In Utero Chemical Exposure Linked to Obesity
Endocrine disrupting chemicals, the ones that affect the way our bodies circulate hormones, are perhaps the most ubiquitous and the most dangerous of the pollutants we encounter each day. Research shows that even at low levels, these chemicals are affecting the way we develop and store fat. Host Steve Curwood talks with Dr. Pete Myers, head of Environmental Health Sciences, about the latest research.
CURWOOD: From the Jennifer and Ted Stanley Studios in Somerville, Massachusetts, this is Living on Earth. I'm Steve Curwood.
We are what we eat. Being fat or thin depends on what we eat, how much we eat, how much we exercise, and our genetic makeup, right? Well, scientists now say there may be another factor at work. Tiny amounts of synthetic chemicals found in the environment appear to play havoc with hormones that shape our bodies and behavior by turning genes on and off. These chemicals are called endocrine disrupters, and new research shows a link between them and setting the stage for obesity even before birth. Joining me is John Pete Myers. He's the Chief Scientist and founder of Environmental Health Sciences, and co-author of the book “Our Stolen Future,” which explores the science of endocrine disruption. Hello, sir.
MYERS: Hello, Steve, it’s great to be with you.
CURWOOD: So, how do you reconcile the notion that these disorders are linked to our genes, and yet you’re talking about chemicals in the environment?
MYERS: That’s a really good question, and it basically comes from an old understanding of what it means for a disease to be linked to a gene. For a long time we thought that that meant heredity. You got a gene from your parents, and it was a bad gene, and you got the disease.
But this new science – it’s been unfolding now for 30 years and it’s really, really taken off now – is saying you can have the right gene, but because of the environment it’s behaving in the wrong way. It could be diet that does it. It could be stress that does it. Or it could be an environmental contaminant. And so what we’re learning is turning on its head this whole notion of the separation between environment and genetics.
CURWOOD: Could you give us a “most wanted” list of endocrine-disrupting, that is, hormone-disrupting, chemicals, and where they’re found in our everyday lives?
MYERS: That list, the overall list is long. The “most wanted” list is a lot shorter. They basically fall into two categories. There’re the ones like DDT and PCBs, the polychlorinated biphenyls, that have been around a long time. Industrial chemicals, contaminants. There’s another category which are transient which degrade in the environment fairly rapidly, but because they are present in lots of consumer products, like cosmetics – lipstick, eye shadow, perfume – or, like, certain types of plastics, we’re exposed to them every day. So those are the two categories.
Now I think we’re learning that the perfluorinated compounds, things that are involved in the production of Teflon, are real problems. As are certain compounds used to make flame retardants, called the brominated flame retardants. At the top of the list of the transient compounds are the phthalates and bisphenol A, which is used to make polycarbonate plastic.
CURWOOD: Okay, so as a consumer where would I run into these chemicals?
MYERS: You’re going to run into them when you buy and use a bottle made out of polycarbonate, for example, the rigid, really popular sports bottles that virtually every college kid has. The way those are made guarantees that this compound called bisphenol A will leach into the water. And there’s a whole new generation of science that’s unfolded in the last ten years that has transformed what scientists understand about the risk of that chemical.
CURWOOD: Pete, could you tell us about the range of sicknesses that have been linked to the endocrine disrupters?
MYERS: Well, that list is really quite large. It runs from neurodevelopmental disorders, things like ADHD, attention hyperactivity disorder syndrome. Autism. Obesity. And a variety of problems having to do with weight regulation, what scientists call weight homeostasis. Diabetes. Problems of aging, what happens to people as they’re getting old. Definitely problems in infertility. And malfunctions in the immune system so that people wind up either with immune systems that are hyperactive and are involved in causing auto-immune disorders, or the opposite, immune systems that aren’t strong enough to help us resist the diseases that we normally would be able to resist.
CURWOOD: So, what’s the link now between the hormone disrupting chemicals that science is finding and this question of obesity? I figure that, you know, I’m kind of big around the middle because I don’t exercise enough and I probably eat too much.
MYERS: There’s no doubt, Steve, that those are problems. What our weight is clearly is affected by how much we eat and how much exercise we get. But think about it: we all know people who are tall and thin and eat like a horse and don’t put weight on, period. Or we know other people who, no matter how hard they try to limit their intake, they can’t lose weight. It turns out that in addition to the simple in and out, what you eat and how much you exercise, there are feedback systems at work in the body that balance weight. What this new science is telling us is there are things that can happen, especially in development in the womb, that appear to be having an effect on obesity.
CURWOOD: How much research has been done on this link between endocrine or hormone disrupters and obesity tendencies?
MYERS: Not a lot.
CURWOOD: Not a lot.
MYERS: Not nearly enough. We’ve got a small number of studies that are raising big questions, and because obesity is such a huge issue, this is a huge public health problem. And we’re getting some signals from the animal research that conditions in the womb can affect obesity.
Probably the most dramatic study of all of these has just been published within the last two months by a laboratory in Spain, and they looked at the effect of bisphenol A, this compound that comes out of polycarbonate plastic. They looked at it, and they created an experiment, they ran an experiment where they exposed adult mice to bisphenol A at a level that you can find in a lot of people, a lot of Americans. And what they found is that within four days those adult mice developed insulin resistance. They were no longer responding, their cells were no longer responding, properly to insulin.
Well, when insulin resistance develops in people, 25 percent of the people that get it go on to develop type 2 diabetes. It is the central piece of metabolic syndrome. So here you’ve got this animal result saying a contaminant that’s present in 95 percent of Americans at levels at which the experiments were run causes insulin resistance in mice. That’s a big signal, and the research community ought to be paying more attention to it.
CURWOOD: So, Dr. Myers, can you tell us some good news?
MYERS: Well, yes, Steve, I’m glad you asked that. Because at first encounter, this information is depressing, because it’s telling us that there are some contaminants in the environment that are interfering with gene expression at low levels, and that the science is suggesting it’s linked to a number of human health problems, serious problems. But at the same time, think of it this way: as these signals become sharper, clearer, we’re going to be in a position to reduce exposures. We’re going to be in a position to prevent diseases that until ten or 15 years ago many people wouldn’t have imagined were preventable. I think that’s really good news.
CURWOOD: John Peterson Myers is a biologist who’s the head of Environmental Health Sciences which publishes the Environmental Health News Service. Thanks so much for taking this time.
MYERS: Steve, it’s been a pleasure.
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