Researchers find easier test for mercury

University of Illinois researchers have developed an easier test for toxic mercury in the environment, a problem found in fish caught in some Illinois lakes and streams, among other things.

More than a dozen waterways in the state, although none in East Central Illinois, are under a mercury advisory by the Illinois Department of Public Health.

The advisory suggests that pregnant and nursing women, women of childbearing age and children younger than 15 years old limit consumption of certain fish from the locations because of adverse effects of mercury on developing nervous systems, which could result in lower IQ, abnormal muscle tone and slowed motor function. In the extreme, mercury poisoning also can be deadly.

The suggested limit is generally one meal a month for those "sensitive populations" and once a week for other folks.

At issue, UI Professor Bob Hudson said recently, is a form of mercury called methylmercury, because it mimics a natural amino acid the body needs, especially the bodies of growing children.

"When we eat (contaminated) fish, we absorb almost all that mercury," said Hudson, a UI natural resources and environmental sciences professor and an environmental chemist. "That's why it's so nasty."

Mercury in its basic, inorganic form, while toxic, isn't as readily assimilated in the body or in the food chain.

"Methylmercury is like 90 percent or more efficient at transferring up the food chain," said Hudson, who studies the effects of toxic metals in the environment.

Some mercury exists in the environment naturally, but most of it is put there by man-made means, coal-fired power plants, waste incinerators and industrial operations such as metal smelting, for example.

The mercury goes up into the atmosphere and comes down in the rain and other precipitation. When it lands in an anaerobic location – one with depleted oxygen levels where bacteria can work on it, a wetland or the sediments of a lake bed, for instance – it is converted to organic methylmercury. From there it gets into plants, zooplankton, fish, wildlife, and us.

"It's a natural process that occurs in very specific areas," said Hudson, whose lab, in part, works to understand how methylmercury is formed and moves in the environment.

Scientists test for methylmercury now using gas chromatography, a method of separating and identifying chemicals in a sample carried along by a gas pumped through the detection apparatus.

Preparation of the samples is laborious and prone to flaws that require starting the testing procedure all over again, said Hudson and Brian Vermillion and Wade Wimer, graduate students who work in Hudson's lab.

"The analysis of methylmercury is really expensive," Hudson said. "Typically, it's like $200 or more a sample."

Hudson, who needs to do a lot of such testing in his research, couldn't afford it at that price, which also limits the number and scope of environmental studies involving mercury in general. So he and Chris Shade, a former UI doctoral student, began working on an alternative.

They developed a process, which is being patented, starting with easier-to-produce liquid samples that separates methylmercury by taking advantage of the difference in its electrical charge.

The process, which Shade is commercializing, can test a sample about every seven minutes, Vermillion said. It can detect methylmercury at levels below one part per trillion, roughly equivalent to a drop of ink in an Olympic-sized swimming pool.

"We can simplify the preparation of the sample and you can automate getting the sample into the system," Hudson said. They're working on automating the process now.

The goal is to make the tests less expensive and more common, both for their own research and for environmental monitoring purposes. That might allow full-blown surveys of lakes and rivers for methylmercury to provide a better idea of where contamination is a problem and how to remediate it.

The method was outlined in the October issue of Environmental Science & Technology. The Illinois-Indiana Sea Grant program, the Council on Food and Agricultural Research and the UI College of Agricultural, Consumer and Environmental Sciences funded the research.

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