Thursday, August 30, 2012


Published in the Williamson County Sun 8-26-12

Mercury from a broken thermometer was so much fun to play with.  I would put it on a saucer and break it into tiny beads with a toothpick, and then watch the beads pop back together into a big, shimmery ball.  Genie Vogler told me she would squish a dime into the mercury to make the dime real shiny.  What our mothers didn’t know when they gave us mercury as a toy was that those bits of quicksilver were vaporizing into toxic gases, inhaled into our curious little brains.  We all survived those multiple small exposures, and even went to college, but sometimes when I watch CSPAN I wonder if there could have been a lingering effect on our generation.


Remember Alice in Wonderland and the Mad Hatter?  In 1865, when Lewis Carroll wrote the novel, mercuric nitrate was used to make felt hats.  Hatters were chronically exposed to mercury vapors and suffered tremors, hallucinations, and erratic behavior.  Carroll grew up near the center of England’s hat industry, so he would have been acquainted with the condition.  The center of America’s hat making industry was Danbury, Connecticut, where factories dumped waste mercury into the Still River.  Although the use of mercury for making felt was banned in 1941, the river sediment is contaminated with mercury to this day.


Mercury has no essential role in animal physiology, but it has become a ubiquitous pollutant.  Every year, fifty tons of mercury is released into American air as the result of burning coal for electricity.  You guessed it:  Texas is Numero Uno, with more than twice the emissions of the distant number 2, Ohio.  The problem with all that mercury in the air is that it settles into our lakes and oceans where bacteria convert it into methylmercury, a neurotoxin that accumulates in the muscle tissue of fish.  The higher the fish is on the food chain, the more mercury it accumulates, so the big carnivorous fish like tuna and shark have the most mercury.  Eating large doses of methylmercury can cause permanent brain damage, especially in a fetus or young child.  This fact creates a dilemma for me.  In my freezer is a big filet of king mackerel, caught recently by my son-in-law at Port Aransas.  It is super-delicious, which I know because I ate the other half of that fish before realizing that king mackerel is on the Food and Drug Administration’s “Do Not Eat” list for pregnant women and young children.  I’m not pregnant, of course, but knowing about the mercury in that fish sucks the joy right out of eating it.


Mercury can also bypass the air and enter directly into our water supply.  Dentists’ offices that place or remove amalgam fillings (the silver ones which are 43% mercury) flush 3.7 tons of mercury a year into municipal wastewater systems, according to an estimate by the EPA.  Ninety percent of that mercury will settle out with the biosolids and can re-enter the environment if the biosolids are incinerated or applied to land as fertilizer.  The other ten percent remains in the treated water and returns to our lakes and streams.  The quantity in the water is too little to hurt you if you drink it, but it can be converted to methylmercury and concentrated in fish.  Mercury never goes away.  It just moves around.


Although in most states it is still perfectly legal for dentists to flush waste amalgam down the drain, the American Dental Association recommends that it be carefully captured and recycled.  Dr. David Hennington was kind enough to show me his amalgam separator, a special filter that removes amalgam fragments from his surgical wastewater.  Dr. Hennington prefers to fill cavities with the new tooth-colored composite resins and doesn’t use amalgam for filling teeth anymore, but often he has to remove an old silver filling that has failed.


Interestingly, another way that dental amalgams contribute to mercury pollution is by cremations.  When a body with amalgam fillings is cremated, the high temperatures vaporize the mercury.  The EPA estimates that every year several tons of mercury go up in smoke from cremated teeth.


There is a lot of controversy about possible health effects of having amalgam fillings in your mouth.  It is well known that there are mercury emissions even from cured amalgam fillings, but the amount is so small that it is difficult to prove any detriment to health.  The argument will rage on, but neither Dr. Hennington nor the American Dental Association recommends removing amalgam fillings that are functioning well.  If a dentist advises you to remove all your old amalgam fillings to avoid mercury toxicity, put your hand over your wallet and get a second opinion.  Dr. Hennington belongs to the Eco-Dentistry Association, and not even they recommend removing intact amalgam fillings.  They do, however, recommend that you save water by turning off the tap while you brush your teeth.

Dr. David Hennington and his amalgam separator

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