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Heavy Metals

NAME: Aluminium

CLASSIFICATION: Heavy metal

DESCRIPTION: Metal that has resistant properties to corrosion. It is used in foil, kitchenware and automobile and aircraft industries. Workers who are at risk for toxicity are those in refineries, foundries and also welders and grinders. Dialysis patients can also have toxicity. Aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al and its atomic number is 13. It is not soluble in water under normal circumstances. Aluminum is the most abundant metal in the Earth's crust, and the third most abundant element, after oxygen and silicon. It makes up about 8% by weight of the Earth's solid surface. Aluminium is too reactive chemically to occur in nature as a free metal. Instead, it is found combined in over 270 different minerals the chief source of aluminium is bauxite ore. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are very important in other areas of transportation and building. Its reactive nature makes it useful as a catalyst or additive in chemical mixtures, including ammonium nitrate explosives, to enhance blast power.

HEALTH PROBLEMS:  Despite its natural abundance, aluminium has no known function in living cells and presents some toxic effects in elevated concentrations. Its toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardation. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood-brain barrier. A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium, such as deodorants or antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts. Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in general, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levels. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption, and maltol has been shown to increase the accumulation of aluminium in nervous and osseous tissue. Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. The estrogen-like effects of these salts have led to their classification as a metalloestrogen. It may cause conjunctivitis, eczema, upper airway irritation, pneumoconiosis, and especially with dialysis patients, neurotoxicity and osteomalacia. Using dialysis water aluminum concentration should be lower than 10-micrograms/ deciliter. Exposure limits are 15mg/m3 for dust and 5mg/m3 for respirable particles.


NAME: Antimony

CLASSIFICATION: Heavy metal

DESCRIPTIONS: it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Although the use of antimony is limited by its toxicity, its compounds have been of fundamental value in chemistry - a prominent example being the development of superacids derived from antimony pentafluoride. Antimony compounds are prominent fire retardants found in many commercial and domestic products. Certain alloys are valuable for use in solders and ball bearings. An emerging application is the use of antimony in microelectronics.Used with lead for the production of semiconductors and thermoelectric devices. Other exposures include pharmaceuticals, mining, making pewter, solder, and storage battery plates.

HEALTH PROBLEMS: Antimony and many of its compounds are toxic at very high levels. Inhalation of antimony dust is harmful; in small doses, antimony causes headaches, dizziness, and depression. Larger doses such as prolonged skin contact may cause dermatitis; otherwise it can damage the kidneys and the liver, causing violent and frequent vomiting. Cardiotoxicity occurs with antimony pharmaceuticals. Occupational exposure - irritation of mucus membranes, eczema, chemical burns, perforation of the nasal septum, antimony spots, benign pneumoconiosis. 


NAME: Arsenic

CLASSIFICATION: Metalloid

DESCRIPTION: Arsenic is a chemical element with the symbol as, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, mainly combined with sulfur and metals, and naturally in the native (elemental) state. Albertus Magnus first documented it in 1250. Arsenic is a metalloid. It can exist in various allotropes, although only the grey form is industrially important. The main use of metallic arsenic is for strengthening alloys of copper and especially leads (for example, in automotive batteries). Arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon. A few species of bacteria are able to use arsenic compounds as respiratory metabolites, and are arsenic-tolerant. However, arsenic is notoriously poisonous to multicellular life, due to the interaction of arsenic ions with protein thiols. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides (treated wood products), herbicides and insecticides. These applications are declining, however, as many of these compounds are in the process of being banned

HEALTH PROBLEMS:  Acute effects - vomiting, colic and diarrhea, fever, cardiotoxicity, shock, and death. Inhaled Arsine causes dizziness, headache, hemolysis, jaundice, kidney damage and death. Chronic effects - sensorimotor neuropathy, eczema, hyperkeratosis, hyperpigmentation, vascular effects including Raynaud's, acrocyanosis and necrosis. Arsenic is associated with lung cancer.


