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Mercury Poisoning: How Best to Deal with a Toxic Element
Mercury is a toxic element found naturally in the world and is usually released through the burning of coal in factories. As a waste product, it can contaminate waterways and the land near the industries that produce it. Once mercury enters waterways, the fish population becomes tainted and when humans consume a large amount of tainted fish, they could be poisoned from their exposure to mercury. The effects of mercury poisoning can range from the “mad hatter” symptoms that hat makers suffered from in the late 1800s because of their exposure to mercury in the hat making factories. The symptoms ranged from sweating and twitching to the most extreme of mental retardation in babies.
 The new University Center being constructed at Wesleyan will not be LEED certified, despite the conservation measures included in the project
Thus, genetically modifying transgenic plants to help clean up mercury from contaminated soils sounds like a beneficial idea. However, although this new phytoremediation technique seems like a useful idea, researchers have yet to grasp that it does not actually make much sense.
The Environmental Protection Agency certainly has faith in this new method of genetic modification in phytoremediation. In 2004, the EPA gave the city of Danbury, Connecticut $55,000 to plant cottonwood trees with the MerA gene inserted in them to remove mercury from the contaminated soils of Barnum Court. This area was the site of a hat-making factory and the amount of mercury in the soil ranges up to the very dangerous level of 300 parts per million (ppm) in the soil. The cottonwood trees were planted because they have an extensive root system to reach more of the contaminated soil. Thus, the idea is that roots would take up the ionic mercury from the soil and then the leaves would transpire minimal amounts of elemental mercury back into the air.
However, initial evidence suggests that there is significant mercury transpiration from the leaves. Research findings on the Barnum Court plants in Danbury, CT conducted by Dr. Johan Varekamp and myself show that the leaves of the transgenic cottonwood trees have lower mercury concentration than the bark and stems.
Although the researchers believe that elemental mercury is less dangerous when large amounts of it are emitted in the air, it will eventually be deposited back to land because it will accumulate in the rivers where it will then be converted into organic mercury by microbes. Organic mercury is the most toxic type that builds up in fish that people will consume. In addition, it is clear that the consumption of tainted fish is a major factor leading to mercury poisoning in humans today. Furthermore, scientists do not know the effects of these genetically modified trees, thus insects and birds may also be affected.
The effects of phytoremediation also cannot be seen after planting the genetically modified plants. After conducting general calculations, Dr. Varekamp has shown that it would take approximately 100,000 years just to clean up Barnum Court, which is less than an acre in area, using the transgenic cottonwood trees. If Danbury had extracted mercury using excavation techniques, it would have only taken a couple of years.
However, the idea of phytoremediation is not without benefits. Excavation and removal of mercury from Barnum Court alone would have cost Danbury about $543,0000. Also, phytoremediation is much easier than extracting the mercury and then carting it to special landfills around the United States because of the dangers associated with spilling of the toxic poison. What the EPA needs to understand, however, is that the transpiration of elemental mercury is not the best way to remove mercury. They need to explore other options like the research being done at Rice University using phytochelatins (heavy metal-binding proteins) that break apart the lead from the soil and draw it up into the plants’ vacuoles for storage. Storing away toxins is a much better method because it is then contained and cannot escape into the air. Thus, the contained plants can then be specially disposed of in hazardous sites.
Using transgenic trees that release elemental mercury back into the air is not an effective method of removing mercury because transpiration into the air will spread mercury into a much larger area and harm more people. Mercury is a dangerous substance afflicting people around the world. The best way to reduce mercury’s impact on the environment is a topic that needs more financing and research.
Asia Neupane, a sophomore at Wesleyan University, works under Dr. Johan Varekamp in an Earth & Environmental Sciences lab in the Exley Science Center. She has been researching mercury for the past year and has recently been researching the effects of phytoremediation (specifically with the plants from Danbury, CT). Her initial findings mentioned in this article were presented in a poster for the Wesleyan Hughes Summer Program in August 2006. This poster can be found in the Exley basement near the Biology labs. Asia can be contacted at PNeupane@Wesleyan.edu.
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