Endocrine disrupters ubiquitous in U.S. homes

Photo by Tanya Swann With the aid of researcher Jennifer Kachajian, the Silent Spring Institute collected samples of air and dust from inside 120 homes on Cape Cod, Mass.

The air and dust inside U.S. homes are likely to contain a wide variety of chemicals and pesticides that have been identified as endocrine-disrupting compounds, according to research posted to ES&T’s Research ASAP website this week.The most comprehensive analysis conducted to date, it reveals that many people may be continually exposed to dangerous levels of toxic substances, including chemicals like DDT and PCBs, which have been banned for decades.

This study, together with other data, shows that U.S. families may have “very widespread exposures” to chemicals that could affect the health of everyone from infants to senior citizens, warns Mary Wolff, of Mount Sinai School of Medicine in New York City. Currently, the U.S. EPA has no regulatory authority over indoor air or endocrine-disrupting chemicals.
The study was led by Ruthann Rudel of the Silent Spring Institute, a nonprofit organization based in Boston, Mass., as part of its ongoing Cape Cod Breast Cancer and Environment Study. The group measured concentrations of 89 suspected endocrine disrupters in air and dust samples taken from 120 homes on Massachusetts’ Cape Cod peninsula, where the state’s Bureau of Environmental Health Assessment has documented elevated incidences of breast, colorectal, lung, and prostate cancers.

The researchers found bis(2-ethylhexyl) phthalate (DEHP), which is “reasonably anticipated to be a human carcinogen”, according to the National Institutes of Health, in the dust of every home tested, at concentrations ranging from 16.7 to 7700 micrograms per gram (µg/g). DEHP is used in a wide variety of flexible poly(vinyl chloride) products, including children’s toys, shower curtains, raincoats, shoes, and floor tiles. The concentrations of DEHP in the dust of most of the tested homes exceeded EPA’s risk-based safety guidelines of 35 µg/g for residential soil, which are based on the compound’s carcinogenicity. There is scientific debate over whether DEHP is a human carcinogen, but the levels in some households also exceeded EPA’s guidelines of 1240 µg/g to protect against reproductive toxicity, Rudel says.

The study also contains the first reports of residential concentrations for 30 of the measured compounds, including 4-nonylphenol, an alkylphenol that can act like female estrogen hormones, and its ethyoxylates. Nonylphenol or nonylphenol ethoxylates are found in some laundry detergents, disinfecting cleaners, all-purpose cleaners, spot removers, hair-coloring and other hair-care products, and spermicides. The researchers found 4-nonylphenol to be one of the most abundant chemicals in the air of the sampled homes. It was discovered in every tested home at concentrations ranging from 21 to 420 nanograms per cubic meter of air (ng/m³).

The European Union (EU) Parliament has approved a directive that would restrict the use of 4-nonylphenol, but no EPA safety guidelines have been set for human exposure for it or any chemicals based on their endocrine activity.

“Finding the alkylphenols in air was a bit of a surprise because EPA and some documents from the manufacturers had suggested that you wouldn’t expect it to volatilize at all,” Rudel says. She adds that this is just one example raised by the study showing that reliance on using manufacturers’ claims by EPA and the U.S. Food and Drug Administration can be problematic. Wolff points out that “air pollutants don’t have to be volatile” because they can be adsorbed onto particles.

People have a limited exposure to nonylphenols through the use of products, and the daily intake is thought to be very low, according to the Alkylphenols and Ethoxylates Research Council, an industry group. Rudel says that the findings show that the compound’s potential for inhalation toxicity merits further investigation.

The researchers also documented the presence of some long-banned substances in the tested samples, including PCBs and the pesticides dieldrin, chlordane, and DDT, at levels that exceed federal risk-based safety guidelines.

4-4' DDT was one of the most abundant pesticides in the tested household dust. The scientists detected it in 65% of the homes at concentrations of up to 9.61 µg/g. Although they also detected some of DDT’s breakdown products, most of the chemical was in the form of DDT. “Since [DDT] really hasn’t been used in 30 years, it means it’s really not breaking down indoors,” Rudel says.

The results could help explain why the Centers for Disease Control (CDC) has reported that DDT’s breakdown product, DDE, is present in the bodies of youth aged 12–19 who were born after the United States banned the pesticide.