NAME: Barium

CLASSIFICATION: Alkaline earth metal

DESCRIPTION: is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with water and carbon dioxide and is not found as a mineral. The most common naturally occurring minerals are the very insoluble barium sulfate, BaSO4 (barite), and barium carbonate, BaCO3 (witherite). Barium's name originates from Greek barys meaning "heavy", describing the high density of some common barium-containing ores. Barium has few industrial applications, but the metal has been historically used to scavenge air in vacuum tubes. Barium compounds impart a green color to flames and have been used in fireworks. Barium sulfate is used for its density, insolubility, and X-ray opacity. It is used as an insoluble heavy mud-like paste when drilling oil wells, and in purer form, as an X-ray radiocontrast agent for imaging the human gastrointestinal tract. Soluble barium compounds are poisonous due to release of the soluble barium ion, and have been used as rodenticides. New uses for barium continue to be sought. It is a component of some "high temperature" YBCO superconductors, and electroceramics.

HEALTH PROBLEMS: Because it is insoluble in water as well as stomach acids, barium sulfate can be taken orally. It is eliminated from the digestive tract. Unlike other heavy metals, barium does not bioaccumulate. However, inhaled dust containing barium compounds can accumulate in the lungs, causing a benign condition called baritosis. Soluble salts cause hypokalemia. Acute poisoning - smooth muscle stimulation, vomiting, colic, diarrhea and eventual paralysis.


NAME: Beryllium

CLASSIFICATION: Heavy metal

DESCRIPTION: Beryllium is the chemical element with the symbol Be and atomic number 4. A divalent element only occurs naturally in combination with other elements in minerals. Notable gemstones, which contain beryllium, include beryl (aquamarine, emerald) and chrysoberyl. As a free element, it is a steel-gray, strong, lightweight and brittle alkaline earth metal.

It is primarily used as a hardening agent in alloys. Structurally, highly flexural rigidity, thermal stability, thermal conductivity and low density  of 1.85 times that of water makes beryllium a quality aerospace material for high-speed aircraft, missiles, space-vehicles and communication satellites. Because of its low density and atomic mass, beryllium is relatively transparent to X-rays and other forms of ionizing radiation therefore; it is the most common window material for X-ray equipment and in particle physics experiments. The commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium is corrosive to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in some people. As it is not synthesized in stars, beryllium is a relatively rare element in both the Earth and the universe. The element is not known to be necessary or useful for either plant or animal life.

HEALTH PROBLEMS: The toxicity of beryllium depends upon the duration, intensity and frequency of exposure (features of dose), as well as the form of beryllium and the route of exposure (e.g., inhalation, dermal, ingestion). According to the International Agency for Research on Cancer (IARC), beryllium and beryllium compounds are Category 1 carcinogens; they are carcinogenic to both animals and humans. Chronic berylliosis is a pulmonary and systemic granulomatous disease caused by exposure to beryllium. Acute beryllium disease in the form of chemical pneumonitis was first reported in Europe in 1933 and in the United States in 1943. Cases of chronic berylliosis were first described in 1946 among workers in plants manufacturing fluorescent lamps in Massachusetts.


NAME: Cadmium

CLASSIFICATION: Heavy metal

DESCRIPTION: is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white metal is chemically similar to the two other metals in-group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low melting point compared to transition metals. Cadmium and its congeners are not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. Average concentration in the earth’s crust is between 0.1 and 0.5 parts per million (ppm). It was by Stromeyer and Hermann, both in Germany discovered simultaneously, as an impurity in zinc carbonate. Cadmium occurs as a minor component in most zinc ores and therefore is a byproduct of zinc production. Cadmium was used for a long time as a pigment and for corrosion resistant plating on steel. Cadmium compounds were used to stabilize plastic. With the exception of its use in nickel-cadmium batteries and cadmium telluride solar panels, the use of cadmium is generally decreasing in its other applications. These declines have been due to competing technologies, cadmium’s toxicity in certain forms and concentration and resulting regulations. Although cadmium is toxic, one enzyme, a carbonic anhydrase with cadmium as reactive center has been discovered.

