Rapidly rising PBDE levels in North America

The most comprehensive assessment to date of polybrominated diphenyl ethers (PBDEs) in the breast milk of North American women indicates that the body burden of Americans and Canadians is the highest in the world, 40 times greater than the highest levels reported for women in Sweden. Some scientists are alarmed because North American levels of PBDEs, which are used as flame retardants in consumer goods and have been banned by the European Union (EU), appear to be rising at an exponential rate.

The levels of PBDEs in North Americans appear to be doubling every two to five years, says Mehran Alaee, a research scientist with Environment Canada. As the principal investigator for the toxic substance research grant being used to investigate PBDE exposure in North America, Alaee is the author of a previously unpublished graph that pulls together all of the human milk data amassed on the continent thus far (see Figure 1). Alaee stresses that this graph is based on preliminary data. Still, he says, the data indicate “that PBDEs will become a problem” if nothing is done to limit the release of the chemicals into the environment.

“This is clear evidence for an urgent need for a systematic study [to determine the] spatial distribution and temporal trends of PBDEs in human breast milk in North America,” Alaee adds. “This new data from Canada strongly supports the need for more information on the levels of PBDEs in breast milk in the United States and Canada,” agrees Linda Birnbaum, director of the Human Studies Division of the U.S. EPA’s National Health and Environmental Effects Research Laboratory.

However, “due to the limited number of samples and their diverse collection, the data [in Alaee’s graph] are only indicative and not demonstrative of any trend,” cautions Jake Ryan, a senior research scientist at Health Canada who collected some of the data presented in the graph.

The toxicology of PBDEs is currently under investigation, but research has established that PBDEs can be persistent, bioaccumulative, and toxic. They can cause liver and neurodevelopmental toxicity and affect thyroid hormone levels, Birnbaum says. Tests on mice conducted by Per Eriksson of Sweden’s Uppsala University show that PBDEs can cause neurotoxic effects similar to polychlorinated biphenyls (PCBs).

The new Canadian data are important because they show that PBDE levels are approaching those of PCBs, which have been proven to cause developmental problems in children, says Åke Bergman, chair of the environmental chemistry department at Sweden’s Stockholm University and one of the world’s leading PBDE researchers.

Scientists agree that some of the PBDE formulations used to protect consumer products from spontaneously igniting are more problematic than others. The penta brominated diphenyl ether (penta-BDE) formulation that is used almost exclusively in the United States is associated with the greatest number of health effects. According to Alaee, most of the PBDEs measured in the North American samples are from the penta-BDE formulation.

Working in collaboration with Benoit Patry of Health Canada, Ryan has been trying to amass more data by collecting human milk samples from across Canada. However, Ryan says that the process is taking much longer than anticipated. To expedite the process, the industrial producers of brominated flame retardants are holding a workshop to develop a preferred method of collecting human milk samples, says Bob Campbell, director of corporate regulatory affairs for Great Lakes Chemical Corp.

Some of the data on the graph come from human “milk bank” samples that have been collected in Canada every 10 years—the next year that data is scheduled to be collected is in 2002. The graph also includes pooled samples from New York State, Austin, Texas, and Denver, Colo.

The levels of 200 nanograms of PBDEs per gram of fat (ng/g) reported as the highest data point on the graph are so high that Olaf Päpke, the German scientist who collected the milk from women in Austin and Denver, sent samples to colleagues in Germany and Sweden to have them analyzed independently. Before those confirmations came back, Päpke “didn’t believe the result,” recalls Bergman, who says he was shocked when his lab verified the samples’ PBDE concentrations.

The North American data are “consistent with the higher concentrations of PBDEs measured in other environmental media—air, fish, biosolids, etc.—in North American versus Europe,” says Tom Harner, a research scientist with Environment Canada. Birnbaum agrees that the high levels are “not a surprise.”

As is the case with PCBs and dioxins, the main way people take up PBDEs is by consuming fatty animal foods such as meat, fish, poultry, eggs, and dairy products, Ryan says. “However, there may be additional food exposure routes for PBDEs, possibly in food processing, which are not found with dioxins or PCBs,” he notes.

The California EPA also has been collecting data on PBDEs, and the levels the state agency is finding in adipose tissue of women, 85 ng/g, are on a par with the data Ryan, Patry, and Päpke have collected, says Tom McDonald, a staff toxicologist at the agency’s Office of Environmental Health Hazard Assessment.

Environment Canada’s commercial chemical branches are currently evaluating the PBDE data, and the end result could be a recommendation to ban the chemicals, Alaee says. Based in part on the evidence that the levels of PBDEs were growing exponentially in Swedish women, the EU has voted to ban two PBDE formulations, octa-BDE and penta-BDE, by July 1, 2003, and a third formulation, deca-BDE, could be banned by 2006.

The graph showing that PBDEs were increasing exponentially as contaminants in Swedish breast milk samples over the past 25 years (see inset to Figure 1) was instrumental in getting EU lawmakers to agree to the ban, Bergman says. “It was one of the very last nails in the coffin [of PBDEs in the EU],” he recalls.

McDonald says the rapidly rising levels of PBDEs in human tissues illustrate the value of human milk monitoring programs to identify important emerging contaminants. He says that his colleagues at California EPA have been agitating for such a program for years, but there is as yet no U.S. program for regularly monitoring women’s breast milk.

Campbell, who is on the Brominated Flame Retardants Industry Panel of the American Chemistry Council, an industry organization, stresses that that more data will be needed to convince the industry that any PBDE formulations must be removed from the market. But he says that his company would “do the right thing”, if faced with sufficient evidence that its products were causing harm. The industry is voluntarily testing whether children’s exposures to PBDEs present any risk through the U.S. EPA’s pilot Voluntary Children’s Chemical Evaluation Program, he says.

In the meantime, Campbell stresses his belief that the high level of fire safety afforded by adding PBDEs to U.S. consumer goods outweighs the risk they pose to human health and the environment. —KELLYN S. BETTS