Arsenic poisoning
Nature
Arsenic poisoning (or arsenicosis) is a medical condition that occurs due to elevated levels of arsenic in the body. If arsenic poisoning occurs over a brief period of time, symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.
The most common reason for long-term exposure is contaminated drinking water. Groundwater most often becomes contaminated naturally; however, contamination may also occur from mining or agriculture. It may also be found in the soil and air. Recommended levels in water are less than 10–50 µg/L (10–50 parts per billion). Other routes of exposure include toxic waste sites and pseudo-medicine. Most cases of poisoning are accidental. Arsenic acts by changing the functioning of around 200 enzymes. Diagnosis is by testing the urine, blood, or hair.
Prevention is by using water that does not contain high levels of arsenic. This may be achieved by the use of special filters or using rainwater. There is not good evidence to support specific treatments for long-term poisoning. For acute poisonings treating dehydration is important. Dimercaptosuccinic acid or dimercaptopropane sulfonate may be used while dimercaprol (BAL) is not recommended. Hemodialysis may also be used.
Through drinking water, more than 200 million people globally are exposed to higher-than-safe levels of arsenic. The areas most affected are Bangladesh and West Bengal. Exposure is also more common in people of low income and minorities. Acute poisoning is uncommon. The toxicity of arsenic has been described as far back as 1500 BC in the Ebers papyrus.
Source: Wikipedia
Incidence
The roots of the arsenic crisis in the Ganges delta go back a generation to when most Bangladeshis drank water from rivers and ponds that were often contaminated by sewage. Thousands died each year from gastrointestinal diseases. International agencies such as UNICEF devised a plan to sink boreholes into the sands of the delta that covers much of Bangladesh and the neighbouring Indian state of West Bengal. Unfortunately, nobody thought to check the underground water for natural poisons until symptoms of arsenic poisoning began to emerge, first in West Bengal and later in Bangladesh. In 2000, there were more than 4 million such boreholes supplying water to 95 percent of Bangladesh's villagers.
Claim
1. Whole villages in Bangladesh now show symptoms of arsenic poisoning ranging from skin blemishes to lung diseases, skin cancers and liver failure. Doctors predict that unless urgent action is taken, there will be an epidemic of arsenic-related deaths across southern Bangladesh.
2. Detection of the estimated 2 million arsenic-polluted wells in Bangladesh is a major task because contamination vary drastically - even between neighbouring boreholes and cheap and easy-to-use testing kits are not available.
3. In Bangladesh, the village pumps lowered water levels and allowed oxygen to attack the arsenic-bearing iron pyrite deposits in the sediment. The resulting oxidation - and perhaps other mechanisms - released the arsenic into the water.
4. Another potential culprit in Bangladesh might be agricultural fertilisers. Screenings show unusually high phosphate concentration in the region's water, but it is not sure whether fertiliser is to blame.
Counter-claim
1. The essential process in the release of arsenic into underground water in Bangladesh is not oxidation but reduction. Much of the arsenic is bound to iron oxyhydroxide compounds in the top 40 metres of the delta sediments. Away from the surface, rotting vegetation has consumed all the oxygen dissolved in water, creating an environment in which these compounds release iron and arsenic.
2. Pyrite oxidation would happen mainly in shallow wells (less than 10 metres deep) and the answer will be to dig deeper wells. But iron reduction would happen at deeper levels and the answer will be shallow wells. We can not decide what is the solution until there is more complete scientific data.
Broader
Value(s)
Type
(G) Very specific problems