Unhealthy Air Quality (AQI 151–200)
Everyone may begin to experience health effects. Sensitive groups may experience more serious effects.
0–50
51–100
101–150
151–200
201–300
301–500
What Does This Mean?
PM2.5 is typically 55.5–150.4 µg/m³ — 3–10× the WHO 24-hour guideline. This is a significant pollution event. The air is visibly hazy. Common during severe inversions, large wildfires, or heavy industrial areas.
Who Is Affected?
- Everyone — healthy adults may notice throat irritation, coughing, or reduced stamina
- Sensitive groups face increased risk of respiratory symptoms, asthma attacks, or cardiovascular events
- Outdoor workers are particularly exposed
What Should You Do?
- Everyone: reduce prolonged outdoor exertion
- Move exercise indoors
- Wear N95/KN95 masks outdoors (surgical masks do NOT filter PM2.5)
- Close windows and doors, run HEPA air purifiers
- Sensitive groups: avoid outdoor exertion entirely if possible
- Monitor symptoms — seek medical attention for persistent coughing, chest tightness, or shortness of breath
Key Pollutants at This Level
PM2.5 is almost always the primary driver at AQI 151+. In rare cases, ozone or SO₂ from industrial emissions can contribute.