Introduction

The purpose of this paper is to observe the relationship between mercury and its relationship with people. Mercury (Hg) is a naturally occurring heavy metal that is a dangerous neurotoxin, and has been recognized as a global pollutant. Like Carbon, it has its own cycle, which means it has impact and influence in every environment and disperses all over the globe, of which is heavily influenced by human activities. The focus of this paper is on the presence of Mercury in the ocean and other bodies of water. Mercury has both chemical and physical forms in seawater, including dissolved species of divalent mercury, dissolved gaseous mercury, and particulate mercury species. The focus of the paper is on the main component of dissolved gaseous mercury, Methylmercury (MeHg).

Methylmercury (MeHg) is an organic form of Hg, formed from the methylation of inorganic Hg, which increases bioaccumulation potential and has one of, if not the, highest toxicity rates. Some percentage goes into water, others get absorbed by the food web. The exact percentage is unknown. It is also the most poisonous chemical form of Hg, which gives it a high affinity for the sulfhydryl ligands in amino acids. MeHg varies seasonally, and increases with temperature, nanoplankton amount, and in coastal areas, increases with primary production, biological turnover, and metabolic activities of phytoplankton and pelagic bacteria. Thus, the production of methylmercury is correlated with the organic processes and organic matter, such as the decomposition of organic matter, and primary producers. It also increases with depth and salinity in the open ocean water column, where it is most prevalent, and increases with sediment deposition in coastal areas.

 

Mercury Source

Mercury in the ocean, and in turn methylmercury, has a variety of sources. The greatest source is from wet and dry deposition from the atmosphere. Re-emissions also occur, or rather, the ocean reabsorbs some of what it released into the atmosphere. MeHg is also produced and affected by anthropogenic and natural sources. Anthropogenic productions and effectors include: industrial waste management activities, fossil-fuel power plant use, production and manufacturing of metals and chemicals, gold and Hg mining, urbanization, logging, and most importantly, oil and other drilling in the ocean, and sediment runoff in coastal regions. Natural producers and effectors include: volcanic and geothermal activities, invasive species, re-emission, and results from climate change such as water temperature, oxygen level, and sulfate input. Anthropogenic sources have the greatest influence on methylmercury production.

The Problem

Mercury (Hg) levels have increased. Although mercury levels may have naturally been elevated in the environment, anthropogenic activities since industrialization has increased it worldwide. Rise in mercury could be due to recently increasing atmospheric mercury emissions from East and South Asia offsetting reductions in North America, global climate change, and food web alterations due to invasive species. As a result, methylmercury concentrations in animals have increased greatly. Methylmercury is not only harmful to wildlife, but also to humans. It’s affinity for sulfhydryl ligands in amino acids induces alterations in protein structures that leads to a loss of function.

Fish are known to absorb levels of MeHg, the process of which being through bioaccumulation, and/or trophic transfer. How much methylmercury a fish contains is dependent on a variety of variable, including age, size, metabolic rate, how fast it grew, community, feeding habits, and food-chain length. The trend is that the higher position a fish has in the trophic level, the more amount of MeHg it contains.

Methylmercury causes a variety of health problems to occur, many of which are still unstudied.  In fish it has been known to reduce growth, disrupt reproduction, and cause lives to be lost. To further the cause of disrupting reproduction, at least in freshwater fish, it is also an endocrine disrupter and can damage gonads and alter production of sex hormones in freshwater fish. Aside from being a neurotoxin, not much is known of the affects of mercury in fish, and thusly, predators that eat the fish, including humans.

Pregnant women, other women of child-bearing age, and infants are known to be particularly vulnerable to effects from consuming MeHg-contaminated fish. In children, prolonged or increased exposure to MeHg during gestation may result in neurobehavioral disorders. In adults, one result of increased mercury levels is Alzheimer’s Disease- a progressive disease that results in memory loss and other cognitive function. A recent analysis of studies has shown that there are elevated blood mercury levels in patients with Alzheimer’s disease, and there appears to be a link between mercury and the features that cause Alzheimer’s (Pigatto, 2018). Other toxic effects of mercury to humans are other damages to the neurological, immune, genetic, enzyme, cardiovascular, respiratory, and gastrointestinal systems.

If mercury levels continue to rise, more wildlife and humans will suffer from health issues, many of which are unconfirmed.

 

 

Resolutions

To begin, mercury is hard to decrease and monitor due to having so many variable sources, and in additionally, in the ocean, with the varying rates of accumulation and dilation. Commonplace now, at least in North America, are fish advisories which catalogue different fish and their mercury levels, telling people which are safe to eat.

International efforts are also taking place to lower the dangers of mercury. In 2013, a global treaty to prevent emissions was signed at the Minamata Convention of Mercury, after much effort from the united Nations Environment Programme (UNEP) that had been working on the issue since 2003. Unfortunately, these methods will only prevent the addition of mercury, and the levels are predicted to simply remain the same as present day for decades. A full recovery could take centuries to occur, due to watershed responses being slow and sediments storing historic mercury. Additional/specific measures that can be taken are converting to use green energy, as Ontario, Canada has done with the implementation of the Green Energy act in 2009, and the elimination of coal as a source of electricity in 2014.

Conclusion

Mercury is cycled throughout all of earth’s environments and is intricately linked to humans. The levels of mercury, especially methylmercury, has risen greatly since industrialization and continues to rise, much of which is due to anthropogenic influences. It causes health problems to many humans and other wildlife, and if levels continue to rise, more health risks will occur.  Not much research has been done on not only its full effects on health, but its presence in the environment and how to rectify it, as there are so many variables influencing it. One way to begin solving the issue is to research and use renewable sources of energy.

 

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