WASHINGTON — The Environmental Protection Agency announced a new standard for soot pollution on Friday that will force industry, utilities and local governments to find ways to reduce emissions of particles that are linked to thousands of cases of disease and death each year.

The agency, acting under a court deadline, set an annual standard of 12 micrograms per cubic meter of air, a significant tightening from the previous standard of 15 micrograms, set in 1997, which a federal court found too weak to adequately protect public health. The new standard is in the middle of the range of 11 to 13 micrograms per cubic meter that the E.P.A.’s science advisory panel recommended.

Communities must meet the new standard by 2020 or face possible penalties, including loss of federal transportation financing.

The E.P.A. based its action on health studies that found that exposure to fine particles — in this case measuring 2.5 micrometers in diameter — brought a marked increase in heart and lung disease, acute asthma attacks and early death. Older people, adults with heart and lung ailments and children are particularly susceptible to the ill effects.