Chemical reaction.

Researchers are finding evidence that the chemicals we encounter in our everyday routines could be causing subtle but potent health problems other than cancer.

In the giddy, early days of this century's Chemical Age, companies such as Union Carbide and Dow trumpeted the miraculous powers of chemicals ("Better Living Through Chemicals") on billboards and in ad campaigns. And chemicals did bring miracles, from antibiotics, penicillin, and other medical advances to a range of creature comforts our ancestors could never have imagined: synthetic fibers, dry cleaning, spoil-proof food, crop-saving pesticides, contraceptives, contact lenses ... the list is endless. All in all, scientists have heaped more than 70,000 new chemical compounds on the bandwagon of progress, creating every imaginable convenience - and chasing every imagined ache or emptiness from our lives.

But these new creations have generated, along with all their benefits, a long list of problems, including serious health consequences. Our enthusiasm for new chemicals and the products and services they make possible has outstripped our attention to their long-term effects. While billions of dollars have been lavished on product development, marketing, promotion, and advertising, very little has been devoted to observing chemicals' interactions with living things and the environment. And these effects can never be thoroughly tested; the sheer number of combinations these chemicals now represent - in our food, water, clothing, and homes - are astronomical.

The research that has been done on chemicals' health effects has led environmental health experts to one fairly solid conclusion: there is an indisputable link between exposure to some industrial substances and certain serious diseases, particularly cancer. But some scientists are now beginning to look beyond the obvious - cancer and other easily diagnosable problems - to other health consequences of the Chemical Age. What they are finding puts a different face on the miraculous claims that we accepted without question in a more innocent era.

In the summer of 1991, for example, a group of American scientists and other experts met at the Wingspread conference center in Racine, Wisconsin, to talk about what was still just a hunch to each of them: was it possible that the chemicals encountered in people's everyday routines - from weed killer and bug spray to chemical-laced meat and dairy products - could be causing subtle but potent health problems other than cancer?

The scientists at Wingspread had been researching the connection between chemicals and serious health problems in wild animals or laboratory animals - health problems that could affect human beings as well. Few of the scientists knew about the others' research before the conference, and many were startled by the similarities in their findings. "The amount of evidence [for a link] was overwhelming," says Pat Whitten, an anthropologist who attended the conference.

While it is now widely accepted that certain diseases may result from exposure to hazardous substances - leukemia has been linked to benzene, an ingredient in gasoline, for example, and mesothelioma, a form of cancer, is considered a signature of asbestos exposure - the Wingspread scientists have continued to collect evidence that chemicals cause systemic damage by disrupting the functions of the endocrine system, which regulates hormones; the immune system, which defends the body against infectious disease and cancer; and the nervous system. Lowered fertility, abnormal sexual development, eccentric behavior, and lowered resistance to disease were among the health effects the scientists at Wingspread observed in wildlife and laboratory animals. Because most of the damage was so insidious, the scientists determined that similar effects in people might go unnoticed unless researchers specifically hunted for them. At the end of its meeting, the group called for a major epidemiological study to better assess the extent of subtle chemical damage to human health.

Some new advances in toxicology suggest that chemicals need not cause outright disease in order to have dramatic consequences. Other findings shed light on the potency of tiny exposures, and the extreme sensitivity of the developing fetus to chemicals. Since regulation of toxic chemicals has often been aimed strictly at preventing cancer and overt poisoning in adults, many subtle chemical effects on development, hormone regulation, the immune system, the nervous system, and reproduction have never been studied. "Our fascination with cancers has led us to underestimate [chemicals'] other health effects," says Theo Colborn, a World Wildlife Fund zoologist who helped organize the Wingspread conference.

The Chemical Load

Society has understood for centuries the dangers posed by many natural and synthetic substances, often through casual observation of diseases that have beset workers in various "dirty" industries. Lead's dangers, for example, were recognized by the Greeks and Romans. Hippocrates noted cases of lead poisoning among miners in the fourth century B.C. Dioscerides, a Greek physician, reported in the second century B.C., that "lead makes the mind give way." In the late 18th century, Sir Percival Pott, an Englishman, traced a connection between cancer of the scrotum, a hallmark of the profession of chimney sweeping, and the soot in the chimneys the sweeps scrubbed clean. Before their profession was outlawed for humanitarian reasons late in the 19th century, sweeps wedged themselves down soot-lined chimneys and in the process collected particles of cancer-causing coal tar in the creases and crevices of their bodies.

