This is the greatest case of poisoning in the history of mankind: In Bangladesh, the health of 35 to 80 million people is endangered due to water contaminated by arsenic (Figure 1 [1]). The problem was first detected in the early 1980s in the Indian state of Western Bengal, a neighbor of Bangladesh. It quickly became evident that this contamination also existed in Bangladesh. Another ten years would pass, however, before the authorities and the international community mobilized their efforts. The aim is simple: to make sure the people of Bangladesh have safe drinking water. Achieving it, however, is far more complex. There is no miracle solution in sight and, meanwhile, millions of people are slowly becoming poisoned.
Context
Bangladesh is one of the poorest countries in the world. It has a land area of 144,000 square kilometers and stretches from the Ganges Delta to that of the Brahmaputra. The climate is subtropical, with three main seasons: from March to May, a warm, wet season with regular storms; from June to September, the monsoon, with frequent rains and rising river levels that flood the country; and form October to February, a relatively cool, dry season. These seasons and the level of the rivers regulate life in Bangladesh.
Typhoons from the Gulf of Bengal frequently arrive during the rain season, causing water levels in the delta to increase. These flood seasons may be followed by harsh droughts. Poor in mineral resources, with almost non-existent industrialization, the country relies on agriculture — mostly rice farming — and international aid. Internal political strife and corruption hinder economic reform.
The population of Bangladesh is 140 million, which amounts to a population density of approximately 1000 inhabitants per square kilometer. This is Bangladeshâ€TMs most serious problem: The country is overpopulated, and the birth rate remains high. The introduction of family planning and contraception campaigns has attempted to solve this problem. More than 80 percent of the population lives in the countryside. Under the duress of natural conditions and with little help from the corrupt authorities, most Bangladeshis cannot but count on themselves and on international aid for their survival.
Sources of the problem
The supply of water has always been a problem in Bangladesh. Until the 1970s, Bangladeshis used surface water that was contaminated with microorganisms, which spread permanent epidemics of diarrhea and cholera. Children were always the hardest hit by those diseases. UNICEF (the United Nations Children Fund) and WHO (the World Health Organization) decided then to install millions of wells in the country to give people access to groundwater, which was supposedly safe. Eight million such wells were built, giving access to groundwater to more than 80 percent of the population. Construction of those wells helped to decrease drastically the diseases due to consumption of surface water. Unfortunately, no tests had been done on the groundwater to determine if it contained arsenic.
The arsenic in Bangladeshâ€TMs groundwater has a natural origin. The Earthâ€TMs crust contains about 2 milligrams of arsenic per kilogram. With erosion, the arsenic contained in the minerals is released in its trivalent form. In the presence of oxygen, it oxidizes to become pentavalent arsenic and binds to iron hydroxides, which will then be carried by rivers. Arriving in the large deltaic plains, these compounds will settle and accumulate. Contamination by arsenic is a worldwide problem which concerns countries like India, Bangladesh, Vietnam, Chile, Argentina, China, Mexico, and Hungary. In the last three countries, however, the existence of arsenic in drinking water is not completely of a natural origin: Contamination may be caused by the presence of mines or the massive use of phytosanitarian products. Switzerland is also affected in certain areas with well-defined boundaries. Switzerland, however, has the means to reduce these pollution problems quickly.
Effects on health
Arsenic belongs to the list of oligo-elements essential to life, but in excessive amounts it is harmful to human health. Most arsenic that is ingested is metabolized to render it less toxic and is then eliminated from the body. The effects of arsenic from drinking water contamination appear slowly. It can take ten years from the first consumption before symptoms appear, in the form of skin lesions. The interval between first consumption and the appearance of symptoms depends on the arsenic concentration in the water. The health of the victim will go from bad to worse, little by little. After twenty years of exposure to arsenic, the risk of certain cancers becomes high, including skin cancer or internal cancers damaging the liver, the lungs, the kidneys, or the bladder. If skin lesions become infected, death may come sooner. Nutrition plays an important role in the time of appearance and the intensity of problems due to arsenic. Endemic malnutrition in Bangladesh makes the population more vulnerable. Food shortages and nutritional deficiencies due to poor diet are common. In particular, Bangladeshis frequently suffer from a deficiency of vitamin A, found in green vegetables and in dairy products. This vitamin plays a role in skin regeneration, and the lack of it in oneâ€TMs diet quickens and amplifies the effects of arsenic on health. Other deficiencies make the problem worse.
