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Flame-proofing the Arctic?
Page 1 of 5
The authoritative voice of the environmental research community.
Table of Contents
Flame-Proofing the Arctic?
May 1, 2002 / Volume 36, Issue 9 / pp 188 A–192 A.
KELLYN S. BETTS
Scientists are perplexed by how quickly PBDEs are bioaccumulating in the
The polybrominated diphenyl ether (PBDE)
chemicals that are used as flame retardants in
consumer products appear to be contaminating
pristine sections of the Arctic more quickly than
either polychlorinated biphenyls (PCBs) or
dioxins, according to an article published in the
research section of this issue (1). Other recent
ES&T research provides insight into the
mechanism that allows the PBDEs to take such a
quick trip to the Arctic (2) and reveals that some
young children have significantly higher levels of
PBDEs in their blood than older people (3).
Åke Bergman, professor of chemistry at Sweden’s Stockholm University and one of the
world’s foremost PBDE researchers, calls the new ES&T papers a “really important” part of
an avalanche of data on PBDEs now entering the research literature.
PBDEs are accumulating in Arctic ringed seals at an unprecedented rate, according to
Michael Ikonomou, a research scientist at Canada’s Institute of Ocean Sciences and the lead
author of the paper published today. Ikonomou and a group of researchers from Fisheries and
Oceans Canada, a government agency, analyzed archived tissue samples taken from Arctic
ringed seals caught during Inuit subsistence hunts on Holman Island in the Canadian Arctic
between 1981 and 2000 for PBDEs, dioxins, furans, and PCBs. The oldest samples were
taken just a few years after PBDEs began to be used widely in both North America and
Europe, says Marcia Hardy, senior toxicology adviser to Albemarle Corp., a manufacturer of
flame retardants. The samples show that the concentrations of PBDEs in the ringed seals,
which are the most common seals
in the Arctic and the main prey of
polar bears, have been doubling
every 4–5 years, Ikonomou says.
The finding is particularly notable
because, while PBDE levels have
been increasing exponentially over
the past two decades, the levels of
dioxins, furans, and PCBs in
Arctic animals have been stable or
declining, he says. PCBs have
been banned for years, and
regulations governing dioxin and
furan emissions have tightened in
recent years, he explains.
PDBEs appear to be traveling more quickly to the
Arctic than PCBs or dioxins, according to the first
This is the first peer-reviewed
temporal analysis of brominated flame retardant
research showing PBDE
levels in Arctic animals. If current PBDE usage rates
accumulation in animals living
continue, researchers predict that the levels of
above the Arctic Circle, Ikonomou PBDEs in the Arctic will surpass those of PCBs by
says. Other studies have reported 2050. Source: Environ. Sci. & Technol. 2002, 36, 1886-1982.
high levels of PBDEs in fish in
Flame-proofing the Arctic?
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Virginia rivers (4) and Great Lakes fish, and scientists have presented data at a research
conference showing exponential rates of accumulation of PBDEs in beluga whales further
south in the St. Lawrence Seaway.
Ikonomou’s team also looked at PBDEs in crabs, sole, and marine mammals from the coastal
waters of British Columbia and found that all of the animal samples they tested had
significantly elevated levels of one specific PBDE molecule, or congener, BDE-47. Although
BDE-47 has only four bromine atoms, it is commonly found in the commercial Penta
formulation (which is not pure, but, as its name implies, mainly contains BDEs with five
bromine atoms) used in polyurethane foam in North America (5). All nine of the congeners
found in Ikonomou’s samples are known to be contained in the Penta formulation, Hardy
In fact, because Penta is the only one of the three PBDE commercial flame retardant
formulations (Penta, Octa, and Deca) containing congeners that tend to persist and
bioaccumulate in the environment, Hardy objects to the use of the general term PBDEs to
describe the chemicals of concern, although this practice has been established in the scientific
literature. Hardy acknowledges that Penta is indeed composed of PBDEs, but she argues that
the general use of the term PBDEs in the scientific literature to discuss effects associated
with Penta unfairly stigmatizes the other two formulations. The Deca formulation represents
80% of the worldwide volume of PBDE-based flame retardants and tends to be very stable,
Because the European Union has banned the Penta formulation (6), it is now used primarily
in North America, particularly in the United States, which has some of the world’s most
stringent fire-safety requirements.
