Toxicity from Heavy Metals - Dissertation Example

? TABLE OF CONTENT The Toxi of Heavy Metals 2 Chapter One Introduction 2 Heavy Metals 2 Toxi in Heavy Metals 3 Toxic Effects of Heavy Metals 5 References 11 The Toxicity of Heavy Metals 2 Chapter One Introduction 2 Heavy Metals 2 Toxicity in Heavy Metals 3 Toxic Effects of Heavy Metals 5 References 11 The Toxicity of Heavy Metals Chapter One Introduction Heavy Metals The term heavy metal is an improperly defined subsidiary category of the elements that have the properties of metals. Several definitions of the term heavy metal have been forthcoming, and these are founded on atomic number, density, atomic weight, chemical properties or toxicity (Department for Environment Food and Rural Affairs, 2008). The Centre for Ecology & Hydrology (CEH) monitors some of the heavy metals. These are Aluminium (Al), Antimony (Sb), Arsenic (As), Barium (Ba), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Nickel (Ni), Lead (Pb), Manganese (Mn), Molybdenum (Mo), Rubidium (Rb), Scandium (Sc), Selenium (Se), Strontium (Sr), Tin (Sn), Titanium (Ti), Tungsten (W), Vanadium (V), Zinc (Zn) (Department for Environment Food and Rural Affairs, 2008). Heavy metals occur naturally in the crust of the Earth. These metals depict remarkable stability, and resist any attempt at degradation or destruction. As a consequence, heavy metals accumulate in sediments and soils. Some of the heavy metals have undergone drastic change in their biochemical and geological cycles, due to human activity (Department for Environment Food and Rural Affairs, 2008). Some of the primary man – made sources of heavy metals are the mines, smelters, foundries, traffic and by products of combustion. Heavy metals that are comparatively more volatile tend to be dispersed over vast areas through the atmosphere. In several cases, such heavy metals have been deposited thousands of miles from the site of their initial release into the atmosphere (Department for Environment Food and Rural Affairs, 2008). The suspension in the atmosphere of heavy metal particles, in general, depends on their size and lightness. Thus, heavy metal particles that are larger than 10 micro meters (µm) in diameter settle to the ground, under the influence of gravity. This takes a few hours for completion. However, the heavy metal particles that are less than 1µm in diameter persist in the atmosphere for weeks. Such particles are usually removed from the atmosphere, by precipitation (Department for Environment Food and Rural Affairs, 2008). A useful definition of heavy metals is given below. Heavy metals are chemical elements that have a specific gravity that is ? 5 times the specific gravity of water. At 40C the specific gravity is deemed to be 1, by convention. As such, specific gravity is the ration of the density of a substance to the density of water (LifeExtension, 2013). Toxicity in Heavy Metals Some of the toxic metals, whose specific gravity exceeds 5 times that of water are; arsenic with a specific gravity of 5.7, cadmium with a specific gravity of 8.65, iron with a specific gravity of 7.9, lead with a specific gravity of 11.34, and mercury with a specific gravity of 13.546 (LifeExtension, 2013). Heavy metals that cannot be metabolised by the human body accumulate in the soft tissues and become toxic. The entry of heavy metals into the human body is via air, food, water; and cutaneous absorption due to agricultural activity; exposure during manufacturing, industrial or pharmaceutical activity; or residential exposure (LifeExtension, 2013). With regard to adults, the entry of toxic heavy metals is frequently on account of industrial exposure to these substances. Among children, ingestion is the most common reason for the entry of toxic heavy metals. It has been determined that normal hand to mouth activity could lead to the development of toxic levels of heavy metals among children. The infrequent or rare routes of toxic heavy metal entry into the human body include radiological procedures, incorrect dosing or monitoring during intravenous nutrition, a broken thermometer that is used for measuring the temperature of a human, and an attempt at suicide of homicide (LifeExtension, 2013). In general, acute poisoning involving toxic heavy metals is the outcome of inhalation or contact with materials, fumes, vapours, or dust in the workplace. All the same, some instances of contamination have been discovered in the domestic environment, especially in houses with lead paint or old plumbing (LifeExtension, 2013). Some of the more important causes of heavy metal toxicity are the environmental sources. These could be based in the consumed food, water that is drunk, or excessive exposure to industrial metals and chemicals. The environment of an individual and that person’s living habits, usually determine the degree of exposure to heavy metal toxicity (Patients Medical, 2013). For instance, toxicity due to the heavy