The detection of arsenic
There are two types of tests that lead to detection of arsenic in water, the in situ test and the laboratory test. The in situ test consists of a kit that determines whether the sample contains an arsenic concentration over the normal level of 50 micrograms per liter. The laboratory test requires a heavy infrastructure and generates further costs. In addition to measure the quantity of arsenic in a sample, the laboratory test helps to differentiate the various arsenic-containing compounds in the sample. This is the only means to know the exact concentration of arsenic in water. The in situ test uses reagents produced locally and their manufacturers used to boast that their kits were reliable to concentrations lower than the WHO norms. It turned out, however, that 68 percent of 1.3 million wells were contaminated while the in situ tests declared them as safe.
Alternatives to these detection kits have begun to appear. For instance, the EAWAG, a Swiss institute for water protection, designed a test using bacterial biosensors to detect the presence of arsenic in water. The test uses a piece of cardboard covered with genetically-modified bacteria that change color when exposed to arsenic. This technique allows the detection of arsenic in water at concentrations lower than 10 micrograms per liter. The test is entirely qualitative and allows one to run several tests at the same time as a control check. Biosensors should be easy to use as a field kit, for this technique is simple to use, precise, and cheap (two cents US per sample). There are some drawbacks with this technique, however, such as the high humidity in Bangladesh that deteriorates the cardboard. Among other problems is the possibility of the bacteria reacting with other substances in the water, and also what do with the bacteria in the water after the test is run. In addition, it is forbidden by international legislation to use modified bacteria outside laboratories – and nothing hints that Bangladeshis will accept such a method to run water tests.
For all the efforts made to test a maximum of wells, the great majority has not yet been tested and some have been tested with insufficient reliability. The cost of testing the remaining wells is estimated at US$4.7 million, and new wells are dug every day without first being checked for water safety. New field kits manufactured locally and the good results that the biosensors have achieved leave hope that the millions of Bangladesh wells can all be tested in a reliable manner at least once.
To date, no regular tests of wells have been instituted. It is generally reckoned that wells should be tested once or twice per year. A protocol for well control has finally been established by the Department of Public Health Engineering (DPHE) and the WHO in February 2003. Managing the water quality in Bangladesh requires a database accessible to the public that would store test results and allow new entries at any time. This would facilitate the creation of more exact maps on the water quality situation in the country and the possibility of continually updating them. The National Arsenic Mitigation Information Centre has been mandated to set up such a database.
The experts that come to run tests have the opportunity to speak with the local people. It is best to immediately inform people of the results and to explain these to them. In the event that the concentrations are over the established Bangladeshi norms, the expert has to explain carefully why the well is declared unsafe.
Methods of decontaminating water
A number of means exist to decontaminate water. The first solution proposed is to remove arsenic from water. Four such techniques were recently permitted by the Bangladesh Council of Scientific and Industrial Research (BCSIR), on 25 February 2004.
The first is a filtration method that has been used for centuries by Bangladeshi women: a system of three nest jars, called kalshi, through which water is slowly filtered. The technique has been slightly adapted by adding cloth, sand, and small pieces of charcoal and iron to the bottom of the upper kalshi; and adding to the second kalshi a layer of charcoal, a layer of sand, and, finally, a layer of cloth. Water that reaches the bottom of the three kalshi is drinkable.
The second solution is an adsorption system, which relies on alumina (Al2O3) to adsorb arsenic. This method is not commonly used in Bangladesh, probably because alumina is produced by India. Adsorption processes have been designed using iron oxide, however, which is available in Bangladesh. In either case, there is no scheme to sufficiently deal with the contaminated substrate on which adsorption takes place. The best that can be done is to treat these compounds with special filters that collect between 50 and 85 percent of the arsenic. Using a similar idea, the third method uses ion-exchanging resins to retain arsenates in water and let the water pass through.
