Heavy Metal in the Context of Environmental Toxicology - Term Paper Example

HEAVY METAL IN THE CONTEXT OF ENVIRONMENTAL TOXICOLOGY Introduction Over years, the word “heavy metals” has been utilized in a variety of legislations and publications linked to the safe utilization of chemicals and chemical hazards. The name often refers to a category name of metalloids (semimetals) and metals associated with eco-toxicity or toxicity potential and contamination (Daffus, 2002). There is an assumption that all heavy-metals and their compounds have properties that are eco-toxic or highly toxic. However, this assumption has no fundamental basis on the available toxicological or chemical data. Legal regulations have specified an inventory of heavy metals applied in various situations. There is no definition that is authoritative in literatures that are relevant. There is a tendency of assuming that all heavy metals in conjunction with their compounds have properties that are highly eco-toxic or toxic. Arguably, this assumption has no prove in toxicological or chemical data. Hence, the term heavy metal is misleading and meaningless. Furthermore, the word metal is also misused in legislation and toxicological data. In these literatures it is used to mean a metal that is pure and the entire species chemical in which it occurs. This is untrue because, all pure metals can not exhibit similar toxicological and chemical properties. For purposes of avoiding the term heavy metal, there is need for reclassification of the periodic table as people refer to the term heavy metal as misleading and meaningless. The change in classification should mirror individuals understanding of toxicity chemical basis and provide room for the prediction of toxic impacts. Classification of heavy metals The increased worry on environmental pollution reduction has triggered the continued literature and research on heavy metals toxicology (Rabajczyk et al., 2011). Heavy metals emit their toxic substances through the formation of complexes with compounds that are organic. These eventually results to formation of modified biological molecules that lose their functioning ability. The outcome is affected cell malfunction or death. The most common heavy metals that form organic compounds that are complex are such as oxygen, sulfur and nitrogen. Classification of heavy metals is done depending on which class it lies. For example class A belong to the hard metals, class be identifies soft metals and lastly we have the intermediate metals. Heavy metals such as Mercury, Lead and cadmium fall under class B which represents soft metals. On the other hand chromium is an intermediate metal. The classification of these metals varies depending on their chemical formula. How Heavy Metal Occurs in the Environment Through causes that are both anthropogenic and natural, heavy metals find their way into the environment. The major emission causes are human sources such as mining operations. Heavy metals are exposed into the environment in forms that are both inorganic and organic. Anthropogenic sources of emissions occur from both point and non-point sources such as industrial areas such as present and previous sites of mining, smelters and foundries and by-products and traffics combustion. The pollution of the environment by heavy metals is acute in mining locations and it decreases as the distance widens from those mining sites. The heavy metals are often leached into the soil and ground water. Those in sloppy areas find their way into the water bodies through surface runoff. The heavy metals eventually attach themselves to the sediments whilst some leak into the waters underground resulting to their contamination. Underground and surface water sources heavy metal contamination leads to soil pollution. Exposure of the heavy metals to air and rain is via dumping on the surface soil. Pollution of Agricultural soils results to the uptake of the heavy metals by plants resulting to their accumulation in the plant tissues. These consequently happen to those marine animals and domestic animals that feed on the contaminated plants resulting to the accumulation of the heavy metals in their body tissues. Human beings are vulnerable to heavy metal pollution. This is due to their consumption of plants and animals that are contaminated. This subsequently results to biochemical disorders. In conclusion, all biota’s get contaminated along their food chain cycles. Human beings at home get contaminated via utilization of industrial products made from heavy metals. Disinfectants, organo-metallics, anti-fungal agents, creams and toiletries expose an individual to Mercury, whereas artist paints and batteries made from cadmium or Nickel exposes an individual to Cadmium metal. Moreover, bottle wraps of wine, mirror coatings, old paints, tiles just to mention a few exposes an individual to lead metal. Despite the toxicity of the heavy metals, they are significant in various aspects of human life. Table 1 indicates United State Environmental Protection Agency (USEPA) Maximum level of heavy metal contamination in water, soil and air. Examples of Heavy metals Max.conc in air(mg/m3) Max.conc. in sludge(soil)(mg/kg) Max.conc. in