Air quality alerts are in effect in the Philadelphia area for a second straight day, fueled by smoke from wildfires that are burning thousands of miles away.

Bill Hoffman is battling more than just a hill on his 3-mile run in Fairmount Park. He says the air is also a challenge.

Smoke from wildfires in Canada is causing air quality issues.

"If I run really hard and breathe deeply, then I might get smoke in my lungs," Hoffman said.

The Pennsylvania Department of Environmental Protection says wildfire smoke is adding extra pollution to the air with fine particulates, or microscopic pieces of ash and soot.

Dr. David Manoff, chief of pulmonary and critical care at Temple University Hospital, said the bad air can be especially dangerous for people with heart or lung disease. They might be more prone to symptoms such as shortness of breath, coughing, wheezing and chest tightness, he said.

"When that gets down into the tiny air spaces of your lungs, it is going to cause inflammation. The body is going to want to get it out of there, and then it can also cause some problems in terms of the small air spaces of the lungs functioning properly," Manoff said.

Manoff said the smoke in the air is affecting thousands of people in the Philadelphia region.

"We very definitely have fairly sizable rates of asthma and COPD. And we certainly at the Temple Lung Center see a very significant amount of interstitial lung disease," Manoff said. "Over the course of the past several weeks, we've seen an increase in people come in who are saying that spending time outside is causing problems," he added.

People who are vulnerable, including young children and older people, are advised to stay inside as much as possible.