News Release Communique
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 issue 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.
For more information, contact:
Graham George
U of S Geological Sciences
(306) 966-5722
Kathryn Warden
U of S Research Communications
(306) 966-2506
kathryn.warden@usask.ca
Last modified: 2012-01-19 17:01:54