But by the early 1900s, modern industry was well on its way to surpassing the 19th-century industrialists' wildest dreams of progress, and in turn, chemical threats were crossing the boundaries of factories into everyday life. Industry had begun to produce synthetic chemicals by the 1920s, and some of these new chemical products, such as the notorious polychlorinated biphenyls - now commonly known as PCBs - eventually began to leach into the environment.

PCBs, first introduccd in the United States in 1930 and then banned in the United States, Canada and other industrialized countries beginning in the mid-1970s, were used for decades in electrical transformers, plastics, paints, varnishes, and waxes. By the 1950s, industry had invented formulas for thousands of important industrial compounds, some of which were as-yet-unrecognized toxins.

Among the toxic compounds were a number that contained chlorine, a building block in the production of many synthetic chemicals. In its gaseous form, chlorine proved useful to the chemical industry since it bonds readily with carbon. Between 1920 and 1990, U.S. production of chlorine rose ten-fold, and it now figures at roughly 11 million metric tons a year - a little less than one-third of world production.

Unfortunately, thanks to their chlorine-carbon bonds, many industrial compounds are quite stable and only break down slowly. These "organochlorine" substances are not water-soluble but do dissolve in fat. Like iron filings drawn to a magnet, these substances migrate to the reserves of fat stored in the tissues of fish, birds, mammals, and people.

In addition to creating brand-new hazards, 20th-century industry has coaxed many naturally toxic substances from rock and soil for use in manufacturing, and in the process released them into the environment. Industry's reliance on these metals has pushed more than 300 times as much lead, 20 times as much cadmium, and four times as much arsenic into the atmosphere than is naturally present. Roughly 13 million pounds of mercury drop from the atmosphere to the earth annually in rainfall, mostly as a result of industrial activity. Mercury readily evaporates, escaping into the atmosphere. Since minute quantities of cadmium, lead, and mercury have proved poisonous to the central nervous system, their potential impact is great.

No matter how far removed from the centers of industrial activity, people have been unable to escape exposure to this chemical brew. PCBs and DDT, for example, can be detected in the soil and in the bodies of wild animals almost anywhere in the world, as well as in people living in regions of the world still untouched by industry. Native American women living in Canada's Hudson Bay area carry roughly 3.6 parts per million of PCBs in their breast milk, compared to the one part-per-million average in industrialized countries. These women have such high PCB levels because they have diets heavy in marine mammals and fish, which store PCBs in their fat (PCBs are apparently carried north by the wind and absorbed by algae, plankton, cod, and then marine mammals). Women in industrialized countries commonly have dioxins and furans - chlorine-containing by-products of chemical manufacturing and waste incineration - in their breast milk.

To study chemicals' conflicting identities - are they miraculous agents of progress or a collective unknown evil? - It may be helpful to look to the United States, which is probably further along than any other country in the struggle to figure out where the progress ends and the dangers begin.

The Great Unknown

People are now exposed to thousands more chemicals than were their ancestors of a mere 150 years ago, but the world's understanding of how all these substances affect human beings is still elementary. A few years ago, the National Research Council (NRC) looked into just how much is known. It found that there is no information at all on the possible toxic effects of 80 percent of the 50,000 or so industrial chemicals (a category excluding pesticides, food additives, cosmetics, and drugs) used in the United States. And there are still many important unanswered questions about the remaining 20 percent. For chemicals produced in amounts exceeding 1 million pounds a year, for example, the council found that no testing had been done to determine whether there is potential for neurobehavioral damage, birth defects, or other toxic effects that might be passed on through several generations.

The NRC finding isn't surprising since the U.S. Environmental Protection Agency (EPA) does not require that industrial chemical manufacturers run specific tests to determine any adverse effects of their products before putting them on the market. Most chemicals, says Erik Olson, a senior attorney at the Natural Resources Defense Council, "are innocent until proven guilty."

The U.S. government took a step toward budding a bank of information on chemicals' health effects in 1988, when it passed a law requiring that EPA "re-register" (formally re-evaluate) 620 active ingredients in older pesticides by 1997. To re-register these substances, the agency has to review data supplied by manufacturers on their toxicity. But in many cases, the information did not exist or was completely outdated. As a result, EPA has so far been able to complete reviews of only 29 of the 620 ingredients it was charged to evaluate.

