International Journal of Health Sciences and Research www.ijhsr.org ISSN: 2249-9571

Review Article


Shikha Bathla, Tanu Jain

Research Scholar, Department of Food and Nutrition, Punjab Agricultural University, Ludhiana-141004.

Corresponding Author: Shikha Bathla

Received: 15/02/2016 Revised: 13/04/2016 Accepted: 18/04/2016


A heavy is a member of a loosely defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some , , and . Many different definitions have been proposed based on , or atomic weight, and some on chemical properties. Heavy can result in damaged central nervous function, lower energy levels, and damage to composition, lungs, kidneys, , and other vital organs. Long- term exposure may result in slowly progressing physical, muscular, and neurological degenerative diseases. Exposure to toxic or heavy metals comes from many sources like in fish, chicken, vegetables, vaccinations, dental fillings and deodorants. Remedies to combat heavy metal toxicity can be to adopt the practice of kitchen gardening and also to ensure plethora supply of includes fruits and vegetables in the diet Increase intake of miso soup (made from soya) and garlic and regular exercise and brisk walking. Increase intake of to detoxify the harmful effect of heavy metals. Use of free paints and avoids carrying metal accessories.

Key words: heavy metals, lead, , , .

INTRODUCTION in body with ligands containing Metals occurrence in the (OH, -COO,-OPO3H, >C=O) sulphur (-SH, environment has become a concern because -S-S-), and (-NH and >NH) and the globe is experiencing a silent epidemic affect the body by interaction with essential of environmental poisoning, from the ever metals, formation of metal protein complex, increasing amounts of metals released into age and stage of development, lifestyle the biosphere. A heavy metal is a member factors, immune status of the host (Young of a loosely defined subset of elements that 2005; Nolan 2003; Duruibe et al 2007). exhibit metallic properties. Heavy metals Metal toxicity or metal poisoning is are those, which have specific gravity the toxic effect of certain metals in certain (density) of more than 5g/cm3 in their forms and doses on life. Some metals are standard state. It is not that every heavy toxic when they form poisonous soluble metal that is harmful to life. Living compounds. Certain metals have no organisms require varying amounts of biological role, i.e. are not essential "heavy metals”. , , , minerals, or are toxic when in a certain , , and are form. In the case of lead, any measurable required by humans. Excessive levels can be amount may have negative health effects damaging to the organism. Heavy metal (CDC 2012). exerts their toxic effect by combining with Indicators of environmental metal one or more reactive groups essential for the . Heavy metals are naturally normal physiological functions. They react occurring elements that are found International Journal of Health Sciences & Research (www.ijhsr.org) 361 Vol.6; Issue: 5; May 2016 throughout the ’s crust, most I. LEAD environmental contamination and human Global Perspective of Lead Poisoning: exposure result from anthropogenic Over 120 million people are overexposed to activities such as and lead all over the world and 99 percent of the operations, industrial production and use, most serious cases are in the developing and domestic and agricultural use of metals world and more than 51.3 per cent of and metal-containing compounds (He et al children in Indian metros below 12 years of 2005; Shallari et al 1998; Paul et al 2012). age have their blood lead levels above 10 Environmental contamination can also occur ug/dl. Lead poisoning (also known as through metal , atmospheric plumbism, colica Pictonum, saturnism, deposition, soil of metal ions and Devon colic, or painter's colic) is a medical of heavy metals, sediment re- condition in humans and other vertebrates suspension and metal evaporation from caused by increased levels of the heavy water resources to soil and ground water metal lead in the body (Venkatesh et al, (Nriagu 1989). Natural phenomena such as 2009) weathering and volcanic eruptions have also Routes of exposure to lead include been reported to significantly contribute to contaminated air, water, soil, food, and heavy metal pollution (Bradl et al 2002; consumer products. Occupational exposure Shallari et al 1998; Paul et al 2012). is a common cause of lead poisoning in Industrial sources include metal processing adults. According to estimates made by the in refineries, burning in power plants, National Institute of Occupational Safety petroleum combustion, nuclear power and Health (NIOSH), more than 3 million stations, and high tension lines, , workers in the United States are potentially textiles, microelectronics, wood exposed to lead in the workplace preservation, and paper processing plants (Staudinger 1998). The main threats of lead (Aruti et al 2010). toxicity to children is lead paint that exists Heavy metals: Any metal (or ) in homes and prevention of lead exposure species may be considered a “contaminant” can range from individual efforts (e.g. if it occurs where it is unwanted, or in a removing lead-containing items such as form or concentration that causes a piping or blinds from the home) to detrimental human or environmental effect. nationwide policies (e.g. laws that ban lead Metals/metalloids include lead (Pb), in products, reduce allowable levels in water (Cd), mercury (Hg), (As), or soil, or provide for cleanup and (Cr), copper (Cu), selenium (Se), mitigation of contaminated soil, etc.). (Ni), (Ag), and zinc (Zn). Other The increased lead in the body can less common metallic contaminants include be detected by the presence of changes in (Al), cesium (Cs), cobalt (Co), blood cells visible with a microscope and manganese (Mn), molybdenum (Mo), dense lines in the of children seen on (Sr), and (U) (Singh et al X-ray, but the main tool for diagnosis is 2011). Factors affecting the thresholds of measurement of the blood lead level. When dietary toxicity of heavy metal in soil-crop blood lead levels are recorded, the results system include the soil type, which includes indicate how much lead is circulating within soil pH, organic matter content, the blood stream, not the amount being and other soil chemical and biochemical stored in the body. The Centers for Disease properties; and crop species or cultivars Control (US) has set the standard elevated regulated by genetic basis for heavy metal blood lead level for adults to be 10 (µg/dl) transport and accumulation in plants and of the whole blood. For children the number hence, influencing the thresholds for is set much lower at 5 (µg/dl) of blood as of assessing dietary toxicity of heavy metals in 2012 down from a previous 10 the food chain (Ejaz et al 2007). (µg/dl).Children are especially prone to the

