The Brunner Island power plant in York County is the single greatest source of bad air in Lancaster County, but levels are dropping dramatically with new air pollution equipment and a conversion to natural gas. (File photo: June 20, 2018)

Warmer, windier weather was expected to push stagnant, pollution-laden air out of Lancaster County by today, ending a two-day stretch in which poor air quality presented a health risk to sensitive groups.

The conditions were blamed on almost-windless, wintry weather, and it’s a problem that the region likely will experience again before the end of the season, according to Richard Clark, chair of Earth Sciences at Millersville University, where he teaches meteorology.

“It’s not uncommon,” he said. “It’ll happen again this winter.”

Clark shared his prediction Monday, the same day that officials at the state Department of Environmental Protection ordered a “code orange” air quality warning for parts of southern Pennsylvania, including Lancaster County.

A similar warning also was issued Sunday. The orange designation means pollution levels in the air could threaten sensitive groups — young children, elderly people and those with preexisting respiratory problems.

They were in danger of exposure to particulate pollution, which Clark described as microscopic liquids and solids suspended in air.

Sources of pollution

Like other forms of air pollution, particulates are a product of vehicle exhaust, power plant emissions and agriculture, as well as the domestic burning of trash, wood or coal, Clark said.

The suspended particles are so small, he said, that they can easily be inhaled, making their way past bodily defense systems like nose hairs and mucus that trap larger substances.

“The smallest ones can go all the way into the lungs and restrict oxygen,” he said, explaining that’s true for both humans and animals.

That’s a problem, according to Alan Peterson, a retired Lancaster County physician, who has long studied the relationship between the environment and health.

In the lungs, those particles can cause inflammation before making their way into the bloodstream and, eventually, the heart and other organs, he said.

For that reason, poor air quality presents a danger not only to those with underlying respiratory issues but also those with heart problems or a history of cardiovascular disease, Peterson said.

Infants, he said, are especially at risk, because they breathe more rapidly than adults and whose lungs are still developing.

Peterson also noted that studies during the ongoing pandemic suggest that poor air quality can exacerbate the effects of COVID-19.

The doctor offered advice for at-risk individuals on bad-air days.

“It’s probably best just to stay inside,” he said, backed by the DEP warning, which urged those groups to “limit outdoor activities” until cleaner air returns.

Weather patterns

That relief likely will have arrived by today with warmer, windier weather predicted, according to Steve Travis, a National Weather Service meteorologist. That wind, he said, was expected to push stagnant, pollutant-laden air out of the area.

The Sunday and Monday air pollution warnings were a direct result of stagnant air, he said. Mostly windless weather coupled with dense, cold air close to the snow-covered ground created ideal conditions for particulate pollution to remain in the region, largely unmoved.

“It’s not unheard of,” Travis said, explaining it’s something the region has experienced before.

In fact, a similar weather pattern in 2014 created a multi-day period of high pollution levels in Lancaster County, where there is a history of poor air quality, according to Kevin Stewart, the local environmental health director for the American Lung Association.

Taking a quick look at regional air quality reports Monday morning, Stewart said he wasn’t seeing extraordinarily high numbers in Lancaster County. However, some other parts of the state were seeing particulate pollution totals outside of clean air standards, he said. The Monday DEP warning included more than a dozen counties.

People, especially those in the at-risk groups, should regularly monitor conditions on websites like, Stewart said.

“We would like people to pay attention to air quality, particularly on days like today,” he said Monday. “This is an issue for folks, and they should be careful about their exposure to air pollution.”

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