The production and release of vast quantities of novel synthetic chemicals over the past 75 years has proved to be a great global experiment—one that now involves all life. Even before the Chemical Revolution moved into high gear at the end of World War II, the first warning sign appeared that some man-made chemicals might spell serious trouble. In 1944, scientists found residues of a man-made pesticide, DDT, in human fat. Seven years later, another study brought disturbing news of DDT contamination in the milk of nursing mothers. In the early 1950s, naturalists saw thinning eggshells and crashing populations of bald eagles and other birds. By 1962, Rachel Carson documented the growing burden of contamination in Silent Spring, which detailed the devastating impact of persistent pesticides on wildlife and warned about hazards to human health.

Ironically, chemicals that were developed to control disease, increase food production, and improve our standard of living are, in fact, a threat to biodiversity and human health. Because the risk from these originally well-intentioned chemicals outweighs their benefits, their continued use is no longer warranted.

Today, the contamination from persistent man-made chemicals is a pervasive global problem that urgently demands a global solution. Responding to the gravity of this threat, the international community has begun important steps toward stopping this unintended experiment. In June 1998, nearly a hundred nations embarked on negotiations with the goal of concluding a binding, global treaty on persistent organic pollutants (POPs) before the end of 2000. The outcome is critical since this process will determine the scope and pace of global action against persistent chemicals.

Because of their unique properties, POPs pose a special kind of challenge that makes it impossible for any nation to remedy the problem by acting alone. POPs don't degrade readily and, even more important, they don't stay put. They can travel thousands of miles in complex journeys on air, water currents, and through the food web, making one country's contamination inevitably the world's problem. POPs are now ubiquitous.

The scientific case against the POPs targeted in the treaty negotiations has been mounting since the late 1940s. Many countries have already banned most of the chemicals in question or severely restricted their use. But their trade and use continues in some parts of the world. In many places, old stockpiles of pesticides and industrial chemicals are an increasing hazard to those who live nearby and to the world at large as they leak, leach, and evaporate into the air from dump sites and inadequate or deteriorating storage containers. Until an effective and adequately funded disposal program is put into place, POPs will continue to escape and add to the existing danger.

The 12 persistent chemicals specified in the ongoing negotiations pose a host of hazards. Acute exposure in tropical agriculture has caused large numbers of human deaths and injuries, including severe nervous system and liver damage. Numerous studies have also linked these synthetic chemicals to cancer and other significant health problems in people and wildlife. Emerging science has also recently heightened concern about typical "background" levels of these contaminants and a new kind of hazard known as "endocrine disruption." Researchers find that PCBs (polychlorinated biphenyls) and their co-contaminants can do damage at extraordinarily low doses, measured in parts per trillion, and that they are already compromising the health and intelligence of the next generation.

POPs jeopardize human and wildlife health in all parts of the world: in the tropics through the continued use of persistent pesticides; in temperate industrial regions through the release of persistent combustion and manufacturing by-products; in many regions because of leaking stockpiles; and in wild and remote places where globe-hopping contaminants come to rest. There is no clean, uncontaminated place anywhere on Earth and no creature untouched by this chemical legacy.

Each of us now carries several hundred synthetic chemicals that were not present in the bodies of our great grandparents at the turn of the century. Every child born today has been exposed to persistent chemicals in the womb. Because these chemicals also become concentrated in breast milk due to their affinity for fatty substances, a baby can experience the heaviest exposure to contaminants in its lifetime through breast feeding. This exposure threatens the integrity of the next generation. Given these immense stakes, precaution dictates swift and strong action to eliminate the use and production of persistent chemicals. POPs by their nature cannot be managed. The time is long overdue to end this fateful legacy of hand-me-down poisons.

What Are POPs?

The greatest concerns about contaminants have centered on persistent compounds—synthetic chemicals that resist the normal processes of degradation. As detailed in Table I, page 4, the 12 persistent chemicals targeted in the POPs negotiations include eight pesticides (aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, and toxaphene), two types of industrial chemicals (polychlorinated biphenyls or PCBs and hexachlorobenzene)1, and two families of unintended by-products of the manufacture, use, and/or combustion of chlorine and chlorine-containing materials (dioxins and furans). Persistent organic pollutants are carbon-based chemical compounds and mixtures that share four characteristics: high toxicity, persistence, a special affinity for fat, and a propensity to evaporate and travel long distances. Toxicity. The 12 POPs targeted for immediate action are all chlorine-containing compounds that belong to a class of chemicals known as organochlorines. Because of long-standing concerns about their high toxicity, this dozen are among the most widely studied synthetic chemicals. Numerous studies have shown that these POPs are dangerous not only at high levels, but at low levels as well. Short-term exposure to high concentrations can be fatal or result in serious illness. Lower chronic levels have been implicated in a wide array of health and environmental problems.

