Environmental Science & Technology
November 6, 2003


By Kellyn S. Betts

This week, the main U.S. manufacturer of two widely used flame
retardants announced that it was going to discontinue their use
as part of a voluntary agreement with the U.S. EPA. The
agreement was "based on potential concerns associated with the
continued use of the chemicals," according to a joint
statement. However, a paper published in Environmental Science
& Technology [ES&T] this week provides the first definitive
evidence that a third popular brominated flame retardant could
be the source of some of the persistent, bioaccumulative, and
potentially toxic chemicals in the environment that are
associated with the discontinuation of the other two

The EPA agreement with the Great Lakes Chemical Corp. of West
Lafayette, Ind., covered two widely used polybrominated
diphenyl ether (PBDE) flame retardants known as the Penta and
Octa formulations. The research posted to ES&T's ASAP website
this week deals with the Deca flame retardant, which is the
most widely used PBDE flame retardant in the world.

Until quite recently, most researchers believed that -- unlike
their long-embattled cousins the Penta and Octa -- the Deca PBDE
chemicals added to consumer products to increase their safety
posed relatively little risk to the environment. But the new
ES&T research is just part of a growing body of data showing
that Deca can be both toxic and persistent. Some researchers
contend that the weight of evidence is now tipping the scales.

"It's time for people to agree that Deca is not totally
inert...that it can be taken up and that it can be broken down,"
says Linda Birnbaum, director of the Experimental Toxicology
Division of EPA's National Health and Environmental Effects
Research Laboratory.

The evidence comes from a number of fronts. The ES&T research
by Heather Stapleton and Joel Baker of the University of
Maryland's (UMD) Center for Environmental Science and their
colleagues provides persuasive evidence that fish exposed to
Deca can metabolize it into the lighter brominated compounds
associated with the Penta and Octa flame retardant
formulations, which have also been banned in Europe. Deca could
also be breaking down into substances that are much more toxic,
including hydroxylated compounds or fully debrominated diphenyl
ethers, Stapleton and Baker say.

Deca can cause developmental neurotoxic effects, too, according
to research published in Toxocological Sciences (DOI
10.1093/toxsci/kfg210). Researchers from Stockholm University
and Uppsala University (both in Sweden) exposed neonatal mice
to bromodiphenyl ether (BDE) 209, the main compound in the Deca
formulation, on their third day of life. Those mice exhibit
altered behavioral patterns that worsen with age, they say. The
researchers have reported similar altered behaviors in mice
exposed to BDE-99, a compound in the Penta flame retardant

This paper is the first to show that Deca can have these
effects, Birnbaum says. "It surprises us. But they did have to
dose the animals on day three; the reason is because it took
time for the chemicals to migrate," she says. The researchers
suggest that the effects they observed from BDE-209 could be
the result of a metabolite, because they mirror developmental
disturbances usually seen when the mice were dosed with PCBs or
BDE-99 on day 10. Birnbaum notes that the data shown in the
paper might appear even stronger if the statistics were
compiled in a different way. "Clearly, we'd like to see the
results repeated," she adds.

The new research points to "somewhat of a different paradigm,"
according to Baker. While concerns about accumulation of PCBs
and dioxins are based on the chemicals themselves, the
metabolites are the issue with BDE-209, he says.

Researchers are also finding more evidence of Deca in the
environment, says Mark La Guardia of the Virginia Institute of
Marine Sciences (VIMS). La Guardia will be presenting research
at the Society of Toxicology and Environmental Chemistry
meeting next week showing that minnows in a Virginia stream are
taking up BDE-209.

The stream contained 50 parts per billion (ppb) of Deca, which
La Guardia says he believes are the highest numbers yet
reported. "This value surpasses the water solubility of 209 and
likely reflects association with particulates," says Rob Hale,
La Guardia's research adviser at VIMS.

The Deca flame retardant formulation is used in electrical and
electronic equipment, as well as automotive equipment,
construction materials, and textiles. In 2001, 56,100 metric
tons of Deca were used, making it the second most heavily used
brominated flame retardant in the world, according to the
Bromine Science and Environmental Forum (BSEF).

All of the PBDE flame retardant formulations take their names
from the number of bromine atoms in their major constituents.
Deca has 10, although the commercial Deca formulation also
contains compounds of different sizes; the same is also the
case with the Penta and Octa formulations. In addition to being
very large, the Deca molecules are extremely hydrophobic.

"The significance of this work from a fate and transport
perspective is that Deca-BDE is itself quite involatile and
less prone to atmospheric transport. However, the lighter
congeners are more readily transported -- we see them in the
Arctic," says Tom Harner, a research scientist for Environment
Canada, the country's environmental protection agency.

