et al.document that polybrominated flame retardants are now
increasing exponentially in the North American Arctic, so rapidly
that they will overtake PCBs as the most prevalent organohalogen
contaminant in that region by 2050, absent changes in trends in
production and use volumes.
pace of PBDE increase is of great concern because PBDEs are classic
persistent, bioaccumulative compounds as well as potent
thyroid disruptors, in principle capable of interfering with
brain development and other processes mediated by thyroid hormone.
did they do? Ikonomou et al. measured PBDE levels in
Ringed Seal blubber in samples obtained on Holman Island, in Canada's
Northwest Territory (70°44' N, 117°43'W) during seal culls
in 1981, 1991, 1996 and 2000. Their analytical procedure allowed
them to distinguish between many of the different forms, or congeners,
of PBDEs,of which there are 209. They also measured PBDE congener
levels from harbor porpoise, Dungeness crab and English sole, obtained
elsewhere in Canada.
did they find? The central result is that PBDE levels in ringed
seals in arctic Canada are increasing at an exponential rate, doubling
every 4-5 years. This parallels increases in world-wide production,
as depicted in the graph below
PBDE levels in seals track world-wide production levels. Concentrations
in human milk in Sweden, however, have fallen after restrictions
on PBDE use were adopted in that country.
2002. ES&T; adapted from Ikonomou et al. 2002.
main PBDE congener contributing to the total PBDE concentrations
was BDE-47. This is significant because it is a form that is found
in the commercial "Penta" formulation of PBDE, which has
been banned in the European Union but is used heavily in the US,
especially in polyurethane foams. BDE-47, however, is not the dominant
congener in Penta and hence the question arises, why... if the source
of the contamination is Penta, why is BDE-47 the dominant congener
in seal tissues. It turns out that BDE-47's chemical characteristics
appear to make it more bioaccumulative than the more common congeners.
An accompanying news story in the journal in which Ikonomou et
al. was published carries a more extended discussion of this
examining the time trends in the graph above, Ikonomou et al.
comment on the fact that levels in the arctic seals were higher
than in human breast mile for approximately the period 1985-1996.
They take this as an indication of the high efficiency of long-distance
transport of BDE-47. They also note that air movement during the
summer, when temperatures are more favorable for PBDE volatilization,
carries air masses over industrial areas of North America and Japan
prior to reaching Holman Island, rather than over Europe. Hence
recent policy changes in the EUbaning Pentaare unlikely
to be reflected in Holman Island seal tissues.
of porpoise, crab and sole also revealed PBDE contamination, with
BDE-47 dominating but with other congeners being somewhat more common
in comparison to congener distributions in the seal tissues.
does this mean? PBDEs are poised to become the "next PCB,"
a persistent organic pollutant for the 21st century. Global transport
is rapid and efficient. They are bioaccumulative and some congeners
are persistent. Emerging toxicological information indicates they
are anything but inert, especially with respect to thyroid.
US regulatory apparatus and producing companies are resisting control
efforts, asserting that the flame-retardant properties of PBDEs
outweigh the currently understood risks. Europe has taken the first
steps toward reducing PBDE usage by banning one of the dominant
commercial forms, Penta-PBDE.
Ikonomou et al. also show that PBDE levels in breast milk
in Sweden have dropped since that country instituted control measures.
that concerted action to control PBDE levels would be successful,
if other countries would make similar decisions. Recent
moves by the US to avoid provisions in the Stockholm Convention
on Persistent Organic Pollutants that enable addition of new chemicals,
like PBDEs, make that unlikely, given current US attitudes.
trends measured by Ikonomou et al. indicate that PBDEs will
become the dominant organohalogen contaminant in the Arctic environment
by 2050 even though presently they are but 1/50th the level of PCBs.
This possibility should heighten pressures to begin finding alternatives
to PBDEs for retarding flames in consumer products, and to advance
PBDEs as one of the first, if not the first, contaminant to be added
to the list of persistent organic pollutants covered by the Stockholm
research effort on PBDEs fate and impact in the environment should
be moved forward urgently, with particular attention paid to the
behavioral and cognitive impacts of these compounds, both in wildlife
and humans. A significant component of this research should be directed
toward arctic ecosystems and arctic-dwelling people, as they are
poised to become the ultimate sink for PBDEs in the environment.