All 12 targeted POPs have also been recently identified as "endocrine disruptors," chemicals that can interfere with the body's own hormones. Such hormone-disrupting persistent contaminants can be hazardous at extremely low doses and pose a particular danger to those exposed in the womb. During prenatal life, endocrine disruptors can alter development and undermine the ability to learn, to fight off disease, and to reproduce.

Persistence. POPs are highly stable compounds that can accumulate and remain in the environment or in body tissue for years or decades before breaking down. Chemicals characterized as "persistent" resist the natural processes of degradation—by light, chemical reactions, or biological processes—that would eventually render them harmless. Sometimes, as with DDT, the breakdown products, notably DDE, prove far more stable and persistent than the original pesticide. The body cannot readily excrete persistent contaminants except through breast feeding, so most of the targeted POPs typically have long half lives in the body and with continued exposure their concentrations grow higher over time. Persistent contaminants are now pervasive in the food web, with animal products—meat, fish, and milk, in particular—the primary routes of human exposure.

Affinity for fat. POPs are not soluble in water, but they dissolve readily in fats and oils. Because of their resistance to degradation and this affinity for fat, POPs accumulate in the body fat of living organisms and become more concentrated as they move from one creature to another onward and upward in the food web. In this way, extremely small levels of such contaminants in water or soil can magnify into a significant hazard to predators who feed at the top of the food web such as dolphins, polar bears, herring gulls, and people. In Lake Ontario, for example, the tissue of herring gulls may contain 25 million times the concentration of PCBs found in the lake's water.

Global travelers. POPs share a notable physical and chemical characteristic that makes them highly mobile and capable of traveling to the ends of the Earth. These compounds are semi-volatile, a property that allows them to occur either as a solid or a vapor depending on the temperature. Once a persistent contaminant has evaporated, it can travel great distances in air masses, often hitchhiking on particles in the atmosphere like dust.

Through a process known as the "grasshopper effect," persistent chemicals jump around, evaporating in warm conditions and then settling in cool spots. When the temperature is right, POPs will again take flight and continue hopscotching travels that carry them anywhere and everywhere on Earth. Scientists detect them wherever they look in the world, even in regions where these synthetic chemicals have never been used. The pesticide toxaphene now contaminates fish in wilderness lakes in the Canadian Arctic, but there are no records of its use anywhere near that region. Toxaphene is often found in much higher concentrations than other organochlorines found in the Arctic. Persistent contaminants typical of industrial regions like the Great Lakes have been found in albatrosses on remote Midway Island in the middle of the Pacific. The penguins in Antarctica have become contaminated with a breakdown product of the pesticide chlordane and other persistent chemicals.

Emerging concerns. In the ongoing investigation of synthetic chemical hazards, scientists have come to understand how two particular characteristics of the 12 POPs under discussion—their tendency to accumulate in fat and their hormonal activity—combine to pose a special danger to the next generation. Throughout a woman's lifetime, the store of persistent contaminants mounts in her body fat. By unfortunate coincidence, the demands of pregnancy and breast feeding draw down these fat reserves, so a load of contaminants a mother has taken decades to accumulate passes on to her baby in a very short time. Even worse, these hormone-disrupting contaminants hit the baby at the most vulnerable period in its entire life.

During early development, hormones orchestrate key events such as sexual differentiation and the construction of the brain, so synthetic chemicals that interfere with hormone messages, including all the targeted POPs, can disrupt development and cause lifelong damage. In one study on dioxin, a fetus proved 100 times more sensitive to this hormone-disrupting POP than did an adult. A single low dose of dioxin to a pregnant rat at a critical moment in pregnancy did permanent damage to the reproductive systems of her pups, which showed notably diminished male sexual behavior and a sperm count drop of as much as 40 percent. The dose used in this experiment is very near the levels of dioxin and related compounds reported in people in industrialized regions such as Europe, Japan, and the United States.

Pervasive Harm

Following the ban or restrictions on the use of certain POPs, contaminant levels have declined from peak levels in many industrial countries over the past three decades. Not all trends are favorable, however. Contrary to the widespread impression, POPs are not an old problem that has already been addressed, let alone solved. A recent study of North Pacific minke whales found increasing levels of contamination from chlordane and PCBs—an indication, according to the research team, of "continuous fresh input of PCBs and [chlordane] in the North Pacific marine environment." Whatever the trends, environmental levels remain high enough to continue to affect people and wildlife. The existing global burden of POPs must be reduced and eliminated as quickly as possible.

