Asthma Capitals®: Risk Factors That Can Worsen Asthma or Influence Asthma Rates

Socioeconomic status plays a major role in the development of asthma and a person’s ability to manage it. People living below 100% of the Federal Poverty Level (FPL) are more likely to have asthma than people living at any percentage above the poverty level.¹

Numerous studies have explored and confirmed the link between poverty and poor asthma outcomes. For example, living in poverty directly affects:

• Housing quality and increased exposure to indoor asthma triggers
• Physical environment and increased exposure to outdoor asthma triggers
• Ability to pay for asthma care due to competing priorities and basic needs
• Access to quality asthma care due to suboptimal health care coverage

Many cities in our report have poverty as a top risk factor. Good asthma management can be difficult when families are worried about paying for housing, clothing, utilities, and food. The cost of care may affect the decision to seek medical care. A lack of reliable transportation and paid sick leave may influence a person’s ability to attend regular health care appointments.

These cities have the highest rates of poverty^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained the poverty rate for its respective county. The estimates range from 7.1% to 24.2%. Download image of Figure 1 table

People without insurance, or with limited coverage, face steep costs for routine office visits, emergency care, and medicines. Even people with insurance often face high deductibles and copays.

However, insurance itself can also be costly. These costs may vary depending on employment status and whether the job offers health insurance as a benefit and pays any of the costs. Other options include marketplace health insurance and government-sponsored insurance, like Medicare or Medicaid. Some states have expanded health insurance options for their residents while others have not. The states with the highest uninsured rates are states that did not expand Medicaid under the Affordable Care Act.

These cities have the highest number of uninsured residents^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained the uninsured rate for its respective county. The estimates range from 3.2% to 27.5%. Download image of Figure 2 table

Nearly half of children with asthma in the U.S. depend on Medicaid or the Children’s Health Insurance Program for coverage. Medicaid also provides coverage for millions of low-income adults, children, older adults, and people with disabilities and helps pay for the hospitals, physicians, and community health centers that deliver care in communities nationwide.

Medicaid cuts passed in the recent H.R. 1 federal bill are expected to cause millions of people to become uninsured. Changes to the ACA marketplace coverage are unfolding at the same time, creating a coverage “cliff,” in which affordable coverage can become unavailable or substantially more expensive rather than changing gradually. This will leave a larger share of people with asthma facing higher costs, thinner coverage, or no coverage at a time when consistent access to care is critical.

Effective asthma management begins with access to the right providers. Many people with asthma rely on primary care providers, who diagnose the condition, prescribe medicines, and offer follow-up management. But for many people – especially those with severe or uncontrolled asthma – specialist care can make a significant difference. Allergists and pulmonologists can provide advanced diagnostic testing, offer advanced therapies, and create individualized management plans.

Yet access to specialists varies dramatically. In rural areas, people may have to travel for hours to see a specialist. Even in urban centers, shortages of specialists serving low-income neighborhoods can leave families without nearby options. Long wait times are common, sometimes stretching weeks or months.

These cities have the fewest asthma specialists per asthma patient^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained data on specialists per 10,000 asthma patients. Download image of Figure 3 table

People managing asthma and allergies can search for specialists in their area using the Find an Allergist tool from the American College of Allergy, Asthma & Immunology (ACAAI): acaai.org/find-an-allergist

Respiratory infections (also called respiratory illnesses) are caused by viruses or bacteria that make you sick. Respiratory infections are a significant asthma trigger, and lead to more asthma flare-ups, ED visits, hospital stays, and deaths. Vaccines can help protect against some respiratory infections and reduce the risk of serious illness and death. They also can help stop the spread of respiratory infections to others. Seasonal vaccines, like those for flu and COVID-19, are available each year to help protect against the most current strains of these illnesses.

Analyses of medical claims data for asthma and flu ED visits in 2025 show the months with the most asthma ED visits (January, February, March, and December) are also the months with the most flu ED visits.

These cities have the lowest vaccination rates for flu and COVID-19 for the 2025-2026 viral season^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained the total number billed flu and COVID-19 vaccinations for the respective census-designated metropolitan statistical area, or MSA, from August 2025-June 2026 (when vaccines were available for the 2025-2026 viral season). Download image of Figure 4 table

In addition to seasonal vaccines for respiratory infections, the FDA approved a vaccine for respiratory syncytial virus (RSV) that became available in August 2023 to protect infants and babies, adults with asthma or other risk factors, and all adults over age 60. The vaccine can help prevent lower respiratory tract disease that is caused by the RSV virus.

