Photograph by Peter Bohler, Redux
Read Caption

Los Angeles has long struggled with air quality.

Photograph by Peter Bohler, Redux

See the Best and Worst Places for Breathable Air in the U.S.

New rankings of air quality in cities show the cleanest air isn't always rural.  

The air Americans breathe is cleaner than ever, thanks to cleaner power plants and cleaner vehicles. That milestone is all the more impressive when considering progress has been achieved in spite of increases in population, energy use, and miles driven.

Yet nearly 40 percent of Americans—125 million people—still live where the air is unhealthy to breathe. Those findings are contained in the American Lung Association’s annual State of the Air report, released Wednesday.

This year’s survey tracks air quality measurements between 2013 and 2015 of ozone and particle pollution, short-term and year-round. Cities and counties are ranked on three separate lists for levels of those pollutants. More than 18 million people live in 12 counties with all three air pollution conditions.

Ozone, otherwise known as smog, is created by gases, including tailpipe and smokestack emissions. People at risk from inhaling ozone are children, teens, seniors age 65 and older, people who work outdoors, and people with heart and lung diseases, including asthma and lung cancer.

Particle pollution is a mixture of solid and liquid particles, one-thirtieth the diameter of a human hair, that circulate in the air. Inhaling particle pollution can increase the risk of lung cancer and cause heart attacks, strokes, emergency room visits for people with asthma, heart disease, and early death.

Both particles and ozone increase the risk of lower birth weight in newborns.

“You don’t have to have pollution day in and day out to harm you,” says Janice Nolen, an American Lung Association assistant vice president. “The classic example is the 1952 killer fog in London.”

Toxic fog, mixed with tons of poisonous soot from coal-burning fireplaces, settled over the city for five days, creating the worst air pollution disaster in British history. An estimated 4,000 people died, though some concluded that the bad air eventually caused 12,000 deaths.

Nolen says the Clean Air Act of 1970 accounts for the progress that’s been made in cleaning up America’s air. But with success has come pushback from industries that “don’t want to do more,” she says. “We’re concerned about that.” (See 46 environmental victories since the first Earth Day.)

Here are four takeaways from the Lung Association’s new annual review:

View Images

Pittsburgh's air has dramatically improved in recent years.

1. California is still air pollution king

Los Angeles maintains its rank as the city with the worst ozone pollution. The City of Angels has remained at the top of the worst pollution list for 17 out of the 18-year history of the report. Bakersfield is holding steady as the city with the worst short-term particle pollution and Visalia-Porterfield-Hanford rounds out a California trifecta in the pollution rankings by becoming the most-polluted city for year-round particle pollution for the first time this year.

California also retains its ranking with seven of the 10 most-polluted metropolitan areas and 11 of the worst 25 cities. But the pollution isn’t caused just by the millions of cars driven by the 39 million people who live in California. The state’s weather and geography complicate efforts to reduce emissions. Wildfire smoke and high inversions that trap particles behind ridges and mountains are becoming year-round conditions. After California, nine of the 25 most ozone-polluted cities are in the Southwest, where wildfires and drought are now also regular occurrences.

2. Progress in the Rust Belt and the industrial East

The eastern portion of the country, where coal-fired power plants have been cleaned up and the use of old diesel engines has declined, has seen a shift in rankings. Dirty manufacturing cities such as Pittsburgh, Pennsylvania, which had been ranked as the most polluted city for year-round particle pollution in 2008, experienced its fewest unhealthy days ever, thanks to clean-up of industrial sites. Likewise, three Tennessee cities, including Knoxville, home to the Tennessee Valley Authority power plants, are no longer on the worst-polluted lists. Knoxville once had 111 unhealthy air days, but just one for the new report.

View Images

The Church Street Marketplace in Burlington, Vt., one of six cities ranked on all three of the American Lung Association's cleanest U.S. cities lists.

3. Climate change will make it difficult to protect human health

Despite the improvements in air quality, a handful of cities reported their highest number of unhealthy days since the report began, in part because of extreme weather events. Drought prompts dust storms and wildfires, which, in turn, increase short-term particle pollution. Warmer daily temperatures make it more difficult to reduce ozone pollution. Stagnant weather patterns contributed to the extraordinarily high number of days the air contained unhealthy particulate matter. Inversions in the San Joaquin Valley in southern California and in the Wasatch Ridge in Utah worsened bad air days in both states.

4. The cleanest cities are not all rural

Six cities ranked on all three pollutant lists for cleanest cities. They had no high ozone or high particle pollution days, and were among the 25 cities with the lowest year-round particle levels. Five cities are repeaters: Burlington, Vermont, Cape Coral-Fort Myers, Florida, Elmira-Corning, New York, Honolulu, Hawaii, and Melbourne-Titusville-Palm Bay on Florida’s Space Coast. For the first time, Wilmington, North Carolina made the top clean cities list.