Pollutants
A plain-language guide to what's in the air. Where we have a live reading, the pollutant's current US EPA AQI is shown; otherwise the card still explains what it is and how it affects health.
PM2.5
AQI 58 · Moderate
58
Moderate
What it is
Fine inhalable particles 2.5 micrometers across or smaller — roughly one-thirtieth the width of a human hair. Most comes from combustion: vehicle exhaust, wood smoke and wildfires, power plants, and industry.
Health effects
Small enough to reach deep into the lungs and pass into the bloodstream. Short exposure can irritate the eyes, nose, and throat and worsen asthma; long-term exposure is linked to reduced lung function and heart and lung disease. Most people are unaffected at Good-to-Moderate levels. Once the air is Unhealthy for Sensitive Groups or worse, children, older adults, and people with heart or lung conditions should limit prolonged or heavy outdoor exertion.
PM10
AQI 16 · Good
16
Good
What it is
Coarse inhalable particles 10 micrometers across or smaller, including dust, pollen, mold, and ash. Common sources are road and construction dust, agriculture, and wildfire smoke.
Health effects
Larger than PM2.5 but still able to enter the lungs and irritate the airways, triggering coughing, throat irritation, and asthma or bronchitis flare-ups. Healthy people usually notice little at low levels; sensitive groups should ease back on outdoor activity as levels climb into the Unhealthy range.
Ozone
AQI 74 · Moderate
74
Moderate
What it is
Ground-level ozone isn't emitted directly — it forms when sunlight reacts with pollution from vehicles, industry, and solvents. Levels usually peak on hot, sunny afternoons.
Health effects
A strong respiratory irritant that can cause chest tightness, coughing, and shortness of breath, and can inflame the airways even in healthy people. Children, older adults, outdoor workers, and people with asthma are most sensitive. On high-ozone afternoons, move strenuous outdoor activity to the morning or evening.
NO₂
No current reading
What it is
Nitrogen dioxide, a reddish-brown gas from burning fuel — mainly cars, trucks, and power plants. It's a marker of traffic pollution and helps form both ozone and particle pollution.
Health effects
Irritates the airways and can aggravate asthma and other respiratory conditions; longer exposure can raise susceptibility to respiratory infections. People with asthma, children, and older adults are most affected. Levels are usually highest near busy roads.
SO₂
No current reading
What it is
Sulfur dioxide, a sharp-smelling gas mostly from burning sulfur-rich fossil fuels at power plants and industrial facilities, plus natural sources such as volcanoes.
Health effects
Even brief exposure can tighten the airways, causing wheezing, chest tightness, and difficulty breathing — especially during exercise. People with asthma are the most sensitive group. SO₂ also feeds particle pollution and acid rain.
CO
No current reading
What it is
Carbon monoxide, a colorless, odorless gas from incomplete combustion — vehicle exhaust, engines, and fuel-burning appliances. Outdoor levels are usually highest in heavy traffic.
Health effects
Reduces the blood's ability to carry oxygen. At typical outdoor levels it mainly affects people with heart disease, who may feel chest pain sooner during exertion; very high indoor concentrations cause headache and dizziness and can be life-threatening. Keep fuel-burning appliances well vented.
About these levels
Current AQI values are our own instantaneous US EPA sub-index for each
pollutant, taken as the worst reading across all sources so risk is never
understated. Gases other than PM2.5/PM10 appear only when a source reports
them as the current air-quality driver. Guidance follows the US EPA Air
Quality Index and is informational, not medical advice.