These cities have the lowest vaccination rates for RSV to date^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained the total number billed RSV vaccinations for the respective census-designated metropolitan statistical area, or MSA, since August 2023 (when the RSV became commercially available in the United States). Download image of Figure 5 table

Pediatric asthma-related ED admissions start to rise in September and continue to spike in alignment with respiratory virus season. This pattern is associated with the return of kids going back to school in August and September, where close contact and crowded classrooms facilitate the spread of respiratory infections. The overlap of school and onset of respiratory infection season contributes to the rise in asthma attacks in the fall and winter, leading to an increase in ED visits and missed school days.

Older adults have a higher risk of death from asthma as well as respiratory infections. Older adults have weakening immune systems that make them more susceptible to serious complications.

Poor air quality can negatively affect everyone’s health. The people at highest risk from exposure are children, older adults, people with lung or heart disease, are pregnant, have lower incomes, or who live or work outside. Outdoor air pollution is a significant asthma trigger. It  causes increased rates of ED visits, hospital admissions, and missed school days related to asthma. Air pollution includes gases, smoke from fires, volcanic ash, dust particles, emissions from transportation, and other substances that can harm the lungs.

Major air pollutants include:

• Harmful gases (ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide)
• Particle pollution (also called particulate matter or soot pollution, reported by size: PM_2.5 and PM₁₀)

Ground-level ozone, a gas, is one of the most common air pollutants. Ozone contributes to what we typically experience as smog or haze. Ozone triggers asthma because it is irritating to the lungs and airways. Other gases can also trigger asthma.

Small particles in the air found in haze, smoke, and airborne dust can pass through your nose or mouth and get into your lungs. People with asthma are at greater risk from breathing in small particles. PM_2.5 pollutants are the most dangerous because they can get deep into the airways.²

Nearly half of the U.S. population lives in areas with unhealthy levels of ozone or particle pollution.³

The American Lung Association’s 2026 State of the Air Report gave 18 cities an F rating for high ozone days and particle pollution^†:

† For each city included in the 2026 Asthma Capitals report, AAFA obtained the grades for high ozone days and particle pollution for the respective county. Grades were averaged to produce an overall grade, ranging from A to F. Download image of Figure 6 table

Housing Quality and Indoor Air Pollution

Indoor air quality is just as important as outdoor air quality. We spend about 90% of our time indoors, whether at school, home, or in the workplace.⁴ Indoor air can be up to 5 times more polluted than outdoor air. Buildings can trap harmful air pollution and other asthma triggers inside. Reducing asthma triggers in homes, schools, and workplaces is an important part of asthma management.

The following can negatively affect indoor air quality:

• Allergens, such as dust mites, animal dander, cockroaches, and mold
• Scents and fragrances from candles, scent diffusers, cleaning products, and personal hygiene products
• Chemicals and volatile organic compounds (VOCs) from building materials, cleaning products, and new furniture
• Burning fuels and wood (from cooking food or heating the indoor space)
• Emissions from vehicles, gas-powered generators, and other machinery
• Outdoor air pollution that enters the building (like from wildfire smoke)
• High levels of humidity that encourage mold growth and dust mites

Due to limited data on the MSA level, AAFA’s Asthma Capitals report does not rank cities based on indoor air quality (IAQ) or housing quality as a risk factor for asthma. But this is a critical area to address in housing policy, building maintenance, school environmental policies, and workplace accommodations.

Tobacco smoke and e-cigarette aerosol can be especially harmful to people who have asthma.

About 19 out 100 adults with asthma smoke tobacco products.⁵ Children who live with smokers have more frequent asthma attacks. More than 40% of children who go to the ED for asthma live with smokers.⁶

According to the CDC, smoking is the leading cause of preventable death in the U.S.⁷ Smoking is not only harmful to the person doing the smoking but also to people nearby who inhale secondhand smoke or come into contact with thirdhand smoke. People with asthma are at greater risk of harm from tobacco products. Many chemicals, gases, and small particles in secondhand and thirdhand smoke can irritate the lungs and airways, causing additional inflammation and swelling.

Secondhand smoke – also known as environmental tobacco smoke (ETS) – refers to smoke that is released in the air when a smoker exhales, as well as smoke released from a burning cigarette, cigar, or pipe. Secondhand aerosols are also released by electronic smoking devices (e-cigarettes, hookahs, vapes).

Thirdhand smoke is residue from tobacco smoke. When a nicotine product is smoked, chemicals in the smoke stick to surfaces and dust for months after the smoke is gone. The chemicals in the residue then react to other pollutants in the air, like ozone, to create harmful particles you can easily inhale or ingest.⁸

Tobacco smoke and aerosols (including secondhand and thirdhand smoke) are unhealthy for everyone. There is no safe level of exposure to secondhand or thirdhand smoke. But many non-smokers are exposed to ETS in public places, homes, vehicles, and workplaces.

