Arsenic: Sources, Transport and Distribution, and Health Effects - Term Paper Example

ARSENIC: SOURCES, TRANSPORT AND DISTRIBUTION, AND HEALTH EFFECTS Toxi of chemicals along with the effects on different organisms in the environment can be considered as one of the issues that requires the attention of the authorities and the public. The knowledge on the toxicity of chemicals can serve as a weapon against the effects of such materials. Included in the chemicals studied for its effects is Arsenic. Arsenic and Its Properties Arsenic, from the Greek work arsenikos, is a naturally occurring element within the Earth's crust. Represented in the periodic table by the symbol As with an atomic number of 33, arsenic occurs in three allotropic forms, yellow, black and grey. Its stable form is a silver-gray brittle crystalline solid that does not exhibit any characteristic smell or taste. Owing to its membership to the Va group of the periodic table, it readily combines with other elements to produce organic arsenic compounds (when in combination with carbon and hydrogen) and inorganic arsenic compounds (when in combination with oxygen, chlorine and sulfur) (Marcus, 2006; Nriagu, 1994). A. Arsenic in the Environment The occurrence of arsenic in the environment can be considered as an important notion in the study of the effects and toxicology. The name of Arsenic is equated to poison, due to the effects that it can bring about to the different organisms and components of the environment. The said chemical can be considered as toxic due to its reactivity. It occurs in different forms that are commonly reactive due to the fact that it is considered as a heavy metal but its use in different industries and the by-products produced intensifies the effects of arsenic (Marcus, 2006). Although natural arsenic can be found in certain amounts in the environment, accumulation increases the hazardous effect of the chemical. Effects of arsenic can be attributed to the exposure in relation to the industrial process and accumulated amounts in the environment. For this reason, it is important to consider the need to regulate the application of arsenic in different industries. B. Arsenic as Perceived by the Society Arsenic is widely regarded as a poisonous metalloid. It holds a notorious place in history for being the poison of choice used by nobles including the Italian family of the Borgias who used arsenic for political assassinations, and was regarded to be the poison that killed Napoleon, thus earning its moniker as the "Poison of Kings" (Nriagu, 1994). Aside from being an agent for murder, arsenic has largely been used as an ingredient in insecticides and herbicides. It has also been used in dyes, paints and other coloring agents including the green pigment Emerald Green which had been widely used by Impressionist painters and was thought to have caused Van Gogh's neurological disorder, Cezanne's diabetes and Monet's blindness. Currently, the arsenic compound gallium arsenide is used in the semiconductor industry to produce integrated circuits. Arsenic compounds are also used in the manufacture of glass and the smelting of copper and bronze. Chromated copper arsenate (CCA) is also used to preserve timber (Nriagu, 1994). Natural and Man-Made Sources of Environmental Arsenic Arsenic is naturally present in small concentrations in rock, soil, water and air arsenopyrite is among the 200 mineral species that arsenic is present. The chemical can be found prevalent in any types of environment, thus any exploitation in the use of the said chemical can cause imbalance. A. Atmospheric Arsenic One-third of the arsenic present in the atmosphere is from volcanic activity. The release of methylarsines by microorganisms also contributes to atmospheric arsenic. Inorganic arsenic compounds are also found in groundwater in countries like Bangladesh as a result of geologic activity. Organic arsenic compounds in the form of arsenobetaine and arsenocholine are found in marine organisms and a few terrestrial organisms (Brimblecombe, 1979). Atmospheric arsenic concentrations will range from 0.02 ng/m3 to 200 ng/m3 varying between rural and urban areas with the highest concentrations recorded in sites of industrial operations (Brimblecombe, 1979). Based on these results, the spread of arsenic suspended in the air can be considered of high possibility. The natural cycle of materials in the environment increases the dispersal rate thus affecting more organisms. B. Arsenic in Water Water bodies are also prevalent with arsenic sources. Pollution of arsenic compounds then can result to the abnormal accumulation in waters. The presence of such compounds can be attributed to the different activities on land such as mining, smelting, the proliferation of fossil fuel-powered industrial plants, use of arsenic-containing pesticides in agriculture, and the burning of CCA-treated timber are some of the man-made sources of environmental arsenic responsible for the contamination of air, water and soil (Anderson and Bruland, 1991; Neff, 1997: Reay, 1972). Arsenic in oceans are 1-2 mg/L, rivers and lakes 10 mg/L and in groundwater 1-2 mg/L (Ferguson and Gavis, 1972), and in sediments, from 5 to 3000 mg/kg. Arsenic compounds released to the environment through natural or anthropogenic means are then further dispersed through soil erosion, water runoff and windblown dust. Arsenic trioxide in the atmosphere eventually falls back to the earth due to its weight or rainfall. Volatile methylarsines released by microbes combine with oxygen in the atmosphere and are converted back into nonvolatile forms. Dissolved arsenic in the water column may take the form of "arsenate, arsenite, methylarsonic acid (MMA)" and dimethylarsinic acid (DMA) (Anderson and Bruland, 1991). Most arsenic compounds have the tendency to adsorb to soils and weathered rock thus leaching also becomes another mode of arsenic transport (Anderson and Bruland, 1991; Neff, 1997: Reay, 1972). Effects of Arsenic