Decades after one of the largest food contamination incidents in American history, the health effects are still not known. But according to a new study, one of the scariest ramifications of the poisoning has been for girls who were exposed in utero and through breastfeeding. They started menstruating at an average of 11.6 years old -- a full year earlier than others who were not as highly exposed.

This finding, the first in an ongoing study at Emory University that looks at the possible reproductive effects of the chemical exposure on women, provides one of the first clues about what happens when humans come into contact with hormone-disrupting compounds. More specifically, the study has bolstered -- with rare research on human subjects -- the belief of many researchers that environmental estrogens, including PBBs like this one, may be the culprit for what is believed to be an alarming trend of early sexual maturity.

Previous studies have provided evidence of the impact of environmental estrogens -- but mainly on animals. Lab rats consistently hit puberty early after being given doses of synthetic estrogens, for example. Most of the evidence of a mysterious race to puberty in American girls comes from anecdotal tales about the physical and hormonal mayhem hitting girls too young to have had any education about what is going on in their bodies.

The idea that environmental estrogens are the cause of this early and tumultous development is controversial, but many researchers are convinced that the two are definitively linked, at least as one piece of the pubertal puzzle.

"Because we did find this association with PBB exposure, it makes it more likely that other endocrine disruptors may be causing similar effects," says Michele Marcus, Ph.D., author of the Emory University study and associate professor of epidemiology there. "But that would have to be determined in other studies." Luckily, the Michigan residents' exposure was a freakish accident and most people will not be exposed to PBB. But they are very similar chemically to polychlorinated biphenyls (PCBs), which were widely used in electrical insulation in the 1970s and are still found in the environment.

Hitting puberty at an earlier age is believed to lead to many types of medical problems later in a woman's life, including increased risk of ovarian and breast cancer and early menopause. When the pubertal clock speeds up, "Everything gets shifted forward," says one researcher.

Although nothing biologically dangerous is believed to immediately occur with early puberty, the psychological effects cannot be underestimated. A girl can be teased mercilessly when she starts to develop before her classmates; or so embarrassed when she gets her period the first time that she keeps it a secret. A lack of sex education at such an early age also creates fear and confusion for girls who literally don't have a clue as to what is happening when they start to bleed.

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