doi:10.5455/vetworld.2013.53-58 Arsenic: it's extent of pollution and toxicosis: An animal perspective 1

Arsenic poisoning is now considered as one of the biggest environmental disaster and a major public health issue. Incidence of arsenicpoisoning has been reported from many parts of the world. While Bangladesh and West Bengal (India) account for the most of the incidence, occasional reports from Mexico, Taiwan and mainland China have also appeared.It is a natural metalloid found in low concentrations in virtually every part of the environment as it is used in a wide variety of industrial applications, from computers to fireworks. Ground water arsenic is the major source of poisoning in animals and human. About 80% of ingested arsenic is absorbed and metabolized in liver and then excreted through urine and faeces while upon chronic exposure, it is deposited in liver, kidney and skin. Human populations are also being exposed to this poison by consuming the milk of affected animal.Inorganic forms of arsenic are more toxic compared to organic forms. Acute toxicity is rare in nature in comparison to chronic toxicity, which is prevalent in contaminated areas. Most non-ruminants are more susceptible to intoxication than ruminants. Chronic exposure of arsenic in animals and human beings causes severe adverse effects in the form of lowered immunity, diseases and production performances.


Introduction
vatives [6].It is considered as heavy metal due to its specific gravity higher than five (specific gravity Environmental pollution due to Arsenic (As) has =5.73).Its atomic number and atomic weight are 33 and gained global attention owing to its several deleterious 74.91, respectively.It can exist in four valency states; health effects on human and animal population.The -3, 0, +3, and +5.It occurs in particularly two forms i.e.Agency for Toxic substances and Disease Registry [1] organic and inorganic.Inorganic As is prevalent in two lists As among the top seven of 275 most hazardous forms i.e. trivalent and pentavalent.Trivalent forms are substances in the environment.This listing is based on As tri-oxide, As trichloride and arsenites, whereas toxicity of substance and the potential for its exposure pentavalent forms are As pentoxide, As acids and from air, water or soil contamination.
arsenate.Major organic compounds of As are basically Among the general public, the word "arsenic" has marine origin i.e. arsenosugars (macroalgae), arsenobecome almost synonymous with the word "poison" choline, arsenobetaine (invertebrates and fish) and [2].Indeed, Haas [3] has suggested that As has a fairly trimethylarsonium salts.In strongly reducing environlow toxicity in comparison with some of the other metals.
ments, elemental As and arsine (-3) can exist.Under Furthermore, As deprivation has been associated with moderately reducing conditions, arsenite (As (III)) is impaired growth and abnormal reproduction in rats, the dominant form; arsenate (As (V)) is generally the hamsters, chicks, goats, and miniature pigs [4].The stable form in oxygenated environments.Elemental As source of As in India's groundwater has eluded scientists for more than a decade after the toxin was is not soluble in water.Arsenic salts exhibit a wide discovered in the water supply of the Bengal delta [5].
range of solubility depending on pH and the ionic Due to chronic exposure of As human beings including environment.Water soluble arsenites and arsenates are animals are exposed to its adverse effects in the form of the most toxic, particularly trivalent form, while the lowered immunity, diseases and production performances.
elemental As is nontoxic, even if eaten in substantial The situation worsens if nutritional status of As exposed amounts [7].individual is also not optimum.
Taiwan [8].Several studies showed that As affected the feeds and fodders samples from different districts people in Bangladesh are 30-35 million [9].Serious of Haryana, which was in the normal range and far health hazards can be occurred due to As contaminated below the maximum dietary tolerable limit recommended drinking water use after a long period of about 5-15 by National Research Council (NRC, India) which is years, but the duration can be even 2-5 years for high 50 mg/kg DM for inorganic As and 100 mg/kg DM for exposure of contamination [10].Slow As poisoning organic As, thereby rendering the feeds fit for animal observed in scalp hair samples among the As consumption [22].contaminated water consumers [11].Safiuddin and

