Mercury: A Toxicological Review - Essay Example

Mercury: A Toxicological Review The element mercury is one of the transition elements of the periodic table, and is otherwise known as liquid silver or quicksilver. Mercury was known to ancient civilizations and no single individual is credited with having discovered it. Studied first by the alchemists, mercury was first distinguished as an element by the French chemist Antoine Laurent Lavoisier, who burned mercury and other substances in his experiments in attempts to discover the composition of air. The element mercury was in fact named after the planet Mercury. There are various effects that mercury has on the human body, and relationship between it, especially in regards to autism and birth defects, must be carefully and critically addressed. In order to come to a clearer and more knowledgeable understanding on the subject matter of the element mercury, all of the characteristics and factors in relation to it must be thoroughly discussed, as well as other key factors which are relevant to this subject matter. The aim of this paper is to discuss all of this in order for us to gain a more dynamic and intellectual viewpoint on this issue. This is what will be dissertated in the following. The element mercury (Hg) has an atomic number of 80, and an atomic weight of 200.59. Mercury is the only common metal liquid at ordinary temperatures. Mercury was known to the ancient Chinese and Hindus and was in fact found in Egyptian tombs that date from 1500 BC. In the days of ancient China, India and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. "The ancient Greeks used mercury in ointments and the Romans used it in cosmetics." (Wikipedia, 2006). It was only by 500 BC that mercury was used to make amalgams with other metals. A heavy metal, mercury is widely considered one of the most toxic substances on earth. (Clarkson, 1997). The toxic effects of mercury affect the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight. The four primary forms of mercury are as follows: 1. Metallic Hg: The liquid, silvery, heavy globule found in thermometers. Metallic mercury is 13 times denser than water. Though insoluble, metallic mercury can vaporize sufficiently at room temperature to reach toxic levels over time. 2. HgCl2: A white, corrosive, crystalline salt. It is sparingly soluble in water and is used in some pesticides. 3. Organic bivalent mercury compounds: Very volatile and able to be absorbed into the body through all portals (openings) including the skin. These compounds are often times used as fungicides and as preservatives and in manufacturing processes. 4. Methylmercury: Water soluble form of mercury that can pass the brain barrier and cause central nervous system damage. This is the most toxic of all mercury forms and is the result of a conversion of soluble mercury into an insoluble metallic mercury byproduct. Mercury is widely used in laboratory work for making such things as thermometers, barometers, diffusion pumps, along with many other instruments. It is also used in making mercury-vapor lamps and advertising signs, as well as in mercury switches and other electronic apparatus. Various other uses include such things as making pesticides, cercury cells for caustic soda and chlorine production, dental preparations, anti-fouling paint, batteries, and catalysts. Mercury is a virulent poison which is easily and readily absorbed through the respiratory tract, the gastrointestinal tract, or through unbroken skin. This element acts as a cumulative poison and dangerous levels are readily attained in air. "Air saturated with mercury vapor at 20C contains a concentration that exceeds the toxic limit many times." (Los Alamos National Laboratory, 2003). The danger in regards to this element actually increases significantly at higher temperatures, and it is therefore important that mercury be handled with extreme care. The toxicological effects of Mercury and the correlation to birth defects and autism are significant in this issue. Mercury is a poisonous, metallic element which is present throughout the environment. Birth defects can be caused by mercury in numerous ways, one of the most common being due to the fact that mercury is released into the environment by a number of different sources including burning fossil fuels, coal combusting power plants, lead smelters, mining operations and chlorine producers. "Mercury floats in the air as vapor or binds to particles and eventually falls to earth, settling in sediment, oceans and lakes or re-enters the atmosphere by evaporation." (Birth Defect Research for Children, 2001). After the mercury is present in the water, it then accumulates in fish as methyl mercury, which is an organic form of the element that builds up in animal tissue. Unborn babies are most highly at risk to the dangers of consumption of contaminated fish. When pregnant women consume contaminated fish, the mercury passes easily through placental barrier to affect the developing baby. An example of how critical a situation as consuming mercury could be occurred in Minamata, Japan, when "Birth defects, brain damage, weakening of immune systems and many other severe problems were traced to a factory that dumped mercury contaminated waste into the bay at Minamata, Japan." (Traudt, 2005). It is a significantly important fact that if a woman is exposed to high levels of mercury while she is pregnant, both her and her baby's health are threatened. What is less known is that a person can be exposed to mercury in many ways, some of which may not even have been considered viable. A person can be exposed to mercury by breathing