Ask TreeHugger: What Is an Endocrine Disruptor?

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Question: I realize that we are exposed to all types of chemicals everyday, many that we are unaware of and some which are unavoidable currently. My particular concern is of endocrine disruptor's and their effects on developing kids. I know for conventional produce there is a dirty dozen list to avoid, is there something similar for products or sources of endocrine disruptor's ...

What are the five largest exposure sources for endocrine disruptor's in our daily lives?

Any help or information would be great, thanks for being a great resource.

Response: The endocrine system specifically includes organs, such as the pituitary, thyroid, pancreas, adrenals, ovaries and the testes, that release hormones into the bloodstream. These hormones, of which there are many different types, act as chemical messengers in humans and in animals, telling the body how to behave – for example, growth hormone tells the body to build muscle mass. Endocrine disruptors are any chemical – man-made or natural -- that disrupts the normal balance of these hormones, with particular focus on estrogen, which is secreted by the ovaries that regulates menstruation, fertility, and fetal development, androgens, including testosterone secreted by the testes, and thyroid hormones. Disruption can occur when a chemical mimics or blocks one of these hormone’s actions or causes the hormone to be over or underproduced. By doing so, this disruption can cause the body to act or a fetus to develop in ways that are not normal or desired. For example, scientific studies have shown that certain chemicals can disrupt endocrine function and through this disruption, can result in physical abnormalities, infertility, or cancer (breast, prostate and testicular).

These effects have been shown mostly in animals. Scientific studies have specifically identified only a few chemicals as known endocrine disruptors in humans, including the drug diethylstilbesterol (or DES), and the chemicals DDT, PCBs, and dioxin. Although these chemicals are no longer in use today, PCBs and dioxin especially can still be found in the air, water, food and dirt, causing concerns over their endocrine disrupting effects to remain as well.

Laboratory studies of animals have also identified a growing list of commonly used chemicals as suspected endocrine disruptors. This list includes many pesticides (such as 2,4-D, aldicarb, benomyl), as well as several chemicals used in plastics (such as alkyl phenols, bisphenol A, and phthalates) and certain heavy metals (such as cadmium, mercury, and lead). Whether these and other chemicals also have endocrine disrupting effects in humans is not known, but is the subject of much research. The US Environmental Protection Agency has developed a two-tiered screening and testing process to test chemicals for their possible endocrine disrupting effects in humans and is beginning to test chemicals – initially 73 pesticide-related chemicals – for their possible endocrine disrupting effects. The results of this testing are not yet known, but if successful will likely result in testing of additional chemicals.

More detailed information about endocrine disruptors and the EPA screening system can be found here. Or, if you prefer, information on the European perspective on endocrine disruptors can be found here.

Previous Ask Treehugger columns can be found here.

Helen Suh MacIntosh is a professor in environmental health at Harvard University and studies how pollution behaves in the environment and how it affects people's health. Please keep in mind that her answers are just her interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Use this column at your own risk. Having said this, please feel free to post any of your environmental health questions to (Please use a descriptive email subject line and mention if you want to remain anonymous or not).