Mercury is a poisonous neurotoxic heavy metal that has been linked to a host of serious medical conditions in humans and animals. Some forms of mercury such as methylmercury, which is found in some fish, are dangerous to humans.
Exposure to excessive amounts of mercury has been linked to damage to the nervous system; kidney damage (changes in kidney function); damage to developing fetuses; tremors; loss of sensation; irritability; skin rashes; eye irritation; and memory problems.
Some symptoms of an elevated mercury level are hair loss, tiredness, and short-term memory loss. In most cases, the effects of an elevated mercury level are reversible within a few months after the source of the mercury is eliminated.
Low-level exposure to mercury in its various forms and compounds is normal and happens regularly. Experts say that there is no risk associated with exposure that remains within the safety limit of 1 part per million (food and drink).
Mercury poisoning, however, is a more serious situation. It can occur through breathing mercury vapor or handling droplets from a spill. Extreme caution should be used in cleaning up such spills so as to avoid dispersing toxic mercury vapor.
Two studies in the November 2002 issue of the New England Journal of Medicine presented contradictory findings about possible heart-related dangers from eating mercury-laden fish.
Past research, however, has shown that mercury found in fish can have harmful effects on the developing brain of a child or fetus. Thus, pregnant women are strongly cautioned to avoid eating the type of large, deep-sea predatory fish which are most prone to contain high concentrations of mercury. These include swordfish, albacore tuna, shark, and bluefish.
Other recent studies dealt with the long-term effects of mercury exposure on the hearts of middle-aged and elderly men. While one study found that men who had suffered a heart attack had higher levels of mercury, the other found no correlation between mercury level in the body and the risk of developing heart disease.
In April of 2002, researchers at the Glasgow Royal Infirmary in Scotland conducted a study of 180 dentists and concluded that dentists are more likely to suffer memory and kidney problems as a result of long term exposure to the mercury used in tooth fillings.
The test group had up to four times the normal level of mercury in their urine and nail samples. While fillings can emit vapors that are harmful to both dentists and their patients, the dentist is more likely to experience health-related complications such as AlzheimerÃ¢â‚¬â„¢s disease since they are subjected to ongoing exposure to the mercury.
For years, a number of consumer advocates and some dentists have argued that the mercury found in fillings can slowly leach into the body in sufficient quantities to cause autism and other serious neurological problems.
Dental associations, however, have always claimed that the mercury in fillings is safe when it is mixed with other metals. These so-called Ã¢â‚¬Å“amalgamÃ¢â‚¬Â (or Ã¢â‚¬Å“silverÃ¢â‚¬Â) fillings have been in use for over a century.
While the more versatile Ã¢â‚¬Å“compositeÃ¢â‚¬Â fillings made of synthetic resins that can also be matched to the color of the surrounding tooth have become widely used by dentists, amalgams remain an accepted type of filling worldwide.
Although the results of two long-term studies seem to indicate that there is no reason for concern, the findings have not silenced the skeptics, who have already challenged the research as everything from biased and unreliable to unethical experimentation on children.
Both studies, which were government-financed (National Institute of Dental and Craniofacial Research) and are published in The Journal of the American Medical Association (JAMA), claim to show that there is nothing to worry about.
One study conducted in Portugal involved 507 children (ages 8 to 10) who were tested for neurological effects Ã¢â‚¬Å“repeatedlyÃ¢â‚¬Â over a seven-year period.
The other, involving 534 children (ages 6 to 10) in New England (U.S.), examined effects on intelligence, memory and other cognitive functions, and kidney function.
Critics argue that the studies amounted to unethical experimentation on children that was performed without proper disclosure Ã¢â‚¬â€œ a charge that has been strongly denied Ã¢â‚¬â€œ and that the studies were far too limited in scope and size to furnish conclusive proof of anything.
There is also the fact that, because of their small size, neither study examined any possible link between mercury-based fillings and autism, which is one of the most relevant areas of inquiry with respect to mercury exposure in children. Thus, that issue remains completely unaddressed.