America’s Most Polluted Cities

There’s no doubt that great strides have been made in air pollution. Awareness, stricter legislation and improved technology have all contributed to improved air, land and water conditions. In fact, the nation’s air quality is much cleaner than it was in some of the worst-affected areas, according to a recent report by the American Lung Association. Air emissions that contribute to pollutants have fallen since 1970 thanks to the Clean Air Act.

Despite the improvements, 1 in 4 Americans live where pollution levels are often dangerous to breath. Since the ALA began studying particle pollution, almost all of the most polluted cities have consistently remained among the worst. Pittsburgh has been one of the 10 most polluted cities since 2004. The cities of Bakersfield and Merced, in California, are the most polluted cities in the U.S. this year and have been among the 25 most polluted since at least 2004. They are among many California cities, including Los Angeles, that have struggled with pollution for some time.

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The ALA’s 2013 “State of the Air” report measures cities based on low-lying ozone pollution, as well as both short- and long-term particle pollution. These particles, just 1/30th the diameter of a human hair, are capable of getting past our bodily defenses and cause physical harm, particularly to those who already suffer from pulmonary diseases, the very young and the elderly. The report measures both the total accumulated particle pollution over the course of a year, as well as the number of days that the air pollution hit unhealthily high levels. Based on the average levels of long-term pollution measured by the report between 2009 and 2011, these are the most polluted cities in the country.

10. Cincinnati-Middletown-Wilmington, Ohio-Ky.-Ind. > Year-round particle pollution rank: 10th worst > Unhealthy ozone pollution rank: 14th worst > Residents with asthma: 215,984 > Population: 2,179,965

The greater Cincinnati area is one of the most polluted areas in the country outside of California. Only 13 other metropolitan areas averaged more days with dangerously high ozone levels. However, to the city’s credit, the number of days with high ozone levels in the area fell by more than half between the 1996-1998 measurement period to the 2009-2011 one. Much of the greater Cincinnati area is in Ohio, which was the second worst state for air pollution in the nation, according to a 2012 study from the National Resources Defense Council. Cincinnati is also on the Ohio River, which had more toxic releases than any other river in 2010, according to

9. El Centro, Calif. > Year-round particle pollution rank: 9th worst > Unhealthy ozone pollution rank: 10th worst > Residents with asthma: 14,253 > Population: 177,057

In the last year, the El Centro metro area had 49 days where the ozone level was unhealthy for sensitive populations. In addition, the ALA gave the metropolitan area a failing grade for particle pollution. El Centro’s population of about 177,000 people includes many residents who suffer from conditions that can be exacerbated by pollution. Much of El Centro’s air pollution has to do with vehicle emissions, and the city has made efforts to address the problem by recently converting several city streets into pedestrian malls. Fortunately, the number high ozone days has fallen from an average of more than 80 annually in 1996-1998 to less than 20 in 2009-2011.

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8. Pittsburgh-New Castle, Penn. > Year-round particle pollution rank: 8th worst > Unhealthy ozone pollution rank: 24th worst > Residents with asthma: 224,567 > Population: 2,450,281

Since the ALA began measuring particle pollution in 2004, Pittsburgh has been among the 10 cities with the highest levels of particle pollution. In the most recent study, it was seventh worst overall for short-term particle pollution, and eighth worst for long-term pollution. Nolen explained that one of the major sources of continuing particle pollution in the area is the U.S. Steel Plant. Pittsburgh is also downwind from many coal-fired power plants in the midwest. This also has a major impact on the region’s particle pollution levels. As a major city, Nolen added, heavy traffic also contributes to high pollution levels. An estimated 28% of the region’s 2.45 million residents suffer from cardiovascular disease, with high pollution levels putting them at risk of further exacerbating their condition.

7. Visalia-Porterville, Calif. > Year-round particle pollution rank: 7th worst > Unhealthy ozone pollution rank: 2nd worst > Residents with asthma: 35,957 > Population: 449,253

The Visalia metro area registered an average of 234 days a year of ozone air quality that was considered unhealthy for sensitive populations between 2009-2011. In addition, in 19 days the ozone air quality was considered unhealthy for everyone. According to the ALA, particle pollution in Kings County, the only county in the Visalia area , has doubled in the last six years. Out of roughly 450,000 residents 36,000 have asthma, and the poor air quality may be causing them significant problems. In addition, more than 86,000 people in the area suffer from cardiovascular disease.

6. Modesto, Calif. > Year-round particle pollution rank: 6th worst > Unhealthy ozone pollution rank: 13th worst > Residents with asthma: 41,791 > Population: 518,522

Modesto is one of several cities among the nation’s worst for air pollution located within the Central Valley in California. The valley has high pollution levels due to both its unique geography and its massive agricultural industry. The Modesto Convention & Visitors Bureau reported that agriculture represented over one-third of all jobs in the area and was among the nation’s leading producers of milk, almonds and poultry. The metro area received failing grades for the number of high ozone days it had, the number of high particle pollution days, and the annual average levels of particle pollution. Additionally, while the number of high ozone days has declined in recent years, the number of days where particle pollution is especially high has risen dramatically — there were 16.2 more such days in the most recent measurement than there were in the 2000-2002 period.

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