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September 02, 2003
Synchrotron Science Helps Identify Mercury in Fish
FOR IMMEDIATE RELEASE - September 2, 2003 2003-09-03-OTHER
Synchrotron Science Helps Identify Mercury in Fish
Though studies from around the world have shown that mercury from fish can
sicken or even kill people, new synchrotron-based research involving
University of Saskatchewan scientists raises the possibility that the
mercury compounds that build up in fish may not be so bad after all.
That's because the mercury that collects in fish may be in a form that is
less harmful than the form that had previously been thought to build up in
fish tissue. However, the researchers caution that many questions need to be
answered before the implications for people who eat fish are clear.
The research was led by biophysicist Graham George who recently relocated to
the U of S from the Stanford Synchrotron Radiation Laboratory. The paper
appeared in the August 29th issue of the journal Science published by the
American Association for the Advancement of Science (AAAS).
Other members of the team were environmental scientist Ingrid Pickering, who
also recently joined the U of S from Stanford, and Australian chemist Hugh
Harris. U of S developmental biologist Pat Krone and former graduate student
Scott Blechinger were also collaborators on aspects of the work.
The exact chemical identity of the mercury in fish is important because
different methylmercury compounds have quite different toxicities. It has
been known for many years that the mercury in fish is a
methylmercury-containing species -- but exactly which methylmercury species
has remained a mystery. The safe limits for human consumption of fish have
been to some extent based on studies using methylmercury chloride as a
model.
The researchers studied swordfish and orange roughy bought at a local
seafood store. With conventional chemical analysis, fish tissues always need
to be chemically pulled apart before an analysis can be done, which partly
destroys the molecules. But with the synchrotron, the intact sample can be
measured and no chemical pre-treatment is required, which allows the
molecules to be observed directly.
The researchers collected information on the atoms bound to mercury in the
fish muscle tissue.
They found that the methylmercury in both fish is bound to a sulfur atom,
and is most likely methylmercury cysteine. The cysteine form of
methylmercury was found to be less toxic to day-old zebrafish larvae.
"There's reason for cautious optimism that mercury in fish may not be as
much of a concern as we thought," said George.
The next step is to determine the form of mercury that accumulates in
mammals that eat mercury-laden fish. "Once we understand how mercury is
bound in mammalian tissues, we'll be ideally poised to design a drug that
could perhaps remove it," he said.
George and Pickering were recruited to the U of S geological sciences
department as Canada Research Chairs. They will use the Canadian Light
Source (www.lightsource.ca), which opens next spring, in their research.
George stresses the synchrotron provides a tremendous advantage for
molecular toxicology sleuthing over conventional imaging techniques. "Now we
can take intact tissue samples and study compounds at the very low
concentrations commonly found in biological systems," he said.
Mercury can accumulate in the tissues of fish from industrial pollutants and
mercury-tainted trash that wind up in rivers and oceans. It has been linked
to neurological damage and increased risk of heart attacks.
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For more information, contact:
Graham George
Geological Sciences
University of Saskatchewan
(306) 966-5722
Kathryn Warden
Research Communications
University of Saskatchewan
(306) 966-2506
kathryn.warden@usask.ca
(Posted September 02, 2003)