Prohibiting smoking in indoor spaces protects nonsmokers (including children) from ETS. Many state and local jurisdictions have passed laws that ban smoking in some places. These smoke-free zones may include workplaces, restaurants, hotels, parks, public housing, transit systems, and inside of cars with children as passengers.

These cities do the least to protect their residents and visitors from tobacco smoke and have fewer smoke-free laws^†, comparatively:

† For each city included in the 2026 Asthma Capitals, AAFA obtained data on whether there was a 100% smoking ban for cars with minors, non-hospitality workplaces, restaurants, bars, and multi-unit housing. Download image of Figure 7 table

That number could rise in the coming years due to climate change.¹¹ Many people have been experiencing worsening pollen allergy symptoms over the years.

Pollen allergy seasons start earlier and end later in the year than they did previously.¹² Research shows that from 1990-2018, pollen seasons start 20 days earlier and last 10 days longer.¹³ With warmer, longer seasons, allergy-causing plants can move into new areas. Ragweed, for example, is migrating northward due to climate change.

These cities have the highest pollen scores^†:

† For each city included in the 2026 Asthma Capitals, AAFA obtained daily pollen counts for each growth form (tree, grass, and weed) for the most recent calendar year (2025). Data were obtained from Pollen Sense, LLC Automated Particulate Sensors (APS). These sensors automatically image particulate matter collected from ambient air and use a neural network algorithm to identify individual pollen species and calculate daily pollen counts. Using these daily pollen counts, AAFA calculated the number of days each MSA had within the “high” or “very high” levels for each growth. Download image of Figure 8 table

1. Centers for Disease Control and Prevention. (2024). Most recent national asthma data. U.S. Department of Health and Human Services. https://www.cdc.gov/asthma/most_recent_national_asthma_data.htm
2. Centers for Disease Control and Prevention. (2024). Air pollutants. U.S. Department of Health and Human Services. https://www.cdc.gov/air-quality/pollutants/index.html
3. American Lung Association. (2025). State of the Air 2025. https://www.lung.org/getmedia/5d8035e5-4e86-4205-b408-865550860783/State-of-the-Air-2025.pdf
4. S. Environmental Protection Agency. (2024). Indoor Air Quality. https://www.epa.gov/report-environment/indoor-air-quality
5. Centers for Disease Control and Prevention. (2023). Asthma and Secondhand Smoke. U.S. Department of Health and Human Services. https://www.cdc.gov/tobacco/campaign/tips/diseases/secondhand-smoke-asthma.html
6. Patra, K. (2017). Tobacco and Children with Asthma. American Academy of Pediatrics. https://www.healthychildren.org/English/health-issues/conditions/tobacco/Pages/Tobacco-and-Children-with-Asthma.aspx
7. Centers for Disease Control and Prevention. (2024). Cigarette Smoking. U.S. Department of Health and Human Services. https://www.cdc.gov/tobacco/about/index.html
8. James, J., George, G., Cherian, M., & Rasheed, N. (2022). Thirdhand smoke composition and consequences: A narrative review. Public Health and Toxicology, 2(2), 1–6. https://doi.org/10.18332/pht/151102
9. Ng, A.E. & Boersma, P. (2023). NCHS Data Brief, no 460: Diagnosed allergic conditions in adults: United States, 2021. National Center for Health Statistics. https://dx.doi.org/10.15620/cdc:122809
10. Zablotsky, B., Black, L.I., & Akinbami, L.J. (2023). NCHS Data Brief, no 459: Diagnosed allergic conditions in children aged 0-17 years: United States, 2021. National Center for Health Statistics. https://dx.doi.org/10.15620/cdc:123250
11. Climate Central. (2021). Pollen & Allergy Season. https://www.climatecentral.org/climate-matters/pollen-allergy-season
12. Zhang, Y., Bielory, L., Mi, Z., Cai, T., Robock, A., Georgopoulos, P., & Kinney, P. L. (2022). Projected climate-driven changes in pollen emission season length and magnitude over the Northern Hemisphere. Nature Communications, 13, 1236. https://doi.org/10.1038/s41467-022-28764-0
13. Anderegg, W. R. L., Abatzoglou, J. T., et al. (2021). Anthropogenic climate change is worsening North American pollen seasons. Proceedings of the National Academy of Sciences, 118(7), e2013284118. https://doi.org/10.1073/pnas.2013284118