The recent Food and Drug Administration ruling that mercury used in dental amalgam fillings is not at a level high enough to cause harm in patients was a long-awaited next volley in what is an ongoing discussion about the safety of mercury. The agency did, however, reclassify it from a class I to a class II device. By placing it in this category (moderate risk), the FDA will be able to impose special controls for its use, and warnings are now placed on the packaging.
While the FDA reviewed over 200 studies and their ruling is reassuring, the person contemplating dental work might be interested in some background information on mercury and some questions to ask the dentist.
Mercury is now known to be a neurotoxin but for more than 100 years, it has been an ingredient in dental fillings (the ones that look silver) because mercury helps bind together the other powdered metals that make up a filling. Mercury amalgams are popular because they are inexpensive, durable, and easy to work with, though based on the increasing information about its health effects, dentists are being warned to be sure to have adequate ventilation when working with it.
The discussion about the safety of filling teeth with a mercury-containing substance first began in 1843 when the American Society of Dental Surgeons required members to sign a pledge that they wouldn't use it. But the fact that mercury has been an ingredient in many types of medications probably worked against the dental surgeons' original intentions. Abraham Lincoln and Andrew Jackson both used mercury as part of their medical regimen, and early in the twentieth century, it was given to children as a dewormer; it was also sometimes used in infants' teething powders. Mercurochrome and merthiolate -- that red stuff mothers dabbed on cuts -- were extremely popular up until relatively recently.
Mercury's frequent presence in medications does not necessarily mean it was deemed safe. The substance has been in use for so long that it was "grandfathered" in until the FDA had time to review it. Mercurochrome first came under FDA scrutiny in 1982, but not until 1998 did the FDA pronounce that it was "not generally recognized as safe and effective" as an over-the-counter antiseptic and prohibited its sale across state lines (though it can still be found for sale).
While not everyone has a toxic reaction to mercury, mercury can lead to neurological problems and may contribute to illnesses such as multiple sclerosis if the exposure is high enough and a person is susceptible. Women are more prone to mercury poisoning than men, and children are at the highest risk because their neurological systems are still developing.
So what level of danger do silver fillings present? The 2009 FDA ruling indicates that having a tooth filled with the amalgam is perfectly safe. However, consumers should know that dentists today can offer options. Only about one-third of all fillings that are done each year now use the mercury-based amalgams. Ceramic and polymer compounds have been created that are tooth-color so they look better in spots where a filling is visible. They are more expensive, not as durable, and a little more challenging for the dentist to put in properly, but the composite substances have definite advantages by not containing mercury.
There is some feeling that small amounts of mercury may be released as constant pressure from chewing, grinding or clenching can cause dental fillings to wear away. The lifetime of most fillings is limited -- generally they last 20-30 years. The removal of an amalgam filling needs to be done by a dentist who understands the importance of minimizing a patient's exposure to mercury.
If you currently have amalgam fillings and are experiencing no health problems, it is preferable to avoid disrupting the filling. If you suspect the amalgams are causing health problems and decide to have them removed, talk to your dentist about the process to be used.
Ironically, in 1988 scrap dental amalgam -- fillings that have been removed from the mouth--was declared a hazardous waste product. California legislators have considered legislation to ban the use of mercury amalgams within the state but it has not passed.
But even if we keep mercury out of our mouths, we still have a good deal of exposure to it. Most of our mercury exposure comes from power plant emissions. The Bush administration loosened regulations on the industry, but the Environmental Protection Agency is tightening up again. From the airborne particles emitted from the power plants, mercury becomes part of our food chain by entering the water and the soil, and people are exposed via the fish they consume. The higher the fish on the food chain, the more mercury in the fish. The EPA offers guidelines on fish consumption to consumers. See the information on the government website for details: http://www.epa.gov/waterscience/fish/advice/index.html
Only by reducing plant emissions worldwide will we be able to bring down human exposure to mercury.
Next week, we'll take a look at the problem of mercury in fluorescent light bulbs.