President Obama’s “war on coal” claims to be a “war on mercury.” While the Environmental Protection Agency’s (EPA’s) proposed “Mercury and Air Toxics Standards” (MATS) rule is supposed to reduce exposure to “mercury” emissions, this is just a pretext; the real intent is to control “carbon” emissions, or carbon dioxide (CO2) emissions, to be more precise.
Mercury or CO2?
EPA uses “mercury emissions” as a convenient mechanism to regulate and discourage the use of coal for electricity generation and heating. However, EPA’s real intent is to reduce emissions of carbon dioxide (CO2) emissions that President Obama frequently terms “carbon pollution.”
The mercury rule is nothing but a red herring to control fossil fuel-derived energy production which is claimed to contribute to “climate change.” To use a crass analogy, it is akin to doing away with all civilian airplanes just because on 9/11 airplanes were used as weapons. Several trade unions recently called the proposed MATS rule “
nothing less than industrial sabotage by regulatory means.”
While mercury (in whichever form) is only a minor by-product of burning coal, it is claimed to be the intended target of the proposed MATS rule. Therefore, it ought to be reasonable to look at the various forms and uses of the mercury, their chemistry, effects and quantities. Let’s begin with the element itself.
Use of Mercury
Elemental mercury is known to most people in the form of a silver-like shiny liquid. Elemental mercury is best known from such devices as thermometers like the kind used by your mom to measure your body temperature when you were a child and had a fever, or in motion-activated light switches under the hood of your old Chevy, or even some other electrical switches commonly found in households. For many decades, such uses were common throughout the western world. In fact, the humidity control device in my house contains a small glass vial with liquid mercury inside. It changes position with the humidity in the air to allow either a connection or break of the electrical circuit between the poles.
Because of its high density of 13.5 (relative to that of water, i.e. 1.0), liquid mercury can support all kinds of things close to its surface. There are practical uses for that property as in light houses. Widely used in former times and still found in some locations, their structures supporting the Fresnel lenses are floating on a bath of liquid mercury. The reason is twofold: there is hardly any friction to slowly turning the lens system for creating blinking lights and, more importantly the lens system is always perfectly parallel to the earth’s surface. The latter is critical to the distance from which the light can be seen to guide ships through treacherous waters.
In chemical laboratories around the world, elemental mercury is quite common. There are various applications of its unusual physical properties; from one-way valves to vacuum pumps. As a chemistry student, I worked with such things for years. With proper handling none of us experienced any problem using mercury.
Apart from applications that make use of elemental mercury’s physical properties like its high density and electrical conductivity, there are other common uses of mercury of which you may not be aware. Amalgam is one of those and more likely than not you have some of that in your mouth.
Amalgam
Indeed, you may have a significant amount of mercury in your body. I am not talking trace amounts here, but real quantities, say a volume like that of your mom’s sewing thimble filled with the element. Most of that mercury is found in your teeth, put there (after some drilling) by your friendly dentist. Of course, he or she didn’t put liquid mercury into your extended cavities but a mixture of mercury and another element such as silver powder. When well mixed, the liquid elemental mercury and the silver powder rapidly combine to a rock hard solid, generally known as an amalgam.
Silver-mercury amalgam is most suitable for filling dental cavities as it can be formed to any shape but will harden within a few minutes. It is also extremely durable, resisting any dissolution by saliva and can last for a lifetime. However, I do not dispute that some other amalgams, for example those made with lesser metals such as zinc, are less stable and should not have been used for dentistry.
Silver amalgam is still widely used by dentists around the world when it comes to filling cavities in teeth with a material that is easily applied, hardens rapidly, is strong and lasts a life time. Though quite obvious from its silver-like appearance, its properties for dental fillings are unsurpassed.
The ease with which mercury forms an amalgam with gold is also widely exploited by small claim gold miners around the world. Small claim panning for gold is a major use of mercury. In order to extract and consolidate the gold flakes and nuggets, miners in Brazil and elsewhere use elemental mercury to capture the gold flakes in water running over liquid mercury beds. The gold binds with the mercury and the solid gold-amalgam can be sieved off. The mercury is then easily recycled by heating the amalgam in an iron pot with the resulting mercury vapour forced through a water bath where it liquefies again. The gold remains as a solid lump in the crucible.
