Toxic chemicals used as flame retardants are rapidly building up in the bodies of people and wildlife around the world, approaching levels in American women and their babies that could harm developing brains, new research shows.
The chemicals, PBDEs, or polybrominated diphenyl ethers, are used to reduce the spread of fire in an array of plastic and foam products in homes and offices, including upholstered furniture, building materials, televisions, computers and other electronic equipment.
This year, the European Union banned the two PBDE compounds that have been shown to accumulate in human bodies. Some European industries had already begun to phase out the chemicals, and levels in the breast milk of European women have begun to decline.
But in the United States, no action to regulate the flame retardants has been taken, and their use continues to rise. About half of the 135 million pounds of PBDEs used worldwide in 2001 were applied to products in North America.
Scientists who specialize in toxic contaminants say they haven’t seen a chemical build up in human bodies and the environment as quickly as that of PBDEs in almost half a century. The flame retardants are as potent and long-lasting as PCBs (polychlorinated biphenyls) and DDT-- chemicals that began to accumulate in the environment in the 1950s and were banned in the 1970s. Even if PBDEs were banned today, they would endure in the environment for decades, scientists say.
A single, small dose of PBDEs fed to newborn laboratory mice and rats disrupts their brain development, altering their learning ability, memory, behavior and hearing, according to three studies, two conducted in Europe and one at the U.S. Environmental Protection Agency. Mice fed less than 1 part per million of PBDEs performed poorly in maze tests and were hyperactive and slower to become habituated to new environments.
“These effects are persistent and worsen with age,” said Per Eriksson, a neurotoxicologist at Uppsala University in Sweden who led the rodent studies.
Only a few hundred people in the U.S. have been tested so far. But studies completed in the last few months show that some American women and their babies are carrying levels of PBDEs that are beginning to approximate those that harm newborn rodents.
The brains of newborn mice are altered when their bodies contain concentrations that are 10 to 100 times higher than levels already seen in some people in the United States today.
“That is not a comfortable margin of exposure,” said Linda Birnbaum, director of experimental toxicology at the EPA’s National Health and Environmental Effects Research Laboratory. Because concentrations in Americans are doubling every few years, it won’t take long to close the gap.
Scientists have not yet determined how the flame retardants are getting into human beings. Some suspect that dust in homes and offices containing foam from old furniture cushions is the primary source; others suspect it comes mainly from consumption of fish caught in contaminated waters. The uncertainty complicates the task of figuring out ways to tell people how they can reduce their exposure.
“We’re adding them to consumer products, so they’re in every home, every office, every car, every bus, every plane,” said Tom McDonald, a toxicologist with the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment.
Impact on Intelligence
Researchers say the effects on children are likely to be subtle -- not mental retardation or disability, but measurable changes in a child’s intelligence, memory, hyperactivity and hearing. “We’re concerned about learning and memory and some behavioral effects and hearing loss,” Birnbaum said.
The flame retardants, which pass through the placenta and are readily absorbed by a fetus, are doubling in concentration every two to five years in people and wildlife throughout North America, several studies show.
By far, the highest human exposures are in the United States.
A pregnant Indiana woman had the largest individual concentration found so far -- 580 parts per billion -- and her baby carried nearly as much at birth, according to an Indiana University study published last month. A San Francisco Bay Area woman in her 30s had amounts measuring nearly as much in another new study conducted by the California Department of Toxic Substances Control.
“The levels are rising, and as the levels rise, so should our concern about health effects,” McDonald said.
The federal EPA, which has jurisdiction over the chemicals, has made no move to regulate them. The agency has begun a risk assessment of the compounds, which is expected to be completed next year.
EPA Administrator Christine Todd Whitman said in an interview that she is concerned about the spread of PBDEs, but that “we just don’t know enough yet” to take any action, especially because the compounds help protect the public from fires.
Many scientists in the United States, Canada and Europe disagree. Two Cal/EPA scientists, writing in a scientific journal, have recommended a phase-out of the chemicals.
“Even in the absence of further studies, it seems clear that less toxic alternatives to the persistent PBDE flame retardants are desirable,” wrote McDonald and Cal/EPA scientist Kim Hooper.
Last month, Assemblywoman Wilma Chan (D-Alameda) introduced a bill that would restrict the use of PBDEs in products sold in California, beginning in 2006.
Firms Oppose Ban
Representatives of the four companies that manufacture PBDEs say they also are worried about the buildup in humans and the environment. But the companies oppose a ban, saying the compounds’ benefits to public safety are well known and their risks are uncertain.
“We are concerned about the findings, and we want to get to the bottom of this as much as the regulators and scientists do,” said Lawrie McLaren, program director for the Bromine Science and Environmental Forum, an industry group. “At the same time, you have a product with a proven benefit, as far as saving people’s lives, so one has to be very careful.”
If a fire occurs, products treated with flame-retarding chemicals provide as much as 15 times as much escape time as untreated products, according to the industry group. In Great Britain, a government report estimated that flame retardants on furniture saved about 1,800 lives there in a 10-year period.
