WASHINGTON (AP) _ A Senate committee is looking into a report that says the Bush administration is hampering the ability of Environmental Protection Agency scientists to assess the health dangers of toxic chemicals.

The head of the EPA's pesticide and toxic chemical office was to testify Tuesday before the Senate Environment and Public Works Committee, along with an official of the Government Accounting Office that has just concluded an investigation of the EPA's chemical risk assessment program.

The GAO report, obtained by The Associated Press, said the EPA's ability to conduct timely, science-based risks assessments was being undermined by allowing greater involvement in the process by nonscientists, often in secret.

The administration's decision to give the Defense Department and other agencies an early role in the process adds to years of delay in acting on harmful chemicals and jeopardizes the program's credibility, the GAO concluded.

At issue is the EPA's screening of chemicals used in everything from household products to rocket fuel to determine whether they pose serious risk of cancer or other illnesses.

A review process begun by the White House in 2004 and imposed formally by the EPA earlier this month is adding more speed bumps for EPA scientists, the GAO said in its report.

GAO investigators said extensive involvement by EPA managers, White House budget officials and other agencies has eroded the independence of EPA scientists charged with determining the health risks posed by chemicals.

Many of the deliberations over risks posed by specific chemicals "occur in what amounts to a black box" of secrecy because the White House claims they are private executive branch deliberations, the report said.

The Pentagon, the Energy Department, the National Aeronautics and Space Administration and other agencies all of which could be severely affected by EPA risk findings are being allowed to participate "at almost every step in the assessment process," the GAO said.

Those agencies, their private contractors and manufacturers of the chemicals could face new restrictions on using the chemicals and be saddled with major cleanup requirements, depending on the EPA's scientific determinations. The risks data is widely used by EPA and states to determine levels of regulation and cleanup standards.

"By law the EPA must protect our families from dangerous chemicals," said Sen. Barbara Boxer, D-Calif., the Senate committee's chairwoman. "Instead, they're protecting the chemical companies."

The EPA's risk assessment process "never was perfect," Boxer said in an interview Monday. "But at least it put the scientists up front. Now the scientists are being shunted aside."

The White House said the GAO is wrong in suggesting that the EPA has lost control in assessing the health risks posed by toxic chemicals.

"Only EPA has the authority to finalize an EPA assessment," Kevin F. Neyland, deputy administrator of the White House budget office's Office of Information and Regulatory Affairs, wrote in response to the GAO. He called the interagency process "a dialogue that helps to ensure the quality" of the reviews.

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