Nowhere to hide: the global spread of high-risk synthetic chemicals.

• Author: Mitchell, Jennifer D.

The mounting risks of exposure to synthetic chemicals - through accidental contact, bioaccumulation, and unpredictable synergies - suggest that the tens of thousands of compounds now at large in the environment can no longer be considered "harmless until proven guilty."

In August 1995, a group of middle-school students on a biology field trip in Minnesota were shocked to find that some frogs they had caught were grotesquely disfigured, with misshapen limbs and extra legs. The teacher reported their discovery to the Minnesota Pollution Control Agency in St. Paul. Since then, there have been reports of deformities in a large number of amphibians from widely scattered locations across North America - from Quebec to Texas, from New York to California. Tissue analysis by scientists at Augustana College in South Dakota indicates that the deformities found by the school children are not genetic mutations, but abnormalities that occurred during development. Something that happened to the frogs after they began to grow - perhaps something their mothers ate, or breathed, or came into contact with - caused their development to go haywire.

Experts have offered a variety of speculations: that parasites, radiation, ozone depletion, or some combination of such factors may be responsible. But scientists studying deformed frogs from the St. Lawrence River Valley and the Great Lakes Region are now giving particular attention to the role of man-made chemicals, which have become suspiciously pervasive in the places where such biocatastrophes occur. It is difficult, however, either to confirm or to eliminate such suspicions, because very few of the synthetic chemicals now present in the water and air were tested before they were released, to determine whether they cause developmental effects.

Non-testing - or incomplete testing - of chemicals, either because of limited resources or because of a lack of alertness to likely risks, is not new. In her classic 1962 book Silent Spring, Rachel Carson noted that synthetic substances were being released into the environment "with little or no advance investigation of their effects on soil, water, wildlife, and man himself." Since then, the situation has only worsened. U.S. farmers now apply twice the quantity of pesticides per year that they were applying when Carson published her book. But growing volume is only the beginning of this story, as the number of compounds has increased even more. Worldwide, an average of two to three new synthetic chemicals - their effects largely unknown - are released into the environment every day.

Despite some gaps in our understanding of chemicals and their interactions with living things, evidence from laboratory studies, observations in the field, and some tragic experiences with pharmaceuticals have provided sharp warnings that some of the "common" chemicals now so omnipresent in our homes and workplaces - in our food and water, our clothes, our carpets, our cleaning fluids and heating vents - may be dangerously undermining human, as well as ecological, health. Yet, these warnings have been largely ignored. History has taken us far past the point where we could envision living without some of the services synthetic chemicals provide, but it has also taken us to the point where we can no longer shrug off these warnings.

In less than one lifetime, production of synthetic organic chemicals - dyes, plastics, solvents, and the like - has increased more than a thousandfold in the United States alone: from less than 0.15 billion kilograms in 1935 to more than 150 billion kilograms in 1995. Today, there are roughly 70,000 different synthetic chemicals on the global market, and many others are emitted as by-products of their production or incineration.

Some chemicals, such as antihistamines, have direct health benefits, and some are innocuous. Others, such as pesticides, are designed to be usefully lethal. Many, however, are not meant to have toxic effects, or are not meant to come in contact with living creatures in any case, yet turn out to be both highly toxic and pervasive. For example, when polychlorinated biphenyls (PCBs) were created in 1929, they were intended only for use in electrical wiring, lubricants, and liquid seals. But old buildings are demolished and old machines are junked, and the residues that remain in them - some proving to be dangerously toxic - often leach into ground water. Today, these PCBs - along with more than 250 other synthetic chemicals - can be found in the body of almost anyone who lives in the developed world. Furthermore, since a mother will pass some contaminants on to the developing fetus during pregnancy, even an unborn child is at risk of exposure. It has been estimated that a mother's exposure to some persistent chemicals will still be detectable five generations later.

Exposure can occur almost anywhere. Pesticides such as Dursban and methoxychlor are sprayed in offices and schools without the knowledge of workers or students. Other chemicals are pumped into livestock and poultry or sprayed liberally over fruits and vegetables, only to show up on the dinner table. They are absorbed into the body through mouth contact with soft plastic toys or pacifiers, through skin contact with synthetic fabrics, and through direct consumption. Ironically, some of the chemicals most specifically intended to protect human health - by killing pests that would otherwise infest food - end up having the opposite effect: the residues accumulate in the tissues of people, who are vulnerable to long-term exposure, whereas the rapidly reproducing pests mutate fast enough to develop resistance.

Many of these chemicals will persist and build up in the environment long after they are released. For example, chemists estimate that the solvent chloroform, which is toxic to birds, fish, and. humans, will persist in water for 1,850 years. Yet it is continually being dumped into rivers or lakes via municipal waste treatment plants and accidental spills. Phorate, an organophosphorus insecticide, was used around a South Dakota wetland at only three-quarters of the recommended dose yet persisted through the winter despite assurances from the U.S. Environmental Protection Agency that it would degrade. The following year, it killed a number of waterfowl. The contaminated fowl were scavenged by bald eagles, which also died.

The most notorious of the persistent chemicals are organohalogens: carbon-based substances containing chlorine, fluorine, bromine, or iodine. The majority are chlorine-containing, or organochlorines. Around 11,000 organochlorines have been identified, most of which do not occur naturally. They include roughly 50 pesticides such as toxaphene and DDT (dichlorodiphenyltrichloroethane); solvents such as perchloroethylene; and multiple-use chemicals such as PCBs. However, the relative indestructibility of these chemicals, a boon for industry, has become a threat to the environment.

The problem is not just that these substances long overstay their welcome, but also that they concentrate. Most persistent chemicals do not dissolve easily in water. They are taken up by organic matter such as algae, and tend to build up in the fatty tissue of fish and wildlife that consume the algae. Concentrations continue to increase as the fish that ate the algae in turn are eaten by predators. In this way, a predator can actually end up bioaccumulating - storing in its flesh - a larger quantity of toxin over a period of time than would constitute a single fatal dose. Sometimes the final predator is a human sitting down to a plate of fish in a restaurant.

In just a few decades, synthetic chemicals have reached the remotest ends of the earth. They run off farmland or city streets into streams and sewers, are carried downstream, circulate in the air, and later fall as rain. On Midway atoll, located thousands of miles from Los Angeles, Tokyo, or Honolulu, and once thought to be a pristine environment, scientists have found DDT, PCBs, and dioxin-like compounds in the black-footed albatross in concentrations similar to those in bald eagles from the heavily contaminated Great Lakes. Researchers believe that the contaminants are coming from a plume of DDT off the coast of Southeast Asia (where the U.S.-banned chemical is still widely used), and from partly burned plastics from municipal incinerators in Japan and other Pacific Rim countries.

In a similarly disturbing discovery, investigators have found high levels of contamination in Northern Canadian and Greenland Inuit (Eskimo) villages. The PCBs and other persistent chemicals found in the Inuit people arrived by wind and water, and then reached...