Though chemical manufacturers usually don't submit full reports on their products' potential toxic effects, independent researchers have documented some of them. Based on current scientific literature, the NRC estimates that one-third of the 197 substances to which a million or more American workers are exposed have the potential to be neurotoxic, which means they can damage the central nervous system and the brain. A partial list of these products includes many solvents, pesticides, and several metals.

Many common industrial substances - including benzene, dioxin, certain pesticides, and some metals - also have the ability to interfere with the immune system. Many organochlorines, including DDT, dioxins, furans, and PCBs, as well as the pesticides chlordane, heptachlor, and hexachlorobenzene, disrupt the endocrine system and impair reproductive abilities. While some toxic organochlorine substances have been banned in the United States and other countries, they can persist in the environment for decades, and many, like DDT, are still used in other parts of the world.

Though workers often have the highest exposures to these toxic compounds, other people are exposed through consumer products, through their drinking water, or by virtue of living next to a factory or hazardous waste site. Some 53 million Americans apply herbicides to their lawns and millions more use commercial bug sprays inside their homes. Shoe polish, glues, household cleaners, varnishes, and other everyday consumer products stored in the home contain neurotoxic chemicals. Some hazardous waste sites harbor neurotoxic chemicals that threaten the drinking supplies in nearby communities.

But little is known about the precise extent to which people are exposed outside the workplace to a given toxic chemical, let alone about the variety of hazardous substances in the environment. Experts are also unsure, in many cases, how much - or how little - of an exposure will produce subtle adverse effects in people. As a result, it is difficult to assess how likely it is that a majority of people may be suffering from exposure to a wide range of industrial substances.

However, there has been a good bit of research on lead and dioxin, two substances used heavily by industry, that supports the connection between industrial pollutants and health problems. Lead, undoubtedly the best-studied neurotoxin, has already dramatically affected the intellectual performance of children in many countries where leaded gasoline and other lead-based products are or were once common. And the latest research on dioxin and related toxins indicates that these compounds are capable of wreaking silent havoc on the endocrine system, the immune system, the nervous system, and reproductive functions of animals at levels of exposure that are perilously close to those encountered by the average American. The still-evolving stories of lead and dioxin should serve as fair warning to the scientific and industrial communities that progress has come at a substantial price.

Lead Weight

In the 1970s, the U.S. government banned the use of lead in gasoline and household paint. Two decades later, government officials estimate that one of every six children in the United States under the age of five has enough lead in her blood to be at risk for health consequences.

Although lead persists as a health problem in the United States, the U.S. government and the American medical establishment are still far ahead of the rest of the world in understanding and combating its effects. "Many countries in Europe have not yet reached the conclusion that lead is as much a hazard as it is seen to be in the United States," says Polly Hoppin, a senior program officer for pollution prevention at the World Wildlife Fund. Nonetheless, lead is a huge environmental health threat in many European countries as well as a growing menace in India, Mexico, Thailand, and many other developing countries.

An ubiquitous metal that is part of many different manufacturing processes, lead is still used even in the United States in batteries, fishing weights, ammunition, solder, ceramic glaze, aprons used by radiation workers, and in paint applied to bridges and the hulls of ships. Lead from waste dumps, airborne dust, peeling paint, and other sources settles into the soil as well. Despite the U.S. ban of lead-based household paint in 1978, the main source of lead "pollution" is still lead house paint: 3 million tons of old lead line the walls and homes of 57 million American homes, and 74 percent of all private housing built before 1980 contains some lead paint, according to the U.S. Department of Health and Human Services.

Louis Sullivan, secretary of Health and Human Services in the Bush administration, called lead poisoning "the number one environmental health hazard" for children, who are at risk of swallowing lead dust, paint chips, or contaminated soil, whether it be in dilapidated housing projects or old homes in upper-to-middle class neighborhoods. U.S. government researchers say that even small doses of lead can slow a child's development, and they have concluded that damage from regular lead exposure is usually irreversible.

