The Link Between Air Quality and Respiratory Health in Urban Centers

The United States is facing an unprecedented air quality crisis. According to the American Lung Association's 2025

, nearly half of all Americans—156 million people—now live in areas that received failing grades for air pollution. This represents a troubling increase of 25 million people compared to the previous year's report. The situation has deteriorated so dramatically that only two cities in the entire country now meet air quality standards across all three pollution measures, down from five cities just one year earlier.

The primary culprits behind this decline are ground-level ozone pollution and particulate matter. More than 125 million Americans live in areas with unhealthy ozone levels, and the problem is spreading rapidly across the central United States. Extreme heat and wildfires have accelerated the formation of ozone and trapped particles near ground level, creating dangerous conditions from Minnesota to Texas and throughout the West Coast.

Ground-level ozone, commonly known as smog, is a powerful respiratory irritant that has been compared to a sunburn of the lungs. Unlike the protective ozone layer high in the atmosphere, ground-level ozone forms when sunlight interacts with emissions from vehicles, power plants, and industrial facilities. Warmer temperatures driven by climate change make ozone formation more likely and harder to eliminate. Inhaling ozone can trigger shortness of breath, coughing, and asthma attacks, and research shows it may shorten overall life expectancy.

Particle pollution, particularly fine particulate matter known as PM2.5, poses an equally serious threat. These tiny particles measuring 2.5 microns or smaller originate from combustion sources including vehicle exhaust, power plants, fires, and certain chemical reactions in the atmosphere. Unlike larger particles that the body can filter naturally, PM2.5 penetrates deep into the lungs and even enters the bloodstream, causing long-term damage. Both Bakersfield-Delano, California and Visalia, California consistently rank among the nation's most polluted cities for both short-term and year-round particle pollution.

The health impacts of air pollution are severe and wide-ranging. Exposure to polluted air is linked to asthma, respiratory diseases, heart disease, certain cancers, adverse birth outcomes, cognitive impairments, and premature death. Children are especially vulnerable, as air pollution can trigger asthma exacerbations and increase risks for wheezing, bronchitis, and pneumonia. Prenatal exposure to air pollution has been associated with preterm birth, low birth weight, and stillbirth.

Environmental inequities amplify these health risks in vulnerable communities. People of color in the United States are more than twice as likely as white individuals to live in communities with failing air quality grades on all three pollution measures. Hispanic individuals face even more severe disparities, being nearly three times as likely as white individuals to live in areas with three failing grades. These stark inequalities mean that low-income and minority communities bear a disproportionate burden of respiratory disease, asthma hospitalizations, and premature mortality.

For people with preexisting conditions such as hypertension, diabetes, or chronic obstructive pulmonary disease, poor air quality can intensify their existing health problems. Older adults and children represent particularly vulnerable populations, and health officials specifically warn these groups to limit outdoor activities during air quality alerts.

The American Lung Association's 2025

identified the most polluted urban centers across the country. For ozone pollution, Los Angeles-Long Beach, California leads the nation, followed by Visalia, Bakersfield-Delano, and Phoenix-Mesa. Other notably polluted cities include Denver-Aurora-Greeley, Houston-Pasadena, San Diego-Chula Vista-Carlsbad, Salt Lake City-Provo-Orem, and Dallas-Fort Worth.

When measuring year-round particle pollution, Bakersfield-Delano and Visalia again top the list, joined by Fresno-Hanford-Corcoran, Eugene-Springfield, Los Angeles-Long Beach, and the Detroit-Warren-Ann Arbor region. Even coastal cities like San Jose-San Francisco-Oakland struggle with particle pollution, while industrial areas like Cleveland-Akron-Canton also rank among the nation's ten most polluted. Notably, 72.8 million Americans live in counties where neither ozone nor particle pollution levels are monitored, making it impossible to assess their true air quality situation.

During air quality alerts, individuals can take immediate steps to protect themselves. Stay indoors as much as possible and keep windows and car doors closed to prevent polluted air from entering. Check real-time air quality data using tools like airnow.gov or PurpleAir, which provide community-level information to help you make informed decisions about outdoor activities. This is especially important for people with asthma, chronic obstructive pulmonary disease, or other respiratory conditions.

Long-term solutions require reducing reliance on fossil fuels. At the individual level, this means reducing vehicle use and switching to electric or hybrid vehicles when possible, or using public transportation, biking, and walking. Many cities are implementing strategies to incentivize cleaner transportation, including converting city vehicles to electric power, creating low-emission zones, and redirecting pension investments away from fossil fuels. Ultimately, transitioning to clean energy sources represents the key strategy for reducing air pollution and protecting respiratory health in urban centers.