
This is TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.
First up this hour, a story that I'm sure is going to capture the attention of those men on Capitol Hill. Fish biologists working in the Potomac River say that up to as many as 100 percent of the male smallmouth bass that they have pulled from the water also had female sexual characteristics. They had eggs in their testes.
Scientists aren't exactly sure what's causing the intersex fish but they believe it's related to hormones in the water - either naturally occurring or synthetic hormones, such as those found in birth-control pills.
The intersex fish are just the latest example of how the products we use and flush down the toilet may be affecting aquatic animals. For example, scientists this week reported that the drug Prozac can interfere with the reproductive cycle of mussels. Other researchers have found that Prozac in the water can slow the growth of tadpoles. Can our pharmaceuticals and personal care products be causing harm to aquatic animals?
That's what we'll be talking about this hour. So give us a call, our number, 1-800-989-8255, 1-800-989-TALK. And as always you're invited to surf up to our Web site at sciencefriday.com, where you'll find links to our topics.
Vicki Blazer is a fish pathologist with the U.S. Geological Survey in Leetown, West Virginia. Thank you for being with us today, Dr. Blazer. [POST-BROADCAST CORRECTION: The correct name is Dr. Vicki Blazer.]
Dr. VICKI BLAZER (U.S. Geological Survey): You're welcome.
FLATOW: Tell us when you pull this fish from the water, is it obvious that the fish have both male and female sex characteristics?
Dr. BLAZER: No. They tend to look absolutely normal. You have to look at the gonads microscopically.
FLATOW: And tell us exactly when you look at them what you find there?
Dr. BLAZER: Basically, when you do pathology or histology, looking at slices of the gonad histologically - just what you said - we see immature eggs in the testes.
FLATOW: And is this something unprecedented?
Dr. BLAZER: No. Actually it's been reported in a number of places in the past 10 to 12 years. But as you said, we do believe its indication of exposure to some of these estrogen or estrogen-like compounds.
FLATOW: One of the things I found really amazing was the percentage, up to a hundred percent of smallmouth bass that you pulled out in some places.
Dr. BLAZER: Yes. And that was what was surprising, the high percentage. Small mouth bass seemed to be very sensitive to these chemicals.
FLATOW: Could you find it in any other fish, do you think, if you pull them out?
Dr. BLAZER: We have found that in largemouth bass in the same systems, but at a lower prevalence.
FLATOW: And you think what's causing these changes are these hormones in the water?
Dr. BLAZER: Well, either the hormones directly - estrogen comes from animals naturally. We excrete estrogen and other hormones. So it can be from agricultural, from human wastewater. But there are also a number of chemicals that act like estrogen. They bind to the same receptors. So some of the pesticides, herbicides, plasticizers, things like that can have estrogenic activities.
FLATOW: What made you decide to look at these fish for this?
Dr. BLAZER: Well, actually the reason we initially looked, we were not looking for intersex, there had been a fish kill of smallmouth bass in the south trench of the Potomac. And the state of West Virginia asked us to look at the fish to try to determine, you know, what caused the fish kill and what was going on healthwise with the fish. So in the process, we took pieces of all their organs and looked at them microscopically and that's when we found the intersex.
FLATOW: Now see if you can connect the dots for me, Dr. Blazer. How would you go from hormones in the water to the fish die off?
Dr. BLAZER: Well, we don't know that there's a direct correlation yet between the fish kills and the intersex but what we do know is that many of these chemicals that can cause intersex also affect the immune response. And so that's kind of where we're going from now with our research trying to determine is it the same mixture of chemicals that are making the fish more susceptible to bacteria and parasites that might be in the water and under normal circumstances wouldn't cause a problem.
FLATOW: Now, we should point that you're not studying the effect of the hormones in the water on people, correct?
Dr. BLAZER: No. We are not.
FLATOW: And there has not been any evidence to date that we know of that shows that it's affecting people who drink the water in the Potomac?
Dr. BLAZER: Not that I'm aware of.