Experts agree that lead's greatest danger to the general population is its effect on the central nervous system. Studies have shown that exposure to lead during childhood is associated with greater hyperactivity, impulsive behavior, aggression, and shorter attention spans, says Dr. Herbert Needleman, a professor of psychiatry and pediatrics at the University of Pittsburgh School of Medicine and one of the nation's top experts on the substance's adverse health effects. Because shorter attention spans have been linked to delinquency, "it is a reasonable hypothesis that lead exposure accounts for a meaningful amount of delinquency in the United States," says Needleman. Exposure to lead in the environment has already exacted a significant, but immeasurable, cost to society. "An enormous cognitive deficit across U.S. society has occurred and mill continue," says Paul Mushak, a professor of pathology at the University of North Carolina at Chapel Hill.

Lead can create IQ deficits of up to eight points in children, according to some studies, without any outward, recognizable signs of damage. Although people have recognized lead's toxic properties for 2,000 years, appreciation of the subtle damage wrought by low-level exposure is very recent. U.S. government agencies, such as EPA, the Centers for Disease Control and Prevention (CDC), and the Public Health Service, have lowered "acceptable" levels of exposure to lead by 75 percent since the 1970s. The CDC's new threshold for lead levels is 10 micrograms per deciliter of blood. Anything higher is likely to impair intellectual development.

The new CDC threshold does not mean that there are no permanent, toxic effects at lower exposures. A recent study by Dr. David Bellinger of Boston Children's Hospital found that children whose lead levels had averaged less than 10 micrograms at age five still had IQ deficits when they were retested at age 10.

Beyond nervous system damage, lead exposure may also impair fertility, cause menstrual disorders, and lead to anemia, high blood pressure, and kidney problems. But these effects occur mostly among workers in industries that use lead, according to Ellen Silbergeld, an epidemiologist at the University of Maryland's School of Medicine in Baltimore. Lead may also dampen immune responses, though research on this aspect of its toxicity has yielded conflicting results.

Most U.S. experts agree that ridding the environment of lead will be a gargantuan task. Houses with lead-painted interiors that are now in good condition will eventually deteriorate and threaten the country's children. The U.S. Congress recently approved $100 million in funds to help clean up lead hazards in low and moderate income housing, and Herbert Needleman believes that federal agencies have finally begun to alter their approach to the problem. "They're moving from finding a case and treating it to preventing lead poisoning in the first place." But, unfortunately, in lead-polluted countries that have yet to recognize the substance's dangers, children remain at great risk of being robbed of their intellectual potential.

Hormonally Driven

While the dioxin story is less fleshed out than the lead saga, dioxin may prove to have more effects on the human body. Outside the workplace, lead primarily threatens the central nervous system, but dioxin, an industrial by-product, appears capable of interfering with a number of physiological systems.

Dioxin is created by the paper industry's chlorine bleaching, by waste incineration, and as an unintended by-product of the manufacture of dacthal, a pesticide, and pentachlorophenol, a wood preservative. However, no one has been able to account for the sources of up to half the dioxin in the environment.

More than 90 percent of exposure to dioxin comes from food, particularly meat, dairy products, and fish. While dioxin commonly refers to a particular compound known as tetrachlorodibenzo-p-dioxin, or TCDD, there are actually 75 different dioxins. TCDD, the substance found in Agent Orange, a defoliant used widely during the Vietnam War, is the most toxic dioxin. Researchers now think that low-level exposure to dioxin damages the immune system and reproductive functions. Dioxin also appears to affect behavior and learning ability, which suggests that it is neurotoxic. As with lead, researchers have found that dioxin is most damaging to very young animals, especially those that are exposed while in the uterus.

In the 1980s, dioxin was widely believed to be the most potent animal carcinogen ever known. More recently, though, intense controversy has cropped up over the true nature of dioxin's toxicity in people. To resolve conflicting claims about dioxin's potency, EPA has embarked on an in-depth study. Instead of focusing just on cancer, the agency decided to examine all of dioxin's potential toxic effects - including those involving metabolism, behavior, the immune system, reproduction, and development of the fetus. The study will also analyze the contributing role played by related toxins, furans and dioxin-like PCBs. The findings are due out late this year.

So far, "much of the scientific data suggests that dioxin is no less dangerous than we thought it was before," says Linda Birnbaum, director of environmental toxicology at EPA's Research Triangle Park facility in North Carolina. But in the minds of Birnbaum and other toxicologists, concern over dioxin's potential effects on human reproductive and immune systems is now on equal footing with worries about its cancer-causing potential. Recent studies have found higher rates of certain kinds of cancer among workers exposed to dioxin. But if reproductive and immune system damage occurs at much lower levels of exposure than those associated with cancer, far more people may be at risk for these subtle effects.

