Massachusetts' air quality has worsened over the past couple of years, according to a new report released Wednesday.
Denver has some of the highest levels of hazardous air pollution in the country, and the problem is getting worse, a new report from the American Lung Association found.
They say four in 10 Americans live in counties that have air with unhealthy levels of "particle pollution" or ozone.
The 2019 "State of the Air" report found ozone levels increased in most cities, largely because of rising temperatures.
The American Lung Association says their annual air quality "report card" tracks Americans' exposure to unhealthy levels of ozone or particle pollution, both of which can be deadly.
These moves have seemed to cause some alarm at the American Lung Association, which insists that 'the Clean Air Act must remain intact and enforced to enable the nation to continue to protect all Americans from the dangers of air pollution, ' the association said in its report.
The report said that the Fresno-Madera-Hanford area exposed the highest number of at-risk people to year-round particle pollution.
Particle pollution is the mix of solid and liquid droplets in the air, according to the US Environmental Protection Agency. That's an increase of 7.2 million people from last year's report.
In Oregon, Multnomah County earned a B grade for "high ozone days". "We have to keep cleaning up the air, and we have to deal with climate change first and foremost, especially after seeing the harm of what is happening now".
"People don't understand how risky ozone really is", said Ellen Penrod, executive director of the American Lung Association in Colorado.
"Particle pollution is made of soot or tiny particles that come from coal-fired power plants, diesel emissions, wildfires and wood-burning devices".
That means that more than 141 million people in the United States now breathe air that is contaminated with high levels of ozone and soot, day-in and day-out.
Bangor, Maine, and the Burlington-South Burlington area in Vermont were named by the association as two of the six cleanest-air cities in the country.