Mirex, the pesticide banned since 1977 because of its threat to human health, has been given a new life by the House Agriculture Committee.

In a surprise move Thursday, the committee voted to allow one-year "emergency" use of Mirex against pestiferous fire ants in the South. The bill now moves to the House floor where a move to strike it is expected.

Adoption of the proposal by Rep. Dawson Mathis (D-Ga.) came as the committee extended for another year the Fungicide, Insecticide and Rodenticide Act, which will expire this fall.

A similar extension of the act-without approval of Mirex-earlier had been adopted by the Senate Agriculture Committee.

The Mirex amendment, passed without hearings or debate, was one of three offered by Mathis that would severely curtail the authority of the Environmental Protection Agency which administers the act.

A second amendment would remove EPA from pesticide regulation by 1985 and a third would allow any EPA ban on pesticides to be overruled by vote of either the House of Senate. Both were passed by the committee.

"It's appalling, to say the least," said William Butler, attorney for the Environmental Defence Fund, an organization that has fought the use of Mirex and related pesticides for years.

"We think it is irresponsible of the committee to approve a pesticide whose cancellation was upheld only last month by the U.S. Court of Appeals in the 5th Circuit," Butler said.

The committee action seems certain to stir a spirited debate when the peticide act extension reaches the House floor. Southern legislators long have supported the use of Mirex and other potent pesticides against the growing fire ant infestation.

Mirex was banned by EPA and phased out of use by mid-1978 after the agency found that it caused cancer and birth defects in humans.

Use of a successor pesticide, ferriamicide, was approved by EPA this year but that action was delayed in February after it, too, raised questions about adverse effects on humans.

Meanwhile, EPA last week authorized the use of Diazinon and indicated several other pesticides would soon be approved for battling the fire ants.