Normal development and reproductive abilities in animals are apparently affected by dioxin when the chemical interferes by amplifying or diminishing the effect of natural sexual hormones at a critical point during pregnancy. Depending on whether it produces estrogen or testosterone, the fetus develops "female" or "male" features. Later in life, hormones direct sexual behavior and regulate fertility. "The slightest shift of the ratio of male hormones to female hormones will alter development irrevocably," says the World Wildlife Fund's Theo Colborn.

Some of dioxin's hormone-like effects on rat fetuses have been investigated by Dick Peterson, Thomas Mably, and other researchers at the University of Wisconsin. Male rats that were exposed to very small amounts of dioxin in the womb had smaller sexual organs, produced fewer sperm when they reached adulthood, and even exhibited feminine sexual behavior. For instance, when "mounted" by other male rats, they arched their backs and threw back their heads, a typical response of female rats during sex.

Researchers have also studied dioxin's ability to suppress immune system responses and its effect on learning ability. Robert Bowman, a retired psychologist who did research on dioxin when he was a professor at the University of Wisconsin, detected, for example, differences in the learning abilities of baby rhesus monkeys when their mothers were exposed to low, chronic doses of dioxin compared to monkeys that were not exposed. On the tests, which measured things such as the ability to differentiate colors, location, and shapes, the performance of exposed animals was diminished.

"It doesn't look to me like there's much, if any, margin of safety for some of these effects," worries Tom Webster, a biologist at the Center for the Biology, of Natural Systems at City University, of New York (CUNY). "We may be seeing developmental and reproductive effects at current levels found in humans."

Despite new research by EPA scientists and others, many questions remain about dioxin, not to mention the thousands of other chemicals that have never been studied.

Human Guinea Pigs

Scientists despair of the void in research on toxic chemicals, but there are plenty of experiments in progress around the world. Most of us are involuntary research subjects, exposed to not just one, but a wide variety of chemicals every day, some of which remain in our bodies for months or even years. (Dioxin lingers in the body for more than a decade.) If scientists know little about the effects of individual chemicals on the body, they are certainly ill-equipped to evaluate the combined toxicity of multiple chemicals. One study by the National Institute of Environmental Health Sciences compared the effect on mice's immune responses of a mixture of 25 chemicals commonly found in U.S. groundwater with the effects of individual chemicals. The researchers concluded that the potency of the 25-chemical mixture was greater than the individual strength of any one chemical.

What hazards are posed by simultaneous exposure to many potentially toxic chemicals? "We don't have a ghost of an idea," says Nicholas Ashford, a technology and policy professor at the Massachusetts Institute of Technology.

The shortage of studies on individual chemicals, or on the synergistic effects of several chemicals, has prompted some researchers to call for a more radical approach to the problem. "Put the paper industry on a chlorine-free diet and you'll get rid of a lot of dioxin," says CUNY's Tom Webster.

Webster and like-minded scientists argue that it's time to attack the problem at the source, reducing the levels of chemicals allowed into the environment in the first place, a strategy that would require redesigning the products or processes that use or produce chemicals. The chemicals they would target include benzene, chlorine, dioxin, formaldehyde, and lead.

"The science of this stuff is fascinating - we could probably spend the rest of our lives trying to understand how dioxin works," says Webster. "But is this really in the best public interest?"

There isn't a simple answer to his question. The EPA's reassessment of dioxin will provide a model for future studies of toxic chemicals' subtle effects on both adults and children and may very well be worth its $3-to $4-million cost.

On the other hand, is it fair to continue making people the unwitting guinea pigs in industries' quest for better, faster manufacturing and products? Shouldn't the burden of safety be placed squarely upon industry?

The philosopher Hannah Arendt once observed that it is the nature of evil to make itself appear unremarkable and commonplace. Likewise, chemicals now occupy such a comfortable niche in our lives that we fail to consider their dual nature. The time may have come to hold these life-changing substances to a far stricter standard and consider them guilty until proven innocent.

Ann Misch is a research associate with the Worldwatch Institute. She is currently studying the link between health and the environment.