This is a summary of an article written by Stephen M Koral, DMD and
published in Compendium, February,
2013. The article is entitled ‘Mercury
from dental amalgam: exposure and risk assessment’.
Dental amalgam has been used to
restore teeth for nearly 200 years and doubts about putting mercury in the
mouths of human beings have persisted nearly the entire time.
Generally, dentists do not feel
that there is anything scientifically (or medically) wrong with putting mercury
in people’s mouths. Nonetheless, more dentists are using composite fillings
instead of amalgam fillings as they have become easier to use and people are
requesting them given their aesthetic appeal. The reason that dentists don’t
think there is anything scientifically wrong with the mercury in amalgam
fillings is that the sources of information that might implicate mercury as a
toxic substance are largely unavailable to them. The information is not found
in dental journals. Thus, the majority of dentists will tell you that the mercury
found in amalgam fillings is safe.
It is now an indisputable fact
that dental amalgam releases metallic mercury into its environment (i.e., the
mouth). Mercury is released in its gaseous form from the moment the amalgams
are placed in the mouth until they are either removed or the mercury is
completely and rapidly released into the air after death, during cremation, or
more slowly if the person is buried in the ground.
Numerous studies have shown higher levels of
mercury in the tissues of humans with amalgam fillings compared to those who do
not have amalgam fillings. Greater numbers of fillings are associated with
increased mercury concentration in exhaled air, saliva, blood, feces, urine, and
various tissues including the liver, kidney, pituitary gland, and brain as well
as, amniotic fluid, umbilical cord blood, placenta, fetal tissues, colostrum,
and breastmilk.
Evidence of exposure through amalgam fillings is
important, but perhaps the amount of exposure to mercury released in the mouth
is not enough to be dangerous. That is the question. A Risk Assessment is an
important tool for making that determination. A Risk Assessment is a set of
formal procedures that use data from the scientific literature to propose
levels of exposure that may be acceptable under given circumstances. Several
agencies are responsible for regulating human exposure to toxic substances.
These include the FDA (Food and Drug Administration), the EPA (Environmental
Protection Agency), and OSHA (Occupational Safety and Health Administration).
They all rely on risk assessment procedures to set acceptable limits for
chemicals including mercury, in fish and other foods, drinking water and air.
They set enforceable limits or at the very least, guidelines, on human
exposures termed regulatory exposure
limits (RELs). This allowable level must be one at which there is an
expectation of no negative health outcomes.
The mercury released from amalgam
fillings is emitted in the form of a gas and is odorless, tasteless and
invisible. It is inhaled into the lungs and absorbed at a rate of 80%. Mercury
from amalgam fillings also comes from that which is dissolved in saliva,
particles that break off, corrosion products that are swallowed, or
methylmercury that is produced from metallic mercury by intestinal bacteria (author’s comment: bacteria in the
mouth can also convert metallic mercury to methylmercury which is considered the
most toxic form of mercury). Other identified pathways include absorption
of mercury into the brain through the olfactory epithelium (nose) and also
transported directly from the jawbone into the brain. However, most of the
research has been done on the gas form as the other mechanisms are poorly
understood or are considered less important.
There are several issues that
must be considered when establishing a mercury REL. One particularly difficult
issue is that mercury’s effects cannot be accounted for by dose response
models. In other words, the amount of exposure that may cause adverse effects
in one person is not the same amount of exposure that may cause adverse effects
in someone else.
The brain is the most
sensitive target organ for mercury vapor exposure. Therefore, studies that have
been used to calculate the REL are those that have indicated mercury-induced brain
dysfunction. Generally the studies from which RELs were calculated were
conducted in male workers in occupational settings wherein they were exposed to
mercury and thus, they are fraught with limitations. For example, the workers
were only exposed for 8 hours per day compared to 24 hour a day exposure from
amalgam fillings. Further, there are known sex differences between males and
females and the type and severity of adverse effects related to exposure to
poisons. For example, women experience more severe health consequences from
smoking cigarettes than men. Similarly, children and senior adults represent
additional vulnerable groups. comment from the author: mercury from the mother actually accumulates
in the umbilical cord). Nonetheless, these special populations have been
understudied and the available data have been gathered from healthy adult males, 
Other individuals at higher risk for experiencing
harmful effects include people who are medically compromised, people with
genetically determined increased sensitivity to mercury, women of childbearing
age, infants and the developing fetus, to name a few (Comment from the author: Mercury from the mother actually accumulates
in the umbilical cord). Nonetheless, these special populations have been
understudied and the available data have been gathered from healthy adult males,
adding significant bias.
