the allegheny front

Endocrine Disruptors--The New DDT?

Tim Palucka

Air date: 04/04/2007

OPEN: While Rachel Carson was a pioneer in banning DDT, there are still a lot of other chemical compounds called endocrine disruptors that are causing environmental and health problems similar to DDT. A new batch of scientists has stepped up in the fight to ban these chemicals, but the going is rough. Tim Palucka spoke to a few of these scientists.

SOUND: A frog from Tyrone Hayes's lab.

PALUCKA: That's the mating call of a male African Clawed Frog in the laboratory of Dr. Tyrone Hayes, a professor of biology at the University of California, Berkeley. It's just one of many thousands of frogs Hayes has been studying over the years. He's looking at the effects that the common herbicide atrazine have on the endocrine systems of these frogs. Atrazine is the most widely used weed killer in the world. The results are not good.

HAYES: So, at a very low level it can disrupt hormones. It can make males and females express estrogen--the female hormone, inappropriately. In frogs that leads to hermaphroditism, it leads to genetic males with both ovaries and testes, it can lead to males that make eggs instead of sperm. And there's at least two epidemiological studies showing association between breast cancer and prostate cancer in humans exposed to atrazine.

PALUCKA: Atrazine is just one of many chemicals that are known as endocrine disruptors. The endocrine system is a set of glands, including the hypothalamus, pituitary, thyroid, adrenals, ovaries and testes. These glands release chemical messengers called hormones. They send information and instructions from one set of cells to another through the bloodstream. And they are remarkably similar among vertebrates.

HAYES: The hormones that we're looking at, thyroid hormone, estrogen, testosterone are chemically exactly the same. It doesn't matter if you're a fish a frog, a farmer, hog, dog, cat, rat for vertebrate animals they're all the same.

PALUCKA: For reasons not yet fully understood, atrazine mimics estrogen. Frogs that develop in waters contaminated with as little as a tenth of a part per billion of atrazine tend to become feminized. Take reed frogs for example. Normally green males develop the red color and white spots of the female, and have changes in the reproductive organs.

HAYES: Atrazine is important because it's ubiquitous. It's always there, it's persistent, it travels, it can travel up to 600 miles from where it was applied, a half million pounds come down in the rainwater every year in the United States.

NATURAL SOUNDS: Water running, geese honking, birds chirping.

PALUCKA: It's a misty spring morning at North Park Lake just outside of Pittsburgh. Dr. Dan Volz, a researcher at the University of Pittsburgh, studies the water and fish in the rivers and streams of Western Pennsylvania. Recent tests have detected atrazine in an Allegheny County watershed. And studies of fish caught in the Three Rivers of Pittsburgh are showing gender abnormalities similar to Hayes' frogs.

VOLZ: It was very difficult, especially in white bass and channel catfish, to be able to determine gender. Now why that is we don't know. Our working hypothesis right now is that it's because there are estrogenic chemicals in water.


PALUCKA: But you don't have to venture outside to find endocrine disruptors - you can go to your local grocery store.

SOUNDS: Inside a supermarket. Music, beeping cash register, shopping carts.

PALUCKA: Here, shoppers fill their baskets with everyday items like canned food, baby formula, and bottled water. Some researchers say it's these very products that expose people to compounds that interfere with hormones.

MYERS: Probably the poster child for that is a compound called bisphenol-A.

PALUCKA: That's Dr. Pete Myers, head of Environmental Health Sciences and co-author of the 1996 book on endocrine disruptors called 'Our Stolen Future.' Bisphenol-A is found in plastic polycarbonates that are used to line the inside of food and beverage cans and even cans of baby formula. He says a recent study by the watchdog organization, Environmental Working Group, found the compound leaches into food.

MYERS: They took a sample of 97 food cans from grocery stores around the country and measured the bisphenol-A levels in it, and they found disturbingly high levels, at least in some of the cans, and the most consistently high were in baby formula, which is not a good thing to find.

PALUCKA: Dr. Myers' knowledge of the dangers of bisphenol-A has led him to stop eating canned foods, especially because the link to prostate cancer.

MYERS: What they're learning is that exposure to levels of bisphenol-A that people experience are sufficient to speed the progression of that tumor along and make it unresponsive to medical treatment. We now know based on CDC data that 95% of Americans have bisphenol-A in them at levels that animal experiments tell us cause developmental harm. And there's a big fight underway, a fight that's as brutal as what Rachel Carson experienced, as public health scientists try to get control of that compound.

PALUCKA: The United States Environmental Protection Agency has a program to screen for endocrine disruptors since 1996, but many people, including Hayes and Myers, have criticized the program as ineffective. They say the program is compromised due to a mixture of politics and conflicts of interest. And Hayes says that there are excessive hoops to jump through to prove that a compound causes harm.

HAYES: In terms of protecting the environment and people, I say we go back to Rachel Carson. Because if you look at the EPA's model, DDT would still be on the market, because even today we don't know how DDT causes eggshell thinning. So she was ahead of her time, and I would argue that we've moved backwards.

PALUCKA: The EPA responded to these criticisms with a written statement. They said that they have been developing a set of scientifically rigorous tests to detect estrogen, androgen, and thyroid effects in both humans and wildlife. In the next few weeks, they will be issuing a list of 50 to 100 pesticide chemicals that will be subject to screening. Myers maintains a positive outlook on the ability to control endocrine disruptors.

MYERS: DDT is at much lower levels now than when Rachel Carson was fighting it, and its been lowered because society made a political decision that we're going to get that out based on science. So we can do it. We just have to be willing to accept the science and act upon it. That's where the fight is right now.

PALUCKA: For the Allegheny Front, I'm Tim Palucka.