sperm counts loom ominously over this discussion, for these reports
harbor implications that extend beyond the question of male fertility.
Animal experiments indicate that contamination levels sufficient
to impair sperm production may affect brain development and behavior
as well. Thus, it is likely that sperm counts are just one concrete,
measurable signal of much broader effects on aspects of human health
and well-being that are not so easily quantified. What is at stake
is not simply a matter of some individual destinies or impacts on
the most sensitive among us but a widespread erosion of human potential
over the past half century. The evidence taken as a whole makes
it difficult to avoid questions about the significance of this chemical
assault for society at large.
data, laboratory experiments, the DES experience, and a handful
of human studies support the possibility of physical, mental, and
behavioral disruption in humans that could affect fertility, learning
ability, aggression, and conceivably even parenting and mating behavior.
To what extent have scrambled messages contributed to what we see
happening around us-the reproductive problems seen among family
and friends, the rash of learning problems showing up in our schools,
the disintegration of the family and the neglect and abuse of children,
and the increasing violence in our society? If hormone-disrupting
chemicals undermine the immune system, could they be increasing
our vulnerability to disease and thus, contributing to rising health
care costs? Most fundamentally, what does this mean for the human
these effects are occurring broadly, hormone disruption may well
be contributing to aberrant and unhealthy tendencies in our society.
On the other hand it is doubtful these chemicals are causing all
the social dysfunction we see around us. Those seeking a single,
simple explanation for such complicated phenomena are bound to be
frustrated and disappointed.
in the case of relatively straightforward physical problems, such
as sperm count declines, we understand far too little about the
hormone-disrupting chemicals unleashed in the environment to assess
the prospects with confidence. The four studies reported to date
show a precipitous drop in human male sperm counts in recent decades-a
loss on average of one million sperm per milliliter of semen a year.
Such a sharp downward trend is truly alarming. Even more alarming
is the fact that this decline continued for almost a half century
before medical researchers recognized what was happening. Will this
stunning rate of loss continue? Where will it end?
currently regulated persistent chemicals are largely responsible
for the decline, sperm counts could begin rebounding around 2030.
As noted in Chapter 10, the studies find a correlation between the
quantity and quality of sperm and the date of a man's birth with
the youngest men showing the lowest sperm counts and the greatest
number of malformed sperm- a pattern that strongly supports the
theory that the decline is the result of damage before birth or
early in life. There is inevitably a long delay, however, before
damage becomes evident through a sperm count analysis. The youngest
men in the recently reported sperm count studies were born in the
early 1970s, just at the time that the United States and other industrialized
countries began to restrict the use of highly persistent organochlorine
chemicals such as DDT, dieldrin, lindane, and PCBs. So their low
sperm counts could reflect the high exposure of their mothers to
persistent chemicals in the 1960s and 1970s before governments imposed
restrictions. Since then, the concentrations in human tissue of
DDT, the DDT breakdown product DDE, and lindane, for example, have
dropped considerably in countries where their use is restricted.
So if prenatal exposure to endocrine-disrupting pesticides have
played a major role in sperm count reductions, one would expect
to see an upswing in sperm numbers over the next decade, at least
in developed countries, as males born in the 1980s reach maturity.
In countries such as India, however, just two persistent pesticides,
DDT and lindane, make up 60 percent of the pesticides and their
use is still increasing, according to pesticide experts. It is important
to note, also, that human body burdens of PCBs, which were banned
in industrial countries at about the same time as DDT, have not
shown a significant decline even where the compounds were banned.
Animal and human studies have both linked this family of chemicals
to impaired male fertility.
sperm counts could be an unfortunate historical episode-an unforeseen
consequence of the midcentury experiment with persistent chemicals,
which many countries have now wisely discontinued. The threat could
now be essentially behind us, even though it may take decades to
play out the effects. Unfortunately, the worrisome new discoveries
described in previous chapters indicate the hazard from synthetic
chemicals has probably not abated. As human exposure to DDT and
other persistent compounds has diminished in countries like the
United States, exposure to other hormone-disrupting chemicals has
rapidly increased. Consider the extent to which plastic has replaced
glass and paper in packaging over the past two decades. A series
of accidental discoveries have demonstrated that plastics are not
inert as was commonly assumed and that some of the chemicals leaching
from plastics are hormonally active. Plastics have found their way
into every corner of our lives, creating the potential for significant
chronic exposure to hormone disruptors. They carry everything from
soda to cooking oil; they line metal cans and are the preferred
material for children's toys. It is unlikely that all plastics are
hazardous, but because of manufacturers' claims of trade secrets,
there is no way to know the chemical composition of any given plastic
container or to judge how much of the plastic in use might be shedding
hormone-disrupting chemicals. Scientists also warn that hormone-disrupting
chemicals may lurk in ointments, cosmetics, shampoos, and other