Controversy over hydraulic fracturing fluids and their possible effect on drinking water demonstrates the boundless human capacity for inconsistency.Although chances are low that injected frac fluid will find its way down anyone's throat, fear persists in parts of the US about contamination of subsurface drinking water.It persists despite the tens of thousands of frac jobs producers have performed over 60 years without fouling groundwater.And it persists despite explanations about vertical separation between injection targets and freshwater aquifers, about mechanical controls that keep injectants from entering sensitive strata, and about regulations in place to ensure safe work.A reason t...