“Our Stolen Future,” by Theo Colborn, Dianne Dumanoski, and John Peterson Myers.
Hand-Me-Down Poisons Excerpt
Gilbertson had given Colborn complete access to his meticulously organized collection of material on each animal species that breeds in the Great Lakes basin–data that he had gathered over the years and arranged in chronological order in three-ring binders. Colborn was awed by the elegance of the effort and by the years of dedication and scholarly consideration that it reflected. With a sense of history, Gilbertson had gone to great lengths to collect papers and studies dating back a half century or more–literature documenting that the problems seen today in the birds and wildlife along the lakes had not been reported before World War II. In the bald eagle file, she found evidence of parallel declines in the postwar period in the bald eagle in North America and in its European cousin, the white-tailed sea eagle, along with a collection of reports detailing the concentrations of synthetic chemical contaminants found in both species. Photocopies from Gilbertson’s archive had greatly enriched Colborn’s files, but their conversations, during which Gilbertson generously shared his broad experience, had proven even more valuable.
Over lunch in the Canadian Wildlife Service cafeteria, Colborn, Gilbertson, and Fox had discussed the wildlife evidence contradicting the frequent claims that the lakes had been cleaned up. The two Canadians shared the conviction the wildlife work had likely implications for human health and constituted a warning humans ought to heed. In her survey of the scientific literature, Colborn had been fascinated by some of Fox’s work, which reported evidence of behavioral changes in wildlife as well as signs of physical damage.
In herring gull colonies, particularly in highly polluted areas of Lakes Ontario and Michigan, Fox and his colleagues had found nests with twice the normal number of eggs–a sign that the birds occupying the nests were two females instead of the expected male-female pair. The phenomenon, which persisted in some areas, had been particularly prevalent in the mid to late 1970s. During this period, Fox had collected and preserved seventeen near-term embryos and newly hatched chicks from the affected colonies in hopes that he might eventually discover what was causing this unusual behavior and other reproduction problems.
A few years later, Fox encountered a scientist who might help him find the answer. Michael Fry, a wildlife toxicologist at the University of California at Davis, had investigated how the pesticide DDT and other synthetic chemicals disrupt the sexual development of birds after hearing reports of nests with female pairs in western gull colonies in southern California. While some looked for an evolutionary explanation for the phenomenon, Fry had suspected contamination. Reports in scientific literature indicated that a number of synthetic chemicals, including the pesticide DDT, could somehow act like the female hormone estrogen.
To test his theory, Fry had injected eggs taken from western gull and California gull colonies in relatively uncontaminated areas with four substances–two forms of DDT; DDE, the breakdown product of DDT; and methoxychlor, another synthetic pesticide that had also been reported to act like the hormone estrogen. The experiment showed that the levels of DDT reported in contaminated areas would disrupt the sexual development of male birds. Fry noted a feminization of the males’ reproductive tracts, evident by the presence of typically female cell types in the testicles or, in cases of higher doses, by the presence of an oviduct, the egg-laying canal normally found in females. Despite all this internal disruption, the chicks had no visible defects and looked completely normal.
As soon as he could make arrangements, Fox shipped the preserved embryos and chicks off to Fry in California. In his examination of the birds’ reproductive tracts, Fry found that five of the seven males were significantly feminized and two had visibly abnormal sex organs. Five of the nine females showed significant signs of disrupted development as well, including the presence of two egg-laying canals instead of the one that is normal in gulls. Such disruption, Fry noted, could indicate that the birds had been exposed to chemicals that acted like the female hormone estrogen.
Earlier experiments by other researchers had shown that exposing male birds to estrogen during development affects the brain as well as the reproductive tract and permanently suppresses sexual behavior. When chicken and Japanese quail eggs received estrogen injections, the males that hatched never crowed, strutted, or exhibited mating behavior as adults.
Taken together, the evidence in the Great Lakes suggested that the females were nesting together because of a shortage of males, which might be absent because they were disinterested in mating or incapable of reproducing. Though most eggs in these same sex nests were infertile, these females sometimes managed to mate with an already paired male and hatch a chick. The female pairs appeared to be an effort to make the best of a bad situation.
Fox and others had noticed other behavioral abnormalities as well, particularly in birds that had high levels of chemical contamination. In Lake Ontario colonies, the birds showed aberrant parental behavior, including less inclination to defend their nests or sit on their eggs. In unsuccessful nests, the incubating eggs were unattended for three times as long as in the nests where birds successfully produced offspring. A study comparing reproduction in Forster’s terns nesting in clean and contaminated areas reported that nest abandonment and egg disappearance, often due to theft by predators, was substantial in the contaminated area on Lake Michigan but virtually nonexistent in the clean colony on a smaller lake in Wisconsin. Parental inattentiveness clearly diminished the chances that the eggs would hatch and the chicks would survive.
What Colborn remembered afterward about the conversation was how cautious they had all been. Despite the shared view that wildlife findings had implications for humans, no one wanted to acknowledge the unspoken question hanging in the air. No one dared ask whether synthetic chemicals might be having similar disrupting effects on human behavior. Those were treacherous waters they all preferred to avoid.
pages 20 – 22
For additional information – http://www.ourstolenfuture.org/