to Plants and Animals The study on the effects that can be attributed to arsenic can be need for vigilance to be able to prevent the further detrimental results due to accumulation of arsenic. Arsenic compounds can cause acute and chronic effects in aquatic and terrestrial biota including mortality, inhibition of growth, behavioral effects, reproduction and photosynthesis. These effects include both plants and animals inhabiting different types of ecosystems. Freshwater and terrestrial organisms exhibit arsenic concentrations less than 1 mg/kg while marine organisms naturally contain organic arsenic compounds in the range of 1 to 100 mg/kg (Neff, 1997). Terrestrial plants are capable of accumulating arsenic through root uptake and in areas of considerable arsenic contamination, some plants may contain up to 3000 mg/kg of arsenic (Reay, 1972). In 2003, Janssens, et. al. studied the effects of heavy metal exposure (As, Ag, Cd, Hg and Pb) on the health of great tit nestlings (Parus major) and found out that body mass and condition were significantly lower in nestlings located at the most polluted site. Nestlings from the polluted sites also fledged significantly later than other nestlings situated away from the polluted site. Erry et. al. (1999) also demonstrated that the amount of arsenic bioaccumulated by an organism was directly proportional to the level arsenic pollution of their habitat. Experimental laboratory studies have also confirmed that chronic exposure to arsenic through inhalation produced developmental defects (Nagymajtenyi et al., 1985), immunological suppression (Aranyi et al., 1985) as well as histological and biochemical effects on the nervous system (Itoh, et al., 1990). These correlated with symptoms observed in human arsenic exposure. Arsenic and Humans Being known as a poison even in the early part of history, exposure can be attributed to either intentional or accidental events. There is a variety of fields to be considered in the study of the effects of arsenic to humans. A. Exposure to Arsenic in the Environment Human exposure to arsenic is through the ingestion of food and water which ranges from 0.04-1.4 mg. Food is generally considered to be the principal source of human's arsenic intake although in areas of arsenic-contaminated groundwater, water may take its place. In an average 70 kg human, arsenic concentration is between 0.5 -15 mg. Table 1 summarizes the natural concentration of arsenic in the human body. Table 1. Arsenic Concentration in the Human Body Tissue Concentration Blood 0.0017-0.09 mg/dm3 Bone 0.08-1.6 ppm Liver 0.023-1.61 ppm Muscle 0.04-1.4 ppm B. Symptoms Acute exposure to inorganic arsenic compounds through accidental ingestion of high doses will lead to gastrointestinal symptoms and severe malfunctioning of the cardiovascular and respiratory system often leading to death. Chronic arsenic exposure in doses that are less than that of acute exposure will also cause adverse health effects. In 1993, Chatterjee, Das and Chakraborti investigated the high arsenic concentrations in the groundwater of Behala, Calcutta after a Paris Green factory dumped its industrial effluent in the area. Thousands of residents were hospitalized and symptoms of arsenic toxicity were evident in a large number of the population. Arsenic toxicity is often characterized by hyperkeratosis (Saha et al., 1999), exfoliative dermatitis and Mees' lines (white crescent moon marks on fingernails), sensory and motor polyneuritis (Blom, et. al., 1985). Peripheral vascular insufficiency resulting in blackfoot disease has also been noted by Tseng, et. al. in Taiwan in 1996. Occupational exposure to arsenic through inhalation in the case of smelter workers have demonstrated increased incidence in rhinopharyngolaryngitis, tracheobronchitis, nasal septum perforation and pulmonary insufficiency. Measurement of finger systolic pressure (FSP) also in smelter workers also revealed vasospastic tendency to be correlated with the duration of the workers' exposure to arsenic (Lagerkvist et al., 1986) Finally, chronic arsenic exposure has also been linked to cancer. In 2003, K.C. Saha investigated the clinical manifestations of arsenic toxicity in Bangladesh and West Bengal, considered as the "greatest arsenical calamity of the world". High levels of arsenic were found in nails, hair and skin scales of the patients. It took about 6 months to 10 years for a person to manifest symptoms of arsenic toxicity with melanosis as the earliest symptom. Soon thereafter, melanokeratosis sets in and malignancy often develops after 10 to 20 years in the form of skin cancer mostly squamous cell carcinoma. Aside from skin cancer, prolonged exposure to arsenic, either through inhalation, skin contact or ingestion of contaminated water, also increases the risk for lung and bladder cancer (Nriagu, 1994). In the case of lung cancer, arsenic plays an interactive role with tobacco smoking to promote lung malignancies (Hertz-Picciotto and Smith, 1993). C. Pertinent Data on the Effects of Arsenic The vigilance and the improvement on the knowledge regarding the effects of arsenic can be considered essential to be able to improve the statistics and the baseline information regarding the said chemical. Based on the studies conducted by the American Association of Poison Control Centers' (AAPCC) in its Toxic Exposure Surveillance System (TESS), in 2004 almost 1000 people were exposed in arsenic in causes other than pesticides which resulted in 2 deaths. In other parts of the world, the highest risks of arsenic exposure were recognized in the deposition in water bodies specifically drinking water which can directly affect the body (Marcus, 2006). Conclusion Based on the study conducted on the arsenic including its characteristics, distribution and effect to different organisms, the toxicity of the chemical has significant effects on health and survival of these organisms including human. 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