HEALTH PROBLEMS: The most dangerous form of occupational exposure to cadmium is inhalation of fine dust and fumes, or ingestion of highly soluble cadmium compounds. Inhalation of cadmium-containing fumes can result initially in metal fume fever but may progress to chemical pneumonitis, pulmonary edema, and death. Cadmium is also an environmental hazard. Human exposures to environmental cadmium are primarily the result of fossil fuel combustion, phosphate fertilizers, natural sources, iron and steel production, cement production and related activities, nonferrous metals production, and municipal solid waste incineration. However, there have been a few instances of general population toxicity as the result of long-term exposure to cadmium in contaminated food and water. In the decades leading up to World War II, Japanese mining operations contaminated the Jinzu River with cadmium and traces of other toxic metals. Therefore, cadmium accumulated in the rice crops growing along the riverbanks downstream of the mines. Some members of the local agricultural communities consuming the contaminated rice developed itai-itai disease and renal abnormalities, including proteinuria and glucosuria. The victims of this poisoning were almost exclusively post-menopausal women with low iron and other mineral body stores. Similar general population cadmium exposures in other parts of the world have not resulted in the same health problems as long as the populations maintained sufficient iron and other mineral levels. Thus, while cadmium is a major factor in the Itai Itai disease in Japan, most researchers have concluded that it was one of several factors. Cadmium is one of six substances banned by the European Union's Restriction on Hazardous Substances.


NAME: Chromium

CLASSIFICATION: Heavy metal

DESCRIPTION: is a chemical element that has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray,  lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable. The name of the element is derived from the Greek word "chroma"   meaning colour, because many of its compounds are intensely coloured. It was discovered by Louis Nicolas Vauquelin in the mineral crocoite (lead chromate) in 1797. Crocoite was used as a pigment, and after the discovery that the mineral chromite also contains chromium; this latter mineral was used to produce pigments as well.
Chromium was regarded with great interest because of its high corrosion resistance and hardness. A major development was the discovery that steel could be made highly resistant to corrosion and discoloration by adding chromium to form stainless steel. This application, along with chrome plating (electroplating with chromium) is currently the highest-volume uses of the metal. Chromium and ferrochromium are produced from the single commercially viable ore, chromite, by silicothermic or aluminothermic reaction or by roasting and leaching processes. Although trivalent chromium is required in trace amounts for sugar and lipid metabolism, few cases have been reported where its complete removal from the diet has caused chromium deficiency. In larger amounts and different forms, chromium can be toxic and carcinogenic. The most prominent example of toxic chromium is hexavalent chromium. Abandoned chromium production sites often require environmental cleanup.

HEALTH PROBLEMS: Water insoluble chromium compounds and chromium metal are not considered a health hazard, while the toxicity and carcinogenic properties of chromium have been known for a long time. Because of the specific transport mechanisms, only limited amounts of chromium enter the cells. Several in vitro studies indicated that high concentrations of chromium in the cell could lead to DNA damage. Acute oral toxicity ranges between 1.5 and 3.3 mg/kg.  The proposed beneficial effects of chromium and the use as dietary supplements yielded some controversial results, but recent reviews suggest that moderate uptake of chromium through dietary supplements poses no risk.


NAME: Cobalt

CLASSIFICATION: Heavy metal

DESCRIPTION: is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. Cobalt-based blue pigments have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought by alchemists to be due to the known metal bismuth. Miners had long used the name kobold ore (German for goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the kobold. Nowadays, some cobalt is produced specifically from various metallic-lustered ores, for example, cobaltite (CoAsS), but the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo and Zambia yields most of the cobalt metal mined worldwide. Cobalt is used in the preparation of magnetic, wear-resistant and high-strength alloys. Cobalt silicate and cobalt(II) aluminates (CoAl2O4, cobalt blue) give a distinctive deep blue color to glass, smalt, ceramics, inks, paints and varnishes. Cobalt occurs naturally as only one stable isotope, cobalt-59. Cobalt-60 is a commercially important radioisotope, used as a radioactive tracer and in the production of gamma rays. Cobalt is the active center of coenzymes called cobalamin or vitamin B12, and is an essential trace element for all animals. Cobalt is also an active nutrient for bacteria, algae and fungi.

HEALTH PROBLEMS: Cobalt is an essential element for life in minute amounts. The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg. Thus, for a 100 kg person the LD50 would be about 20 grams. After nickel and chromium, cobalt is a major cause of contact dermatitis and is considered carcinogenic. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to cardiomyopathy, which came to be known as beer drinkers cardiomyopathy.


