Groundwater Arsenic Contamination in Bangladesh by yZqISa4

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									       Groundwater Arsenic
Contamination in Bangladesh
             Nadiah Mohd Nordin
                     Erica Islas
          Arsenic Contamination in
                Bangladesh
 By the late 1980s surface water was the main source of
  drinking water.
 Unfortunately, it was severely polluted
 So the government, UNICEF and a few other groups
  decided that they should use groundwater as an
  alternative.
 Ironically, the installations of tube wells triggered the
  naturally occurring arsenic that already existed in the
  earth to dissolve into the drinking water.
 The arsenic that was present in the water was colorless,
  tasteless and odorless, therefore people did not realize
  that their drinking water was contaminated by arsenic
  until there was a widespread of people suffering from
  various diseases, such as warts, skin lesions, and
  cancers.
  Causes of Arsenic Contamination in
             Bangladesh
 Pyrite Oxidation Hypothesis
    Arsenic is assumed to be
     present in certain sulphide
     minerals (pyrites) that are
     deposited within the aquifer
     sediments. Due to the
     lowering of water table below
     deposits, arseno-pyrite
     oxidized in the vadose zone
     releases arsenic as arsenic
     adsorbed on iron hydroxide.
     During the subsequence
     recharge period, iron
     hydroxide releases arsenic
     into groundwater. According to
     this hypothesis, the origin of
     arsenic rich groundwater is
     man-made, which is a recent
     phenomenon.
                  Continued...
 Oxy-hydroxide Reduction Hypothesis
  Arsenic is assumed to be present in alluvial
   sediments with high concentrations in sand grains
   as a coating of iron hydroxide. The sediments were
   deposited in valleys eroded in the delta when the
   stream base level was lowered due to the drop in
   sea level during the last glacial advance. The
   organic matter deposited with the sediments
   reduces the arsenic bearing iron hydroxide and
   releases arsenic into groundwater. According to this
   hypothesis, the origin of arsenic rich groundwater is
   due to a natural process, and it seems that the
   arsenic in groundwater has been present for
   thousands of years without being flushed from the
   delta.
                  Arsenic in Nature

 Rock contains 1.5-2.0 milligram of arsenic per kilogram. But, in
  contaminated soil, concentration of arsenic may be up to 500 mg/kg.
 Arsenic content of natural water may be up to 1-2 g/L.
 Most fruits, vegetables, meats and fishes contain arsenic; but
  arsenic levels in sea water and sea fishes are higher. Sea fish may
  contain 5 mg of arsenic per kg weight.
 An intake of 150 microgram of arsenic per day should not cause any
  harmful effect to human being, but very sensitive person often
  becomes sick with as low as 20 microgram of arsenic a day
             Chemistry of Arsenic
 H2AsO4- + 3H+ + 2e-          H3AsO3 + H2O
 In the environment, arsenic can occur in several
  oxidation states (-3, 0, +3, +5)
 In natural waters, arsenic is mostly found in inorganic
  form as oxyanions of trivalent arsenite [As(lll)] or
  pentavalent arsenate [As(V)].
 As(lll) is more toxic (40-60 times) than As(V)
 As(lll) exists in most natural water as As(OH)3 (pKa =
  9.2) and is more mobile than As(V) because it is less
  strongly absorbed on most mineral surfaces than the
  negatively charged As(V) oxyanions (H3AsO4; pKa =
  2.22, 6.98, 11.53).
 However, it is widely believed that arsenate is the major
  water-soluble species in groundwater because arsenite
  is usually prevalent in anaerobic conditions.
        What makes Arsenic Unique as a
                Contaminant?
 Most toxic trace metals occur in solution as cations (e.g. Pb2+, Ni2+,
  Cd2+) which become insoluble as the pH increases.
     However, arsenate, like most oxyanions, tend to become less strongly sorbed as
      the pH increases.
     As a result, arsenic anions can persist in solution at relatively high concentrations
      (tens of g l-1) even at near-neutral pH values.
 Arsenic is problematic in the environment due to its relative mobility
  over a wide range of natural processes, such as:
       Weathering reactions
       Biological activity
       Volcanic emissions
       Range of anthropogenic activities
 Arsenic is also distinct by becoming relatively mobile under reduced
  conditions. Its oxyanions can be found at concentrations in the mg l-1
  range when all other oxyanion-forming elements are present in the
  g l-1 range. Example:
     Selenium is mobile as selenate (SeO42-) oxyanion under oxidising conditions, but
      immobilized under reducing conditions.
     Chromium behaves like other trace cations (i.e. is relatively immobile at near-
      neutral pH values) under reducing environments.
 Arsenicosis: Toxic Effects of Arsenic
              in Humans
 Arsenic is a poison and its lethal dose for human is 125
  milligram.
 It is 4 times as poisonous as mercury.
 Toxicity depends on the amount of arsenic intake, which
  is classified into acute, sub-acute and chronic toxicity
  respectively. Drinking water contamination causes the
  last variety of toxicity.
 Most of the ingested arsenic is excreted from the body
  through urine, stool, skin, hair, nail and breath. In
  excessive intake, some amount of arsenic is deposited in
  tissues and inhibits cellular enzyme activities.
 Almost all organs are affected; but clinical symptoms
  appear insidiously after 6 months to 2 years or more
  depending upon the amount of arsenic intake.
        Arsenic Toxicity in Different Organ
                    Systems
Organ System                                     Problems
Skin                    Symmetric hyperkeratosis of palms and soles, melanosis or
                        depigmentation, bowen's disease, basal cell carcinoma and
                        squamous cell carcinoma.
Liver                   Enlargement, Jaundice, cirrhosis, non-cirrhotic portal
                        hypertension
Nervous System          Peripheral neuropathy, hearing loss

