The Environmental Protection Agency said yesterday it may delay approval of "emergency" use of a potent new pesticide to combat fire ants this spring in Mississippi.

A decision on use of the chemical ferriamicide will be made after EP A scientists review new Canadian research suggesting the pesticide may cause cancer and birth defects in humans. Ferriamicide is made of Mirex, a chemical banned by EP A as a potential health hazard.

EP A Deputy Administrator Barbara Blum on Jan. 30 approved the use of ferriamicide in Mississippi after almost a year of litigation by environmentalists and intense political pressure from southern members of Congress.

A report in yesterday's Washington Post provided details of the political campaign to approve the new fire ant pesticide and disclosed that the Mississippi approval occurred without consideration by EP A of the Canadian research.

The EP A yesterday called a press briefing and issued a three-page statement to denounce what Blum termed "very shallow treatment" of the pesticide report by The Post.

She denied that political considerations had taken precedence over the health aspects of ferriamicide use and said that the risks had been balanced carefully against the benefits of using the pesticide.

But the agency also announced that it is reopening the public comment period on its Mississippi decision and the comment period on applications by eight other southern states for emergency approval of ferriamicide applications to areas infested by the bothersome fire ants.

Steven D. Jellinek, an assistant administrator of EP A, said that EP A was unaware of the Canadian data during long deliberations on ferriamicide and that environmental opponents of the pesticide had not mentioned it before the comment period closed on Jan. 3.

EP A twice last year authorized the use of ferriamicide on a one-time-only basis in Mississippi, but litigation brought by the Environmental Defense Fund prevented the pesticide from being used.

Jellinek said the Canadian data is on its way to Washington and will be reviewed "immediately" by EP A scientists to determine if the Mississippi approval should be resinded.

"We have notified Mississippi that this additional information is on the way and that the spring application may have to be delayed," he said. "But I want our scientists to see the data. I am not recommending any decisions based on reports in the news paper, however reliable."