Evidence accumulates that manmade chemicals, known as endocrine disruptors, are causing abnormal mutations in marine creatures. Does that mean they're having an impact on human health?
U.S. Geological Survey
What was it that triggered your research on the fish up in these rivers above the Potomac?
We were requested by the West Virginia Department of Natural Resources [DNR] to take a look at some fish. There had been a major kill of primarily smallmouth bass in the South Branch of the Potomac in the spring of 2002. We actually didn't get involved until the summer, but there continued to be lesions and fishermen concerned about the issue. So we went out with DNR basically to collect some fish and look at the skin lesions to determine if we could find out what the cause was. ...
And what did you find?
A lot of different things: Some fish had bacterial lesions; some fish had fungal lesions; some fish had parasites. So we didn't find any specific cause. ... To me that suggested that the fish were immunosuppressed, and so that anything that was in the water as what we would call an opportunistic pathogen could attack them and cause those lesions. ...
Could you point to anything that would have caused that? What was your idea? ...
Our first idea was that it was probably some kind of chemical contamination. That's something we worked on for years as far as looking at specific contaminants and how that affects the immune response, or disease resistance, of fish. So, what we suggested was that we go out the following year, in the spring, when this problem had occurred, and collect fish at a number of different areas and really look in detail, not just at the skin lesions but at all the organs, to try to find signs of some kind of chemical exposure. ...
One of the major and most interesting findings was intersex in the male bass, which is not something you can see grossly, just looking at the fish. But when we look at it microscopically, or histologically, when we look at the male gonads, or testes, what we find is immature eggs within the male testes.
So you got a sort of feminization of male fish. Is that a big, alarming finding?
Yes. It's something that people have been recognizing for a number of years. ...
Is there any connection between the bad effects in the fish and human activity?
With the intersex issue, since we've been looking at it for quite a few years now, we've moved from just looking at the South Branch of the Potomac, which is a fairly sparsely populated area, but there is a lot of agriculture, and there is some industry. We've looked at a number of areas to sort of try to tease that out. We've been looking at the Shenandoah, because there's been major fish kills there as well. That's a more heavily populated area, also more ag, and we actually find a higher prevalence of intersex in the Shenandoah than we do in the South Branch. ... So we do think that there is a gradation, and it is associated with both human population density as well as agriculture. ...
[What kind of chemical compounds were you associating with the intersex?]
When we first discovered the intersex, we went into the literature and looked at what are the things that have been reported to cause that in other fish species. And estrogen -- natural estrogen, as well as the synthetic estrogens that are used, for instance, in birth control pills and estrogen replacement, are two primary ones. But then there's a whole group of compounds that can be what we call estrogen mimics. In other words, because of their structure, they can act like estrogen, and those include some of the pesticides, herbicides, things like nonylphenol.
How big a range of products are we talking here? ...
... Personal care products, some of the antimicrobials that are in those, as well as the fragrances, have been shown to have what we call weak estrogenic activity. But together they can cause some of these things. ...
Part of the problem of trying to identify specific chemicals, or even groups of chemicals, is just that [the range] is so large, and so many of these things act at very low concentrations. And so even getting the methods to measure them in the water at those low concentrations is something that's just developing, which is why we refer to this as an emerging-contaminants issue. These are contaminants we're just beginning to recognize can have serious effects. ...
Are [the fish] the canary in the coalmine for human beings in terms of potential health dangers?
To me, they're certainly the canary in the coalmine as far as ecological damage. How that will directly relate to human health still needs to be determined. In other words, the fish are constantly swimming in that water. ... People aren't necessarily constantly in the water. They may not directly be drinking that water, so how that relates specifically to human health is a whole 'nother step we need to take.
Director, National Institute of Environmental Health Sciences
Our endocrine system is very important to our maintaining our normal bodily functions, and at different points in our life, our hormones interact very much to allow us to develop, to grow, to go through puberty, then to go on to have children and so on.
What we're finding is that chemicals that can disrupt or modify or perturb this endocrine system in a variety of ways can cause effects on reproduction, on development, on the developing nervous system; can be associated with the increased incidences of cancer; can affect our immune system.
The function of the endocrine system is to integrate our body. In the endocrine system, one part or one tissue or cell in our body talks to another tissue, and if you interrupt that communication, if you cause too much communication, too little communication, wrong communication, we're not going to function well.
We've been out with [USGS fish pathologist] Vicki Blazer. ... She's shown us problems with lesions on fish livers, and then she's shown us the intersex, the eggs and the male gonads. She and others talk about this as an effective endocrine disruptor. Is that a fairly broadly accepted notion?
Yes. For example, we've known for a number of years that if you look at fish that are present where sewage flows into a river, you'll see this imposex, [the imposition of male sex characteristics on female organisms]. That was first reported in the Thames in London a number of years ago. We know that, for example, in certain bodies of waters that were highly contaminated by PCBs and other organic pesticides in the past, we saw changes in their liver or changes in their thyroid gland. ... So yes, some of these are clearly effects of disturbances of the endocrine system. ...
