The American Lung Association has given Fairfield County an "F" on it's annual State of the Air report.

Fairfield County is among the 25 worst places for ozone pollution in the nation.

"Fairfield County has the worst ozone pollution east of Texas, frankly east of the Mississippi River," says Ruth Canovi, the Connecticut director of public policy for the American Lung Association.

Since the program began, it has never met the association's standards.

One of the reasons is the amount of traffic that occurs within the county.

Experts say the county's ozone pollution primarily comes from transportation and power plants.

"Transportation is responsible for 40% of our greenhouse gas emissions," says Canovi.

Pollution and smog from the West Coast also travel downwind to the tri-state area.

High temperatures are also a factor because they help pollution form easier.

"Climate change is really impacting our ability to clean up the air that we breathe, with wildfires but also just more hot days. More hot, sunny days will actually increase ozone," says Canovi.

The report specifically focuses on ozone because it is a lung irritant that's also linked to low birth weight.

However, progress has been made to reduce the county's pollution.

Fairfield County currently averages 30 less ozone alert days than it did in the mid-1990s.

Canovi says the reduction is the result of the Clean Air Act.

"Over these 25 years, that really shows the downward trends of ozone pollution in Fairfield County. And so, one of the things that we say is the Clean Air Act works," she says.