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Summer Research Fellowship Programme of India's Science Academies

ARSENIC IN GROUNDWATER: SOURCES AND ITS IMPACTS ON THE HUMAN BODY. A REVIEW.

SANGEETA SUBHADARSHINI

Department of Geology, Ravenshaw University, Cuttack

Guided by:

DR. NRIPEN CHANDA

CSIR - CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, DURGAPUR, WEST BENGAL

ABSTRACT

Arsenic contamination of groundwater in different parts of the world is an outcome of natural and/or anthropogenic sources, leading to adverse effects on human health and ecosystem. Millions of people from different countries are heavily dependent on groundwater containing elevated level of As for drinking purposes. As contamination of groundwater poses a serious risk to human health. Excessive and prolonged exposure to inorganic As with drinking water is causing arsenicosis, a deteriorating and disabling disease characterized by skin lesions and pigmentation of the skin, patches in the palm of the hands and soles of the feet. Arsenic poisoning culminates into potentially fatal diseases like skin and internal cancers. This paper reviews sources, speciation, and mobility of As and presents a global overview of groundwater As contamination. The paper also critically reviews As-led human health risks, its uptake, metabolism, and toxicity mechanisms. The paper provides an overview of the state-of-the-art of knowledge on the alternative to As-free drinking water and various technologies (oxidation, coagulation flocculation, adsorption, and microbial) for mitigation of the problem of As contamination of groundwater.

Keywords: Arsenic, Sources, Groundwater Contamination, Health Impacts

INTRODUCTION

 Arsenic contamination of groundwater has been identified in various parts of the world. Regardless of localized inputs of arsenic from human activities, much of the contamination of groundwater by arsenic was shown to arise from geogenic sources which affected groundwater in many countries. Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment. On land, rocks which are exposed to certain geological and geothermal activities can contribute to major sources of arsenic deposits if they are rich in minerals containing arsenic like Realgar (As4S4), Arsenopyrite (FeAsS), Anargite (Cu3AsS4) and Orpiment. The major cause of contamination of arsenic in groundwater is the mobilization of natural arsenic on sediments. If the minerals are subjected to the right chemical conditions under the ground, the arsenic content in them can dissolve in the surrounding groundwater accumulation. The main anthropogenic sources for contamination of groundwater with arsenic are mining, burning of fossil fuels, use of arsenical fungicides, herbicides and insecticides in agriculture and wood preservatives. The degree of groundwater arsenic contamination by anthropogenic sources is much less compared to the natural sources; however, their contribution cannot be neglected. In the United States, the arsenic contents have been reported to be sourcing from geogenic sources like up-flow of geothermal water, dissolution of or desorption from iron oxide, and dissolution of sulphide minerals; and also, from anthropogenic sources such as copper smelting. The source of arsenic in India is geogenic as well as anthropogenic. Arsenic is present in the alluvial sediments of the Delta; and the chemical industries along with mining contribute to the anthropogenic causes of arsenic in groundwater. The presence of arsenic in groundwater exceeding the standard limits set by the government and its toxicology pose serious health concerns. The severity of the problem is alarmingly high. Its long-term exposures are fatal. Arsenic poisoning immediately causes vomiting, abdominal pain, and diarrhoea which might be followed by muscle cramping, numbness and at times death. The long-term exposures can be indicated by pigmentations on skin, hyperkeratosis and skin lesions which might prove to be early signs of skin cancer. Along with skin cancer, there may be developmental effects, diabetes, pulmonary and cardiovascular disease.

The report shall focus on the sources of arsenic in groundwater and its health impacts on the human body.

ARSENIC AND ITS GEOCHEMISTRY

Arsenic is a trace element found in the environment which ranks 52nd in the abundance of elements in the crust with an average crustal concentration coming up to 1.8 mg/kg (Lide 1994). It comes from the arsenic minerals that are present on the earth's surface. These minerals are the primary sources of arsenic apart from other various sources that it comes from. It is found in the crystal lattices of these minerals.

