Fracking a single well requires up to 7 million gallons of water, plus an additional 400,000 gallons of additives, including lubricants, biocides, scale and rust inhibitors, solvents, foaming and defoaming agents, emulsifiers and de-emulsifiers, stabilizers and breakers. About 70 percent of the liquid that goes down a borehole eventually comes up—now further tainted with such deep-earth compounds as sodium, chloride, bromide, arsenic, barium, uranium, radium and radon. (These substances occur naturally, but many of them can cause illness if ingested or inhaled over time.) This super-salty “produced” water, or brine, can be stored on-site for reuse. Depending on state regulations, it can also be held in plastic-lined pits until it evaporates, is injected back into the earth, or gets hauled to municipal wastewater treatment plants, which aren’t designed to neutralize or sequester fracking chemicals (in other words, they’re discharged with effluent into nearby streams).