Scientists are continuing to sound the alarm about some common chemicals, including the herbicide atrazine. So, what is Atrazine?
Atrazine is used to stop pre- and post-emergence broadleaf and grassy weeds in major crops. The compound is both effective and inexpensive, and thus is well-suited to production systems with very narrow profit margins, as is often the case with maize. Atrazine is the most widely used herbicide in conservation tillage systems, which are designed to prevent soil erosion.
Its use is controversial due to widespread contamination in drinking water and its associations with birth defects, menstrual problems, and cancer when consumed by humans at concentrations below government standards.[1] Although it has been excluded from a re-registration process in the European Union,[2] it is still one of the most widely used herbicides in the world.
Highlights from the endocrine disruptor interview:
AHERN: To explain what he meant by "feminized" Hayes brought me back to his office and pulled up a picture on his laptop of a frog that had been exposed to the herbicide.
HAYES: This is an animal that looked like a female on the outside. But on the inside it had large testis, so these are testis, and this is an oviduct. So, this is the equivalent of a man with a uterus.
AHEARN: These frogs aren't just behaving like females – they're actually producing eggs and when those eggs are fertilized by normal male frogs, the babies grow up to be seemingly normal frogs. Let me say that again: the male frogs are having babies. And there are consequences. HAYES: ...because they don't have a female chromosome the females that are genetically males can only produce other males so 100 percent of their offspring would be males.
AHEARN: And more male frogs means fewer babies down the road. Hayes says this might be one reason that populations of frogs and other amphibians all over the world are going down.
AHEARN: The reproductive problems Hayes is seeing in his specimens aren't limited to frogs. Studies on rats, reptiles and even human cells exposed to atrazine showed similar results. Recently, scientists with the U.S. Geological Survey found intersex fish in one third of the waterways they tested across the United States.
And atrazine is not the only chemical to blame for causing widespread reproductive health problems. It's a member of a family of chemicals known as endocrine disruptors.
COLBORN: They're in plastics. They're in our toys, the children's toys. If you go to your kitchen sink and under your bathroom sink and look at the cleaning compounds that are there. The cosmetics. The toiletries. They're just about in everything because they've made every one of these products much nicer. They last longer. They're preservatives. They're fire retardants.
AHEARN: The endocrine system is made up of a series of glands throughout the body that control the hormonal messages that direct development. By imitating natural hormones– such as estrogen and androgen – endocrine disrupting chemicals prevent the body from sending and receiving those messages. Dr. Stephen Rosenthal, a pediatric endocrinologist at the University of California San Francisco, broke down some basic human developmental biology for me. He says in the womb, we all start out developing as girls.
ROSENTHAL: If you consider the gonads, which basically is the other name for the testis or the ovaries, in any baby - either boy or a girl – that, basically, these gonads are pre-programmed to become ovaries unless there's an overriding signal that tells them to become testis.
AHEARN: If you're a boy that over-riding signal comes from a gene on your Y-chromosome. It tells your gonads to become testis, instead of ovaries, and to start producing testosterone and androgen. Those hormones then travel through the body and hook up with receptors in cells.
ROSENTHAL: That sets off a chain of events inside a cell. It's like if you need a key and an ignition to start a car right, so the key goes into the ignition and then the whole thing can turn and the car goes on.
AHEARN: The car "going on" would equate to normal development of a fetus. Now picture some chewing gum in the ignition. The key won't fit. The car won't start – or, as Rosenthal explains - normal masculine development won't proceed.
ROSENTHAL: If there is some agent, some environmental disruptor that interferes with the normal functioning of the Androgen Receptor then it's very likely that in a male there will be incomplete masculinization of the external genitalia.
HAYES: People go, well, it's frogs. I go, yeah but look, the estrogen that works in this frog is exactly, chemically exactly, the same as the estrogen that regulates female reproduction. Exactly the same testosterone that's in these frogs regulating their larynx or their voice box or their breeding glands or their sperm count is exactly the same hormone in rats and in us.
AHEARN: So, what about us? Could endocrine disruptors be having feminizing effects in humans?
AHEARN: Talking about problems with reproductive health is something society has never handled well. And perhaps because most hypospadias can be corrected with surgery, very few doctors have raised questions about the underlying causes of this birth defect.
But endocrine disrupting chemicals show up in almost 100 percent of the population, according to the Centers for Disease Control, and many of these chemicals are known to disrupt normal reproductive system development in animals - think back to Tyrone Hayes' frogs here.
So I asked Dr. Theo Colborn, who's been studying endocrine disruptors for over 30 years, if she thought our environmental exposures could be affecting our reproductive health. Or more specifically, given what we're seeing with hypospadias, I asked her, do you think we are feminizing our baby boys?
COLBORN: I definitely do. I think there's a certain percentage that are definitely being affected and there's no denying it.
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