Where It Comes From
Vehicle exhaust, wood and biomass burning (including wildfires), cooking, tobacco smoke, and chemical reactions in air that form secondary organic aerosol [1][2].
How You Are Exposed
Breathing outdoor air near roads, fires, or industry; PM2.5 also enters indoors and comes from indoor sources like cooking, candles, wood stoves, and smoking [1][2][4].
Why It Matters
OC-rich PM2.5 triggers asthma, cough, reduced lung function, heart attacks and strokes, adverse pregnancy outcomes, and premature death; outdoor air pollution and PM are carcinogenic (IARC Group 1) [1][2][3].
Who Is at Risk
Children, older adults, people with heart or lung disease, pregnant people, outdoor workers, and communities near heavy traffic or wildfire smoke [1][2][4].
How to Lower Your Exposure
Check the Air Quality Index, limit strenuous outdoor activity on bad-air days, use MERV-13/HEPA filtration and kitchen exhaust, avoid smoking/wood burning, keep windows closed during smoke, and wear a well-fitted N95 when air is very smoky [2][4][5].