Endocrine Disrupting Chemicals

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Our understanding of how endocrine disrupting chemicals (EDCs) interfere with hormones and other chemical signalers is growing rapidly. Once thought to primarily interfere with hormone receptors, we now know the culprits impact a wide range of signaling processes. They can interfere with hormone binding, transport, and production; gene expression; and a host of other cell regulatory mechanisms. These disruptions may affect the endocrine, immune and neural systems and may lead to developmental, reproductive, metabolic, brain, and behavior problems.

There is no doubt that the physical world, and a good portion of its human and animal life, is exposed to and contaminated with EDCs. Some are natural plant compounds called phytochemicals. Others are synthetic versions mostly released during human activities.

The long list of known and potential EDCs are found in:

• water, soil, and air
• plants
• processed foods
• pharmaceuticals
• personal care products
  household products
• plastics
• pesticides
• industrial chemicals
• humans and wildlife

Still, no simple conclusions about effects can be drawn. Even though exposure is widespread, we still don’t know the full extent of health risks and problems associated with EDCs.

Clearly, wildlife studies, laboratory experiments, and human experiences do provide evidence of health effects and intergenerational impacts from exposure to high concentrations of these ubiquitous substances. Male feminization, lower fertility, and other reproductive and developmental problems occur in a host of invertebrate species and wild fish, amphibians, reptiles, birds, and mammals.

Human impacts could be likely for certain individuals or populations in specific regions of the world. Attention has focused on health problems arising when EDCs interfere with estrogens, androgens, and other sex hormones and the thyroid hormones. These powerful messengers are key for proper functioning of the reproductive, immune, and central nervous systems. Health effects associated with EDCs include reproductive problems, such as reduced fertility, male and female reproductive tract abnormalities, and skewed male/female sex ratios; early puberty; brain and behavior problems; impaired immune functions; and various cancers.

Probably the most convincing evidence for human impacts comes from diethylstilbestrol (DES). DES, a strong synthetic estrogen banned since the 1970s, was given to pregnant women to prevent miscarriages. Years later, the grown daughters and sons of women who took the drug were having more reproductive problems and higher cancer rates than those not exposed to DES in the womb. Mice studies confirmed that DES caused the reproductive problems and certain cancers (including the rare rete-testicular cancer in males). More recent animal studies find granddaughters and sons may also be affected (CDC 2005).

Less clear, though, are impacts from daily, low level exposures to chemical mixtures.

Whether long-term exposure to low levels of EDCs causes health problems in adult wildlife and humans is still a question. Developing fetuses and embryos, whose growth and development is highly controlled by endocrine signals, may be the most vulnerable to and have the most lasting effects.

Many consensus statements issued and endorsed by scientists and scientific organizations echo this. The Wingspread statements, the Weybridge Report, and the Prague Declaration on Endocrine Disruption are examples.

The World Health Organization’s 2002 global report on endocrine disrupters also concluded that there is sufficient evidence of health effects from high-level exposure to EDCs in wildlife and weaker evidence for humans. Uncertainty from constant, low-level exposure “make understanding the potential effects posed by exposure to these chemicals an obvious international priority.”(IPCS 2002)
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