in air, eating food or drinking water contaminated with mercury, and can also be exposed to mercury through the skin. Mercury can damage many parts of the human body, including the nervous system, the lungs, the kidneys, vision, and hearing. Although the seriousness of the risk depends on how much mercury a person is actually exposed to, the risk is significantly greater for fetuses and children that it is for adults. Pregnant women are actually often times advised to avoid working in jobs where they have a risk of being exposed to mercury liquid or vapors. "Many studies have documented health effects occurring to the neurological, immune, hormonal, and reproductive systems due to the high levels of mercury accumulating from chronic occupational exposure." (LCD, 2005). The most common source of maternal exposure to mercury vapor is amalgam fillings. The fetal mercury content after maternal inhalation of mercury vapor was found to be over 20 times that for maternal exposure to an equivalent dose of inorganic mercury. "Mercury is often stored in breast milk and the fetus at much higher levels than that in the mother. Milk from mothers with 7 or more fillings was found to have levels of mercury approximately 10 times that of amalgam free mothers." (Vimy, Takahashi, & Lorscheider, 1990). The highest levels of mercury are usually found in the pituitary gland of the fetus which then affects the development of the endocrine, immune, and reproductive systems. Mercury has been well documented to be "an endocrine system disrupting substance in animals and people, preferentially accumulating in and disrupting function of the pituitary gland, hypothalamus, and thyroid gland; along with disrupting or blocking enzyme production processes, glucose transfer, and many hormonal functions at very low levels of exposure." (LCD, 2005). It has been found that approximately one out of every six children in America born every year have been exposed to mercury levels so high that they are potentially at risk for things such as learning disabilities and motor skill impairment and even short-term memory loss. In fact one government analysis showed that 630,000 children each year are exposed to potentially unsafe mercury levels in the womb. Most of the difficulties stemming from mercury in regards to the affects on the human body arise from acute (larger doses) of exposure. Once in the body, mercury combines with sulfhydril groups in the cells and depresses the enzymatic system of the cells. It is known that "Repeated exposure at high levels can harm the central nervous system and cause mood swings, shaky hands, difficulty walking, slurred speech, hallucinations, and loss of memory and concentration." (Heimlich, n.d.). Although all forms of mercury are poisonous if absorbed into the body, in acute exposure, absorption of mercury through the blood system is very rapid. If treatment is not initiated within 10 to 15 minutes, the affect of the poisoning is set and may lead to death. Many things can occur after this: mental and nervous systems are not likely to be affected in acute as in chronic mercury poisoning; absorption through the skin (dermis) leads to a systemic poisoning; and if the entrance is through the eye, there is likely to be ulceration of the conjunctiva and cornea of the eye. There has also been substantial evidence which stands to show that there is as well a correlation between mercury and autism. Autism is a syndrome which is characterized by impairments in social relatedness, language and communication, a need for routine and sameness, abnormal movements, and sensory dysfunction. A recent study has found a possible link between higher mercury emissions and higher rates of autism. According to the study, "There was a significant increase. On average, for each 1,000 pounds of environmentally released mercury, there was a 43 percent increase in the rate of special education services and a 61 percent increase in the rate of autism." (Olmsted, 2005). Mercury is a toxic metal which can exist as either a pure element or in a variety of inorganic and organic forms and can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism. The role of mercury as a major possible cause of autism has only truly come to light in the past 18 months after it was realized that the amount of mercury preservative in many vaccines was well in excess of recommended safety standards." (Rimland, 2001). The concern of this correlation between mercury and autism has been highest in the United States where use of mercury is far more widespread and indeed where the number of vaccines received by children is higher at earlier ages and often times multiple vaccines are applied in a single day. The causes of autism are, for the most part, currently unknown; however, present knowledge suggests strongly that autism is a primary factor. However, people are not the only being affected by the toxic effects of mercury; wildlife and fish are at risk as well. In several areas of the United States, concentrations of mercury in fish and wildlife are high enough to be a significant risk to wildlife. "Scientists have discovered toxic effects in the field at concentrations of mercury that are toxic in the lab, and controlled lab studies have found toxic effects at concentrations that are common in certain environments." (USGS, 2000). The steadily increasing number and geographic extent of state advisories against the consumption of fish because of mercury contamination has raised the awareness of the ever wide-spreading nature of the mercury hazard. Studies have shown that "fish consumption advisories for methylmercury now account