How Environmental Pollutants Are Causing Reproductive Problems
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This below story includes both parts of a two-part series.
In California, female sea lions are spontaneously aborting their fetuses.
In the Great Lakes area, mother gulls are sharing nests and raising eggs together because their male partners have forgotten how to parent.
In upstate New York, female frogs have as much testosterone in their bodies as males.
Scientists say these aberrations all share a common link: exposure to toxic chemicals called "endocrine disruptors," which pollute the air, soil and water.
"At the rate this pollution is going, we will likely have population decreases in many wildlife species, especially amphibians and fish that are more susceptible to toxins because their skin is constantly exposed to these chemicals in an aquatic environment," says Sarah Janssen, a science fellow at the New York-based Natural Resources Defense Council. "These animals serve as canaries in the coal mine for human females, teaching us how synthetic chemicals might affect our nervous system development, immune function, fertility and other health outcomes."
In the past six decades, U.S. manufacturers have unleashed an estimated 100,000 synthetic compounds into the environment.
When animals come into contact with these pollutants, which have been detected in rainwater and in the rivers and soil of even the most remote areas, they absorb synthetic chemicals into their bloodstreams and their bodies. Researchers are finding that the female halves of many species are displaying biological reactions.
Earthworms Dosed With Prozac
Synthetic compounds have been detected in even the simplest life forms. According to a 2006 study by the U.S. Geological Survey (USGS), earthworms now have an average 31 pollutants in their bodies, including perfumes, household disinfectants and the antidepressant Prozac.
"As you go up the food chain, the numbers or relative amounts of synthetic chemicals can be even higher," says Diana Papoulias, a USGS biologist in Columbia, Mo. "Mammals, in particular females, have more fat in their bodies than other animals and therefore can have more toxins in their fat."
Years after they were created and put into common use, many synthetic chemicals were found to be endocrine disruptors, which means they interfere with the action of hormones that regulate animals' growth, development and fertility. These chemicals are of particular concern to female animals, since their hormones, like those of human females, fluctuate more than those of males.
Common endocrine disruptors include pesticides, phthalates (which make plastic flexible and make cosmetics adhere to the skin) and polychlorinated biphenyls (PCBs, industrial cooling agents banned in the United States in 1979 but still present in the environment.) Individual chemicals such as these -- or groups of them working together -- are making animals' hormones go haywire.
In Washington state, endocrine disruptors have been tied to the deaths of mother orcas, whose orphans have been adopted by other female whales. Some waterfowl and fish are experiencing 'feminization' from chemicals.
In Alaska, they have caused female polar bears' ovaries to shrink.
In Massachusetts, they have lowered the over-winter survival rates of female tree swallows.
In Florida, they have accumulated in the milk of mother dolphins, poisoning and killing their calves.
In addition to harming female animals, endocrine disruptors can cause the "feminization" of males. In Arizona, these chemicals have shrunken the gonads of largemouth bass and common carp. In the Midwest, they have spurred male waterfowl to grow female organs. In Washington, D.C., they have caused male fish to produce eggs.
Small Amounts, Big Impact
Just as alarming as these problems is the low level of exposure at which they are occurring. When Tyrone Hayes, an assistant professor of biology at the University of California, Berkeley, studied the endocrine-disrupting properties of atrazine, a common weed killer, he discovered reproductive abnormalities in affected leopard frogs at 0.1 parts per billion parts water, 30 times less than the Environmental Protection Agency's limit for atrazine in drinking water.
Though proof that endocrine disruptors can harm female wildlife is mounting, scientists say it is difficult to assess the total damage.
"In the wild, subtle outcomes such as length of gestation, litter size and the age of onset of puberty are difficult to ascertain," says Janssen. "You would have to know exactly when these females became pregnant and gave birth. You would have to anesthetize them to take blood samples. You would have to carefully observe and measure life events that are difficult to track in the field. Measuring these effects would ideally involve more controlled studies."
In laboratory settings, studies have repeatedly shown the adverse effects of some of the most prevalent endocrine disruptors.