Cardiovascular System   Acrocyanosis and Raynaud's Phenomenon

Hemopoietic System      Megalobastosis

Respiratory System      Lung Cancer

Endocrine System        Diabetes mellitus and goiter
      Effects on human health
 Cancer            Melanosis




                    Hyperkeratosis
   Clinical Feature of Arsenicosis observed
                in Bangladesh

PRE-CLINICAL              INITIAL               SECOND                   LAST
   STAGE                  STAGE                  STAGE                  STAGE

No clinical           Melanosis,              Depigmentation           Nephropathy,
manifestation         keratosis,              (leucomelanosis),        hepatopathy,
                      conjunctivitis,         hyperkeratosis,          gangrene,
                      bronchitis,             non-pitting edema        cancer of
                      gastroenteritis         of legs, peripheral      skin, bladder
                                              nephropathy,             and lung
                                              hepatopathy



    • In Bangladesh, majority of patients are in initial and second stages
          Treatment for Arsenicosis
 Unfortunately there is no specific treatment for chronic arsenicosis.
  Stopping further intake of arsenic contaminated water and drinking arsenic-
  free water improves the cases.
 A recent report of DCH (2000) states that chronic arsenicosis cannot be
  cured, but the symptoms are reversible up to certain point if a patient
  discontinues ingesting contaminated water.
     Chelation therapy helps relief of symptoms and improves clinical manifestations.
          D-penicillamine (250 mg 3-4 times a day for 3 months)
          Dimercapto succinic acid (10 mg/kg body weight daily for 7 days followed by 10 mg/kg
           body weight thrice daily for 14 days)
          Dimercapto procane sulphonate (100 mg 3-4 times a day every alternate weeks up to 3
           such courses).
     Vitamins:
          Vitamin A- 50,000 i.u. daily, Vitamin E- 200 mg daily and Vitamin C- 500 mg daily for
           adults.
     Symptomatic treatments, viz. antihistamines, local ointments, etc.
     Nutritious diets.
 If a patient crosses this threshold, he/she still needs medical assistance to
  save his/her life. For instance, amputation may save the life of a patient
  suffering from gangrene. Palliative drugs may also be administered along
  with micronutrient supplement.
In Bangladesh, following de-arsination
         methods are used:
 Arsenic Removal Chemical Method
    Developed by the Department of Occupational and Environmental
     Health of NIPSOM, which is based on the principle of iron coagulation
     with a pre-oxidation step. Removal of arsenic by this method is almost
     99%.
 Alum Method
    This cheap method allows 70% removal of arsenic. 300-500 grams of
     alum wrapped in a clean cloth is sinked in a bucket full of arsenic
     contaminated water for 12 hours. Upper 2/3rd of the water is separated
     using decantation or two layered clean cloth. Lower third of water
     contains arsenic and not suitable for drinking.
 Ferric oxide-manganese dioxide clay based filter columns
    This earthen column packed with the above substances is attached to
     the tube well outlet. The method is claimed to remove significant
     amount of arsenic at the water flow rate of 90-110 mL/minute and the
     system can filter up to 5000 L of water before disposal.
          Control Measures Taken by
          Government of Bangladesh
 Short Term Programs
    Conduct survey to detect problem prone population group who is
     drinking arsenic contaminated water.
    Detect arsenicoses patients
    Provide treatment to arsenicoses patients and ensure follow-ups.
    Create alternate source of drinking water in problem prone areas.
     Distribute de-arsination filters and digging deep tube wells. Encourage
     people use alum to de-arsinate contaminated water.
    Create laboratory facilities for quantitative analysis of arsenic and
     determine its toxicity levels in humans.
    Conduct training courses for officers and staff in the health services.
    Conduct national survey to identify new problem prone areas.
    Conduct appropriate health education campaigns.
    Create outpatient services for detection and treatment of arsenicoses
     patients throughout the country.
    Build communications programs with national and international
     organizations for collaboration in the control measures.
                          Continued...
 Long Term Programs
    Find out causes of arsenic contamination of soil water, identify sources
     and take control measures.
    Create a Surveillance Team starting from grass-root level up to the
     central level to identify, treat, follow up and conduct water-testing
     activities.
    Establish 10-bed arsenic hospitals in the affected districts with a view to
     provide treatment to the complicated patients and also conduct
     research.
    Launch a national training course for the health personnel and staff.
    Find out long term alternate source of safe drinking water.
    Launch effective water management scheme for encouraging people
     ensure rational use of ground water.
    Include media people in the prevention of arsenic contamination
     program.
    Develop necessary information, education and communication (IEC)
     materials to enhance awareness of the people.

								
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