International Journal of Health Sciences & Research (www.ijhsr.org) 362 Vol.6; Issue: 5; May 2016 health effects of lead and as a result, blood the extremities. Fatigue, problems with lead levels must be set lower and closely sleep, headaches, stupor, slurred speech, and monitored if contamination is possible. The are also found in chronic lead major treatments are removal of the source poisoning (Pearce 2007, Brunton et al 2007, of lead by (CDC, 2012). Kosnett 2007, Patrick 2006, James et al Classification: The amount of lead in the 2005, Rambousek 2008). blood and tissues, as well as the time and Effects on children: Children are more at course of exposure, determine toxicity. Lead risk for lead poisoning because their smaller poisoning may be acute (from intense bodies are in a continuous state of growth exposure of short duration) or chronic (from and development. Lead is absorbed at a repeat low-level exposure over a prolonged faster rate compared to adults, which causes ), but the latter is much more more physical harm than to older people. common. The signs and symptoms are loss of Acute poisoning: In acute poisoning, appetite, abdominal pain, vomiting, weight typical neurological signs are pain, muscle loss, constipation, anemia, failure, weakness, paraesthesia and, rarely, irritability, lethargy, learning disabilities, symptoms associated with encephalitis and behavioral problems. Slow development (Pearce, 2007). Abdominal pain, nausea, of normal childhood behaviors, such as vomiting, diarrhea, and constipation are talking and use of words, and permanent other acute symptoms. Lead's effects on the mental retardation are both commonly seen mouth include astringency and a metallic (Cleveland et al, Meyer 2003, Bellinger et taste. Gastrointestinal problems, such as al 2008, Merrill et al 2007, Casarett et al constipation, diarrhea, poor appetite, or 2007). weight loss, are common in acute poisoning. Complications: Lead can affects all the Absorption of large amounts of lead over a body's organ but predominantly, the nervous short time can cause shock (insufficient system, then bones and teeth, kidneys, fluid in the circulatory system) due to loss cardiovascular and also reproductive of water from the gastrointestinal tract. system. Hearing loss and tooth decay are Hemolysis (the rupture of red blood cells) also the complications of lead poising. due to acute poisoning can cause anemia However, the health effects experienced by and hemoglobin in the urine. Damage to adults are similar to those in children, kidneys can cause changes in urination such although the thresholds are generally higher as decreased urine output. People who (White et al 2007, Lanphear et al 2007). survive acute poisoning often go on to Renal system: The toxic effect of lead display symptoms of chronic poisoning causes nephropathy and may cause Fanconi (Brunton, 2007). syndrome, in which the proximal tubular Chronic poisoning: Chronic poisoning function of the kidney is impaired (Rubin usually presents with symptoms affecting and Strayer 2008). Long-term exposure at multiple systems but is associated with three levels lower than those that cause lead main types of symptoms including nephropathy have also been reported as gastrointestinal, neuromuscular, and nephrotoxic in patients from developed neurological. Central nervous system and countries that had chronic kidney disease or neuromuscular symptoms usually result were at risk because of hypertension or from intense exposure, while diabetes mellitus (Eking et al 2006). Even gastrointestinal symptoms usually result lower levels of lead in the blood can also from exposure over longer periods. Signs of damage the kidneys (Grant 2009). chronic exposure include loss of short-term Cardiovascular system: Evidence suggests memory or concentration, depression, lead exposure is associated with high blood nausea, abdominal pain, loss of pressure, and studies have also found coordination, and numbness and tingling in connections between lead exposure and