Sources of contamination in diet of animals
Karim [12] reported that the melanosis (93.5%) and Arsenic is present in more than 200 mineral species, keratosis (68.3%) are the most common sufferings the most common of which is arsenopyrite.There are among the As affected people in Bangladesh.
various sources of As.Arsenic appears in the earth's Thereafter, the seriously affected people are by crust at an average concentration of 2 to 5 mg/kg, with arsenical (arsenite and arsenate), resulting skin cancer low levels commonly found in the air, water, and soil of about 0.8 % of the total skin disease patients.[23].Ores are the most abundant source of As in nature.Livestock reared in and around such localities are Most commonly As bearing ores are Niceolite, Realger, also likely victims of such catastrophe arising from As Orpiment, Lobaltile, Arsenopyrite, Tennanites.Arsenic pollution.In Indian sub continent, the ground water is a major constituent of many minerals of the earth posses a major threat of exposing animals and human crust.Clays, phosphate rocks, sedimentary iron ores beings to toxic level of As in some geographical locations.
and coal are notably rich in As.The most common form Reports of As toxicity as an emerging epidemic of As is arsenite and arsenate compounds [24].It can be appeared in the newspapers in West Bengal in the early introduced to a groundwater system through various 1970s depicting the tale of people suffering from a means, including surface water and precipitation as peculiar disease, characterized by rain drip skin pigwell as anthropogenic and naturally occurring sources mentation, thickening and pricking sensation of palm [25,26].In addition to anthropogenic sources of As and feet tissues, excessive sweating, cirrhosis of liver contamination, human activity can aggravate and and cancer etc.
accelerate the release of naturally occurring As [27, The first report on As contamination of ground 28].Organic As compounds usually containing carbon water in West Bengal appeared in 1978.A report are mainly found in marine organisms.Industrial indicated that the flood prone areas of Ganga-Meghnaprocess, such as mining, smelting and coal-fired power Brahmaputra (GMB) covering an area of 5 lakh sq.km plants, found as another source of environmental As in Uttar Pradesh, Bihar, Jharkhand, West Bengal and [12,29,30].Agricultural pesticides and chemicals for Assam inhabiting 450 million people are prone to As timber preservation also play important roles in the poisoning [13].
presence of As [31,32].In 50 districts of Bangladesh and 9 districts of Ground water can be a major source of As, West Bengal, India found higher level of As in ground especially in the inorganic form.As concentration in water i.e. above WHO's recommended limit of 0.01 unpolluted fresh waters, mainly as arsenate, generally mg/L [14] and suffering of huge human population has ranges from1 to 10 µg/L.However, As content can be been reported.A recent survey was conducted on the As much higher in waters in some geochemical concentration of drinking water from deep wells in 64 environments.These include aquifers under strongly districts of Bangladesh and it was found that 54 districts were having As concentration more than 10 reducing condition, aquifers under oxidizing, high pH µg/Lt and 43 districts had more than 50 µg/Lt As (>8) condition, areas of sulphide mineralization and concentration [15].A few districts of Madhya Pradesh mining and geothermal areas [33].are reported to have As content of ground water up to In nature, As-bearing minerals undergo oxidation 800 ppb [16].As content in various water sources from and release