10. St. Louis-St. Charles-Farmington, Mo.-Ill.
> Year-round particle pollution rank: 10th worst
> Ozone pollution rank: 13th worst
> Adults with asthma: 221,038
> Population: 2.9 million
More than 280,000 residents in the St. Louis metro area suffered from either pediatric or adult asthma, making them especially sensitive to particle pollution. As of 2011, nearly 26 million Americans suffered from the disease, according to the ALA. The St. Louis area’s high level of pollution is partly attributable to coal-fired generation plants. Local politicians have called for stricter environmental regulations of Ameren Corporation’s Meramec plant to reduce sulfur dioxide emissions. Recently, environmental group Sierra Club sued Ameren, claiming it violated pollution levels and demanding it lower pollution at its plants. According to ALA’s Nolen, the area also had higher ozone levels due to the summer’s temperature, which was especially high last year.
9. Phoenix-Mesa-Scottsdale, Ariz.
> Year-round particle pollution rank: 9th worst
> Ozone pollution rank: 11th worst
> Adults with asthma: 278,199
> Population: 4.3 million
The average number of high particle pollution days in the Phoenix area — days in which the air is actually unhealthy for at least some residents to breathe — increased since last year. The area also ranks among the worst metro areas in the United States for ozone pollution. The cause of much of the pollution can be traced to a steadily growing population, which increases car pollution. And because of the relatively windless dry desert air, the ground-level ozone pollution becomes smog that hovers over the area rather than dissipating. Much of the area’s population is especially vulnerable to air pollution. According to ALA data, more than 370,000 Phoenix area residents have adult or pediatric asthma. Additionally, more than 187,000 suffered from COPD, a lung disease that affects 12.7 million adults, according to the ALA.
8. El Paso-Las Cruces, Texas-N.M.
> Year-round particle pollution rank: 8th worst
> Ozone pollution rank: n/a
> Adults with asthma: 54,409
> Population: 1.0 million
The quality of air in the El Paso metro area has suffered from a growing population in recent decades, as well as a heavy volume of commercial and passenger vehicles passing through the area. El Paso, which sits on the Texas-New Mexico border and is located roughly 25 miles from one of the largest cities in Mexico, Ciudad Juarez, had one of the fastest growing populations in the nation between 2000 and 2006 — and with the growing population came more cars. According to the U.S. Federal Highway Administration, the border crossing between El Paso and Juarez is a major source of international trade. El Paso was only one of five cities to see its year-round particle pollution levels increase in the past year.
7. El Centro, Calif.
> Year-round particle pollution rank: 7th worst
> Ozone pollution rank: 17th worst
> Adults with asthma: 11,084
> Population: 176,948
The El Centro metro area had an average of 16 high ozone days, and received failing grades for both ozone pollution as well as year-round particle pollution levels. More than 15,500 of the metro area’s 177,000 residents suffered from asthma, while roughly 5,700 suffered from COPD, making them especially susceptible to air pollution. The area borders Mexico — which has less stringent environmental regulations — and the far-larger city of Mexicali. The region’s dry desert air also allows smog to linger over the city.
6. Pittsburgh-New Castle-Weirton, Penn.-Ohio-W.Va.
> Year-round particle pollution rank: 6th worst
> Ozone pollution rank: 21st worst
> Adults with asthma: 214,860
> Population: 2.7 million
Once again, the Pittsburgh metro area was among the top 10 most polluted cities in America. However, the area recorded its lowest levels of both year-round and short-term particle pollution since the ALA began its annual study. Still for many residents, pollution may still be a problem. More than 268,000 residents, out of a population of 2.7 million suffered from asthma, while close to 150,000 suffered from COPD. Facilities operated by U.S. Steel, as well as the coal-powered Homer City power plant, have both been criticized for their environmental track record in the past. More recently, natural gas drilling has come under fire, and the state has toughened regulations to protect air quality.