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ESI Special
Topics: September 2007
Citing URL: http://esi-topics.com/pbde/interviews/AkeBergman.html |
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An INTERVIEW with Dr. Åke Bergman |
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 ccording
to our Special Topics analysis on PBDE research over the
past decade, Dr. Åke Bergman's work ranks at the top, with
49 papers cited a total of 1,622 times. In
Essential
Science IndicatorsSM, Dr.
Bergman's work can be found in the fields of Environment &
Ecology and Pharmacology & Toxicology, and includes 210
papers cited a total of 3,889 times to date. Dr. Bergman is
the Chair of the Department of Environmental Chemistry at
Stockholm University in Sweden. In the interview below, he
talks with correspondent Gary Taubes about his highly cited
PBDE research. |
 When
did you first start working on PBDEs?
I have a fairly long history in environmental research, studying
organic environmental contaminants, going back to my doctoral work
in the second part of the 1970s. Accordingly it was natural to come
across PBDEs after their discovery in Swedish wildlife in 1981. In
1989, the Swedish Chemical Agency hosted a meeting on brominated
flame retardants, and I knew when we first discussed it, that we
needed to do chemical synthesis to get reference compounds. It’s
almost impossible to do anything unless you have a pure standard to
work with, and that goes both for the analytical and toxicological
work. It was obvious that pure standards were required for the
PBDEs, just as it had been for the PCBs and PCB metabolites that I
had worked with up till then.
How
did you approach the problem after that 1989 meeting?
At the end of the meeting, it was really up to me as a scientist
to decide if this was something I wanted to do. There was no grant
money available at that time but some pressure from colleagues that
I should give it a try. I was able to receive some financial
support, so we slowly started to dig into the chemical synthesis of
individual compounds. Theoretically, PBDEs can consist of up to 209
different chemical compounds but the knowledge on commercial mixture
compositions of PBDEs was rudimentary. We knew the structure of one
of the PBDE compounds; that was it.
So we started doing chemical synthesis and we have continued to
do so up till today. It has been a matter of finding the best
methodology for synthesis of pure PBDE compounds, to refine or come
up with new ideas how to prepare them. When we had a reasonable
number of pure standards available they could then be used as
analytical standards. One of our papers that is still highly cited
reports the outcome of this work. It was, for example, possible to
assess PBDEs in milk from nursing women in Stockholm (Meironyte D,
et al., "Analysis of polybrominated diphenyl ethers in
Swedish human milk. A time-related trend study, 1972-1997," J.
Toxicol. Env. Health A 58:329-41, 1999). The result of that
study showing increasing levels of PBDEs with time, redoubling every
fifth year, was presented at the annual Dioxin conference in 1998.
The
mothers’ milk study is your second most-cited paper. What made so
influential?
The report was shocking, instead of declining concentrations of
environmental contaminants like DDTs, PCBs and other POPs, the PBDEs
were indeed showing the reverse temporal trend in the mothers’ milk.
This was really new to everyone—to scientists, authorities, and the
public. The data showed, independent of what we all thought at the
time, that the society had a fair control over persistent
contaminants. Indeed, our data was confirmed in other studies in
wildlife and other environmental matrices.
Your
most-cited paper is the 2000 Toxicological Sciences paper,
"Potent competitive interactions of some brominated flame retardants and
related compounds with human transthyretin in vitro," (Meerts IATM,
et al. 56[1]: 95-104, July 2000). What was that about and why do you
think it’s been cited so frequently?
That paper was the natural next step in this process: after some
initial analytical work was done, we want to know what the effects
are. It was obvious from the structures of PBDEs that they do indeed
have a structural resemblance to thyroxin, the thyroid hormone.
Meerts, the first author, was a doctoral student at Wageningen
University (The Netherlands), and we supplied her with the necessary
chemicals in order to test endocrine effects of PBDEs. This paper
reports on the metabolism of PBDEs to hydroxylated PBDEs, and on
competition studies between thyroxin on one side and PBDE congeners,
PBDEs after microsomal transformations and a few synthetic
hydroxylated PBDEs (OH-PBDEs) on the other, for the transport
protein transthyretin.