The Penta congeners are most likely to get into the environment because they are added to
polyurethane foam padding material used in products like seat cushions, which tend to
crumble with age (7), Hardy says. Because the foam has an open-cell structure that air or
water can move into, there is more surface area that can be exposed, which allows the Penta
fire retardant embedded in the foam to escape into the environment, she says.
Testing of the commercial PBDE mixtures shows them to have low aquatic toxicity, but they
are suspected to be endocrine disrupters. A new study also shows that developmental
exposure to PBDEs can perturb thyroid function (8).
Some researchers suspect that more testing may be in order because the patterns of congeners
in the mixtures that have been tested don’t match with the occurrence of congeners found in
wildlife. “The data really suggest that the Penta source is North America, [but] what we’re
finding in the environment doesn’t look like commercial products,” explains Linda
Birnbaum, director of the Experimental Toxicology division at the U.S. EPA’s National
Health and Environmental Effects Research Laboratory. ’It’s really interesting that BDE-47
is the most common congener they’re finding out there in wildlife and in people, and BDE47 is not the major congener in any of the commercial products. The BDE-99 is much more
prevalent than BDE-47, even in the Penta formulation, and its levels are, in some of these
samples, very low compared to BDE-47.”
Hardy counters that the testing done to date predicts these results. BDE-47 typically makes
up about 70% of the “total PBDEs” detected in biological specimens collected in the
environment, she says. “If you look at a fish bioconcentration study done using the Penta,
you’ll find that the [BDE-47 does] bioaccumulate extensively. That’s probably related to its
uptake and how it’s handled by the body,” she explains. The main reason that BDE-99 does
not bioconcentrate as readily as BDE-47 is because BDE-99 is slightly less water-soluble,
she says. Additionally, she says, metabolism studies in rats and mice show that BDE-47 is
excreted very slowly.
The BDE-47 congener’s light weight helps explain its abundance in the Arctic environment,
Ikonomou says. “The atmosphere is distilling the most volatile congeners among those
present in the commercial flame retardant mixtures,” he explains, noting that the situation in
the Arctic is particularly complicated because PBDEs from both North America and Europe
are transported there.
Flame-proofing the Arctic?
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Although all of these factors help explain why the uptake of the PBDE congeners does not
match what researchers would expect to be in the environment, Ikonomou says the evidence
nonetheless points to some process that removes bromine atoms. The compounds may be
metabolized as they go through the food chain, or they may break down via photolytic
degradation in the presence of light, according to Ikonomou’s paper, which discusses some
potential debromination pathways.
“We believe that some of the BDE-47 in the Arctic may come from [the] higher brominated
compounds present in commercial mixtures such as the Penta, Octa, and Deca,” Ikonomou
says, stressing that he does not yet have enough evidence to support the hypothesis. But he
says he intends to observe the deposition patterns in the Arctic over the next five years
because the Arctic is the final resting place for PBDEs from both Europe and North America.
If BDE-47 remains the predominant congener in the Arctic, even though Europeans have
dramatically scaled back use of the compound, it will certainly strengthen the case for
debromination, he says.
Hardy says that it is far-fetched to speculate that the Deca product is degrading to lowerbrominated congeners, although she did not address the issue of whether Penta or Octa
congeners may degrade. To evaluate Deca’s potential for debromination, the Brominated
Flame Retardants Industry Panel (BFRIP), an industry group, has conducted studies of
anaerobic sediment biodegradation and photolytic degradation, Hardy says. Neither BFRIP
nor Swedish researchers have found evidence of anaerobic biodegradation of the Deca
product in sediments, she says, but she acknowledged that Deca will photodegrade into lower
PBDE congeners in an organic solvent. “However, we don’t typically see that combination of
events in the environment,” she says. “If we look at [Deca’s] potential to degrade into lower
BDEs in a more environmentally realistic matrix, we don’t find good evidence for that.”
Hardy adds that the levels of the PBDEs observed to date are too low to be cause for concern.
