Proclaiming a "new era for clean air," President Bush yesterday signed into law sweeping controls designed to sharply reduce pollution from cars and factories by early next century.

The Clean Air Act Amendments of 1990, signed at an East Room ceremony, impose new, costly technological requirements or health standards on virtually every industrial sector in hope of restoring the atmosphere's protective ozone shield and combating urban smog, acid rain and cancer-causing plant emissions.

"This legislation isn't just the centerpiece of our environmental agenda," said Bush, fulfilling a campaign pledge as he signed the bill. "It is simply the most significant air pollution legislation in our nation's history."

The legislation closes a gaping hole in the nation's environmental laws, strengthening and expanding a statute allowed to erode since its last revision 13 years ago. Air quality deteriorated in the interim, with unhealthy levels of smog spreading to 100 cities, factory fumes exposing communities to unusually high cancer risks, acid rain taking a toll on forests and streams of the Northeast and the ozone layer thinning over Antarctica and parts of Europe and North America.

The law gives the federal government new and more potent weapons to battle those threats. Antipollution controls extending from coke ovens to bakeries are expected to cost industry $25 billion a year eventually to implement and raise consumer prices of everything from new cars to dry cleaning.

But under the law's timetable, it will take years before Americans begin to breathe easier. With cutbacks in auto pollution and requirements for cleaner gasoline delayed to accommodate industry, "seriously" smoggy cities, such as Washington, are not required to achieve health standards for nine years. More polluted places, such as Baltimore and Chicago, will take 15 and 17 years, respectively, to meet standards.

"Our kids will have kids of their own before they can play outside in the summer without health warnings," said Fran DuMelle of the American Lung Association.

For communities downwind of toxic emissions, partial relief will come as early as 1995 when controls for industrial sources of 41 pollutants must be installed and capable of cutting emissions at least 70 percent. But for sources of 148 other pollutants, including carcinogens, the deadline is 2003. And years more will be permitted to curb high cancer risks remaining after the initial round of controls.

Only the least damaged streams of New England are expected to benefit from the early years of acid rain controls. The program requires utilities to cut sulfur dioxide emissions 10 million tons, then cap them. But the reductions will be phased in slowly, meeting the goal in the year 2000.

"Given the political context, this is a defensible bill," environmentalist David Hawkins said. "From a 21st century perspective, it will not look very demanding."

But for businesses grappling with the oil shortage and threat of recession, the new law is far-reaching -- "it will dramatically change our lifestyles and the way most companies do business," said Bill Fay, lobbyist for an industry umbrella group.

The costs of those changes will be passed along to consumers, adding $100 to the price of new, cleaner cars in 1996; 10 cents per gallon for cleaner gasoline sold in the nine smoggiest cities; electricity rate hikes as high as 16 percent for customers of the dirtiest utilities in the Midwest, and uncertain price increases for small businesses such as bakeries and dry cleaners that emit newly regulated substances.

Fortunes of entire industries will shift under the new law. Producers of ethanol, a corn-based alcohol that reduces the oxygen content of gasoline, are headed for a boom. A 1992 requirement for higher oxygen content in fuels sold in 44 cities with the worst carbon monoxide is expected to double sales of ethanol by 1995. Acid rain controls are expected to ring up sales of $10 billion for companies that sell "scrubber" technology to take the sulfur out of power plant exhausts.

The same controls threaten the high sulfur coal industry in Appalachia and the Midwest, which is expected to lose 20 percent of its projected market in the year 2010 and lay off 5,500 miners. Low sulfur coal interests in the West will profit.

Yesterday's signing ceremony culminated 16 months of political struggle with a guest list reflecting the coalition that produced the law. Environmentalists sat near industry lobbyists. Longtime rivals who cooperated in the bill -- Reps. John D. Dingell (D-Mich.) and Henry A. Waxman (D-Calif.) -- were there, as was Senate Majority Leader George J. Mitchell (D-Maine.)