"Frack Secrets by Thousands Keep U.S. Clueless on Wells"
"A subsidiary of Nabors Industries Ltd. pumped a mixture of chemicals identified only as “EXP- F0173-11” into a half-dozen oil wells in rural Karnes County, Texas, in July. Few people outside Nabors, the largest onshore drilling contractor by revenue, know exactly what’s in that blend. This much is clear: One ingredient, an unidentified solvent, can cause damage to the kidney and liver, according to safety information about the product that Michigan state regulators have on file."