But the trends reported in this year's report, which covers data collected by states, cities, counties, tribes and federal agencies in 2013-2015, are strikingly different for these pollutants.
California's most populous metro area, Los Angeles, continues to improve, posting its lowest number of unhealthy days for ozone pollution and lowest levels of year-round particle pollution.
One way the region can make strides in improving air quality would be to better regulate agricultural burns, create more stringent thresholds for when homeowners can burn wood in their fireplaces and place restrictions on other businesses that contribute to pollution, Dolores Weller, director of the Central Valley Air Quality Coalition, said.
For those Counties receiving an "F" for fine particle pollution, the majority of poor air quality days can be directly attributed to smoke from wildfires. Janice Nolen, assistant vice president of Policy for the American Lung Association, called the Northeast the tailpipe of the nation. Since last year's release, the number of people nationwide who were exposed to unhealthy air at some point dropped from 166 million to 125 million. Additionally, according to the Indiana Department of Environmental Management, North Dakota ranks third in the nation among all 50 states and the District of Columbia in overall air quality, based on population-weighted design values from 2013-15.
Particle pollution is a combination of both minuscule liquid and solid particles circulating in the air. It is also risky for cardiovascular harm, like heart disease and stroke and it causes lung cancer.More news: Arrest made in Sask. human smuggling case
Many cities experienced their highest number of daily particle pollution spikes since monitoring began in 2000-2002. The Bay Area ranked among the country's 10 worst regions for what is known as particle pollution. "We've had an extended drought, we've had a lot of heat waves, and those tend to increase and accelerate the formation of ozone". Likewise, three Tennessee cities, including Knoxville, home to the Tennessee Valley Authority power plants, are no longer on the worst-polluted lists. Several cities, including four among the ten most polluted, reached their lowest levels ever.
The eastern portion of the country, where coal-fired power plants have been cleaned up and the use of old diesel engines has declined, has seen a shift in rankings. Visalia-Porterville-Hanford, California was an area where levels worsened, and it ranked as the city with the worst year-round level in 2013-2015. Last year's report gave the county an "A" for having no high ozone days.
Children are at special risk from air pollution because their lungs are still growing, health experts say. However, research shows that climate change causes warmer temperatures, which makes ozone harder to clean up.
Unfortunately for most of the rest of the state, the report's findings are not so positive.
Ozone is the other air pollutant the American Lung Association studies. It was given a mark of "B" by the lung association.