By Bill Chameides
Polybrominated diphenyl ethers or PBDEs: you've got `em whether you want 'em or not.
Halocarbons: The `Miracle' Compounds. Hardly.
In the mid-20th century, chemical engineers appeared to have hit upon the chemical industry's equivalent of gold. Unfortunately it turned out to be fool's gold.
The fool's gold was halocarbons. Chemical engineers discovered that they could take a hydrocarbon (a molecule composed of hydrogen and carbon atoms) and by replacing some of the hydrogen atoms with halogens like chlorine, fluorine, or bromine, transform it into a compound with amazing new properties -- compounds that worked, for example, as insecticides (DDT), refrigerants (Freons), and insulators (PCBs).
That discovery inevitably led to their introduction into the marketplace, and new technologies being such a kick, consumers embraced these new chemicals, often unwittingly, buying up the products that contained them without much thought.
The problem is that many of these halocarbons are extremely stable. While that stability is one of the things that makes them so handy in the first place, it is also responsible for their ability to accumulate in the environment and our bodies, and that can cause problems -- serious problems.
The discovery of these problems led to U.S. bans on the manufacture and use of many halocarbons. These include DDT, short for dichlorodiphenyltrichloroethane (details here [pdf], here, and here); Freons, which deplete the stratospheric ozone layer (details here); and PCBs (more in this video). Of course, the bans were a little like closing the barn door after the horse escaped, as many of these chemicals will persist in the environment for decades to come.
PBDEs: The Latest Halocarbon to Be Re-examined for Public Safety
Which brings us to polybrominated diphenyl ethers. PBDEs made their entrance into the marketplace in the 1970s as flame retardants. First used in TVs and mattress foams, PBDEs eventually found their way into lots of everyday products, including pillows, carpet padding, cushions, children's car seats, furniture, electronics, and appliances. (More on PBDEs here and here.)
In the 1990s, along with so many other halocarbons, scientific studies began to suggest that the use of PBDEs is probably not such a great idea. Because of their propensity to leach out and accumulate in indoor air and dust, PBDEs are present in just about every American (we Americans have 15-20 times more PDBEs than our European counterparts, by the way). And a variety of laboratory studies on mice and rats suggests that carrying PPDEs in our bodies is probably not a good thing: effects include impaired liver, neurological, reproductive and thyroid functions.
Two New Studies on PBDEs Underscore Dangers
The body of data documenting the dangers of PBDEs seems to grow with every month. Now two nails have been added to the PBDE coffin.
In a paper published last week in Environmental Health Perspectives, Kim Harley of the School of Public Health at the University of California, Berkeley, and colleagues report the first epidemiological evidence linking elevated concentrations of PBDEs to depressed fertility in women. Their study was based on blood tests and interviews with 223 pregnant women living in a low-income community in California. The authors found that women with higher blood levels of PBDEs took longer to get pregnant than women with lower levels.
The second study, slated for publication in the April issue of Environmental Health Perspectives, was led by Julie Herbstman of Columbia University's Mailman School of Public Health. Herbstman and colleagues found that children with higher concentrations of PBDEs at birth scored lower on IQ and developmental tests between the ages of one and six compared to children with lower levels at birth. (The drop in IQ is similar to what other studies have found for exposure to polycyclic aromatic hydrocarbons (PAHs) and lead; see related post).
What's Next for PBDEs and Fire Retardants
Deciding what to do about PBDEs in consumer products is not as straightforward as deciding what to do about many other halocarbons. As you know, fire kills, and fire retardants are supposed to save lives. Some argue that banning PBDEs could result in more deaths from fire than the deaths prevented from the contamination (others argue that fire retardants do not deliver on what they aim to do).
One solution has been to fine-tune our use of PBDEs. The chemicals have been produced in three different commercial mixtures: pentaBDE (containing on average five bromine atoms and used primarily in foams for cushions and mattresses), octaBDE (containing on average eight bromine atoms and used in plastics), and decaBDE (consisting of diphenyl ethers that are nearly saturated with bromine and used in plastics commonly found in TV casings). Because the penta and octa forms accumulate in fat more readily than decaBDE, and thus potentially pose more of a danger to human health, U.S. manufacturers voluntarily agreed to cease their production in 2004 while continuing the use of decaBDE.
Using decaBDE is not without risk, though. Scientific studies have shown that decaBDE by itself can be a developmental neurotoxicant and affect learning and memory behavior in rodents. In addition, decaBDE is known to break down into components that are found in pentaBDE and octaBDE, thus increasing potential exposure to the banned chemicals.
Because of such findings, Europe has banned the use of all PBDE mixtures. As an acknowledgment of problems here in the United States, some states have banned the use of deca. And late last year the U.S. Environmental Protection Agency announced commitments by the two U.S. producers of PBDEs that they will end the production, import, and sales of decaBDE for most uses by 2013.
But banning all PBDEs still doesn't solve the problem. Most of us will continue to be exposed to the chemicals for quite some time from products purchased before the ban. And U.S. and European bans won't stops PBDEs from being imported into America in manufactured goods from countries still using them.
And there is still the question of what to do about fire prevention without PBDEs. Industry, in partnership with EPA, is already on the case, looking for chemical replacements for PBDEs. But you may not find that reassuring. Why? Because scientists are finding that the replacements may pose a greater health risk [pdf] than PBDEs.
Heather Stapleton, a Nicholas School professor of environmental chemistry who studies halogenated fire retardants, believes a new wonder chemical to replace PBDEs is not the answer. What is needed in her opinion is a new paradigm that integrates fire safety into the design of consumer products rather than adding it after the fact (e.g, using materials that are inherently flame retardant and using flame retardants that are chemically bound to the materials they are protecting so that the retardants are less likely to leach out).
In the meantime, we are left to play Russian roulette with the stuff we buy. Do you know what chemicals are in that rug you bought last year for the family room? Or the computer you bought for your teenage daughter? Probably not.
Stapleton argues: "Consumers have a choice about whether or not they want pesticides in their food -- they can buy organic or non-organic. However, consumers do not have a choice about having halogenated flame retardants in their furniture and electronics. ... So many products produced for infants and toddlers contain these toxic chemicals. As a mother of a 9 month old, I'm frustrated by that fact."