metal arsenic, includes exposure to insecticides, sources of potable water, and dermal contact with oils such as linseed oil. Some of the causes of acute exposure to toxic heavy metals includes; vaccination with material containing thimerosal, which is a mercury preservative; improper handling of toxic heavy metals; spills containing toxic heavy metals (Patients Medical, 2013). Chronic exposure takes place over time. Some of its instances are; silver fillings during dental work, which contain mercury amalgams; residing in a home, constructed prior to 1978, which has lead based paint; smoking or inhaling the smoke expelled by smokers; consuming food with high levels of toxic heavy metals; living near a landfill; and working in an atmosphere where exposure to toxic heavy metals is certain, such as a dentist’s office, wherein mercury amalgam is employed to fill dental cavities (Patients Medical, 2013). Toxic Effects of Heavy Metals Several studies have been conducted on the toxic effects of heavy metals. These have disclosed that heavy metals have the capacity to directly affect behaviour, by producing the impairment of mental and neurological function, influencing neurotransmitter production and utilisation, and changing a number of metabolic processes (Farr, 2009). Some of the systems that can be impaired are the circulatory and cardiovascular systems; detoxification pathways, such as the colon, liver, kidney and skin; endocrine system; energy production pathways; and the enzymatic, gastrointestinal, immune, nervous, reproductive and urinary systems (Farr, 2009). The health of an individual can be seriously damaged, upon inhaling heavy metal particles, even if these are present to levels that are deemed to be non – toxic. In fact, most if not all aspects of the immune system are seriously compromised due to the inhalation of heavy metal particulates. Furthermore, heavy metals can enhance allergic reactions, engender genetic mutation, displace the beneficial trace metals at the biochemical bond sites, and destroy harmful and beneficial bacteria (Farr, 2009). The damage caused by heavy metals stems, principally, from the proliferation of the free radicals that they produce. A free radical is an electrically unbalanced molecule, and this imbalance is due to the total electrons in that molecule being lesser than the protons in that molecule. Such molecules displace electrons from other molecules, in order to become electrically neutral (Farr, 2009). The natural production of free radicals occurs when cell molecules undergo oxidation. However, the presence of a heavy toxic load or antioxidant deficiencies, results in the uncontrolled production of free radicals. When free radicals remain uncontrolled, they damage the tissue throughout the body. Such damage is the basis for all the degenerative diseases. However, the vitamins A, C, and E dramatically reduce free radical activity (Farr, 2009). Another danger posed by heavy metals is that they increase the acidity of the blood. The bones provide blood with calcium, in order to restore the correct pH of the blood (Farr, 2009). The term pH is given by the equation: pH = – log10 [H+]. Where, [H+] denotes the hydrogen ion concentration (Campbell & Farrell, 2011, p. 23). In addition, heavy metal toxicity results in the inflammation of arteries and tissues, and this results in a greater amount of calcium being drawn to the area as a buffer. This calcium forms a coating over the inflamed blood vessels, which causes the hardening of the arterial walls. Finally, the artery undergoes blockage. When calcium is not replenished to the extent necessary, then the bones develop osteoporosis, due to the constant removal of calcium. The bones become brittle (Farr, 2009). Contemporary research studies have shown that negative health outcomes result from the presence of even minute levels of toxic elements. The response of an individual depends on nutritional status, metabolic rate, capacity to detoxify toxic substances, and the type and extent of exposure to heavy metals. The most vulnerable groups to such toxicity are the children and the elderly. This is due to their underdeveloped or age compromised state, respectively (Farr, 2009). The chief danger to human health from heavy metals is on account of exposure to arsenic, cadmium, lead and mercury. Cadmium is principally used in the rechargeable nickel cadmium batteries. The practice of dumping cadmium containing products instead of recycling them, has resulted in the drastic emission of cadmium. In addition, the smoking of cigarettes constitutes a major source of cadmium (Jarup, 2003, p. 167). With regard to people who do not smoke tobacco, food is the chief source of exposure to cadmium. A disturbing fact disclosed by contemporary research data is that the adverse health effects of exposure to cadmium can take place at lower exposure levels. The main adverse health effects are damage to the kidneys, insalubrious