The distribution of this element depends gravely upon the biogeochemical transformations which comprise pH, adsorption-desorption, redox conditions, availability of ions, dissolution and various biological activities. (https://www.omicsonline.org/open-access/arsenic-occurrence-and-fate-in-the-environment-a-geochemical-perspective-2157-7617-1000269.php?aid=51452 )

Since various sources of arsenic are present on the earth's surface, this element can be found in soil, water, air, rocks and living bodies. It continuously cycles through different forms and combinations. (https://www.opb.org/news/article/oregon-arsenic-discovery-could-lead-to-cleaner-drinking-water-/). Volcanic eruption is one of the most significant natural activities responsible for the release of arsenic into the atmosphere. Being widely found in more than 300 minerals, the most common and abundant ones still remain to be Pyrite, Arsenopyrite, Realgar and Orpiment. (U.S. EPA 2002; Mandal et al 1998; Acharyya et al 1999; Nickson et al 1998; Nickson et al 2000; Kumaresan and Riyazuddin 2001). Arsenic is closely associated with ores of metal sulphides because it has chemical similarities with sulphur which support the isomorphous replacement between the lattices of arsenic and sulphur. ​(McCarty 2011).

If the surrounding conditions are typically suitable for the formation of soil, there would exist several factors on which the nature of arsenic in the soil shall depend on; they are lithology of the protoliths, biological factors, transportation, precipitation, weathering profile, sorption and volcanic activity, if any (Kabata-Pendias and Adriano 1995). ​

In geothermal reservoirs that are deep seated, leaching helps the release of arsenic which are brought to sub-surface level by the uprising activity of the geothermal fluids. At high temperatures, arsenic occurs in Arsenopyrite (FeAsS) or simply arsenic bearing pyrite. ​Bundschuh​ These minerals dissolved in geothermal fluids, after reaching the subsurface zone, get adsorbed to the sediments when in excess. Later on these sediments work as source for arsenic when the concentration of iron decreases in the surrounding waters. (Cornett et al 1992, Bright et al. 1994) When these sediments weather, they release bivalent Fe in an oxidising environment, which sorbs the co-weathered arsenic. The iron oxyhydroxide rocks adsorb arsenic released from these sediments. Redox processes in these rocks trigger the reductive dissolution of iron oxides into the surrounding aqueous phases along with a substantial amount of arsenic through different biogeochemical processes ​(​Singh 2006​).

Microbes also promote arsenic concentration in fluids by oxidation or reduction to produce As (V) and As(III) respectively. Low pH promotes the concentration of the aqueous species H2AsO4- under oxidising conditions and high pH will promote HAsO42- under the same conditions. Under reducing conditions, arsenite dominates in the form H3AsO30 (Kinniburgh et al 2003).

Arsenic geochemistry is a result of various biogeochemical factors that in turn depend on the primary source of arsenic, pH and various microbial activities. 

ARSENIC IN GROUNDWATER - A MENACE

Arsenic in groundwater has been a very serious issue since the last few decades when it was discovered and its ill effects were reported. The element has very significant toxicity and causes major health concerns. The metal, when it combines with other elements in the environment, becomes very difficult to detect (Chowdhury et al 2000). Though the concentration of arsenic in soils is very low at most of the places, at some places it is exceptionally high. Also, weathering, erosion and deposition are factors responsible for this contamination. The chemistry of groundwater is dependent upon the geochemistry of the source aquifer.

There are several anthropogenic sources affecting this contamination but they don’t have much acceptance. Geogenic sources are widely accepted because they contribute in much greater extent to this contamination.

The worst affected areas in the world with very high arsenic contamination and arsenic poisoning proving to be a huge factor in the mortality rates are Bangladesh, India, Argentina, and Chile. The problem generally emerges because of the consumption of arsenic contaminated water over a long term. As per a survey in 2011, the estimated population at risk is about 750,000 (Chowdhury et al 2000).

Bangladesh is the worst affected country in the world by arsenic contamination. More than 60% of the groundwater available in Bangladesh is highly contaminated with arsenic. About 50-77 million of the total population of about 164 million is under extreme threat.

The concentration of Arsenic varies along space as well as depth. This variation makes it difficult to generalise the state of arsenic in a particular region as small, as a local phenomenon. The main factor affecting this variation is theregional geology (Smedley 2005).

