What is it?
Tiny pollution particles in the air, small enough to be inhaled deep into the lungs and to cross from the lungs into the bloodstream. Measured in micrograms per cubic meter of air (µg/m³).
Why it matters
Long-term exposure is one of the most consistent environmental factors associated with asthma, COPD, heart disease, stroke, and reduced life expectancy.
Reference value
EPA's annual standard is 9 µg/m³ (tightened from 12 in 2024). Values below 9 are within the standard; above 9 means the area is in non-attainment.
Related health outcomes
- Asthma
- COPD
- Heart disease
- Stroke
Data source
EPA Air Quality System (AQS) · View source →