A new report from the Delaware Valley Regional Planning Commission says cuts to SEPTA will lead to a significant increase in vehicle emissions and result in a detrimental impact on air quality.

Regional planners say big planned cuts to SEPTA service will lead to a significant increase in vehicle emissions and result in a detrimental impact on the city's air quality.

The recent report from the Delaware Valley Regional Planning Commission (DVRPC) said that means a rise in traffic and fossil fuel combustion associated with pollutants that contribute to asthma and impact people with chronic obstructive pulmonary disease (COPD), among other illnesses.

SEPTA, the sixth-largest transportation agency in the country, plans to cut service by 20% starting Aug. 24 in the face of a $213 million budget deficit.

As a result, the DVRPC report projects an increase of nearly 8% in fine particulate matter (PM2.5), 7% in nitrogen oxides (NOx), and roughly 2% in volatile organic compounds (VOCs) in Philadelphia. It projects pollution would also rise in surrounding counties in smaller amounts.

Temple pulmonologist Eric Balaban fears the cuts will worsen multiple pollutants that are already a major concern for Philly residents.

"The fact of the matter is, Pennsylvania, Philadelphia, has struggled with our air quality," Balaban said. "The American Lung Association's 'State of the Air' report for 2025 gave the Philadelphia metro area straight failing grades for air pollution measures across the board, everything from ozone to small particulate pollution."

PM 2.5 is of particular concern. Defined as concentrations of 2.5 microns or smaller, the particles are so small -- far smaller than the width of a human hair -- that they are easily inhalable. The World Health Organization says PM2.5 is responsible for the biggest proportion of health effects from air pollution.

Locally, the biggest sources of PM2.5 are emissions from gas and diesel-powered vehicles. Power plants are also a source. The particles form when emissions react in the air.

Health effects can stem from short- or long-term exposure, and can range from aggravation of asthma and other respiratory illnesses to premature death in people with chronic heart or lung diseases. Children and seniors are most vulnerable.

The current standard set by the U.S. Environmental Protection Agency (EPA) for PM 2.5 is 9.0 micrograms per cubic meter, set during the Biden administration, which reduced it from the previous standard of 12.0.

The EPA under the Trump administration is weighing whether to revisit the higher standard as "a major obstacle to permitting" for polluting businesses.

According to Balaban, poor air quality disproportionately affects vulnerable populations.

"The air quality is especially important for my patients, and that makes it especially important to me," he said.

"The size matters here," he said. "When we talk about ultrafine particles, those particles go right past the upper airways ... and actually pass freely from the lungs into the bloodstream and get deposited to organs throughout our body."

Balaban specified two demographics he sees as particularly at risk: those with preexisting lung conditions like COPD and asthma, and socioeconomically disadvantaged people.

"Damaged lungs are vulnerable lungs," Balaban explained. "So patients who have COPD or asthma ... are more sensitive to toxic air, and they are more vulnerable to worsening disease due to air pollution."

He also highlighted the added risk for people living in "urban heat islands" -- areas of cities that can be as much as 22 degrees warmer than other areas. He said public transportation plays a critical role in mitigating climate change.

"By hamstringing our public transportation, not only are we missing an opportunity to be proactive in our greenhouse gas footprint, but we're also, of course, exacerbating the issue by going the other way and putting more vehicles on the road."

Heat gives rise to ground level ozone, also known as smog, that forms when NOx and VOCs combine. Smog is a lung irritant that's most likely to reach unhealthy levels on hot, sunny days in cities.

It is most common in densely populated areas with higher amounts of car exhaust and industrial air emissions.

Health agencies such as the Pennsylvania Department of Environmental Protection cite ozone when declaring Code Orange Air Quality Action Days during hot weather. During code orange days, the DEP cautions that children, older adults, and those with respiratory conditions should avoid being outdoors.

"Air pollution can actually cause lung diseases like asthma and lung cancer, and even more aggressive types of lung cancer than we would normally see," Balaban said.

He also noted that his patients rely on SEPTA.

"A lot of folks around here depend on the public transportation to make their appointments with me and my colleagues," Balaban noted, "and so we can try to keep them healthy and out of the hospital."