NAME: Copper

CLASSIFICATION: Heavy metal

DESCRIPTION: Copper occurs naturally in elemental form and as a component of many different compounds. The most toxic form of copper is thought to be that in the divalent state, cupric (Cu2+). Because of its high electrical conductivity, copper is used extensively in the manufacturing of electrical equipment and different metallic alloys. Copper is released into the environment primarily through mining, sewage treatment plants, solid waste disposal, welding and electroplating processes, electrical wiring materials, plumbing supplies (pipes, faucets, braces, and various forms of tubing), and agricultural processes (ATSDR 1990a). It is present in the air and water due to natural discharges like volcanic eruptions and windblown dust.     Drinking water sources become contaminated with copper primarily because of its use in many different types of plumbing supplies. It is a common component of fungicides and algaecides, and agricultural use of copper for these purposes can result in its presence in soil, ground water, farm animals (grazing animals like cows, horses, etc.) and many forms of produce. Copper is also present in ceramics, jewelry, monies (coins) and pyrotechnics (ACGIH 1986). Though copper is an essential trace element required by the body for normal physiological processes, increased exposure to copper containing substances can result in copper toxicity and a wide variety of complications. 

HEALTH PROBLEMS: Absorption of copper occurs through the lungs, gastrointestinal tract and skin (U.S. EPA, 1987). The degree to which copper is absorbed in the gastrointestinal tract largely depends upon its chemical state and the presence of other compounds, like zinc (U.S.A.F., 1990). Once absorbed, copper is distributed primarily to the liver, kidneys, spleen, heart, lungs, stomach, intestines, nails, and hair. Individuals with copper toxicity show an abnormally high level of copper in the liver, kidneys, brain, eyes and bones. Acute toxicity of ingested copper is characterized by abdominal pain, diarrhea, vomiting, tachycardia and a metallic taste in the mouth. Continued ingestion of copper compounds can cause cirrhosis and other debilitating liver conditions.


NAME: Gadolinium

CLASSIFICATION: Ductile Rare Earth Metal

DESCRIPTION: Gadolinium is a chemical element with the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare earth metal. Gadolinium has exceptionally high absorption of neutrons and therefore is used for shielding in neutron radiography and in nuclear reactors. Because of its paramagnetic properties, solutions of organic gadolinium complexes and gadolinium compounds are the most popular intravenous MRI contrast agents in medical magnetic resonance imaging.

HEALTH PROBLEMS: As a free ion, gadolinium is highly toxic, but MRI contrast agents are chelated compounds and are considered safe. The toxicity depends on the strength of the chelating agent. US Food approved Gd chelated contrast agents  include: Omniscan, Multihance, Magnevist, ProHance, Vasovist, Eovist and OptiMARK. 

Gadolinium MRI contrast agents have proved safer than the iodinated contrast agents used in X-ray radiography or computed tomography. Anaphylactoid reactions are rare, occurring in approx. 0.03–0.1%. Although gadolinium agents have proved useful for patients with renal impairment, in patients with severe renal failure requiring dialysis there is a risk of a rare but serious illnesses, such as nephrogenic systemic fibrosis and nephrogenic fibrosing dermopathy, that may be linked to the use of certain gadolinium-containing agents. Current guidelines in the United States are that dialysis patients should only receive gadolinium agents where essential, and that dialysis should be performed as soon as possible after the scan is complete, in order to remove the agent from the body promptly. However, after several years of controversy during which up to 100 Danish patients have been gadolinium poisoned (and some died) after Omniscan use, it has been admitted by the Norwegian medical company Nycomed that they were aware of the dangers of using gadolinium based agents for their product.


NAME: Iron

CLASSIFICATION: Heavy metal

DESCRIPTION: Iron is a chemical element with the symbol Fe (Latin: ferrum) and atomic number 26. It is a metal in the first transition series. It is the most common element in the whole planet Earth, forming much of Earth's outer and inner core, and it is the fourth most common element in the Earth's crust. It is produced in abundance as a result of fusion in high-mass stars, where the production of nickel-56 (which decays to iron) is the last nuclear fusion reaction that is exothermic, becoming the last element to be produced before collapse of a supernova leads to events that scatter the precursor radionuclides of iron into space. Iron metal has been used since ancient times, though lower-melting copper alloys were used first in history. Pure iron is soft (softer than aluminium), but is unobtainable by smelting. The material is significantly hardenened and strengthened by impurities from the smelting process, such as carbon. A certain proportion of carbon (between 0.2% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to cast iron. Further refinement with oxygen reduces the carbon content to make steel. Steels and low carbon iron alloys with other metals (alloy steels) are by far the most common metals in industrial use, due to their great range of desirable properties.

