Posted on 08/10/2005 5:26:23 AM PDT by dennisw
Let’s start with a straightforward fact:
Mercury is unimaginably toxic and dangerous.
A single drop on a human hand can be irreversibly fatal.
A single drop in a large lake can make all
the fish in it unsafe to eat.
Often referred to as quicksilver, mercury is the only common metal that is liquid at room temperature. Alchemists, including the young Sir Isaac Newton, believed it was the source of gold. In the modern era, it became a common ingredient of paints, diuretics, pesticides, batteries, fluorescent lightbulbs, skin creams, antifungal agents, vaccines for children, and of course, thermometers. There is probably some in your mouth right now: So-called silver dental fillings are half mercury.
Mercury is also a by-product of many industrial processes. In the United States coal-fired power plants alone pump about 50 tons of it into the air each year. That mercury rains out of the sky into oceans, lakes, rivers, and streams, where it becomes concentrated in the flesh of fish, shellfish, seals, and whales. Last year the Food and Drug Administration determined there is so much mercury in the sea that women of childbearing age should severely limit their consumption of larger ocean fish. The warning comes too late for many mothers. A nationwide survey by the Centers for Disease Control shows that one in 12 women of childbearing age already have unsafe blood levels of mercury and that as many as 600,000 babies in the United States could be at risk. But that begs a critical question: At risk for what?
_________________________________________
TUNA TYPES
One particularly common source of low-level mercury exposure is tuna. Because they are large, long-lived predators, tuna accumulate more mercury in their tissue than smaller, short-lived fish. When tested for mercury in parts per million, flesh from albacore tuna, which take five years to mature, was shown to contain about four times as much mercury as chunk light tuna, which is harvested from younger fish. ______________________________________________
Infants born to mothers contaminated by mercury in Japan’s Minamata Bay in 1956 had profound neurological disabilities including deafness, blindness, mental retardation, and cerebral palsy. In adults, mercury poisoning can cause numbness, stumbling, dementia, and death. “It’s no secret that mercury exposure is highly toxic,” says toxicologist Alan Stern, a contributor to a 2000 National Research Council report on mercury toxicity. But high-level exposures like those at Minamata cannot help scientists determine whether six silver fillings and a weekly tuna-salad sandwich will poison you or an unborn child. “The question is, what are the effects at low levels of exposure?” he says.
Data now suggest effects might occur at levels lower than anyone suspected. Some studies show that children who were exposed to tiny amounts of mercury in utero have slower reflexes, language deficits, and shortened attention spans. In adults, recent studies show a possible link between heart disease and mercury ingested from eating fish. Other groups claim mercury exposure is responsible for Parkinson’s disease, multiple sclerosis, Alzheimer’s, and the escalating rate of autism.
How—and in what form—mercury inflicts damage is still unclear. Yet scientists and policymakers agree that more regulation is imperative. The Environmental Protection Agency plans to finalize its controversial first rule on reducing mercury emissions from power plants this month, and delegates from the United Nations Environment Programme met in late February to discuss an international convention limiting mercury use and emissions.
A decade ago researchers and lawmakers agreed that lead, another heavy metal, was harmful to children at levels one-sixth as high as previously recognized. But it took scientists decades to establish the scope and subtlety of lead poisoning. Mercury is now a ubiquitous contaminant. The average American may have several micrograms of it in each liter of blood, and the atmospheric burden of mercury has perhaps tripled since the industrial age. Whatever needs to be done to protect humanity from its love affair with quicksilver, it had better happen soon.
In August 1996 Karen Wetterhahn, a chemistry professor at Dartmouth College in Hanover, New Hampshire, spilled a few drops of a laboratory compound called dimethyl mercury onto one of her hands. She was wearing latex lab gloves, so she didn’t think much of it. A colleague saw her at a conference the following November. “She said she thought she was coming down with the flu,” says toxicologist Vas Aposhian of the University of Arizona. By the time Wetterhahn was diagnosed with mercury poisoning, in January, it was too late. Despite subsequent treatment that helped clear the metal from her body, she lapsed into a vegetative state in February and died the following June.
Scientists are at a loss to explain why mercury often takes months to exert its effects. “If we knew that, we’d know a lot more about how mercury poisons the brain,” says Tom Clarkson, a toxicologist at the University of Rochester Medical Center.
The degree of mercury’s toxicity depends on the form and route of exposure. You can swallow the liquid form of elemental mercury without much fear because it doesn’t easily penetrate the lining of the stomach and intestines. On the other hand, liquid mercury vaporizes at room temperature, and when you inhale the vapor it moves right from the lungs to the bloodstream to the brain. A broken thermometer can release enough mercury vapor to poison the air in a room—one reason why some cities and several states discourage the sale of mercury fever thermometers.
Mercury also binds with other elements in salts and organic compounds of varying toxicity. Dimethyl mercury, the substance that poisoned the Dartmouth chemist, is a synthetic form of organic mercury rarely found outside a lab. A simpler organic compound called methylmercury is of greater concern because methyl- mercury is the form found in the flesh of fish.
