Mercury Exposure in Children's Health

Topics: Mercury, Mercury poisoning, Methylmercury Pages: 16 (5524 words) Published: October 1, 2012
Mercury exposure has become a serious, mainstream topic that has attracted mass amounts of global attention. Exposure to toxic levels of mercury is devastating to the developing central nervous system and general physiological systems in humans. Studies have suggested that mercury exposure can affect limb coordination, academic performance and mercury may have a role in other developmental disorders. There are many ways humans may be exposed to mercury in their daily lives. Populations with a high dietary intake of seafood are most likely to be at risk for mercury exposure. Mercury is a derivative from both natural and man-made sources and is known worldwide to be a contaminant in aquatic environments. There are multiple sources of mercury exposure. Some sources include fish consumption, thermometers, vaccinations, dental amalgams and the atmosphere. This paper aims to examine the correlation between prenatal and postnatal mercury exposure in children and associated neurological functioning. Neurological functioning is defined as aspects affecting behaviour, learning, motor functioning and IQ. Throughout this paper, multiple literature sources are studied to assess the evidence of adverse effects of neurological development in children as a result of low- dose mercury exposure. Studies were done in multiple countries with various sample sizes and sources of exposure. Our review focuses on children because they are the most vulnerable to environmental threats as children are constantly growing and developing. Our studies also focus on exposure to low levels of mercury because it is not understood as well as acute toxicity to mercury exposure (PP, 2003). Chronic exposure to low level mercury is an important area of mercury health research because the general population is primarily exposed to this form. Understanding the mechanisms and exposure pathways can aid to limit mercury exposures. Also, future regulations on the safe level of mercury exposure can be established as increasing populations become aware of this issue.

Sources of Mercury Exposure:
There are several sources of mercury exposure which include methylmercury, ethylmercury, elemental mercury vapor, inorganic mercury and metallic mercury. Three forms of mercury species exist: elemental mercury (Hg0), inorganic mercury compound (I-Hg) and organic mercury (MeHg). Exposure to each species may result in specific, general toxicological effects in children (Counter et al., 2004). Methylmercury Children are exposed to methylmercury through oral ingestion of fish, marine mammals, crustaceans, animals and poultry that is fed fish meal. Inorganic mercury that is deposited in aquatic environments is converted through methylation to methylmercury by microorganisms (Zahir et al., 2005). Methylmercury is then biomagnified through the food chain resulting in a high concentration of methylmercury in large predatory fish and some marine mammals that are then consumed by humans (Zahir et al., 2005). The exposure level of methylmercury can be measured by biomarkers such as hair, blood or umbilical cord blood samples. There are multiple ways in which methylmercury can be absorbed by the human body. First, is through inhalation, where vapor of methylmercury is inhaled and absorbed by the body. Secondly, methylmercury can be absorbed by oral exposure and dermal exposure. Almost 95% of methylmercury contained in contaminated fish is absorbed through the human gastrointestinal tract. About 3 to 5% of an applied dose is absorbed through the dermal pathway. Approximately 10% of the absorbed oral dose of methylmercury is distributed to the blood, 50% to the liver and 10% to the brain (Counter et al., 2004). Methylmercury undergoes a biotransformation process within the body. Methylmercury demethylates to mercuric mercury. The biotransformation process, demethylation, can be found especially in human tissue macrophages, human intestinal flora and in the liver of...
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