Remediation of arsenic for agriculture sustainability, food security and health in Bangladesh

Working paper

Arsenic in groundwater is a major health concern in Asia and the risks from using shallow tube wells for drinking-water are well-known. At present, twelve countries in the Asian region have reported high arsenic levels in part of their groundwater resources. Bangladesh has the highest percentage of contaminated shallow tube wells (~20 percent) and an estimated 30 million people are dependent on those wells for domestic purposes. The problem originates in arsenic-rich bedrock of the Brahmaputra river basin that filters drinking water pumped to the surface through millions of tube wells. Since an initial investigation on arsenic accumulation in rice undertaken by FAO with support from the United Nations Development Programme (UNDP) in 2001, further scientific studies in the last couple of years have reported potential risks from arsenic from dietary exposures. The most well-known concern is arsenic entering the food chain, affecting food safety. This poses a potential dietary risk to human health in addition to the risk from drinking contaminated groundwater. Less well-known but potentially more serious is the risk of arsenic to crop production. Continuous build up of arsenic in the soil from arsenic-contaminated irrigation water reduces crop yields in the long term. As part of the green revolution, millions of shallow tube wells have been installed throughout Asia over the last three decades. This has resulted in a sharp increase of groundwater extraction for irrigation. In Bangladesh, of the four million ha under irrigation, 2.4 million ha are irrigated with approximately 900,000 shallow tube wells. It has been estimated that water extraction from the shallow aquifer for irrigation adds 1 million kg of arsenic per year to the arable soil in Bangladesh, mainly in the paddy fields.

Management options of health risk prevention and agricultural sustainability should therefore focus on preventing and minimizing arsenic input to soils and minimizing human exposures. Various management options are explored in the current FAO-Cornell remediation study. Optimizing water efficiency was shown to be a sound option to reduce arsenic input while saving water; furthermore, aerobic growth conditions in paddy fields were shown to reduce bioavailability and uptake of arsenic in rice. This current working paper reports the first successfully implemented field pilot study in the management strategy of arsenic in crop production and for sustainable environment.

The final report on the overall arsenic issue in agriculture will be released in the near future. The remediation measures mentioned in this report are also applicable and useful as adaptive measures in coping with changing agriculture practice and responses to climate change.

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