HEALTH PROBLEMS: Large amounts of ingested iron can cause excessive levels of iron in the blood. High blood levels of free ferrous iron react with peroxides to produce free radicals, which are highly reactive and can damage DNA, proteins, lipids, and other cellular components. Thus, iron toxicity occurs when there is free iron in the cell, which generally occurs when iron levels exceed the capacity of transferrin to bind the iron. Damage to the cells of the gastrointestinal tract can also prevent them from regulating iron absorption leading to further increases in blood levels. Iron typically damages cells in the heart, liver and elsewhere, which can cause significant adverse effects, including coma, metabolic acidosis, shock, liver failure, coagulopathy, adult respiratory distress syndrome, long-term organ damage, and even death. Humans experience iron toxicity above 20 milligrams of iron for every kilogram of mass, and 60 milligrams per kilogram is considered a lethal dose. Overconsumption of iron, often the result of children eating large quantities of ferrous sulfate tablets intended for adult consumption, is one of the most common toxicological causes of death in children under six.  The Dietary Reference Intake (DRI) lists the Tolerable Upper Intake Level (UL) for adults as 45 mg/day. For children under fourteen years old the UL is 40 mg/day.


NAME: Lead

CLASSIFICATION: Heavy metal

DESCRIPTION: Lead is the fifth most utilized metal in the U.S. It is mined extensively in Missouri, Colorado, Idaho, and Utah and is used for the production of ammunition, bearing metals, brass materials, solder, ballasts, tubes, containers, gasoline products, ceramics, and weights (ATSDR 1993). Human exposure to lead occurs primarily through drinking water, airborne lead-containing particulates and lead-based paints. Several industrial processes create lead dust/fumes, resulting in its presence in the air. Mining, smelting and manufacturing processes, the burning of fossil fuels (especially lead-based gasoline) and municipal waste and incorrect removal of lead-based paint results in airborne lead concentrations. After lead is airborne for a period of ten days, it falls to the ground and becomes distributed in soils and water sources (fresh and salt water, surface and well water, and drinking water). However, the primary source of lead in drinking water is from lead-based plumbing materials (U.S. EPA, 1989). The corrosion of such materials will lead to increased concentrations of lead in municipal drinking water. Lead from water and airborne sources have been shown to accumulate in agricultural areas, leading to increased concentrations in agricultural produce and farm animals (ATSDR 1993). Cigarette smoke is also a significant source of lead exposure; people who smoke tobacco, or breath in tobacco smoke, may be exposed to higher levels of lead than people who are not exposed to cigarette smoke.