FLATOW: Yeah. And does it mean that these fish then - if they become feminized, does that mean they can't mate with the other fish and then reproduce anymore?
Dr. BLAZER: Well, no. Actually, many of the male fish that we looked at in the spring did have sperm in the testes as well. What they found in Europe with a similar fish that they've been looking at for a number of years is that the intersex fish produce less sperm and that sperm is less motile. And so, you know, less successful at reproduction, but they still can reproduce.
Dr. BLAZER: Let me take a phone call or two. Our number 1-800-989-8255. Let's go to Joy in Perry, Florida. Hi, Joy, where is Perry?
JOY (Caller): Perry, Florida, is near Tallahassee.
FLATOW: Okay, go ahead.
JOY: Up in North Florida.
FLATOW: Beautiful spot.
JOY: We have a same sort of situation but a little bit different. We have a pulp mill here that uses chlorine in its processes, the Buckeye pulp mill and they dump their effluent into the Fenholloway River. And downstream from the mill, the scientists have been finding two species of mosquito fish who are changing sex, however it's the female fish taking on male sexual characteristics.
JOY: And they think that the chemicals from the mill are making - the chlorinated compounds, all kinds of dioxins and fluorines and organochlorines. And they are making these fish change sex because they act as endocrine disruptors for the fish.
FLATOW: Dr. Blazer, any reaction?
Dr. BLAZER: Yes. That has, I mean, that's a known effect of the pulp mills. And in this case, it's the androgen-like activity. So kind of going the other way.
FLATOW: Yeah. Do you think, Dr. Blazer, if we look hard enough we'll find many instances of these in lots of different kinds of aquatics?
Dr. BLAZER: Well, I do think what we found is that there is different sensitivity of fish species that we've looked at some other - we've looked for it in some other fish species. And so I think it depends on their sort of their lifestyle and whether they, you know, lay eggs in the sediment where some of this chemicals might be. Those sorts of things would affect sensitivity.
I do think that, you know, some of these things we just simply haven't looked for before and so we probably will find them in more places then we know right now they exist.
FLATOW: Thank you, Joy, have a good weekend.
JOY: Well, thank you. Let me say one more thing. The mill's effluent is also known to be contaminating the aquifer here and many people's wells. And so we are very concerned about that.
FLATOW: In the well water, it's going.
FLATOW: All right. Thanks for calling, Joy.
JOY: Thank you.
FLATOW: 1-800-989-8255. There was that story out this week about Prozac interfering with the reproductive cycle of mussels. Are you familiar with that, Dr. Blazer?
Dr. BLAZER: Just a little. I don't work on invertebrates. I am aware that they've been looking at that. We've also found Prozac, or at least some of the metabolites, in the brains of fish.
FLATOW: In fish?
Dr. BLAZER: Yep.
Dr. BLAZER: We don't know yet what that's about.
FLATOW: All kinds of images of very peaceful fish.
Dr. BLAZER: Exactly.
FLATOW: Now the fact that this happened in the Potomac or the tributaries of the Potomac and it affects male fish - feminizing male fish. Do you think the folks on Capitol Hill, who are mostly men, are perking up to this a little bit?
Dr. BLAZER: We can hope so.
FLATOW: Well, that's an interesting possibility as the story gets around that they - can you take it out of the water? Can it be - is it kind of the thing that can be taken out in a water treatment facility?
Dr. BLAZER: Well that's part of - yes. I think part of our interest in really trying to understand and document these things is once we find out what kind of chemicals that specific areas are causing it, then the hope would be that, you know, chemical engineers and other people can work on how do you take these things out of the water. Some can be removed simply by activated carbon. Others we, you know, we may have to go to other methodologies.
FLATOW: All right. Dr. Blazer, thank you for taking time to talk with us. And very interesting work. Good luck to you.
Dr. BLAZER: Thank you.
FLATOW: You're welcome. Have a good weekend. Dr. Vicki Blazer is a fish pathologist with the U.S. Geological Survey in Leetown, West Virginia.
NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.