Scientists believe effects can extend to two generations
By Douglas Fischer, STAFF WRITER
SAN FRANCISCO — Your ability to reproduce — and the health of your child and even your grandchildren — hinges on an exquisitely timed series of chemical reactions controlled by infinitesimally tiny amounts of hormones.
You scramble those reactions at your peril, in other words, and last week hundreds of researchers gathered at the University of California, San Francisco, warned society may be doing exactly that with synthetic chemicals.
The chemicals, known as endocrine disrupters, are found everywhere in our environment: our food, lotions, shampoos, baby bottles, toys, appliances, even the casings encapsulating our medicines. They mimic hormones at levels scientists only recently have been able to measure, and some are active at concentrations of a part-per-trillion or less — a speck of dirt sullying 55tons of clean laundry.
Most worrisome to scientists: In many cases the effect of such pollution on our bodies remains as mysterious as the processes they potentially disrupt.
"In the absence of concrete data for many of these chemicals, the precautionary principle should be exercised," said Dr. Linda Guidice,chairwoman of obstetrics, gynecology and reproductive sciences at UCSF and the organizer of the reproductive health conference that brought 500 scientists, clinicians and community activists together last week.
The list of potential effects, scientists concluded, stretches across every aspect of reproductive and sexual development — preconception, conception, pregnancy, puberty, menstruation, menopause.
Every key developmental stage is driven by a tightly choreographed fluctuation in hormones. A flood of endocrine disrupters, scientists fear, obviates that dance.
For those suffering from endometriosis, there's no need to imagine.
Wendy Botwin of Oakland was 18 when she felt the first signs: mysterious sickness, massive abdominal pain, irregular periods, crushing headaches, painful sex. Two-and-a-half years passed before a doctor diagnosed endometriosis, a debilitating disease where the tissue lining the uterus appears outside the womb in other parts of the body.
Today, at 37, Botwin has been on every type of birth control pill, been advised to get pregnant (she may be infertile) and to have a hysterectomy. One drug sent her into menopause, at age 21.
Nothing has worked.
She feels certain something in the environment has triggered this. Her father died at 62 of stomach cancer. Her younger sister last year was diagnosed with thyroid cancer. She feels, she said, very much like a canary in a coal mine.
"I know we've polluted our bodies and the Earth," she said. "The environment is really inside of our bodies. It's not just outside."
The science of endocrine disrupters is still controversial. The effects in humans are uncertain. Government panels assessing the weight of the evidence for many of these compounds repeatedly have found no need for concern. But scientists say disturbing gaps remain in our knowledge.
- Several studies have shown pesticides suppress fetal testosterone in laboratory animals. But scientists can't fully explain the consequence. They don't even know the role testosterone plays in a baby boy's brain development.
- The womb was once thought of as a gatekeeper, shielding the developing baby from harm. No more. A number of contaminants readily traverse the placenta, and others — synthetic fragrances, for one — are thought to hold the door open, so to speak.
- Female mice exposed in utero to bisphenol-A, a estrogenic additive used to line food cans and make plastic shatterproof, among other things, saw a 40percent increase in chromosomally abnormal eggs, according to one research team.
But this is where the science gets murky. In November a European panel investigating the effects of bisphenol-A concluded levels found in the environment pose no threat to our health, despite findings such as Hunt's.
Why? Mice and humans process bisphenol-A differently, the panel said.
Mice recirculate the compound and appear to be particularly sensitive to such weak estrogens. Humans, in contrast, rapidly transform bisphenol-A in the gut into a compound devoid of hormonal activity, then pass it via urine.
Such differences, according to the European Food Safety Administration, "raise considerable doubts about the relevance of any low-dose observations in rodents for humans."
There's another example out there, however: DES, or diethylstilbestrol, a wonder drug given with the best of intentions from the 1940s to the 1970s to pregnant women prone to miscarriage.
The mothers did fine, but DES ravaged the reproductive tracts of their children.
DES did its damage, scientists now know, because it turned hormones on at a time during fetal development when they would normally be silent. That, researchers say, is exactly what bisphenol-A and a soup of other endocrine-disrupting compounds do.
Sandra Steingraber, a noted ecologist, author and cancer survivor, echoed Botwin's thoughts on the environment and endometriosis as she told scientists of her experience being pregnant with her daughter, Faith.
"We need to start thinking of our reproductive lives as a live musical performance. Our bodies are the piano, but the hands are the environment," she said. "We are nothing less than the receivers of environmental messages. As that message changes, we are changing ourselves."