Health Risks

Mercury is usually released into the environment by factories as emissions or waste. Eventually this mercury is discharged into the water bodies and then is converted by bacteria living in the sediment into methyl mercury. Methyl mercury can be ingested by smaller aquatic plants and animals. The danger here is that, through biomagnification, animals higher in the food chain will have larger concentrations of methyl mercury in their systems. This is dangerous especially for large fish, birds, and humans. Additionally, through bioaccumulation, small amounts of consumed toxins can build up within one’s system over time, leading to mercury poisoning. The most common form of mercury poisoning comes from methyl mercury. According to the Environmental Protection Agency, almost everyone in the world has trace amounts of methyl mercury in their bodies because of its abundance in our environment, but in larger concentrations, it can be dangerous.

Side Effects of Mercury Poisoning:

For infants and children:

• Impaired neurological development
• Impaired cognitive thinking, memory, attention, and language skills
• Impaired fine motor and spatial visual skills

For adults:

• "Pins and needles” in the hands, feet, and around the mouth
• Impairment of the peripheral vision
• Lack of coordination of movements
• Impairment of speech and hearing
• Muscle weakness

Extreme cases of high mercury poisoning:^[3]

• Kidney and respiratory failure
• Death

Case Study

Onondaga Lake: Commonly known as the “Most Polluted Lake in America”, Onondaga Lake suffers from industrial waste and sewage pollution (i.e. ammonia and phosphorus which cause high algal blooms and suffocation of other organisms in the Lake).

Since the 1800s Allied Chemical, recently succeeded by Honeywell International, is credited for dumping a total of 165,000 lbs of mercury into the lake, resulting in the contamination of about 7 million cubic yards of lake-bottom sediments.^[4] Their continuous polluting only ceased in the last few decades and has fomented tragic damage to the environment.^[4]

Mercury contamination usually is caused by industrial emissions. The mercury enters the environment as an industrial emission and then moves through the water system before entering the lake. Once in the lake, the mercury is transformed by sediment-dwelling bacteria into methyl mercury, which has a high tendency to bioacculumate in aquatic life.^[5] Even now, the State Health Department advises staying clear of eating any fish that come out of the Lake. In addition, through biomagnification, the methyl mercury has made its way up the food chain and has been found in bats and birds surrounding the Onondaga Lake area. Researchers found that the Spotted-Sand piper was the most affected bird.^[6] The levels of mercury found in the animals is so high that only about 20% of all birds’ chicks survive. Furthermore, scientists have reasons to believe that the mercury poisoning will continue to work its way up the food chain unless direct action is taken.

Remediation Efforts: The Upstate Freshwater Institute has been working to prevent the mobilization of methyl mercury from the deep sediments of the Lake. To do so, they have been adding a common agricultural fertilizer, calcium nitrate, solution to the bottom on the lake, which has been successful in lowering the concentration of mercury in fish dramatically.^[7] In addition, Honeywell International has been working since 2012, 24 hours a day, 6 days a week, between April and November on dredging the contaminated mud on the bottom of the lake. Earlier this summer, Honeywell attorneys said that there were 800,000 cubic yards of dredging to complete and they estimated being able to complete this amount by the end of the season in 2014. The cost of such efforts is estimated at $451 million.^[8] The Metropolitan Syracuse Wastewater Treatment Plant, which dumps about 20% of the water that goes into Onondaga Lake, has spent millions of dollars on making sure that there is no further lake pollution. Although major progress has occurred on the mercury levels on Onondaga Lake. It takes millions of dollars of remediation efforts to fix the polluted ecosystem and years for the biomagnification effects to resolve themselves.^[9] has been successful in lowering the concentration of mercury in fish dramatically.^[10]

Current Remediation Techniques

Although the EPA is working with the National Institute of Standards and Technology to reduce mercury use and pollution, there are still a number of already contaminated areas that are being remediated now.^[11]

