Arsenic, cancer, and thoughtless policy

The current drinking water contaminant standard for arsenic is 50 μg/L, as an upper bound. There is no lower bound for the standard. In an analysis of three epidemiology studies, the author demonstrates a significant cancer incidence trough for arsenic near 50 μg/L. Allowing, and even requiring, a much lower arsenic standard is not a desirable health outcome. Since most water systems currently deliver arsenic at levels below 5 μg/L, an undesirable health outcome is expected. For these systems and others not near 50 μg/L, the level of arsenic should be adjusted to bring it near 50 μg/L.