An effort to create standardized autopsy guidelines that could document the link between toxic air at ground zero and the later deaths of Sept. 11 rescue workers was abandoned by the federal government over concerns that the information collected could be misinterpreted.

The National Institute for Occupational Safety and Health, in a note posted Friday on its web site, said the agency "instead will pursue other avenues for documenting long-term health effects from exposure to air contaminants from the World Trade Center disaster."

The proposal for standard autopsy guidelines was laid out by the institute in a Sept. 15 draft document that was subsequently reviewed by medical experts outside the federal government. The decision to scratch the autopsy plan came after the experts raised questions about whether the plan would work.

"This study has many insurmountable barriers to overcome," wrote Dr. David J. Prezant, chief medical officer for the city Fire Department. Prezant, whose review was also posted on the institute web site, said one of those barriers was the "politics of causality," a reference to pending lawsuits filed against the city by injured workers. Autopsy results are often used in civil suits.

The institute said reviewers had raised several questions about the program, including concerns that "the draft document could be misinterpreted or misapplied, hindering rather than furthering progress in addressing WTC health concerns." The independent reviews were complete on Oct. 31, according to the institute.

The draft had proposed examining specific sections of the lungs, along with the creation of a "tissue bank" to preserve certain organs and bodily fluids for later testing. But the agency ultimately decided to look for another method to reduce "uncertainties in assessing WTC health effects."

The five-paragraph web site statement contained no specific alternatives.

The collapse of the twin towers sent thick plumes of concrete dust, fiberglass, asbestos and lead into the air in lower Manhattan. The tainted air was taken in by thousands of ground zero workers in the weeks after the terrorist attack that killed 2,749 people.

The guidelines were intended to be used nationwide in cases like the death of New York City police detective James Zadroga, who died last January. Zadroga spent 470 hours working amid the toxic fumes, and fell ill within weeks.

An autopsy found the 34-year-old detective died as a result of ground zero exposure, finding that there was material "consistent with dust" found in his lungs.