HEALTH PROBLEMS: Lead is absorbed into the body following inhalation or ingestion. Children absorb lead much more efficiently than adults do after exposure, and ingested lead is more readily absorbed in a fasting individual (U.S.EPA 1986). Over 90% of inhaled lead is absorbed directly into the blood. After lead is absorbed into the body, it circulates in the blood stream and distributes primarily in the soft tissues (kidneys, brain and muscle) and bone. Adults distribute about 95% of their total body lead to their bones, while children distribute about 73% of their total body lead to their bones (U.S. EPA, 1986a). Lead is one of the most toxic elements naturally occurring on Earth. High concentrations of lead can cause irreversible brain damage (encephalopathy), seizure, coma and death if not treated immediately (U.S. EPA, 1986). The Central Nervous System (CNS) becomes severely damaged at blood lead concentrations starting at 40mcg/dL, causing a reduction in nerve conduction velocities and neuritis (ATSDR 1993). Neuropsychological impairment has been shown to occur in individuals exposed to moderate levels of lead. Evidence suggests that lead may cause fatigue, irritability, information processing difficulties, memory problems, a reduction in sensory and motor reaction times, decision making impairment, and lapses in concentration (Ehle and McKee, 1990). At blood concentrations above 70 mcg/dL, lead has been shown to cause anemia, characterized by a reduction in hemoglobin levels, and erythropoiesis-- a shortened life span of red blood cells (Goyer, 1988; US EPA 1986a). In adults, lead is very detrimental to the cardiovascular system. Occupationally exposed individuals tend to have higher blood pressure than normal controls (Pocock et al., 1984; Harlan et al., 1985; Landis and Flegal, 1988), and are at an increased risk for cardiovascular disease, myocardial infarction, and stroke (US EPA, 1990). The kidneys are targets of lead toxicity and prone to impairment at moderate to high levels of lead concentrations. Kidney disease, both acute and chronic nephropathy, is a characteristic of lead toxicity (Goyer, 1988). Kidney impairment can be seen in morphological changes in the kidney epithelium, increases in the excretion rates of many different compounds, reductions in glomerular filtration rate, progressive glomerular, arterial, and arteriolar sclerosis, and an altered plasma albumin ratio (Goyer, 1985, 1988; Landigran, 1989). Chronic nephropathy has lead to increased death rates among occupationally exposed individuals as compared to controls in studies by Selevan et al. (1975) and Cooper et al. (1985). Other signs/symptoms of lead toxicity include gastrointestinal disturbances-abdominal pain, cramps, constipation, anorexia and weight loss-immunosuppression, and slight liver impairment (ATSDR, 1993; US EPA, 1986a). 


NAME: Magnesium

CLASSIFICATION: Alkaline Earth Metal

DESCRIPTIONS: Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the seventh most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole. This preponderance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Due to magnesium ion's high solubility in water, it is the third most abundant element dissolved in seawater. Magnesium is the 11th most abundant element by mass in the human body; its ions are essential to all living cells, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Hundreds of enzymes thus require magnesium ions to function. Magnesium is also the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers. Magnesium compounds are used medicinally as common laxatives, antacids (i.e., milk of magnesia), and in a number of situations where stabilization of abnormal nerve excitation and blood vessel spasm is required (i.e., to treat eclampsia). Magnesium ions are sour to the taste, and in low concentrations help to impart a natural tartness to fresh mineral waters. The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, is coated in a thin layer of oxide, which partly masks this reactivity). The free metal burns with a characteristic brilliant white light, making it a useful ingredient in flares. The metal is now mainly obtained by electrolysis of magnesium salts obtained from brine. Commercially, the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys, sometimes called "magnalium" or "magnelium". Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

HEALTH PROBLEMS: Excess magnesium in the blood is freely filtered at the kidneys, and for this reason it is difficult to overdose on magnesium from dietary sources alone. With supplements, overdose is possible, however, particularly in people with poor renal function; occasionally, with use of high cathartic doses of magnesium salts, severe hypermagnesemia has been reported to occur even without renal dysfunction. Alcoholism can produce a magnesium deficiency, which is easily reversed by oral or parenteral administration, depending on the degree of deficiency. 


NAME: Manganese

CLASSIFICATION: Alkaline Earth Metal

DESCRIPTION: Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals. As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels. Manganese phosphating is used as a treatment for rust and corrosion prevention on steel. Depending on their oxidation state, manganese ions have various colors and are used industrially as pigments. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Manganese dioxide is used as the cathode (electron acceptor) material in standard and alkaline disposable dry cells and batteries. Manganese (II) ions function as cofactors for a number of enzymes in higher organisms, where they are essential in detoxification of superoxide free radicals. The element is a required trace mineral for all known living organisms. In larger amounts, and apparently with far greater activity by inhalation, manganese can cause a poisoning syndrome in mammals, with neurological damage that is sometimes irreversible.

