In 2005, Shanna Swan and her colleagues discovered that the phthalates in plastic baby products and toys led to a variety of penile disorders, including reduced size.
Credit: iStockphoto
We are all unwittingly participating in a massive experiment without our consent. We are exposed to hundreds (and perhaps thousands) of man-made chemicals whose impacts on our health have barely been considered. But increasingly we are learning that many can threaten human health.
Of particular concern are those chemicals that modify how our hormones function and the multiplicity of complex signals that our bodies need to function properly. These chemicals are known as endocrine disruptors, and only now are we becoming aware of their profound influence on how we feel, how we function, how healthy we are, and how little we know about them.
Rachel Carson stirred the first notable misgivings about our contaminated environment in her 1962 summons to action, Silent Spring. She provoked us to listen to her sentinels: "…On the mornings that had once throbbed with the dawn chorus of scores of bird voices there was now no sound; only silence lay over the fields and woods and marsh."
Carson wrote about wildlife, where we saw the earliest clues to what we had wrought by contaminating our environment. Humans are not exempt from these consequences.
Our current understanding of how these chemicals can alter human health began with the discovery of the disastrous impacts of a drug, diethylstilbestrol, or DES. The FDA approved DES for the prevention of miscarriage in 1947.
It was marketed worldwide despite a well-done clinical study showing it was therapeutically ineffective. It proved to be a biological time bomb. Daughters of women who had been prescribed DES appeared to be healthy.
But, after undergoing the hormonal changes of adolescence, a majority of those who had been exposed early in pregnancy developed a multitude of adverse effects. They showed abnormalities of the reproductive tract; they had problems conceiving and, if they succeeded in becoming pregnant, they were far less likely to carry their pregnancy to term.
Most seriously, and fortunately far less often, they developed a rare form of vaginal cancer. New evidence is now suggesting that these reproductive problems can also affect the third generation.
DES is a synthetic estrogen. Other estrogenic chemicals were already known to pervade the environment; they had been targeted as the source of the eggshell thinning that had decimated bird populations such as the bald eagle.
It was a natural step to begin searching for other kinds of effects. They were not hard to find. And they provoked intense concern about human health.
These concerns culminated in a conference, held in the Wingspread Conference Centre in Wisconsin, in 1991. Its theme became the impetus for what became a prodigious research effort: chemically induced alterations in sexual development: the wildlife/human connection.
The Wingspread consensus statement listed the suspect chemicals. It described the wildlife populations that had been afflicted by chemical exposures; it linked these effects to human health by showing how we, too, are exposed; it called for remediation to prevent disorders in human populations.
