WASHINGTON — The U.S. Supreme Court dealt a setback to a group of industries that mounted a court challenge to EPA air-quality rules on ozone and particulate pollution, as the high court said the EPA does not have to weigh the cost of such rules to industry. But the court gave businesses a partial victory, ordering the EPA to reconsider rules setting a timetable for ozone-pollution reduction in areas of the country with the worst pollution.

The group seeking to overturn the EPA rules includes the National Paint & Coatings Association (NPCA) and represents more than 20 industries.

The EPA in 1997 enacted tougher standards on ozone pollution, or smog, and airborne particulates. The ozone-pollution standard could significantly expand the size of geographic areas that are not in compliance with federal air-quality rules, triggering increased restrictions on emissions from autos and industries.

In its ruling, the Supreme Court reversed a federal appeals-court decision that had struck down the new EPA regulations on the grounds that Congress had not given the agency clear guidance to enact the new standards. The high court also rejected industry arguments that the EPA should have considered the estimated $50 billion in annual compliance costs that the new rules could generate to businesses and consumers.

NPCA representatives said that despite the ruling sending the case back to the appeals court, the Supreme Court action could lead to a lower-court decision striking down the EPA standards on the grounds that the agency cannot demonstrate that the regulations would enhance the protection of public health. On the other hand, the ruling also could “embolden EPA to push across-the-board lower basic Clean Air Act standards,” said NPCA Vice President and General Counsel Thomas Graves.

“At this time, it is not known what the direct impact will be on the paint and coatings industry,” Graves said.