Arsenic, Lead, and Cadmium

In contrast to inorganics such as mercury, copper, arsenic, lead, and cadmium, there have been fewer studies that focus only on zinc removal by carbonaceous adsorbents [199-203]. The presence of zinc in water appears to be due primarily to corrosion of galvanized metals [33]. The dominant oxidation state in aqueous solution is Zn(II), while the dominant species (see Fig. Al) are Zn at pH < 9 and Zn(OH), at pH > 9 [202]. 

Almela, C, M.J. Clemente, D. Velez, and R. Montoro. 2006. Total arsenic, inorganic arsenic, lead and cadmium contents in edible seaweed sold in Spain. Food Chem. Toxicol. 44(11) 1901-1908. Baker, D.H. 2004. Iodine toxicity and its amelioration. Exp. Bid. Med. 229(6) 473 78. 

Hazardous waste burning incinerators, cement kilns, and LWAKs do not follow a tiered approach to regulate the release of toxic metals into the atmosphere. The MACT rule finalized numerical emission standards for three categories of metals mercury, low-volatile metals (arsenic, beryllium, and chromium), and semivolatile metals (lead and cadmium). Units must meet emission standards for the amount of metals emitted. For example, a new cement kiln must meet an emission limit of 120pg/m3 of mercury, 54pg/m3 of low-volatile metals, and 180 pg/m3 of semivolatile metals. 

Several other chemicals are often included in different RSU or eco-labels. Examples of metals often included are lead, cadmium and arsenic. Head and cadmium may still be used as metal complex dyes but have in most cases been substituted. Metal complex dyes are often used to increase the fastness properties of leather, but metal complex dyes with lead and cadmium should be avoided. 

Occupational and environmental poisoning with metals, metalloids, and metal compounds is a major health problem. Exposure in the workplace is found in many industries, and exposure in the home and elsewhere in the nonoccupational environment is widespread. The classic metal poisons (arsenic, lead, and mercury) continue to be widely used. (Treatment of their toxicities is discussed in Chapter 57.) Occupational exposure and poisoning due to beryllium, cadmium, manganese, and uranium are relatively new occupational problems, which present new and previously unaddressed problems. 

The most abundant cation is potassium (2000-6500 ppm), accounting for approximately 70% by weight of total cationic content, followed by magnesium (400-1200 ppm), which accounts for approximately 14%i [120]. Calcium (400-1200 ppm) is found both in the lumen and in the pectin fraction, where it serves as a cross-linking agent, and accounts for approximately 14%) of the total cationic content. Sodium (100-300 ppm), iron (30-90 ppm), zinc (1-10 ppm), manganese (1-10 ppm), and copper (1-10 ppm) are also present in relatively small quantities. Lead and cadmium were not detected (Table 3.2). In untreated cotton, arsenic levels are usually less than 1 ppm [122,123]. Silicon, phosphorus, chlorine, sulfur, and boron are detected sometimes in trace amounts. 

Different metals and metal compounds have been in use since the beginning of human civilization. Metals include aluminum, antimony, cobalt, copper, chromium, iron, nickel, manganese, molybdenum, selenium, tin, vanadium, and zinc. The list of toxic metals includes but is not limited to arsenic, beryllium, cadmium, hexavalent chromium, lead, and mercury. Contamination of food, water, and the air by metals, particularly lead and cadmium, has caused global concern. Several studies have shown elevated levels of lead, nickel, chromium, and manganese in children s hair. 

Li, Y., Dhankher, O.P., Carreira, L., Lee, D., Chen, A., Schroeder, J.I., Balish, R.S., Meagher, R.B. (2004). Overexpression of phytochelatin synthase in Arabidopsis leads to enhanced arsenic tolerance and cadmium hypersensitivity. Plant Cell Physiol. 45 1787-97. 

The objective of this chapter is to put into perspective some of the current knowledge with respect to trace metals and their health implications. Potential adverse health effects of occupational exposures to trace metals are dis cussed cancer (arsenic, beryllium chromium nickel, and perhaps cadmium) chronic lung disease (beryllium and cadmium) neurologic and reproductive disorders (lead and mercury) and kidney disorders (lead and cadmium). Also discussed are the National Institute for Occupational Safety and Health (NIOSH) recommended standards for occupational exposure to several trace metals, the difficulty of establishing safe levels of exposure (particularly for carcinogens), and problems involved in identifying toxic components of trade name products. Special attention is given to the role of chemists to help protect the public health. 

