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About 47% of Nepal's total population is living in Terai region and 90% of them are relying on groundwater as their major source of drinking water. About 200,000 shallow tubewells have been installed by different agencies in 20 Terai districts, serving 11 million people. Recently, arsenic contamination of groundwater has been recognized as a public health problem in Nepal. This has sensitized government, national and international nongovernment organizations working on water quality sector to carry out water quality assessment for arsenic in the affected communities. So far, 15,000 tubewells has been tested where 23% samples exceeded World Health Organization guideline value of 10 microg/L and 5% exceeded "Nepal Interim Arsenic Guideline" of 50 microg/L. It is estimated that around 0.5 million people in Terai are living at risk of arsenic poisoning (>50 microg/L). Some recent studies have reported the prevalence of dermatosis related to arsenicosis from 1.3 to 5.1% and the accumulation of arsenic in biological samples like hair and nail much higher than the acceptable level. Though some steps are being taken by government and private organizations to combat the problem, it has not been able to cover all the affected communities. Nepal still needs more research work on arsenic occurrence and effects and mitigation programs simultaneously.

In Nepal, the National Arsenic Steering Committee has reported the Nawalparasi district as a high-risk area for groundwater contamination by arsenic. One type of shallow well, the seesaw well, is most popular among the farmers due to its large water pumping capacity under manual operation. About 600 seesaw wells exist for irrigation water extraction for vegetable farming in the district. However, the wells have not yet been tested for arsenic. Therefore, this study was performed to generate preliminary data on arsenic contamination of the irrigation water of the three Villages: Manari, Devgaoun and Sukrauli. Some 100 water samples were collected from those wells and analyzed for total arsenic content immediately, using an ENPHO field test kit. From these, 52 samples (52%) were randomly selected for arsenic speciation and for the analysis of total arsenic by Atomic Adsorption Spectroscopy. The results show that the arsenic concentration in 65% of the wells exceeded 50 mg l 71 and in 36%, 100 mg l 71 . A calculation of soil contamination based on these data (n ¼ 52) revealed an increase in arsenic contamination to soil ranging from about 0.04 mg kg 71 to 10.19 mg kg 71 per year.

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