Another chemical measured for the first time in the study is 2,3-dibromo-1-propanol, a mutagenic and carcinogenic chemical that was found as an impurity in the TRIS flame retardant, which was banned in the late 1970s. Rudel is currently trying to solve the mystery of why the research team detected the chemical in the air of 9% and in the dust of 6% of the tested homes.

Other banned pesticides frequently detected in the homes included heptachlor (found in the air of 44% of the tested homes), pentachlorophenol (detected in the dust of 86% and the air of 58% of the homes), methoxychlor (in the dust of 54% of the homes), -chlordane (detected in 51% of the tested air in the homes), -chlordane (found in the air of 53% of the tested homes), and chlorpyrifos (found in the air of 38% and the dust of 18% of the homes). All of these banned pesticides were detected in some of the homes at levels that exceed EPA’s risk-based safety guidelines.

The Silent Spring team’s finding of high levels of the recently banned chlorpyrifos in some homes could also provide explanatory fodder for why CDC found that levels of this pesticide are higher in children aged 6–11 than in the rest of the population.

Although the presence of these compounds in the tested homes should set off alarm bells, Rudel stresses that the risk presented by exposure to the compounds could be much higher. EPA has developed toxicity guidelines for only 39 of the tested compounds, and the agency does not yet consider the impacts of exposure to mixtures of chemicals, she says. The agency does not regulate indoor air.

On average, the dust in the tested homes contained 26 different compounds and the air contained 19 different compounds. In a high proportion of the homes, the concentrations of at least one of compounds exceeded risk-based guidelines for safety developed by EPA, Rudel says.

Although the researchers took samples from the homes of breast cancer survivors and healthy women, they cannot make associations between cancer incidence and the levels of chemicals in the homes they studied because the sample size is too small and the samples were collected many years after the women were diagnosed. On the basis of values recorded in other U.S. studies, the researchers say that the levels they measured in Cape Cod are not significantly higher than elsewhere in the country.

Home contaminants are important contributors to people’s overall exposure and health effects because studies show that people in the United States spend 65% of their time in their residences, according to John Spengler of the Harvard School of Public Health, a paper coauthor. This figure holds true for most other industrialized countries, he says.
The Silent Spring researchers focused their efforts on looking for chemicals that are produced in high volumes in the United States and have been identified as endocrine disrupters in either whole-animal or cell-based tests. The pesticides measured in the study are regulated by the federal government, as are some of the toxic compounds, while others are candidates.

The study contains what Rudel believes to be the first report of the levels of the polybrominated diphenyl ether (PBDE) flame retardants in U.S. household dust. It shows that the levels of PBDEs in household dust are 10 times higher than the levels in Europe and higher than the levels of PCBs in dust in U.S. homes. “We know that levels of PCBs are going down, and the PBDE flame retardants are still being made and their levels of usage are increasing,” Rudel says.

Linda Birnbaum, director of the Experimental Toxicology Division of EPA’s National Health and Environmental Effects Research Laboratory, agrees that this finding is important. Three new animal studies show that BDE-99—the PBDE congener found in most abundance in household dust, according to the study—can have neurotoxic effects and that embryonic exposures can impair sexual development in addition to causing thyroid toxicity, Birnbaum adds.

The presence of contaminants like PBDEs and phthalates in household dust has significant health implications, Spengler says. Many studies of dust have focused on what crawling babies and children are exposed to, but he argues that everyone comes into contact with household dust. “Carpets are very effective at re-suspending materials,” he explains.

Spengler’s lab has conducted tracer measurement studies showing that approximately 10 µg/m³ of dust is suspended back in air, on average, from the dust that has settled. In this manner, dust can be continually redistributed throughout a home, he says. Vacuuming also re-suspends contaminants, says Rob Hale of the Virginia Institute of Marine Science.

The movement of household dust takes on added significance given that some of the toxic compounds measured in the study—particularly the phthalates and alkylphenols, which were found in the air or dust of every tested home—are present in high concentrations.

The Silent Spring findings also imply that people who buy used homes can be unwittingly exposed to the pesticides and chemicals used by the prior owners, Spengler says. “The real concern is, How does an individual get informed about the concentrations in their own home? It’s not easy for an individual consumer to get these measurements made—the laboratories that can make these measurements are few and far between, and they’re expensive measurements to make,” he explains.

