trends in scientific findings about endocrine disruption
disruption burst onto the public and policy scene in the mid-1990s,
propelled by a growing body of science and then galvanized by the
publication of Our Stolen Future. For a good history of this
dynamic, read Sheldon Krimsky's 1999 book, Hormonal
Since publication of Our Stolen Future, the emerging science
has emphasized 6 broad trends:
is ubiquitous. All humans have been exposed, to varying
amounts. Some have more exposure. Some have less. But no one has
no exposure. No baby has been born for at least three decades
without some exposure in the womb. Every person has several hundred
novel chemicals in their body, chemicals not part of human body
chemistry before the 20th century.
experiments show that exposures have impacts at levels
far lower than had been considered possible in traditional
toxicology. The exquisite sensitivity of natural hormonal
control to interference by endocrine disruptors will force many
changes in regulations, as the current system is inadequate.
more hormone systems, perhaps all chemically-mediated message
systems, are now known to be vulnerable to endocrine disruptors.
The study of endocrine disruption began with a focus on compounds
capable of mimicking or interfering with estrogen. Now science
has revealed disruptors for almost every hormone system that has
been studied. This includes other sex steroid hormones, like testosterone
and progesterone, as well as thyroid and retinoids.
more compounds are now known to be powerful endocrine disruptors.
This includes contemporary use pesticides and a range of chemicals
in widespread use in consumer products. The biggest surprise (except,
perhaps, to the polymer chemists who invented them) is that certain
plastics show endocrine-disrupting effects.
health effects of concern now include adult impacts of fetal exposure.
This means, for example, that studies attempting to prove an association
between adult levels of exposure and adult risk
to disease or dysfunction do not test the most important potential
links between endocrine disruptors and human health. We need studies
of developmental exposure (especially fetal) in relation to risk,
examined for all relevant life stages. For example, one of the
greatest gaps in breast cancer research is that while many studies
examine adult exposure and adult risk, none examine fetal or pubertal
exposure and adult risk.
epidemiology is biased toward false negatives in the search for
health effects of endocrine disruption. It will be exceedingly
difficult, if not impossible, to establish scientific certainty
of causation of many health problems in human, even though based
on laboratory data it is likely that endocrine disruption is involved
in a range of human diseases. Because the animal data demonstrate
plausible, serious risks to human healths, this bias toward false
negatives (a statistical term that means finding no association
when in fact there is one) requires the application of the precautionary
principle, using animal data as the guide.