Mercury compounds are also common preservatives in various medicinal products such as vaccine solutions that require stability and shelf life before application.
The Mercury and Air Toxics Standards (MATS) Rule
In order to understand how the new MATS rule stacks up against reality, some simple calculations are useful. The most basic ones would give estimates of mercury emissions from the “villain du jeur” (coal) and other sources. Let’s do some math:
Mercury from Coal
The U.S. consumes close to 1,000 million tonnes of coal a year, or 10^12 kg. That coal contains close to 0.1 ppm (parts per million) of mercury. Hence, on combustion, of all that coal and without any cleansing of the flue gases, a total of 100 tonnes or 100,000 kg mercury would be coming out of all chimneys in one year. As the density of mercury is quite high (approximately 13 times that of water), roughly, that amount of mercury would fit into a volume occupied by a table that comfortably seats eight persons..
Mercury from Teeth
As mentioned, for the last one hundred years or so, silver amalgam has been the material of choice to fill dental cavities. I recently visited my favourite dentist and asked him about the amount of amalgam in my mouth. He assured me that it was quite comparable to his other patients of equal age. When I asked about the combined volume of all of such fillings, he guessed about one milli-liter or the volume of half a sewing thimble. That would represent about 10 grams, or 0.01 kg of mercury as amalgam.
Now, let’s multiply that by the population in North America, say 400 million, and you arrive at an amount of 4,000,000 kg of mercury in the entire population’s teeth. As you can see, that number is approximately 40 times that of the annual release of mercury from the burning of coal, 100,000 kg/per year. Wikipedia states the total amount of anthropogenic (manmade) emissions of “mercury” in the U.S as
144,000 kg/year.
At a death rate of approximately 8% of the population and with an estimated one third of the population being cremated, the amount of mercury so released then also comes to 0.1 million kg (elemental) mercury; the same quantity as calculated for the mercury from coal. Indeed, EPA concluded that only one half of the mercury emissions comes from coal.
Mercury from other Sources
Most difficult to estimate is the amount of mercury released from sources other than the two mentioned above. While the element (in any form) is relatively rare with its abundance in the earth’s crust estimated at
0.067 ppm, slightly higher than that of gold, it also is found in any rock and soil in nature; mercury compounds are ubiquitous in nature. Therefore, methyl-mercury and other mercury compounds are also found in aquatic organisms around the world including those far from any human settlement.
In nature, mercury is almost never found as the free element but only in compounds with other elements. Of these, cinnabar, mercury sulfide is by far the most common one. Its bright red color made it a favored
cosmetic for millennia.
Toxicity of Mercury
This brief discourse on mercury would be incomplete without a quick review of mercury’s (in any form) toxicity. However, that is also a major bone of contention.
Elemental mercury, i.e. its vapor is a known neurotoxin. Many of the early investigators of mercury’s effect suffered from its neurological toxic effects before they were recognized. However, it would be wrong to call mercury a villain on that basis only.
Chronic exposure to elemental mercury vapor causes neurotoxic effects like the “mad hatters” disease. However, as with all things toxic, the dose or concentration over time of exposure is most critical. While long-time exposure to elemental mercury vapors causes severe effects, no such effect has been proven to arise from the extremely low levels of mercury and its compounds in the atmosphere that result from the burning of coal. Therefore, the limitations on coal-fired power plants based on their mercury emissions are not scientifically defensible.
Pollution by soluble mercury compounds in lakes, rivers or ocean embayments like at Minamata can lead to increased methyl-mercury levels in local fish above the natural background concentration of approximately 1 ppm. However, the amount of mercury contributed to the atmosphere from burning coal is miniscule relative to its natural background levels in most environs. Even without the use of any coal whatsoever, the concentrations of mercury and its compounds in the environment would not change materially.
Therefore, EPA’s MATS rule is not based on scientific evidence of benefit from the reduction of mercury emissions; it is nothing but a ruse, solely invented to couch the “war on coal” as a “war on mercury.”