HEALTH PROBLEMS: Manganese compounds are less toxic than those of other widespread metals such as nickel and copper. However, exposure to manganese dusts and fumes should not exceed the ceiling value of 5 mg/m3 even for short periods because of its toxicity level. Manganese poisoning has been linked to impaired motor skills and cognitive disorders. The permanganate exhibits a higher toxicity than the manganese (II) compounds. The fatal dose is about 10 g, and several fatal intoxications have occurred. The strong oxidative effect leads to necrosis of the mucous membrane. For example, the esophagus is affected if the permanganate is swallowed. Only a limited amount is absorbed by the intestines, but this small amount shows severe effects on the kidneys and on the liver. In 2005, a study suggested a possible link between manganese inhalation and central nervous system toxicity in rats. It is hypothesized that long-term exposure to the naturally occurring manganese in shower water puts up to 8.7 million Americans at risk. A form of neurodegeneration similar to Parkinson's disease called "manganism" has been linked to manganese exposure amongst miners and smelters since the early 19th century. Allegations of inhalation-induced manganism have been made regarding the welding industry. Occupational Safety and Health Administration regulates Manganese exposure in US. According to results from a 2010 study, higher levels of exposure to manganese in drinking water are associated with increased intellectual impairment and reduced intelligence quotients in school-age children.


NAME: Mercury

CLASSIFICATION: Heavy Metal

DESCRIPTION: Mercury occurs primarily in two forms: organic mercury and inorganic mercury. Inorganic mercury occurs when elemental mercury is combined with chlorine, sulfur, or oxygen. Inorganic mercury and elemental mercury are both toxins that can produce a wide range of adverse health effects. Inorganic mercury is used in thermometers, barometers, dental fillings, batteries, electrical wiring and switches, fluorescent light bulbs, pesticides, fungicides, vaccines, paint, skin-tightening creams, vapors from spills, antiseptic creams, pharmaceutical drugs and ointments (ATSDR, 1989a). Inorganic mercury vapor is at high concentrations near chlorine-alkali plants, smelters, municipal incinerators and sewage treatment plants. The organic form occurs when mercury is combined with carbon. The most common form of organic mercury is methyl mercury, which is produced primarily by small organisms in water and soil when they are exposed to inorganic mercury. Humans also have the ability to convert inorganic mercury to an organic form once it has become absorbed into the bloodstream. Organic mercury is known to bioaccumulate -- or passes up the food chain due an organism's inability to process and eliminate it. It is found primarily in marine life (fish), and can often be found in produce and farm animals, processed grains and dairy products, and surface, salt-, and fresh water sources (ATSDR, 1989a; Brenner and Snyder, 1980). Occupational exposure to mercury containing compounds presents a significant health risk to individuals. Dentists, painters, fisherman, electricians, pharmaceutical/laboratories workers, farmers, factory workers, miners, chemists and beauticians are just some of the professions chronically exposed to mercury compounds.     The absorption and distribution of mercury compounds depends largely upon its chemical state. Organic mercury compounds are absorbed from the gastrointestinal tract more readily than inorganic mercury compounds, with the latter being very poorly absorbed. After absorption in the gastrointestinal tract, organic mercury is readily distributed throughout the body but tends to concentrate in the brain and kidneys (Goyer, 1991b). Approximately 80% of mercury vapor is absorbed directly through the lungs and distributed primarily to the CNS and the kidneys (Friberg and Nordberg, 1973). Inorganic and organic forms of mercury have also been seen in the red blood cells, liver, muscle tissue, and gall bladder (Peterson et al., 1991, Dutczak et al., 1991, ATSDR 1989a).     

HEALTH PROBLEMS: Mercury exposure can result in a wide variety of human health conditions. The degree of impairment and the clinical manifestations that accompany mercury exposure largely depend upon its chemical state and the route of exposure. While inorganic mercury compounds are considered less toxic than organic mercury compounds (primarily due to difficulties in absorption), inorganic mercury that is absorbed is readily converted to an organic form by physiological processes in the liver. The acute ingestion of inorganic mercury salts may cause gastrointestinal disorders such as abdominal pain, vomiting, diarrhea, and hemorrhage (ATSD 1989a). Repeated and prolonged exposure has resulted in severe disturbances in the central nervous system, gastrointestinal tract, kidneys, and liver. Daivs et al. (1974) reported dementia, colitis, and renal failure in individuals chronically poisoned due to the ingestion of an inorganic mercury containing laxative. Inhaled inorganic mercury can cause a wide range of clinical complications in individuals including corrosive bronchitis, interstitial pneumonitis, renal disorders, fatigue, insomnia, loss of memory, excitability, chest pains, impairment of pulmonary function and gingivitis (Goyer 1991b, ATSDR 1989a). 