Researchers are nonetheless continuing to investigate whether photolytic degradation can
debrominate PBDE molecules, according to Birnbaum, Ikonomou, and Bergman. If evidence
of debromination comes to light, it should force the industry to begin testing to find whether
there are health effects from the patterns of congeners found in the environment, in addition
to the commercial formulations that have been tested to date, Birnbaum says.
“As stuff goes through the environment and through biotic systems, we are definitely getting
changes,” Birnbaum explains. “We need to look at the effects of the chemicals that we’re
actually being exposed to ... . The real question, it seems to me, is what are the potential
health effects from the chemicals we’re finding in wildlife as well as people, and at what
doses?” Because PBDEs are usually found in combination with dioxins and PCBs and
together these compounds may act synergistically (or antagonistically), Ikonomou says that
the compounds should be evaluated as mixtures.
The toxicology studies conducted to date show that the Octa mixture includes developmental
toxicity in rats and that the no-observable-effect level for Penta is 1 milligram/kilogram
(mg/kg), according to a recent article by Hardy (9).
Ikonomou and other scientists interviewed for this article nonetheless argue that there is a
pressing need for more toxicology data on PBDE compounds. Chris Metcalfe at Trent
University and Nigel Bunce of University of Guelph, both in Canada, and Abraham Brouwer
of the Institute for Environmental Studies in the Netherlands are among the few researchers
investigating PBDE toxicology, Ikonomou says.
Bergman argues that scientists already have enough evidence. “Bioaccumulation and
persistency is really enough. You do not need a lot of toxicological data. We do have some
toxicological data that indicate the PBDEs are as toxic as PCBs. They will cause a problem
sooner or later; sooner, if we let the levels increase,” he says. In that sense, what North
America does affects the entire world, he adds.
High levels in children
The new ES&T research showing that infants and children under the age of four in Norway
have levels of PBDEs in their blood that are 1.6-3.5 times higher than older people is yet
another reason for concern about PBDEs, Bergman argues.
Flame-proofing the Arctic?
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The research, which was conducted by researchers from the University of Oslo and Norway’s
National Institute of Public Health, “is showing dramatic increases over time,” Birnbaum
says. “The fact that young children are the ones with the highest levels, several times that of
adults is very important.... It’s further documentation of the dramatic increases in [PBDEs] in
another human population (10),” she says. That said, Bergman notes that the levels in
Norway are very low compared to what is being seen in the United States.
However, because the United States is not following the precautionary principle that guides
decision making about chemicals in the European Union, more data—including toxicological
data—will probably be necessary to persuade North American legislators to take action on
To collect the data that will be used to determine whether the compounds represent a
problem, North American scientists are following a different approach than the one
pioneered by their European colleagues, Ikonomou says. Instead of focusing on three or four
different congeners, the North American scientists have been taking a more holistic approach
by evaluating all detectable PBDEs, he explains, noting that some Europeans are now
beginning to follow suit. This holistic approach “will allow us to look at patterns in a more
detailed way and try to understand the transport mechanisms and fate of these compounds in
the environment,” he says. It will also allow us to evaluate the overall toxicity of these
compounds, as some of the congeners found in low concentrations may prove to be more
potent than the congeners found in higher concentrations, as is the case with PCBs, he adds.
Although exactly how the PBDEs are being transported up to the Arctic is not yet clear,
Ikonomou says he expects that PBDEs are governed by a mechanism similar to one that
sends pesticides to the far north, which has been documented in previous research by
scientists from Fisheries and Oceans Canada (11), although the vapor pressure and solubility
of PBDEs and pesticides differ somewhat.
The grasshopper effect
Further insight into the mechanism by which the PBDEs may be traveling to the Arctic
comes from new ES&T research by scientists at Trent University in Canada and Lancaster
University in the United Kingdom. Conducted by a group led by Todd Gouin and Doug
Mackay of Trent University’s Canadian Environmental Modelling Centre, the research
reports “surprisingly” high levels of PBDEs in air samples—the total PBDE concentrations
reached 1250 picograms/cubic meter (pg/m3), a level more than double the total
concentration of PCBs—taken from a rural site in southern Ontario. Their analysis shows
that the PBDEs, like PCBs, tend to oscillate back and forth between being airborne and
adhering to surfaces such as vegetation, a mode of atmospheric transport known as the
“grasshopper” effect that tends to move chemicals efficiently and rapidly. The researchers
believe they observed an “early spring pulse” transporting the PBDEs and PCBs from the
surface into the atmosphere as it warmed.
