Xenoestrogens/Endocrine Disruptors

What is an endocrine disruptor?

Rachel Carson first highlighted the subtle impacts of chemicals in our environment upon animals with her work on DDT
in the 1950's and 60's. In recent years studies have begun to bring together the studies showing clearly the impacts of
man-made chemicals like PCBs, dioxin and many pesticides act like hormones and interfere with or disrupt normal
body functions exacerbating the development of breast cancer, reducing sperm counts, interfering with normal
development among other health impacts. One book that describes these impacts is Our Stolen Future: Are We
Threatening Our Fertility, Intelligence and Survival? by Theo Colborn, Diane Dumanoski and John Peterson Myers.

Environmental chemicals pose the greatest hazard in the earliest phases of life because hormones orchestrate
development and fetal development is exquisitely sensitive to tiny variations in hormone signals.

Endocrine disruptors (sometimes also referred to as hormonally active agents) are exogenous substances that act like
hormones in the endocrine system and disrupt the physiologic function of endogenous hormones.

Studies have linked endocrine disruptors to adverse biological effects in animals, giving rise to concerns that low-level
exposure might cause similar effects in human beings.

Endocrine disrupting compounds encompass a variety of chemical classes, including hormones, plant constituents,
pesticides, compounds used in the plastics industry and in consumer products, and other industrial by-products and
pollutants. Some are pervasive and widely dispersed in the environment. Some are persistent organic pollutants
(POP's), and can be transported long distances across national boundaries and have been found in virtually all regions
of the world. Others are rapidly degraded in the environment or human body or may be present for only short periods
of time.

All people are exposed to chemicals with estrogenic effects in their everyday life, because endocrine disrupting
chemicals are found in low doses in literally thousands of products. Chemicals commonly detected in people include
Bisphenol A, Polybrominated diphenyl ethers (PBDE's), and a variety of Phthalates.


The endocrine system utilizes circulating hormones to help integrate the functions of individual organs and the nervous
and immune systems. Complex interactions among these systems are responsible for control, regulation, and
maintenance of homeostasis, reproduction, development, and behavior.

DDT was recognized to have estrogenic effects in chickens in 1950. Though it is now banned from use domestically, one
ton of DDT per day passed through US ports in 1996. Large quantities are produced and used elsewhere in the world.

The effects of endocrine disruptors also provides powerful evidence for why we must stop exposure to chemicals such
as dioxins, PCBs, DDT and other chlorinated pesticides and industrial chemicals. PCBs and DDT have already been
banned from sale in this country, but PCBs can still be found in virtually every neighborhood transformer and
capacitor. And, DDT continues to be manufactured for export to other countries. We need to get involved to get
government and industry to remove PCBs from use in this country and to stop the manufacturing of DDT for export
and use in other countries.

Our historic concentration on dioxin, PCBs, and DDT has produced a large volume of literature relating to their
toxicity. Even with these chemicals, there are large gaps in our understanding of mechanisms of action. Most other
compounds, some of which are in widespread commercial use, found virtually throughout the world, to which large
populations of humans and wildlife are exposed, have been studied much less or not at all.

Between the 1940s and 1970s, doctors prescribed an artificial estrogen named diethylstilbestrol, or DES, to prevent
miscarriages in millions of pregnant women. The diethylstilbestrol (DES) story is, of course, another tragic example of
failure to understand the consequences of human exposure to a hormonally-active substance. DES was given to millions
of pregnant women for over twenty years before its adverse effects in DES daughters and sons were recognized and its
failure to do what it was intended to do was acknowledged. In the early 1950's, soon after human use of DES was
initiated, investigators performed a double-blind, placebo-controlled study on the therapeutic value of DES during
pregnancy. The study clearly indicated that DES did not prevent spontaneous abortions. In fact, DES use was
associated with increases in abortions, neonatal deaths, and premature births - and we now know of the wide range of
other effects that became apparent after birth. If the unusual malignancies had not occurred and finally been recognized
in young women, how long would it have been before other adverse effects were recognized and attributed to DES
exposure?

More....


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