New Jersey’s wildfires are under control. But health effects from wildfire smoke can linger.

The three New Jersey wildfires that sent smoke wafting over Philadelphia this weekend — causing air quality to plummet in some areas — are now under control, thanks in part to the first rainfall in more than a month.

But climate change means the region can expect air pollution from wildfires to become a more frequent and severe concern, says Josiah Kephart, an assistant professor of environmental and occupational health at Drexel University’s Dornsife School of Public Health.

That also puts Philly residents at a higher risk of adverse health effects from air pollution. The Inquirer spoke to Kephart about how wildfire smoke affects health and what people can do to protect themselves.

The main danger from wildfire smoke is fine particulate matter. “These are very tiny microscopic particles that are so light they float through air — you can’t see them,” Kephart said.

“But the smaller the particles are, the deeper they can get into the lungs. When they go deep into your lungs, your lungs will try to clear particles from your system, and that creates inflammation. If the particles are very small, they can pass into the bloodstream and float around your body, and that can cause trouble in other parts of the body.”

Air pollution like the kind that affected Philadelphia over the weekend — conditions were particularly bad in South Philly — impacts everyone negatively in the short term, Kephart said, but it’s especially dangerous for vulnerable populations.

“It affects all of our bodies, regardless of how healthy you are, and this is because air pollution from wildfire smoke creates inflammation throughout the body,” he said.

And there are long-term consequences for repeated exposures to air pollution, putting people at risk for respiratory and cardiac diseases and death.

Air pollution in Philadelphia and other major cities has actually been reduced over the last several decades thanks to the Clean Air Act and other environmental policies, Kephart said. “But this increase in wildfire smoke we’re experiencing is turning back those gains that we’ve worked so hard to see,” he said.

The culprit, Kephart said, is climate change. “Wildfires are happening more and more and increasing in frequency,” he said. “The carbon pollution that people are putting into the atmosphere is changing the climate and making conditions that are drier and hotter, so wildfires are more likely to happen.”

People with preexisting respiratory conditions are at a higher risk. So are kids and the elderly.

Philadelphia already has high rates of childhood asthma that are worse among Hispanic and Black children.

“It’s not because Hispanic and Black children have an inherent difference in how they respond to asthma,” James Reingold, the head of the emergency department at St. Christopher’s Hospital for Children, told The Inquirer in 2023, during another wildfire that affected air quality in Philadelphia. “It’s just a marker for where they live, what pollution they’re exposed to, and what other chronic stress they’re under.”

These health disparities are, in part, the consequences of racist housing policies that pushed many Black and Hispanic residents to neighborhoods close to highways and other pollution producers like power plants.

“If you already have preexisting conditions, if you have asthma, if you’re an older adult, if you live in a place where you’ve already been exposed to more air pollution, which has served to make your body sicker, you will be more vulnerable to health impacts from a day of bad air pollution,” Kephart said.

People who work outside are at a higher risk because they might not be able to go inside to protect themselves from the smoke during the workday.

By contrast, those who can afford indoor air purifiers can protect themselves more easily, Kephart said.

Whenever possible, people should limit physical activity outside during a wildfire smoke event and close windows and doors. Other safety steps include checking on neighbors, especially if they’re older or have other health issues, and monitoring air quality through weather apps and the federal government’s air quality website, airnow.gov.

“On a societal level, we want to reduce the amount of air pollution we’re creating in the city, and a large portion of that is through cars,” Kephart said. “Using public transit and electric vehicles are a great way to reduce air pollution.”

He urged policymakers to work to reduce greenhouse gas emissions to prevent further climate change. “Increasing wildfires is an example of the health threats that will increase because of human-caused climate change,” Kephart said.