Monday, July 12, 2010

Case study: Arsenic poisoning in Bangladesh

After knowing more about arsenic, we will now look at a case study of Bangladesh to showcase the seriousness of arsenic poisoning to human health.

Picture extracted from:

High level of arsenic contamination can be observed in Bangladesh with more than 20 % of the total land contains arsenic of concentration more than 50 μ g/ L as depicted from the picture.


Arsenic is naturally occurring in pyrite bedrock underlying much of West Bengal. The poisoning began to occur as millions of kiloliters of water were being pumped out from deep within underground reservoirs for more water resources. As a result, the water level dropped and exposed the arsenic-bearing pyrite to air leading to oxidisation, a reaction which flushed arsenic into the remaining water, contaminating them with arsenic compounds. This has lead to a large numbers of clean wells to be contaminated and expose more people to arsenic poisoning.

In the 1970’s, villagers in Jampukkur started to notice dark spots spread across their bodies; not knowing exactly what was actually causing it. Until 1993 did the villagers learned that they were drinking arsenic contaminated water with 95% of the village wells being contaminated.

Social effects...

Besides health effects, arsenic also poses several social effects to the people of Bangladesh. Not only did arsenic take away millions of life in Jampukkur, it has also leaved citizens in tremors and pain. More reports of broken marriages surfaced when husbands send disfigured wives back to their parents for the fear that their wives disfigure is cause by arsenic poisoning. In Jampukkur, literally no young men and women get married at all. People believe that arsenic poison can be passed on from the parent to child, leading to many arsenic poisoned women having problems finding husbands.

Hence, it is evident that people suffering from arsenic are neglected by friends, neighbours and even their own relatives. They are either avoided or discouraged to appear in public places. Children who are affected are not allowed to go to school while adults are discouraged to attend public meetings and going to the office to work. Even qualified individuals are refused jobs if they are found suffering from arsenic poisoning. People in the surroundings are also indirectly affected as they grief over their loved ones who are suffering from the poisoning. Above all, those people who are affected will not have a proper social life.

The picture shows a woman in Bangladesh with skin lesions on her soles as a result of drinking water contaminated with arsenic


Some scientists hypothesize that Bangladesh's problem is caused by local water chemistry. Others suggest it is because of the way vegetation decomposes in the monsoon cycles of wet and dry periods, which affect levels of oxygen in ground water.

And local factors enhance the impact of the poison, including a poor diet and addiction to chewing intoxicating betel palm seeds.
Prevention is the only solution, because there is no satisfactory treatment to arsenic poisoning, say experts.

Villagers pumping water at a Bangladesh well.

The table above shows the arsenic calamity in Bangladesh.

Monitoring arsenic in Bangladesh....

As mentioned in our video, scientists uses field test kits to monitor arsenic in Bangladesh. We discussed previously that arsenic normally exists in groundwater in the form of arsenite and arsenate. Arsenate is reduced to arsenite by using reducing agents such as potassium iodide and stannous chloride. Arsenite is then added to zinc and hydrochloric acid, which produces arsenic in the form of gas, known as arsine gas. The arsine gas is then treated with a specially prepared paper disk, which will show a change in colour. Scientists will then compare the color produced with a color scale to determine the concentration of arsenic in the water sample. An example of a method that uses this principle is the determination of arsenic by Arsenomolybdate, which is a relatively inexpensive and accurate method of detection. The arsenomolybdate is measured spectrophotometrically at 835nm.

The diagram above shows the instruments used for Arsenomolybdate

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