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FILE - In this July 27, 2018, file photo, the Dave Johnson coal-fired power plant is silhouetted against the morning sun in Glenrock, Wyoming. The Trump administration targeted an Obama-era regulation credited with helping dramatically reduce toxic mercury pollution from coal-fired power plants, saying the benefits to human health and the environment may not be worth the cost of the regulation. The 2011 Obama administration rule, called the Mercury and Air Toxics Standards, led to what electric utilities say was an $18 billion clean-up of mercury and other toxins from the smokestacks of coal-fired power plants. (AP Photo/J. David Ake, File)

On Dec. 28, the Environmental Protection Agency announced its intent to cancel regulations that govern the release into the air of mercury and other pollutants from coal-fired power plants. Citizens have 60 days to comment on the proposed, needless rollback.

Termed the Mercury and Air Toxic Standards, the Obama administration contended that the regulations would reduce diseases related to mercury and other pollutants emitted from smokestacks. Most power plants have complied, spending billions of dollars to remove those toxins. Some plants were shuttered. Mercury emissions have decreased an estimated 85 percent as a result of those actions.

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Dr. Clif Cleaveland

EPA, now directed by Acting Administrator Andrew Wheeler, contends that the cost of complying with the regulations is excessive for uncertain health benefits. Wheeler worked as a lobbyist for the coal industry before his Senate confirmation in April 2018 to serve as deputy to Administrator Scott Pruitt, who resigned in July 2018.

Coal-fired power plants have been the main source of mercury pollution in the U.S. and the world. Gold mining, some metal-smelting operations and chemical plants that manufacture chlorine release lesser amounts of mercury. Volcanic eruptions and natural erosion of rocky surfaces account for a small percent of mercury release. Forest fires also release mercury into the air.

When released in smoke, mercury may travel hundreds of miles before settling over land, fresh water and oceans. Once deposited, micro-organisms slowly convert elemental mercury to highly soluble, organic methyl mercury (MM). Both mercury and MM may accumulate in the sediment of rivers and lakes. Disruption of that sediment by flooding or dredging can release significant amounts of the toxins.

Mercury accumulates in aquatic life by a process of "bio-magnification." Minute organisms take in MM. Progressively larger fish eat the smaller creatures. Large, older fish and sharks accumulate MM to the extent that their meat contain extremely high concentrations compared to surrounding fresh or oceanic water.

MM is readily absorbed from the human (and animal) digestive tract and is dispersed throughout the organs of the body, including the central nervous system. MM crosses the placenta to enter the fetus and its nervous system, and therein lies a major problem. The rapidly developing fetal brain as well as the brains of infants and children are especially vulnerable to MM's toxic effects. MM is also carried in the milk of nursing mothers.

MM toxicity leads to slowed thinking, impaired coordination, and difficulty paying attention. Those changes may not show up for months.

The highest concentrations of MM occur in shark, swordfish, big-eye or ahi tuna, king and Spanish mackerel, tile fish from the Gulf of Mexico, and orange roughy. Women who are pregnant and nursing mothers should avoid those fish. Because MM lingers in the body for months, women who are planning a pregnancy should avoid those species as well.

Localized mercury and HH pollution prompt advisories by states to avoid either certain species or all fish from specific lakes and streams. The 2018 Tennessee Fishing Guide includes a listing that is updated annually. The sad conclusion from that data is that many Tennessee waters contain harmful levels of MM and other toxins. Determining which fishing sites to avoid is complex. Unstated are the sources of the polluting mercury.

Another problem is the uncertain origin and feeding practices for imported farmed-fish. Who monitors international fish farms for MM pollution? Is the food fed to those fish free of mercury and MM?

Against this background of uncertainty, I believe it wise for pregnant and nursing mothers as well as very young children to avoid or to strictly limit seafood intake. The species mentioned above should not be eaten.

Until mercury emissions are permanently limited by coal-fired power plants around the world, mercury and MM pollution of aquatic life will be a continuing problem. Mercury and MM that is already in the aquatic food chain will persist for many years.

This is no time to relax U.S. restrictions on mercury emissions. Since most power plants are in compliance, what is the point unless EPA plans to argue that health considerations should not be factored into environmental regulations.

Contact Clif Cleaveland, a retired physician, at ccleaveland@timesfreepress.com.

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