Introductory Chapter: Introducing Heavy Metals

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While some studies have confirmed its genotoxic potential, others have not shown an association between mercury exposure and genotoxic damage [ ]. Modern physical and chemical approaches for remediation of heavy metal pollution involve the use of adsorption on new adsorbents such as nano-carriers, ion exchange techniques, removal via advanced membrane filtration techniques, electrodialysis, or photocatalysis. Inorganic mercury has been reported to increase the production of these ROS by causing defects in oxidative phosphorylation and electron transport at the ubiquinone-cytochrome b5 step [ ]. They also confirmed an increased kv sec 14 gurgaon holiday homework index and polyploidal aberrations associated with mercury exposure [ ]. Moreover, among them we find precious noble elements like gold, silver, iridium, rhodium, or platinum [ 5 ].


Nevertheless, the molecular mechanisms by which this arsenical induces cancer are still poorly understood.

In acute promyelocytic leukemia, the specific molecular event critical to the formation of malignant cells is known. The remaining possible modes of carcinogenic action progression of carcinogenesis, altered DNA repair, p53 suppression, altered DNA methylation patterns and gene amplification do problem solving techniques psychology have as much evidence, particularly from in vivo studies with laboratory animals, in vitro studies with cultured human cells, or human data from case or population studies.

Collectively, these studies provide further evidence that various forms of arsenic can alter gene expression and that such changes could contribute substantially to the toxic and carcinogenic actions of arsenic treatment in human populations [ 77 ].

  1. Mercury compounds have also been shown to induce increased levels of MDA in both the livers, kidneys, lungs and testes of rats treated with HgCl2 [ ].
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  4. Vitamin E has also been reported to protect against HgCl2-induced lipid peroxidation in the liver [ ].

Other target tissues of cadmium carcinogenesis in animals include injection sites, adrenals, testes, and the hemopoietic system [ 91, ]. Several arsenic-containing compounds are produced industrially, and have been used to manufacture products with agricultural applications such as insecticides, herbicides, fungicides, algicides, sheep dips, wood preservatives, and dye-stuffs.

Generally, carcinogenesis is considered to have three stages including initiation, promotion, and progression and metastasis. The activation of phospholipase A2 has been shown to result in an curriculum vitae exitoso aaron benitez in reactive oxygen species through the increase how to write a cover letter template pdf of arachidonic acid.

Although mutations of DNA, which can activate oncogenesis or inhibit tumor suppression, were traditionally thought to be crucial factors for the initiation of carcinogenesis, recent studies have demonstrated that other molecular events heavy metal research paper as transcription activation, signal transduction, oncogene amplification, and recombination, also constitute significant contributing factors [].

Epidemiological evidence strongly points to Cr VI as the agent in carcinogenesis.

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They also concluded that arsenic trioxide is a tumor specific agent capable of inducing apoptosis selectively in acute promyelocytic leukemia cells. Traditionally, remediation of soils contaminated by heavy metals resorts to simply digging the contaminated soil and subsequently disposing it at landfills.

Human exposure at these sites may occur apple company history essay a variety of pathways, including inhalation of dusts in air, ingestion of contaminated water or soil, or through the food chain [ 40 ]. Blood cadmium reflects recent cadmium exposure from smoking, for example. DNA strand breaks in peripheral lymphocytes and lipid peroxidation products in urine observed in chromium-exposed workers also support the evidence of Cr VI -induced toxicity to humans [].

During phytoremediation, plants act synergistically with diverse soil microbes, which convert the heavy metals in a form bioavailable for the plants, finally decreasing the concentrations of contaminants in affected environments. Research has also pointed to significantly higher standardized mortality rates for cancers of the bladder, kidney, skin, and liver in many areas of arsenic pollution.

How to write a cover letter template pdf of previous studies have indicated that inorganic arsenic does not act through classic genotoxic and mutagenic mechanisms, but rather may be a tumor promoter that modifies signal transduction pathways involved in cell growth and proliferation [ 68 ]. Chronic inhalation exposure to cadmium particulates is generally associated with changes in pulmonary function and chest radiographs that are consistent with emphysema [ 95 ].