As to water.This could be one explanation some industrial areas in Panipat, Yamunanagar and for the problems of As in the groundwater of West Sonepat was reported to be higher than the WHO Bengal and Bangladesh.In these areas, the ground permissible limits [17].In Punjab, Bathinda belt has water usage is very high.It has been estimated that been shown to have high As level in water [18].High there are about 4-10 million tube wells in Bangladesh level of As in ground water of Ballia region of U.P. was alone.The excessive withdrawal and lowering of the found [19]As level in 45 ground water samples water table for rice irrigation and other requirements collected from different areas of Delhi was in range of lead to the exposure and subsequent oxidation of As-0.0170 to 0.1000 ppm, which is more than WHO containing pyrite in the sediment.As the water table recommended value for As in drinking water (0.01 recharges after rainfall, As leaches out of the sediment ppm) [20].In the country except a few samples from into the aquifer.However, another studies seem to Faridabad industrial area, As content in all the water favour the reduction of Fe/As oxyhydroxides as the samples collected from all over Haryana was below source for As contamination in groundwater [34].maximum contamination level (MCL) of 10 ppb [21].
Sewage water from industries and households The same thing was also reflected in As content of all contain high amounts of heavy metals.When untreated sewage water is used for irrigation, there is a sharp animal milk and tissues.In milk the average value of As increase in the content of toxic elements in the soil.In was 0.08 ppm and 0.07 ppm in low As level villages 40 sewage irrigated vegetable farming locations of (LAL) and high As level villages (HAL), respectively.Punjab, the soil samples were found to contain As content in goat meat was 1.80 ppm (1.13 to 2.94 potentially toxic levels of As, Cr and Pb [35].Sewage ppb) and 0.13 ppm (0.00-0.In another study, it was reported that the As [37].Lead smelter contributes a great amount of As in content in cattle tail hair samples from As polluted area nature.Sea plants, fish products and supplemental was 0.22 to 1.22 ppm, whereas in As unpolluted area it minerals contribute towards most of the As found in was 0.10 to 0.73 ppm [43].As content of cattle hair animal feeds.The concentration of As has been found samples was 684.4 ppb, whereas in animals suppleto range between 1 and 180 mg/kg DM for various mented with 50 ppm As O contained three times 2 3 marine micro algae and it ranges from 2 to 170 mg/kg higher As in hair as compared to control [44].fresh weigh in marine fish and bivalves and between The maximum allowable concentration of As in 0.1 to 3 mg/kg fresh weight for fresh water fish [38]. drinking water were 0.05 ppm by WHO [45], which Gallium arsenate (GaAs) is also used as a doping was reduced to 0.01 ppm, WHO (14).However the agent for semiconductors.Furthermore, semicondulevel recommended by FAO [46] was 0.10 ppm.For ctors have been found to release As making them a cattle, sheep, swine and poultry, the maximum possible pathway for As contamination [39].
tolerable dietary As level is 50 mg/kg and 100 mg/kg Arsenic compounds are used in medicinal for inorganic and organic As, respectively [47].Critical preparation.Organic Arsenical compounds like acetarsol, level of As in animal feeds (both roughage and neoarsphenamine are used in the treatment of histoconcentrate) is reported to be 1.4 ppm, whereas for moniasis, Leishmaniasis, tryponosomiasis and sleeping milk the critical level is 50 ppb [40].sickness.Arsenical dips for sheep and cattle are usually