Moreover, arsenic doesn’t have a good correlation with other trace metals, making the arsenic concentration difficult to predict (Kinniburgh et al 2003).

Local geology, confining clay units and aquifer types decide the variation of arsenic concentration along the vertical scale or depth of a region. Chowdhury et al 2000 Apart from local geology, the concentration of arsenic content in the sediments, sorption capacity of the grains, size of sediment grains, and redox condition of the sediments are also responsible (Chakraborty 2015).

The age of the aquifer also decides the variation as aged aquifers take longer to flush out arsenic contaminated water compared to younger aquifers (Kinniburgh et al 2003).

ARSENIC IN GROUNDWATER: SOURCES

Arsenic contamination of groundwater has been a worldwide problem in the last four decades. A huge population is exposed to arsenic contaminated water continuously and this causes arsenic poisoning. The worst affected parts of the world include Bangladesh, India (West Bengal), Argentina, Chile, Western USA, China. An alarmingly large number of aquifers in these countries have been found to be higher than 50 μg l–1, which is much higher than the recent arsenic limit set by World Health Organisation i.e. 10 μg l-1.  

Picture1.png
    World Arsenic Contaminated Groundwater Scenario

    Most of the arsenic contamination of groundwater in the world is very less in terms of area and concentration. The issue lies in the uneven distribution of the element in the ground waters of the world. Specific regions tend to be associated with very high concentrations of arsenic found in the groundwater whereas others don’t.

    Though the environments of these contaminated areas are very different from each other, certain similarities could be observed.        

    The contaminated aquifers are mostly of Quaternary period with an age of about 12000 years (Singh 2006; Julia L and Pamela A 2013). Most of them appear in inland closed basins or alluvial and deltaic plains. They are most common in groundwater with high pH (Singh 2006; Ayotte et al 2003).

    Persistent research is being going on the sources of arsenic in groundwater. The basic problem with the sources of arsenic is that, arsenic is a very mobile element and gets adsorbed, removed, transported, suspended during alteration processes (Guillot and Charlet 2007). But, years of research has provided some acceptable theories to this problem.

    We shall now look upon the scenario in some of the arsenic affected countries of the world.

    BANGLADESH

    Bangladesh comes as a part of the Bengal basin which shelters the Meghna river fault plain and the Sylhet basin. The whole area is majorly affected by arsenic contamination in its ground waters. The basin supports more than 2% of the world’s population and they are affected by this contamination (Chakraborty 2015).

    Picture2.png
      Bangladesh scenario of Groundwater Arsenic contamination

      The arsenic concentration in groundwater ranges from 0.5 μg L-1 - 4730 μg L-1 (Mukherjee et al 2009). Though the sediments present in this area have very less arsenic content, the groundwater is contaminated with arsenic in toxic amounts (Acharyya et al 2000). Many researches have been carried out but no specific reason has been found regarding the contamination. We have some likely reasons to the contamination.

      The Gondwana coal seams deposited under the Basaltic rocks in the Rajmahal Trap and the Rajmahal Basins have a concentration of arsenic around 200 mg/kg (Mukherjee et al 2006). This area is drained by Ganga and its tributaries perennially. It is found that the sediments get triggered by several biogeochemical processes that mobilize arsenic into the surroundings (Singh 2006).

      The mineralised rocks of the mica belt of Bihar contain pyrite and a few other minerals which have arsenic in their lattices; in association with their pegmatites (Chakraborty 2015; Acharyya et al 2000). The concentration in these is found to be about 0.08% - 0.12%. This seems quite a likely source of arsenic (Chakraborty 2015).

      The tributaries of Bhagirathi and Padmalaya that pass through the eastern Himalayas carry arsenic from the Gorubathan base-metal deposits (Julia L and Pamela A 2013; Chakraborty 2015).

      Fluvial sediments from the tectonically active regions of the Himalayas have been regarded as the main sources of arsenic in this region.

        The oxy-hydroxide reduction theory (Bhattacharya et al, 1997) shows that in ferrous-rich waters with anaearobic conditions, Arsenic gets adsorbed to iron or manganese oxides, and releases into the surrounding areas when reducing conditions prevail (Singh 2006; Acharyya et al 2000).

