Special Report Children at Risk
The young are harmed far more by toxic pollutants than adults, suggests new research on wildlife and humans
No one knows exactly why so few baby boys were born in the late 1970s and early 1980s to certain families in Seveso, Italy. But the answer may lie in a 1976 industrial explosion that spewed out the pollutant dioxin. Two weeks after the accident, the 735 people living in the most contaminated area, dubbed Zone A, were evacuated. In the following eight years, women from that group gave birth to far more girls than boys. At the time, researchers did not notice the phenomenon; they were more concerned with whether the dioxin might eventually cause cancer. Then excess cancers did start turning up among Seveso´s adults, and last year epidemiologists noticed in the data the strange scarcity of male children among Zone A´s previous residents.
Baby boys usually slightly outnumber girls; worldwide, there are about 106 boys to every 100 girls. But during the first eight years after the Seveso accident, mothers who had lived in Zone A gave birth to 48 girls and only 26 boys. Parents with the highest levels of dioxin had daughters but no sons at all. Perhaps, theorized University of Milan clinical pathologist Paolo Mocarelli last fall in the British medical journal The Lancet, dioxin interferes with hormonal balances in developing embryos, either making normal male growth impossible or killing males.
Mocarelli didn´t stumble upon the Seveso phenomenon by accident. He knew to look for it, in part, because scientists had already discovered in wildlife that toxics such as dioxin can affect sex ratios. "In wildlife, that is well known," he says.
Consider the famous case of crossed bills in double-crested cormorants in the Great Lakes region during the 1980s. Hatchlings with the deformity were almost always female, and scientists speculate the same chemicals that likely cause the crossed bills also were killing males before they hatched. Proof remains illusive, as unhatched embryos usually rot away in the shell before researchers can determine gender. But, says zoologist James Ludwig, a private ecotoxicology consultant in Canada and Wisconsin who examined the eggs, "If you assume there´s an equal probability that males and females will get the crossed-bill syndrome from exposure to toxic chemicals, then the males must be dying. Or the females are more sensitive."
POISONED WILDLIFE: Sickened and dying wild animals have long been harbingers of the effects of toxics in the environment. In the United States, we have paid enough attention to such messages to pass laws such as the 1972 ban on the pesticide DDT, as well as increase regulation of tox- ics such as dioxin and dioxinlike chemicals. As a result, many affected wildlife species are better off than they were 25 years ago, and presumably so are humans.
That´s the good news. So are the facts that U.S. children today are generally healthier and better nourished than at any time in history. But even with DDT, we are only now finding out just how dangerous that chemical is to human health--especially to children. While a great deal of uncertainty remains, a growing body of peer-reviewed scientific literature strongly suggests that the young of most, if not all, animals are far more susceptible to toxics than adults.
Not only can the young get heftier proportional doses of pollutants because of their small sizes and fast metabolisms, the exposures can impede development of rapidly growing bodies.
"Children eat, drink, and breathe more for their body weights than adults do, so they get bigger proportional doses of whatever is out there," explains University of Pittsburgh psychiatrist Herbert Needleman, who pioneered studies linking lowered intelligence with early childhood exposures to lead.
In 1993, the National Academy of Sciences concluded that infants and children are not sufficiently protected by pesticide regulations--in part because in many cases the risks have been calculated for adults. "That was a real wake-up call for us," says Environmental Protection Agency assistant administrator Lynn Goldman. Researchers are concerned about kids´ exposure to persistent traces of banned chemicals as well as to chemicals that continue to be dumped into the environment.
Not long ago, scientists considered cancer to be the main threat from exposure to toxics. Now there is new understanding that poisons also can affect the young´s immune systems, brains and reproductive organs--again, not only in wildlife, but in humans. "We have to be concerned about more than higher incidence of cancer," says National Wildlife Federation attorney Elise Hoerath. "The science shows a lot of other health effects we should look at closely."
That science, in many cases, starts with observations in the wild.
"It´s important for us to realize that if we´re seeing abnormalities in wildlife, similar kinds of mechanisms may exist in humans," says University of Florida zoologist Louis Guillette. "We are just another species in the ecosystem; if other species are harmed, we may be too."