The fourth method is photo-oxidation. Here, a simple PET bottle is filled with contaminated water and lemon juice that has been exposed to the sun for a few hours. Iron hydroxides precipitate, allowing decantation to separate the remaining pentavalent arsenic.
One obvious alternate solution is, instead of drinking groundwater, to collect rain water using water tanks. During the dry season, however, people will not be able to collect water in this manner. This system also requires regular cleaning, for tanks may be contaminated by animal excrement. This solution would require the cooperation of local populations, which would help foster social cohesion. People must be hinted at organizing themselves in this way, however, for they will not likely take this initiative on their own.
Water ponds may be used as a source of drinkable water if people are taught to use them only for drinking water. Using a filter made of sand on the side of the pond, it is possible to pump water fit for consumption. There is no miraculous solution to the problem, but it is above all important to make people aware of the problem so that they can become motivated to set up solutions. Medical information on the effects of arsenic poisoning would get people to come and receive medical treatment. Diet must also be changed by encouraging people to vary the food they grow and also to grow fruits and vegetables. There is also a need to educate competent local people to handle the water contamination.
Feedback
There is still hope that Bangladeshis will find a solution to their problem. There is money, existing structures, and thousands of people asking to be educated. If a way to detect arsenic easily, reliably, and cheaply can be found, use can then be made of the variety of good means of decontaminating water that already exist. Alternative means of providing mean should be extended and used as much as possible. Given the urgency of the problem, both short- and long-term solutions must be introduced simultaneously.
The greatest uncontrollable variable is the contamination of rice by irrigation water. If it is found that contaminated rice also harms human health, then a solution for contaminated irrigation water will also have to be found.
The scope of the problem requires Bangladeshis to become involved, for the international community can bring only money and know-how to Bangladesh. The international community cannot, however, pay the entire cost. There is thus a need to implement a solution for this problem that would allow Bangladesh to be self-reliant — a system run for Bangladeshis and by Bangladeshis.
Personal feedback (by Xavier Bengoa)
Six months after completing our reflection on the arsenic contamination of drinking water in Bangladesh, I was able to meet two engineers from Dhaka, the capital of Bangladesh. Both graduated in the past three years, one of them in Urban Planning and the second in Civil Engineering. Both are now starting masters programs in Environmental Engineering and Sustainable Infrastructure in Stockholm. This was, for me, the first occasion to talk about the problem with people who are directed connected to it.
The two engineers were surprised to see that anyone was aware of what is happening in their country but were pleased to share with me their knowledge and opinions. In fact, they knew very well the consequences of the contamination and what had led to the present state. They also knew who the main actors were in the field and what the difficulties were in working with the Bangladeshi government.
These were, of course, two literate Bangladeshis who have been to university, but their belief about the contamination seemed fatalistic. People were working on it, but as no one seemed very concerned about it in Europe and North America, things would change slowly and people would get used to the situation. My opinion was that they already seemed to be. It was interesting that they immediately asked me if I wanted to write my thesis in Bangladesh. I saw this as an offer to deepen my knowledge of the problem, and, at the same time, a demand for international interest.
On the issue of overpopulation, I read recently that Dhaka will be the worldâ€TMs fifth-largest city by 2025. An analysis of the cityâ€TMs use of resources, however, shows that countries like the Netherlands are proportionally much more overpopulated than Bangladesh, where the level of consumption and the production of waste per capita are much lower. Moreover, local people do not see overpopulation as an important issue. It seems that the lack of interest comes mainly from a certain class of Bangladeshis who, because of their more affluent status, do not see the emergency of the problem. This may be due to the very slow development of diseases caused by arsenic. I hope that educated people will start to become involved voluntarily in the mitigation and supervising processes, which can be the key for a positive and sustainable improvement of the situation.
