Guest lecturer Nancy Langston on precaution and environmental health

We’ve asked this year’s Lynn W. Day lecturer Nancy Langston to discuss an aspect of her latest book, Toxic Bodies: Hormone Disruptors and the Legacy of DES (Yale University Press, 2010) as a prelude to her lecture on Nov. 11. Her current research on Lake Superior extends this interest in environmental health to the health of watersheds. In this project, she will examine the intersection of human culture with the profusion of global pollutants, such as mercury, that have made their way into watersheds and fish.

My recent book, Toxic Bodies, explores environmental histories of hormone disruptors—the industrial pollutants that mimic hormones and disrupt the endocrine systems that influence reproduction and development in wildlife as well as people. Toxic Bodies examines the landscape of exposure which begins in our own bodies, and connects us inward and outward, across generations, across ecosystems, and across species.

One of my core concerns in Toxic Bodies is the history of precautionary approaches to environmental health. The precautionary principle states that if an action might cause severe or irreversible harm to complex, unpredictable systems, the burden of proof should be on the industry to show safety. Rather than requiring the government or consumer to prove harm after a chemical is on the market, industry would have to demonstrate a chemical is safe before approval.

Precaution is popular with environmental health advocates, but many industry groups are concerned that application of the precautionary principle is unfeasible. Two main concerns have emerged: first, because experimental proof is lacking that any particular environmental exposure causes specific illnesses in people, too much scientific uncertainty remains to act. Second, precaution might stifle innovation and destroy profits.

The first concern is valid; we do indeed lack the experimental evidence that would prove pollutants cause cancer or other illnesses in humans. But does this mean chemicals are safe? Unfortunately not. We lack experimental evidence of human harm because those experiments are illegal. In the late 1940s, during the Doctors’ Trial in Nuremberg Germany, evidence emerged of Nazi medical experimentation that subjected prisoners to chemical poisons such as mustard gas. The resultant Nuremberg Code forbids research that might lead to unnecessary pain, suffering, death, or disability. No researcher can design an experiment that subjects a person to a suspected carcinogen to test whether that chemical induces cancer. By definition, then, we will never have firm proof of the links between pollutants and environmental illness. Scientific uncertainty will always remain. Toxic Bodies explores how other lines of evidence, historical as well as experimental, have been developed to provide a reasonable basis for environmental health protection.

Will precaution be as destructive to profit and innovation as opponents often claim? This sounds reasonable, but historical evidence suggests the opposite: precaution can actually increase both innovation and consumer confidence.

Precaution is not a new idea; it has been at the heart of pharmaceutical regulation since the 1938 Food Drug and Cosmetics Act. After a tainted drug named Elixir Sulfanilamide killed more than a hundred people in 1937, the FDA required that companies submit evidence of safety before a new drug would be allowed on the market. The burden of proof shifted from the consumer to the company.

Pharmaceuticals have thrived since the 1938 Act—not in spite of precautionary regulation, but because of it. When doctors and patients began to trust that the risks of new drugs would not be hidden, drug sales rose. Currently, pharmaceuticals are among the most profitable industries in the world, refuting the claim that precaution is a death knell to industry.

Precautionary policy in drug regulation has not been perfect, of course. All too often, regulators have responded to political pressure by retreating from precaution, putting consumers at heightened risk of cancer from chemical exposures. Diethylstilbestrol (DES), the first synthetic estrogen to be marketed to consumers, provides a tragic example. Beginning in the 1940s, millions of women were prescribed DES, first for menopause and then to prevent miscarriage. By the 1950s, 95% of feedlot cattle were treated with the chemical to promote rapid weight gain, and consumers who ate that beef exposed themselves and their children to carcinogenic residues.

Why did the FDA approve DES under the precautionary 1938 Food Drug and Cosmetics Act? Soon after DES had been synthesized, dozens of laboratory experiments on animals had shown that DES caused cancer and reproductive problems. These studies initially led FDA Commissioner Walter Campbell to reject the drug, arguing that even though substantial uncertainty remained about DES’s human effects, regulators must follow what he called the “conservative principle.” Yet by 1947, under political and economic pressures, the FDA had retreated from its position of precaution three times, allowing consumers to be exposed to a known carcinogen in food and medicine. Because high doses of DES in adult women didn’t seem to result in immediate harm, regulators weren’t certain that the animal experiments showing cancer were applicable. Few scientists realized that the timing of exposure was more important than the dosage, and fewer scientists realized that in utero exposure could lead to cancer that only appeared decades later. Tragedy resulted. Of the children who were exposed to DES prenatally, nearly 95 percent of those sampled experienced reproductive tract problems, infertility, or cancer.

Toxic Bodies asks: what can we learn from DES histories to guide us in a rational approach to environmental health? Several lessons emerge. First, timing is critical: during fetal development, low-level exposures to pollutants can set into motion processes that lead to cancer much later in life. Chemicals in doses that may have little effect on an adult can have tremendous effects on a child, but those effects may not be observable for decades. Requiring experimental proof of human harm means that pollutants will continue to harm human health. A precautionary approach will better protect health without stifling innovation.