Tuesday, June 01, 2010
Mercury in your Mouth
Mercury has a number of toxic effects and for that reason much work has gone into eliminating mercury from the environment. Although CFC lightbulbs do contain mercury, the government hopes people won't break them, and mercury thermometers have been generally discontinued. The coal industry has spent millions of dollars to combat the problem of mercury emissions, as have other chemical industries. Unfortunately, one place we've forgotten to look is in our own mouths.
Mercury or Amalgam fillings are shiny and metallic and have been used for a least 150 years to fill cavities in human teeth. Currently, their installation and use is not regulated under environmental laws, despite clear research showing that "dental amalgam is the greatest source of mercury vapour in non-industrial settings, exposing the concerned population to mercury levels significantly exceeding those set for food and for air." (WHO)
The problem is not trivial: in the U.S. dental amalgam accounts for about 11 percent of total mercury use, and emits between .6 tons/year and 10 tons/year (more than hazardous waste combusters, cement, etc). (EPA) These emissions are from cremations (~3 tons), water passing through humans (1-10 tons from 300 million americans, each excreting 3-100 micrograms per day) dentist offices (2-25 tons a year from 35-522mg/day/dentist). The totals are less than coal power plants (52 tons/year), but still significant. In Washtington state, King county has mandated the disposal of dental amalgam fillings in a hazardous waste disposal facility and states that "Amalgam particles removed from teeth should be collected, dried, placed in sealed containers, labeled and disposed of only to those qualified waste handlers and waste sites that do not incenerate or burn solid wastes. " Apparently the only place the stuff is safe is in our mouths.
The EPA Reference Dose for safe exposure to mercury is 0.1 micro g/kg/day and the FDA can remove food product from the shelf if it is found to contain more than 1 ppm mercury. Individuals with amalgam fillings ingest 3 to 100 micrograms of mercury per day, easily putting them over both limits. Depending on the number, size, and age of the fillings, the effective dose can be equivalent to eating several cans of tuna a day, each and every day. ( Environmental and Toxicological Concerns of Dental Amalgam and Mercury. Scarmoutzos, Louis and Boyd, Owen. )
In addition, dental amalgam in contact with dissimilar metals may generate galvanic corrosion which would release inorganic mercury (which is water soluble and readily transportable in the environment). Gastrointestinal microorganisms in humans can form methylmercury (the more dangerous form of mercry) from inorganic mercury. Studies have documented that dental amalgam is indeed bioavailable, at least to goldfishes. (Christopher J. Kennedy, “Uptake and accumulation of mercury from dental amalgam in the common goldfish, Carassius auratus,” Environmental Pollution 121, no. 3 (March 2003): 321-326.)
These environmental and personal health issues have convinced me to have my fillings removed and replaced with plastic composite. I would strongly urge anyone else with health concerns about their mercury fillings to also do the research, and then make their own decision. As with many areas of science, the evidence for harm is not complete, and much more research needs to be done. However, I believe that there is sufficient evidence to act.