Although some POPs-related studies have taken place in developing countries, few if any provide baseline data on levels and effects of POPs. Therefore, up to this point in time the bulk of the data has come from studies undertaken in industrialized countries. Resources must be provided to fill these critical gaps in POPs-related data. This is all the more urgent as exposure of people and wildlife to POPs in the developing world can be much more direct—at or near the point of release—than in the industrialized world. The lack of such baseline work, however, should in no way delay action on POPs.

Effects on Wildlife

An extensive body of scientific evidence documents the devastating toll of persistent contaminants on wildlife. In many parts of the world, wild species show signs of disrupted sexual development and a diminished ability to reproduce. Some sensitive species have disappeared altogether because of total reproductive failure linked to chemicals on the POPs list.

Threatened beluga whales. In the St. Lawrence River, the beluga whales suffer from an astonishing list of afflictions—several kinds of cancer, twisted spines and skeletal disorders, ulcers, pneumonia, bacterial and viral infections, thyroid abnormalities—seldom if ever seen in belugas living in less polluted water. Although levels of persistent contaminants in the river have dropped markedly in the past three decades, the belugas still show high levels of the targeted POPs, especially the young who acquire the contaminants from their mother's milk. One young whale found dead had 10 times more PCBs in its body than the level necessary to qualify as hazardous waste under Canadian law. Ongoing research on this population indicates that widespread hormone disruption is undermining reproduction and preventing recovery of the population.

Alligator abnormalities. POPs have also been linked to the stunted penises and reproductive failure in the alligators in Florida's Lake Apopka. Alligator eggs collected there had relatively high levels of a variety of contaminants, including toxaphene, dieldrin, and the DDT breakdown products DDE and DDD. Although the abnormally small penises are the most dramatic symptom, male and female alligators also suffer from profound but invisible disruption of their internal reproductive organs and from skewed hormone levels. A new study shows that these wildlife problems are not limited to Lake Apopka, which once had a chemical spill. The discovery of alligator hormone abnormalities and reproductive failure in other Florida lakes indicates that chronic contamination from agricultural pesticides may be as hazardous as acute incidents.

Lake trout crash. Based on persuasive new studies, dioxin now appears in part or wholly responsible for the extinction of the native lake trout in the Great Lakes. Fishery officials had blamed the trout's crash in the 1950s on overfishing, habitat destruction, and predation by an introduced parasite, the sea lamprey. But University of Wisconsin researchers have shown that trout eggs die when exposed to a concentration of as little as 55 parts per trillion of dioxin. Studies of the lake sediments indicate that contamination from dioxin and dioxin-like PCBs reached a level high enough to begin undermining trout reproduction in the 1940s.

Vanishing mink and otter. PCBs are implicated in the disappearance or decline of several animal populations in the United States and Europe. Mink began disappearing from the shoreline of the Great Lakes in the mid-1950s. Despite restrictions on DDT, PCBs, and other persistent chemicals, mink have not yet returned. Studies done by Michigan State University biologists have demonstrated that mink are highly sensitive to PCBs. British researchers have also linked PCBs to the parallel decline among otters in Britain and Europe in the 1950s: Their analysis, showing that otters have disappeared in regions downwind from major industrial areas, points to the likely role of atmospheric transport.

Recent work on the Columbia River in the Pacific Northwest region of the United States found delayed or inadequate reproductive tract development in male otters as well as a significant dose-response relationship between these problems and synthetic contaminants such as certain PCBs, dioxins, and pesticides. More heavily contaminated young males had smaller bones (baculums) within their penises as well as lighter testicles. The animal with the greatest burden of contaminants had no testicles at all.

Abnormal behavior in wildlife. Over the years, scientists have reported behavioral changes in wildlife contaminated with persistent man-made chemicals. In gull and tern colonies in the Great Lakes, the Pacific Northwest, California, and Massachusetts, field researchers have found nests with twice the normal number of eggs, which is a sign that the birds occupying the nests were two females instead of the expected male-female pair. In some Lake Ontario colonies, birds showed behavioral aberrations, including less inclination to defend their nests or sit on their eggs, which increased predation and diminished the hatching and survival of the chicks.

Marine mammal die-offs. Over the past decade, scientists have also documented that contaminants, such as DDT, PCBs, and dioxins, weaken the immune systems of marine mammals and that animals become more vulnerable to disease as they accumulate increasing levels in their bodies. Based on this evidence, it now appears that contaminant-induced immune suppression may have contributed to the dramatic marine epidemics that killed thousands of seals, dolphins, and porpoises in the late 1980s and early '90s. The dramatic die-offs hit populations in the Baltic and North Seas, the Mediterranean, the Gulf of Mexico, the North Atlantic, the eastern coast of Australia, and even the seals in Lake Baikal in Siberia.