In addition to measuring the carcinogenic and teratogenic DEHP, the Silent Spring researchers detected seven other phthalates, which are suspected of harming male reproductive systems by interfering with androgen function, in the homes they tested. As was the case with previous studies, the phthalate levels were very high—orders of magnitude higher than the levels of other contaminants (Environ. Sci. Technol. 2001, 35, 235A). For example, the researchers found a median value of 340 µg/g of DEHP in the dust they tested, while the median values for all of the other measured chemicals were less than 10 µg/g, if they were above the detection limits.

The new phthalate data also raise some new questions. In the past, most researchers doubted that inhalation was an important route of exposure for phthalates, but the new measurements suggest that inhalation may indeed be important, Rudel says. The phthalates that the researchers found in most abundance in the air of the tested homes—diethyl phthalate (DEP), which was present at a median level of 590 ng/m³, and di-n-butyl phthalate (DBP), which was present at levels ranging from 52 to 1100 ng/m³—are the same ones determined to be most abundant in human urine by CDC for a cross-section of U.S. adults.

When CDC’s results were first published, they were a surprise because they were not the phthalates that the National Toxicology Program had predicted that people would be most exposed to, Rudel explains. However, although DEP and DBP are not the phthalates used in greatest quantities, they are used in many personal care products like perfume and nail polish, she says. DBP is of particular concern because it is known to be a reproductive toxin. Although the risk-based safety guideline for DBP in air of 370 µg/m³ is significantly higher than the values the Silent Spring researchers recorded, Rudel says that the number is not based on the newest research.

“The phthalates and phenols are so widely used in commerce now that we’ve got to be concerned about this component of the body burden,” Spengler says, noting that other studies have shown that food and water are also sources. Phthalates and alkylphenols are the chemicals most urgently in need of further toxicity testing, agree Rudel and Julie Brody, executive director of the Silent Spring Institute and a paper co-author.

The study also points out the importance of considering the mixtures of chemicals to which people are exposed in their homes, say Rudel, Spengler, and Brody. The science of evaluating mixture toxicity is in its infancy, but European studies have shown that endocrine-disrupting chemicals can be evaluated as mixtures. Compounds that target the estrogen receptor site share similar mechanisms of action, and experiments show that the activity of mixtures of such compounds is indeed additive, Wiebke Meyer of the University of Bremen in Germany told attendees at a Society of Environmental Toxicology and Chemistry meeting in his native country this past May.

However, Meyer’s experiments, which are being conducted as part of the European Commission’s ACE project charged with “analyzing combination effects of mixtures of estrogenic chemicals in marine and freshwater organisms,” are based on evaluations of aquatic toxicity.

“The need to assess mixture toxicity is recognized by most environmental toxicologists, but the tools to do this, especially for complex mixtures, are lacking or poorly developed,” adds Paul Sibley, an assistant professor at Canada’s University of Guelph who is interested in aquatic mixture toxicology.

The mixtures of endocrine-disrupting chemicals to which people are exposed is likely to be more complex than what the Silent Spring study indicates, the researchers stress. “We just happened to look for 89 of these chemicals...but most chemicals that are actually in use haven’t been screened yet, so probably the true number of endocrine-active chemicals that people are exposed to is much, much higher than the number we came up with,” Rudel says.

The finding that a few homes had significantly higher levels of each chemical has significant implications for risk policy, Rudel says. For example, a few homes had concentrations of DBP and DEHP, which both have reproductive toxicity, that were far higher than in the other tested homes. “We typically go chemical by chemical and say we’re protecting the 95th percentile person, and if you actually look at these kinds of exposure data, there are a lot of people in the top 1–2% of the concentration distribution that you’re really not protecting,” Rudel says.

Rudel and Brody will consider themselves successful if their work provides impetus for rethinking such policies and conducting more toxicity tests. Although the reports on endocrine disruption by such influential organizations as EPA, the Endocrine Disruptor Screening and Testing Advisory Committee, and the National Academies, have identified the need for exposure information to help prioritize which substances should most urgently be evaluated, there are as yet very little exposure data, Rudel explains. This new data, says Birnbaum, give scientists a place to start.

Moreover, Brody adds, “Breast cancer research has really been hindered by lack of adequate measurements of the pollutants that women are exposed to that might be relevant to breast cancer, so this is really a necessary first step.”

The researchers are currently analyzing the relationships between the levels of phthalates and pesticides in the air and dust of different homes, and the amount of phthalates in the urine of the women living in those homes. They are also trying to track down the sources of some of the compounds measured in the study. —KELLYN BETTS