Medicine: The Sins of the Fathers

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Ever since thousands of severely deformed babies were born in the early 1960s to mothers who had taken the drug thalidomide, doctors have been alert to the risks that certain chemicals can pose to developing fetuses. Precautions, however, have been based on one central assumption: that exposure to dangerous substances is most likely to occur inside the wombs of mothers- to-be. A series of studies has raised the possibility that the fault can sometimes lie with the father. Poisons in a man's body may silently damage his sperm and thus lead to birth defects.

The new research suggests that men exposed to substances such as lead, alcohol and some anticancer medications, as well as nuclear radiation and dioxin-containing herbicides, could be conceiving children with serious physical and mental abnormalities. Although the reports do not prove that such damage is occurring, the increasing number of studies reflects a concern about the issue that some experts feel is long overdue. Says Dr. Ellen Silbergeld, a toxicologist at the University of Maryland: "There has been a sense ((among scientists studying birth defects)) that reproduction is something that women do, and that men don't contribute very much. That is simply not true."

Researchers have long known that certain poisons can produce so-called dominant lethal effects in men. In these cases, the sperm is so damaged that it fails either to fertilize the egg or to produce a viable embryo. But little was known about whether toxins could trigger more insidious defects in the sperm -- problems subtle enough to allow the birth of the child but still harmful enough to produce serious malformations. Perhaps the most disturbing recent report concerns lead, which had been shown to impair fetal growth when mothers were exposed while pregnant. At a meeting last month of the American Public Health Association, Silbergeld reported on a study in which male rats subjected to even low levels of the toxic metal -- comparable to amounts found in the dust and dirt of many inner-city neighborhoods -- often sired offspring with "substantial" changes in brain development.

The dangers of nuclear radiation have been exhaustively studied, especially among survivors of Hiroshima and Nagasaki. Yet researchers had never confirmed that the children of exposed men could be affected. Earlier this year, researchers in England reported that such transmission may in fact be possible. Children of male workers at the Sellafield nuclear power plant were up to eight times as likely to be stricken by leukemia as children whose fathers did not work at the plant. The researchers theorized that cumulative low-level doses of radiation during the six months before conception may have triggered the damage.

Vietnam veterans have long contended that the herbicide Agent Orange, which contains dioxin, has contributed to birth defects in their children, although scientists have not been able to confirm the link. Still, a patchwork of reports continues to suggest at least a minor effect. The most recent study, published last month in the American Journal of Public Health, found that the children of men who served in Vietnam were 1.7 times as likely as the babies of other veterans to suffer from major malformations, such as clubfoot or serious heart problems.