Seafood is one of the two most common sources of mercury exposure in adults. Although concentrations of mercury in air and water are increasing, they are still too small for alarm. But bacteria process the mercury in lakes and oceans into a form that accumulates in living tissue. Plankton take in the bacteria and are in turn eaten by small fish. With each meal, the mercury concentration rises. Then larger fish eat the small fish, increasing tissue concentrations still more. Fish at the top of the food chain accumulate the most mercury. The species singled out by the recent FDA advisory—big predators such as albacore tuna, shark, and swordfish—can have 100 times more mercury in their tissues than smaller fish do.
The methylmercury in fish passes readily from the human gut to the bloodstream and on into all organs and tissues. It seems to act most powerfully on the brain because the compound is strongly attracted to fatty molecules called lipids, and the brain has the highest lipid content of any organ. Methylmercury crosses the protective blood-brain barrier by binding with an essential amino acid that has dedicated carrier proteins for shunting it into brain cells. Once inside brain cells, some of it gets converted to an inorganic form that sticks to and disables many structural proteins and enzymes essential to cell function. “It can destroy the biological function of any protein it binds to,” says Boyd Haley, a biochemist at the University of Kentucky.
Researchers learned how much mercury the body can tolerate from studies of victims of catastrophic poisoning, such as the Japanese sickened by eating fish from Minamata Bay and the Iraqis who ate grain treated with a methylmercury-based preservative in the early 1970s. But those studies do not reveal how little mercury it takes to cause harm. At the time of her diagnosis, the Dartmouth chemist had 4,000 micrograms of mercury per liter in her blood. A diet consistently high in fish can create a blood-mercury level of about 25 micrograms per liter. That’s far below a lethal dose, but it still may not be safe.
On one of our local hunting and fishing shows here in Michigan often higlights a charter boat captain who has been part of a study for more than twenty years. This guy eats fish from Lake Michigan nearly every day and the mercury levels in his blood are no higher than the control group.
Are you sure :-)
There's a big difference between mercury and dimethyl mercury. It's kind of like the difference between sodium and sodium chloride. Put each of them in your mouth and you get much different results. Or hydrogen and hydrogen fluoride. When I was little, we used to play with mercury all the time. We could put blobs of it in our hands and roll it around. We would rub it onto new pennies to make them shiny silver. Another reporter who doesn't understand the difference between an element and a compound or who is going for the hot opening paragraphs. Later in the story she reports that you can swallow mercury metal without much fear.
Thanks much for the letters that oppose this article. I never got to read them
I did the same thing. I think the effects are that you get old and tired. I know I have had these symptoms.
Every cloud has a silver lining that contains abnormally high traces of mercury, which will eventually lead to the onset of neurological disorders.
Somebody has said of the boldest figure in rhetoric, the hyperbole, that it lies without deceiving.
Right. The liquid metal mercury doesn't not react with the human body and poison it just like that. But the dimethyl mercury can be a quick poisoner. That's the real bogyman.
LOL. I guess back in the day all the working class filth had mercury.
That's very misleading. Thermometers, of course, contain mercury, but vaccines don't.
"A single drop on a human hand can be irreversibly fatal."
"Bull... I use to play with it all the time when I was a kid, never even got sick let alone died...obviously..."
That was elemental mercury that you were playing with. The kind that gets in through your skin is dimethyl mercury (it's the kind that killed the chemist in the article after she spilled it on her hand).
There's two different things at work here, so let's review ;)
Elemental (metallic) mercury of the kind found in thermometers is mainly a danger from vapor inhalation - it doesn't penetrate the skin, so holding it in your hand is not dangerous by itself. It's readily absorbed by inhalation, but fortunately most of it gets trapped in your blood cells, and so doesn't reach the brain. Some does reach the brain, however, and long term exposure or exposure to high concentrations of elemental mercury vapor can result in brain damage - this is the source of the "mad hatter's" madness, BTW.
The other form, the much more dangerous form of mercury is organometallic mercury compounds, such as methyl mercury or dimethyl mercury. These compounds are readily absorbed through the skin and not readily excreted, so they accumulate in the body, particularly the brain in humans, over time. Other than the (usually fatal) move of dipping your hand in a jar of the stuff, what usually happens is that organic mercury is absorbed through the skin of fish and accumulates in the fish over time. Then a person eats the fish and in turn absorbs the organic mercury through the digestive tract. Rinse, lather, and repeat, and over time you can have enough organic mercury accumulate to start causing problems. Sometimes it doesn't take much time at all, such as in the case of fetal brain development, which is why pregnant women are usually advised to limit their fish eating these days.
Well, for those people who it was fatal - they aren't here to tell you otherwise.
In the article:
Dimethyl mercury, the substance that poisoned the Dartmouth chemist, is a synthetic form of organic mercury rarely found outside a lab. A simpler organic compound called methylmercury is of greater concern because methylmercury is the form found in the flesh of fish.
Elemental mercury is not very toxic. The organic compounds of mercury are all toxic to varying degrees. The type of mercury found in fish, (mono) methyl mercury, is not the most poisonous, but it is the one that most people will have in their bodies. It is therefore probably important to know how the levels within one order of magnitude of the "normal" blood levels can affect people's nervous systems.
http://www.jtbaker.com/msds/englishhtml/M1599.htm << MSDS info
All the kids had it. None of us died (quickly) from it. But who knows what the long term effects have been.
---
However, this might explain liberals.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.