Adds University of Missouri reproductive biologist Frederick vom Saal, "If these chemicals are causing animals to develop abnormally--getting into wildlife and causing changes in their brains, their behavior and their reproductive organs--we have to operate on the assumption that humans could respond in similar ways."
DEFORMED NEWBORNS: In the early 1950s, before anyone understood that the world´s first modern industrial pollution disaster was underway in Minamata, Japan, fishermen there noticed that seabirds were dying and feral cats that scavenged fish from the docks seemed stiff legged. Cerebral palsy and mental retardation started turning up in children, and adults were showing signs of illness. At first, people thought the symptoms were of a new disease. By the late 1960s, it was clear that mercury discharges from a chemical plant had poisoned the seafood--as well as those who
ate it.
"These poisons creep up on you," says toxicologist Bernard Weiss of the University of Rochester, who has studied the Minamata tragedy. "You see a few cases of animals dying or people getting sick. You catch a few clues. The evidence begins to mount." Weiss often calls such toxics in the environment "stealth poisons."
The problem has not been limited to Japan. In the 1970s in this country, scientists discovered widespread mercury contamination--though at far lower levels than the Minamata case--throughout the Upper Midwest and in fishing grounds along the Texas Gulf Coast. The extent of possible harm from mercury to people in this country is unclear, but one thing is certain: Children, especially those exposed to mercury before birth, are likely to suffer far greater damage than adults. (For more information about mercury pollution, see "Looking for Lessons from Loons," National Wildlife, August/September 1996.)
At the time of the Minamata poisonings, science held that the womb was a protected environment capable of screening out harmful substances. But in Japan, many women who ate contaminated fish without becoming obviously ill themselves, gave birth to children with severe mental retardation and physical deformities.
That led scientists to hypothesize that the fetus was sharing the mother´s toxic load. "It looks as though being pregnant sort of protects the mother, because the fetus takes up some of the mercury, reducing the mother´s exposure," says Weiss. The fetus receives at least the same doses as its mother--and the fetus has far greater susceptibility to toxic pollutants.
Not only are the young exposed to toxic chemicals in the womb, mothers also unload toxics in their milk. In milk from species ranging from beluga whales to dairy cows, scientists have measured concentrations of chemicals including dioxins, PCBs and various pesticides. Children get 12 percent of their lifetime exposure to dioxin in their first year of life. Notes EPA toxicologist Linda Birnbaum, "On a daily basis, the infant is getting about 50 times the exposure an adult gets, during what may be a critical developmental stage."
Of course, milk also provides important protection by passing along the mother´s antibodies, and doctors still recommend nursing when possible. In a long-term study in the Netherlands, researchers have found that children with higher levels of dioxins and PCBs in their bodies have more health problems--including immune-system and hormonal changes--than kids carrying lower doses. Of the kids who consumed mothers´ milk, those who had gotten higher doses of toxics did worse than others. But no matter the levels of contamination, children who were nursed did better than children who had not been nursed. "The benefits still clearly outweigh the potential risks," says Birnbaum. "The Dutch studies have supported that."
DAMAGED IMMUNITY: Along the west coast of Florida, in a stable population of bottlenose dolphins near Sarasota, nearly all the firstborn calves die before they separate from their mothers between the ages of three and six. In four generations over the past quarter century, only one firstborn calf--an orphan at the age of one--is known to have survived.
Biologists don´t know for sure why the dolphins´ firstborns are dying--or whether they have always died. But a series of studies worldwide over the past decade has revealed high levels of toxics in the fat of marine mammals. Research suggests mother dolphins unload as much as 80 percent of their accumulation of pollutants into each of their calves, probably through nursing. The firstborn gets the highest dose by far, as the mother has been accumulating toxics for many years.
Chemicals found in the Florida dolphins´ blubber include some of the most deadly and long-lived contaminants of the industrial age. Dioxins, a group of chlorine-based chemicals, are unwanted by-products of papermaking, incineration of chlorinated plastics and other industrial processes. Although PCBs were banned in this country in the late 1970s, they are still commonly found in electrical systems, where they were used for insulation. Leaks from the equipment into soil and water can move readily into food. The toxics are so persistent and widely distributed that people and other animals continue to be exposed worldwide. "What we are seeing now is the impact of damage that was done over the last few decades," says biologist Randall Wells of the Chicago Zoological Society, which runs the program that has studied the Sarasota dolphins for 26 years.
