New clean air standards announced by the U.S. Environmental Protection Agency on Friday could be tough for some Valley counties to meet.

The new nationwide standard allows no more than 12 micrograms of harmful fine particle pollution – particles smaller than 2.5 micrometers, like soot – in a cubic meter of air.

That PM2.5 can lead to plaque deposits in arteries, leading to vascular inflammation and atherosclerosis, according to the American Medical Association. The World Health Organization says the particles lead to cardiopulmonary disease, cancer of the trachea, bronchus, and lung, and acute respiratory infections.

“These standards are fulfilling the promise of the Clean Air Act,” said EPA Administrator Lisa P. Jackson. “We will save lives and reduce the burden of illness in our communities, and families across the country will benefit from the simple fact of being able to breathe cleaner air.”

The EPA was required to update the PM2.5 standard by a recent federal court ruling. The updated standard is based on the “best available science,” per the EPA. Public input was taken prior to the change, including two public hearings and more than 230,000 written comments.

According to the EPA, 99 percent of all American counties will meet the new standard with no changes. But all seven counties expected not to meet the 12 microgram per cubic meter requirement by 2020 are located within California.

Three Valley counties – Merced, Tulare, and Kern Counties – are projected not to meet the revised standard by 2020. All other counties projected not to meet the standard – Los Angeles, San Bernardino, Riverside, and Imperial Counties – are located in Southern California.

Stanislaus County is already below the new requirement, according to the EPA.