WASHINGTON (AP) — The Supreme Court, stepping into an enormous environmental battle, today agreed to decide the fate of tougher federal regulations for curtailing smog and soot nationwide.

The justices said they will review a federal appeals court ruling that blocked the Environmental Protection Agency from enforcing clean-air standards it adopted in 1997, among the most contentious regulations ever issued by the Clinton administration.

The highest court's decision is expected sometime in 2001.

The dispute carries "profound implications for the health of the American public," government lawyers told the court.

The EPA says the tougher standards are needed to protect people with respiratory ailments, the elderly and children from the adverse health effects of dirty air.

The standards were successfully challenged by a large coalition of industry groups and three states — Michigan, Ohio and West Virginia.

A three-judge panel of the U.S. Circuit Court of the Appeals for the District of Columbia ruled by a 2-1 vote last year that the agency overstepped its authority. The appeals court panel said the EPA had interpreted the 1990 Clean Air Act "so loosely" that it unlawfully usurped Congress' legislative power.

The full appeals court voted 6-5 in October against reviewing the panel's decision.

The revised air standards limited the allowable level of ozone, an essential part of smog, to 0.08 parts per million, instead of the 0.12 parts per million under the old requirement. And states for the first time were required to regulate microscopic particulates, or soot, from power plants, cars and other sources down to 2.5 microns, or 28 times smaller than the width of a human hair.

The Clean Air Act authorizes the EPA to issue air quality standards to protect human health. The law says the agency may set pollution limits that "accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of a pollutant."

In its decision last year, the appeals court panel said the EPA "rightly recognizes that the question is one of degree but offers no intelligible principle by which to identify a stopping point."

The administration's Supreme Court appeal cited a 1989 decision in which the justices gave Congress considerable leeway in delegating its power. "A practical understanding that in our increasingly complex society, replete with ever-changing and more technical problems, Congress simply cannot do its job absent an ability to delegate power under broad general directives," the court said then.

Government lawyers aid the appeals court decision ignored that "crucial practical understanding," and by doing so "opened to potential constitutional attack ... numerous other federal statutes containing similarly broad grants of authority to administrative agencies."

Two states — Massachusetts and New Jersey — also appealed, as did the American Lung Association. The court left those appeals still pending, probably until a decision is reached on the EPA's appeal.

Industry groups filed cross-appeals that said the justices, if they review the appeals court's decision, should also review those portions of the ruling that freed the EPA from taking costs into account and rejected the groups' contention that the air-quality standards were based on incomplete and poor science.

The court also did not act on those cases.

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