But it's very hard often to see these effects in people, because some of the effects we're talking about are relatively subtle, or the term clinicians might use is "subclinical."
To use lead as the simplest example that most people understand, I couldn't say, "Gee, if you had a little less blood lead, you'd have two more IQ points." But you can look at a population of children and see that the population has lower IQs than populations without that amount of lead. And it's the same kind of thing with much endocrine disruption. It's hard to pick up effects in the individual; you can pick them up in the population. ...
... What have large epidemiological studies shown about endocrine disruptors and their impact on human health?
There's some evidence for associations. It's very difficult to prove causation. We're not going to intentionally expose people to these chemicals, but we can show that people with higher levels of some of these chemicals may have a higher incidence of a certain kind of effect than people with lower levels of these chemicals.
Like what kind of effect?
Some of the effects that have been reported are with certain of these persistent organic chemicals. There are associations with what's called male testicular dysgenesis syndrome. That's a big term, but it means --
Lower sperm count?
-- lower sperm count; increases in hypospadias, increases in cryptorchidism, which is undescended testicles. ... These are male problems with the male reproductive tract that are caused by exposure very early in life, probably in utero.
Exposure to what?
Exposure to a number of different kinds of chemicals that may either mimic estrogen, so it's like too much estrogen, or it may be blocking the androgen system. Our body has a very, very fine balance between the levels of androgens and the levels of estrogen, and if you upset the balance, you can have adverse effects. So that's just one example. ...
We know that developmentally, the thyroid hormones being at the appropriate level are absolutely essential for normal brain development. And yet we're finding that certain chemicals like PCBs and now the flame retardants -- there are reports of their being associated with alterations in the normal level of circulating thyroid hormones. ...
We know that endocrine disruptors can cause adverse effects in human populations, and we know that from the studies of certain drug situations. DES, which was used from the '50s through the early '70s to prevent miscarriage, was associated with adenocarcinoma, a kind of very rare vaginal cancer in young girls. DES also causes in women who took it when they are postmenopausal an increase in breast cancer, and appears to be causing an increase in breast cancer in the DES daughters. It appears to be causing effects in the DES sons. Many of these effects we would never have noticed or known about had it not caused this very rare cancer in young women.
So the point that I'm making is you kind of have to look. Otherwise you don't see these things.
Robert Lawrence, M.D.
Johns Hopkins School of Public Health
How seriously should we take the threat to our health of endocrine disruptors in our drinking water, in the water that the fish we eat swim in, or where we bathe ourselves?
Endocrine disruptors are very, very potent chemicals at infinitesimally small quantification. You're talking about parts per million or parts per billion. These chemicals enter the body through the drinking water, sometimes through the food supply, less likely through the air we breathe, and then they tinker with the body's mechanics. They interrupt the normal way in which the body controls everything from growth and development to thyroid function to reproductive function to estrogen levels, testosterone levels.
So they're very, very important, and they are of deep concern because there are so many of them now. ... Serious things can happen, and they can go over generations. ...
I'm not quite clear exactly what the risk is. Are we facing a long-term, slow-motion risk that we don't recognize because it's not readily apparent?
We are. The long-term, slow-motion risk is already being spelled out in epidemiologic data, large population studies that show that some of these endocrine disruptors are increasing; for example, the rate of hypospadias. Hypospadias is a congenital anomaly in male infants where the urethra leaves the body before it gets to the end of the penis, so that the actual opening of the urethra where the urine comes out is closer to the base of the penis or maybe even back around the scrotal sac. We're seeing increasing numbers of infants born with that anomaly steadily increasing over the last 20 or 30 years, and the culprit is almost certainly one of these endocrine disruptors, or maybe a combination of them. ...
[Where do the endocrine disruptors come from?]
The endocrine disruptors could come from agriculture, from industry, from home lawn care products, from all of the things that we tend to be using without adequate regulation.
The Clean Water Act really focused in on acceptable levels of bacteria and viruses and parasites. It did nothing about acceptable levels, if there is such a thing, of these organic compounds that are mostly manmade. ...
We have literally tens of thousands of chemicals in regular use, being produced sometimes in the millions of pounds, that we do not know enough about in terms of their human safety or the safety to the ecosystem.
When you see scientists like [USGS fish pathologist] Vicki Blazer cutting open fish, finding intersex in the male fish, seeing high levels of fish kills, seeing immune systems disrupted, seeing other damage to the fish, is that a warning to you, potentially, about human health?
Oh, absolutely. The warning, not just from the smallmouth bass in the Potomac but from amphibians all across the country -- particularly in the Central Valley in California where atrazine is so commonly used, you have frogs with six legs, hermaphroditic frogs, male frogs with ovaries, female frogs with male genitalia -- these are the modern canary in the mine that we haven't been paying enough attention to.