Nitrate Immobilization: The use of calcium nitrate to prevent methyl mercury from moving throughout bodies of water.^[12]
Dredging: Mercury containing sediments are removed or dug up from the lake bottom.^[12]
ISMS (In Situ Mercury Stabilization): Developed by Brookhaven researchers, the ISMS treats and removes mercury content from the soil, sludge, and other industrial waste; therefore stopping mercury from entering the water source.^[13]
Thermal desorption: This involves heating the contaminated soil to high temperatures so that the mercury will vaporize away and can be separated from the soil.^[13]

merT/merP

The transport system being utilized for this project is a combination of the merT and merP genes from the transposon TN501 of Pseudomonas aeruginosa. The genes merT and merP are part of the mer operon which helps P. aeruginosa resist mercury toxicity.^[14] These two membrane proteins work together to transport Hg²⁺ ions into the cell.^[1] Systems for sequestration of mercury have been successfully developed utilizing merT and merP.^[15,16,17] We hope to improve upon these systems by combining the merT and merP genes with a different regulatory system and by making all these genetic parts modular.

References

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1. United States of America. Environmental Protection Agency. EPA. Environmental Protection Agency, n.d. Web. 23 Sept. 2014.
2. United States of America. Environmental Protection Agency. EPA. Environmental Protection Agency, n.d. Web. 23 Sept. 2014.
3. "Mercury Poisoning: Facts about the Symptoms of This Poison." MedicineNet. N.p., n.d. Web. 24 Sept. 2014. .
4. Moriarty, Rick. "Discovering What Lies at the Bottom of Onondaga Lake." Syracuse.com. Syracuse.com, n.d. Web. 24 Sept. 2014.
5. Mattews, Dave A., David B. Babcock, John G. Nolan, Anthony R. Prestigiacomo, Steven W. Effler, Charles T. Driscoll, Svetoslava G. Todorova, and Kenneth M. Kuhr. "Whole-lake Nitrate Addition for Control of Methylmercury in Mercury-contaminated Onondaga Lake, NY." Elsevier (2013): n. pag. Print.
6. Collin, Glen. "High Levels of Toxic Mercury Found in Onondaga Lake Birds, Bats; Studies Show Web of Contamination." Syracuse.com. N.p., 18 May 2014. Web. 11 Aug. 2014.
7. "Onondaga Lake Nitrate Addition and Monitoring." Recent and Current Water Quality Projects with Examples of Lake, Reservoirs and Tributaries Studied. Upstate Freshwater Institute, n.d. Web. 11 Aug. 2014.
8. Collin, Glen. "Onondaga Lake Dredging Begins for Season; Could End a Year Early (video)." Syracuse.com. N.p., 7 Apr. 2014. Web. 11 Aug. 2014.
9. Collin, Glen. "Homegrown Onondaga Lake Cleanup Project Cuts Mercury Levels by 95 Percent." Syracuse.com. N.p., 13 Oct. 2013. Web. 11 Aug. 2014.
10. "Onondaga Lake Nitrate Addition and Monitoring." Recent and Current Water Quality Projects with Examples of Lake, Reservoirs and Tributaries Studied. Upstate Freshwater Institute, n.d. Web. 11 Aug. 2014.
11. United States of America. Environmental Protection Agency. EPA. Environmental Protection Agency, n.d. Web. 23 Sept. 2014.
12. "Onondaga Lake - The Most Polluted Lake In America." Onondaga Nation. Onondaga Nation People of the Hills, n.d. Web. 11 Aug. 2014.
13. Greenberg, Diane. "And Then There's Mercury Pollution." Innovation: America's Journal of Technology Commercialization 9.6 (2011/2012): n. pag. Innovation America. Web. 24 Sept. 2014.
14. Misra, T. (1984). Mercuric Ion-Resistance Operons of Plasmid R100 and Transposon Tn501: The Beginning of the Operon Including the Regulatory Region and the First Two Structural Genes. Proceedings of the National Academy of Sciences, 5975-5979.
15. Chen, S., & Wilson, D. B. (1997). Genetic engineering of bacteria and their potential for Hg2+ bioremediation. Biodegradation, 8(2), 97–103. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/9342882
16. Chen, S., & Wilson, D. (1997). Construction and characterization of Escherichia coli genetically engineered for bioremediation of Hg(2+)-contaminated environments. Applied and Environmental Microbiology, 63(6), 2442-2445.
17. Chen, S., Kim, E., Shuler, M., & Wilson, D. (1998). Hg²⁺ Removal by Genetically Engineered Escherichia coli in a Hollow Fiber Bioreactor. Biotechnology Progress, 667-671.