LOST HILLS, CA - MARCH 24: Pump jacks are seen at dawn in an oil field over the Monterey Shale formation where gas and oil extraction using hydraulic fracturing, or fracking, is on the verge of a boom on March 24, 2014 near Lost Hills, California. Critics of fracking in California cite concerns over water usage and possible chemical pollution of ground water sources as California farmers are forced to leave unprecedented expanses of fields fallow in one of the worst droughts in California history. Concerns also include the possibility of earthquakes triggered by the fracking process which injects water, sand and various chemicals under high pressure into the ground to break the rock to release oil and gas for extraction though a well. The 800-mile-long San Andreas Fault runs north and south on the western side of the Monterey Formation in the Central Valley and is thought to be the most dangerous fault in the nation. Proponents of the fracking boom saying that the expansion of petroleum extraction is good for the economy and security by developing more domestic energy sources and increasing gas and oil exports. (Photo by David McNew/Getty Images)

WASHINGTON -- The Environmental Protection Agency is requesting public comments on how it might go about "enhancing transparency for chemicals and mixtures used in hydraulic fracturing."

Hydraulic fracturing, often called fracking, uses high-pressure blasts of a mixture of water, chemicals and sand to break into shale rock formations and release the oil and natural gas contained therein. On Friday, the EPA issued what is known as an "advance notice of proposed rulemaking" -- in other words, a heads up that the agency is looking at new regulations for the disclosure of chemicals used in fracking. Those chemicals have become a contentious subject as natural gas development has boomed in the United States, with citizens and environmental activists calling for mandatory disclosure.

In its announcement, the EPA said it is seeking comments on "what information could be reported and disclosed for hydraulic fracturing chemicals and mixtures and the approaches for obtaining this information, including non-regulatory approaches." The comment period is open to the public and will last for 90 days. The full notice is available online.

Many companies that use fracking fluids have claimed that their mixtures are proprietary information and that it would put them at a competitive disadvantage to disclose them. The industry started its own voluntary disclosure program, FracFocus, in 2011, but many companies have opted for partial disclosure.

Some states, such as Wyoming and Colorado, have passed their own rules requiring disclosure, and similar rules are under consideration in other states.

"Today's announcement represents an important step in increasing the public's access to information on chemicals used in hydraulic fracturing activities," said James Jones, EPA's assistant administrator for the Office of Chemical Safety and Pollution Prevention, in a statement Friday. Jones said the agency would seek to "ensure that we complement but not duplicate existing reporting requirements."

Steve Everley, a spokesman for Energy In Depth, a program of the Independent Petroleum Association of America, said via email that the state and voluntary programs are already providing increased disclosure.

"States across the country already have strong disclosure requirements, chiefly through the use of FracFocus.org, which even the Obama administration has praised for providing transparency to the general public," said Everley. "I imagine none of that will ever be good enough for most of the groups who pushed EPA into this process, though."

A coalition of environmental, community and religious groups had filed a petition asking the EPA to regulate fracking chemicals back in August 2011. The headline on an Environmental Defense Fund blog post about Friday's announcement called it "better late than never."