Now scientists are finding that these and other, still-manufactured toxic chemicals can interfere with immune systems. In 1987, more than 700 bottlenose dolphins, half of the migrant Atlantic population, washed up on beaches from New Jersey to Florida, and necropsies determined they were killed by infectious disease. The bodies contained high levels of PCBs, DDT and other immune-suppressing compounds, and those chemicals may explain the dolphins´ susceptibility to disease. "If these chemicals are damaging immunity in adult dolphins, they may be doing even more harm to juveniles," says immunologist Garet Lahvis of the University of Maryland School of Medicine. That´s partly because mammalian immune systems aren´t fully functional until months or years after birth.
A few disturbing links between pollutants and human immunity are currently under investigation. In the Canadian Arctic, Quebec community health researchers are attempting to tease out connections between unusually high rates of infectious disease among Inuit children and exposure to toxic chemicals. Even though no polluting industries operate near the region, contaminants enter the ecosystem in high-altitude winds and in migrant wildlife. As PCBs, pesticides and other organochlorines make their way up the food chain--from plants and fish to seals, whales, polar bears and humans--they accumulate in greater density in every link. Inuit women have seven times more PCBs in their breast milk than women from the urban, industrialized south of Quebec.
During their first year, Inuit babies suffer through 20 times more infectious diseases than babies in southern Quebec. Acute ear infections are rampant among the Inuit children, causing hearing loss for nearly one in four. And the usual childhood immunizations frequently don´t seem to work on these kids; they apparently can´t produce enough antibodies for vaccinations to take. Public-health workers stress that Inuit children are subject to many other risk factors--such as wood smoke in homes. That sort of complication is a common problem in human research. Researchers can´t control for every factor, and they obviously can´t deliberately expose humans to toxics. Frequently, scientists can´t distinguish which chemical might be causing a problem, because people are exposed to so many all at once.
But in Quebec, data suggests that contaminants may be at least partly responsible for the health problems. In a 1993 study, Quebec community health researcher Eric Dewailly found that babies nursed by mothers with the highest contaminant levels in their milk are afflicted with more acute ear infections than bottle-fed Inuit babies. The babies with the highest exposures also produced fewer of the helper T cells that play an important role in ridding the body of bacteria and other harmful invaders.
On the other side of the Atlantic, in the Netherlands, researchers concluded in 1995 that even infants with mild exposures to contaminants may experience weakened immunity. A study published in the journal Pediatric Research found a correlation between PCB/dioxin exposures and suppressed levels of disease-fighting white blood cells. Doctors who examined the children concluded that while the immune-system changes were not extreme, they "could persist into later child- or adulthood and could presage difficulties"--including autoimmune diseases that provoke the body to attack itself.
Immune-system difficulties also are showing up in non-mammalian species. Biologist Keith Grasman of Wright State University in Dayton, Ohio, measured a type of immune suppression mediated by T cells in prefledgling Caspian terns and herring gulls taken from contaminated colonies around the Great Lakes between 1992 and 1994. Says Grasman, "We are finding the same pollutants in our birds--PCBs and organochlorines" that have been measured in seals, dolphins, humans and other species with similar T-cell immune problems.
In some years, many chicks with suppressed immune systems die before they leave the breeding grounds. In other years, contaminated Caspian terns do grow and migrate south as they should, but most never return to breed. "We´ve banded enough of these birds in the nest that we would know if they were showing up in any significant numbers anyplace else," says Grasman. "They aren´t." He is now planning a multi-year study to learn whether the immunosuppression is leading to more deaths from disease among the birds.
LOWERED INTELLIGENCE: Not only are kids´ metabolisms faster than those of adults, babies don´t excrete contaminants or store them away in fat in the same ways that adults do. That means babies get continuous exposures at a time when all of their organs, including their brains, are still developing. In an adult, a blood-brain barrier insulates the brain from many of the potentially harmful chemicals circulating through the body. But in a human child, that barrier isn´t fully developed until six months after birth.
Many studies have found that developing brains of various wildlife species are far more sensitive to toxic insults than adult brains. In the late 1980s, for example, University of British Columbia zoologist Diane Henshel found gross asymmetries and other abnormal changes in brain structures of great blue heron hatchlings from dioxin-contaminated colonies in Canada.