In effect, Stapleton and Baker's work shows that Deca can be
transformed into a persistent compound, says Ake Bergman of
Stockholm University in Sweden, who coauthored a paper showing
that Swedish recycling workers take up BDE-209 but that their
levels drop rapidly during their vacations. Bergman likens Deca
to DDT, which is readily transformed into a more persistent
compound (4, 4' DDE) in the environment.

Not surprisingly, the BSEF views the findings a bit
differently. The research "seems to counter the contention that
Deca debrominates in fish to form BDE-47 (tetrabromo diphenyl
ether) or BDE-99 (pentabromo diphenyl ether), the major species
typically found in fish. Also, the findings are favorable in
that the research seems to clearly support our extensive
research demonstrating that Deca is not well absorbed and, with
certainty, does not show signs of bioaccumulating," according
to a statement from the organization.

Stapleton and Baker used a BDE-209 standard from Cambridge
Isotope Laboratories to overcome the issues raised by the
Swedish researchers who first reported that a fish (in that
case, a rainbow trout) was metabolically debrominating the Deca
molecules by exposing the fish to the commercial Deca
formulation. Amelie Kierkegaard and her colleagues at Stockholm
University's Institute of Applied Environmental Research could
not rule out the impurities in that commercial mixture as the
source of the lighter brominated compounds they reported.

The UMD researchers exposed their fish to the BDE-209 standard
for 60 days and then fed them clean food for 40 days. Although
the researchers found no BDE-209 in the fish during either the
exposure or the subsequent "depuration" periods, they detected
peaks associated with lower-brominated compounds. They used a
cool on-column injection gas chromatography coupled with an
electron capture detector -- a technique they had devised to
overcome known problems posed by gas chromatography with mass

The fact that the lower-brominated compounds were detected
after the Deca was no longer being fed to the fish indicates
that the fish were metabolically debrominating the Deca. The
compounds found in the experimental group of fish, but not the
control group, include BDE-154 and BDE-155, which are
associated with both the Octa and Penta formulations. The
researchers also identified compounds that were homologues of
the Penta-, Hexa-, Hepta-, and Oocta-brominated molecules.

Stapleton and Baker found that the levels of a few of the
debrominated molecules, particularly the Penta homologue,
continued to increase after the fish were no longer exposed to
the Deca in their food. Mehran Alaee, a paper coauthor from
Environment Canada and a principal investigator for a study of
PBDEs in the Canadian environment, confirmed the findings by
gas chromatography combined with high-resolution mass

"We were just looking for PBDEs. It's possible that other
compounds could be formed in the carp that we can't measure
based on our extraction methods in the lab," Stapleton

Stapleton even back-calculated to prove that the brominated
compounds must have come from the deca. She showed that the
levels they found were above the detection limits for the food
fed to the fish, Alaee says.

Scientists have long suspected that the brominated flame
retardants were undergoing some kind of metabolic
transformation, because the amounts found in human and animal
tissues do not match the percentages in the commercial
formulations. "Some of the PBDE congeners were missing if you
looked for them," Baker explains. "That clues you in that there
might be some metabolism going on."

For example, the harbor seals in San Francisco Bay have a lot
of BDE-153 and 154, Birnbaum says. "There's a little bit of 153
and 154 in the commercial Penta mix, but not very much. So are
[these congeners] coming from Octa, or are they coming from
Deca breakdown?" she asks.

"In nature, opportunities for uptake of Deca may be limited due
to its extremely low water solubility and large molecular
volume. However, clearly [La Guardia's] work and some of that
examining 209 burdens in humans show that this opportunity
does, in some cases, exist," Hale points out. Carp appear to be
particularly good at debrominating the PBDEs, he says, noting
that the fish with the highest levels of PBDEs recorded to
date, which was discovered by VIMS researchers, is also a carp.
But he says it is extremely unlikely that carp are the only
fish able to do it.

Researchers have a wealth of evidence that Deca is breaking
down in other species and perhaps in the environment, Birnbaum
says. "We have data demonstrating that Deca can be broken down
in mammals," she says. A Stockholm University metabolism study
on Deca showed that rats transform the compound to Nona-BDEs
and hydroxylated metabolites, Bergman points out.

"There's lots of evidence from lab studies that UV light leads
to rapid degradation, albiet in organic vehicles," Birnbaum
continues. "The Swedes [also] have some evidence that there may
be some breakdown in sediments or sludge," she says. Additional
evidence that Deca is bioavailable comes from Arnold Schecter,
who detected the compound in human milk for the first time
(Environ. Health Perspect. 2003, 111, 1723-1729).

Stapleton and Baker say that they are planning to try to look
for other, non-PBDE breakdown products, including hydroxylated
compounds, in the next studies they conduct.

Copyright 2003 American Chemical Society