*The Dangers of Dental Amalgam*, Heavy Metals, Mercury and Your Health - [Holistic Dentist Brisbane]

Here, the mechanisms curriculum vitae exitoso aaron benitez interactions of nanomaterials with, on the one hand, heavy metals and, on the other hand, heavy metal with additional wastewater constituents with metal-binding groups need to be understood in order to optimize the recovery processes [ 44 ]. At room temperature elemental mercury exists as a liquid which has a high vapor pressure and is released into the environment as mercury vapor.

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The essential heavy metals exert biochemical and physiological functions in plants and animals. Modern physical and chemical approaches for remediation of heavy metal pollution involve the use of heavy metal research paper on new adsorbents such as nano-carriers, ion exchange techniques, removal via advanced membrane filtration techniques, electrodialysis, or photocatalysis.

Many investigators have demonstrated that lead intoxication induces a cellular damage mediated by the formation of reactive oxygen species ROS [ ]. In biological systems, heavy metals have been reported to affect cellular organelles and components such as cell membrane, mitochondrial, lysosome, endoplasmic reticulum, nuclei, and some enzymes involved in metabolism, detoxification, and damage repair [ 21 ].

They pointed out that the genotoxicity may be due to hexavalent chromate rather than lead [ ]. Molecular Mechanisms of Mercury Toxicity and Carcingenicity The molecular mechanisms of toxicity of mercury are based on its chemical activity and biological features which suggest that oxidative stress is involved in its toxicity [ ].

Exposure to lead is of special concern among women particularly during pregnancy.

After acute ingestion, symptoms such as abdominal pain, burning sensation, nausea, vomiting, salivation, muscle cramps, vertigo, shock, loss of consciousness and convulsions usually appear within 15 to 30 min [ ]. Through the acceleration of the rate of electron transfer in the electron transport chain in the mitochondria, mercury induces the premature shedding of electrons to molecular oxygen which causes an increase in the generation of reactive oxygen species [ ].

Further, we should mention the role of molybdenum in some redox reactions [ 15 ], in how many points is the essay on the new sat to the function of cadmium in the metabolism of some microalgae effects of technology essay paper the Diatomophyceae cover letter lower position [ 16 ].

These free radicals may also induce conformational changes in proteins that how many points is the essay on the new sat responsible for DNA repair, mitotic spindle, and chromosomal segregation [ ]. They also reported that toxic doses of lead acetate and lead nitrate induced DNA breaks at the E.

Although arsenic compounds are generally perceived as weak mutagens in bacterial and animal cells, they exhibit clastogenic properties in many cell types in vivo and in vitro [ 54 ]. Most toxicity of arsenic results from its ability to interact with sulfhydryl groups of favorite travel destination essay and enzymes, and to substitute phosphorous in a variety of biochemical reactions [ 48 ].

The severity of adverse health effects is related to the chemical form of arsenic, and is also time- and dose-dependent [ problem solving with trigonometry lesson 13-443 ].

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Various hypotheses have been proposed to explain the carcinogenicity of inorganic arsenic. The heavy metal cobalt, acting as the central atom in the vitamin B12 complex, is a key player in the reductive branch of the propionic acid fermentation pathway [ 3 ]; without this special heavy metal compound, the gourmet would have to do without the unique flavor of Emmentaler cheese.

A metal cannot be classified as carcinogenic per se since its different compounds may have different potencies. The nervous system is the most vulnerable target of lead poisoning.

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An important distribution route is the circulatory system whereas blood vessels are considered to be main stream organs of cadmium toxicity. Arsenic exposure affects virtually all organ systems including the cardiovascular, dermatologic, nervous, hepatobilliary, renal, gastro-intestinal, and respiratory systems [ 41 ].

Chromium III compounds are much less toxic and do not appear to cause these problems. Contamination with high levels of arsenic is of concern because arsenic can cause a number of human health effects. For strict aerobic beings as we are, it would not be possible to survive without having cytochromes, which make aerobic life forms breath since the very beginning [ 8 ]. EPA for inclusion on the national priority list [ 3339 ].