Consider phthalates, those chemicals that help prevent makeup from smudging. In 2003, an Environmental Protection Agency study found these substances could reduce fertility in rodents, causing female rats to bear 50 to 90 percent fewer offspring.
Take bisphenol-A, a compound used to make everything from computer keyboards to dental sealants to food-can lining. A 2005 study by the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., found that exposure to this chemical can spur obesity in female rats. In August 2006, researchers at Tufts University in Boston found it can also cause breast cancer in female rodents.
There's also dioxin, a byproduct of paper manufacture and waste incineration. In 1998, researchers at the Washington-based Environmental Protection Agency found this chemical could trigger spontaneous abortions in rhesus monkeys. In 2003, a University of Ottawa study found it could also cause female primates to develop endometriosis, a disease that causes endometrial tissue normally found in the uterus to grow outside the womb.
More Questions Than Answers
As lab studies on endocrine disruptors continue, questions about what's happening in the wild persist. Why are mother sea ducks in Alaska producing fewer offspring? What's causing female dolphins in the Southeast to develop tumors in their reproductive tracts? Why are loon hatchlings in Wisconsin emerging deformed from their eggs?
Since only 10 percent of the synthetic chemicals in our environment have been tested on animals, scientists have yet to offer answers to these questions.
While research continues, some environmental advocates recommend that women avoid consuming fish and meat from the wild (such as carp caught in rivers or deer or pheasant shot by hunters) to avoid ingesting endocrine disruptors found in these animals' bodies.
Others recommend political action: calling for reduced emissions of synthetic chemicals, and calling on the Environmental Protection Agency to beef up its study of endocrine disruptors, a step Congress mandated in 1996 but one that the EPA has yet to take because it says setting up the research is proving more difficult than expected.
Because these chemicals also surround people, concern is building about their effect on humans.
"Animals don't use computers, apply makeup or use chemical solvents in their homes every day," says Theo Colborn, former director of the Wildlife and Contaminants Program at the Washington-based World Wildlife Fund. "In the end, female humans may be at even greater risk than female animals."
The Hereditary Consequences of Environmental Pollutants
It starts in the first weeks of life.
As the umbilical cord sends nutrients to the fetus, pumping 300 quarts of blood per day, it also delivers what nature never intended: synthetic chemicals that may wreak havoc with development and cause health problems later in life.
The Atlanta-based Centers for Disease Control and Prevention, which tests the "body burden" of chemicals every two years, finds the average American now has 116 synthetic compounds in her body, including dioxin (produced by burning plastic), polycyclic aromatic hydrocarbons (found in auto exhaust) and organochlorine pesticides (found in farming areas).
Recent studies have detected these pesticides, plastics and polymers not only in umbilical cord blood, but in the placenta, in human milk and in the bloodstreams and body fat of infants.
Though some of these chemicals pass through body systems in a matter of days, they maintain a long-term presence because exposure is constant.
Scientists say women are especially sensitive to synthetic chemicals because these substances can interfere with female hormone cycles and because they adhere to body fat that is more prevalent in women than in men.
In 2007, California will launch the nation's first statewide, voluntary biomonitoring program to measure chemical contaminants in people and find out which pollutants are most common in the state's residents.
The National Institute of Child Health and Human Development next year will also begin a $2.5 billion study to track children's exposures from birth to age 21, examining which chemicals are building up in the bodies of U.S. children and how they relate to individuals' susceptibility to different diseases.
While waiting for the results of these and other studies, health advocates are encouraging consumers to shun pesticides, remove outdoor shoes in the house, choose fragrance- and toxin-free products, use baby bottles that are free of a carcinogenic chemical called bisphenol-A and press authorities for stricter laws and more studies.
"Manufacturers are producing new chemicals all the time with little government oversight," says Julia Brody, director of the Silent Spring Institute, based in Newton, Mass. "We need tighter restrictions, like those in Europe, if we hope to protect the next generation."
One toxin threatening mothers and children is mercury, which can spur breast cancer, autism and attention deficit disorder. In 2002, a study found that 1 in 6 U.S. women of reproductive age has enough of this contaminant in her blood to endanger a developing fetus.
