WASHINGTON — The Environmental Protection Agency tightened the nation’s soot standards by 20 percent Friday, a move that will force communities nationwide to improve air quality by the end of the decade while making it harder for some industries to expand without strict pollution controls.
The new rule limits soot, or fine particulate matter, which stems from activities from burning wood to vehicle emissions, and which causes disease by entering the lungs and bloodstream.
Fine particulate matter measuring less than 2.5 micrometers in diameter, or one-thirtieth the width of a human hair, ranks as the nation’s most widespread deadly pollutant.
The new regulation results from a 2009 court ruling that said the EPA standards for the amount of soot permissible in the air on an annual average ignored the advice of scientific advisers by maintaining the standard established in 1997 and must be rewritten. That limit was 15 micrograms per cubic meter of air.
The EPA has decided to cut the level to 12 micrograms per cubic meter.
The soot rule ‘‘is among the most critical standards that EPA could set’’ because it triggers a series of measures local governments must take to comply or risk facing federal penalties, said Clean Air Watch president Frank O’Donnell.
The rule is significant because once areas are found in violation, it becomes harder for new pollution sources, such as industrial facilities and power plants, to get operating permits. While the federal government offers several incentives to reduce soot — such as money to phase out dirty diesel school buses — funding for these initiatives is in short supply.
The agency will determine which areas are out of compliance in 2014, and these communities will then have six years to comply. According to people familiar with the rule, 66 out of 3,033 counties will be found in violation of the new standard, though EPA projects seven will be out of compliance by 2020.
Air concentrations of soot can vary widely. In Pittsburgh’s Liberty-Clairton neighborhood, the annual average is 15 micrograms per cubic meter; in more bucolic Harrisonburg, Va., near Shenandoah National Park, it averages 10.2. An estimated 17.3 million Americans are living in areas that do not meet the soot standard of 15.
The EPA issued a draft rule in June, and faced a court-ordered deadline of Dec. 21 to finalize it. EPA picked the more stringent standard of the choices laid out in the draft rule.
The agency sent the final rule to the Office of Management and Budget on Dec. 11, and business groups have been scrambling to alter it during the past week.
Several trade groups — including the National Association of Manufacturers, the American Chemistry Council, and the Rubber Manufacturers Association — had less than one day’s notice to respond to the OMB on Wednesday. They argued that the EPA could protect public health and minimize economic harm with a more lenient standard of between 13 and 15 micrograms per cubic meter.
Ross Eisenberg, NAM’s vice president for energy and resources policy, said in a conference call Thursday the stricter rule will raise the cost of doing business in the United States.
‘‘It is impossible to ignore that, against the backdrop of a still-fragile economy and a looming fiscal crisis, EPA is heaping another new set of costs and burdens on manufacturers.’’ he said.
But Brooke Suter, who heads the Clean Air Task Force’s diesel cleanup campaign, noted that the EPA’s own scientific advisory panel said that a standard that would protect public health would range between 11 and 13 micrograms per cubic meter, and that the Clean Air Act requires the EPA to base the rule on scientific rather than economic considerations.
Her group has estimated a soot limit of 12 micrograms would save 15,000 lives a year by the time the rule takes full effect in 2020.