The Tacoma area on Thursday officially received a dirty air designation from the federal Environmental Protection Agency, which branded it as one of 31 most polluted places in the country.

The formal federal designation as a “non-attainment area” is new, but the data behind it are not. The EPA listing is based on air quality monitoring from 2006 to 2008.

“It just makes it official,” said Amy Warren, spokeswoman for the Puget Sound Clean Air Agency. “Everybody’s been seeing this coming for more than a year.”

Inclusion on the list means the Tacoma area must develop a plan to reduce pollution by 2012 and demonstrate it is meeting federal standards by 2014, said David Kircher, manager of the Clean Air Agency’s Air Resources program.

The delay in the official designations for the non-attainment areas was because of the transition at the EPA from the Bush administration to the Obama administration, Warren said.

Specifically, the designation is for “PM2.5” pollution, scientific shorthand for particulate matter that is 2.5 micrometers in diameter or smaller – ultra fine particles found in smoke and haze.

The size of airborne particles is directly linked to their potential for causing health problems. Health officials are concerned about particles 10 micrometers in diameter or smaller because they pass through the throat and nose and enter the lungs.

Once inhaled, they can affect the heart and lungs and cause serious health effects. Sources typically include fires, power plants, factories and motor vehicles. In Tacoma’s case, Warren said, the main culprits are inefficient wood stoves, fireplaces, diesel engines and local geography, which tends to trap polluted air in winter months.

Tacoma is the only city in the state on the list and one of five designated areas in the Pacific Northwest. Others in the region are parts of Fairbanks, Alaska; Franklin, Idaho; and Klamath Falls and Oakridge in Oregon.

Tacoma’s non-attainment area includes nearly all of the city (except for Point Defiance Park) and the suburbs to the south, east and west. McChord Air Force Base and Fort Lewis are not included.

In anticipation of the listing, several elements of a pollution control plan have been instituted in Tacoma. They include measures taken by the Port of Tacoma to reduce diesel exhaust, efforts by the city and Pierce County to move to less polluting vehicles, and programs intended to motivate consumers to weatherize their homes.

Rob Carson: 253-597-8693

rob.carson@thenewstribune.com