WASHINGTON (AP) — In a dramatic reversal, President Barack Obama has scrubbed a clean-air regulation aimed at reducing health-threatening smog.Today's decision yields to bitter protests from businesses and congressional Republicans who complained the rule would kill jobs in America's ailing economy.Withdrawal of the proposed regulation marked the latest in a string of retreats by the president in the face of GOP opposition, and it drew quick criticism from liberals. Environmentalists accused him of caving to corporate polluters, and the American Lung Association threatened to restart the legal action it had begun against rules proposed by President George W. Bush.The White House has been under heavy pressure from GOP lawmakers and major industries, which have slammed the stricter standard as an unnecessary jobs killer.The Environmental Protection Agency's scientific advisers favored the tighter limits. The EPA had predicted the proposed change would cost up to $90 billion a year, making it one of the most expensive environmental regulations ever imposed in the U.S. But the Clean Air Act bars the EPA from considering the costs of complying when setting public health standards.Obama said his decision was made in part to reduce regulatory burdens and uncertainty at a time of rampant questions about the strength of the U.S. economy. Underscoring the economic concerns: a new report Friday that showed the economy essentially adding no jobs in August and the unemployment rate stubbornly stuck at 9.1 percent.