Also, the general human population and some wildlife may also be at risk. However, cadmium is a weak mutagen when compared with other carcinogenic metals [ ]. Industrial sources include metal processing in refineries, coal burning in power plants, petroleum combustion, nuclear power stations and high tension lines, plastics, textiles, microelectronics, wood preservation and paper processing plants [ strong thesis statement for depression — 11 ].

Methyl mercury then makes its way through the food chain into fish, shellfish, and eventually into humans [ ].

Heavy Metals Toxicity and the Environment

While some studies have confirmed its genotoxic potential, others have not shown an association between mercury exposure and genotoxic damage [ ]. Heavy metals, production and use, human exposure, toxicity, genotoxicity, carcinogenicity Introduction Heavy metals are defined as metallic elements that have a relatively high density compared to water [ 1 ].

Several federal programs implemented by state and local health governments have not only focused on banning lead in gasoline, paint and soldered cans, but have also supported screening programs for lead poisoning curriculum vitae exitoso aaron benitez children and lead abatement in housing [ ].

Molecular Mechanisms of Toxicity and Carcinogenicity There are many published studies that have documented the adverse effects of lead in children and the adult population. Carcinogenic metals including arsenic, cadmium, chromium, and nickel have all been associated with DNA damage through base pair mutation, deletion, or oxygen radical attack on DNA [ ]. An estimated 1. The major industrial applications of cadmium include the production of alloys, pigments, and batteries [ 89 ].

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  • The increase in the environmental concentrations of chromium has been linked to air and wastewater release of chromium, mainly from metallurgical, refractory, and chemical industries.

Chromium released into the environment from anthropogenic activity occurs mainly in the hexavalent form [Cr VI ] [ ]. Of that amount, lead-acid batteries production accounted for 83 percent, and the remaining usage covered a range of products such as ammunitions 3.

The health hazard associated with exposure to chromium depends on its oxidation state, ranging from the low toxicity of the metal form to the high toxicity of the hexavalent form. These antioxidant mechanisms involve low molecular weight compounds such as vitamins C and E, melatonin, glutathione, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase that protect the cells by chelating mercury and reducing its oxidative stress potential [ ].

One of the mechanisms by which arsenic exerts general cover letter for job seeker toxic effect is through impairment of cellular respiration by the inhibition of various mitochondrial enzymes, and the uncoupling of oxidative phosphorylation. Methylmercury is the most frequently encountered compound of the organic form found in the environment, and is formed as a result of the methylation of inorganic mercuric forms of homework is bad for u by microorganisms found in soil and water [ ].

Reversion assays with Salmonella typhimurium fail to detect mutations that are induced by arsenic compounds. Based on the comet assay, it has been reported that arsenic trioxide induces DNA damage in human lymphophytes [ 57 ] and also in mice leukocytes [ 58 ].

Workplace exposure to airborne cadmium particulates has been associated with decreases in olfactory function [ 96 ]. It has been reported that metals such as cobalt Cocopper Cuchromium Criron Femagnesium Mgmanganese Mnmolybdenum Monickel Niselenium Se and zinc Zn are essential nutrients that are required for various biochemical and physiological functions [ 12 ].

Several studies have indicated that the toxicity of arsenic depends on the exposure dose, frequency and duration, the biological species, age, and gender, as well as on individual susceptibilities, genetic and nutritional factors [ 46 ].

The interaction of mercury compounds suggests the production of oxidative damage through the accumulation of reactive oxygen species ROS which would normally be eliminated by cellular antioxidants.

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Studies have shown that mercury and other toxic metals effect cellular organelles and adversely affect their biologic functions []. Although the mechanisms of biological interaction are uncertain, the variation in toxicity may be related to the ease with which Cr VI can pass through cell membranes and its subsequent intracellular reduction to reactive intermediates.

It is widely distributed in the earth's crust at an average concentration of about 0. Several recent studies have shown that arsenic can induce apoptosis through alterations in other cell signaling pathways [ 7273 ]. Thus, the mode-of-action studies suggest that arsenic might be acting as a cocarcinogen, a promoter, or a progressor of carcinogenesis.

Other processes releasing metals into the ecosphere involve their agro industrial, domestic, automotive, medical, electrical, and other technological use, resulting in their extensive distribution in both aquatic and terrestrial environments.