So
why do you think it’s been cited so often?
I don’t know for sure, but it was indeed the first study to
report on strong binding potencies to transthyretin. The paper is
dealing PBDEs and their potential for inducing endocrine effects and
that is a hot topic. The paper was among the first to address
toxicological effects of PBDEs and this is always a key issue in
research on environmental contaminants.
You
have remained in the forefront of PBDE research for over a decade, but
you seem to collaborate widely. How important are these collaborations
to doing what you do?
This has never been work to be done all by myself. I may have
been a researcher that fused the escalation of the research interest
in PBDEs, but much of the success is through collaborations. I have
been fortunate to have strong and good collaborators in Sweden,
Europe, North America, and Japan covering a variety of scientific
areas. This is not the least important in the area of toxicokinetics,
making metabolism research a key in what I have been involved in.
Through collaborations in an interdisciplinary way, it has been
possible to achieve data on PBDE half-lives and lot of exposure
assessments in people around the world. Frighteningly high
concentrations of PBDEs have been observed not only in U.S. adults
but also in children in the U.S. and in Nicaragua. This is of
particular concern to me.
What
have you learned about PBDEs in the last decade of research and how has
that affected how your own research has evolved?
Since 1998, there’s been an exponential increase in research
worldwide on PBDEs, both regarding effects and exposure assessments
and in wildlife and humans. What I have actually done recently is
taken the step to the next phase, and now I’m much more interested
in PBDE metabolites—in hydroxylated PBDEs that we have actually
found in humans. We also have linked these metabolites to naturally
produced compounds that are very, very similar to hydroxylated PBDE
metabolites. So I’m leaving the PBDE exposure assessments. I think
that work is basically finished. Now I’m trying to continue and move
on to new areas. At least, I am striving to be ahead of the front in
BFR research.
What
has proven to be the biggest obstacle to successful research on PBDEs?
The chemical synthesis—to get the pure compounds we need for
analytical assessment was a major obstacle. We had to invest a lot
of energy to do the chemical synthesis, to find the right
methodology for PBDE congener synthesis in the past; nowadays we are
looking into synthesis of PBDE metabolites. What the commercial
companies offering analytical standards are now using is our
methodology to produce these PBDE compounds. That is a satisfying
achievement, I think.
Of course, I would still like to see more research on the effects
side. Although this is a typical picture in this kind of work. The
chemical area, the exposure assessments, comes first and dominates
the scientific publications, then comes the research on
toxicological effects. I would like to see more structured work on
testing individual PBDE compounds (as chemicals in general). We need
better interdisciplinary cooperation to achieve more. And, of
course, money is the real big obstacle. In the U.S., there has been
extremely little money allocated for PBDE research. In Europe it’s
been better. But you can’t achieve very much without money.
If
you were in charge of funding in this research, how would you allocate
it?
I would definitely want to set up a program to look much more at
the unknowns. I would actually allocate less money to PBDEs because
we have a pretty good idea what’s going on there; there has been so
much research for a long time. Instead, I’d like to look at the
other compounds, particularly focusing on those compounds that are
now replacing PBDEs in flame retardants. Some of these alternative
flame retardants are brominated, and that’s what we need to focus
on. Look at these compounds that we know very little about—maybe
synthesize them and make it possible to go back and do toxicological
assessments.
Åke Bergman, Ph.D.
Department of Environmental Chemistry
Stockholm University
Stockholm, Sweden
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Dr. Åke Bergman's
most-cited paper with 194 cites to date: |
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Brouwer A, et al., "Interactions of
persistent environmental organohalogens with the
thyroid hormone system: mechanisms and possible
consequences for animal and human health,"
Toxicol. Ind. Health 14(1-2): 59-84, Jan-Apr
1998.
Three of
Dr. Bergman's papers
are also represented in the
Research Front map.
Source:
Essential Science Indicators. |
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Related
Links: |
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Dr. Åke Bergman
is featured in
ISIHighlyCited.com |
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ESI Special
Topics: September 2007
Citing URL: http://esi-topics.com/pbde/interviews/AkeBergman.html
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