Hillary Carpenter, a toxicologist, is the Minnesota Department of Health’s expert on endocrine disrupting compounds. He has doctorate in pharmacology, has written about EDCs for the Minnesota Medical Association and lectures on EDCs for an introductory toxicology course in the University of Minnesota’s Department of Environmental Health Sciences.
The Freshwater Society interviewed Carpenter about EDCs’ potential impacts on human health and the implications of environmental studies of their impact on fish. His responses, edited for brevity, follow:
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| Hillary Carpenter |
What are the major types of chemicals, and the types of products in which we find them, that contain EDCs?
Because of the fact that you can disrupt the endocrine system on so many levels, it’s entirely likely that any chemical that’s out there could be an EDC in one way or another. That’s why the U.S. Environmental Protection Agency plans to eventually test 80,000 chemicals. The ones that led to the legislation for the EPA to test EDCs are pesticides. Lots of pesticides are shown to be EDCs, as are pharmaceuticals, chemicals that are used in the plastics industry. EDCs are virtually everywhere.
Talk a bit about the history of proven impacts on human health of EDCs, starting with diethylstilbestrol.
That’s probably the only case where we’ve got a good argument for impacts on human health. DES is a synthetic estrogen that was developed to stimulate growth in cattle. DES, which was given as a pharmaceutical in very large doses, had impacts that were not predicted.
The major impact was discovered in New York City where DES was given to thousands and thousands of women. The female offspring of moms who received DES as therapy to prevent spontaneous abortions ended up with a higher incidence of clear cell vaginal carcinoma, an incredibly rare form of cancer. That’s what started the study that ultimately showed DES had the ability in impact offspring in ways that weren’t apparent until puberty.
What is the Health Department doing to research and regulate EDCs?
We really don’t regulate EDCs. That’s not happening at any level. What’s happening is everyone is waiting for the U.S. EPA to get their program started with the EDC screening program and use that information to potentially regulate EDCs.
Lots has been written lately suggesting EDCs cause a string of human ailments: Decreased sperm counts in men, an increase in urinary birth defects in boys, increased rates of obesity, diabetes and testicular cancer. Do you believe those cause-and-effect linkages exist? Have they been proven?
They have not been proven in humans. What we’re talking about here is the field of epidemiology and that is the discipline that establishes associations. It is not really designed to determine cause and effect. Most of the epidemiology that’s been done is retrospective, working backward. It’s a hypothesis-generating mechanism. The National Academy of Sciences in 1999 talked about a number of these issues, and these scientists reached the consensus that, based on the information that was available to date, it wasn’t possible to say there was a cause and effect.
In June of this year, the Endocrine Society, an international organization devoted to research on hormones and the clinical practice of endocrinology, labeled EDCs a “significant concern to public health.” The society cited “evidence that endocrine disruptors have effects on male and female reproduction, breast development and cancer, prostate cancer, neuroendocrinology, thyroid, metabolism and obesity…” How important is that statement?
I think it will stimulate a lot of people and cause some concern, but I think if you go back and look at the original stuff, there are a lot of mays and mights and coulds, which people tend not to see. Scientists are not saying we know exposure to this chemical causes this. I think what the Endocrine Society is saying is: “Look, folks, this is a cause for concern.” We’ve got a considerable amount of animal data that’s available, an increased amount of experimental data that’s available, and all of it indicates that there is a cause for concern or caution.
There has been a lot research in Minnesota -completed, under way and proposed-on the presence of EDCs in effluent from wastewater treatment plants, and on the effects of EDCs on fish living in that effluent. What is the connection of that research to human health?
It indicates the potential for exposure, and the whole issue of EDCs in my mind always goes back to the idea of exposure. Environmental exposures are being reported in rivers and wastewater effluent. It’s a different kind of exposure than humans are facing. Fish and invertebrates that live in those waters are exposed on a 24-hour, seven-days-a-week basis, and that’s not the kind of exposure you see with humans. The real big question is: How do you extrapolate that into a public health issue? And you can’t really do that until you start talking about what the levels in that wastewater mean to potential exposure to humans.
How do you think most Americans are most exposed to EDCs?
Americans are exposed to EDCs on a regular basis from all kinds of sources – air, water, food. There are a lot of EDCs in plant materials and people who eat a lot of vegetables are eating phytoestrogens. We’re exposed with the cosmetics we use, some of the pharmaceuticals we take. We take birth control, and that’s an EDC. The exposure to these chemicals is ongoing. The bottom line becomes: What are the levels of exposure, and are we getting exposed to concentrations of these chemicals where we would expect to see responses?
Are we put at risk by swimming in or drinking the water from the Mississippi and other rivers where EDCs have been found in concentrations that are very small, but apparently big enough to cause feminization of male fish?
I think it’s unlikely because the exposure is going to very different. The thing you need to remember again is that the fish are in that water for an extended period of time, some of them a lifetime. Their exposure would be much higher than for a human.
These compounds almost always are found at very low concentrations: parts per billion or parts per trillion. But the Endocrine Society said “even infinitesimally low levels of exposure, indeed, any level of exposure at all-may cause endocrine or reproductive abnormalities.” And it also said that sometimes low doses “exert more potent effects than higher doses.” So how can we possibly know what’s safe and what’s not?
You can’t. A lot of what’s going on with the EDC issue right now is at the basis of toxicology as a discipline. Toxicologists don’t think in terms of low doses, and the EDC issue is making people rethink how they design experiments. We live in a dose-response world. The higher the dose the bigger the impact. It’s clear now that toxicological tenet is no longer true. We have to take a timing component into it. And the Endocrine Society is talking about development-that if you’re exposed to small amount of material at a critical time during development-you might see an impact that wouldn’t be apparent at any other time of life. It’s forcing us to think about chemicals differently and think about potential exposures early in development vs. adult exposures.