PITTSBURGH — A major supplier to the oil and gas industry says it will begin disclosing 100 percent of the chemicals used in hydraulic fracturing fluid, with no exemptions for trade secrets. The move by Baker Hughes of Houston is a shift for a major firm; it's unclear if others will follow suit.

The oil and gas industry has said the chemicals used are disclosed at tens of thousands of wells, but environmental and health groups and government regulators say a loophole that allows companies to hide chemical "trade secrets" has been a major problem.

A statement on the Baker Hughes website said the company believes it's possible to disclose 100 percent "of the chemical ingredients we use in hydraulic fracturing fluids without compromising our formulations," to increase public trust.

"This really good news. It's a step in the right direction," said Dr. Bernard Goldstein, the former dean of the University of Pittsburgh Graduate School of Public Health.

Goldstein said the Baker Hughes language sets a new standard for transparency and "clearly distinguishes them from Halliburton," another major industry supplier. A Halliburton spokeswoman did not immediately respond to requests for comment.