By Dr. Robin Rattray, Contributor
A health worker test for collected from area ponds in Bangladesh for unsafe levels of arsenic.
IN WEST Bengal in India and in parts of Bangladesh, millions of people are suffering from disfiguring skin lesions associated with skin cancer. Who would have dreamed that the apparently logical act of drilling wells for ground water could have brought on such an affliction? But it did, and the culprit was arsenic, an element that has long been associated with poisoning that leaches into groundwater.
The story itself is fascinating and complicated and may have relevance to Jamaica where high arsenic levels have been found in some soils.
In the past 20 or so years, water from tube wells was recommended for irrigation in India, to support the Green Revolution and feed the country's one billion people. In Bangladesh, over one million of these wells were sunk to replace water from rivers that had been contaminated by sewage and had led to disease outbreaks. As a result, a dramatic increase in pumping of groundwater took place, and by the mid-1990s, what has been described as "the greatest arsenic calamity in the world" began to unfold.
The arsenic occurs in minerals in natural geological formations below the surface of the earth, in the host rock for the groundwater-holding region known as an aquifer. The water levels in the aquifers fluctuate with withdrawal rate. It is suspected that the increased extraction of water was accompanied by the drying out of the minerals and it seems that chemical changes occurred which allowed the arsenic to be released into the groundwater.
CLINICAL SYMPTOMS
The sinister aspect of the situation is that the arsenic acts as a chronic poison, not manifesting its presence until long after exposure has taken place. It is estimated that a period of five to 10 years exposure is needed before clinical symptoms are seen. These symptoms include irritation of gastro-intestinal and upper respiratory tracts, and a general darkening of the skin (melanosis) is the most common symptom - often observed on the palms. Swelling of the hands and feet is often seen. A more serious symptom is keratosis or hardening of skin into nodules, often on palms and soles, with the development of numerous warts and ridges on the finger-nails. This can lead to gangrene and skin cancer.
The World Bank has co-ordinated a project worth almost US$1,000 million to find solutions to the calamity. Some experts have recommended a return to the use of treated surface water as a less expensive alternative to cleaning up the groundwater. In an ironic twist to the situation, the British Geological Survey (BGS) is presently being sued by two Bangladeshi residents, diagnosed with arsenic poisoning, for not alerting them to the presence of arsenic when they carried out a survey of groundwater in 1992. In their defence, the BGS claims that their mandate did not include arsenic measurements as at that time the geological setting was thought not to be compatible with the occurrence of arsenic. The litigation has just started and is being closely watched as a test case by many other affected Bangladeshis.
For more information visit West Bengal and Bangladesh Crisis Information Centre: www.bicn.com/acic/
Robin Rattray, Ph.D., International Centre for Environmental and
Nuclear Sciences (ICENS),
University of the West Indies, Mona, email:rrattray@
uwimona.edu.jm.