      INDIA

      The arsenic menace in India was discovered in 1983. In West Bengal there are 33 affected villages from four districts. The Gangetic plains and deltas, parts of Bihar, Jharkhand, Chhattisgarh, Uttar Pradesh, and parts of the North-East are also affected (Singh 2006; Acharyya et al 2000).

      Picture3.png
        Arsenic contamination scenario in India

        Research is persistent since the first discovery in 1983. The number of sites discovered has been increasing. Many sources have been detected. The Rajmahal trap, for instance, is found to release 200 ppm of arsenic into the Ganges (Mukherjee et al 2009; Acharyya et al 2000).

        In the Darjeeling Himalayas, 0.8% arsenic is found trapped in isolated sulphide outcrops. In the upper zones of the Ganges, outcrops with varying concentrations of arsenic are found (Acharyya et al 2000).

        The most accepted source is the Himalayan sediments that fluviate to the plains and basins (Chakraborty 2015).

        In Chhattisgarh, the source of arsenic varies. It occurs in geothermal fluids that disseminate into the rocks. The chemical weathering of these rocks releases arsenic into the surroundings. The contamination is highly localised depending upon the source (Mukherjee et al 2006).

        A WIDER FOCUS ON THE BENGAL BASIN: THE PLATE TECTONICS CONNECT

        The geo-morphological setup affects deposition of rocks in the eastern belt of India

        1. All rivers in India flow towards the east except Narmada and Tapti which flow towards the West.

        2. This happens because the tectonic plate on which India resides has a 30 degree tilt towards east.

        3. Narmada and Tapti flow towards West because they encounter the fault mountains of the Aravali Range which changes their direction

        4. Sedimentation is also maximum on the East because Ganga carries all the sediments through its course of flow and by the time it reaches Bengal, its force reduces making those sediments form a delta after deposition. It is found that those sediments contain arsenic.

        5. In the west, sedimentation is reduced in the fault basins. Besides, the waves of the Arabian Sea are very high and deposition is not quite feasible there.

        6. The continental shelf in the east is more planar than the west making it possible to hold the sediments in a more stable manner. 

        ARGENTINA

        Argentina has one of most affected regions in South America.    (Mukherjee et al 2006). With a concentration ranging from 1 μg L−1 to 11500 μg L−1, it has become an area of severe arsenic contamination with over 8 provinces badly affected. The most affected areas lie in the Chaco-Pampian plain of Central Argentina of which Cordaba is the most intensely affected (Mukherjee et al 2009).

        416px-Mapa_arsenico_argentina.jpg
          Groundwater Arsenic Scenario in Argentina - Concentration in ppb

          The source for the contamination of arsenic here is volcanic activity. Arsenic was liberated by rhyolitic glass dissolution into the volcanic ash layers which contained iron and aluminium oxides to adsorb the liberated arsenic (Mukherjee et al 2006). Under alkaline pH conditions, the arsenic could desorb extensively. Other reasons include: overuse of groundwater, high pH, slow rates of groundwater flow, weathering reactions, evaporating concentrations and total TDS. The aquifers in this region are oxic. They oxidise the sulphide minerals containing arsenic and dissolve the silicates enriched with arsenic. Water from geothermal springs also acts as a contaminant of arsenic (Smedley 2005).

          NORTHERN CHILE

          Northern Chile's rivers are the main causes of arsenic contamination (Mukherjee et al 2006). The region is drained by the Rio Loa river which has an arsenic concentration of 1400 μg L−1 and its tributaries have about 1000 μg L−1 (Mukherjee et al 2009).

          922px-Antofagasta_in_Chile_(equirectangular_projection).svg.png
            High concentration of Arsenic is found in the red marked area - map of Chile

            Geological evidence from here is corroborative as a tributary of Rio Loa, Rio Salado, is fed by the geothermal springs El Tatio in the Andean Cordillera. El Tatio is concentrated with about 50,000 μg L−1 of arsenic. The volcanic rocks in the Rio Loa watershed are rich in arsenic content. The sediments were found to have concentrations of around 26 - 2000 mg Kg-1 (Mukherjee et al 2006; Mukherjee et al 2009).