Gouin and Mackay’s findings are in accord with yet more new research into the physical and
chemical properties of PBDEs as a function of temperature (12), says Tom Harner, a research
scientist with Environment Canada, a governmental organization. “Our findings show that
PBDEs are special in that most of the dominant congeners (BDE-47, BDE-99, BDE-100,
BDE-153, etc.) exist in two states in the atmosphere—split between the gas phase and
partitioned onto aerosols. The temperature dependence of this particle-gas partitioning is
such that at warmer temperatures, the partitioning favors the gas-phase (more transportable)
and at colder temperatures, it favors partitioning onto aerosols (i.e., deposition).”
However, Harner says it is still unclear why this transport occurs more efficiently for PBDEs
than for PCBs, dioxins, or furans, all of which have similar partitioning behavior to the
PBDEs. He says the Gouin paper should lead to “some interesting debate however and
ultimately more process-related research to investigate the role of surface–air interactions
and ground cover type on ambient concentrations and atmospheric transport of PBDEs.” In
any case, it is clear that PBDEs are making it up to Arctic and moving up the food chain in
record time, Ikonomou says.
If PBDEs continue to be used at the same levels currently found in North America,
Ikonomou predicts that they will surpass PCBs as the most prevalent organohalogen
compound in the Arctic environment by 2050. Hardy declined to comment on that prediction,
but she acknowledges that the industry is keeping its options open by investigating new
flame retardants that can play the same role as the Penta formulation with polyurethane foam.
Flame-proofing the Arctic?
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“Polyurethane foam needs to be flame retarded,” she says.
1. Ikonomou, M.; Rayne; S.; Addison, R. Exponential increases of brominated flame
retardants, polybrominated diphenyl ethers, in the Canadian Arctic from 1981 to 2000.
Environ. Sci. Technol. 2002, 36, 1886–1892.
Gouin, T., Thomas, G. O.; Cousins, I.; Barber, J.; Mackay, D.; Jones, K. C. Air-surface
exchange of polybrominated diphenyl ethers and polychlorinated biphenyls. Environ.
Sci. Technol. 2002, 36, 1426–1434.
Thomsen, C.; Lundanes, E.; Becher, G. Brominated flame retardants in archived
serum samples from Norway: A study on temporal trends and the role of age. Environ.
Sci. Technol. 2002, 36, 1414–1418.
Renner, R. Flame retardant levels in Virginia fish are among the highest found.
Environ. Sci. Technol. 2000, 34, 163A.
Polybrominated diphenyl ethers—Environmental contaminants of concern. The
Standard 1999, 4, 2.
Renner, R. At odds over PBDEs. Environ. Sci. Technol. 2002, 36, 11A.
Betts, K. Mounting concern over brominated flame retardants Environ. Sci. Technol.
2001, 35, 274A–275A.
Zhou, T.; Taylor, M.; DeVito, M.J.; Crofton, K. M. Developmental exposure to
brominated diphenyl ethers results in thyroid hormone disruption. Toxicological
Sciences 2002, 66, 105-116.
Hardy, M. L. The toxicology of the three commercial polybrominated flame retardants.
Chemosphere 2002, 46, 757-777.
Betts, K. Rapidly rising PBDE levels in North America. Environ. Sci. Technol. 2002,
Macdonald, R. W.; Bewers, J. M. Contaminants in the arctic marine environment:
Priorities for protection. Ices J. Mar. Sci. 1996, 53, 537-563.
Harner, T.; Shoeib, M. Measurements of Octanol–air partition coefficients (KOA) for
polybrominated diphenyl ethers (PBDEs): Predicting partitioning in the environment. J.
Chem. Eng. Data 2002, 47, 228-232.
Kellyn S. Betts is a senior associate editor of ES&T.
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