Several dozen flame-retarding compounds other than PBDEs exist. Some of them do not accumulate in tissues and pose less risk. Electronics manufacturers already are switching to them or are altering their plastics so that retardants are unnecessary. But the chemical companies say there are drawbacks in some applications, including higher costs, less effective fire retardancy and reduced durability of furniture.
Exposure is probably highest in North America because it is the only place still using the form of PBDE most likely to accumulate in humans and the environment. That compound, penta-BDE, is banned in Europe but is used in the polyurethane foam of furniture and building materials in the United States. Much less is known about any health effects of PBDE compounds that are applied to computers and electronics equipment and whether they accumulate in bodies.
Great Lakes Chemical Corp., based in Indiana, is the only manufacturer of the type of PBDEs used in furniture and building materials. Albemarle Corp. of Virginia is the only other U.S. maker of PBDEs.
The exposure levels of tested Americans vary widely -- some people carry concentrations as much as 100 times as high as others -- and they follow no obvious geographic pattern. On average, however, Americans carry 10 to 70 times as much PBDEs in their breast milk, tissues and blood as Europeans do.
Of the melange of toxic chemicals that people and wildlife breathe, eat and drink, only three -- lead, mercury and PCBs -- are known to harm human health at levels found in the environment. The new studies provide evidence that PBDEs may be the fourth.
What disturbs scientists the most about PBDEs are their striking similarities to PCBs, which were widely used as insulating fluids in electrical transformers until they were banned in the 1970s because they were collecting in the tissues of people and wildlife.
Like PCBs and the pesticide DDT, PBDEs are slow to break down, persisting in the environment and accumulating in human and animal fat. PBDE concentrations increase as the chemicals move up through the food web, peaking in top predators such as whales, dolphins, birds of prey and humans.
“This will be a social experiment we’ll be following for the next 20 years. It is not going away,” said Hooper, a scientist at Cal/EPA’s Hazardous Materials Laboratory.
PBDEs mimic thyroid hormones, which regulate the growth of a baby’s neurological system. Because of that, if exposure comes during a critical phase of brain growth, it can alter how the brain develops, said Eriksson, the Swedish toxicologist. “There is a window of development when these compounds cause effects,” Eriksson said. In humans, that period lasts from the third trimester of pregnancy to a child’s second birthday.
Although EPA Administrator Whitman maintains that not enough is known about the effects of PBDEs to warrant regulating them now, Birnbaum, the EPA’s director of toxicology, said “there is no question” that the chemicals are altering thyroid hormones. Altering thyroid hormones during fetal development “can affect how the brain functions,” she said.
Also, Eriksson and other toxicologists say the flame retardants have the same effects as PCBs on the brains of newborn animals in the same doses.
In several studies, children born to women who ate large amounts of PCB-contaminated fish have been found to have reduced intelligence. Some women are carrying amounts of PBDEs comparable to the amounts of PCBs that reduce children’s IQs, toxicologists say.
“These are compounds that have the same properties as PCBs and DDT, and it’s just a matter of concentration before we have a toxic effect,” said Aake Bergman, Stockholm University’s chief of environmental chemistry and one of the world’s leading scientists regarding PBDEs.
Research teams at Stockholm University and other scientific institutions in Sweden have led the investigation of the flame retardants. The chemicals, developed in the 1970s, were first detected in the environment in 1981 in a river downstream from a textile manufacturing plant southwest of Stockholm.
As demand for flame retardants in electronics and furniture grew in the 1980s, PBDEs began to build up in nature and people, but few scientists thought to look for them. Then, in the mid-1990s, Swedish scientists checked women’s breast milk and discovered that levels of PBDEs had increased sixtyfold.
Stockholm University researcher Daiva Meironyte-Guvenius said the growth in breast milk “was very scary. The reaction here in Sweden was very powerful.” Facing public and political pressure, companies in Europe began to voluntarily phase out use of the most persistent flame retardants in the late 1990s.
PBDEs also are showing up in wildlife worldwide, settling in oceans and lakes just as PCBs and DDT did. Even polar bears near the North Pole and sperm whales feeding in deep ocean waters are contaminated with them. The effects on wildlife are unknown.
Ross Norstrom of the Canadian Wildlife Service, who has studied contaminants in wildlife for 30 years, said he was “flabbergasted” by the rapid buildup in North America: a doubling of PBDEs in Great Lakes gulls, trout in Lake Ontario and seals in San Francisco Bay every two to three years.
Some environmental scientists say the discovery of PBDEs near the North Pole proves their global spread, and that this should be an impetus for U.S. regulators to take precautionary measures as soon as possible. Many say they are dismayed that industry and society have forgotten lessons learned from the toxic legacies of the past.
“We knew less about PCBs when they were banned than we know about PBDEs today,” Bergman said. “Those of us who have been around for a while say, ‘Didn’t we learn from PCBs?’ ”