Student unlocks secrets of mercury

Oct 13, 2011 By Stephen Prestley
Tracy MacDonald’s work with zebrafish reveals that some forms of mercury are safer than others. Photo: Scott Bell for the U of S.

More than one billion people around the world depend upon fish for protein in their diet. But the threat of mercury poisoning, especially in children, has raised concerns about the safety of eating fish.

University of Saskatchewan student Tracy MacDonald is part of a research group that has tested different chemical forms of on , a common fish in labs and home aquariums, to see how mercury accumulates in a developing organism. The results show that not all chemical forms are equally harmful.

The organic chemical form is most responsible for mercury poisoning because it targets the brain and central nervous system. Mercury is converted into the organic form by and, in turn, is eaten by fish. Higher up the , the toxic organic form becomes increasingly concentrated, so that large like or swordfish usually contain more mercury.

In contrast, the inorganic form found in the air, water and is much less toxic. It results from natural releases such as and industrial releases such as .

“We’re able to prove that chemical form is important and that researchers shouldn’t just be looking at one form of it,” says MacDonald, a native of Nelson, B.C. “You really need to look at which chemical form will be really toxic.”

The team includes her supervisors Graham George, a synchrotron scientist, and Pat Krone, a zebrafish expert, as well as research associate Goshia Korbas.

The research is funded by the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada.

Zebrafish were selected because they are a “vertebrate model,” meaning that the researchers can infer that what happens to the fish could happen in human fetuses.

“I really like working on something with a human-related aspect and am excited to apply this to my research,” says MacDonald.

The group is using innovative and powerful X-ray fluorescence imaging at the Canadian Light Source synchrotron and the Advanced Photon Source synchrotron in the U.S. to, in effect, take pictures of the fish down to the cellular level.

MacDonald and Korbas have seen that inorganic mercury is less likely than the organic form to cause illness in the fish because it typically accumulates at much lower levels.

In contrast, the fish exposed to organic mercury are much sicker because they have mercury accumulating in important areas such as the brain, eye lens and muscle tissue.

MacDonald has seen how organic mercury can cross through blood barriers in the fish and make them ill. Previous research has shown that similar processes in humans can damage the or, in the case of a pregnant female, damage the developing fetus.

The next step for MacDonald is to discover exactly how mercury damages fish tissues.

Members of the group are designing a compound that would neutralize organic and inorganic mercury in the body with better potency and fewer side effects. The team is currently looking to add a member who would synthesize the drug.

This work is still in the early stages, but when the new drug is ready, MacDonald will help test it out on her zebrafish and perhaps better understand how to prevent mercury’s toxic effects. From this knowledge, human danger from mercury poisoning might even become a thing of the past.

“There are a billion people worldwide who depend on fish as a primary source of protein and, of course, children are at the greatest risk of toxicity,” says MacDonald. “If we could understand mercury better we could say that, in general, it is safe which would be helpful for alleviating the concerns of eating fish for people in developing countries.”

Explore further: US delays decision on Keystone pipeline project

Provided by U of S Research News

5 /5 (3 votes)
add to favorites email to friend print save as pdf

Related Stories

Mercury reduction tied to emissions laws

Apr 03, 2006

Seven years after Massachusetts passed the nation's toughest mercury emission incinerator laws, mercury found in some freshwater fish is down 32 percent.

Study: Mercury can travel long distances

Dec 12, 2005

University of Washington scientists say they may have determined why mercury in the atmosphere might be washed out more easily than earlier believed.

Engineered bacteria mop up mercury spills

Aug 12, 2011

Thousands of tonnes of toxic mercury are released into the environment every year. Much of this collects in sediment where it is converted into toxic methyl mercury, and enters the food chain ending up in the fish we eat. ...

Recommended for you

US delays decision on Keystone pipeline project

43 minutes ago

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

7 hours ago

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

AWT
not rated yet Oct 13, 2011
This is rather common view - for example, whereas dimethylmercury is extremely toxic, however mercury salts inflict little neurological damage without continuous or heavy exposure.

More news stories

Magnitude-7.2 earthquake shakes Mexican capital

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.