Asthma and Air Quality

About 25 million Americans have asthma, including roughly 5 million children. For most of them, air quality is one of the biggest day-to-day variables in how their lungs feel. A bad-air day can mean wheezing, missed work or school, an ER visit, or worse.

Why polluted air makes asthma worse

Asthma is a chronic inflammation of the airways. Pollution adds fuel to that inflammation. Two pollutants do most of the damage: ground-level ozone and fine particulate matter (PM2.5).

Ozone irritates the airway lining within minutes. It causes the airways to constrict, increases mucus production, and amplifies the response to other triggers like pollen or cold air. PM2.5 penetrates deep into the lungs and triggers the same inflammatory cascade that an asthma attack relies on. NO2 from traffic and gas stoves, plus SO2 from industrial sources, can also set off symptoms.

What the research shows

A 2019 global burden study estimated that ambient PM2.5, ozone, and NO2 together cause millions of asthma-related ER visits every year worldwide. Children are disproportionately affected.

Short-term ozone spikes are tightly linked to same-day or next-day asthma flares. Research from the Annals of Allergy, Asthma and Immunology shows that even modest increases in daily ozone correlate with measurable drops in lung function in people with asthma. PM2.5 worsens the effect of ozone, so days with both pollutants elevated are especially risky.

Long-term exposure also matters. Kids growing up in high-pollution areas are more likely to develop asthma in the first place, not just have worse attacks.

Who is most at risk

• People with moderate to severe asthma
• Children with asthma
• Adults with asthma plus a second condition (heart disease, COPD, pregnancy)
• People who exercise outdoors with asthma
• Anyone whose asthma was recently uncontrolled or who had a recent hospitalization

What you can do

Check the AQI before you head outside. A simple rule for most people with asthma:

• AQI 0 to 50: Normal activity
• AQI 51 to 100: Sensitive groups (including most asthmatics) should watch for symptoms
• AQI 101 to 150: Reduce prolonged or heavy outdoor exertion
• AQI 151+: Move activities indoors

Keep your rescue inhaler with you on poor-air days. If you use a controller medication, take it as prescribed; do not skip doses during pollution events.

Indoors, run a HEPA air purifier in the rooms where you spend the most time. Close windows on high-AQI days. Don't smoke or vape, and don't let anyone smoke in your home or car. Run the range hood when cooking with gas, since NO2 from gas burners is linked to higher pediatric asthma rates.

If your asthma flares more than twice a week or wakes you at night, your action plan probably needs updating. Talk to your doctor or allergist about adjusting medications, especially heading into wildfire season or summer ozone season.

Sources

• Air Pollution and Asthma, Asthma and Allergy Foundation of America
• Understanding the Strong Link between Air Pollution and Asthma, American Lung Association
• Estimates of the Global Burden of Ambient PM2.5, Ozone, and NO2 on Asthma Incidence and Emergency Room Visits, PMC
• Effect of air pollution on asthma, Annals of Allergy, Asthma and Immunology
• Short-Term Effect of Ozone Exposure on Small Airway Function in Adult Asthma Patients, NIH