How Environmental Pollutants Are Causing Reproductive Problems

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.