            CHINA

            China has several regions highly contaminated with arsenic, with 40 μg L−1 - 750 μg L−1 in Xinjiang region and about 1μg L−1 - 2400μg L−1 in inner Mongolia (Mukherjee et al 2009). The first cases were reported in 1990 and reports have been increasing. The issue encompasses over 6000 km2 (Mukherjee et al 2006).

            pages-from-piis1607551x11001136.jpg
              Groundwater Arsenic contamination scenario in China

              Sediments found in the Huhhot basin are rich in arsenic. The low lying areas of the Tianshan mountain range is also rich in arsenic (Mukherjee et al 2006).

              Strongly reducing waters in the low lying areas promote the concentration of arsenic in this area. Reduction helps in the mobilization of arsenic like in the case of the Bengal basin. The waters are low in oxygen, sulphate, nitrate and even iron and manganese unlike other arsenic mobilizing reducing environments (Mukherjee et al 2009).

              WESTERN USA

               The United States are highly contaminated in arsenic in their western provinces with the concentration reaching to 2600 μg L−1. The aquifer can be traced back to the Holocene period with alluvial and aeolian aquifers dominating the region. Atleast 10 samples out of every 100 samples tested by Welch et. al, had arsenic content more than 10 μg L−1. The western part of the United States were found to be more contaminated than the eastern part.

              fig2.jpg
                Groundwater Arsenic Contamination in the Western USA

                The climate and geology control the arsenic concentrations in the USA. Fendrof et al 2010 The Rocky Mountain System, Pacific Mountain System and Intermontane Plateau are deeply affected due to the presence of iron oxide ores, evapotranspiration and geothermal waters (Mukherjee et al 2009).

                Arizona, Western Utah and eastern California come under the Intermontane Plateau and Pacific Mountain Systems and have arid climatic conditions. This promotes evaporation increasing the concentration of arsenic in shallow aquifers (Smedley 2005). The concentration turns out to to be as high as 2600 μg L−1 in eastern California and 180μg L−1 -210 μg L−1 in Western Utah. In areas of Western Oregon, the concentration has reached 1700 μg L−1 (Mukherjee et al 2009).

                The concentration of this area is mainly attributed to the iron (oxy)(hydro)oxides in the sediments present in the aquifers which liberate arsenic (Mukherjee et al 2006). Aquifers have both anoxic and oxic waters which help in the desorption and mobilization of arsenic from the sediments. Weathering of felsic volcanic rocks promotes the alkaline pH in the water which in turn helps the desorption and arsenic from the sediments and their mobilization. Geothermal hot springs also act as active sources for the concentration of arsenic in the water (Fendrof et al 2010).

                Picture11.png
                  DATA FOR THESE GRAPHS HAVE BEEN TAKEN FROM Major Occurrences of Elevated Arsenic in Groundwater and Other Natural Waters ABHIJIT MUKHERJEE, ALAN E. FRYAR, and BETHANY M. O’SHEA Mukherjee et al 2009
                  Picture12.png
                    DATA FOR THESE GRAPHS HAVE BEEN TAKEN FROM Major Occurrences of Elevated Arsenic in Groundwater and Other Natural Waters ABHIJIT MUKHERJEE, ALAN E. FRYAR, and BETHANY M. O’SHEA Mukherjee et al 2009

                    ARSENIC AS A HEALTH HAZARD

                    Arsenic is a serious global health concern. It has affected groundwater making it highly toxic in more than 70 countries in six continents. Zhu YG et al 2008

                    Arsenic can enter the human biological system usually through direct ingestion or dermal contact. Out of these two, direct ingestion in the form of drinking water has contributed the most to this fatal hazard all over the world. By consuming groundwater contaminated with arsenic, countries like Argentina, Bangladesh, Cambodia, Chile, China, Ghana, Hungary, India, Inner Mongolia, Mexico, Nepal, New Zealand, Philippines, Romania, Slovakia, Taiwan, and Vietnam are tremendously affected. Millions of people are affected in Bangladesh alone. Drinking water coupled with diet i.e. the intake of rice or fish have been the greatest source of arsenic (Chakraborti et al 2018). Considering the body mass index, children are worse affected than adults. Plus, children are more exposed to dirt and soil.

