The chemicals we come into contact with every day could affect a woman's ability to breastfeed, concludes a review of research published in the journal Environmental Health Perspectives. The review was compiled by a panel of over 60 toxicologists, epidemiologists, and public health advocates who met back in November 2009 to analyze the existing research on environmental chemicals and breast development and breast cancer. "We know that factors early in life, during puberty, and during pregnancy have a big impact on breast cancer rates," says Ruthann Rudel, lead author of the review and director of research at the nonprofit Silent Spring Institute, which studies how environmental influences can affect breast cancer. "And we know there is a diverse array of chemicals that are doing this."
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The purpose of the panel's meeting was to review the existing evidence on endocrine disruptors and determine gaps in what's known and isn't known about how they affect the mammary gland, and how they might play a role in breast cancer and a woman's ability to breastfeed. Much of the research uncovered at the workshop centered on what is known about endocrine-disrupting chemicals. The authors identified eight chemicals for which enough research exists to demonstrate that they alter mammary gland development in such a way that can increase both a woman's risk of developing breast cancer and having difficulty breastfeeding, and even lead to enlarged breasts in young boys and men. To put that number in perspective, another nonprofit health advocacy group, The Endocrine Disruption Exchange, recently published a list of 1,373 known endocrine disruptors. In essence, out of more than 1,000 chemicals, only eight have been researched well enough to fully understand their potential health effects. They are:
• bisphenol A, an endocrine-disrupting component of plastic and canned food linings
• the pesticide atrazine, which has been banned in most countries but has been detected in drinking-water supplies in the U.S.
• flame retardants called polybrominated diphenyl ethers used in electronics, furniture, and automobiles
• dibutylphthalate, a chemical used in nail polish, paints, and modeling clays to keep them flexible
• dioxin, an industrial contaminant associated with PVC plastic production that builds up in the fatty tissue of animals whose meat and dairy products we consume
• methoxychlor, a now-banned pesticide that is still detected in some U.S. homes
• nonylphenol, a chemical added to pesticides that's also used in petroleum-based laundry detergents
• perfluorooctanoic acid (PFOA), which is used in the production of nonstick and stain-resistant finishes.
Exposures to these chemicals, as well as to natural estrogens, such as the soy phytoestrogen genistein, are most problematic at three stages of life: while a fetus is still in the womb, during puberty, and (for women) during pregnancy. It's during those phases that an individual's mammary glands are developing and are therefore most sensitive to endocrine disruptors. And, the researchers concluded, some of these chemicals are more damaging to breast tissue than they are to other tissues in the body, and at much lower doses.