Mercury: The Good, the Bad, and the Ugly, Part 3
According to www.epa.gov, in 2000, the EPA Administrator found that regulation of hazardous air pollutants, including mercury, from coal and oil-fired power plants was appropriate and necessary.
In 1999, EPA estimated that approximately 75 tons of mercury were found in the coal delivered to power plants each year and about two thirds of this mercury was emitted to the air, resulting in about 50 tons being emitted annually.
This seems to be an outrageously large amount of elemental mercury. This is mercury emitted in the United States...imagine the total global mercury pollution.
Natural sources of mercury — such as volcanic eruptions and emissions from the ocean—have been estimated to contribute about a third of current worldwide mercury air emissions, whereas anthropogenic (human-caused) emissions account for the remaining two-thirds. These estimates are highly uncertain. Land, water, and other surfaces can repeatedly re-emit mercury into the atmosphere after its initial release into the environment. Much of the mercury circulating through today's environment is mercury that was released years ago.
Recent estimates, which are highly uncertain, of annual total global mercury emissions from all sources, natural and anthropogenic, are about 4,400 to 7,500 metric tons emitted per year.
The U.S. is the third largest emitter of anthropogenic mercury, although its emissions, estimated to account for roughly three percent of the global total, are far lower than emissions from China, the largest source globally.
A power plant will emit 10mg of mercury to produce the electricity to run an incandescent bulb compared to only 2.4mg of mercury to run a CFL for the same time.
If a typical low-mercury CFL light bulb has about 5mg of mercury, adding 2.4mg additional mercury as a byproduct of generating the electricity required to energize the light bulb is still environmentally better than producing 10mg of mercury to energize an ordinary incandescent bulb.
Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others. The levels of methylmercury in fish and shellfish depend on what they eat, how long they live and how high they are in the food chain.
Research shows that most people's fish consumption does not cause a health concern. However, it has been demonstrated that high levels of methylmercury in the bloodstream of unborn babies and young children may harm the developing nervous system, making the child less able to think and learn.
At high levels of exposure, methylmercury's harmful effects on these animals include death, reduced reproduction, slower growth and development, and abnormal behavior.
This methylmercury is bad stuff: highly toxic, accumulating in water plants and animals, causing tragic disease and disorder.
Methylmercury [CH3Hg] is the most toxic form of mercury pollution. It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight. Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults. Exposure to methylmercury is usually by ingestion, and it is absorbed more readily and excreted more slowly than other forms of mercury.
People are exposed to methylmercury almost entirely by eating contaminated fish and wildlife that are at the top of aquatic foodchains. The National Research Council, in its 2000 report on the toxicological effects of methylmercury, pointed out that the population at highest risk is the offspring of women who consume large amounts of fish and seafood. The report went on to estimate that more than 60,000 children are born each year at risk for adverse neurodevelopmental effects due to in utero exposure to methylmercury. In its 1997 Mercury Study Report to Congress, the U.S. Environmental Protection Agency concluded that mercury also may pose a risk to some adults and wildlife populations that consume large amounts of fish that is contaminated by mercury.
How can I avoid consuming mercury in fish?
Fish are important in a healthy diet. They are a lean, low-calorie source of protein. However, some fish may contain methylmercury or other harmful chemicals at sufficiently high levels to be a concern. Federal, state and local governments issue fish consumption advisories when the fish are unsafe to eat.
Options for avoiding the mercury in mercury-contaminated fish are more limited than for fish contaminated with PCBs, dioxins and other organic contaminants. Younger fish tend to have lower concentrations of mercury than older, larger fish within the same waterbody. Mercury concentrates in the muscle tissue of fish. So, unlike PCBs, dioxins and other organic contaminants that concentrate in the skin and fat, mercury cannot be filleted or cooked out of consumable game fish.
Alkali and metal processing, incineration of coal, and medical and other waste, and mining of gold and mercury contribute greatly to mercury concentrations in some areas, but atmospheric deposition is the dominant source of mercury over most of the landscape. Once in the atmosphere, mercury is widely disseminated and can circulate for years, accounting for its wide-spread distribution.
Once in surface water, mercury enters a complex cycle in which one form can be converted to another. Mercury attached to particles can settle onto the sediments where it can diffuse into the water column, be resuspended, be buried by other sediments, or be methylated. Methylmercury can enter the food chain, or it can be released back to the atmosphere by volatilization.
Mercury and methylmercury exposure to sunlight (specifically ultra-violet light) has an overall detoxifying effect. Sunlight can break down methylmercury to Hg(II) or Hg(0), which can leave the aquatic environment and reenter the atmosphere as a gas.
Bacteria that process sulfate (SO4=) in the environment take up mercury in its inorganic form and convert it to methylmercury through metabolic processes.
These methylmercury-containing bacteria may be consumed by the next higher level in the food chain, or the bacteria may excrete the methylmercury to the water where it can quickly adsorb to plankton, which are also consumed by the next level in the food chain. Because animals accumulate methylmercury faster than they eliminate it, animals consume higher concentrations of mercury at each successive level of the food chain. Small environmental concentrations of methy-lmercury can thus readily accumulate to potentially harmful concentrations in fish, fish-eating wildlife and people. Even at very low atmospheric deposition rates in locations remote from point sources, mercury biomagnification can result in toxic effects in consumers at the top of these aquatic food chains.
The mercury that occurs naturally, plus that which has already been released and converted to methylmercury, is quite enough to be considered a cause of the world's declining health and weakening immune systems. We must halt use of coal. I'd rather deal with radioactive waste than mercury. Nuclear energy generation produces concentrated, controlled, and contained waste that can be encased in glass and buried without any possibility of leaching or contamination.
Interestingly, the only coal-fired electrical generating plant in Oregon (my home state) is the Boardman Power Plant, about 30 miles from where I live.
The plant releases about 35 pounds of mercury for every 100 megawatts of electricity generated. In 2007 the plant generated 585 megawatts of electricity, totaling over 200 pounds of mercury.
Portland General Electric (PGE) posted a report on January 8, 2010 that described their goal of reducing those emissions to just five pounds of mercury per 100 megawatts, or about 30 pounds per year. The cost of the retrofits would be about $560 million.
Shortly thereafter, PGE announced that installing fewer emmission controls and closing the plant in 2020 would make better sense financially. The original end of life date for the plant was 2040.
Other options are still being explored and discussed, including development of alternate fuel sources such as algae.
The best answer in my opinion? Nuclear energy plants.
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