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Crossed Signals

When Theo Colburn's Our Stolen Future came out last year, many saw it as a sequel to Rachel Carson's classic Silent Spring . Since its publication, the book has played a central role in catalyzing an international debate on the threat of a new class of pollutants known as "endocrine-disrupting chemicals" (EDCs), dubbed "Gender Benders" in the press because one of their effects is to influence gender orientation in animals (the evidence is not yet decisive in humans).

While scientists are taking the debate regarding EDCs very seriously, media coverage of the health and environmental threats posed by EDCs has been amazingly deficient. Most of the press has focused on whether there is a global drop in human sperm counts and whether the micropenises of alligators exposed to EDCs in a Florida lake ("Why Female Alligators Are Snappy," said one headline) were an omen for men as well.

If the popular press missed the boat, the respected science writer Janet Raloff did not. She wrote in Science News Online:

"Bearing the clumsy moniker 'endocrine disruptors,' these pollutants including PCBs, DDT-breakdown products, dioxin and certain plasticizers can mimic or block the action of natural hormones.

"By inappropriately turning genes on or off, these compounds can elicit a range of adverse effects. In humans, they may foster cancer in the breast and other reproductive organs. Prenatal exposures appear capable of altering brain development with impacts on IQ and behavior that persist at least a decade, perhaps for life.

"Most surprising, in some exposed wildlife, creatures whose genes instruct them to be male matured into individuals that look and act like females. The newly recognized potential of these pollutants to wreak havoc in so many ways, together with their ubiquity, has given rise to a sense of humility among toxicologists. The compounds have been detected in pesticides, plastics, dental sealants, contraceptives, and dishwashing liquids, and they contaminate water, plants, wildlife, and foods."

Before EDCs, we used to worry most about toxic chemicals' increased cancer risk. The higher the dosage/exposure, the greater the cancer risk. The new research shows that EDCs have a wide range of serious health effects beyond cancer; that they cause these effects at infinitely lower levels than are necessary to cause cancer; that these effects are fundamentally intergenerational (the health effects are in our children and grandchildren).

Scientists have begun to refer to EDCs as signal disruptors or signal transducers because they misguide fetal development in many ways, both known and unknown. Principally, they disrupt fetal development by mimicking hormones, or hormone-like substances, that come from two sources: the fetus's genes and the mother's bloodstream.

Rethinking Risk Assessment

Even more troubling: the dose response curve for EDCs can go up and down in ways that confound traditional toxicology. Scientists call this a "non-monotonic dose response curve." That means EDCs can have different developmental effects at different windows of fetal development and at different doses. Extremely low doses in some developmental windows can end up causing worse effects than larger doses in other developmental windows.

One leading scientist, Frederick vom Saal, warned that these non-monotonic dose response curves are "the end of risk assessment as we know it." This alarm has government regulators and industry scientists tearing their hair out. "Risk assessment" represents the only "rational" way that government has been able to justify licensing companies to pour hazardous chemicals into the environment.

Classic risk assessment depends on dose response curves that theoretically allow scientists and regulators to assess population- or age-specific risks based on simple extrapolations of high-dose exposures. The classic experiment is to expose lab rats to a series of high doses and then extrapolate the curve downward, assuming that what you see in high doses can predict what happens at low doses. But if there is no known safe minimum dose for EDCs, and if they can have different effects at different doses and during different months of fetal development, the whole mechanism by which government licenses chemical companies to release chemicals doesn't make sense. The implications of no known safe minimum dose, for a petrochemically based global industrial system, are simply staggering.

Three additional complications have arisen: the endocrine-disrupting chemicals do not seem to be limited to a specific discrete class, the way DDT was, for example. It appears that a very wide range of synthetic chemicals may have endo-crine effects. Second, these effects may come both from persistent organic pollutants that are stored and concentrated in body tissue as well as from transient chemicals that may not store but may have profound health effects. Third, the effects of these chemicals may not be discrete but often additive or even synergistic. We currently test one chemical at a time; if, in reality, people are exposed to vast cocktails of these chemicals, this is a serious problem.

In short, many of us may already be "full up" of some persistent organic pollutants, including both chemicals that function as classic carcinogens and those that also function as EDCs. Millions of American people may carry in their bodies, right now, the levels of these chemicals at which, in other animal populations, scientists have seen pathological effects.

Non-human Indicators

EDC negative effects are far better demonstrated now in wildlife and experimental animals than humans. Industry scientists insist that we cannot generalize from animal effects to human effects. Yet some ecologists and physiologists counter that the endocrine system is quite similar across vertebrate species, involving the same principles and the same hormones. A growing number of independent scientists believe that the capacity to generalize concerns about EDCs across vertebrate species, including humans, is reasonable.

Since it is so difficult to conduct conclusive tests of EDCs on humans, and since so many human diseases do not have known benchmarks for incidence levels, Our Stolen Future (see review p. 80) suggests evaluating human health risks by a rough analogy: "If we know potential EDCs have specific serious health effects on animals, and we believe that the same effects might also occur in humans, what health problems would we look for in humans to see if they are increasing?" The expected health problems would include testicular cancer, endometriosis, intersex births, undescended testes, decreased fertility, learning and behavioral disorders, decreased resilience to stress, immune disorders, and neurological disorders. For a few conditions where we do have good benchmarks, notably testicular cancer, the statistical increase leads us to real concern. Clinical and anecdotal evidence has begun to confirm increased incidence of other health problems.

Hope and Public Health

Hope, the Czech playwright and statesman Vaclav Havel says, is different from optimism. It is an orientation of the human soul, and can spring forth within us even at the darkest times. At Commonweal, for many years, my coworkers and I have worked with adults with cancer and children with learning and behavior disorders. Both cancer and learning disabilities are epidemic in our time. Many scientists now suspect that EDCs may have a good deal to do with both epidemics.

These modern epidemics are deeply painful to all who suffer from them. I have listened to too many young mothers facing metastatic breast cancer, too many families agonized by dealing with learning disabilities, and too many friends seared by endometriosis and autoimmune diseases to accept this as just another horror story.

Historically, when health-affected people and their health professionals understood the threat of nuclear tests and smoking, we began to get action on those threats. What we have done as a first step is to challenge the silence and help start a national campaign, called Health Care without Harm, to get health professionals and health-affected lay people involved in warning the public about EDCs. We have started by trying to right a grievous wrong which is that the American healthcare system is one of the primary sources of public (and fetal) exposure to dioxin.

While we work with Health Care without Harm, other activists are working on a dozen other major sources of exposure to EDCs and other toxic fetal contaminants (see "Yellow Pages," p. 84). For the simple truth is that what is required to deal with EDCs is nothing less than a global environmental public health revolution, a fundamental transformation of the petrochemical backbone of modern industrial society.

Perhaps the most basic principle of that environmental public health revolution will be a precautionary principle: no synthetic chemical can be released into the environment until we are certain it is safe for mothers, babies, and all living beings.

I believe that as people begin to understand the true EDC threat to the health of our families, a global movement toward an environmental public health revolution like the nineteenth century public health revolution that controlled infectious disease with public hygiene is possible, and may even be inevitable. You don't have to be optimistic about our chances to make toxic-free babies and toxic-free bodies a human right. Ending slavery once seemed hopeless too. All you need is to hold hope as an orientation of your soul. Win or lose, fighting for the basic integrity of all life born of mothers seems to me to be the most interesting way to live.