NAME: Nickel

CLASSIFICATION: Heavy metal

DESCRIPTION: Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four elements that are ferromagnetic around room temperature, the other three being iron, cobalt and gadolinium. The use of nickel has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Norilsk in Russia. Pure nickel shows a significant chemical activity, but is slow to react at ambient conditions due to the formation of a protective oxide surface – similar to some other metals like chromium, aluminium and titanium. Because of this permanence in air and slow rate of oxidation, nickel is considered corrosion-resistant. Historically it has been used for plating metals such as iron and brass, for chemical apparatus, and in certain alloys such as German silver. About 6% of world nickel production is still used for corrosion-resistant pure-nickel plating. Nickel was a common component of coins, but is has largely been replaced by cheaper iron for this purpose, especially since the metal has proven to be an skin allergen for some people. Nickel is chiefly valuable in the modern world for the alloys it forms. About 60% of world production is used in nickel-steels (particularly stainless steel). Other common alloys, as well as some new superalloys, make up most of the remainder of world nickel use, with chemical uses for nickel compounds consuming less than 3% of production. As a compound, nickel has a number of niche chemical manufacturing uses, such as a catalyst for hydrogenation. Enzymes of some microorganisms and plants contain nickel as an active center, which makes the metal an essential nutrient for them.

HEALTH PROBLEMS: Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour workweek. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well. Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of the metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception; nickel carbonyl is also explosive in air. Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis. Sensitivity to nickel may also be present in patients with pompholyx. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for pierced ears. Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002, researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction. It was voted Allergen of the Year in 2008 by the American Contact Dermatitis Society. 


NAME: Zinc

CLASSIFICATION: Heavy metal

DESCRIPTION: Zinc also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in the Earth's crust and has five stable isotopes. The most exploited zinc ore is sphalerite, a zinc sulfide. The largest exploitable deposits are found in Australia, Asia, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning). Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC. Impure zinc metal was not produced in large scale until the 13th century in India, while the metal was unknown to Europe until the end of the 16th century. Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow". Paracelsus probably named the element after the German word Zinke. German chemist Andreas Sigismund Marggraf is normally given credit for discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of steel (hot-dip galvanizing) is the major application for zinc. Other applications are in batteries and alloys, such as brass. A variety of zinc compounds are commonly used, such as zinc carbonate and zinc gluconate (as dietary supplements), zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and zinc methyl or zinc diethyl in the organic laboratory. Zinc is an essential mineral of "exceptional biologic and public health importance". Zinc deficiency affects about two billion people in the developing world and is associated with many diseases. In children, it causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea, contributing to the death of about 800,000 children worldwide per year. Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans. Consumption of excess zinc can cause ataxia, lethargy and copper deficiency.

HEALTH PROBLEMS: Although zinc is an essential requirement for good health, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption. The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. The Free Ion Activity Model is well established in the literature, and shows that just micromolar amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all Daphnia in water. 
The free zinc ion is a powerful Lewis acid up to the point of being corrosive. Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to give corrosive zinc chloride. Swallowing a post-1982 American one cent piece (97.5% zinc) can cause damage to the stomach lining due to the high solubility of the zinc ion in the acidic stomach. There is evidence of induced copper deficiency at low intakes of 100–300 mg Zn/day; a recent trial had higher hospitalizations for urinary complications compared to placebo among elderly men taking 80 mg/day. The USDA RDA is 15 mg Zn/day. Even lower levels, closer to the RDA, may interfere with the utilization of copper and iron or adversely affect cholesterol. Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other essential metals, such as iron and manganese. There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide formed during the welding of  galvanized materials. The U.S. Food and Drug Administration (FDA) have stated that zinc damages nerve receptors in the nose, which can cause anosmia. Reports of anosmia were also observed in the 1930s when zinc preparations were used in a failed attempt to prevent polio infections. On June 16, 2009, the FDA said that consumers should stop using zinc-based intranasal cold products and ordered their removal from store shelves. The FDA said the loss of smell can be life-threatening because people with impaired smell cannot detect leaking gas or smoke and cannot tell if food has spoiled before they eat it. Recent research suggests that the topical antimicrobial zinc pyrithione is a potent heat shock response inducer that may impair genomic integrity with induction of PARP-dependent energy crisis in cultured human keratinocytes and melanocytes.