Researchers say infants and children are also at high risk, because at the time of early and rapid growth, susceptibility to pollutants can be greatest.
How these pollutants wound up in babies' bodies -- and what impact they may have on the next generation -- are the subjects of inquiry by a growing number of concerned scientists.
According to federal records, U.S. companies produce an estimated 75,000 chemicals; of those, 3,000 are produced in amounts of more than a million pounds per year.
All told, more than 100,000 chemicals -- some of them toxins that were banned decades ago -- persist in the soil, air and water. Whenever people come into contact with these substances, they can pass through the skin, nostrils or mucus membranes and into bloodstreams and body fat.
Some compounds can linger for decades after a single exposure. Take DDT, a pesticide that can damage the nervous system. In May 2006, the Seattle-based Toxic-Free Legacy Coalition tested Washington residents and found 80 percent had detectible levels of the chemical in their bloodstreams 34 years after it was banned in the United States.
'Increased Susceptibility' to Illness
"Our increased susceptibility to a variety of illnesses may be related not just to our exposure to these chemicals, but to exposures our mothers and grandmothers experienced during pregnancy," says Theo Colborn, president of the Endocrine Disruption Exchange, an environmental advocacy group based in Paonia, Colo.
The Washington-based Environmental Working Group in May tested mother-and-daughter pairs and found that each daughter had more chemicals in common with her mother than with other women. Because the mothers had decades more exposure, they had levels of lead, mercury and flame retardants in their bodies up to 5.2 times higher than their daughters.
To date, most studies on mother-to-child transmission -- and on these chemicals' long-term effects -- have been done on laboratory animals.
"It's unethical to experiment with these chemicals on people," says Shanna Swan, director of the Center for Reproductive Epidemiology at New York's University of Rochester. "And that's just one reason we don't have clear answers. There are hundreds of chemicals involved here, and studying just one of them costs upwards of $1 million."
Representatives of the petro-chemical industry say that until studies prove otherwise, there is little reason to worry about these compounds' negative effects.
"Finding a chemical in the body doesn't tell you anything about the source of the exposure, what caused the exposure or what risk it might pose at that level," says Sarah Brozena, a senior director at the American Chemistry Council, an industry trade association in Arlington, Va.
Some scientists are more cautious.
"There is extensive evidence of harm in animals and growing evidence of harm in humans," says Frederick vom Saal, a professor of biology at the University of Missouri-Columbia.
He points to an October 2006 study from Washington State University that showed damage caused by some pollutants could last for four generations.
Though scattered, studies on humans who were accidentally exposed to high levels of synthetic chemicals give a glimpse of their possible effects.
In 2000, a University of Michigan study found breast-fed girls exposed in utero to polybrominated biphenyls (PBBs, a type of flame retardant) started menstruating at an earlier-than-average age.
In 2002, a Taiwanese study examined men born to mothers who were exposed to polychlorinated biphenyls (PCBs, coolants banned in the U.S. in 1979). Researchers discovered the men's sperm were misshapen and could not swim as quickly or strongly as those of other men.
In 2005, Swan lead a University of Rochester study that examined phthalates, chemicals that soften plastic and help cosmetics adhere without smudging. She discovered that exposure to these compounds in utero resulted in the "feminization" of baby boys, who had smaller penises, shorter distances between the anus and genitals, and a higher risk for undescended testicles.
Health advocates suspect synthetic chemicals such as these may be linked to a whole flurry of health problems that have grown more common since industrialization surged in the past century.
They say pollutants may be partly responsible for the rising incidence of breast cancer, up 90 percent in 50 years and triggered in lab studies by organochlorine pesticides, mercury, PAH (found in auto emissions) and polyvinyl chloride (PVC, found in plastics).
Other health problems that researchers say may be linked to environmental toxins include male infertility, which has increased twelvefold in the past 80 years; prostate cancer, up 75 percent in 30 years; diabetes, which has doubled in the past 25 years; and obesity, which has doubled in the past 15 years.
Molly M. Ginty is a freelance writer based in New York.