In the U.S. the REL for mercury
vapor that was set in 1995 at .3 micrograms of mercury per cubic meter of air
(.3 ug/m3) is still
the same today. In California, the level is set 10 times more strict at .03 ug/
m3 to account for the lack of studies in pregnant
women and in young children. In Canada, the REL is set at .06 ug/ m3 which is 5
times stricter than the U.S. REL. Notably, more recent studies have found
neurological deficits in mercury exposed individuals that suggest the REL
should be reduced to between .1 and .07 ug/m3 (Lettmeier et al, Sci Total Environ 2010). Although the
EPA acknowledges that new and convincing studies have been published that show
that the REL should be adjusted downward, they have not made the adjustment.
In 1976, Congress mandated the FDA to complete a
classification of dental amalgam. In 2009, under pressure from citizen’s
lawsuits, the FDA finally completed the classification and determined that
amalgam was harmless to everyone over age 6. However, the classification
determination was severely flawed as it ignored the full range of exposures
across individuals and did not control for body weight. In other words, a 40 pound
elementary school-aged child was treated
in the analysis in exactly the same manner as a 175 pound 60
year old man. It also excluded
all children under 6 years of age. These issues were contested forcing the FDA
to convene an expert panel to reconsider the risk assessment. Experts were
gathered to examine data. They took a highly conservative approach and yet
still came up with numbers that significantly exceeded the daily dose of
mercury that is considered acceptable. The number of amalgam surfaces that
would not exceed the U.S. REL was calculated to be six surfaces for toddlers,
children and young teens. For older teens, adults, and seniors it was eight
surfaces. An examination of the entire range of numbers of filled teeth in the
population provided an estimate of 67 million Americans whose amount of mercury
exposure due to amalgam fillings exceeds the U.S. REL.
As of November 2012
the FDA had not announced a response to the petitions to reconsider the
regulatory status of dental amalgam. [Comment
by the author: Sadly, in 2014, the
FDA rebutted the petitions and upheld their amalgam rule stating that amalgam
was safe for everyone.]
Comment by Teri
Franklin, Ph.D.: [So, how much mercury is
too much? How many surfaces in your teeth have amalgam fillings? Each tooth has
5 surfaces, like a box - 4 sides and a top. It is not unusual for an amalgam filling to cover several surfaces
within one tooth. Two surfaces are covered by the amalgam filling in the top
right picture while 3 surfaces are covered by the middle tooth in the bottom
picture. How many days, months, years
have you had amalgam in your mouth? The mercury never stops vaporizing. During
that time some of the mercury is excreted in your urine and feces and some of
the mercury is deposited in your brain, your kidneys, and your liver. To not exceed the daily U.S. REL, toddlers and
teens should have less than 6 surfaces covered with amalgam. For older teens,
adults and seniors the number is 8. Do the math. Of course, this magical
number that you must not pass to be safe assumes that you have not had any
other exposure to mercury, which is highly unlikely. We continue to carelessly
dump mercury into our environment. Further, as described in this summary, the
U.S. REL is most likely far too lenient. We just don’t have all of the
controlled trials in children that will definitively show that any amount of
mercury is or isn’t safe. It isn’t possible or ethical to conduct such studies.
Hundreds of thousands of people are being diagnosed with autoimmune disorders
and illnesses that are destroying their quality of life. They visit their
doctors frequently seeking relief. Doctors do not test for chronic mercury
toxicity. Instead, they prescribe multiple medications that must be taken for
the rest of their life. I was one such patient but I got the mercury out and I
got relief. There is no known medicinal use for mercury and it can do no good
in your mouth. Get it out. Safely. The use of amalgam fillings IS regulated in
E.U. What are we waiting for?]
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