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Around 150 million people in more than 70 countries around the world are exposed to elevated levels of naturally occurring arsenic in groundwater used for drinking and cooking. Inexpensive arsenic field test kits are readily commercially available and have been promoted for classifying the safety of water sources. However, the accuracy and reliability of test kits has been called into question by some researchers. The purpose of this project was to provide decision support to a small nonprofit community development organization in central Mexico regarding the applicability of field test kits for assessing the safety of rural groundwater supplies. Test kit evaluation was conducted as an experiential learning exercise for undergraduate and graduate students in a University engineering course on Global Water and Sanitation. Recounting the scale and scope of the ongoing arsenic crisis in Bangladesh, as well as the sensational epidemic of "arsenical beer" in Manchester, England in 1900 that popularized the Gutzeit chemistry upon which test kits are based, spurred student interest and enthusiasm for the learning activities. Reviewing the contradictory and inconclusive literature from the recent two decades on the use of test kits provided a sobering case study for students to grapple with the difficulties and uncertainties inherent in conducting humanitarian science and engineering in the developing world. This study found generally poor performance of test kits, in particular for waters containing As in excess of 95 µg/L. Additionally, the field kits tested could not be used to classify waters as "safe," i.e., below the WHO Guideline Value of 10 µg/L to 95% level of confidence. This study lends further caution to the use of test kits for identification of safe water sources. [ABSTRACT FROM AUTHOR]