Herbicides turn male frog into female frogs |
By Nicholas D. Kristof, The New York Times, May 2, 2012
Scientists are
observing with increasing alarm that some very common hormone-mimicking
chemicals can have grotesque effects.
A widely used herbicide acts as a female hormone and feminizes male
animals in the wild. Thus male frogs can have female organs, and
some male fish actually produce eggs. In a Florida lake contaminated by these
chemicals, male alligators have tiny penises.
These days there is also growing evidence linking this class of
chemicals to problems in humans. These include breast cancer, infertility, low
sperm counts, genital deformities, early menstruation and even diabetes and
obesity.
Philip Landrigan, a professor of pediatrics at
Mount Sinai School of Medicine, says that a congenital defect called
hypospadias — a misplacement of the urethra — is now twice as common among
newborn boys as it used to be. He suspects endocrine
disruptors, so called because they can wreak havoc with the
endocrine system that governs hormones.
Endocrine disruptors are everywhere. They’re
in thermal receipts that come out of gas pumps and A.T.M.’s. They’re in canned
foods, cosmetics, plastics and food packaging. Test your blood or urine, and
you’ll surely find them there, as well as in human breast milk and in cord
blood of newborn babies.
In this campaign year, we are bound to hear endless complaints about
excessive government regulation. But here’s an area where scientists are
increasingly critical of our government for its failure to tackle Big Chem and
regulate endocrine disruptors adequately.
Last month, the Endocrine Society, the leading association of
hormone experts, scolded the Food and Drug Administration for
its failure to ban bisphenol-A, a common endocrine disruptor known as BPA, from
food packaging. Last year, eight medical organizations representing genetics,
gynecology, urology and other fields made a joint call in Science magazine for tighter regulation of
endocrine disruptors.
Shouldn’t our government be as vigilant about threats in our grocery
stores as in the mountains of Afghanistan?
Researchers warn that endocrine disruptors can trigger hormonal
changes in the body that may not show up for decades. One called DES, a synthetic form of estrogen, was once
routinely given to pregnant women to prevent miscarriage or morning sickness,
and it did little harm to the women themselves. But it turned out to cause
vaginal cancer and breast cancer decades later in their daughters, so it is now
banned.
Scientists have long known the tiniest variations in hormone levels
influence fetal development. For example, a female twin is very slightly
masculinized if the other twin is a male, because she is exposed to some of his
hormones. Studies have found that these female twins, on average, end up
slightly more aggressive and sensation-seeking as adults but have lower rates
of eating disorders.
Now experts worry that endocrine disruptors have similar effects,
acting as hormones and swamping the delicate balance for fetuses in particular.
The latest initiative by scholars is a landmark 78-page analysis to be published next month in
Endocrine Reviews, the leading publication in the field.
“Fundamental changes in chemical testing and safety determination are
needed to protect human health,” the analysis declares. Linda S. Birnbaum, the nation’s chief
environmental scientist and toxicologist, endorsed the findings.
The article was written by a 12-member panel that spent three years
reviewing the evidence. It concluded that the nation’s safety system for
endocrine disruptors is broken.
“For several well-studied endocrine disruptors, I think it is fair to
say that we have enough data to conclude that these chemicals are not safe for
human populations,” said Laura Vandenberg, a Tufts University developmental biologist who
was the lead writer for the panel.
Worrying new research on the long-term effects of these chemicals is
constantly being published. One study found that pregnant women who have higher
levels of a common endocrine disruptor, PFOA, are three times as likely to have
daughters who grow up to be overweight. Yet PFOA is unavoidable. It is in
everything from microwave popcorn bags to carpet-cleaning solutions.
Big Chem says all this is sensationalist science. So far, it has
blocked strict regulation in the United States, even as Europe and Canada have adopted tighter controls on
endocrine disruptors.
Yes, there are uncertainties. But the scientists who know endocrine
disruptors best overwhelmingly are already taking steps to protect their
families. John Peterson Myers, chief scientist at
Environmental Health Sciences and a co-author of the new analysis, said that
his family had stopped buying canned food.
“We don’t microwave in plastic,” he added. “We don’t use pesticides in
our house. I refuse receipts whenever I can. My default request at the A.T.M.,
known to my bank, is ‘no receipt.’ I never ask for a receipt from a gas
station.”
I’m taking my cue from the experts, and I wish the Obama administration
would as well.
1 comment:
Post a Comment