effects on the bones and fractures (Jarup, 2003, p. 167). Cadmium exposure proves to be extremely harmful to humans. This is on account of their relative inability to expel cadmium from their body. The kidneys excrete and then re – absorb this metal. Severe respiratory irritation follows acute high dose exposure to cadmium. The occupational levels of exposure to cadmium generates a tangible risk factor for testicular degeneration and chronic pulmonary disease. Exposure to cadmium has been suspected of being a risk factor for cancer of the prostate (Hu, 2002). At lower levels, exposure to cadmium is related to toxicity of the kidneys. It has been established that cadmium damages the proximal tubules of the nephrons. This damage is initially observed as leakage of essential ions and proteins with a low molecular weight. This progresses over time to frank kidney failure (Hu, 2002). These outcomes are irreversible, and such risks are present even at lower levels of exposure that what had been previously believed. In addition, cadmium can engender metabolic effects with pathological outcomes upon the kidneys. One of the main dangers related to cadmium exposure is the loss of calcium (Hu, 2002). This can result in the weakening of the bones. Thus, the disease Itaiitai, which was noticed in Japan, and which is an epidemic of bone fractures, has been attributed to gross contamination of rice stocks with cadmium. This disease has been noticed in communities residing in areas with comparatively smaller cadmium contamination. In this population, it was seen that there was an increase in the risk of bone fractures among females. In addition, there was a reduction in bone density and height loss that was independent of gender (Hu, 2002). With regard to the purification of water, the European Union (EU) has issued the Water Framework Directive. This initiative is a major development in the water policy of the European countries, as it addresses the scope of water protection, and the development and implementation of such policy (Bloch, 2005). The European Commission has adopted a transparent system of working, in this regard, and has taken all possible measures to involve all the stakeholders, the scientific community and NGOs. After engaging in a broad consultation exercise with all the interested and involved parties, the European Commission issued this Directive (Bloch, 2005). This Directive consists of the following pillars. All waters are to be accorded protection, which includes groundwater, surface water and coastal water; all waters are to attain good quality by the year 2015; the term good status has been clearly and comprehensively defined; water management of river basins; and limiting emission values, while ensuring quality norms and eliminating the use of particularly hazardous substances. In addition, there has to be a single coherent managerial frame with regard to economic instruments underlying the environmental goals (Bloch, 2005). Waters of the EU Member States will be protected by this Directive. A novel feature of the Water Framework Directive is that it encompasses surface and groundwater, as well as estuaries and marine waters. The objective of this Directive is to prevent further deterioration of waters, to support sustainable water consumption that is founded on long term protection of water resources; and to contribute to water supply in the quality and quantity necessary for its use in a sustainable manner (Bloch, 2005). The Member States of the EU are required to establish a deadline for achieving a good status for all their waters. The time specified for this achievement is the year 2015. A few derogations have been permitted, which have been correlated to certain conditions. With regard to groundwater, good status is determined by quantity and chemical purity. However, with regard to surface waters, the specified criteria are chemical quality and ecological quality (Bloch, 2005). References Bloch, H., 2005. European Union legislation on wastewater treatment and nutrients removal. [online] Available at: [Accessed 30 April 2013]. Campbell, M. K. & Farrell, S. O., 2011. Biochemistry. 7 ed. Cengage Learning. Department for Environment Food and Rural Affairs, 2008. What are heavy metals?. [online] Available at: [Accessed 24 April 2013]. European Parliament, Council, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Bruxelles/Brussels Belgium. Farr, G., 2009. Why Heavy Metals are a Hazard to Your Health. [online] Available at: [Accessed 24 April 2013]. Hu, H., 2002. Human Health and Heavy Metals Exposure. [online] Available at: [Accessed 30 April 2013]. Jarup, L., 2003. Hazards of heavy metal contamination. British Medical Bulletin, 68(1), pp. 167 – 182. LifeExtension, 2013. Heavy Metal Detoxification. [online] Available at: [Accessed 24 April 2013]. Patients Medical, 2013. Causes of Heavy Metal Toxicity. [online] Available at: [Accessed 24 April 2013]. Read More