International Journal of Health Sciences & Research (www.ijhsr.org) 363 Vol.6; Issue: 5; May 2016 coronary heart disease, heart rate variability, (more toxic) in fish. It can also be found in and death from stroke, but this evidence is thermometers, dental amalgams, fluorescent more limited (Navas-Acien et al 2007). light bulbs, disc batteries, electrical Reproductive system: Lead affects both , folk remedies, chemistry sets and the male and female reproductive systems. vaccines. In men, when blood lead levels exceed Health effects of mercury: It includes 40 μg/dL, sperm count is reduced and disruption of the nervous system, damage to changes occur in volume of sperm, their brain functions, DNA damage and motility, and their morphology (Grant chromosomal damage, allergic reactions, 2009). Elevated blood lead level in pregnant resulting in skin rashes, tiredness and woman's can lead to miscarriage, headaches and negative reproductive prematurity, low birth weight and also the effects, such as sperm damage, birth defects problems with development during and miscarriages (Horowitz et al 2002). childhood (Cleveland et al 2008). Lead is Elemental form of mercury: It is liquid at able to pass through the placenta and also room temperature that volatizes readily. It into the breast milk (Dart et al 2004). rapidly distributes in body by vapor. At high Nervous system: The brains of adults who concentrations, vapor inhalation produces were exposed to lead as children show acute necrotizing bronchitis, pneumonitis, decreased volume, especially in the and death and long term exposure affects prefrontal cortex, on MRI. Areas of volume CNS (ATSDR 1999). loss are shown in color over a template of a Inorganic form of mercury: It is poorly normal brain (Cecil et al 2008). Lead affects absorbed in GI tract, but can be caustic. the peripheral nervous system (especially Acrodynia (Pink disease) occurs usually motor nerves) and the central nervous from dermal exposure. Maculopapular rash, system. Lead causes the axons of nerve cells swollen and painful extremities, peripheral to degenerate and lose their myelin coats neuropathy, hypertension, and renal tubular (Dart et al 2004). Lead poisoning interferes dysfunction are some other effects with the normal development of a child's (Bjorklund 1995). brain and nervous system; therefore children Organic form of mercury: It is lipid are at greater risk of lead neurotoxicity than soluble and well absorbed via GI, lungs and adults (Sanders et al 2009). skin. It can cross placenta and into breast Prevention: Testing kits are commercially milk. Toxicity occurs with long term available for detecting lead that turned into exposure and effects the CNS. Signs red showed the presence of lead (Rossi 2008 progress from paresthesias to ataxia, and Sanborn et al 2002). In most cases, lead followed by generalized weakness, visual poisoning is preventable by avoiding and hearing impairment, tremor and muscle exposure to lead. Prevention strategies can spasticity, and then coma and death be divided into individual measures, (Clarkson and Magos 2006). preventive medicines and public health Diagnosis and Treatment: Diagnosis is measures (Guidotti and Ragain 2007). made by history and physical and lab II. MERCURY analysis. Inorganic mercury can be Mercury is a toxic substance, which has no measured by 24 hour urine collection; known function in human or organic mercury is measured by whole physiology and does not occur naturally in blood. The most important and effective living organism. It occurs in three forms treatment is to identify the source and end (elemental, inorganic salts, and organic the exposure. Chelating agents (DMSA) compounds). Mercury contamination results may enhance inorganic mercury elimination from mining, smelting, and industrial (Ibrahim et al 2006). discharges. Mercury in water can be Prevention: Roll onto a sheet of paper and converted by bacteria to organic mercury place in airtight container. Use of vacuum

