The Senate Environment and Public Works committee yesterday voted to reduce the requirements under which a new industry can move into a region that currently is not meeting clean air standards.

By a 7-to-6 vote, the committee adopted an amendment by Sen. Lloyd M. Bentsen Jr. (D-Tex) under which the Environmental Protection Agency could allow new industry into a so-called "dirty air area" if the state could show "reasonable progress" toward meeting clean air standards.

Currently, a new industry moving into such an area is required to reduce existing pollution by the amount the new industry would contribute. That means it has to shut down an existing polluter or get other polluters to decrease their dirty air.

Areas that don't meet federal clean air standards, which includes most large urban areas with industrial facilities, would be required to come up to those standards by 1979 under existing law. The committee was considering an extension of that deadline until 1982 for most pollutants and until 1987 for oxidants, when Bentsen offered his amendment.

After the session, environmentalists threatened to withdraw support for any clean air bill containing the Bentsen amendment. "We'll fight vigorously any bill that comes out from committee with that in it," said Rafe Pomerance, legislative coordinator or the National Clean Air Coalition, an umbrella organization of environmentalist groups.

Pomerance said the action amounts to a "freeze" that would prevent air quality from getting any better in any dirty air region.

David Hawkins of the Natural Resources Defense Council said this would allow "steel plants to expand in areas where the particulate standards have not been attained and power plants to expand in areas where sulfur dioxide standards have not been attained."

Bentsen had argued that it would be unreasonable to require assured attainment of standards that cities could not possibly meet.

He said that the Houston area could shut down all existing plants and not meet the standards. "If you stopped every industry in the Houston-Beaumont area . . . and if you stopped every car and made people walk . . . you would still exceed the oxidants standards," Bentsen said. He said there was nothing wrong with allowing states a little more flexibility "so long as you get to the same target."

Under the present policy, administered by the Environmental (Protection Agency, a new industry is required to find other polluting sources in the regions to shut down or modify before it could locate in one of those dirty air areas.

The problem in Houston is oxidants or photochemical smog, produced by a combination of auto emissions and petrochemical plants.

Bentsen said his amendment gives air quality regions that are in violation of clean air standards an option of either showing "reasonable further progress" on a yearly basis, or of complying with the trade-off requirement.

But Sen. Edmund S. Muskie (D-Maine) said, "The deadline is eliminated. What then becomes reasonable? If you do that, you ought to consider rewriting the act. If you don't have deadlines, you don't have" firm clean air standards.

The committee was expected to report out the clean air bill today, but adjourned in some confusion ofter the vote as staffers and senators debated exactly what the effect of Bentsen's amendment was. No date for another markup session has been set.