To one knows exactly why so few baby boys were born in the late 1970s and early 1980s to certain families in Seveso, Italy. But the answer may lie in a 1976 industrial explosion that spewed out the pollutant dioxin. Two weeks after the accident, the 735 people living in the most contaminated area, dubbed Zone A, were evacuated. In the following eight years, women from that group gave birth to far more girls than boys. At the time, researchers did not notice the phenomenon; they were more concerned with whether the dioxin might eventually cause cancer. Then excess cancers did start turning up among Seveso's adults, and last year epidemiologists noticed in the data the strange scarcity of male children among Zone A's previous residents.
Baby boys usually slightly outnumber girls; worldwide, there are about 106 boys to every 100 girls. But during the first eight years after the Seveso accident, mothers who had lived in Zone A gave birth to 48 girls and only 26 boys. Parents with the highest levels of dioxin had daughters but no sons at all. Perhaps, theorized University of Milan clinical pathologist Paolo Mocarelli last fall in the British medical journal The Lancet, dioxin inter- feres with hormonal balances in developing embryos, either making normal male growth impossible or killing males.
Mocarelli didn't stumble upon the Seveso phenomenon by accident. He knew to look for it, in part, because scientists had already discovered in wildlife that toxics such as dioxin can affect sex ratios. "In wildlife, that is well known," he says.
Consider the famous case of crossed bills in double-crested cormorants in the Great Lakes region during the 1980s. Hatchlings with the deformity were almost always female, and scientists speculate the same chemicals that likely cause the crossed bills also were killing males before they hatched. Proof remains illusive, as unhatched embryos usually rot away in the shell before resear- chers can determine gender. But, says zoologist James Ludwig, a private ecotoxicology consultant in Canada and Wisconsin who examined the eggs, "If you assume there's an equal probability that males and females will get the crossed-bill syndrome from exposure to toxic chemicals, then the males must be dying. Or the females are more sensitive."
POISONED WILDLIFE: Sickened and dying wild animals have long been harbingers of the effects of toxics in the environment. In the United States, we have paid enough attention to such messages to pass laws such as the 1972 ban on the pesticide DDT, as well as increase regulation of tox--ics such as dioxin and dioxinlike chemicals. As a result, many affected wildlife species are bet- ter off than they were 25 years ago, and presumably so are humans.
That's the good news. So are the facts that U.S. children today are generally healthier and better nourished than at any time in history. But even with DDT, we are only now finding out just how dangerous that chemical is to human health--especially to children. While a great deal of uncertainty remains, a growing body of peer-reviewed scientific literature strongly suggests that the young of most, if not all, animals are far more susceptible to toxics than adults.
Not only can the young get heftier proportional doses of pollutants because of their small sizes and fast metabolisms, the exposures can impede development of rapidly growing bodies. "Children eat, drink, and breathe more for their body weights than adults do, so they get bigger proportional doses of whatever is out there," explains University of Pittsburgh psychiatrist Herbert Need- leman, who pioneered studies linking lowered …