Toxic Chemicals and Public Health
John Peterson Myers and Michael Lerner
International Herald Tribune
October 16, 1999


At a UN conference last month, widespread consensus emerged on eliminating from commerce 12 of the most toxic chemicals on earth, which belong to a class known as persistent organic pollutants. The consensus around these chemicals, however, foretells controversy in the future, and carries us pell- mell toward international disagreement, and potential trade wars, over other manmade substances.

A confrontation between free trade and environmental health, triggered by technological innovations, is already visible in trans- Atlantic disputes. Europeans have made clear that they do not want genetically engineered foods and hormone-treated beef forced on them. U.S. companies and trade negotiators, meanwhile, protest that the scientific research on such products remains ambiguous.

Coming to grips with persistent organic pollutants will raise the stakes for everyone. These substances, known to harm wildlife and humans, remain chemically active for several decades after they have been applied. The decision to reduce or eliminate 12 of them is relatively uncontroversial, so long as important public health exceptions allow DDT to be used for malaria control until better alternatives are deployed.

The real crunch will come in deciding what criteria to apply to chemicals that might be banned in the future. Endocrine-disrupting chemicals, a group that includes a number of widely used pesticides, basic plastics and plastics additives, are likely to come under international scrutiny next. Emerging science shows that these compounds interfere with hormonal action, especially in the developing fetus. They can wreak havoc with reproductive organs, neurological development and disease resistance.

The U.S. National Academy of Sciences recently released a groundbreaking report confirming that concerns about these chemicals were plausible and significant. It noted four reasons to be suspicious of endocrine-disrupting chemicals. First, laboratory experiments show that they can interfere with hormones at extraordinarily low concentrations. Second, low and intermediate concentrations may have especially serious consequences for fetuses during certain developmental ''windows.'' Third, the effect of endocring-disrupting chemicals in mixtures cannot be predicted by studies of one compound alone, although humans experience these chemicals in so many different combinations that a thorough toxicological assessment of all likely mixtures is literally impossible. Finally, the effects of exposure on a fetus may not be apparent until adulthood, long after knowledge of exposure has disappeared.

The academy accurately noted that studies of many potential effects of these chemicals on humans - such as breast cancer, endometriosis sperm count declines, lowered immune resistance and learning disabilities - still need to be done and may take decades to complete. It concluded that the absence of scientific certainty is not a result of the chemicals' safety, but of ignorance.

Among the products that could be affected are major money-makers for the chemical and pesticide industries. Most notable is bisphenol A, a building block of polycarbonate plastic but also a mimic of the hormone estrogen. Polycarbonate leaches bisphenol A into food from can linings, and into children's saliva when it has been used as a dental coating to prevent tooth decay. Although the research on the chemical's health risks is ambiguous, it may be sufficiently alarming to cause Europe to act.

The eventual verdict on many endocrine-disrupting chemicals is virtually guaranteed: plausibly but not certainly guilty. Yet this is exactly the kind of circumstance in which Europe has proven willing to take preventative measures, while the United States, pushed hard by companies producing these toxic chemicals, has not. The battle forming over persistent organic pollutants is fundamentally one of ideas. On the one hand, there is an emerging global consensus that precautionary action is essential to a healthy, sustainable planet. On the other, industrial interests are demanding a ''smoking gun,'' of the type previously required by tobacco manufacturers, before they are willing to change.

The good news is that UN members will likely sign a treaty next year on eliminating persistent organic pollutants. The unanswered question is whether this will be a move toward wider acceptance of a higher public health doctrine. Will we invoke the precautionary principle as a guide for evaluating potential risks from new technology, or will commercial interests force society to wait for an impossible level of proof before acting to protect public health and safety?

Dr. Myers is director of the W. Alton Jones Foundation, a private philanthropy supporting efforts to protect the global environment and prevent nuclear war.

Dr. Lerner is president of Commonweal, a health and environmental research institute in the San Francisco Bay Area.