A report from The American Lung Association released April 24 found Harris County has cut year-round soot levels since last year.

The report, titled "State of the Air 2013 " is described as an annual, national air quality "report card." The 2013 report—the 14th annual release—uses air pollution data compiled by the Environmental Protection Agency from 2009–2011. The data comes from official monitors for the two most widespread types of pollution: ozone (smog) and particle pollution (soot). The report gives a grade to counties and a ranking to cities and counties based on scores for ozone, year-round particle pollution and short-term particle pollution levels.

"Houston ranked as the seventh most polluted city in the nation for smog, and Harris County ranked as tenth most polluted county for smog," the report said. "Despite this, the air quality in Houston continues the long-term trend to much healthier air."

The report found Harris County's smog levels stayed about the same, resulting in a failing grade. Smog is the most widespread air pollutant, created by the reaction of sunlight on emissions from vehicles and other sources. When it is inhaled, it irritates the lungs and can cause immediate health problems, such as wheezing, coughing, asthma attacks and premature death.

While the county was able to reduce its year-round particle pollution, it received a B grade for short-term particle pollution because of too many days of unhealthy particle levels, according to Sara Dreiling, Chief Executive Officer of the American Lung Association, Plains-Gulf Region.

Despite improvements, both Harris and Montgomery counties received an overall grade of F.

"The air in Houston is certainly cleaner than when we started the 'State of the Air' report 14 years ago, but the work is not done," Dreiling said. "We must set stronger health standards for pollutants and cleanup sources of pollution in Houston to protect the health of our citizens."

From 2009 to 2011, many cities in the U.S., including Houston, made progress in year-round levels of particle pollution, Dreiling said. Emissions reductions from coal-fired power plants and the transition to cleaner diesel fuels and engines are two significant initiatives leading to an improvement of air quality nationwide.

The report found that more than 131.8 million people in the U.S. still live in counties that have unhealthy levels of either ozone or particle pollution, which equates to more than 4 in 10 people.

"Cleaning up major air pollution sources through steps like cleaner gasoline and cleaner vehicle standards will drastically cut both ozone and particle pollution," the report said. "That means more health protections for the nearly 132 million people living in counties with dangerous levels of either ozone or particle pollution."

Read more about The American Lung Association in Texas and learn about air pollution at www.stateoftheair.org.