That goes all the way back to 1993 and the initial survey work. One of my colleagues, Ulla Sellström, had analyzed a lot of samples from around the Swedish environment and the Baltic Sea, but the results hadn’t been pulled together. I sat down with her and helped to organize that. The end result was an article in Chemosphere, looking at levels and trends in the Swedish environment: in fish, mammals, birds, and sediments—whatever we had at the time (Sellström U, et al., "Polybrominated diphenyl ethers [PBDE] in biological samples in the Swedish environment," Chemosphere 26[9]: 1703-18, May 1993). We were trying to get a picture of how contaminated the environment was and what in particular was contaminated. That’s how we were able to start saying that levels are higher in marine mammals and marine birds that eat fish than they are in the fish themselves, which suggests this tendency for bioaccumulation.

At that point we started to ask the question, "Where is this stuff coming from?" So in the survey we had carried out, we knew that there was a river in Sweden that seemed to have high levels of PBDEs in fish. We went back to that river and looked at the fish and at the sediments at several different points upstream and downstream from various industries. We looked at textile manufacturers, in particular, because we suspected them of being the source. And as we suspected, the samples in both sediments and fish taken downstream from these industries had higher concentrations. When pressed, the textile industries admitted using these compounds and releasing them into the river.

This was also when we first started looking at the deca compound—as opposed to tetra and pentaBDEs. DecaBDE was in sediments but we couldn’t see it in fish. The industry was saying that deca was not a problem, that it was not going to be taken up in organisms and so could be used even at high levels. We decided to test that. We set up an experiment in the lab and used rainbow trout. We actually fed them with food containing decaBDE and looked to see whether it went right through them or whether it accumulated. That’s what we were reporting in 1999 in that second most-cited paper (Kierkegaard A, et al., "Dietary uptake and biological effects of decabromodiphenyl ether in rainbow trout [Oncorhynchus mykiss]," Environ. Sci. Technol. 33[10]: 1612-7, 15 May 1999).

Some, but not a lot. What was interesting is we thought that would be just a yes-or-no question. What happened instead, and this is why that paper has been influential, was that when we looked at the analytical results in these fish we didn’t see just deca; we also saw lower brominated PBDEs. We initially thought that could have been from contaminants in decaBDE. The fish food could have been contaminated originally. But when we looked at the peaks from the analysis, we could see that certain peaks for these lower brominated compounds kept getting bigger even after we stopped feeding. That was evidence that the fish were somehow breaking down the decaBDE to lower brominated PBDEs, and that meant deca was not as stable as the industry was trying to make out. That was a complicated article to write because a lot of other chemists were saying it wasn’t possible—they’d never seen animals debrominate things. Now we, and others as well, have shown that fish, in particular, seem to be very good at debrominating deca.

When I was still with the EPA, it had a program on persistent organic pollutants, and that’s what funded research on brominated compounds. They asked me, because I knew the field, if I could write a review report on that particular part of the program when it ended. I did that in 2000 and used the opportunity to put the Swedish research into perspective.

Shortly thereafter, the annual dioxin conference was held in Monterey, California. I couldn’t attend it, but two of the people who had arranged it asked me if I could possibly take my EPA report and update it and then that could be used as a review in a special issue of Chemosphere on this conference and flame retardants in general. I saw it as a good way to get a publication from the report and so I agreed.

Updating, though, always takes much more time than you might originally think. I also tried to cover everything—the analytical methodology, the toxicology and trends and levels in the environment and in humans. That’s one of the reasons that paper is so highly cited. People can cite it for all three of those areas. I think it was also at the point in time when it was still possible for one review to cite most of the relevant literature without getting unwieldy. Since then, the research in this area has exploded and the number of papers has increased exponentially.

First, the Canadians and a few U.S. scientists started getting interested in PBDEs. They saw the Swedish data, some of which was rather alarming—the study in human breast milk, for example—and that got them motivated. There were these exponentially increasing trends of PBDEs in human breast milk when PCB and dioxin levels were going down.

So the Canadians made research money available and had some government scientists go back to the archives to start analyzing temporal trends in the Great Lakes and in human samples to see if there was a problem. That was a three-year initiative, and they very quickly found that levels were often many times higher than in Europe and they also saw this exponential increase.

The U.S. was very slow in getting started, but some people did—Ron Hites was one. His work sparked other studies and there was this explosion of papers from people who had been looking at dioxin and PCBs and now turned to PBDEs as well. So that’s the first big change. Everyone has been looking for PBDEs everywhere. And all over the world, there are these similar trends, although in Europe they seem to be flattening out.

We’re also seeing much more work now on decabrominated diphenyl ether. Deca has been difficult to analyze, mainly because a lot of laboratories are contaminated with this compound. Another recent change is that now everyone is starting to include a range of brominated flame retardants in their studies, not just PBDEs anymore. There’s going to be an alphabet soup of compounds coming out in publications in the future.

For lower brominated diphenyl ethers, everything is pretty clear now. And the data for the penta- and octaBDE products became strong enough that the European Union banned both as of 2004. Canada is now considering the same action, as are several states in the U.S.

I think people will accumulate more data on deca, because deca is still produced and marketed. Deca was always the biggest of these products. There’s about 50,000 tons a year produced in the world, compared to 5,000 a year for penta when it was at its peak. Another major area of research will be hot spots. There has been a lot of research on general geographical trends. We’re now beginning to see studies of hotspots of human exposure. Some have to do with recycling old computers and old electronic equipment, and whether or not this is done in a proper manner. There have been discussions about the way this is being handled by dumping old electronic equipment in South East Asia and in China, and that’s exposing these groups of people who are doing the work: who are uneducated and don’t realize the risks of exposure to these compounds.

Well, the hardest part is the analysis. This is not a problem with the lower-brominated compounds. But for deca, there’s a lot of contamination. We’ve been fortunate enough to work in a newly renovated building, which meant we could control all the materials being used in the construction. So we’ve had very low blank levels—no contamination problems at all. But a lot of other labs have a lot of problems analyzing for these compounds, because they couldn’t control for the contamination in their laboratories.

Good standards have also been a problem. You need standards because when you analyze a sample and get out these peaks, you have to be able to compare it to something you know is that substance. If the peaks match the peaks of known substances, then you can identify it. If you don’t have these standards, when you get the peaks, you don’t know what they mean. Is it a PBDE with seven bromines, for instance? And which one? That situation is now improving. There are more and more standards nowadays and it helps us identify things that we couldn’t do before.

That the amount of knowledge we have about PBDEs, even including this deca compound, is really much more than what we had when we banned PCBs. Despite that fact, it’s now much more difficult these days to get something off the market that could potentially be an environmental problem before that problem actually arises.

Well, industry is much better at lobbying; they have more money, are much more powerful and so can stop things or slow them down. The reason deca isn’t off the market is also a safety issue. The industry uses it in plastics to keep things from burning. It’s both good and bad. So instead of discussing what alternatives there could be for fire safety, we end up discussing the risks and benefits of deca, in terms of how many lives it saves because of fires verses the long-term environmental damage.

The other problem is that we’ve all gotten used to this problem. I think when PCBs showed up accumulating in the environment, it was such a shock. It’s not supposed to be there. It was relatively easy to get a ban. Now there are so many chemicals and things in the environment people have just gotten used to it.

Cynthia de Wit, Ph.D.
Stockholm University
Stockholm, Sweden