By Molly M. Ginty
Monday, December 18, 2006
Across the U.S., female animals exposed to toxic chemicals are suffering from a flurry of health problems. As scientists examine the impact of environmental pollution, some are pondering what the results may mean to female humans. First of two parts.
(WOMENSENEWS)--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.
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.
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.
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.
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."
On Dec. 19, Women's eNews will run the second of this series, looking at the efforts taken to study the effects of these toxins on women.
Molly M. Ginty is a freelance writer based in New York City.
Natural Resources Defense Council:
Our Stolen Future:
Silent Spring Institute:
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