What is an endocrine disruptor?
An endocrine disruptor is a synthetic chemical that when absorbed into the
body either mimics or blocks hormones and disrupts the body's
normal functions. This disruption can happen through altering
normal hormone levels, halting or stimulating the production
of hormones, or changing the way hormones travel through the
body, thus affecting the functions that these hormones control.
Chemicals that are known human endocrine disruptors include
diethylstilbesterol (the drug DES), dioxin, PCBs, DDT, and
some other pesticides. Many chemicals, particularly pesticides
and plasticizers, are suspected endocrine disruptors based
on limited animal studies.
How do we know that endocrine disruptors are dangerous?
Many plant and animal species are showing signs of ill health
due to exposure to endocrine disrupting chemicals. For example,
fish in the Great Lakes, which are contaminated with polychlorinated
biphenyls (PCBs) and other man-made chemicals, have numerous
reproductive problems as well as abnormal swelling of the
thyroid glands. Fish-eating birds in the Great Lakes area,
such as eagles, terns, and gulls, have shown similar dysfunctions.
Scientists have also pointed to endocrine disruptors as
the cause of a declining alligator population in Lake Apopka,
Florida. The alligators in this area have diminished reproductive
organs that prevent successful reproduction. These problems
were connected to a large pesticide spill several years earlier,
and the alligators were found to have endocrine disrupting
chemicals in their bodies and eggs.
Should humans be concerned for their health based on
evidence that fish, birds and alligators have been affected?
Yes. All vertebrates (fish, amphibians, reptiles, birds,
and mammals, including humans) are fundamentally similar during
early embryonic development. Scientists can therefore use
the evidence acquired on other species to make predictions
about endocrine disrupting effects on humans.
In the 1950s and 1960s pregnant women were prescribed diethylstilbestrol
(DES), a synthetic estrogen, to prevent miscarriages. Not
only did DES fail to prevent miscarriages, but it also caused
health problems for many of these women's children. In 1971,
doctors began reporting high rates of unusual vaginal cancers
in teenage girls. Investigations of the girls' environmental
exposures traced the problem to their mothers' use of DES.
The girls also suffered birth defects of the uterus and ovaries,
and immune system suppression.
Source: nrdc.org |
