Arsenicals relative toxicity

Boron and arsenic are natural components of soil and are both present as oxyanions. Boron is present as boric acid or borate polymers, and arsenic is present as arsenate. While boron is weakly held by soil, arsenic is similar to phosphate in its interactions with soil constituents. Boron is an essential nutrient for plants however, it is also toxic to plants at relatively low levels. Arsenic is toxic. The laboratory chemistry of both of these elements is well understood, but their environmental chemistry, speciation and movement, is less well understood [23-27],... 

This review considers the literature of the past years (up to 1979) that treats the preconcentration of the priority pollution metals antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc. In some cases, a brief outline is given or some discussion of the method, but in most instances, the number of methods available precludes more than a mention of their specific application or special feature. For some elements such as mercury many methods of preconcentration are available, for others such as beryllium and thallium only a few are reported. Relatively few procedures actually detail the analysis of a sample containing several species both organic and inorganic, although this area is of major concern, because of large differences in the relative toxicity of the various species. 

For many years, arsenic has been regarded as an important environmental pollutant. It can enter the environment in many ways, for example use as an agrochemical, in smelting operations, and from coal fired power plants. Buchet and Lauwerys [70] list the relative toxicities for several arsenic compounds of high concern. In descending order they give arsine > arsenite > arsenate > methanearsonic acid (MMA) > dimethylarsinic acid (cacodylic acid, DMA). Methods which can accurately assess environmental and occupational exposure to these toxic arsenic compounds are necessary. 

Rotenoids. The use of rotenone-bearing roots as insecticides in the United States was developed as a result of federal laws against residues of lead, arsenic, and fluorine upon edible produce. Rotenone [83-79-4] (5) is harmless to plants, highly toxic to many insects, and relatively innocuous to... 

Heavy metals on or in vegetation and water have been and continue to be toxic to animals and fish. Arsenic and lead from smelters, molybdenum from steel plants, and mercury from chlorine-caustic plants are major offenders. Poisoning of aquatic life by mercury is relatively new, whereas the toxic effects of the other metals have been largely eliminated by proper control of industrial emissions. Gaseous (and particulate) fluorides have caused injury and damage to a wide variety of animals—domestic and wild—as well as to fish. Accidental effects resulting from insecticides and nerve gas have been reported. 

A mixture of dihydroxyacetone and inorganic arsenate can replace DHAP due to the transient formation of a monoarsenate ester which is recognized by the aldolase as a DHAP mimic21. This approach suffers from the high toxicity of arsenate, especially at the relatively high levels (>0.5 M) needed for efficient conversion, and from problems in product isolation. 

The term heavy metals is rather broad, relative, and nonspecific. There are many heavy metals. In industrial toxicology, however, the term is used to describe certain heavy metallic substances that can be distinguished from other metals because of their particular toxic effects. Of these, the most common are arsenic, lead, and mercury. These are the ones that will be dealt with here. 

The term heavy metal refers to any metallic chemical element that has a relatively high density (nsnally specific density of more than 5 g/mL) and is toxic or poisonous at low concentrations. Examples of heavy metals include arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), and thallium (Tl). The sources, uses, and environmental effects of several exemplary specific metals are discussed briefly here. 

The word bismuth is derived from the German word Weissmuth, or white substance. It is the heaviest stable element of the periodic table. Even though it carries the status of heavy metal, this metal is rated as relatively nontoxic and noncarcinogenic, unlike its neighboring elements (in the periodic table) like arsenic, antimony, lead, and tin, which are highly toxic. This nontoxicity arises from the insolubility of its salts in neutral aqueous solutions such as biological fluids, which... 

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. 

Lewisite is the most important of the organo-arseni-cal CW agents. Exposure to lewisite is quite painful, and onset of symptoms occurs rapidly (seconds to minutes) (31) in contrast to sulfur mustard for which a latency period occurs of several hours between exposure and symptoms (32). Although it is not known to have been used as a CW agent, lewisite is still considered a potential threat due to the relative ease of production and its rapid onset of action. Moreover, substantial stockpiles of lewisite are present in the United States, Russia, and in China abandoned by the Japanese Imperial Army. This may constitute a potential hazard for public health (33). The toxicity of lewisite is inter alia caused by the high affinity for the vicinal di-thiol system present in dihydrolipoic acid, a component of the pyruvate dehydrogenase complex, as is the case for other arsenicals (34). This prevents the formation of acetyl coenzyme A from pyruvate. 

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