                    Considering occupational pathways, the workers working at metal smelting industries and the residents nearby these industries are the worst affected (McCarty 2011).

                    Numerous epidemiological studies of chronic arsenic exposure have shown the various health effects on human body caused by arsenic (International Agency for Research on Cancer - WHO 2001). Arsenic is capable of causing very serious health effects such as dermal, cardiovascular, respiratory, gastrointestinal, endocrinological (diabetes mellitus), neurological, reproductive and developmental, cancerous, and cutaneous effects (Chakraborti 2017).

                    HEALTH EFFECTS OF ARSENIC

                    Mandal and Suzuki (2002) http://citeseerx.ist.psu.edu/viewdoc/download?doi=10 studied extensively the health effects of arsenic in the human body. The data can be compiled as follows (Julia L and Pamela A 2013).

                    HEALTH EFFECTS BY CONSUMING ARSENIC CONTAMINATED FOOD AND WATER 

                    SYSTEM

                    HEALTH EFFECTS

                    Cardiovascular

                    Heart attack, cardiac arrhythmias, thickening of blood vessels, loss of circulation leading to gangrene of extremities, hypertension

                    Dermal

                    Hyperpigmentation, abnormal skin thickening, narrowing of small arteries leading to numbness (Raynaud’s Disease), squamous and basal-cell cancer

                    Gastrointestinal

                    Heartburn, nausea, abdominal pain

                    Hematological

                    Anemia, low white-blood-cell count (leucopenia)

                    Hepatic

                    Cirrhosis, fatty degeneration, abnormal cell growth (neoplasia)

                    Neurological

                    Brain malfunction, hallucinations, memory loss, seizures, coma, peripheral neuropathy

                    Pulmonary

                    Chronic cough, restrictive lung disease, cancer

                    Respiratory

                    Laryngitis, tracheal bronchitis, rhinitis, pharyngitis, shortness of breath, perforation of nasal

                    septum

                    Renal

                    Hematuria, proteinuria, shock, dehydration, cortical necrosis, cancer of kidneys and bladder

                     Here is an elaborated description of the health effects caused by arsenic.

                    1. Dermatological Effects

                    Dermatological effects of arsenic exposure have been seen all over the world, predominantly in Bangladesh. Skin lesions occur at arsenic levels of 50 µg/L also. Cutaneous manifestations have proven to be the most prominent characteristics for the identification of arsenicosis in patients. Diffuse Melanosis, darkening of skin, might be seen as the earliest symptoms of arsenicosis. Spotted pigmentation can be seen on the chest, back or the limbs as a sign of the second stage symptoms. Mucous membrane melanosis can be seen in the mouth walls and the tongue.

                    If the victims discontinue the consumption of arsenic contaminated water, the spot remain as black and white marks on the skin.

                    Untitled_1.jpg
                      DIFFERENT SKIN SYMPTOMS DUE TO ARSENIC TOXICITY

                      2. Cardio-Vascular Effects

                      Arsenic has very adverse effects on the cardio-vascular system of the body. Amongst the most fatal are the ischemic heart disease, peripheral arterial disease, also known as the ‘blackfoot disease’ and gangrene. These diseases are subject to prolonged exposure of the human body to arsenic. Hypertension can also be caused by exposure to arsenic.

                       3. Respiratory Effects

                      Prolonged exposure to arsenic has caused chronic respiratory problems in people. They suffer from cough, congestion, difficulty in breathing as well as malignant and non-malignant lung diseases. This is a more serious problem since people tend to ignore the symptoms and don’t even realise the danger that the source carries.

                       4. Gastrointestinal Effects

                      Though the gastrointenstinal effects are not spread over a large scale, they are severe in several cases. Reports of persistent and severe abdomenal pain have been reported. Chronically exposed individuals were diagnosed with dyspepsia. Symptoms of diarrhea, nausea, anorexia are also widely reported.

                       5. Hepatological Effects

                      Cirrhosis, fatty degeneration, abnormal cell growth (neoplasia) are the main hepatological effects caused by direct arsenic exposure. Non-cirrhotic portal fibrosis was the first case detected in India. People suffering from these diseases have been subjected to chronic arsenic exposure through direct consumption.