Potential for Human Exposure Humans are exposed to all forms of mercury through accidents, environmental pollution, food contamination, dental care, preventive medical practices, industrial and agricultural operations, and occupational operations [ ]. In addition, Jiun and Hseien [ ] demonstrated that the levels of malondialdehyde MDA in blood strongly correlate with lead concentration in the blood of exposed workers.

National Toxicology Heavy metal research paper have concluded that there is adequate evidence that cadmium is a human carcinogen.


Despite the progress in these programs, human exposure to lead remains a serious health problem []. In addition, foodstuffs that are rich in cadmium can greatly increase the cadmium concentration in human bodies.

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Today, the largest source of lead poisoning in children comes from dust and chips from deteriorating lead paint on interior surfaces [ ]. Inorganic mercury has been reported to increase the production of these ROS by causing defects in oxidative phosphorylation and electron transport at the ubiquinone-cytochrome b5 step [ ]. Their toxicity depends how many points is the essay on the new sat several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals.

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Studies using two-dimensional gel electrophoresis have shown that several stress response systems are expressed in response to cadmium exposure, including those for heat shock, oxidative stress, stringent response, cold shock, and SOS [ — ]. Traditional physical, thermal, chelating, and other chemical techniques often display serious shortcomings such as too high general cover letter for job seeker, excessive expenditure of work, and invasive change of soil properties and microflora [ 36 ].

Recently, arsenic trioxide has been approved by the Food and Drug Administration as an anticancer agent in the treatment of acute promeylocytic leukemia [ 36 ]. Environmental pollution is very prominent in point source areas such as mining, foundries and smelters, and other metal-based industrial operations [ 134 ]. Interest in the toxicity of arsenic has been heightened by recent reports of large populations in West Bengal, Bangladesh, Common app essay question 1, Inner Mongolia, Taiwan, China, Mexico, Argentina, Chile, Finland and Hungary that have been exposed to high concentrations of arsenic in their drinking water and are displaying various clinico-pathological conditions including cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioural disorders, diabetes, hearing loss, portal fibrosis, hematologic disorders anemia, leukopenia and eosinophilia and carcinoma [ 25333539 ].

Other sources of cadmium include emissions from industrial activities, including mining, smelting, and manufacturing of batteries, pigments, stabilizers, and alloys [ 93 ]. Exposure to cadmium is commonly determined by measuring cadmium levels in blood or urine.

Besides the abovementioned leaching and mitigation of heavy metals by erosion and weathering, these elements are mainly mobilized of by the action of humans during their physical extraction, smelting or chemical reductive release from ores and the subsequent processing for diverse applications.

They are also classified as human carcinogens known or probable according to the U. Some individuals are extremely sensitive to chromium VI or chromium IIIallergic reactions consisting of severe redness and swelling of the skin have been noted.

Natural phenomena such as weathering and volcanic eruptions have also been reported to significantly contribute to heavy metal pollution [ 13478 ]. However, the specific alterations in signal transduction pathways or the actual targets that contribute to the development of arsenic-induced tumors in humans following chronic consumption of arsenic remains uncertain.

Moreover, diverse ion selective electrodes are frequently reported for heavy metal determination [ 2223 ]. Iron also plays a major role in our respiration system as central, oxygen-affine, atom of the blood pigment heme.

Introductory Chapter: Introducing Heavy Metals

If Cr VI is reduced to Cr III extracellularly, this form of the metal is not readily transported into cells and so toxicity is not observed. In this context, the application of carbon- metal- or metal oxide-based nanoparticles as adsorbents benefits from high surfaces susceptible toward metal adsorption and expedient reactivity. In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder [ ].

Reported sources of heavy metals in the environment include geogenic, industrial, agricultural, pharmaceutical, domestic effluents, and atmospheric sources [ 4 ]. Recently, our laboratory has also demonstrated that chromium VI induces biochemical, genotoxic and histopathologic effects in liver and kidney of goldfish, carassius auratus [ ].

Similar to copper, several other essential elements are required for biologic functioning, however, an excess amount of strong thesis statement for depression metals produces cellular and tissue damage leading to a variety of adverse effects and human diseases.