Toxicological Effects of Arsenic and Fate of Arsenic - Term Paper Example

Toxicological Effects of Arsenic Physical and Chemical Properties of Arsenic Arsenic is known to exist in two allotropic forms. This means that the forms have different chemical and physical properties. The form of arsenic that is more common is brittle, shiny, gray and metallic like solid. The yellow crystalline solid is the less common. When arsenic is heated, it can change directly to vapor (gas), the process referred to as sublimation. However, at high temperatures of about 814oC, arsenic can be forced to melt. When heated in air, it combines with oxygen to form arsenic oxide. Arsenic rarely exists as a pure element. It normally exists as a compound. The most common arsenic ores are arsenopyrite, orpiment and real gar. These compounds are byproducts of purification and mining of silver metal (Edward, and Carol, 2011). It occurs in group five of the periodic table just below nitrogen and phosphorus. It is classified chemically as a metalloid, having both properties of a metal and non metal. Arsenic also occurs in crystalline metallic form which is a steel gray solid and in dark gray amorphous solid. It exists in one of the three oxidation states; -3, ÷3, and +5 (Edward, and Carol, 2011). These compounds can be classified as either inorganic or organic. Inorganic arsenic compounds are those without arsenic-carbon bond while organic arsenic compounds are those with an arsenic-carbon bond (Ecclestone, 2010). Uses of Arsenic Global production of arsenic is estimated to be 75,000 tons annually (NAS 1977; EPA 1980) of which almost 97% is used in the manufacture of arsenic trioxide and others are used to manufacture of special lead and copper alloys. Arsenic is used as homeopathic remedies used to cure patients with digestive problems, food poisoning, insomnia, allergies, anxiety, depression and obsessive-compulsive disorder. Arsenic compounds have been used in the manufacture of medicine since the time of Hippocrates (David, 2008); the production of herbicides, desiccants, wood preservatives, and the development of stimulants for plants and animals. Other smaller amounts are used in the manufacture of glass and textiles (Toropova et al., 2011). Importance of Arsenic in aquatic environment Arsenics are in constant change and is oxidized, reduced or metabolized and is used in plant uptake or reduction by organisms and chemical processes. These compounds have been used for a long time for the manufacture of medicines ranging from human medicine, plant medicine and also other aquatic organisms. High concentrations of arsenic in aquatic environment can slow down the growth of aquatic organisms such as fish and invertebrates. Arsenic is very vital in the aeration process of the water (David, 2008). Source of Arsenic compounds Arsenic occurs naturally as sulfides and as complex sulfides such as iron, nickel and cobalt. Arsenic is usually present in rocks, soils, water and living organisms at concentrations of parts per billion to parts per million (NAS 1977). Secondary iron oxides in mineralized zones that contain gold, silver and sulfides of lead and zinc.Natural weathering of rocks and soils adds approximately 40,000 tons of arsenic to the oceans every year and this accounts for Read More