How Mercury Becomes Toxic In The Environment

Aug 18, 2009 By Richard Merritt
This is Amrika Deonarine of Duke University. Credit: Duke University Photography

(PhysOrg.com) -- Naturally occurring organic matter in water and sediment appears to play a key role in helping microbes convert tiny particles of mercury in the environment into a form that is dangerous to most living creatures.

This finding is important, say Duke University environmental engineers, because it could change the way in the environment is measured and therefore regulated. This particularly harmful form of the element, known as methylmercury, is a potent toxin for nerve cells. When ingested by organisms, it is not excreted and builds up in tissues or organs.

In a series of laboratory experiments, Amrika Deonarine, a graduate student in civil and environmental engineering at Duke's Pratt School of Engineering, found that organic matter and chemical compounds containing sulfur - known as sulfides -- can readily bind to form mercury sulfide nanoparticles. Since they are more soluble than larger particles, these nanoparticles may be the precursors to a process known as methylation.

"When the organic material combines with the mercury, it prevents the particle from accumulating with other mercury particles and growing larger," said Deonarine, who presented the results of her analysis at the summer annual scientific sessions of the American Chemical Society (ACS) in Washington, D.C.

"Since the mercury remains in a nanoparticle size, it can easily collect on the surface of where any mercury that dissolves can be taken in by the microbes," Deonarine said. "Without the organic matter, the mercury sulfide nanoparticles would grow too large and become insoluble, thus reducing the availability of mercury for microbial methylation."

It is while inside the microbe that the mercury is converted into the harmful methylmercury form, the researchers said.

These reactions can only take place in cold water environments with little to no oxygen, such as the zone of sediment just below the bottom of a body of water. Other such anaerobic environments can also be found in waste water and sewage treatment systems, the researchers said.

"The exposure rate of mercury in the U.S. is quite high," said Heileen Hsu-Kim, Duke assistant professor of civil and environmental engineering and senior member of the research team. "A recent epidemiological survey found that up 8 percent of women had mercury levels higher than national guidelines. Since humans are on top of the food chain, any mercury in our food accumulates in our body."

Because fish and shellfish have a natural tendency to store methylmercury in their organs, they are the leading source of mercury ingestion for humans. Mercury is extremely toxic and can lead to kidney dysfunctions, neurological disorders and even death. In particular, fetuses exposed to methylmercury can suffer from these same disorders as well as impaired learning abilities.

There are many ways mercury gets into the environment, with the primary sources being the combustion of coal, the refining of such metals as gold and other non-ferrous metals, and in the gases released during volcanic eruptions. The air-borne mercury from these sources eventually lands on lakes or ponds and can remain in the water or sediments.

"These initial laboratory findings could have far-reaching implications," Hsu-Kim said. "That these reactions can take places in anaerobic environments suggests that the old paradigm of testing for toxic metals in sediments may provide an incomplete picture of how much methylmercury is there."

The researchers plan to continue their studies with other types of and for longer periods of time.

Source: Duke University (news : web)

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User comments : 8

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E_L_Earnhardt
1 / 5 (2) Aug 18, 2009
Methyl Mercury may be made to "plate out" by
nanoelectric dischrage, (or "spark")! It IS
a "metal molecule"! SOLUTION VITAL!
E_L_Earnhardt
1 / 5 (1) Aug 18, 2009
See "http:www.physorg.com/news 169754920 htm"
Egnite
1 / 5 (1) Aug 19, 2009
How mercury becomes toxic in the human - distribute a "flu vaccine" with it as an ingredient, clever eh?
marjon
not rated yet Aug 19, 2009
Nature, not man, makes Hg more toxic?
Given time, some environmental group will find a way to blame George Bush.
Soylent
1 / 5 (1) Aug 19, 2009
How mercury becomes toxic in the human - distribute a "flu vaccine" with it as an ingredient, clever eh?


No.

Thiomersal is poorly absorbed. You get more mercury from eating a piece of fatty fish than from taking a thiomersal containing vaccine.

If you're worried about thiomersal, use a sealed, single-dose vaccine instead of a multi-dose vial and STFU.

Soylent
not rated yet Aug 19, 2009
Nature, not man, makes Hg more toxic?


Yeah, and?

The source of the mercury is the asinine practice of burning semi-combustible dirt popularly known as coal.
ToddC
5 / 5 (2) Aug 19, 2009
What a bizarre story out of such a prestigious university! All the student managed to do was form ultrafine mercury sulfide particles in the presence of organic matter. Absolutely everything else in this news release is pure speculation - none of the biotransformations discussed in the article have been measured or observed in any experiments by the researchers (nor by anyone else!) It was a good grad. student study, but this article draws a lot of unsupported conclusions from that study.
Egnite
not rated yet Aug 20, 2009
No.

Thiomersal is poorly absorbed. You get more mercury from eating a piece of fatty fish than from taking a thiomersal containing vaccine.

If you're worried about thiomersal, use a sealed, single-dose vaccine instead of a multi-dose vial and STFU.


lol, 1st time I've heard you getting touchy about a subject. Dunno bout your hospitals/nurses but I doubt in the UK we'll get an option of our preferred vial used for the injection. I'd rather not partially absorb any mercury tbh but each to thier own. Can't say I eat much "fatty" fish either, it's normally just the meat from fish I eat and I doubt ingesting trace amounts in your food is anywhere near as dangerous as injecting it straight into your bloodstream.

When it comes to vaccines, there are many more worries than just the mercury. I won't even ingest formaldahyde via aspartame so I'm hardly gonna shoot it up. I'll just leave the testing to sheep like you and run the risk of cathcin oh so scary flu.