Advocacy groups have filed a petition asking U.S. federal regulators to draft rules requiring energy companies to list substances used in fracking fluid. The Environmental Defense Fund said more than 100 groups filed a petition on hydraulic fracturing, or fracking, with the U.S. Environmental Protection Agency. Fracking requires the blasting of high-pressure fluids mixed with chemicals and abrasives into shale deposits to extract natural gas.Megan Klein, an attorney with advocacy group Earthjustice, said the EPA needs to act now because new problems allegedly associated with fracking occur almost daily. \"The more information we have about the chemicals used in fracking and drilling, the easier it will be to keep people safe and healthy,\" she said in a statement. The EDF maintains that little is known about what chemicals are used in fracking fluid. Operators in Michigan under measures passed in May are required to list characteristics of the chemical additives used in fracking fluid. West Virginia, Texas and others have passed similar regulatory measures regarding shale.The EPA in July said it would conduct studies on the potential impact shale fracking has on drinking-water aquifers.