Hormone disruptors: a cautionary tale

January 28, 2010

Nelson Institute professor Nancy Langston, an environmental historian, is the author of a new book that explores why our environment has become saturated with synthetic chemicals that disrupt hormones and asks what we can do to protect human and environmental health. Toxic Bodies: Hormone Disruptors and the Legacy of DES, published by Yale University Press, recounts the public health catastrophe created by the hormone-disrupting drug diethylstilbestrol (DES). Langston explains how this estrogenic drug, promoted for use in every pregnancy beginning in the 1940s, caused cancer in exposed fetuses and is still causing reproductive problems in their children and grandchildren. DES was also widely used to fatten chickens and beef cattle. Residues in meat and poultry were ingested by nearly every American from the 1950s through the 1970s. Even though workers who handled DES at processing plants developed reduced virility, disturbed menstrual cycles, and cancers, government agencies assured the public that DES was safe. For 30 years, says Langston, regulatory officials failed to demand appropriate studies, ignored or concealed existing data, and declined to restrict DES without proof that it caused harm. What have we learned from DES and from other hormone disruptors such as DDT that have damaged human health? Are adequate precautions in place today to prevent new disasters? In Toxic Bodies, Langston shows that the answers to these questions are frightening. While DES has been banned, we are awash in a sea of similar chemicals, and the impacts on human health are likely to be profound. Endocrine disruptors -- chemicals that disrupt hormones and alter sexual development -- are not rare. They are among the most common chemicals produced today, and include pesticides, pharmaceuticals, and plastics such as BPA. Endocrine disruptors are widely used to fatten beef, to package foods and beverages, and throughout our homes. They are found in our rivers and streams and in the tissues of almost every person. These chemicals are under-studied and misunderstood, Langston warns. Today's assurances of safety are based upon the same faulty assumptions that kept DES on the market. Our regulatory model assumes that all chemicals are more toxic at high doses than at low ones, and that toxicity is immediately apparent. Yet endocrine disruptors can cause terrible harm at very low doses, especially to developing fetuses and infants, and the effects of exposure may not be apparent until maturity or even until future generations show problems. So how can we learn from the past and protect ourselves and our children from endocrine disruptors? The key, Langston argues, is the precautionary principle: chemicals should be proven safe before they are approved and distributed. Before DES won FDA approval in 1941, researchers knew it caused cancer and sexual development problems in animals. The FDA initially rejected the drug, adopting the precautionary principle 60 years before that term came into common usage. Yet by 1947, the agency had abandoned its position of precaution, insisting that critics prove DES caused harm, rather than insisting drug companies prove DES was safe. Given what has been known since the 1940s about the risks of endocrine disrupting chemicals, why have federal regulatory agencies done so little to protect public and environmental health? Langston argues that a general hostility to regulation, a focus on economic interests rather than patient interests, and a misunderstanding of endocrine-disrupting chemicals have together delayed action that could save lives. Political, economic, cultural, and scientific pressures all contributed to the retreat from precaution, and these pressures continue to infect our federal agencies. Toxic Bodies calls upon all of us to consider the lessons of history, which hold enormous relevance for our own health and the health of future generations.