Fire retardants' effects arouse safety debate
TORONTO -- For more than 30 years, the stuff of American life -- computers and hair dryers, sofa cushions and auto dashboards -- has increasingly been built from plastic and synthetics treated with chemicals to slow the spread of fire.
And at alarming levels, researchers are discovering, those fire retardants are building up in our bodies as well. A growing body of research shows that the chemicals, known as polybrominated diphenyl ethers, or PBDEs, are rapidly accumulating in people's blood, in mothers' breast milk, and in animals as remote as Arctic polar bears.
Concern about the rising measures of PBDEs has prompted three states and the European Union to ban two of the three forms of the chemical. Canada just declared all three forms toxic. But as momentum builds, scientists and regulators are running into a nagging knowledge gap: Even the experts haven't proven PBDEs are causing humans any harm.
Last week, a conference on PBDEs drew nearly 200 researchers and academics from around the world to share research on the chemicals, which have been shown to cause reproductive and learning problems in animals. But firm data on human health effects remain elusive, and epidemiological studies are only now underway. The US Environmental Protection Agency has been evaluating and funding research into PBDEs, but has not decided that they pose an unreasonable risk to health or the environment.
In the absence of firm evidence on human effects, the movement to ban PBDEs is stoking a long-running debate over possibly toxic chemicals: How much evidence is needed before the government steps in? Some manufacturers and scientists say the known benefits outweigh a still-unproven threat, but proponents of the "precautionary principle" maintain that, in the face of uncertainty, suspect substances should be deemed guilty before judged innocent.
"By the time we actually do know, we're going to be dealing with 25 or 30 years of legacy and we can't do anything about it," said Joel Tickner, assistant research director at the Lowell Center for Sustainable Production, who argues for banning PBDEs and using safer alternatives.
Used since the 1970s, PBDEs have proved popular with manufacturers because they can make plastics flame-resistant without turning them brittle or otherwise changing their properties. "They're the most effective [flame retardants]," said Peter O'Toole, US program director for the Bromine Science and Environmental Forum, which represents the world's three manufacturers of PBDEs.
But scientists are growing increasingly alarmed about PBDEs because of their chemical similarities to a more famous family of chemicals largely banned a generation ago that continue to permeate the environment -- polychlorinated biphenyls, or PCBs. The industrial oils, invented in the 1920s, were widely used in fire extinguishers, hydraulics, and transformers because they resisted flames and would not conduct electricity. But they were discovered accumulating in animals in the 1960s, just before an accidental leak into cooking oil in Japan led to children born with a skin disease, growth problems, and hampered IQs. The United States banned their production in 1976. Only later did studies resolve the questions of how they became toxic in the body, and suggest links to cancer and to learning and memory problems in children.
In the 1980s, after PBDEs were measured in the environment, European scientists began to turn their attention to this newer class of chemicals. In the 1990s, studies showed them turning up in women's breast milk; a Swedish study found the levels had increased 60-fold from 1972 to 1997. PBDEs build up in fatty tissues, making breast milk a good indicator of both the mother's exposure and the chemicals in a newborn's diet. Studies since then have found American women's levels to be much higher than women's levels in Europe and Japan; researchers suspect that's because two of the PBDE manufacturers are located in the United States, and because Europe and Japan have been voluntarily phasing out some of the chemicals for years.
"I often say PBDEs are the poster child for the precautionary principle," said Tom Webster, a Boston University School of Public Health professor conducting an analysis of PBDE levels in Massachusetts women. Researchers point to animal studies that showed learning and behavioral problems in newborn mice fed PBDEs at particular points of development, stoking fears that PBDEs could cause learning disabilities and attention deficit disorder in children.
A new analysis compared the "body burden" of chemicals in American women with the levels that caused problems in animals. About 5 percent of the women studied had much higher levels of PBDEs than the others, and those women's levels approached the concentrations of concern in animals, said Thomas A. McDonald, of the Office of Environmental Health Hazard Assessment in the California Environmental Protection Agency. "They're pretty close, meaning the current margin of safety is small for these women."
Scientists are still trying to quantify how much of people's exposure to the chemicals comes from diet, or whether the chemicals, often found in household dust, are being inhaled. Researchers suspect some flame retardants leach out of plastics during the life of products. Typically, chemical exposure comes from diet, as pollutants in the atmosphere are taken in by fish, animals, and other wildlife, increasing in concentration as they move up the food chain to humans.
Some companies, not waiting for regulations, have already stopped using PBDEs. Dell now uses another flame retardant in its computer equipment, and the furniture maker Ikea has dropped them for alternative chemicals. But new chemicals also present unknowns, and there's an obvious cost-benefit analysis in the debate over a substance intended to promote safety. Untreated polyurethane foam was partly to blame for the fast-burning Rhode Island nightclub fire that killed 100 people last year; polyurethane treated with PBDEs burns more slowly.
Because of the difficult tradeoffs, regulators are remaining cautious about one of the three classes of PBDEs, known as deca, which the industry defends as benign. Maine legislators intended to ban all three compounds, but after resistance from the industry they approved a measure that says the state intends to ban deca in 2008 if a nationally available alternative is found. "They still gave themselves an escape valve," said the sponsor, Representative Hannah Pingree. "We were saying you must prove that this chemical is safe, which is, in a lot of ways, the way you wish you had gone with DDT or mercury or a lot of other things that took a lot of years of fighting and proving that there's something wrong with them."
Stephanie Ebbert can be reached at firstname.lastname@example.org
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