Sodium Polythiocarbonate Solution (Thio-Red II). The analytical results from the precipitation tests conducted with Thio-Red II (Table II) show that when one equivalent of Thio-Red II was added for each equivalent of heavy metal present in the 10-34-0, only copper (>96%) and mercury (>95%) precipitated. Furthermore, only small amounts of lead (22%), arsenic (16%), and cadmium (9%) precipitated, while the levels of zinc (<7%), chromium (<1%), and manganese (<1%) in the 10-34-0 were essentially unaffected by addition of Thio-Red II. When a 50% excess of Thio-Red II was used, the amount of lead which precipitated increased to 83%, while the amounts of arsenic and cadmium which precipitated slightly increased to 34 and 36%, respectively. 

Mercury, copper, lead, and cadmium can be precipitated from 10-34-0 by adding TMT-15. The TMT-15 and Thio-Red II precipitated at least 94% of the copper and mercury present in the 10-34-0 manganese and chromium were not precipitated. The WI starch xanthate adsorbed mercury, copper, and lead from 10-34-0, while the adsorption of arsenic, cadmium, chromium, manganese, and zinc was negligible. 

Some trace metals are classified as toxic. There is, perhaps, justification for this classification for such metals as arsenic, lead, and mercury. In addition, extended exposure of mammals to small amounts of cadmium, lead, selenium, antimony, and nickel carbonyl can shorten life or cause cancer, and lead, nickel, antimony, cadmium, and mercury in small amounts cause human health problems. However, all metals are toxic if ingested at sufficiently high levels. Frequently, the effects of a toxic metal are increased by nutritional deficiencies. ... 

The data were generally in accordance with the lists of elements emitted in the course of technological processes applied by particular works. The main zinc ores used in Poland such as sphalerite, ZnS, and galman, ZnC03 + ZnSi04-H20 are almost always accompanied by lead and cadmium compounds, and very often by copper, arsenic and antimony (Jedrzejowski, 1987). Germanium and tin compounds occur as additional components of sulphidic zinc and lead ores. 

The elemental analyses were carried out at various laboratories with different analytical techniques. Copper and zinc were analyzed by ICP with a Varian Liberty 220 instrument at the Enel S.p.A. laboratories of Larderello (PI). Antimony, mercury and arsenic were determined in our laboratories with a Perkin-Elmer 5000 AAS equipped with FIAS using the hydride method. Lead and cadmium were analyzed at the Enel S.p.A. laboratories of Piacenza with a Perkin-Elmer Elan 5000 ICP-MS equipped with two mass flow controllers and a Perkin-Elmer Gem-Tip crossflow nebulizer. To enhance the sensitivity for cadmium, we also employed a CETAC U5000AT ultrasonic nebulizer (Cetac Technologies Inc., Omaha, NE) as an alternative introduction system to the pneumatic nebulizer. 

Heavy metals are natural constituents of rocks and soils. Following the industrialization, very big quantities of metals such as copper (Cu), mercury (Hg), cadmium (Cd), lead (Pb), nickel (Ni), zinc (Zn), chromium (Cr) and arsenic (As) have been released into the environment. Some industrial sources are still responsible for the contamination of water and soil. One of the main processes, which contribute to water pollution, is industrial extraction of cadmium, arsenic, lead and zinc. Among the fields of chemical industry, which also contribute towards the release of heavy metals, are metallization processes with cadmium and chromium, production of paints (zinc, cadmium), tannery (chromium), production of pesticides (copper) and fermentation (copper, zinc). ... 

A number of elements are naturally toxic. These include arsenic mercury heavy metals, such as lead and cadmium and the halogens fluorine, chlorine, bromine and iodine. Fluorine and chlorine are covered in Chapter 4 in the Poison Gas section. It is important to note the uses of elements, because they give an indication where these materials may be found in storage and manufacturing. 

For this reason, heavy metals and metal ions that are used as additives in plastics and rubber (as colorants, stabilisers, plasticisers and so on) should be monitored carefully, and their use as well as the amounts used should be well known and regulated. In addition to their existence in some of the additives used in plastics and rubbers, toxic heavy metals most of which are considered chronic poisons, such as arsenic, lead, mercury, cadmium, nickel, zinc and chromium, are frequently encountered in industrial processing and other manufacturing operations (their main industrial sources include paint, ink, plastic, rubber and plastic film production, leather tanning, wood preserving, battery manufacturing, and so on). 

For trace analysis, the main ceramic elements of interest are Zn, Pb, Cu, Bi, Sb, Sn, Ag, As, Mn, Cr, Se, and Hg. Many of these are environmentally important. In certain cases the detection limits of flame AAS are inadequate, so that hydride generation for antimony, selenium, arsenic and bismuth, cold vapor for mercury, and graphite furnace AAS for lead and cadmium are required. A variation of AAS is atomic fluorescence, and this is used to achieve the detection limits needed for Hg and Se in environmental samples. Microwave digestion techniques for sample preparation are becoming more common, where, unlike fusion, there is no risk of loss of volatile elements from unfired samples and fewer reagents are... 

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