Metabolism of As
combined with sulphur and contain about 20 per cent of Inorganic As as well as its organic metabolites are soluble As and 3 per cent insoluble arsenious sulphide.
extensively absorbed (approximately 80%) and excreted As is essential constituent of many organic and in the urine.Accumulation of As in tissue is slow and inorganic coloring agents in dyeing.It is also used as occurs mainly in liver, kidney and skin.Withdrawal of discoloring agent in glass and enamel industry.The exposure led to a decrease in tissue contamination [48].effluent from these industries may contribute Asin The absorption and metabolism of As may be environment. influenced

by intestinal bacteria that can methylate As
As levels in milk and animal tissues and and metabolize methylated As [49].

recommended level of As
Once absorbed inorganic As is transferred to Based on limited data, it has been estimated that various tissues including the liver and testes, where it is the percentage of inorganic As is about 75% in meats methylated by S-adenosyl-methionine as a methyl and dairy products, and 65% in cereals.In As polluted donor to mono methyl arsonic acid [51].Before areas of West Bengal, high As level was reported in arsenate is methylated, it is reduced to arsenite.This reduction is facilitated by glutathione [52].As methyl pain, vomiting, diarrhea, marked depression and dermatitis usually due to increased capillary permeability and transferase, methylates arsenite to form mono methyl cellular necrosis.arsonic acid, which is then reduced to mono-methyl arsonous acid (Fig- 1).This is a toxic form of As, which Chronic toxicity is then rapidly methylated by a methyltransferase to Chronic toxicity of As is reported in animals from form dimethyl As acid.The formation of dimethyl As intoxicated areas.It is mostly manifested in weight arsenic acid usually is the final step of metabolism of loss, capricious appetite, conjunctivitis and mucosal As in most animals.
erythematic lesion including mouth ulceration and Excretion of ingested higher levels of As is rapid reduced milk yield.It is a cumulative poison having principally in the urine.However, high retention of As long retention time inside the body and therefore poses in the body was also been found in experimental group a threat on various physiological functions of the body. of crossbred calves given 50 ppm As (As O ) daily upto s 3 Animal exhibits signs of abdominal pain, hemorrhagic a period of 90 days in their diet.The amount of As diarrhea, salivation, vomiting, constipation, anorexia, retained in the control and experimental group were weight loss, dark urination and discrete skin eruptions 34.17% and 97%, respectively.The retention was [57].Liver and kidney are the primary target organs for further confirmed by increased levels of As in blood as toxic effects of As as evidenced by clinical maniwell as hairs [44].In some species, significant amounts festation and biochemical alterations [58].ATSDR [1] of As are reported to be excreted through the bile in also reported that chronic poisoning of As includes association with glutathione [52].
anemia, liver and kidney damage, hyperpigmentation Arsenic in addition to its excretion via urine and and keratosis.Symptoms in goat include abortion, skin faeces also secreted via milk.High As level was problems, white and black spot in the body, sometimes reported in animal milk and tissues from areas having diarrhea with blood, stunted growth, weakness, high As content [40] with increased morbidity in all anorexia, dark and cloudy urine [59].species of ruminants.Anke et al. [53] reported Chronic exposure to As, in addition to its general significantly lower As concentration in goat colostrum toxicity and its stimulation of many diseases, may compared to goat milk (from 0.01 to 0.024 mg/kg).
affect lymphocyte, monocyte and macrophage activity

Toxicosis of As
in many mammals, resulting in immunosuppression [60].Supplementation of As through drinking water Trivalent As (arsenite) is about 60 times more has been found to suppress the natural, humoral and toxic than pentavalent As (arsenate).Furthermore, cell mediated immune response in broiler chicks [61].inorganic As is about 100 times more toxic than organic As compound [54].Trivalent As is much more toxic Conclusions than pentavalent As compounds, which may be due in Arsenic, a metalloid, is ranked first in a list of 20 part to different rates of cellular uptake.Sodium hazardous substances by ATSDR and United States arsenite, which is more soluble than As (III) oxide, has Environmental Protection Agency.Exposures to As been shown to be ten times more toxic than As (III) large enough to cause acute toxic effects would be oxide.The toxicity of organic As compounds is easily recognized and the source of exposure would be inversely related to their degree of methylation.
found and eliminated.But the problem lies in the fact Inorganic forms are much more toxic than organic As that lowdoses of As that would be too low to cause [55].It may be surprising to some individuals that As overt acute toxicity, finally be recognized after a long has a low order of toxicity, especially when it is in the time with the development of toxic symptoms.This has pentavalent oxidation state.The lethal dose in domestic demanded a serious effort to trace all thepossible animals ranges from 1 to 25 mg/kg body weight as sources that cause human and animal exposure of this sodium arsenite, which is 3 to 10 fold more toxic than "king of poison".Finally, it is worth mentioning that As As trioxide [38].Trivalent arsenical compounds poisoning in humans and animals should not be combine with thiol group (SH) of lipoic acid moiety of considered a natural phenomenon, rather it is due to lipothiamide phosphate, an essential in oxidative wrong policy of uncontrolled industrialization and decarboxylation of pyruvic acid and α-ketoglutaric ignorance to develop an effective water management acid.Arsenic also appears to exert toxic action by of surface-water resources.attachment to sulphydryl groups of protein.