Ikonomou 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.

The 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.

What 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.

What 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

Total 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. graph from Betts, 2002. ES&T; adapted from Ikonomou et al. 2002.

The 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 issue (Betts 2002).

In 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 EU—baning Penta—are unlikely to be reflected in Holman Island seal tissues.

Samples 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.

What 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.

The 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.

Intriguingly, Ikonomou et al. also show that PBDE levels in breast milk in Sweden have dropped since that country instituted control measures. This indicates 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.

The 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 Convention.

The 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.