All of Bangladesh’s approximately 10,000,000 drinking water tubewells must be periodically tested for arsenic (As). The magnitude of this task and limited resources of Bangladesh has led to the use of low-cost, semi-quantitative field kits that measure As to a relatively high 50-µg/L national drinking water standard. However, there is an urgent need to supplement and ultimately replace these field kits with an inexpensive laboratory method that can measure As to the more protective 10-µg/L World Health Organization (WHO) health-based drinking water guideline. Unfortunately, Bangladesh has limited access to atomic absorption spectrometers or other expensive instruments that can measure As to the 10-µg/L WHO guideline. In response to this need, an inexpensive and highly sensitive laboratory method for measuring As has been developed. This new method is the only accurate, precise, and safe way to quantify As to less than 10 µg/L without expensive or highly specialized laboratory equipment. In this method, As is removed from the sample by reduction to arsine (AsH3) gas, collected in an absorber by oxidation to arsenic acid (H3AsO4), colorized by a sequential reaction to arsenomolybdate, and quantified by spectrophotometry. This method was compared to the silver diethyldithiocarbamate (AgSCSN(CH2CH3)2) and graphite furnace atomic absorption spectroscopy (GFAAS) methods for measuring As. Our method is more accurate, precise, and environmentally safe than the AgSCSN(CH2CH3)2 method. Our method is more accurate and affordable than GFAAS. Finally, this study suggests Bangladeshis will readily share drinking water with their neighbors to meet the more protective 10-µg/L WHO guideline for As.