TIME: Almanac 1993/TIME Almanac 1993.iso/time/112690/1126350.000

Text File | 1992-08-28 | 6.6 KB | 137 lines

                                                                                MEDICINE, Page 90

The Sins of the Fathers


Both parents may be vulnerable to toxins that cause birth
defects

By ANDREW PURVIS


    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.

    The list of substances suspected of harming children through
their fathers is growing steadily. One preliminary report
concluded that heavy drinking by a man in the month before
conception could cause his child to have low birth weight.
Another study conducted in rats found that a powerful
anticancer agent called cyclophosphamide -- used primarily
against advanced malignancies -- could hamper nervous-system
development in some offspring. Scientists have also begun a
major examination of the U.S. semiconductor industry, where
workers come into contact with numerous chemicals. The
researchers will be looking for birth defects in children of
male, as well as female, employees.

    Just how men might pass health problems on to their
offspring is unclear. In women it is easy to see how
substances, once they enter the bloodstream, can penetrate the
placenta and harm the fetus, but in men the mechanism must be
more complicated. Whatever problems are transmitted have to be
passed on through the sperm or seminal fluid only at the time
of intercourse. Still, researchers believe this could happen
in several ways. A toxin might directly damage the genetic
material within the sperm (but not so much as to prevent
fertilization). Or the poison could alter the packaging around
the DNA and somehow hamper the process by which it is unfolded
and combined with the egg. Finally, chemicals contained in the
semen could pass directly into the women and damage the egg or
part of the reproductive tract. Most experts concede, however,
that these mechanisms are speculative. Notes Dr. Jeanne
Stellman of Columbia University's School of Public Health: "The
big question remains, Do funny-looking sperm produce
funny-looking babies? We don't have an answer to that."

    The issue has caught the attention of women's groups. Many
have been angered by what they consider an overemphasis in
science and the media on the woman's role in triggering birth
defects. These critics are particularly concerned about the
so-called pregnancy police -- a growing band of fetal-rights
groups and policymakers who want to regulate women, punishing
those who are not properly caring for unborn babies.

    In a case before the Supreme Court, Johnson Controls, a
Milwaukee-based company, is trying to bar fertile women from
the assembly line at a car-battery plant because of alleged
risks that such work may pose to unborn children. If the court
decides in favor of the company, solid evidence that men are
also endangering their future children could lead to major
legal challenges as well as a thorough re-examination of
procedures in U.S. factories.

    No one is suggesting that scientists abandon their search
for potential problems in pregnant women. But that approach
alone is unlikely to clear up all the questions surrounding the
250,000 birth defects that occur in the U.S. each year. The
origins of 60% of these defects are still unknown. Any research
that could dispel some of the disturbing mystery behind those
numbers would be welcomed by mothers and fathers alike.