With great blue herons, yellowlegs, and cattle egrets so abundant in the marsh that borders her property, Jane Chase was not surprised when her backyard was named a national wildlife sanctuary. The designation seemed particularly fitting because she and her husband have lived in a sanctuary of their own for nearly fifty years: the white clapboard house he built on Cape Cod when they were newlyweds. Their home has provided a haven for their six children and now fourteen grandchildren as well.

Yet lately Chase has been doubting the inviolability of that beloved home. Since becoming a grandmother, she has been diagnosed with breast cancer not once, but twice—and with two different kinds of cancer. She finds the dual diagnosis not at all unusual; many women in her 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 allow her home to be tested as part of Silent Spring Institute’s Household Exposure Study. In this groundbreaking 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 they reported in Environmental Science & Technology, the researchers detected a total of 67 endocrine disruptors 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. In a later feature story, the journal called the study “the most comprehensive analysis to date” of household exposures.

The researchers were not surprised to find phthalates—which have known effects on sperm quality and the development of baby boys—in all the homes, while parabens—an estrogenic class of chemicals that have been found in breast tumor tissue—appeared in 90 percent of the homes. What did surprise the investigators was their demonstration, for the first time, that alkyphenols, which are found in detergents, are abundant in indoor air.

“The finding of our widespread exposure to alkyphenols is troubling,” says Ruthann Rudel, senior scientist at Silent Spring, “because we know they are estrogenic. Even more alarming, though, is that no one has conducted enough research to know their full impact on our health.”

The study also provided what Rudel believes 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 researchers were also alarmed to find, in about 10 percent of the homes, impurities of one flame retardant that was banned in 1977 because it had been found to be a potent carcinogen.

Although the indoor air concentrations on Cape Cod resembled those reported elsewhere, the researchers did observe some regional differences in house dust. Polycyclic aromatic hydrocarbons, or PAHs, were lower than on Long Island but higher than in other regions of the United States. Concentrations of the pesticides DDT, carbaryl, chlordane, methoxychlor, propoxur, and pentachlorophenol appeared higher on Cape Cod than in other regions, while diazinon and permethrin levels appeared lower. Rudel points out that 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,” Rudel says. “We found DDT in dust in 65 percent of the homes even though it was banned thirty years ago. The fact that so many chemicals that were banned because of their health risks are 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 87,000 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.”

The Household Exposure Study is expected to yield even more results. To understand major pathways of exposure, for example, the researchers are now analyzing data on urinary levels of phthalates and pesticides in relation to air and dust measurements. They are also resampling more than a dozen of the homes with the highest concentrations of toxins, to try to determine the sources of the pollutants. And they will soon be reporting individual results to the study participants, to allow them to take measures if appropriate.

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.”