According to the American Lung Association’s 2021 State of the Air report, ozone and year-round particle pollution improved in the Harrisburg-York-Lebanon metro area, but short-term particle pollution worsened from the previous report.

The report looks at two kinds of air pollution – ozone pollution and particle pollution — that can have negative health impacts.

Ozone is created when volatile organic compounds, like unburned fuels and solvents, and nitrogen oxides, which are released in sources like automobile exhaust, react in the presence of heat and sunlight, explains Kevin Stewart, director of environmental health for the American Lung Association. This reaction happens most often on hot, sunny, still days.

Ozone is helpful high up in the atmosphere where it protects people from the sun’s intense ultraviolet rays. However, closer to the ground, it can cause problems. It’s a respiratory irritant that causes something akin to sunburn to the lungs, it’s so irritating, says Stewart. It can cause asthma attacks, some of which are severe.

Particle pollution, on the other hand, is tiny pieces of solid (or sometimes liquid) material that enters the air, Stewart says. Soot is one of the main contributors to this type of air pollution, but it can also include materials like pesticides and metal fumes.

The particles are so minuscule that it takes dozens of them to span the diameter of a human hair, says Stewart. Because they’re so small, they can get into the deepest parts of the lungs and even cross over into the bloodstream, Stewart explains. This can cause problems for people with chronic lung disease and people with cardiovascular diseases, in whom particle pollution can cause heart attacks or strokes.

Graphic courtesy of the American Lung Association

The 2021 State of the Air report looked at data from the years 2017-2019. Data in the report shows that the Harrisburg-York-Lebanon metro area — which includes the counties of Adams, Cumberland, Dauphin, Lebanon, Perry and York — had its “best ever results for the ozone smog and for the year-round measure of fine particle pollution,” says Stewart.

Harrisburg-York-Lebanon metro area county grades for high ozone days:

CumberlandNo data available
PerryNo data available
Information from and the 2021 State of the Air report

Nearby county grades for high ozone days:

JuniataNo data available
MifflinNo data available
Information from and the 2021 State of the Air report

While the Harrisburg-York-Lebanon metro area may have done well for year-round particle pollution, achieving its best average annual level of particle pollution so far, it fared worse when it came to short-term particle pollution spikes.

Cumberland County received the worst score of the counties in the metro area and had more bad air days than the previous worst scorers in the area, which in the 2020 report were Dauphin and Lebanon counties, according to an American Lung Association press release.

Nearby Lancaster County received a failing grade for daily fine particle pollution, and it’s now listed among the 25 worst metro areas in the country for particle pollution, notes Stewart.

“It says that there’s still some problem where some days, the air pollution is hazardous for people in high-risk groups, especially…those folks with cardiovascular diseases, not to mention children [and] elderly [individuals],” says Stewart.

Harrisburg-York-Lebanon metro area county grades for daily particle pollution:

PerryNo data available
Information from and the 2021 State of the Air report

Nearby county grades for daily particle pollution:

FranklinNo data
JuniataNo data
MifflinNo data
Information from and the 2021 State of the Air report

To calculate the letter grades for each county, researchers look at how many days the air pollution levels are above Environmental Protection Agency safety standards, then divide that by the number of years included in the study to find the average number of unhealthy air days per year.

The EPA’s Air Quality Index ranks air quality based on how hazardous it is, so the American Lung Association gives more weight to days with worse air conditions when determining the average. The only way for a county to receive an A grade is if there are zero bad air days over the time period studied, explains Stewart.

Because counties must have zero bad air days in order to earn an A, a B grade may indicate that less than one day per year on average had an unhealthy level of pollution. For example, Adams and Lebanon Counties had a weighted average of just 0.7 days with high ozone levels.

“That may not sound like a lot,” Stewart says, “but if you’re a person in a high-risk group, you probably already know that one bad air day could be one bad air day too many.”

Graphic courtesy of the American Lung Association

Stewart also says that the American Lung Association believes that the EPA standards “are inadequate to protect public health with an appropriate margin of safety.” He says this means the association likely undercounts the number of bad air days people actually experience.

Stewart encourages individuals, especially those in high-risk groups, to pay attention to air pollution levels and avoid outdoor activity and exercise during bad air days. The website has current information about daily levels of air pollution.

To try to limit air pollution, individuals can take steps like driving less often and keeping vehicles properly maintained or conserving electricity use, says Stewart. They can also refrain from activities like open burning of trash that contribute to fine particle pollution.

The State of the Air report also offers advocacy advice for improving air quality, such as encouraging all localities to actively monitor air quality “because only when we measure something do we know what we’re exposed to,” Stewart says.

The 2021 report also pushes for a move toward a “cleaner energy economy, with the benefits especially directed to the populations who have been at higher risk, disproportionately exposed populations and populations that are more likely to experience problems,” says Stewart. “We know that people living in poverty, persons of color are more likely to experience problems.”

The full results of the 2021 State of the Air report can be found on the American Lung Association’s website here.