With great blue herons, yellowlegs, and cattle egrets so abundant in the marsh that borders her property, Jane Chase wasn’t surprised when her backyard was declared a National Wildlife Sanctuary. The designation seemed fitting; for nearly fifty years, she and her husband have lived in a sanctuary of their own, the white clapboard house he built on Cape Cod when they were newlyweds.

Yet Chase has learned to doubt the inviolability of that beloved home. Since becoming a grandmother, she has been diagnosed with two different kinds of breast cancer. The dual diagnosis didn’t seem unusual; many women in her Cape Cod support group have developed more than one type of breast cancer. “Like me, these women have no family history,” she says. “And many of them have started to wonder whether their cancer could have been sparked by something in the air, the water—or even their own homes.”

With such lingering suspicions, Chase was quick to volunteer her home for Silent Spring Institute’s Household Exposure Study. In this ground breaking study, Silent Spring researchers took indoor air and dust samples from 120 homes on Cape Cod and measured the concentrations of 89 chemicals identified as endocrine disrupting compounds, which mimic or interfere with human hormones, sometimes affecting cell growth and development. The investigators’ selection was based on the chemicals’ wide use in pesticides, detergents, plastics, furniture, and cosmetics.

As reported in the October 15, 2003 issue of Environmental Science & Technology, the researchers detected a total of 67 endocrine disrupters in the air and dust, providing the first reported measurements in indoor environments for more than 30 of the compounds. The number of chemicals detected in the homes averaged 19 for air and 26 for dust.

The researchers found phthalates—which have known effects on sperm quality and the development of baby boys—in all of the homes, while parabens—an estrogenic class of chemicals that have been found in urine samples of almost all people tested—were found in 90 percent of the homes. The researchers also demonstrated, for the first time, that alkyl phenols, which are found in detergents, are abundant in indoor air.

In addition, the study provided what the researchers believe to be the first report of the levels in U.S. household dust of the polybrominated diphenyl ether (PBDE) flame retardants, found in carpets, draperies, electrical appliances, televisions, and computers. In the Cape Cod homes the researchers found PBDE levels to be ten times higher than in European homes, where these chemicals are being phased out because of their suspected toxic effects.

The U.S. Environmental Protection Agency has issued health-based exposure guidelines for only about half of the compounds in the study. For fifteen of those compounds—including ones that are currently banned—the researchers measured levels that exceeded the guidelines.

“Many of the chemicals we detected were banned many years ago, suggesting that they do not break down indoors,” says Ruthann Rudel, senior scientist at Silent Spring Institute. “We found DDT in dust in 65 percent of the homes even though it was banned thirty years ago. The fact that so many banned chemicals were still in homes suggests that we need to do more substantial testing before products are put on the market.”

No comprehensive list of endocrine disrupting chemicals exists, and most of the nearly 100,000 chemicals in use have not been tested to determine whether they affect hormone systems. “Not enough is known about the potential health risks from exposure to these chemicals,” Rudel says. “Part of the problem is that we tend to study chemicals that are regulated—and we regulate chemicals that are studied. So we end up looking at only a fraction of the chemicals we should be examining. One of our goals with this study has been to try to expand the universe of chemicals that receive regulatory attention.”

Jane Chase welcomes the information. “There are many women in my life I care very much about, and I don’t want them to have to go through breast cancer, too,” she says. “The more we know about what’s in our environment, both indoors and outdoors, the more precautions we can take.”