HARRISBURG — Petroleum services giant Halliburton said today it has begun publicly disclosing the identity of chemicals in solutions it makes to be pumped into the ground by Pennsylvania’s booming natural gas industry.

A new Halliburton website provides information on the chemicals the company says are in its three most commonly used solutions in the state, where drilling crews are rushing to exploit the Marcellus Shale, the biggest known deposit of natural gas in the nation.

Halliburton does not say how much of each chemical has been pumped into the ground or identify the wells where they are used, nor does it reveal the exact concentration of each chemical in an overall solution. In general, water makes up the lion’s share. Sand comprises about 6 percent while chemical cocktails amount to less than 2 percent.

Many of the chemicals, including hydrochloric acid, methanol and acetic acid, are toxic in high enough doses, and appear in everyday household and industrial solvents, cleaners and adhesives.

“We think it’s a great first step,” Halliburton spokeswoman Teresa Wong said.

Last week, the federal Environmental Protection Agency issued a subpoena to Halliburton, seeking a description of the chemical components used in its hydraulic fracturing, or fracking, solutions that are used to break up the shale and release the natural gas deposits. The EPA said Halliburton refused to voluntarily disclose the chemicals, while eight other major energy companies complied.

Halliburton responded that it has worked to supply the EPA with the information it wants.

By The Associated Press