RACHEL'S ENVIRONMENT & HEALTH WEEKLY #490
---April 19, 1996---
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OUR STOLEN FUTURE, PART 3: FLYING BLIND
Our Stolen Future, the new book on hormone-disrupting chemicals, provides many lessons about our use of chemicals, and about our reliance on science as a guide for public policy.
Here is a short discussion of the main lessons we find in the book (numbers inside parentheses are page numbers from the book):
- Genes are not destiny. Many people seem to think that we may be able to explain everything from cancer to homosexuality by locating the responsible genes. But in a series of scientific papers starting in 1980, Frederick vom Saal at University of Missouri demonstrated that there are other powerful forces shaping individuals--both females and males--before birth. Genes are not the whole story. Before birth, levels of both male and female sex hormones in the womb can affect the physical characteristics and the behavior of mice, giving rise to great variation in offspring that are genetically identical. By examining human twins, scientists have now revealed similar effects in humans. Thus we now know that hormones are a way that nature provides variation within a species. Profound variation among individuals can be caused by miniscule hormone differences in the womb, differences of a few parts per trillion. (One part per trillion is a million times lower than one part per million.) This is a degree of sensitivity to hormones that approaches the unfathomable, a sensitivity, vom Saal says, "beyond people's wildest imagination." This exquisite sensitivity provides rich opportunities for creating varied offspring from the same genetic stock. However, the dark side is that this same sensitivity also makes the reproductive system vulnerable to serious disruption if something interferes with normal hormone levels. (pgs. 39-41)
- The exposure of a million American women to the drug, DES, in the 1960s and 1970s showed that the human body could mistake a synthetic (human-created) chemical for a natural hormone. (pg. 66)
- Another lesson from the work of vom Saal and others is that hormones in the womb permanently program (and organize) cells, organs, the brain, and behavior prior to birth, in many ways determining an individual's course for life. (pgs. 39-40)
- The dose of hormones that an embryo receives is not the only thing that matters; the timing of the dose --when it occurs during development in the womb --can be as important as the dose itself. (pgs. 50-51)
- Birth defects may not be noticeable at birth. Serious effects of hormones on the unborn and on the newborn may not be recognizable for decades. (pg. 66)
- In fact, birth defects may never become visible at all, but may involve cellular damage that undermines an organism's ability to survive. For example, exposure to the drug DES, a synthetic hormone, gave rise to a rare form of cancer in female children of DES-exposed women. (pg. 66)
- Mice and humans share a common fate. To an astonishing degree, evolution has retained through hundreds of millions of years a basic strategy for embryonic development in vertebrates [creatures with a backbone] which depends on hormones. Regardless of whether the offspring is a human or a mouse, a whale or a bat, a turtle or an alligator, hormones regulate its development in fundamentally the same way. In the field of cancer research, scientists argue that data gathered from experiments on mice may not reveal anything useful about humans. This uncertainty occurs because the underlying causes of cancer are poorly understood. On the other hand, the working of hormones is better understood, and knowledge gained from experiments on non-humans can reveal useful information about humans. "It is important to take the effects we see in animals seriously," says Dr. Earl Gray, a senior research biologist with U.S. Environmental Protection Agency [EPA]. (pg. 66)
- Industrial chemicals at exceedingly low levels can combine together to produce additive effects. Dr. Ana Soto at Tufts University combined 10 hormone disrupters, each at one-tenth of the dose required to produce a minimal response; she found that the combination produced a response. Thus combinations of chemicals must be taken into account when we try to learn how much "effective exposure" we are getting to hormone-disrupting chemicals.
- Testing hormones at high doses may reveal no effects whereas testing the same hormones at low doses may reveal dramatic effects. This is contrary to the traditional assumptions of toxicology [study of poisons]. The dose-response curve for many hormones is U-shaped: at low doses, the hormones cause effects but at high doses the system becomes overwhelmed and shuts down. This has profound implications for testing. Traditionally, chemicals have been tested on laboratory animals at high doses; now we know that tests must be conducted at low doses as well. (pgs. 169-170)
- Up to now our concept of injury from toxic chemicals had focused on two things: (a) whether a chemical attacks the DNA inside cells, possibly causing cancer; or, (b) whether a chemical damages and kills cells, the way poisons do. However, hormone-disrupting chemicals may not kill or damage cells, and they may not damage DNA. Thus they do not fit the definition of "poisons" or "carcinogens" yet they may cause great harm by disrupting normal growth and development of many organs and tissues, including sex organs, the brain, the nervous system, and the immune system. The key concept in thinking about this kind of toxic assault is the disruption of chemical messages. (pgs. 203-204)
- The traditional approach to toxic chemicals is to look for disease as a result of exposure. However, hormone-disrupting chemicals may not cause "disease" at all: they may cause diminished function --reduced IQ, poorer short-term memory, diminished ability to pay attention, reduced sperm count. These are not signs of "disease" yet they are toxic effects that can be caused in some species by some hormone-disrupting chemicals. (pgs. 205-206)
- To screen for chemicals that cause diminished function, it will be necessary to look for developmental effects across three generations. The first generation (the generation that gets the initial exposures) may not be affected at all. The second generation may have diminished function (for example, diminished ability to reproduce) but the actual effects may not be apparent until the third generation (the grandchildren of the exposed generation). (pg. 207)
- We are flying blind. (pgs. 243, 246) We cannot know whether the ominous shape looming into view is a cloud bank or a mountain. If anything is certain, it is that we must expect more unpleasant surprises. We are flying blind; we can never know that new chemicals are safe (though, if we chose to, we could do a much more thorough job of testing them than we've done in the past).