drinking water()mg/l) Max.conc in water supporting aquatic life(mg/l) Cd 0.1-0.2 85 0.005 0.0088 Pb -- 420 0.01π(0.0) 0.00588 Zn2 1, 5* 7,500 5.00 0.07668 Hg -- 50 Ag 0.01 -- 0.0 0.1 As -- -- 0.01 -- Reasons why Heavy metals are toxic Toxicity of heavy metals only result when the body does not metabolize them thus accumulating in the body’s soft tissues. They do enter the body of human beings via water, air, food or through skin absorption as a result of contact in manufacturing and agriculture, industrial, residential or pharmaceutical settings. For adults, heavy metal contact occurs in industrial settings where as for children it is through ingestion (Cheng et al. 2009). Chronic poisoning results from dust, vapour, and fumes inhalation or through skin contact in workplace environments. Low levels of poisoning occur in dilapidated homesteads painted with lead or with aged plumbing. Extremely larger portions of the heavy metals may result to chronic or acute toxicity. There are consequences associated with the heavy poisoning of these metals. For instance, they may lead to damaging or reduced functioning of the mental and the central nervous system. Furthermore, they may result to extremely low energy levels, blood composition, liver, kidney and lung damage. Heavy metals long-term exposure may trigger serious conditions such as slow physical progression, degenerative processes such as neurological and muscular that enhances diseases such as the Parkinson’s and Alzheimer’s and multiple sclerosis. In addition to that, repetitive long-term exposure can result to cancer (“Heavy Metals Toxicity”) It is common to identify some heavy metals whose level of toxic are slightly above natural background concentrations found in nature. It is hence crucial for individuals to acknowledge the importance of taking preventive measures when exposed to excessive heavy metal. In United States of America, toxicity due to heavy metals is a rare medical condition. Nevertheless, it is a significant clinical condition when reported. On the other hand, if toxicity is treated inappropriately, or goes unrecognized, can result to reduction in the quality of life and major illnesses. Testing is essential for individuals suspected to possess heavy metal toxicity and conventionally natural and appropriate medical procedures need persuasion. Why heavy metals are essential Minute amounts of the heavy metals are present in the diet and in the environment and are essential for good health. In low quantities, specific heavy metals such as zinc, manganese, iron and copper are essential nutritionally for a life that is healthy. Mostly, they are found in foodstuffs (naturally), in vegetables and fruits and in multivitamin products that are available commercially. Some are injected into the body via diagnostic medical procedures. For instance, the direct gallium injection during procedures such as radiological, parenteral nutrition mixtures dosing with chromium metal and the utilization of lead metal in shielding radiation around x-ray equipment. Heavy metals are also vital in industrial applications. For example, they are utilized in industries for production of crucial products such as the disinfectants, accumulators, thermometers, utensils among other vital products. Since the metals are essential, adequate occupational hygiene and precautions should be considered while using them. Industries should ensure the treatment of their effluents before discharging them into the water ecosystems to reduce bioaccumulation of the metals in the water bodies. Conclusion Any metallic element with high relative density and toxic at concentrations that are low is referred to as heavy metal. The term is collectively used to apply to the metals and metalloid groups having an atomic density of higher than 4g/cm3 or 5 times more compared to water. Metals that fall under heavy metals are such as cadmium (Cd), Lead (Pb), mercury (Hg), Arsenic (As), Chromium (Cr) among others (Ogwuebu and Egwurugwu, 2007). Heavy metals are natural components of the earth crust. They are contaminants than persist in the environment for a longer time as they can neither be destroyed nor degraded. They get into the human body system through air, water, food and over time they bio-accumulate. Pollution of the environment has become one of the worst problems in the world. Heavy metals are recognized as the significant pollutants. The conglomeration of industries has triggered the increased pollutants emission into various ecosystems such as aquatic, land and atmospheric ecosystems. Population increase with technology and production development has enhanced the inadequate attention to the safety of the environment. Bibliography Cheng, W., Zhang, X., Wang, K., & Dai, X, ‘Integrating Classification and Regression Tree (CART) with GIS for Assessment of Heavy Metals Pollution’, Environmental Monitoring and Assessment, vol.158, 2009, pp419-431. 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Rabajczyk, A., Jozwiak, M., Kozlowski, R, ’Heavy Metals ( Cd, Pb, Cu, Zn, Cr) in Bottom Sediments and the Recultivation of Kielce Lake’, Polish Journal of Environmental Studies, 2011, pp1014-1018. Read More