Now evidence from an accidental PCB poisoning in Taiwan in 1979 is helping scientists establish that human children also are susceptible to such toxic effects. Eighteen years ago, in the Taichung province of Taiwan, more than 2,000 people were exposed to PCB-contaminated cooking oil in what has come to be called "Yu-Cheng" or oil disease. In the first three years after the accident, many newborns died outright, and others developed blotchy patches of dark skin and deformities of their fingernails and toenails.
As these children grew, tests found that many were slower mentally than other kids their age, and they were frequently hyperactive or had other behavioral problems. According to National Institute of Environmental Health Sciences (NIEHS) medical officer Walter Rogan, who has studied the Yu-Cheng case, the developmental delays and IQ deficits have not gone away as the children age. "And moms continue to have kids with problems," Rogan says. "The kids born as late as 1985 were still affected as much as the kids born in 1979."
As Rogan explains it, a large portion of the PCBs these women consumed ended up stored in their fat, as happens with many toxic chemicals. Because women mobilize a lot of body fat during pregnancy to provide nourishment for their growing babies, the contaminants in the fat also are passed to the children--even, as in Yu-Cheng, when the pregnancy occurs years after the mother´s exposure. The same mechanism also applies to low-level toxic exposures from food, air and water. Now researchers are finding that even these small amounts of pollutants--accumulated by women throughout their lives--can have lasting consequences for a child exposed to them in the womb.
The human evidence is not just from accidents where people were exposed to huge toxic doses, such as Yu-Cheng or Seveso. "Low levels of some of these chemicals are turning out to be more hazardous than we thought," Rogan says, "And the longer we look, the more problems we find."
A Michigan study published in The New England Journal of Medicine last September found persistent intellectual deficits in children exposed before birth to much lower doses of PCBs than the Yu-Cheng children. In 1981, two Wayne State University psychologists, Sandra and Joseph Jacobson, measured PCB levels in mothers and newborn infants.
Since consumption of fatty fish from contaminated water is a major source of PCBs, the Jacobsons selected mostly mothers who had eaten Lake Michigan salmon or lake trout regularly during the years before their children were born. The researchers found that infants with the highest exposures grew more slowly than other babies, and at four years old, the high-exposure group had poorer short-term memory. By the time the group reached 11 years old, the 30 most highly exposed children had average IQs six points lower than the least exposed group. And of the high-exposure kids, 23 percent were two years behind in reading, while only 10 percent of children with low prenatal PCB exposure were two years behind.
Unlike the Yu-Cheng oil poisoning, these were environmental level exposures, the kind anyone, anywhere, could have--not just people who live near the Great Lakes. Somewhat to their surprise, the Jacobsons found that fish-free diets didn´t necessarily guarantee lower PCB levels. "We had some very high-exposed children whose mothers didn´t eat the fish," Jacobson says. One guess is that those exposures might have come from other fatty foods, such as butter, cheese, beef or pork--but there is no way to know the source. "This is a societal problem," Jacobson says. "We are all walking around with PCBs in us."
SEXUAL IMPAIRMENT: Sexual development in the growing fetus may be as sensitive as the brain to toxic effects. When certain chemicals bind to hormone receptors, they can interfere with the work of natural hormones in signaling the body to develop male or female organs. When that happens, studies in the laboratory and in the wild have shown that any number of reproductive disorders can result. These chemicals, known as endocrine disrupters, include PCBs, dioxins and many pesticides.
Scientists are uncertain about the extent of effects of these endocrine-disrupting chemicals in levels found in the environment. But again, the growing body of evidence suggests reason for concern. Among the Yu-Cheng children of Taiwan, boys with high PCB exposures who have reached puberty tend to have smaller than average penises.
Four years ago, University of Florida biologists documented the same phenomenon among alligators born in a lake poisoned by a pesticide spill. And in 1989, in the highly polluted St. Lawrence River, biologists were stunned when they necropsied what they thought was a male beluga whale only to find a fully developed set of female organs--ovaries and a uterus--in addition to the whale´s male apparatus. Like other belugas recovered from the river, the hermaphrodite carried a tremendous load of endocrine-disrupting contaminants in its blubber.