                       6. Neurological Effects

                      Limb pain, hyperpathia or allodynia, distal paresthesia and hypesthesia, calf tenderness, distal limb symptom, and diminished tendon reflexes are the symptoms of peripheral neuropathy that are prevalent in arsenic affected areas.

                       7. Cancerous Effects

                      Lack of research facilities had confined cancerous arsenic effects to skin cancer only. By now we know that along with skin cancer arsenic also causes several other cancers such as lung, liver, urinary tract, bladder, kidney, and other types of cancers.

                      Untitled.png
                        Patients suffering from arsenic keratosis, affected by pre-malignancy

                        COUNTRY-WISE SCENARIO OF HEALTH DISORDERS

                        BANGLADESH & INDIA

                         Of the 120 million population residing in the Bengal basin, almost half the population are under severe risk of health disorders caused by arsenic. In India, the risk factor is restricted to abot 15 million people whereas in Bangladesh, about 30-35 million people reside with groundwater arsenic concentrations of >50 µg/L-1. Yu, Harvey and Harvey (2003) calculated from a data constructed by Guha Mazumdar et al. atleast 1 million of the total affected population suffers from arsenicosis alone. As many as 59 out of the 64 districts in Bangladesh are worst affected. In West Bengal, Malda, Murshidabad, Nadia, North and South Paraganas are highly affected (Rahman et al 2009).

                        The associated health issues were first identified in India in the 1980s and in Bangladesh in 1993. Groundwater development boards have been appointed to figure out an alternative source to the polluted groundwater to prevent the diseases. Hepatomegaly and Arsenical Dermatosis are well spread in more than 90% of the people exposed to arsenic (Chakraborti et al 2004).

                        Arsenic being highly carcinogenic, the effects such as Leukomclanosis, white spots along with other cancerous effects constitute the latter stage of this exposure. The initial stages show the blackening and hardening of the skin soles on the foot and palm (Chakraborti et al 2017).

                        Common symptoms of arsenicosis can be hypermelanosis on the chest, hyperkeratosis and hyperpigmentation in the soles of palm and feet and non-cirrhotic portal fibrosis. Cases of ‘blackfoot disease’ were also found. Bhttacharya et al. (1996) reported that arsenic has been significantly accumulated in the nails, hair, skin scales as well as biopsy samples of the tested persons.

                        From the data constructed by Khan et al. in 1997, we can display the percentages of manifestations due to arsenic toxicity in the Bengal basin (Rahman et al 2009).

                        Picture13.png
                          MANIFESTATIONS OF ARSENIC TOXICITY IN THE BENGAL BASIN

                          ARGENTINA

                          Groundwater arsenic in Argentina was the first to be discovered in the world in 1917 in the Chaco-Pampian Plains of the Central Argentina. It is perhaps one of the largest regions known to be contaminated with arsenic with the total area summing up to 1 million sq. Km. Regions of Córdoba, La Pampa, Santa Fe and Buenos Aires Provinces. Out of the total population, over 4,000,000 people are under extreme risk zone. Arsenic poisoning, skin lesions are very common in this area. Some cases of internal cancers are also recorded. Lung cancer and urinary bladder cancer is common in the arsenic affected areas of Argentina. It basically depends upon chronic exposure than the concentration of arsenic in groundwater.

                          NORTHERN CHILE

                           Arsenic poisoning in the northern Chile was first found in the 1960s as reported by Rahman et al. 2006. Initial stages showed typical symptoms like skin pigmentation, keratosis and squamous cell carcinoma. The later stages develop into cancer of skin, lungs, bladder and other internal cancers. Cardiovascular problems like cardiac arrhythmias and respiratory problems like rhinitis, pharyngitis are also common in the arsenic affected areas of northern Chile.

                          CHINA

                           Arsenic has been found in the groundwaters of Inner Mongolia, Shanxi and Xinjiang as reported by Smedley et al. 2001. The first cases were reported in the 1980s.

                          The Huhhot basin in inner Mongolia has been the worst affected in terms of health problems faced by the population. Ba Meng, Tumet Plain and Bayingao second the list of the worst affected areas. Many people are found to have visible skin lesions as a result of drinking arsenic contaminated groundwater. Lung cancer has been found to be the most common disease among the population. About 200 cases of cancer have been reported.

