Combat Arsenic Crisis in Ganga-Meghna-Brahmaputra (GMB) Plain
During our last 17 years of survey in GMB plain we identified 5750 arsenic affected villages. The GMB plain includes the following states in India : Uttar Pradesth (UP) in the upper and middle Ganga plain, Bihar and Jharkhand in middle Ganga plain. West Bengal in lower Ganga plain, and Assam in upper Brahmaputra plain. Bangladesh falls in Padma-Meghna-Brahmaputra plain. We analyzed 1,45,000 and 52,000 tubewell water samples from India and Bangladesh respectively with FI-HG-AAS. In India 48.7% water smaples had arsenic concentration above 10 ppb and 23.8% above 50 ppb. In Bangladesh these values were 43.0% and 31.0% respectively. Almost 9 million people in India was drinking water with more than 10 ppb arsenic and 7 million people with more than 50 ppb arsenic, while in Bangladesh the affected population were 52 and 32 million respectively. Importantly a good proportion of the people could be sub clinically affected.
So far we have screened 1,42000 people including children (below 11 years age) with our medical team for arsenic toxicity. Almost 9.89% (n= 1,23,000) of the patients screened from India (which inlcude our recent survey in Bihar, UP, Jharkhand) showed arsenical skin lesions while in Bangladesh the ratio was 19.8% (n= 19,000). Another worrisome fact is, our previously reported study showed that within a span of 3-7 years many village tubewells which were safe (arsenic<10mg1-1) are getting contaminated now (arsenic >50mg1-1) and arsenic concentration in many tubewells has increased by as much as 5-20 fold. Therefore it appears that a good proportion of all the states and countries in the GMB plain comprising an area of 5,69.783 sq. km and a population of over 500 million may be at risk from groundwater arsenic contamination.
A few million US dollars have already been spent and millions being spent in the ongoing projects on field kits to classify tube wells delivering arsenic below 50mg/L (the recommended limit in developing countries) as safe, painted green or above 50mg/L, unsafe and painted red. Field kits have tested more than 1.3 million tube wells in Bangladesh alone. However, the reliability of the data generated through field kits is questionable.
Installation of hand tube-well attached arsenic removal plant in the affected areas is one of the alternative ways to provide safe drinking water to the people. But the experience of ARPs is not at all satisfactory to recommend it as a mitigation means. In our extensive survey on arsenic removal plants installed in different parts of West Bengal-India at an expense of millions of dollars, we have noticed that, though some of the plants could remove arsenic below 50µg/L levels, none of them could bring down arsenic level below 10µg/L.
Furthermore, considering the plight of children in the arsenic affected regions of West Bengal and Bangladesh the case would be more evident. Infants and children are often considered more susceptible to the adverse effects of to toxic substance than adults Differences in metabolism of arsenic in infants, children and adults could be responsible behind differing susceptibilities between these subpopulations. In one of our studies on an arsenic affected population in Bangladesh we have found that second metabolic step in arsenic metabolic pathways is more active in exposed children exposed adults.
In arsenic affected areas of West Bengal and Bangladesh arsenic contaminated water is not only used for drinking and cooking but also for agricultural irrigation. Thus arsenic comes into the food chain. It has been estimated that from a single block Deganga in North 24 Parganas (area 200 sq. km) 6 tons of arsenic from 3200 irrigation tubewells is falling agricultural fields. Our specification studies revealed most of the arsenic in rice and vegetables is in inorganic form.
In September 2003, BIS (Bureau of Indian Standards. 2003) set the desirable limit of arsenic in drinking water to be 10mg/l (yet to be accepted by Government of India). In repercussion, in concluding remarks of a recent publication in Toxicology (Smith. A. H. and Smith, H. M. 2004) which discussed about implications of drinking water standards in developing countries especially on magnitude of cancer risks, the authors suggest to raise the guideline value to 50mg/l in case of developing countries. In the same article the authors stressed how malnutrition plays a significant role in increasing the risk of arsenicosis.
Thus a large section of population living in villages in India and Bangladesh are more susceptible to the danger of arsenic. Epidemiologicah studies ascertain that drinking water with as concentration between 0.01 to 0.05mg/l for more than 10 years could produce pigmentation and keratosis in some people. It is also noteworthy that EPA calculated the standard value on basis of l.2L/day water intake value while in case of WHO standards the value was taken as 2L/day. In our extensive survey on a population in a village in West Bengal we have calculated that average volume of water intake per day for adult males adult females and children is 4L, 3L and 2L respectively. This value can be extrapolated to vast region of West Bengal and Bangladesh considering hot and humid climate prevailing there. This value excludes arsenic inclusion into body burden through food chain. It is also been highlighted in literature that the cancer risks might be of the order of as high as 1 in 100 for 50 µg/1.
To understand how effective are the million dollar mitigation programs undertaken in Bangladesh, we made a comparative study in Eruani village (PS: Laksham. Dist: Chandpur) in two different time periods once in the year 1998 and again in 2004 during the fifth International arsenic conference held in Dhaka. During these surveys we collected hand tube well water samples and biological samples for arsenic analysis and our medical team screened villagers for identifying arsenicosis patients. Our analytical results indicate that the arsenic contamination situation and consequently the sufferings of the villagers of Eruani have rather aggravated over a time span of 6 years despite spending more than 100 million dollars for arsenic mitigation in allover Bangladesh.
To combat the present arsenic crisis in the GMB basin we urgently need to consider the following options. West Bengal, India and Bangladesh are called the lands of rivers. During the monsoons, when the average annual rainfall in these regions is about 2000 mm. the rivers are abundantly fed. In addition, there are other available surface water resources such as wetlands, flooded river basins, lagoons, ponds and ox-bow lakes. The per capita available surface water in Bangladesh is 11,000 cubic meters and in arsenic affected areas of West Bengal about 7,000 cubic meters. Instead of sinking tubewells and pumping out underground water without any test, oversight or regulations the use of surface water needs to be seriously considered. One of the long-term solutions may be digging deep lube wells, which extract from aquifers 200 meters or further below.
Deep tubewell is a source of arsenic safe water and possibility of arsenic contamination is less if the deep tube well construction is done properly and the aquifer tapped is underneath a thick clay barrier. In case of deep tubewells we must test for the oilier contaminants. Alternative safe water sources such as dug-wells and rainwater harvesting with controls for bacterial and other chemical contamination need to be implemented. Above all, the villagers in the affected areas need to be educated about the existence, magnitude, danger and sign and symptoms of the arsenic problem.
Dipankar Chakorabarty, School of Environmental Studies (SOES), Jadavpur University, India and is a pioneer in war against Arsenic. Source: The Independent, January 16, 2006