Editorials

Providing clean water: lessons from Bangladesh

Large parts of the world face an unwelcome choice between arsenic and micro-organisms

The people of Bangladesh are being slowly poisoned. Although the world has known this since 1998, the full implications are only just being realised. Up to 57 million of Bangladesh's 130 million inhabitants are drinking water that contains harmful concentrations of arsenic.¹ The tragedy is twofold: it was a well intentioned public health measure that caused the problem in the first place, and there are no easy solutions. Discussion at a meeting in January between the Department for International Development, the British Geological Survey, and non-governmental organisations emphasised the difficulties of reaching a workable long term solution.

The World Health Organization's provisional guideline is that drinking water should contain no more than 10 µg/l of arsenic,² though the Bangladesh standard is 50 µg/l. Water samples from many Bangladeshi tubewells have concentrations exceeding these values, with extreme concentrations greater than 500 µg/l. ^{1 3}

Chronic arsenic ingestion has many health consequences, ranging from skin disorders to cancer, diabetes, and cardiovascular, respiratory, and peripheral vascular disorders. A clear dose response relation exists between arsenic concentration and skin and internal cancers, with a latency period of up to 20 years.⁴ Though chelation and vitamin supplementation have been tried, the only effective treatment is to stop drinking the contaminated water.

From the 1980s onwards an international collaborative effort has worked to provide access to clean water for people living in developing countries. Millions of tubewells have been sunk around the world in an attempt to tap into the earth's hidden asset, groundwater. Groundwater is found at varying depths underneath the earth's surface, in permeable rocks known as aquifers which are saturated by the infiltration of rainfall. It usually has excellent microbiological and adequate chemical quality for most uses⁵ and has obvious advantages over surface water, which is often contaminated with micro-organisms. In Bangladesh using groundwater instead of surface water is thought to have contributed significantly to halving infant and under 5 mortality rates.⁶

No one knows the number of tubewells in Bangladesh, but current estimates are that there are 6 to 11 million. Many have been sunk by the Bangladeshi government, international agencies, and non-governmental organisations, but most are private wells installed by individuals. What no one knew at the time, and which did not come to light on an international scale until around 1998, was that, owing to the geology of the underlying rocks, this "groundwater saviour" has become a killer.

Surveys by the Bangladeshi government and the British Geological Survey have begun to estimate the scale of the problem and also highlighted the difficulties of solving it. ^{1 3 4} Arsenic concentrations can vary from well to well, even within the same village. This means that every well providing drinking water has to be tested before it can be declared safe. In addition, arsenic field kits can reliably detect only concentrations of 100 µg/l or more, and kits are difficult to obtain in the numbers needed.

The Bangladesh arsenic mitigation water supply programme was set up in 1998 with a loan of $44m (£30m) from the World Bank in an attempt to assess the scale of the problem and implement some solutions (www.BAMWSP.org). However, little practical action has been taken, and the people of Bangladesh are still waiting for their safe drinking water. Potential long term solutions include digging deeper tubewells to access aquifers that might have lower arsenic concentrations; water filtration to remove arsenic; chemically treating surface water; and harvesting rainwater.⁴ Difficulties exist with all these, however. Geologists still do not know enough about the properties of the aquifers to be certain that digging deeper wells will help; reverting to surface water and rainwater, even if treated, still carries the risk of communicable disease; and high tech solutions rarely work in developing countries. Non-technical strategies include health education about sanitation practices, and some water charities are diverting their resources into this, with some anecdotal success.

Meanwhile, people are dying. Not just in Bangladesh but in other countries such as China, Mexico, Argentina, and Chile, where arsenic levels are also known to be high and the exact scale of the problem unknown. In pursuit of clean drinking water has the world shot itself in the foot? Or could we have done any differently, even if we had known 20 years ago that arsenic might be present in groundwater? Should the people drinking water contaminated with arsenic be advised to go back to drinking water contaminated by micro-organisms? In public health terms the risk of dying from diarrhoeal illnesses is greater than that of dying from arsenic poisoning. But the people drinking the water should be deciding, not the donor agencies. In the face of all this uncertainty, one thing is beyond doubt. If a developed country was cursed with the geology of Bangladesh it would have mechanisms in place to deal with it and its people would not be drinking poisoned water. Water problems tend to disappear when a country becomes rich.

Rhona MacDonald, editorial registrar. 

BMJ