In South Florida, of the 19 male Florida panthers that still survive, 13 have undescended testicles, a condition called cryptorchidism. Because these males produce abnormal sperm and have low sperm counts, the condition worries biologists fighting to save the endangered animal from extinction. Until the early 1990s, scientists blamed inbreeding for the panthers´ cryptorchidism and other health problems. But two years ago, former U.S. Fish and Wildlife Service environmental toxicologist Charles Facemire, now retired, published a hypothesis suggesting that endocrine-disrupting chemicals may be contributing to the cats´ problems.
The panthers are exposed to heavy doses of pesticides and toxic metals such as methyl mercury through their diet of raccoons, which ingest the pollutants in fish. "The scientific literature doesn´t support a connection between inbreeding in cats and all of these problems we see in the panthers." Facemire says. "But, based upon what we know from laboratory research and other species, everything that is wrong with the Florida panther could be attributed to pesticides." If so, the introduction in 1995 of female Texas cougars into South Florida to help improve the panther´s genetic diversity may not accomplish much. "If all of the panther´s habitat is contaminated." Facemire says, "then there might not be any saving of the animal."
According to a 1996 review by a team of U.S. and European scientists, birth data from several countries show "substantial increases" since the 1950s in the number of human boys born with undescended testicles and hypospadias, a condition where the urethra does not come out through the end of the penis. One London study, for example, found that 5.2 percent of low-birthweight boys born in the late 1980s had undescended testicles, compared with 1.74 percent of low-birthweight boys born 30 years earlier.
Testicular cancers are on the rise, nearly doubling among older teenagers in the United States between 1973 and 1992, from one in every 1,550 boys to one in 820 boys. Public-health officials are concerned that these conditions may be somehow linked to toxic chemicals, but they are a long way from finding proof. (For more information on endocrine disruptors, see "The Alarming Language of Pollution," National Wildlife, April/May 1995.) Many of the health effects documented in young wildlife may not apply to human children. But at the least, wildlife can give us a pretty good idea of where to look for problems and answers.
We don´t know yet what the message is, for example, from the scores of frogs found recently in Minnesota with grotesque deformities. Their problems could be related to parasites, radiation, ozone depletion, toxics or any number of other causes. Whatever the cause, the frog birth defects may yield clues about reasons for high rates of birth defects among the region´s farm children.
According to a 1996 study from the University of Minnesota published in the NIEHS journal Environmental Health Perspectives, in western Minnesota--where wheat, sugar beet and potato farmers rely on insecticides, herbicides and other pesticides to protect their crops--children of farm families had significantly higher rates of birth defects than the state´s general population. The highest rates were among children conceived in the spring, when spraying is most intense. And researchers found another oddity: Male babies had far more birth defects than girls.
Santa Fe, New Mexico, writer Vicki Monks is a frequent contributor to this magazine. For more about dioxin and widespread news reports that it is not as toxic as once thought, see Monks´ article "The Truth About Dioxin" in the August/September 1994 National Wildlife.
NWF: Tackling Toxics in Kids
Working toward a phaseout of the pollutants most dangerous to children is one of NWF´s top priorities. Among NWF´s many related efforts have been warnings about consuming contaminated Great Lakes fish and pressure for national standards for fish advisories. When Congress next revises the Clean Water Act, NWF will push for an amendment that will identify the most dangerous toxics and restrict or phase them out. NWF has also published three reports on the effects of toxic pollutants. For more information about those reports and NWF´s Great Lakes program, write NWF, 506 E. Liberty Street, Ann Arbor, Michigan 48104. Great Lakes web site: which can be found on our regional centers page.
Taking children´s risks into account in new regulations is no simple matter (see the item on a gasoline additive in this issue´s "News of the Wild"). Still, officials have taken important recent steps. Some examples: In February, the EPA announced a new Office of Children´s Health. Among its charges are studying the links between toxics and children´s health; working to see that EPA standards protect children; and setting new policies on kids´ exposure to pollutants. Last year, the agency proposed stricter air-pollution regulations to help address the skyrocketing problem of asthma in children. Also, Congress recently passed amendments to the Safe Drinking Water Act and the Food Quality Protection Act that for the first time require children´s health to be taken into account in assessing drinking-water standards and pesticide levels in food.
Share
