Letter▼ Limited accuracy of arsenic field test kit While we were monitoring arsenic removal filters in Nawalparasi, Nepal, it became evident that the arsenic field test kits are not completely reliable for measuring arsenic in natural groundwaters at levels close to the critical regulatory arsenic concentrations of 10 ppb (the World Health Organization’s recommended limit for drinking water) and 50 ppb (the regulatory limit for drinking water set by the governments of Bangladesh, Nepal, India, and Cambodia). We investigated the problem by splitting water samples. Half of each sample was analyzed in the field by a commonly used arsenic field test kit, while the other half was preserved and sent to a certified laboratory for cross-checking. The atomic adsorption hydride generation method was used to analyze the laboratory samples. Samples measured with the field test kit gave arsenic concentrations of 10, 0–10, 10, 25–50, 50–100, 50–100, 50–100, 175–500, 100–250, and 500 ppb, but those tested in the laboratory yielded concentrations of 145, 38, 67, 165, 240, 200, 110, 680, 510, and 473 ppb, respectively. A comparison of the data shows that at arsenic concentrations
