The Environmental Protection Agency issued a subpoena to compel Halliburton...to provide complete information on hydraulic fracturing... Halliburton remained the only company of nine that did not fully comply with a September request to provide the information voluntarily, according to EPA...The EPA is under a congressional mandate to study potential adverse effects on drinking water and public health posed by hydraulic fracturing, which has been used extensively in the west...The agency is seeking information on the chemical ingredients of fluids used in the process, as well as data on the effects of the chemicals on human health and the environment...and the locations of sites where fracturing has been conducted. A Halliburton spokeswoman said the company had already turned over 5,000 pages to the EPA and was "disappointed" with the EPA's decision, but was working with the agency to narrow the scope of its request...