Cultivating paddy on raised beds, rather than in flooded fields, will help reduce arsenic contamination of rice and cut water use.
Studies have reported that 20 countries, 12 in Asia including India and Bangladesh, have high levels of arsenic, a poisonous compound, in ground water resources used for drinking and irrigation. Widespread use of arsenic-contaminated irrigation water ultimately leads to issues of food security, food safety and environmental degradation.
Said to be an off-shoot of the green revolution, the arsenic crisis was identified in Punjab, Haryana and Himachal Pradesh in 1976 when preliminary survey on arsenic in dug wells, hand pumps and springs were conducted.
A recent survey by the School of Environmental Studies, Jadavapur University, has found that 3417 villages in 111 blocks in 11 districts in West Bengal have been facing arsenic contamination of drinking and irrigation water. A 1988 survey had found only 22 villages in five districts.
A new report by the Food and Agriculture Organisation (FAO) of the United Nations showed that high levels of arsenic in rice grains can be greatly reduced by applying improved irrigation management practices.
A study conducted by FAO in cooperation with the Cornell University revealed that planting rice in raised beds, around 15 cm above the ground, and not in conventional flooded fields, counteracted yield losses and resulted in lower arsenic levels in both crops and soil. Raised rice bed was also found to lessen the effects of drought and flooding, therefore serving as an adaptation to climate change. The study was conducted in Bangladesh, where the highest arsenic groundwater contamination has been recorded.
Sasha Koo-Oshima, FAO water quality and environment officer, said that identifying and targeting rural areas that are worst affected by arsenic contamination and further developing and extending the raised-bed-system should become a main priority in order to reduce the risk of arsenic contamination to human health.
FAO-UNDP studies have reported potential risk of arsenic from dietary exposures.
The major concern is its entering the food chain. This poses a potential dietary risk to human health due to arsenic toxicity to rice and possibly to animals when high arsenic rice straw is used as feed. These are in addition to the risk from drinking contaminated ground water.
A more serious and long-term risk is the possibility of reduction in crop yield from the continuous build-up of arsenic in the soil from arsenic contaminated ground water.