for more than three-quarters of all fish consumption advisories in the United States." (USGS, 2000). As with human beings, mercury can cause deformities and defects in wildlife and fish. Although one might presume that the most mercury would be found in highly polluted areas, this is not always the case. In certain higher polluted areas mercury has accumulated through industrial or mining activities and natural processes may have buried or diluted the mercury. On the other hand, in certain relatively pristine areas mercury concentrations have actually increased due to the fact that atmospheric deposition has increased. "For instance, concentrations of mercury in feathers of fish-eating seabirds from the northeastern Atlantic Ocean have steadily increased for more than a century." (USGS, 2000). Humans have used mercury in various forms for centuries now, and yet in the present day the issue of mercury is one of much greater importance and issue. This is primarily due to way humans live these days, as opposed to centuries ago. Human activity such as coal burning, incineration of wastes, and industrial emissions can release mercury into the environment. The real concerns with mercury today - especially that of methylmercury - are that, in toxic doses, it can cause neurological and developmental disorders in humans. "For an adult woman of average weight who eats four ounces of fish per week, all the fish would need to contain average tissue concentrations of 0.25 parts per million mercury to be toxic." (Heimlich, n.d.). While initial exposure to high concentrations of mercury vapor can produce symptoms similar to 'metal fume fever' including fatigue, fever, and chills, there can also be respiratory system effects such as cough, shortness of breath, and tightness and burning pains in the chest, as well as the coughing up of blood, impaired lung function, and inflammation of the lungs. In comparison to the short-term effects of mercury, the long-term effects are certainly more severe. The harmful effects of long-term exposure to mercury are generally thought to be caused by inhalation exposure. "However, mercury liquid and vapor are absorbed through the skin in small amounts and this route of exposure can contribute to the overall exposure. Effects following absorption through the skin are expected to be similar to those reported long-term inhalation exposure." (Heimlich, n.d.). From this review, we can see that the effects of mercury on the human body are significant and are becoming increasingly more common in the present day. Effects on the nervous system, kidneys, skin, digestive system, heart, immune and endocrine systems, respiratory system, and even on the eyes can range anywhere from subtle to severe and even life-threatening. Although the negative toxicological effects of mercury have been around for centuries, the issue is one of much more significance in the present day due to the fact that humans produce and waste significant amounts more than that of the civilizations centuries ago. Coal burning is one of the most primary conductors of mercury, which easily explains one of the most major reasons for the higher doses of mercury in the environment today. Oil is America's leading import/export, and although the issue of mercury is not often thought about in regards to this topic, we can see from a review of the literature and studies done that it is essential to begin considering the factors involved. Mercury is a significantly severe and potentially deadly element, and through the understanding of mercury and its correlation to such things as autism and birth defects, it is clear that we must create a solution in order to resolve the mercury issue. Works Cited Birth Defect Research for Children, Inc. "Mercury Poisoning." Birth Defects. 2001. 26 April 2006 < http://www.birthdefects.org/archives/News_jun01.htm> Clarkson, T. "The Toxicology of Mercury." Critical Reviews in Clinical Laboratory Sciences 34(3): 369-403, 1997. Drasch, G., Schupp, I., Hofl, H., Reinke, R., & Roider, G. "Mercury Burden of Human Fetal and Infant Tissues." Eur J Pediatrics 153: 607-610, 1994. Heimlich, Joe E. "Mercury." Ohioline. 26 April 2006 http://ohioline.osu.edu/cd-fact/0200.html Kingman, A., Albertini, T., & Brown, L. "National Institute of Dental Research, Mercury Concentrations in Urine and Blood Associated With Amalgam Exposure in the U.S. Military Population." Dent Res 77(3): 461-71, 1998. LCD. "Infertility, Birth Defects, and Fetal Development Effects Related to Mercury From Amalgam Dental Fillings." Curezone. 2005. 26 April 2006 < http://curezone.com/forums/m.aspf=629&i=27> Los Alamos National Laboratory. "Mercury." Radiochemistry. 2003. 26 April 2006 < http://www.radiochemistry.org/periodictable/elements/80.html> Lutz, E., Lind, B., Herin, P., Krakau, I., Bui, T. H., & Vahter, M. "Concentrations of Mercury, Cadmium, and Lead in Brain and Kidney of Second Trimester Fetuses and Infants." Journal of Trace Elements in Medicine and Biology 199(10): 61-67. Olmsted, Dan. "The Age of Autism: Mercury in the air." The Washington Times. 2005. 26 April 2006 http://www.washtimes.com/upi-breaking/20050314-052518-7615r.htm Traudt, Jon. "Air Pollution Health Effects." Air Pollution Health Effects. 2005. 26 April 2006 < http://healthandenergy.com/air_pollution_health_effects.htm> USGS. "Mercury in the Environment." USGS. 2000. 26 April 2006 http://www.usgs.gov/themes/factsheet/146-00/ Vimy, M. J., Takahashi, Y., & Lorscheider, F. L. "Maternal-Fetal Distribution of Mercury Released From Dental Amalgam Fillings." Amer J Physiol 8, 1990. Wikipedia. "Mercury." Wikipedia. 2006. 26 April 2006 Read More