Today, the American Lung Association released its annual report card, State of the Air (pdf). The news for the 4,281,899 residents of the Valley of the Sun (the Phoenix Metropolitan Statistical Area) is not so good. We are now the city with the most polluted air in the United States. The study measures the average fine particle concentration in the air of each city, a key factor in asthma, bronchitis and other respiratory and heart ailments.
Where do the particles come from? Here’s what the report has to say about that:
Particle pollution is produced through two separate processes—mechanical and chemical.
Mechanical processes break down bigger bits into smaller bits with the material remaining essentially the same, only becoming smaller. Mechanical processes primarily create coarse particles.26 Dust storms, construction and demolition, mining operations, and agriculture are among the activities that produce coarse particles.
By contrast, chemical processes in the atmosphere create most of the tiniest fine and ultrafine particles. Combustion sources burn fuels and emit gases. These gases can vaporize and then condense to become a particle of the same chemical compound. Or, they can react with other gases or particles in the atmosphere to form a particle of a different chemical compound. Particles formed by this latter process come from the reaction of elemental carbon (soot), heavy metals, sulfur dioxide (SO2), nitrogen oxides (NOx) and volatile organic compounds with water and other compounds in the atmosphere. Burning fossil fuels in factories, power plants, steel mills, smelters, diesel- and gasoline-powered motor vehicles (cars and trucks) and equipment generate a large part of the raw materials for fine particles. So does burning wood in residential fireplaces and wood stoves or burning agricultural fields or forests.
One more reason to move quickly to a CLEAN energy economy. See if your city is on the list below, or go here to view the highlights and lowlights of the report.
25 U.S. Cities Most Polluted by Year-Round Particle Pollution (Annual PM2.5)
Los Angeles-Long Beach-Riverside, CA
Pittsburgh-New Castle, PA
St. Louis-St. Charles-Farmington, MO-IL
Louisville-Jefferson County-Elizabethtown-Scottsburg, KY-IN
Atlanta-Sandy Springs-Gainesville, GA-AL
Macon-Warner Robins-Fort Valley, GA
Knoxville-Sevierville-La Follette, TN
Augusta-Richmond County, GA-SC