To show that we are flying blind, Our Stolen Future relies on the evidence of hormone-disrupting chemicals and of depletion of the earth's ozone shield by human-created chemicals (see REHW #246, #259, #285). But there is much additional evidence that could have been cited as well. For example, during just the past 25 years, we have been surprised by:
- Global warming brought on by combustion of fossil fuels (REHW #467, #466);
- Mercury build-up to toxic levels in the bodies of fish (chiefly from burning coal, oil, and municipal solid waste) (REHW #291);
- Increasing birth defects in American children. Of 38 kinds of birth defects for which the Centers for Disease Control maintains records, 29 have increased during the past 20 years (REHW #410, #411);
- Steadily increasing cancers, particularly of the reproductive system (prostate; testicles; female breast) and nervous system (brain) (REHW #412, #447, #462);
- The astonishing toxicity of a family of chemicals called dioxins and furans (including some PCBs, or polychlorinated biphenyls), which now contaminate the entire planet from the depths of the oceans to the polar ice caps (REHW #390, #391, #414);
- The accelerated loss of species, which, according to the fossil record, is now occurring at rates 10 to 1000 times as fast as natural background rates that were occurring before humans appeared on the scene (REHW #441);
- Acid rain damaging lakes, killing trees, stunting forests, and washing nutrients from soils across much of the northeastern U.S., southern Canada, and northern Europe (REHW #476);
- Rapidly increasing immune system disorders such as asthma ( REHW #374) and diabetes (REHW #417);
- Epidemics of disease among marine mammals (seals, dolphins, etc.), apparently related to chemical contamination and to blooms of toxic algae caused by excesses of nutrients (chiefly nitrogen and phosphorus) in near-shore marine ecosystems (REHW #466);
- Diminished IQ and reduced ability to concentrate among 1.7 million American children and 300 to 400 thousand fetuses (at any given moment in time), as a result of exposures to the toxic metal, lead (REHW #369);
- Disappearance or decline of some frog and other amphibian populations worldwide (REHW #380, #441);
- Steep declines or near-total depletion of fish stocks at 13 of the world's 17 major fisheries (REHW #399).
- Decline of 50% in sperm among men in industrial countries (REHW #432, #446, #448), and a significant loss of sperm quality during the same period.
- A 60% increase in the rate of migraine headaches among Americans during the period 1980 to 1990. Most (71%) of the increase occurred among people aged less than 45 years.
This does not exhaust the evidence, but represents a fair sample of the kinds of problems that have suddenly loomed into view since 1970. Have we encountered the last of such unsuspected and unlooked-for problems? Certainly not. No, there doesn't seem to be any doubt about it: we are rushing forward at high speed with no sure way to learn what hazards lie ahead. We really are flying blind. To us, this seems the most important lesson of Our Stolen Future.
Under such circumstances, can science provide us with adequate guidance? Next week.
F. vom Saal and F. Bronson, "Sexual Characteristics of Adult Female Mice Are Correlated with Their Blood Testosterone Levels During Prenatal Development," Science Vol. 208 (1980), pgs. 597-599. And see: M. Clark and others, "Hormonally Mediated Inheritance of Acquired Characteristics in Mongolian Gerbils," Nature Vol. 364 (1993), pg. 712. Hormones have also been shown to affect humans exposed in the womb: D. McFadden, "A Masculinizing Effect on the Auditory Systems of Human Females Having Male Co-Twins," Proceedings Of The National Academy Of Science Vol. 90 (1993), pgs. 11900-11904.
Reported in Ana M. Soto and others, "The Pesticides Endosulfan, Toxaphene, and Dieldrin Have Estrogenic Effects on Human Estrogen-Sensitive Cells," Environmental Health Perspectives Vol. 102, No. 4 (April 1994), pgs. 380-383.
"Prevalence of chronic migraine headaches -United States, 1980-1989," Morbidity And Mortality Weekly Report Vol. 40, No. 20 (May 24, 1991), pgs. 331-333.
Descriptor terms: endocrine disrupters; hormones; our stolen future; des; diethylstilbestrol; frederick vom saal; ana soto; science; oceans; marine mammals; global warming; mercury; fish; wildlife; birth defects; cancer; dioxins; furans; pcbs; species loss; acid rain; lead; migraine headaches; theo colborn; john peterson myers; dianne dumanoski;
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--Peter Montague, Editor