(Courtesy Environmental Integrity Project)
(NBC NEWS) -- The quality of the air we breathe has improved over the past 15 years, yet there are still over 100 million Americans breathing smog or pollution every day.
The American Lung Association's State of the Air report breaks down air quality across the country.
Overall, according to the report, the air is much cleaner than it was a decade ago, even in cities like busy Los Angeles.
The American Lung Association's analysis of air quality reports show the most polluted cities are in California, Utah, Texas and Pennsylvania. But Americans across the country are affected; the report shows four out of 10 people live in counties with unhealthy levels of smog and soot.
Infants, the elderly and people with breathing disorders like asthma are most at risk for complications. People who work or exercise outdoors can also be affected.
The risks of exposure from too much pollution can range from difficulty breathing to heart disease.
A proposed EPA standard may reduce the amount of sulfur in gasoline used by cars and some trucks, effectively removing the pollution from 33 million vehicles on the road.
To find out how your area ranks, visit www.stateoftheair.org.