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Source of Mass Arsenic Contamination in Bangladesh Traced

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It has been amongst the most ironic tales of foreign aid observed in any developing country. But now new research may help understand the problem better and shed ways to combat it.

Back in the 1960s and 1970s, Bangladesh suffered from really high mortality rates. Unclean drinking water resulted in the death of over a quarter million children every year. The UNICEF and World Bank decided to combat the dual problem of contaminated surface water and providing water for agriculture by funding the construction of millions of deep tubewells all over the country.

The waters had not been tested for arsenic poisoning as it hadn't been considered a major issue at the time. But around the 1980s, cases of arsenic poisoning came to the fore, with symptoms of lesions on the hands and feet. It was brought to the attention of the international community in the late 1990s that the tubewells contained very high levels of arsenic. The wells which were to provide pure water to the Bangladeshis were themselves contaminated. The total magnitude of this problem is still not clear as arsenic poisoning takes many years to show. World Bank reports estimate that close to 25% people in Bangladesh are at risk, with more than 10,000 confirmed cases of arsenic poisoning. The numbers of affected individuals are estimated to be around 100,000. It is widely regarded to be the largest mass poisoning of all times.

In 2004, projects financed by the World Bank and Swedish government tested 5 million of the 11 million tubewells in the country and found 1.4 million tubewells to be contaminated.

Bangladesh is a poor country, with a nominal GDP of only $520, due to which it has lacked the resources to effectively combat issues of such magnitude. With other diseases competing for attention, Bangladeshis have found themselves drinking the poisoned water, with no alternative sources available.

Furthermore, until now the mechanisms which lead to the arsenic poisoning had not been discovered thus complicating the search for a solution. In 2002, a MIT team led by Charles Harvey, a Doherty Associate Professor of Civil and Environmental Engineering had discovered that microbial digestion of carbon in the silt was releasing trapped arsenic. The high levels of arsenic in Bangladesh have been blamed on the country’s geology. Arsenic is widely distributed throughout the earth’s crust and it enters via the dissolution of minerals and ores and erosion of rocks. Levels of arsenic are especially high in South Asian and East Asian regions, and the silt deposited by rivers usually contain arsenic.

However, the cause of carbon in the silt, which led to the release of arsenic, was still unknown until now. Another research team from Massachusetts Institute of Technology has now found that the likely cause are man-made ponds. These man-made ponds are excavations which have filled with rainwater.

Scientific American reports: "Using a six-square-mile test plot, they found that the organic carbon comes from shallow ponds that were dug to provide soil for flood protection. The carbon compounds sink in the pondwater and seep underground where bacteria digest them, setting up the perfect chemical conditions to free up the soil’s arsenic. Groundwater flow then brings the arsenic-rich water to the wells."

The team also suggested two methods which might help in reducing the problem — digging deeper wells that go below the influence of the ponds, and using wells that retrieve water from beneath rice paddies, which the team found to be less toxic than other wells.

The cause of arsenic poisoning has been a puzzle for many years now. While solving the problem of arsenic poisoning in Bangladesh is complex and will take a lot of resources and effort, these findings will go a long way in finding a permanent solution to this calamity that is affecting an entire nation.

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