International Journal of Health Sciences & Research (www.ijhsr.org) 364 Vol.6; Issue: 5; May 2016 cleaner should be avoided because it causes Distribution: The human body contains mercury to vaporize (unless it is a Hg Vac) approximately 7 grams of silicon, widely Consultation with environmental cleaning distributed in the tissues. High levels are company is advised with large spills. State present in , nails, tendons and the walls advisories on public limit or avoid of the aorta, with nails containing the consumption of certain fish from specific highest levels (up to 1500 mg/kg) and bodies of water (Mozaffarian and Rimm kidneys. Lower levels are present in red 2006). blood cells or serum (approximately 44 III. SELENIUM mg/kg for red cells and 20 mg/kg for bound Selenium (Greek- selene meaning silicic acid in plasma, in liver, spleen and "Moon") was discovered in 1817 by Jöns lung. Silicon is found in breast milk. Jacob Berzelius, who noted the similarity of : The absorption is facilitated the new element to the previously-known by aquaporins (a family of small (channel) (named for the Earth) by proteins present in the intracellular Berzelius, 1818. It is a with membranes, where they facilitate the properties that are intermediate between transport of water and/or small neutral those of its column-adjacent solutes like urea, boric acid, silicic acid). In elements and tellurium. It humans several aquaporins for OSA are rarely occurs in its elemental state in , identified. Average daily intakes of Si vary or as pure ore compounds. Dietary selenium between 13 and 62 mg/d. Mean Si intakes in comes from nuts, cereals, , , men (33 mg/d) are significantly higher than fish, and eggs. Brazil nuts are the richest in women (25 mg/d). Silicon intake ordinary dietary source (though this is soil- decreases with age. The dietary silicon dependent, since the Brazil nut does not intake is significantly correlated with require high levels of the element for its urinary silicon excretion. (Bowen and Peggs own needs). In descending order of 1984, Kayonga-Male and Jia 1999, concentration, high levels are also found in Pennington 1990, Takizawa et al 1988). kidney, tuna, crab, and lobster (Barclay et al Excretion: Silicon is predominantly and 1995 and Mutanen, 1986). rapidly excreted in the urine, with smaller Selenium Toxicity: Although selenium is amounts being eliminated in the feces .The an essential trace element, it is toxic if taken most sensitive test available to assess the in excess. Exceeding the Tolerable Upper reaction of white cells to silicon in the body Intake Level of 400 micrograms per day can is a lymphocyte chemical sensitivity lead to selenosis. Symptoms of selenosis (silicon) test. There is slow leakage include a garlic odor on the breath, (“bleeding”) of the silicone gel from the gastrointestinal disorders, and hair loss, implants through the semi-permeable sloughing of nails, fatigue, irritability, and membrane envelope and also into and neurological damage. Extreme cases of through the capsule that surrounds the selenosis can result in cirrhosis of the liver, implants. This is picked up by the pulmonary edema, and death (Public Health microphages (scavenger cells) of our Statement 2009). immune system and is broken down inside IV. SILICON these cells which travel all over the body. It is a non metallic element with an The gel breaks down inside these cells, atomic weight of 28. It is not found free in which travel all over the body. The gel nature. Highest occurrence is found in the breaks down into Silica and Silicon which oats (4250 mg/kg wet weight). Lower levels causes an immune system deregulation. are found in the animal sources. It is Thus, there are antibodies produced against distributed in various organs of human body the silicon and also against the silicon and as follows: protein complex (organ systems) so that you get autoimmune illness. As well, there is

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How to cite this article: Bathla S, Jain T. Heavy metals toxicity. Int J Health Sci Res. 2016; 6(5):361-368.


International Journal of Health Sciences & Research (www.ijhsr.org) 368 Vol.6; Issue: 5; May 2016