An endocrine disrupting chemical can affect the endocrine system of an organism
in a number of ways, but they typically affect animals in three specific ways. They
can mimic, block, or trigger a hormone response [8].
Mimic Chemicals Mimic chemicals respond like normal hormones inside the
body. A good example of a mimicking endocrine disruptor is the potent drug
diethylstilbestrol (DES), a synthetic estrogen. Doctors prescribed DES to as many
as five million pregnant women to block spontaneous abortion prior to DES being
banned in the early 1970s. When doctors first began prescribing DES, they believed
that it would prevent miscarriage and promote fetal growth. However, researchers
discovered that after the children went through puberty, DES affected the development of the reproductive system of the daughters of the mothers given DES, and
it caused vaginal cancer. In addition, these women have an increased risk of
developing endometriosis. Sons born to mothers given DES have an increased
frequency of undescended testes (cryptorchidism), congenital birth defects, hypospadias (urethra opening on the underside of the penis), and decreased adult
sperm count.
Blocker Chemicals The second group of disrupting chemicals is hormone blockers.
These interfere with how naturally occurring hormones function. Blockers bind to
the same protein receptors as the real hormone but do not stimulate any action. They
sit in the way of the natural hormone and prevent it from sending its message. An
example of a blocker is how DDE (a metabolic breakdown product of the pesticide
DDT) blocked action of testosterone in male alligators in Lake Apopka, Florida,
which led to undersized penises. Testosterone, a male hormone, is needed for proper
reproductive development.
Trigger Chemicals Triggers are the third category of disruptors. They attach to
protein receptors and then trigger an abnormal response in the cell. These triggers
cause growth at the wrong time, an alteration of metabolism or synthesis of a
different product. The best-known triggers are dioxin and dioxin-like chemicals.
Dioxin acts through a hormone-like process to initiate entirely new responses.
3 Descriptions of Specific EDCs
In this section, the potential EDCs are grouped by chemical class (see Table 4.1).
Descriptions of the EDCs provide a brief description of the chemical, its major uses,
the major human exposure routes, health effects, water solubility, environmental
persistence, occurrence/detection in water sources, drinking water standards, and
statutes that regulate the substance in water. The best available technology (BAT) as
determined by laboratory testing for removal of specific EDCs from water is
indicated when this has been determined.
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175
in a number of ways, but they typically affect animals in three specific ways. They
can mimic, block, or trigger a hormone response [8].
Mimic Chemicals Mimic chemicals respond like normal hormones inside the
body. A good example of a mimicking endocrine disruptor is the potent drug
diethylstilbestrol (DES), a synthetic estrogen. Doctors prescribed DES to as many
as five million pregnant women to block spontaneous abortion prior to DES being
banned in the early 1970s. When doctors first began prescribing DES, they believed
that it would prevent miscarriage and promote fetal growth. However, researchers
discovered that after the children went through puberty, DES affected the development of the reproductive system of the daughters of the mothers given DES, and
it caused vaginal cancer. In addition, these women have an increased risk of
developing endometriosis. Sons born to mothers given DES have an increased
frequency of undescended testes (cryptorchidism), congenital birth defects, hypospadias (urethra opening on the underside of the penis), and decreased adult
sperm count.
Blocker Chemicals The second group of disrupting chemicals is hormone blockers.
These interfere with how naturally occurring hormones function. Blockers bind to
the same protein receptors as the real hormone but do not stimulate any action. They
sit in the way of the natural hormone and prevent it from sending its message. An
example of a blocker is how DDE (a metabolic breakdown product of the pesticide
DDT) blocked action of testosterone in male alligators in Lake Apopka, Florida,
which led to undersized penises. Testosterone, a male hormone, is needed for proper
reproductive development.
Trigger Chemicals Triggers are the third category of disruptors. They attach to
protein receptors and then trigger an abnormal response in the cell. These triggers
cause growth at the wrong time, an alteration of metabolism or synthesis of a
different product. The best-known triggers are dioxin and dioxin-like chemicals.
Dioxin acts through a hormone-like process to initiate entirely new responses.
3 Descriptions of Specific EDCs
In this section, the potential EDCs are grouped by chemical class (see Table 4.1).
Descriptions of the EDCs provide a brief description of the chemical, its major uses,
the major human exposure routes, health effects, water solubility, environmental
persistence, occurrence/detection in water sources, drinking water standards, and
statutes that regulate the substance in water. The best available technology (BAT) as
determined by laboratory testing for removal of specific EDCs from water is
indicated when this has been determined.
4 Endocrine Disruptors
175