Washington ? At the White House’s direction, the Environmental Protection Agency gave New Yorkers misleading assurances that there was no health risk from the debris-laden air after the World Trade Center collapse, according to an internal inquiry.

President Bush’s senior environmental adviser on Friday defended the White House involvement, saying it was justified by national security.

The White House “convinced EPA to add reassuring statements and delete cautionary ones” by having the National Security Council control EPA communications in the wake of the Sept. 11 terror attacks, according to a report issued late Thursday by EPA Inspector General Nikki L. Tinsley.

“When EPA made a Sept. 18 announcement that the air was ‘safe’ to breathe, the agency did not have sufficient data and analyses to make the statement,” the report says, adding that the EPA had yet to adequately monitor air quality for contaminants such as PCBs, soot and dioxin.

In all, the EPA issued five press releases within 10 days of the attacks and four more by the end of 2001 reassuring the public about air quality. But it wasn’t until June 2002 that the EPA determined that air quality had returned to pre-Sept. 11 levels — well after respiratory ailments and other problems began to surface in hundreds of workers cleaning dusty offices and apartments.

The day after the attacks, former EPA Deputy Administrator Linda Fisher’s chief of staff e-mailed senior EPA officials to say that “all statements to the media should be cleared” first by the National Security Council, which is Bush’s main forum for discussing national security and foreign policy matters with his senior aides and Cabinet, the report says.

Approval from the NSC was arranged through the White House Council on Environmental Quality, which “influenced, through the collaboration process, the information that EPA communicated to the public through its early press releases when it convinced EPA to add reassuring statements and delete cautionary ones.”

For example, the inspector general found, EPA was convinced to omit guidance for cleaning indoor spaces and tips on potential health effects from airborne dust containing asbestos, lead, glass and concrete.