                          WESTERN USA

                           Extensive research and water analysis reports on the arsenic contamination of groundwater in the USA have suggested that the contamination is not restricted to a few parts only but is widely spread all over the western provinces. Generally, the pathway of arsenic into the human body apart from groundwater is the sea food consumption. The acute arsenic poisoning in this area initiates its symptoms with vomiting, throat and stomach pain, bloody diarrhea and in the later stage may lead to shock, seizure, coma and also death. The US National Research Council has noted that as many as 1 in every 100 additional cancer deaths could be expected from a lifetime exposure to arsenic concentrations of 50 µg/l.. Population exposed to chronic low level arsenic concentrations are susceptible to heightened risk of skin cancer. Most data is concerned on a small geographical region and can’t be generalised for the whole country. The people using well water that exceeds the limits of the government imposed guidelines are under very serious risk.

                          Picture14.png
                            A graphical representation of the population exposed to arsenic contamination of groundwater

                            CONCLUSION

                            The report is a review of a few and prominent research works on the source of arsenic in groundwater and its health impacts. Arsenic toxicity can be seen in many parts of the world. The concentration of arsenic varies dramatically. For a smaller region, the concentration can be very high and for a larger region, it can be spread at a lower concentration. The countries that are significantly affected are Bangladesh, India, China, Taiwan, Vietnam, Argentina, Chile, Western parts of USA and many others. The Bengal basin comprising eastern India and Bangladesh are the worst affected places in the world, adding to this is the high population of this area. Bangladesh alone has 35 million people under high risk of arsenic toxicity. The maximum concentration of arsenic in the world is as much as 12000 µg/l. In most cases the source of arsenic is geogenic. Previous researches have found that sediments carrying minerals like pyrite are susceptible to an arsenic replacement in its crystal lattice. These sediments when they come in contact with water, in an oxidising environment, form oxyhydroxide rocks that are the principal source of arsenic in reducing waters. Other geogenic sources are geothermal water springs, volcanic eruptions and many others.

                            The health issues related to arsenic are very serious and fatal in many cases. Severe skin lesions, keratosis, melanosis, pharyngitis, several cancers are the results of chronic exposure to arsenic contaminated groundwater consumption. In few cases, patients can get into coma and finally death. Children are born with very weak immune system. Women are most susceptible to arsenic toxicity. Researches have proved that even rice and sea food in arsenic affected areas have high concentrations of arsenic. .

                            Researches are going on to curb the issue and provide safe drinking water to the population on a large scale. Majority help as of now can be proper awareness amongst the public about this issue.

                            ACKNOWLEDGEMENT

                            First and foremost, I shall thank my guide, Dr. Nripen Chanda. He has guided me thoroughly and made this project possible. His valuable guidance and motivation have been the most important factors in this project’s completion.

                             Secondly, I shall thank Dr. Biswajit Ruj for co-guiding me. It has been an honour to work with him. He has taught me every basic that is needed to work on my topic. I am grateful for his every contribution of time, ideas and inspiration. I also thank him for the excellent example he has provided as a successful scientist and advisor.

                             I am even thankful to all seniors in the department, especially, Sankha Chakrabortty, Ankita Mukherjee, Papia Sarkar, and Nivedita Priyadarshni for teaching me the essentials of lab works along with immense motivation and guidance.

                             I also want to thank the Indian Academy of Sciences for giving me this opportunity to work in one of the finest labs of our country. My time at CSIR-CMERI has been a great learning experience and I thank Mr. Soumya Sen Sharma, Dr. Sarita Ghosh, Mr. Manas Banerjee and Mr. Partha Sarathi Banerjee for mentoring us throughout the programme.

                            I would also like to thank AuthorCafe for providing this excellent platform for writing our reports and helping us thoroughly in every step of reporting.

                             Lastly, I thank my family for their moral support without which this project couldn’t have been possible.

                             THANK YOU!

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                            • : Major Occurrences of Elevated Arsenic in Groundwater and Other Natural Waters ABHIJIT MUKHERJEE, ALAN E. FRYAR, and BETHANY M. O’SHEA
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