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Flame Fighters Filter Into Folks

Nature Network Boston

April 18, 2008

To prevent the spread of fire, manufacturers often add flame-retardant chemicals to common household products, such as TVs, stereos, and furniture. But over the past decade, researchers have found high levels of polybrominated diphenyl ethers (PBDEs), a common flame retardant, in humans and that concentrations have been doubling every five years. On average, the amount of PBDEs that Americans have in their blood is between 30 and 80 parts per billion (ppb), but some have up to 1,000 ppb.

Only a small number of studies have looked into the health effects these flame-retardant chemicals have on the body, but their prevalence in consumer products and their increasing levels in humans led Boston University researchers to investigate how they are getting into our bodies.

Tom Webster and Mike McClean’s group at Boston University’s Center for Interdisciplinary Research in Environmental Exposures and Health has been testing Massachusetts residents and their homes for PBDEs for the past few years. “There’s quite a lot of concern that the exposure of people to things indoors might be much more substantial than outdoors,” says Webster. “We’re trying to figure how people are being exposed to prevent exposure in the future.”

PBDEs are a type of persistent organic pollutant (POP)—they don’t easily degrade in the environment. They have been the major flame retardant used in furniture foam, small appliances, plastics for computers and TV cabinets, and other electronic devices since the 1980s. Unlike other persistent organic pollutants such as dioxin and PCBs, PBDE levels in humans have increased by a factor of almost 100 over the past 30 years, according to studies.

Dust carriers

Research from the last 10 years showing high concentrations of PBDEs in human breast milk intrigued Webster and McClean, so they began investigating how people could be exposed to PBDEs from household products. In 2004-2005, Webster, McClean, and graduate student Nerissa Wu gathered milk samples from 46 first-time mothers around Boston and vacuumed dust from their homes. They found that many women had high levels of PBDEs in their milk (30 ppb on average, and up to 263 ppb in some cases), and those levels were correlated with the amount of dust in their homes.

A few months later, Webster, McClean, and doctoral student Joseph Allen tested the air in the homes of 20 other Massachusetts residents and found that, compared with other rooms in the house, the air within a person’s immediate breathing space is most packed with PBDEs, probably due to the dust we kick up as we perform everyday activities.

Does exposure occur when we breathe PBDE-packed air or when we ingest dust via our hands? Webster’s group and collaborator Heather Stapleton at Duke University’s Nicholas School of the Environment and Earth Sciences wiped the hands of 33 people (including six children) with sterile gauze pads soaked in isoproyl alcohol to find out. Not only did every person have PBDEs on their hands—a median amount of 130 ppb—but some had extremely high levels—almost 2,000 ppb. “Finding it on the hands gives you an indication that it’s going from the dust to the hands and then probably incidental ingestion,” via oily finger foods such as French fries, activities such as nail-biting, or as a result of children putting their hands in their mouths, says McClean.

The team also wanted to know which products were the worst offenders. So Allen, Webster, McClean, and Stapleton developed a new technique whereby a handheld X-ray fluorescence scanner shoots X-rays at furniture, power strips, TVs, alarm clocks, DVD players, and other devices, and provides a spectrum showing the product’s levels of bromine. Bromine levels correlate with PBDE levels, and the team found that TVs had far more PBDEs than other products.

Questions unanswered

High PBDE levels in humans are worrisome, yet researchers still don’t know how much of a risk the chemicals actually pose to health. One of the few studies looking at the human health effects of PBDEs found that Scandinavian mothers with higher levels of the chemicals in their breast milk tended to have sons with undescended testicles. And animal studies have shown that large amounts of PBDEs (about 100 times the average human dose) are harmful to the endocrine system, reproduction, and neurodevelopment. But there are few other studies. “I’m not convinced yet that PBDEs are so harmful to humans that they need to be banned,” said McClean. “We don’t know enough about it.”

PBDEs are just one of many types of pollutants we encounter indoors, where we spend 69 percent of our time. “Still, I worry about PBDEs because they have turned out to be more toxic than first anticipated and they have disseminated widely,” says Philippe Grandjean, adjunct professor of environmental health at the Harvard School of Public Health.

Linda Birnbaum, senior toxicologist at the US Environmental Protection Agency (EPA), adds, “We’re beginning to find PBDE exposures in some people high enough to be similar to lab animals that have adverse effects.”

The EPA is currently compiling safe dosage levels for PBDEs. Eleven states have banned or phased out several types of PBDE, and many of the flame retardants have been voluntarily withdrawn from the market. The EU, which banned two types of PBDE in 2003, banned a third earlier this month. And some companies, such as IKEA, Sony, Apple, and Canon, have stopped using the chemical in their products. Yet PBDEs persist in older furniture and electronics.

“If we’re going to have flame retardants, they should stay in the product,” says Webster. “Either we redesign products so they don’t need the flame retardants or we design them so it doesn’t get into the home environment.”

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