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?f( 1 ? PC 0701 GST"; Gender$enders Are environmental "hormones" emasculating wildlife? First in a two-part series M other Nature. The term conjures up images of a warm, nurturing, bountiful environment. But this sobriquet is proving increasingly apt for another reason - one that should offer anything but-comfort. New studies suggest that through pol- lution and other environmental factors, Mother Nature is exerting a feminizing hormonal influence on the animal king- dom. W L Juvenile' bald eagle collected in Michigan last year. Its life-threatening bill deformity may have been caused by exposure to estrogenic chemicals. 'We've been seeing many more deformities in recent years,' reports David Best, a bald-eagle specialist with the U.S. Fish and Wildlife Service in East Lansing, Mich. 'We've also seen some suggestion of deformities in the embryos [of eggs that didn't hatch]," he notes. Hatching rates within this population also fall below those seen in less polluted areas, such as inland Alaska. Reproduction in these birds starts to fall when PCBs in their bodies exceed4 to 6 parts per million (ppm) or DDE exceeds 1 ppm. 'We're finding very much higher levels than that around the Great Lakes," Best notes - such as eggs with PCB concentrations as high as 120 ppm. Over the past 15 years, research has unmasked a number of "environmental hormones" - chemicals and pollutants that disrupt biological processes, often by mimicking the effects of naturally produced hormones such as the female hormone estrogen. On the ever-growing list of these agents are several restricted or banned pesticides - including DDT (and its even more toxic metabolite, DDE), kepone, heptachlor, dieldrin, mirex, and tokophene. Some polychlori- nated biphenyls (PCBs) exhibit these disruptive properties, as do certain com- bustion pollutants, ingredients in plastics, and breakdown products of common detergents (SN: 7/3/93, p.10). The hormonal activity of these chemicals usually bears little re- lationship to their intended function. Indeed, there is no way of predicting - based on structure or function - which compounds will exhibit a hormonal alter ego. That fact troubles a number of scien- tists because such environmental hormones may be contributing to an increased risk of reproductive-system cancers in females. Moreover, prenatal exposure to hormone-like pollutants can derail the developmental processes that establish gender or ensure reproductive success. While the health community has re- cently begun a host of studies to explore a possible link between estrogenic pollu- tants and cancers in women, few re- searchers have focused on the related reproductive risks such environmental hormones may pose for both sexes. That's unfortunate, says Theo Colborn, a zoologist with the World Wildlife Fund in Washington, D.C., because reproductive effects are likely to be "much more wide- spread." Indeed, she notes, animal data are beginning to suggest that far smaller exposures are needed to trigger repro- ductive effects than to induce cancers. By JANET RALOFF And because some of these reproductive changes may be subtle, they could evade detection for decades - even a lifetime - unless hunted for explicitly. Colborn has convened a number of symposia in the past few years for re- searchers who study reproductively im- paired wildlife populations or laboratory animals exposed to environmental hor- mones. Most of these scientists, she says, describe the links they're finding be- tween impaired reproduction and "hor- monal" pollutants as sobering - if not downright scary. Indeed, she and many other environ- mental scientists worry that if hormone- like contaminants can feminize male ani- mals, these ubiquitous pollutants may also underlie troubling reproductive- system trends being witnessed in men. Some of the earliest data on unex- pected reproductive risks posed by commercial chemicals came. in the early 1950s. DDT, a potent and persistent organochlorine pesticide, was shown to cause the eggshells of many birds to thin. In fact, long after the compound was banned in 1972, DDT-thinned eggshells continued to put many embryonic birds- including bald eagles - at risk of being crushed to death. DDT even wreaked havoc among birds resistant to eggshell thinning, such as sea gulls. Recognition of the extent of these problems, however, didn't emerge until decades after the initial reports of egg- shell thinning. Though heavily contaminated gull em- bryos managed to hatch, reproduction in gull colonies exposed to large amounts of DDT began to decline precipitously in the late 1960s. Biologists observed not only that many female gulls in these commu- nities were sharing nests with other fe- males - the so-called lesbian gulls - but also that the young within these commu- nities bore grossly feminized reproduc- tive tracts. Female gulls, which should have developed mature reproductive or- gans only on the left side, also carried 24 SCIENCE NEWS, VOL.145