The U.S Environmental Protection Agency adopted a stricter smog limit Thursday that will force states to reduce emissions over the next decade, improving respiratory health for millions of people through pollution controls that will cost industry billions of dollars.

EPA Administrator Gina McCarthy issued a new standard strengthening limits on ground-level ozone to 70 parts per billion, down from the 75-ppb standard adopted in 2008 by the Bush administration.

The tighter restrictions will have the greatest impact in California because the state has the nation’s worst air quality and has failed to meet previous ozone standards.

The EPA’s long-delayed decision disappointed public health advocates and environmentalists, who had endorsed a 60-ppb standard. They said they were likely to challenge the EPA in court for selecting the weakest option under consideration.


“The big polluters won this time, for the most part,” said Frank O’Donnell, president of the advocacy group Clean Air Watch. “This is truly a blemish on the president’s environmental legacy.”

Industry groups, which waged a fierce lobbying and advertising campaign against new ozone rules, predicted they would stifle economic growth, with power plants, factories and other businesses bearing the burden of costly new controls.

The National Assn. of Manufacturers called the revised standard “a punch in the gut” to companies across the country. But the association said a “worst-case scenario was avoided” when the Obama administration chose against the lower proposed standard.

Jay Timmons, the association’s president, said, “The new ozone standard will inflict pain on companies that build things in America — and destroy job opportunities for American workers.”


Public health advocates, environmentalists and President Obama have pointed to decades of improvements in air quality in California and other states as proof that you can curb pollution without dragging down the economy. The EPA said air pollution has declined by 70% since 1970, while gross domestic product has tripled.

Meeting the new smog limit by 2025 will prevent hundreds of thousands of asthma attacks and missed school days for children and hundreds of early deaths from cardiovascular disease and other illnesses, according to the EPA.

The cost savings from those health benefits will outweigh the billions of dollars in annual costs to industry by about 4 to 1, the agency said.

McCarthy’s predecessor at the EPA, Lisa Jackson, had recommended tightening the standard to 65 parts per billion during Obama’s first term. But the president set aside the proposal four years ago at the start of his reelection campaign amid industry opposition, citing regulatory burdens on the recovering economy. That decision left the Bush-era limit in place.


On Thursday, McCarthy defended the 70-ppb standard, telling reporters that it was based on the law and science, not politics. The Clean Air Act obligated her to adopt an ozone limit “no more or less stringent than necessary to protect at-risk groups,” she said.

McCarthy said the standard reflects the agency’s review of thousands of studies, including some that raised uncertainties about the effects of ozone exposure below 70 ppb.

The lowest level that decreased lung function in healthy, exercising adults was 72 parts per billion, she said. The new standard “will essentially eliminate exposures to that level that clinical studies show to be harmful.”

The new smog rules will not go into effect for several years, giving states until 2017 to collect air quality data and determine their status and several more years to devise plans to cut pollution. The EPA projects that all but 14 counties outside California will meet the new limit by 2025.


The EPA will give California until 2037, 12 years longer than the rest of the country, to meet the new standard.

Sen. Barbara Boxer (D-Calif.) said the EPA’s action “is a step in the right direction, but I believe following the science is important, and I am disappointed that a more protective standard was not set.”

Politicians have been wary of tighter standards on ozone because of the economic implications of further reductions in the country’s most widespread air pollutant.

Rep. Fred Upton (R-Michigan), chairman of the House Energy and Commerce Committee, warned that it could be the “last straw for our fragile economy.” House Majority Leader Kevin McCarthy (R-Bakersfield), who is expected to become the new House speaker, said the rule was “all pain for little gain.”


As part of the changes, the federal government will update the nation’s color-coded Air Quality Index to reflect the more stringent limits. Health experts have long complained that the index classifies the air in many regions as healthful when it is not.

Ozone forms when pollution from cars and trucks, factories and power plants cook in the heat and sunlight. Ozone levels are influenced by so many different pollution sources that controlling them requires emissions reductions from a wide variety of places, including vehicles, manufacturing facilities and consumer products.

The Clean Air Act requires the EPA to set pollution standards at levels that protect public health “with an adequate margin of safety,” including protections for children, the elderly and others who are more sensitive to air pollution. The EPA is prohibited from considering cost when establishing the limits on ozone and other pollutants, but can factor in costs when determining how the states carry out the rules.

Tens of millions of Americans live where ozone levels are too high. The problem is worst in California, where about one-third of residents live in communities with pollution that exceeds federal standards, according to recent estimates by state officials. The smoggiest cities in the country are in Southern California and the Central Valley.


Meeting the standard in California will require steep emissions cuts falling most heavily on the transportation sector, which will need many more electric or zero-emissions cars in addition to cleaner trains, trucks, ships and airplanes.

The new standard will throw several rural counties in California out of compliance, including Amador, Tehama and Tuolumne. They will add to the 16 counties that do not currently meet ozone standards, according to the state Air Resources Board.

Squeezing additional emissions cuts from factories, power plants and vehicles will be difficult because of population growth, development and increases in driving miles, air quality officials say. But state officials plan to fight smog with some of the same regulations they are relying on to address climate change, including cleaner fuel requirements, renewable electricity mandates and emissions standards to require cleaner trucks and more electric vehicles.

The new smog limit cannot be attained in Southern California without tougher emissions standards for ocean vessels, locomotives, airplanes and other pollution sources that only the federal government has the power to regulate, said officials with the South Coast Air Quality Management District, which oversees Los Angeles, Orange, Riverside and San Bernardino counties.


tony.barboza@latimes.com

Twitter: @tonybarboza

Times staff writer Michael A. Memoli in Washington contributed to this report. Barboza reported from Los Angeles.