Mercury Fillings: They're Not Risky
Mercury Vapors Not Easily Absorbed by Body
WebMD News Archive
Dec. 9, 2004 -- Mercury in dental fillings does not cause Alzheimer's disease, multiple sclerosis, or other health problems, according to a new review of all current research.
But will this put to rest the concerns many people have?
It's a sensitive issue. Methyl mercury is the type found in fish, and has been found harmful to the brain in large amounts. The EPA advises women to avoid eating mercury-rich fish during pregnancy for that reason.
However, mercury in dental fillings is a different type of chemical compound -- an amalgam or blend of copper, silver, and mercury. Dentists have used this blended metal for more than 150 years. But over the years, concerns about mercury fillings have been raised, writes Meryl Karol, PhD, an epidemiologist with the University of Pittsburgh School of Public Health.
Karol chaired the expert panel whose research review was released today. Scientists from the National Institutes of Health's National Institute of Dental and Craniofacial Research, the Center for Devices and Radiological Health of the FDA, the CDC, and the Public Health Service's chief dental officer, were among those experts.
Only 300 studies published since 1996 had sufficient merit to be included in their report -- studies that analyzed mercury in urine samples as a marker for mercury exposure. Methyl mercury from fish is not found in urine samples, explains Karol.
Large population studies, animal toxicity studies, and studies of effects from various levels of mercury exposure were included. Researchers also looked at whether it was biologically possible for mercury vapor from fillings to cause brain disorders and other health problems, she notes.
The panel's conclusion: "Current research is insufficient to attribute various complaints to mercury in dental amalgam," writes Karol. Even those people with allergic reaction to dental amalgam "did not have high levels in their blood," she adds.
Also among the panel's conclusions:
- The evidence showed that mercury vapor is released from dental work and absorbed in the body. However, about 95% of people in the studies had mercury levels at or lower than the level deemed harmful by the WHO. The long-term use of nicotine chewing gum (over two years) combined with intense chewing and more than 20 dental amalgam surfaces presents the greatest chance that urine mercury measurements exceed the general population and approach a level seen in people who have occupational exposure to mercury. However, the reports state that adverse health effects for long-term nicotine gum chewers was not evaluated.
Bruxism (grinding teeth) and dental amalgam placement and removal appear to have less impact on exposure than the use of nicotine chewing gum.
- Allergic sensitivity to dental amalgam seems to affect a small percentage of people.
- Insufficient research has been done to support or refute whether dental amalgam causes antibiotic resistance in the human gut or that it may cause any autoimmune disease including multiple sclerosis.
- Three studies also failed to support a role of dental amalgam as a factor in the development of Parkinson's disease or Alzheimer's disease.
- Human studies have failed to support or refute a link between dental amalgam with brain damage in a developing fetus.
- Both methyl mercury from fish and mercury from dental amalgam have been found in breast milk. Rat studies show that high exposure of mercury vapor among pregnant rats and monkeys induces behavioral abnormalities -- but no studies have looked at whether low-level exposures affect brain development.
Although some people undergo chelation therapy to treat their symptoms, animal studies have shown that chelation therapy works to bind and remove mercury from the kidneys, but not from the brain, Karol notes. However, chelation carries a host of problems -- possible adverse health problems including headaches, dizziness, nausea, and the loss of essential metals.
Chemicals used in chelation therapy have been harmful to the developing fetus, she adds.